Dr. Alexander Phinikarides

@inproceedings{gardikisOvertheairTestsSatellitebackhauled2022,
  title = {Over-the-Air {{Tests}} of a {{Satellite-backhauled 5G SA Network}} with {{Edge Computing}} and {{Local Breakout}}},
  booktitle = {European {{Conference}} on {{Networks}} and {{Communications}} ({{EuCNC}})},
  author = {Gardikis, Georgios and Lioprasitis, Dimitris and Costicoglou, Socrates and Georgiades, Michael and Phinikarides, Alexander and Watts, Simon and Perentos, Andreas and {Fornes-Leal}, Alejandro and Palau, Carlos E.},
  year = {2022},
  month = jun,
  pages = {160--165},
  publisher = {{IEEE}},
  address = {{Grenoble, France}},
  doi = {10.1109/EuCNC/6GSummit54941.2022.9815715},
  abstract = {The use of satellite as backhaul in 5G networks is currently the most mature approach for satellite/5G integration, extending the coverage of 5G to underserved areas, beyond the reach of terrestrial backhaul infrastructures. This paper presents an actual implementation and over-the-air tests of a 5G StandAlone network, where a satellite link is used to interconnect the 5G Core with the RAN. Furthermore, local breakout is adopted to enable edge computing at the satellite edge; this is achieved by virtualizing and off-loading the 5GC User Plane Function to the edge. The performance of each configuration is evaluated with generic traffic, using the Open5GENESIS experiment automation suite, as well as in the context of an actual use case (5G smart agriculture).},
  copyright = {All rights reserved},
  isbn = {978-1-66549-871-5},
  file = {/home/alexis/Zotero/storage/HB665J4G/Gardikis et al. - 2022 - Over-the-air Tests of a Satellite-backhauled 5G SA.pdf}
}

The use of satellite as backhaul in 5G networks is currently the most mature approach for satellite/5G integration, extending the coverage of 5G to underserved areas, beyond the reach of terrestrial backhaul infrastructures. This paper presents an actual implementation and over-the-air tests of a 5G StandAlone network, where a satellite link is used to interconnect the 5G Core with the RAN. Furthermore, local breakout is adopted to enable edge computing at the satellite edge; this is achieved by virtualizing and off-loading the 5GC User Plane Function to the edge. The performance of each configuration is evaluated with generic traffic, using the Open5GENESIS experiment automation suite, as well as in the context of an actual use case (5G smart agriculture).

@inproceedings{fornes-lealDeployment5GExperiments2021,
  title = {Deployment of {{5G Experiments}} on {{Underserved Areas}} Using the {{Open5GENESIS Suite}}},
  booktitle = {International {{Conference}} on {{Smart Applications}}, {{Communications}} and {{Networking}} ({{SmartNets}})},
  author = {{Fornes-Leal}, Alejandro and {Gonzalez-Usach}, Regel and Palau, Carlos E. and Lioprasitis, Dimitris and Priovolos, Athanasios and Gardikis, Georgios and Pantazis, Spyros and Costicoglou, Socrates and Perentos, Andreas and Hadjioannou, Eleftheria and Georgiades, Michael and Phinikarides, Alexander},
  year = {2021},
  pages = {1--4},
  publisher = {{IEEE}},
  address = {{Glasgow, Scotland}},
  doi = {10.1109/SmartNets50376.2021.9555428},
  abstract = {This demo shows how the Open5GENESIS suite can be used for executing 5G experiments at rural and underserved areas, integrating technologies such as edge computing and satellite backhaul. The use case considered is a smart farming application for weed detection, realized by means of Virtualized Network Functions (VNFs) and tailored functions. The 5GENESIS experimentation methodology will be presented, showing its flexibility for orchestrating, managing and retrieving metrics of this particular experiment.},
  copyright = {All rights reserved},
  file = {/home/alexis/Zotero/storage/2WM6H6UH/Fornes-Leal et al. - 2021 - Deployment of 5G Experiments on Underserved Areas .pdf}
}

This demo shows how the Open5GENESIS suite can be used for executing 5G experiments at rural and underserved areas, integrating technologies such as edge computing and satellite backhaul. The use case considered is a smart farming application for weed detection, realized by means of Virtualized Network Functions (VNFs) and tailored functions. The 5GENESIS experimentation methodology will be presented, showing its flexibility for orchestrating, managing and retrieving metrics of this particular experiment.

@inproceedings{lioprasitisSatelliteEdgeComputing2021,
  title = {Satellite Edge Computing for {{5G}} Rural Applications},
  booktitle = {{{IEEE International Mediterranean Conference}} on {{Communications}} and {{Networking}} ({{MeditCom}})},
  author = {Lioprasitis, Dimitris and Priovolos, Athanasios and Gardikis, Georgios and Pantazis, Spyros and Costicoglou, Socrates and Perentos, Andreas and Hadjioannou, Eleftheria and Georgiades, Michael and Phinikarides, Alexander and Fornes, Alejandro and {Gonzalez-Usach}, Regel and Palau, Carlos E. and Esteve, Manuel},
  year = {2021},
  address = {{Athens, Greece}},
  abstract = {This demo shows the value of edge computing and local break-out in rural 5G -and beyond- deployments, where satellite is used as backhaul. It also demonstrates the use of the Open5GENESIS suite for experiment automation and results analysis.},
  copyright = {All rights reserved},
  langid = {english},
  file = {/home/alexis/Zotero/storage/C2FDGI76/Lioprasitis et al. - 2021 - Satellite edge computing for 5G rural applications.pdf}
}

This demo shows the value of edge computing and local break-out in rural 5G -and beyond- deployments, where satellite is used as backhaul. It also demonstrates the use of the Open5GENESIS suite for experiment automation and results analysis.

@inproceedings{gardikis5GENESISTestingFacility2019,
  title = {The {{5GENESIS}} Testing Facility as an Enabler for Integrated Satellite/Terrestrial {{5G}} Experimentation},
  booktitle = {{{IEEE Wireless Communications}} and {{Networking Conference Workshop}} ({{WCNCW}})},
  author = {Gardikis, Georgios and Papadakis, Nikos and Perentos, Andreas and {Marios Fotiou} and Phinikarides, Alexander and Georgiades, Michael and Ottavj, Luc and Diarra, Mamoutou and Masson, Thierry and Morgado, Antonio Jorge and Mumtaz, Shahid and de Puga, Jara Su{\'a}rez and Palau, Carlos E. and Koumaras, Harilaos and Kourtis, Michail Alexandros and Skiadas, Charalampos},
  year = {2019},
  pages = {1--6},
  publisher = {{IEEE}},
  address = {{Marrakech, Morocco}},
  doi = {10.1109/WCNCW.2019.8902802},
  abstract = {Satellite/terrestrial integration in the context of 5G is a very promising aspect, as it combines the unrivaled performance of 5G with the unprecedented benefits of satellite communications, such as ubiquitous broadband coverage and inherent multicast capabilities. This paper presents the design and implementation of an end-to-end experimental testbed for integrated satellite/terrestrial 5G services, developed in the frame of the EU 5GENESIS project. The testbed encompasses all the components of the 5G network and it is suitable for wide-area field trials over several use cases corresponding to the needs of vertical industries.},
  copyright = {All rights reserved},
  keywords = {5G,satcom,satellite-terrestrial integration},
  file = {/home/alexis/Zotero/storage/WJIAZHPB/Gardikis et al. - 2019 - The 5GENESIS testing facility as an enabler for in.pdf}
}

Satellite/terrestrial integration in the context of 5G is a very promising aspect, as it combines the unrivaled performance of 5G with the unprecedented benefits of satellite communications, such as ubiquitous broadband coverage and inherent multicast capabilities. This paper presents the design and implementation of an end-to-end experimental testbed for integrated satellite/terrestrial 5G services, developed in the frame of the EU 5GENESIS project. The testbed encompasses all the components of the 5G network and it is suitable for wide-area field trials over several use cases corresponding to the needs of vertical industries.

@inproceedings{koumaras5GExperimentationFacility2019,
  title = {{{5G Experimentation Facility Supporting Satellite-Terrestrial Integration}}: {{The 5GENESIS}} Approach},
  booktitle = {European {{Conference}} on {{Networks}} and {{Communications}} ({{EuCNC}})},
  author = {Koumaras, Harilaos and Anagnostopoulos, Themis and Kourtis, Michail-Alexandros and Perentos, Andreas and Fotiou, Marios and Frascolla, Valerio and Gardikis, Georgios and Papadakis, Nikos and Phinikarides, Alexander and Georgiades, Michael and Tsolkas, Dimitris},
  year = {2019},
  address = {{Valencia, Spain}},
  abstract = {This paper describes the pathway towards the realisation of a 5G Facility that will allow Satellite/terrestrial integration with scope the validation of the unprecedented benefits, such as ubiquitous broadband coverage and inherent multicast capabilities. The paper reflects the approach that the 5GENESIS project adopts in this direction for the Facility realization, including the design of a common implementation blueprint that will be instantiated across the five 5GENESIS Platforms distributed across Europe. Special emphasis is put on the design and implementation of the Limassol platform, which builds on integrated satellite/terrestrial 5G services. The platform encompasses all the necessary components of the 5G network and it is suitable for field trials over satellite-terrestrial use cases.},
  copyright = {All rights reserved},
  file = {/home/alexis/Zotero/storage/IDT93I6R/Koumaras et al. - 2019 - 5G Experimentation Facility Supporting Satellite-T.pdf}
}

This paper describes the pathway towards the realisation of a 5G Facility that will allow Satellite/terrestrial integration with scope the validation of the unprecedented benefits, such as ubiquitous broadband coverage and inherent multicast capabilities. The paper reflects the approach that the 5GENESIS project adopts in this direction for the Facility realization, including the design of a common implementation blueprint that will be instantiated across the five 5GENESIS Platforms distributed across Europe. Special emphasis is put on the design and implementation of the Limassol platform, which builds on integrated satellite/terrestrial 5G services. The platform encompasses all the necessary components of the 5G network and it is suitable for field trials over satellite-terrestrial use cases.

@article{belluardoAreSpectroradiometersUsed2018,
  title = {Are the Spectroradiometers Used by the {{PV}} Community Ready to Accurately Measure the Classification of Solar Simulators in a Broader Wavelength Range?},
  author = {Belluardo, Giorgio and Galleano, Roberto and Zaaiman, Willem and Pravettoni, Mauro and Halwachs, Martin and Fucci, Raffaele and Drobisch, Alexander and Friederichs, Matthias and Haverkamp, Erik and Phinikarides, Alexander and Friesen, Gabi},
  year = {2018},
  month = oct,
  journal = {Solar Energy},
  volume = {173},
  pages = {558--565},
  issn = {0038-092X},
  doi = {10.1016/j.solener.2018.07.093},
  abstract = {Latest trends in the photovoltaic sector see the use of innovative photovoltaic technologies with extended spectral responsivity ranging from 300 to 1200\,nm for non-concentrating terrestrial applications, and to 1800\,nm for concentrating PV and space applications. As a consequence, an update of the IEC 60904-9 standard is ongoing with a definition of new spectral ranges for the assessment of the spectral match. This poses new challenges to laboratories and research centers on whether or not they still are able to accurately measure the spectral mismatch of their sun simulator in the newly-defined spectral regions. Prior to that, there is a need to understand if the commercially available spectroradiometers are ready to extend their measurement range as prescribed by the forthcoming new standard. This paper analyses two options for an extension of the spectrum characterisation of solar simulators to 300\textendash 1200\,nm and compares them in terms of spectral match of global normal irradiance (GNI) spectra acquired under natural sunlight by eight spectroradiometers during the 6th European Spectroradiometer Intercomparison. The acquired spectra are also compared in terms of an index of consistency of the spread of the measured spectra with the estimated measurement uncertainty, hereafter named as performance statisticsEn. Results show that all investigated laboratories assure the equivalence of the spectral match classification well below the 25\% limit corresponding to class-A simulators. When considering the more stringent class-A+ corresponding to a 12.5\% limit, one of the two considered options that rearranges the 300\textendash 1200\,nm spectral range into 6 bands appears to still assure the equivalence of the class A+ limits among considered instruments. The En performance index analysis highlights some inconsistencies with the estimated measurement uncertainty or instrument drifts from the expected performance, and the need of further improvements in calibration, set up and measurement procedures.},
  copyright = {All rights reserved},
  keywords = {En performance statistics,IEC60904-9,Intercomparison,Solar simulator classification,Spectral match,Spectroradiometer},
  file = {/home/alexis/Zotero/storage/UV8WF6IJ/Belluardo et al. - 2018 - Are the spectroradiometers used by the PV communit.pdf}
}

Latest trends in the photovoltaic sector see the use of innovative photovoltaic technologies with extended spectral responsivity ranging from 300 to 1200\,nm for non-concentrating terrestrial applications, and to 1800\,nm for concentrating PV and space applications. As a consequence, an update of the IEC 60904-9 standard is ongoing with a definition of new spectral ranges for the assessment of the spectral match. This poses new challenges to laboratories and research centers on whether or not they still are able to accurately measure the spectral mismatch of their sun simulator in the newly-defined spectral regions. Prior to that, there is a need to understand if the commercially available spectroradiometers are ready to extend their measurement range as prescribed by the forthcoming new standard. This paper analyses two options for an extension of the spectrum characterisation of solar simulators to 300– 1200\,nm and compares them in terms of spectral match of global normal irradiance (GNI) spectra acquired under natural sunlight by eight spectroradiometers during the 6th European Spectroradiometer Intercomparison. The acquired spectra are also compared in terms of an index of consistency of the spread of the measured spectra with the estimated measurement uncertainty, hereafter named as performance statisticsEn. Results show that all investigated laboratories assure the equivalence of the spectral match classification well below the 25% limit corresponding to class-A simulators. When considering the more stringent class-A+ corresponding to a 12.5% limit, one of the two considered options that rearranges the 300– 1200\,nm spectral range into 6 bands appears to still assure the equivalence of the class A+ limits among considered instruments. The En performance index analysis highlights some inconsistencies with the estimated measurement uncertainty or instrument drifts from the expected performance, and the need of further improvements in calibration, set up and measurement procedures.

@article{doumanisImprovingVideoQoE2018,
  title = {Improving Video {{QoE}} with {{IP}} over {{ICN}}},
  author = {Doumanis, Ioannis and Phinikarides, Alexander and Xylomenos, George and Porter, Stuart C. M. and Georgiades, Michael},
  year = {2018},
  journal = {International Journal of Network Management},
  issn = {1099-1190},
  doi = {10.1002/nem.2057},
  abstract = {Information-centric networking (ICN) has long been advocating for radical changes to the Internet, but the upgrade challenges that these entail have hindered its adoption. To break this loop, the POINT project proposed a hybrid, IP-over-ICN, architecture: IP networks are preserved at the edge, connected to each other over an ICN core. This exploits the key benefits of ICN, enabling individual network operators to improve the performance of their IP-based services, without changing the rest of the Internet. This paper first provides an overview of POINT and outlines how it can improve upon IP in terms of performance and resilience. It then describes a trial of the POINT prototype in a production network, where real users operated actual IP-based applications. As part of the trial, we carried out experiments to evaluate the quality of experience (QoE) for video services offered via either HLS or IPTV, using either IP or POINT as a substrate. The results from the trial verify that the IP-over-ICN approach of POINT offers enhanced QoE to the users of these video services, compared with traditional IP, especially under exceptional network conditions.},
  copyright = {\textcopyright{} 2018 John Wiley \& Sons, Ltd.},
  langid = {english},
  file = {/home/alexis/Zotero/storage/BRHWIYLN/Doumanis et al. - 2018 - Improving video QoE with IP over ICN.pdf}
}

Information-centric networking (ICN) has long been advocating for radical changes to the Internet, but the upgrade challenges that these entail have hindered its adoption. To break this loop, the POINT project proposed a hybrid, IP-over-ICN, architecture: IP networks are preserved at the edge, connected to each other over an ICN core. This exploits the key benefits of ICN, enabling individual network operators to improve the performance of their IP-based services, without changing the rest of the Internet. This paper first provides an overview of POINT and outlines how it can improve upon IP in terms of performance and resilience. It then describes a trial of the POINT prototype in a production network, where real users operated actual IP-based applications. As part of the trial, we carried out experiments to evaluate the quality of experience (QoE) for video services offered via either HLS or IPTV, using either IP or POINT as a substrate. The results from the trial verify that the IP-over-ICN approach of POINT offers enhanced QoE to the users of these video services, compared with traditional IP, especially under exceptional network conditions.

@inproceedings{halwachsImprovementAccuracyPrecision2018,
  title = {Improvement of {{Accuracy}} and {{Precision}} of {{Spectral Irradiance Measurements}} in {{Annual Spectroradiometer Intercomparison}}},
  booktitle = {35th {{EU-PVSEC}}},
  author = {Halwachs, Martin and Rennhofer, Marcus and Galleano, Roberto and Zaaiman, Willem and Pravettoni, Mauro and Theristis, Marios and Phinikarides, Alexander and Riedel, Nicholas and Thorseth, Anders and Po, M and Hoogendijk, K and Haverkamp, Erik J and Minuto, Alessandro and Tatsiankou, V and Rold{\'a}n, Ruben and Marzoli, Matteo and Cole, Ian R and {Alonso-{\'A}lvarez}, D and Ferretti, Nicoletta and Drobisch, Alexander and Belluardo, Giorgio},
  year = {2018},
  url = {https://bia.unibz.it/handle/10863/9694},
  abstract = {Energy yield measurement and radiation yield determination in the field of photovoltaics (PV) are subject to fast development regarding estimation uncertainties and error in prediction [1]. Both are determined mainly by constraints given by equipment development, calibration schemes and operation routines. Further, an increasing range of PV technologies is available on the market showing rather different spectral responsivities. These require precise PV device calibrations, either outdoor or indoor, with accurate measurement of the light-source. Under these boundary conditions accurate spectrally resolved solar irradiance measurements are gaining higher importance compared to recent years. Finally also PV energy yield estimations (predictions) may benefit from more accurate information on the solar spectrum. The International Spectroradiometer and Broadband intercomparison (ISRC) is evaluating measurement devices, measurement routine and equivalence in measurement results. Last year edition involved 9 scientific institutions and 5 commercial partners of 8 countries, testingmeasurement capabilities and best practices in spectrally resolved solar irradiance between 300 nm and 1700 nm. This work compares results and best practice approaches during the recent years of intercomparison. Capability of precision improvements in measurement as well as deviation in measurement approaches, instruments and institutes are highlighted. The analysis aims to conclude on effects of harmonization efforts, spreading of best-practice.},
  copyright = {All rights reserved},
  file = {/home/alexis/Zotero/storage/4H4HNZT5/Halwachs et al. - 2018 - Improvement of Accuracy and Precision of Spectral .pdf}
}

Energy yield measurement and radiation yield determination in the field of photovoltaics (PV) are subject to fast development regarding estimation uncertainties and error in prediction [1]. Both are determined mainly by constraints given by equipment development, calibration schemes and operation routines. Further, an increasing range of PV technologies is available on the market showing rather different spectral responsivities. These require precise PV device calibrations, either outdoor or indoor, with accurate measurement of the light-source. Under these boundary conditions accurate spectrally resolved solar irradiance measurements are gaining higher importance compared to recent years. Finally also PV energy yield estimations (predictions) may benefit from more accurate information on the solar spectrum. The International Spectroradiometer and Broadband intercomparison (ISRC) is evaluating measurement devices, measurement routine and equivalence in measurement results. Last year edition involved 9 scientific institutions and 5 commercial partners of 8 countries, testingmeasurement capabilities and best practices in spectrally resolved solar irradiance between 300 nm and 1700 nm. This work compares results and best practice approaches during the recent years of intercomparison. Capability of precision improvements in measurement as well as deviation in measurement approaches, instruments and institutes are highlighted. The analysis aims to conclude on effects of harmonization efforts, spreading of best-practice.

@inproceedings{pravettoniSpectroradiometryPVHow2018,
  title = {Spectroradiometry in {{PV}}: How Inter-Laboratory Comparison May Improve Measurement Accuracy},
  booktitle = {7th {{IEEE World Conference}} on {{Photovoltaic Energy Conversion}} ({{WCPEC}})},
  author = {Pravettoni, Mauro and Galleano, Roberto and Zaaiman, Willem and Alvarez, Diego Alonso and Belluardo, Giorgio and Betts, Tom R and Bogeat, Jose Antonio and Cole, Ian R and Drobisch, Alexander and Ferretti, Nicoletta and Friedrich, Dirk and Fucci, Raffaele and G{\'o}mez, Trinidad J and Graditi, Giorgio and Halwachs, Martin and Haverkamp, Erik and Minuto, Alessandro and Phinikarides, Alexander and Plag, Fabian and Rennhofer, Marcus and Molinero, Ruben Roldan and Riedel, Nicholas and Theristis, Marios and Thorseth, Anders and Tim{\`o}, Gianluca and Vilaplana, Jose Manuel},
  year = {2018},
  pages = {2584--2589},
  doi = {10.1109/PVSC.2018.8547975},
  abstract = {Spectroradiometry is a key metrological topic for accurate testing of photovoltaic (PV) devices, particularly relevant both for indoor testing on solar simulators and for outdoor testing. The relevance of accurate measurements of solar spectral irradiance has led the most renowned European solar PV test centres to take part to a series of International Spetroradiometer Intercomparisons that has taken place every year so far since 2011 in various localities in the Mediterranean Basin. This paper revisits the performance of participant laboratories and highlights the importance of inter-laboratory comparisons, showing the possible improvements in measurement reproducibility.},
  copyright = {All rights reserved},
  langid = {english},
  file = {/home/alexis/Zotero/storage/Q7C655WK/Pravettoni et al. - 2018 - Spectroradiometry in PV how inter-laboratory comp.pdf}
}

Spectroradiometry is a key metrological topic for accurate testing of photovoltaic (PV) devices, particularly relevant both for indoor testing on solar simulators and for outdoor testing. The relevance of accurate measurements of solar spectral irradiance has led the most renowned European solar PV test centres to take part to a series of International Spetroradiometer Intercomparisons that has taken place every year so far since 2011 in various localities in the Mediterranean Basin. This paper revisits the performance of participant laboratories and highlights the importance of inter-laboratory comparisons, showing the possible improvements in measurement reproducibility.

@inproceedings{xylomenosIPICNGoes2018,
  title = {{{IP Over ICN Goes Live}}},
  booktitle = {European {{Conference}} on {{Networks}} and {{Communications}} ({{EuCNC}})},
  author = {Xylomenos, G. and Thomas, Y. and Vasilakos, X. and Georgiades, M. and Phinikarides, Alexander and Doumanis, I. and Porter, S. and Trossen, D. and Robitzsch, S. and Reed, M. J. and {Al-Naday}, M. and Petropoulos, G. and Katsaros, K. and Xezonaki, M. and Riihijarvi, J.},
  year = {2018},
  month = jun,
  pages = {319--323},
  doi = {10.1109/EuCNC.2018.8442635},
  abstract = {Information-centric networking (ICN) has long been advocating for radical changes to the IP-based Internet. However, the upgrade challenges that this entails have hindered ICN adoption. To break this loop, the POINT project proposed a hybrid, IP-over-ICN, architecture: IP networks are preserved at the edge, connected to each other over an ICN core. This exploits the key benefits of ICN, enabling individual network operators to improve the performance of their IP-based services, without changing the rest of the Internet. We provide an overview of POINT and outline how it improves upon IP in terms of performance and resilience. Our focus is on the successful trial of the POINT prototype in a production network, where real users operated actual IP-based applications.},
  copyright = {All rights reserved},
  keywords = {Computer architecture,HLS,ICN,IP networks,IPTV,Network topology,POINT,Servers,Streaming media,Topology,Trials},
  file = {/home/alexis/Zotero/storage/AGDI2SF5/Xylomenos et al. - 2018 - IP Over ICN Goes Live.pdf}
}

Information-centric networking (ICN) has long been advocating for radical changes to the IP-based Internet. However, the upgrade challenges that this entails have hindered ICN adoption. To break this loop, the POINT project proposed a hybrid, IP-over-ICN, architecture: IP networks are preserved at the edge, connected to each other over an ICN core. This exploits the key benefits of ICN, enabling individual network operators to improve the performance of their IP-based services, without changing the rest of the Internet. We provide an overview of POINT and outline how it improves upon IP in terms of performance and resilience. Our focus is on the successful trial of the POINT prototype in a production network, where real users operated actual IP-based applications.

@inproceedings{xylomenosIPTVICN2018,
  title = {{{IPTV Over ICN}}},
  booktitle = {23rd {{Packet Video Workshop}}},
  author = {Xylomenos, George and Phinikarides, Alexander and Doumanis, Ioannis and Vasilakos, Xenofon and Thomas, Yannis and Trossen, Dirk and Georgiades, Michael and Porter, Stuart},
  year = {2018},
  pages = {66--71},
  publisher = {{ACM}},
  address = {{New York, NY, USA}},
  doi = {10.1145/3210424.3210435},
  abstract = {The efficient provision of IPTV services requires support for IP multicasting and IGMP snooping, limiting such services to single operator networks. Information-Centric Networking (ICN), with its native support for multicast seems ideal for such services, but it requires operators and users to overhaul their networks and applications. The POINT project has proposed a hybrid, IP-over-ICN, architecture, preserving IP devices and applications at the edge, but interconnecting them via an SDN-based ICN core. This allows individual operators to exploit the benefits of ICN, without expecting the rest of the Internet to change. In this paper, we first outline the POINT approach and show how it can handle multicast-based IPTV services in a more efficient and resilient manner than IP. We then describe a successful trial of the POINT prototype in a production network, where real users tested actual IPTV services over both IP and POINT under regular and exceptional conditions. Results from the trial show that the POINT prototype matched or improved upon the services offered via plain IP.},
  copyright = {All rights reserved},
  isbn = {978-1-4503-5773-9},
  keywords = {ICN,IPTV,POINT,Trials},
  file = {/home/alexis/Zotero/storage/A86TVPQY/Xylomenos et al. - 2018 - IPTV Over ICN.pdf}
}

The efficient provision of IPTV services requires support for IP multicasting and IGMP snooping, limiting such services to single operator networks. Information-Centric Networking (ICN), with its native support for multicast seems ideal for such services, but it requires operators and users to overhaul their networks and applications. The POINT project has proposed a hybrid, IP-over-ICN, architecture, preserving IP devices and applications at the edge, but interconnecting them via an SDN-based ICN core. This allows individual operators to exploit the benefits of ICN, without expecting the rest of the Internet to change. In this paper, we first outline the POINT approach and show how it can handle multicast-based IPTV services in a more efficient and resilient manner than IP. We then describe a successful trial of the POINT prototype in a production network, where real users tested actual IPTV services over both IP and POINT under regular and exceptional conditions. Results from the trial show that the POINT prototype matched or improved upon the services offered via plain IP.

@inproceedings{belluardoExtendingSpectrumCharacterization2017,
  title = {Extending the Spectrum Characterization of Solar Simulator from 300nm to 1200nm: {{Challenges}} on Spectral Measurements in the {{UV}} and {{NIR}}},
  booktitle = {33rd {{EU-PVSEC}}},
  author = {Belluardo, Giorgio and Galleano, Roberto and Zaaiman, Willem and Pravettoni, Mauro and Halwachs, Martin and Fucci, Rafaelle and Drobisch, Alexander and Friederichs, M. and Haverkamp, Erik J and Phinikarides, Alexander and Friesen, Gabi},
  year = {2017},
  pages = {1359--1363},
  doi = {10.4229/EUPVSEC20172017-5BO.6.3},
  abstract = {Innovative photovoltaic technologies with spectral sensitivity exceeding the 400 to 1100 nm limits (as currently defined by the international standard IEC 60904-9) are nowadays available on the market. This poses new challenges in the correct measurement of the spectral content of solar simulators and natural sunlight in those wavelength bands that lie outside these limits. This study proposes an extension of the IEC 60904-9 bandwidth by adding two bands in the UV (300-400 nm) and NIR (1100-1200 nm) regions. This new proposed extension is analysed in terms of spectral match, using spectral measurements of Global Normal Irradiance (GNI) acquired during the 6th European Spectroradiometer Intercomparison by eight independent laboratories. A laboratory is selected to provide reference spectra, and the spectral match of the other ones is calculated, both on a single-measurement level and on a daily average level. The intra-day and inter-day variations are evaluated as well. Results show that all investigated laboratories are capable to assure a spectral match well below the {$\pm$}25\% limit corresponding to class-A simulators. When the more stringent, informal class-A+ corresponding to the {$\pm$}12.5\% limit is considered, four out of seven laboratories are still compliant with it.},
  copyright = {All rights reserved},
  isbn = {3-936338-47-7},
  file = {/home/alexis/Zotero/storage/WLIT57AZ/Belluardo et al. - 2017 - Extending the spectrum characterization of solar s.pdf}
}

Innovative photovoltaic technologies with spectral sensitivity exceeding the 400 to 1100 nm limits (as currently defined by the international standard IEC 60904-9) are nowadays available on the market. This poses new challenges in the correct measurement of the spectral content of solar simulators and natural sunlight in those wavelength bands that lie outside these limits. This study proposes an extension of the IEC 60904-9 bandwidth by adding two bands in the UV (300-400 nm) and NIR (1100-1200 nm) regions. This new proposed extension is analysed in terms of spectral match, using spectral measurements of Global Normal Irradiance (GNI) acquired during the 6th European Spectroradiometer Intercomparison by eight independent laboratories. A laboratory is selected to provide reference spectra, and the spectral match of the other ones is calculated, both on a single-measurement level and on a daily average level. The intra-day and inter-day variations are evaluated as well. Results show that all investigated laboratories are capable to assure a spectral match well below the $±$25% limit corresponding to class-A simulators. When the more stringent, informal class-A+ corresponding to the $±$12.5% limit is considered, four out of seven laboratories are still compliant with it.

@inproceedings{liveraAdvancedFailureDetection2017,
  title = {Advanced {{Failure Detection Algorithms}} and {{Performance Decision Classification}} for {{Grid-Connected PV Systems}}},
  booktitle = {33rd {{EU-PVSEC}}},
  author = {Livera, A. and Phinikarides, Alexander and Makrides, G. and Sutterlueti, J. and Georghiou, G. E.},
  year = {2017},
  month = nov,
  pages = {2358--2363},
  doi = {10.4229/EUPVSEC20172017-6BV.2.13},
  abstract = {PV System Performance and Integration, Design and Operation of PV Systems, Advanced Failure Detection Algorithms and Performance Decision Classification for Grid-Connected PV Systems},
  copyright = {All rights reserved},
  langid = {english},
  file = {/home/alexis/Zotero/storage/UMGRVG9U/Livera et al. - 2017 - Advanced Failure Detection Algorithms and Performa.pdf}
}

PV System Performance and Integration, Design and Operation of PV Systems, Advanced Failure Detection Algorithms and Performance Decision Classification for Grid-Connected PV Systems

@inproceedings{liveraImpactMissingData2017,
  title = {Impact of {{Missing Data}} on the {{Estimation}} of {{Photovoltaic System Degradation Rate}}},
  booktitle = {44th {{IEEE PVSC}}},
  author = {Livera, Andreas and Phinikarides, Alexander and Makrides, George and Georghiou, George E.},
  year = {2017},
  pages = {1954--1958},
  doi = {10.1109/PVSC.2017.8366442},
  abstract = {In this paper, the impact of missing data and the robustness of commonly used statistical techniques to calculate the annual degradation rate of crystalline-Silicon (c-Si) photovoltaic (PV) systems was analyzed. In addition, the performance of different imputation techniques was assessed in order to develop an optimal methodology for treating missing data for degradation rate estimation studies. The results obtained clearly demonstrate that the application of the different statistical methods to estimate the annual degradation rate is sensitive to the amount of missing data, since all the statistical methods underestimated the degradation rate consistently with the increasing level of missing data. In addition, the application of the Seasonal Decomposition (Seas) technique yielded robust annual degradation rate estimates since for a level of 40 \% of missing data, the absolute percentage error (APE) of the annual degradation rate estimated with all statistical techniques, was less than 7.5 \%.  Finally, Classical Seasonal Decomposition (CSD) was shown to be the most robust technique for estimating the degradation rate when imputation was applied, while Autoregressive Integrated Moving Average (ARIMA) was the most successful technique in providing robust degradation rate estimates when not applying any imputation.},
  copyright = {All rights reserved},
  file = {/home/alexis/Zotero/storage/6748IMCH/Livera et al. - 2017 - Impact of Missing Data on the Estimation of Photov.pdf;/home/alexis/Zotero/storage/M8M5Z7DM/Livera et al. - 2017 - Impact of Missing Data on the Estimation of Photov.pdf}
}

In this paper, the impact of missing data and the robustness of commonly used statistical techniques to calculate the annual degradation rate of crystalline-Silicon (c-Si) photovoltaic (PV) systems was analyzed. In addition, the performance of different imputation techniques was assessed in order to develop an optimal methodology for treating missing data for degradation rate estimation studies. The results obtained clearly demonstrate that the application of the different statistical methods to estimate the annual degradation rate is sensitive to the amount of missing data, since all the statistical methods underestimated the degradation rate consistently with the increasing level of missing data. In addition, the application of the Seasonal Decomposition (Seas) technique yielded robust annual degradation rate estimates since for a level of 40 % of missing data, the absolute percentage error (APE) of the annual degradation rate estimated with all statistical techniques, was less than 7.5 %. Finally, Classical Seasonal Decomposition (CSD) was shown to be the most robust technique for estimating the degradation rate when imputation was applied, while Autoregressive Integrated Moving Average (ARIMA) was the most successful technique in providing robust degradation rate estimates when not applying any imputation.

@phdthesis{phinikaridesDegradationRateEstimation2017,
  title = {Degradation {{Rate Estimation}} in {{Photovoltaics}}},
  author = {Phinikarides, Alexander},
  year = {2017},
  month = feb,
  address = {{Nicosia, Cyprus}},
  abstract = {Recent advances in photovoltaic (PV) module manufacturing have resulted in the production of highly efficient cells and modules and the significant reduction of the levelized cost of electricity (LCOE) due to the increased demand for the technology. Two key factors that will increase the demand and reduce the LCOE even further are: 1) improving operations and maintenance (O\&M) to ensure the optimal operation of deployed PV plants, and 2) accurately estimating the well-known effect of gradual performance degradation and guaranteeing their lifetime energy yield. Both of these key factors require active monitoring and supervision of the deployed PV plants, analysis of field measurement data for estimation of the long-term degradation rate, RD with statistical confidence and comparison with the warranty. This analysis will in turn enable the planning of actions to mitigate the causes of low performance and minimize the amount of energy lost. The accurate estimation of the RD for a deployed PV plant will also enable more accurate and precise lifetime energy yield forecasting and stricter performance guarantees, further reducing investment risk and increasing confidence in the technology. This work deals with developing a generalized data analysis methodology based on statistical principles, for estimating the energy degradation rate, using field measurement data from eleven different grid-connected PV plants operating side-by-side since June 2006 at the PV Technology test site of the University of Cyprus. The methodology was designed to provide accurate and robust un-supervised estimation with a measure of uncertainty. Also, it was designed for application on commercial PV plants, where sensor deployment is sparse and data logging capabilities are low due to cost. Therefore, the minimum requirements for the realization of the developed methodology are accurate measurements of power and an accurate measurement of irradiance. The methodology was developed to address four main issues in the field of PV degradation: 1) measurement qualification and creation of a clean data set from uncertain sources, 2) detection of suboptimal performance from the measurement data and assessment of the effect on the actual degradation rate, 3) analysis of time series of constructed performance metrics to extract and analyse the trend in either a linear or non-linear fashion, and 4) substitution of adhoc analyses and empirical parametrisation with formal statistical tests, to enable the applicability of the methodology in an unsupervised way. Therefore, a data pipeline consisting of measurement qualification, creation of performance metrics, detection and treatment of outliers and trend modelling procedures was developed. In addition, the computational expense of implementing such a methodology was explored and alternative ways were proposed to further reduce it. Extensive experimental work has also been performed in order to estimate the RD of the studied PV arrays, under standard test conditions (STC). These experiments were performed ex situ, using high quality laboratory equipment (i.e. flasher, electroluminescence (EL), infrared (IR) thermography), with traceable calibration throughout the evaluation period. Even though the results were more traceable and certain, indoor testing required a significant amount of manual labour and system downtime and introduced risk due to mounting/dismounting and transporting the PV modules to the laboratory. The PV modules under study were characterized in the laboratory and the results were used to benchmark the accuracy of the developed unsupervised methodology. In this way, PV performance measured under a broad spectrum of prevailing meteorological conditions was compared to the results of indoor testing under international standards. This was one of the most important outcomes of this work as this kind of long-term comparison on multiple, co-located PV technologies which were monitored and characterized in a research-grade environment was extremely rare in the bibliography.},
  copyright = {All rights reserved},
  langid = {english},
  school = {University of Cyprus},
  file = {/home/alexis/Zotero/storage/DBN43GLC/Phinikarides - 2017 - Degradation Rate Estimation in Photovoltaics.pdf;/home/alexis/Zotero/storage/SE8FT4U6/Phinikarides - 2017 - Degradation Rate Estimation in Photovoltaics.pdf}
}

Recent advances in photovoltaic (PV) module manufacturing have resulted in the production of highly efficient cells and modules and the significant reduction of the levelized cost of electricity (LCOE) due to the increased demand for the technology. Two key factors that will increase the demand and reduce the LCOE even further are: 1) improving operations and maintenance (O&M) to ensure the optimal operation of deployed PV plants, and 2) accurately estimating the well-known effect of gradual performance degradation and guaranteeing their lifetime energy yield. Both of these key factors require active monitoring and supervision of the deployed PV plants, analysis of field measurement data for estimation of the long-term degradation rate, RD with statistical confidence and comparison with the warranty. This analysis will in turn enable the planning of actions to mitigate the causes of low performance and minimize the amount of energy lost. The accurate estimation of the RD for a deployed PV plant will also enable more accurate and precise lifetime energy yield forecasting and stricter performance guarantees, further reducing investment risk and increasing confidence in the technology. This work deals with developing a generalized data analysis methodology based on statistical principles, for estimating the energy degradation rate, using field measurement data from eleven different grid-connected PV plants operating side-by-side since June 2006 at the PV Technology test site of the University of Cyprus. The methodology was designed to provide accurate and robust un-supervised estimation with a measure of uncertainty. Also, it was designed for application on commercial PV plants, where sensor deployment is sparse and data logging capabilities are low due to cost. Therefore, the minimum requirements for the realization of the developed methodology are accurate measurements of power and an accurate measurement of irradiance. The methodology was developed to address four main issues in the field of PV degradation: 1) measurement qualification and creation of a clean data set from uncertain sources, 2) detection of suboptimal performance from the measurement data and assessment of the effect on the actual degradation rate, 3) analysis of time series of constructed performance metrics to extract and analyse the trend in either a linear or non-linear fashion, and 4) substitution of adhoc analyses and empirical parametrisation with formal statistical tests, to enable the applicability of the methodology in an unsupervised way. Therefore, a data pipeline consisting of measurement qualification, creation of performance metrics, detection and treatment of outliers and trend modelling procedures was developed. In addition, the computational expense of implementing such a methodology was explored and alternative ways were proposed to further reduce it. Extensive experimental work has also been performed in order to estimate the RD of the studied PV arrays, under standard test conditions (STC). These experiments were performed ex situ, using high quality laboratory equipment (i.e. flasher, electroluminescence (EL), infrared (IR) thermography), with traceable calibration throughout the evaluation period. Even though the results were more traceable and certain, indoor testing required a significant amount of manual labour and system downtime and introduced risk due to mounting/dismounting and transporting the PV modules to the laboratory. The PV modules under study were characterized in the laboratory and the results were used to benchmark the accuracy of the developed unsupervised methodology. In this way, PV performance measured under a broad spectrum of prevailing meteorological conditions was compared to the results of indoor testing under international standards. This was one of the most important outcomes of this work as this kind of long-term comparison on multiple, co-located PV technologies which were monitored and characterized in a research-grade environment was extremely rare in the bibliography.

@article{pieriForecastingDegradationRates2017,
  title = {Forecasting Degradation Rates of Different Photovoltaic Systems Using Robust Principal Component Analysis and {{ARIMA}}},
  author = {Pieri, Elena and Kyprianou, Andreas and Phinikarides, Alexander and Makrides, George and Georghiou, George E.},
  year = {2017},
  journal = {IET Renewable Power Generation},
  issn = {1752-1416, 1752-1424},
  doi = {10.1049/iet-rpg.2017.0090},
  abstract = {Degradation rates based on forecasting of performance ratio, Rp, time series are computed and compared with actual degradation rates. A 3-year forecasting of monthly Rp , measured from photovoltaic (PV) connected systems of various technologies is performed using the seasonal auto-regressive integrating moving average (ARIMA) time series model. The seasonal ARIMA model is estimated using monthly Rp measured over a 5-year period and based on this model forecasting is implemented for the subsequent 3 years. The degradation rate at the end of the forecasting period, eighth year, is computed using a robust principal component analysis based methodology. The degradation rates obtained for various (PV) systems are then compared with the ones obtained using the actual 8-year data.},
  copyright = {All rights reserved},
  langid = {english},
  file = {/home/alexis/Zotero/storage/Y5PDRU3T/Pieri et al. - 2017 - Forecasting degradation rates of different photovo.pdf}
}

Degradation rates based on forecasting of performance ratio, Rp, time series are computed and compared with actual degradation rates. A 3-year forecasting of monthly Rp , measured from photovoltaic (PV) connected systems of various technologies is performed using the seasonal auto-regressive integrating moving average (ARIMA) time series model. The seasonal ARIMA model is estimated using monthly Rp measured over a 5-year period and based on this model forecasting is implemented for the subsequent 3 years. The degradation rate at the end of the forecasting period, eighth year, is computed using a robust principal component analysis based methodology. The degradation rates obtained for various (PV) systems are then compared with the ones obtained using the actual 8-year data.

@article{hadjipanayiProspectsPhotovoltaicsSouthern2016,
  title = {Prospects of Photovoltaics in Southern {{European}}, {{Mediterranean}} and {{Middle East}} Regions},
  author = {Hadjipanayi, Maria and Koumparou, Ioannis and Philippou, Nikolas and Paraskeva, Vasiliki and Phinikarides, Alexander and Makrides, George and Efthymiou, Venizelos and Georghiou, George E},
  year = {2016},
  journal = {Renewable Energy},
  volume = {92},
  pages = {58--74},
  issn = {09601481},
  doi = {10.1016/j.renene.2016.01.096},
  abstract = {This review investigates the potential of photovoltaics in southern Europe and Middle East/North Africa in terms of PV status and policies/initiatives for PV market development in the region. In some Sunbelt countries, PV has become a competitive alternative for electricity generation resulting from a combination of high solar resource, decreasing PV system costs and high fuel prices. The PV levelized cost of electricity has fallen in some regions to 0.08 V/kWh whilst retail electricity prices are almost three times higher in some cases attesting to the ideal conditions in the region for PV uptake. In grid parity regions of south Europe, incentives such as feed-in-tariffs have served their purpose. Net metering and self-consumption are proving to be good solutions for driving effectively the PV market as evidenced for the case of Cyprus. In MENA countries, the renewables policy landscape, although still at an exploratory phase, is rapidly developing providing the backbone for a large number of new PV projects. This reflects the region's commitment to meet its ambitious national targets regarding PV. Overall, the timing for the whole region is excellent to achieve energy sustainability, once better policies are adopted and challenges regarding grid integration and reliability are addressed.},
  copyright = {All rights reserved},
  file = {/home/alexis/Zotero/storage/88PB8SH6/Hadjipanayi et al. - 2016 - Prospects of photovoltaics in southern European, M.pdf}
}

This review investigates the potential of photovoltaics in southern Europe and Middle East/North Africa in terms of PV status and policies/initiatives for PV market development in the region. In some Sunbelt countries, PV has become a competitive alternative for electricity generation resulting from a combination of high solar resource, decreasing PV system costs and high fuel prices. The PV levelized cost of electricity has fallen in some regions to 0.08 V/kWh whilst retail electricity prices are almost three times higher in some cases attesting to the ideal conditions in the region for PV uptake. In grid parity regions of south Europe, incentives such as feed-in-tariffs have served their purpose. Net metering and self-consumption are proving to be good solutions for driving effectively the PV market as evidenced for the case of Cyprus. In MENA countries, the renewables policy landscape, although still at an exploratory phase, is rapidly developing providing the backbone for a large number of new PV projects. This reflects the region's commitment to meet its ambitious national targets regarding PV. Overall, the timing for the whole region is excellent to achieve energy sustainability, once better policies are adopted and challenges regarding grid integration and reliability are addressed.

@inproceedings{koumparouCharacterisationMappingDaily2016,
  title = {Characterisation and {{Mapping}} of {{Daily Sky Conditions Based}} on {{Ground}}  {{Measurements}} of {{Solar Irradiance}} in {{Mainland USA}}},
  booktitle = {43rd {{IEEE PVSC}}},
  author = {Koumparou, Ioannis and Phinikarides, Alexander and Makrides, George and Georghiou, George E},
  year = {2016},
  pages = {0986--0991},
  address = {{Portland, OR, USA}},
  doi = {10.1109/PVSC.2016.7749758},
  abstract = {The power produced from solar systems depends strongly on the prevailing weather conditions and more precisely on solar irradiance. Due to the dependence of such systems on the weather conditions the electricity injected into the grid is intermittent in nature with potentially negative impact on the grid operation. The quality and quantity of the electrical power produced from solar systems is directly related to the available solar irradiance and therefore any disturbances to the latter affect the produced power. In this paper, the characterisation and classification of the daily solar irradiance from 12 locations in mainland USA is presented based on 4 years of ground measurements. The K-POP method used evaluates the quantity and quality of solar irradiance for a day and as a consequence classifies the day based on these two indices. The statistical analysis of the results shows high correlation through the years for each station. This is a strong indication that the sky conditions are predictable and that with the utilisation of mechanisms, such as storage, spinning reserve, etc. solar systems can become a major contributor to the energy mix. Finally, this analysis provides better insight into the solar resource of a given location.},
  copyright = {All rights reserved},
  file = {/home/alexis/Zotero/storage/NMXK64PA/Koumparou et al. - 2016 - Characterisation and Mapping of Daily Sky Conditio.pdf}
}

The power produced from solar systems depends strongly on the prevailing weather conditions and more precisely on solar irradiance. Due to the dependence of such systems on the weather conditions the electricity injected into the grid is intermittent in nature with potentially negative impact on the grid operation. The quality and quantity of the electrical power produced from solar systems is directly related to the available solar irradiance and therefore any disturbances to the latter affect the produced power. In this paper, the characterisation and classification of the daily solar irradiance from 12 locations in mainland USA is presented based on 4 years of ground measurements. The K-POP method used evaluates the quantity and quality of solar irradiance for a day and as a consequence classifies the day based on these two indices. The statistical analysis of the results shows high correlation through the years for each station. This is a strong indication that the sky conditions are predictable and that with the utilisation of mechanisms, such as storage, spinning reserve, etc. solar systems can become a major contributor to the energy mix. Finally, this analysis provides better insight into the solar resource of a given location.

@inproceedings{kyprianouForecastingDegradationRates2016,
  title = {Forecasting {{Degradation Rates}} of {{Different Photovoltaic Systems Using Robust Principal Component Analysis}} and {{ARIMA}}},
  booktitle = {32nd {{EU-PVSEC}}},
  author = {Kyprianou, Andreas and Phinikarides, Alexander and Makrides, George and Georghiou, George E},
  year = {2016},
  pages = {2033--2035},
  address = {{Munich, Germany}},
  doi = {10.4229/EUPVSEC20162016-5BV.2.58},
  abstract = {Degradation rates based on forecasting of performance ratio (PR), Rp, time series are computed and compared with actual degradation rates. A three year forecasting of monthly PR, measured from PV connected systems of various technolgies is performed using the seasonal ARIMA (SARIMA) time series model. The seasonal ARIMA model is estimated using monthly PR measured over a 5 year period and based on this model forecasting is implemented for the subsequent three years. The degradation rate  at the end of the forecasting period, eighth year, is computed using a robust principal component analysis (RCPA) based methodology. The degradation rates obtained for various (PV) systems are then compared to the ones obtained using the actual eight year data.},
  copyright = {All rights reserved},
  isbn = {3-936338-41-8},
  file = {/home/alexis/Zotero/storage/59RXHUWR/Kyprianou et al. - 2016 - Forecasting Degradation Rates of Different Photovo.pdf}
}

Degradation rates based on forecasting of performance ratio (PR), Rp, time series are computed and compared with actual degradation rates. A three year forecasting of monthly PR, measured from PV connected systems of various technolgies is performed using the seasonal ARIMA (SARIMA) time series model. The seasonal ARIMA model is estimated using monthly PR measured over a 5 year period and based on this model forecasting is implemented for the subsequent three years. The degradation rate at the end of the forecasting period, eighth year, is computed using a robust principal component analysis (RCPA) based methodology. The degradation rates obtained for various (PV) systems are then compared to the ones obtained using the actual eight year data.

@inproceedings{makridesAdvancedPerformanceMonitoring2016,
  title = {Advanced {{Performance Monitoring System}} for {{Improved Reliability}} and {{Optimized Levelized Cost}} of {{Electricity}}},
  booktitle = {32nd {{EU-PVSEC}}},
  author = {Makrides, George and Phinikarides, Alexander and Sutterlueti, Juergen and Ransome, Steve and Georghiou, George E},
  year = {2016},
  pages = {1973--1977},
  address = {{Munich, Germany}},
  doi = {10.4229/EUPVSEC20162016-5BV.2.38},
  abstract = {The key factor that will enable and enhance the further increase of the uptake of photovoltaic (PV) technology globally, is the reduction in PV electricity costs by increasing the lifetime output of PV systems. This can be achieved by improving the reliability and service lifetime performance through constant, solid and traceable PV plant monitoring of installed systems. In this way, the investment cost, levelised cost of electricity (LCoE) and in general PV competitiveness can be enhanced positively. It is with this background that the project "Innovative Performance Monitoring System for Improved Reliability and Optimized Levelised Cost of Electricity"(IPERMON) funded by the SOLAR-ERA.NET Transnational Calls PV3 and CSP3, has been initiated between Gantner Instruments (GI) GmbH and the PV Technology Laboratory of the University of Cyprus (UCY), in order to develop an innovative monitoring system with enhanced capabilities, far beyond the state-of-the-art. The proposed monitoring system will be capable to detect performance losses and failures, determine the degradation rate and provide accurate hourly and day-ahead power production forecasts. The scope of this work is to present the main scientific, technological and commercial objectives of the project in the field of PV performance monitoring systems and to present first results for the formulation and benchmarking of innovative guidelines and algorithms for the detection and diagnosis of performance losses, degradation and failures.},
  copyright = {All rights reserved},
  isbn = {3-936338-41-8},
  file = {/home/alexis/Zotero/storage/EJ7GK986/Makrides et al. - 2016 - Advanced Performance Monitoring System for Improve.pdf;/home/alexis/Zotero/storage/V4G3QZX7/Makrides et al. - 2016 - Advanced Performance Monitoring System for Improve.pdf}
}

The key factor that will enable and enhance the further increase of the uptake of photovoltaic (PV) technology globally, is the reduction in PV electricity costs by increasing the lifetime output of PV systems. This can be achieved by improving the reliability and service lifetime performance through constant, solid and traceable PV plant monitoring of installed systems. In this way, the investment cost, levelised cost of electricity (LCoE) and in general PV competitiveness can be enhanced positively. It is with this background that the project "Innovative Performance Monitoring System for Improved Reliability and Optimized Levelised Cost of Electricity"(IPERMON) funded by the SOLAR-ERA.NET Transnational Calls PV3 and CSP3, has been initiated between Gantner Instruments (GI) GmbH and the PV Technology Laboratory of the University of Cyprus (UCY), in order to develop an innovative monitoring system with enhanced capabilities, far beyond the state-of-the-art. The proposed monitoring system will be capable to detect performance losses and failures, determine the degradation rate and provide accurate hourly and day-ahead power production forecasts. The scope of this work is to present the main scientific, technological and commercial objectives of the project in the field of PV performance monitoring systems and to present first results for the formulation and benchmarking of innovative guidelines and algorithms for the detection and diagnosis of performance losses, degradation and failures.

@inproceedings{makridesOutdoorPerformanceModelling2016,
  title = {Outdoor {{Performance}} and {{Modelling}} of {{Innovative Crystalline Silicon Photovoltaic Modules Under Hot Climatic Conditions}}},
  booktitle = {32nd {{EU-PVSEC}}},
  author = {Makrides, George and Phinikarides, Alexander and Herzog, Evelyn and Strobel, Matthias B. and Georghiou, George E},
  year = {2016},
  pages = {1991--1996},
  address = {{Munich, Germany}},
  doi = {10.4229/EUPVSEC20162016-5BV.2.44},
  abstract = {The outdoor assessment of photovoltaic (PV) systems provides useful data to validate performance modelling approaches. The scope of this work is to analyse and model the outdoor performance of different grid-connected poly-crystalline Silicon (poly-c Si) PV systems installed at the PV Technology Laboratory of the University of Cyprus (UCY). These systems provided by Hanwha Q CELLS were installed side-by-side at a fixed-plane and monitored for a period of one year. Apart from PV system operational data, meteorological data were also extracted. Specifically, the focus of this ongoing analysis is to compare the performance of different modelling methods against real outdoor energy measurements and to investigate the impact of using real meteorological data for the simulation using the PVWATTS model and the PVSYST simulation software. The annual DC Performance Ratio (PRDC) results using the PVWATTS model and calculated using the PVSYST software showed that the prediction error (PE) was below 2 \% for the PVSYST simulation, whereas for the PVWATTS model PE differences of up to 8 \% were observed when compared to the measured PRDC.},
  copyright = {All rights reserved},
  isbn = {3-936338-41-8},
  file = {/home/alexis/Zotero/storage/75JP4UW2/Makrides et al. - 2016 - Outdoor Performance and Modelling of Innovative Cr.pdf}
}

The outdoor assessment of photovoltaic (PV) systems provides useful data to validate performance modelling approaches. The scope of this work is to analyse and model the outdoor performance of different grid-connected poly-crystalline Silicon (poly-c Si) PV systems installed at the PV Technology Laboratory of the University of Cyprus (UCY). These systems provided by Hanwha Q CELLS were installed side-by-side at a fixed-plane and monitored for a period of one year. Apart from PV system operational data, meteorological data were also extracted. Specifically, the focus of this ongoing analysis is to compare the performance of different modelling methods against real outdoor energy measurements and to investigate the impact of using real meteorological data for the simulation using the PVWATTS model and the PVSYST simulation software. The annual DC Performance Ratio (PRDC) results using the PVWATTS model and calculated using the PVSYST software showed that the prediction error (PE) was below 2 % for the PVSYST simulation, whereas for the PVWATTS model PE differences of up to 8 % were observed when compared to the measured PRDC.

@inproceedings{phinikaridesDevelopmentNovelWeb2016,
  title = {Development of a {{Novel Web Application}} for {{Automatic Photovoltaic System Performance Analysis}} and {{Fault Identification}}},
  booktitle = {43rd {{IEEE PVSC}}},
  author = {Phinikarides, Alexander and Shimitra, Christiana and Bourgeon, Robin and Koumparou, Ioannis and Makrides, George and Georghiou, George E},
  year = {2016},
  pages = {1736--1740},
  address = {{Portland, OR, USA}},
  doi = {10.1109/PVSC.2016.7749921},
  abstract = {This paper details the development of the pvpaR (PV Performance Analysis in R) web application built on open-source technologies for the automated and user-friendly evaluation of photovoltaic (PV) system performance and identif cation and classification of faults. pvpaR's ecosystem is based on the R statistical computing project, both for the back-end as well as for the front-end which uses the Shiny web application framework. Currently, the core of the application incorporates models for synthesizing time-series of irradiance, module temperature, PV system voltage, current, DC and AC power. These are used to validate the imported field measurements and create the comparison which the fault identification function is dependent upon. The web application can currently import measurements from flat files and databases. It has been released under the GNU Affero GPL license to encourage contributions, with the goal to become a useful tool for the PV community and PV system owners.},
  copyright = {All rights reserved},
  file = {/home/alexis/Zotero/storage/4DIVNR5H/Phinikarides et al. - 2016 - Development of a Novel Web Application for Automat.pdf}
}

This paper details the development of the pvpaR (PV Performance Analysis in R) web application built on open-source technologies for the automated and user-friendly evaluation of photovoltaic (PV) system performance and identif cation and classification of faults. pvpaR's ecosystem is based on the R statistical computing project, both for the back-end as well as for the front-end which uses the Shiny web application framework. Currently, the core of the application incorporates models for synthesizing time-series of irradiance, module temperature, PV system voltage, current, DC and AC power. These are used to validate the imported field measurements and create the comparison which the fault identification function is dependent upon. The web application can currently import measurements from flat files and databases. It has been released under the GNU Affero GPL license to encourage contributions, with the goal to become a useful tool for the PV community and PV system owners.

@inproceedings{phinikaridesEstimationDegradationRate2016,
  title = {Estimation of the {{Degradation Rate}} of {{Fielded Photovoltaic Arrays}} in the {{Presence}} of {{Measurement Outages}}},
  booktitle = {32nd {{EU-PVSEC}}},
  author = {Phinikarides, Alexander and Makrides, George and Georghiou, George E},
  year = {2016},
  pages = {1754--1757},
  address = {{Munich, Germany}},
  doi = {10.4229/EUPVSEC20162016-5DO.12.6},
  abstract = {This paper presents a study of the sensitivity of the estimated energy degradation rates of grid-connected crystalline Silicon (c-Si) PV arrays to measurement outages and missing data. The arrays under study have been operating side-by-side since June 2006 in Nicosia, Cyprus. Fifteen-minute average field measurements over their first ten years of operation were used to create a data set, in which invalid measurements were removed and logged system downtimes were corrected based on past performance. The resulting data set was randomly sampled to select data points which were designated as Missing Completely at Random (MCAR) in order to create unbiased artificial outage periods. The same data set was treated with missing data imputation techniques such as imputation by the mean, linear interpolation and imputation by bootstrap. The resulting data sets were then analysed with linear regression (LR), classical seasonal decomposition (CSD) and regARIMA models to extract the trend and estimate the energy degradation rates. The results have shown that regARIMA was the most robust method for up to 10 \% of missing data, the LR and CSD methods were sensitive starting from 2 \% of missing data and that imputation by the bootstrap enhanced the accuracy of the estimated degradation rates up to 20 \% for regARIMA and 40 \% for LR.},
  copyright = {All rights reserved},
  isbn = {3-936338-41-8},
  file = {/home/alexis/Zotero/storage/A7L292XU/Phinikarides et al. - 2016 - Estimation of the Degradation Rate of Fielded Phot.pdf}
}

This paper presents a study of the sensitivity of the estimated energy degradation rates of grid-connected crystalline Silicon (c-Si) PV arrays to measurement outages and missing data. The arrays under study have been operating side-by-side since June 2006 in Nicosia, Cyprus. Fifteen-minute average field measurements over their first ten years of operation were used to create a data set, in which invalid measurements were removed and logged system downtimes were corrected based on past performance. The resulting data set was randomly sampled to select data points which were designated as Missing Completely at Random (MCAR) in order to create unbiased artificial outage periods. The same data set was treated with missing data imputation techniques such as imputation by the mean, linear interpolation and imputation by bootstrap. The resulting data sets were then analysed with linear regression (LR), classical seasonal decomposition (CSD) and regARIMA models to extract the trend and estimate the energy degradation rates. The results have shown that regARIMA was the most robust method for up to 10 % of missing data, the LR and CSD methods were sensitive starting from 2 % of missing data and that imputation by the bootstrap enhanced the accuracy of the estimated degradation rates up to 20 % for regARIMA and 40 % for LR.

@article{kyprianouDefinitionComputationDegradation2015,
  title = {Definition and {{Computation}} of the {{Degradation Rates}} of {{Photovoltaic Systems}} of {{Different Technologies With Robust Principal Component Analysis}}},
  author = {Kyprianou, Andreas and Phinikarides, Alexander and Makrides, George and Georghiou, George E},
  year = {2015},
  journal = {IEEE Journal of Photovoltaics},
  volume = {5},
  number = {6},
  pages = {1698--1705},
  issn = {2156-3381},
  doi = {10.1109/JPHOTOV.2015.2478065},
  abstract = {Grid-connected photovoltaic (PV) systems have become a significant constituent of the power supply mix. A challenge faced by both users and suppliers of PV systems is that of defining and computing a reliable metric of annual degradation rate while in service. This paper defines a new measure to calculate the degradation rate of PV systems from the PV field measured performance ratio (PR). At first, the PR time series is processed by conventional principal component analysis, which yields seasonality as the dominant data feature. The environment, operating conditions, uncertainty, and hardware used for monitoring influence the outdoor measurements unpredictably. These influences are viewed as perturbations that render the dominant feature obtained by PCA unsuitable to be used in a degradation rate definition. Robust principal component analysis (RPCA) is proposed to alleviate these effects. The new measure is defined as the area enclosed by the time series of the corrected by the RPCA annual monthly PR values. The degradation rates obtained for different technologies are compared with those obtained in previous studies. The results have shown that the degradation rates estimated by RPCA were in good agreement with previous investigations and provided increased confidence due to mitigation of uncertainty.},
  copyright = {All rights reserved},
  keywords = {degradation,experimental methods,pv modules},
  file = {/home/alexis/Zotero/storage/9VGWHEI8/Kyprianou et al. - 2015 - Definition and Computation of the Degradation Rate.pdf}
}

Grid-connected photovoltaic (PV) systems have become a significant constituent of the power supply mix. A challenge faced by both users and suppliers of PV systems is that of defining and computing a reliable metric of annual degradation rate while in service. This paper defines a new measure to calculate the degradation rate of PV systems from the PV field measured performance ratio (PR). At first, the PR time series is processed by conventional principal component analysis, which yields seasonality as the dominant data feature. The environment, operating conditions, uncertainty, and hardware used for monitoring influence the outdoor measurements unpredictably. These influences are viewed as perturbations that render the dominant feature obtained by PCA unsuitable to be used in a degradation rate definition. Robust principal component analysis (RPCA) is proposed to alleviate these effects. The new measure is defined as the area enclosed by the time series of the corrected by the RPCA annual monthly PR values. The degradation rates obtained for different technologies are compared with those obtained in previous studies. The results have shown that the degradation rates estimated by RPCA were in good agreement with previous investigations and provided increased confidence due to mitigation of uncertainty.

@inproceedings{phinikaridesAnalysisFieldPerformance2015,
  title = {Analysis of the Field Performance of a Double Junction Amorphous Silicon Photovoltaic Module and Its Correlation to Standardized Testing},
  booktitle = {31st {{EU-PVSEC}}},
  author = {Phinikarides, Alexander and Makrides, George and Georghiou, George E},
  year = {2015},
  pages = {1992--1996},
  address = {{Hamburg, Germany}},
  doi = {10.4229/EUPVSEC20152015-5AV.6.20},
  abstract = {In this work, outdoor and indoor measurements from a double junction amorphous Silicon (a-Si) photovoltaic (PV) module installed at the PV Technology outdoor test site of the University of Cyprus were used to assess the field performance from November 2012 to June 2015. The measurements consisted of continuous current- voltage (I-V) curves from outdoor testing and bi-weekly indoor ratings at standard test conditions (STC) in a solar simulator. In order to accurately evaluate the field performance under varying meteorological conditions, the electrical parameters were extracted from field I-V curves and were then filtered for high irradiance and low angles of incidence, extrapolated to 1000 W/m2 irradiance and corrected for temperature losses. Additionally, the outdoor I-V curves were used to calculate Loss Factor Model (LFM-B) parameters. A comparison of the indoor ratings at STC to each of the two field performance indicators has shown that there was very good agreement with a mean absolute percentage error (MAPE) of 2.9 \{\%\} and 4.47 \{\%\} when using the filtered and corrected PMPP and the LFM-B Performance Factor (PF), respectively. Lastly, the effects of the module's metastable behavior on the performance were analyzed from indoor measurements at STC. It has been shown that the module suffered a degradation rate of 2.36 \{\%\}/year, while the Staebler-Wronski effect and thermal annealing resulted in {$\pm$}3 \{\%\} variation of the performance, observable throughout the year.},
  copyright = {All rights reserved},
  file = {/home/alexis/Zotero/storage/9N2DN3E5/Phinikarides et al. - 2015 - Analysis of the field performance of a double junc.pdf}
}

In this work, outdoor and indoor measurements from a double junction amorphous Silicon (a-Si) photovoltaic (PV) module installed at the PV Technology outdoor test site of the University of Cyprus were used to assess the field performance from November 2012 to June 2015. The measurements consisted of continuous current- voltage (I-V) curves from outdoor testing and bi-weekly indoor ratings at standard test conditions (STC) in a solar simulator. In order to accurately evaluate the field performance under varying meteorological conditions, the electrical parameters were extracted from field I-V curves and were then filtered for high irradiance and low angles of incidence, extrapolated to 1000 W/m2 irradiance and corrected for temperature losses. Additionally, the outdoor I-V curves were used to calculate Loss Factor Model (LFM-B) parameters. A comparison of the indoor ratings at STC to each of the two field performance indicators has shown that there was very good agreement with a mean absolute percentage error (MAPE) of 2.9 \%\ and 4.47 \%\ when using the filtered and corrected PMPP and the LFM-B Performance Factor (PF), respectively. Lastly, the effects of the module's metastable behavior on the performance were analyzed from indoor measurements at STC. It has been shown that the module suffered a degradation rate of 2.36 \%\/year, while the Staebler-Wronski effect and thermal annealing resulted in $±$3 \%\ variation of the performance, observable throughout the year.

@article{phinikaridesAnalysisPhotovoltaicSystem2015,
  title = {Analysis of Photovoltaic System Performance Time Series: Seasonality and Performance Loss},
  author = {Phinikarides, Alexander and Makrides, George and Zinsser, Bastian and Schubert, Markus and Georghiou, George E},
  year = {2015},
  journal = {Renewable Energy},
  volume = {77},
  pages = {51--63},
  doi = {10.1016/j.renene.2014.11.091},
  abstract = {In this work, the seasonality and performance loss rates of eleven grid-connected photovoltaic (PV) systems of different technologies were evaluated through seasonal adjustment. The classical seasonal decomposition (CSD) and X-12-ARIMA statistical techniques were applied on monthly DC performance ratio, RP, time series, constructed from field measurements over the systems' first five years of operation. The results have shown that the RP of crystalline silicon (c-Si) technologies was higher during winter. This was also the case for the coppereindium gallium-diselenide (CIGS) and cadmium telluride (CdTe) technologies but with lower seasonal amplitude. The amorphous silicon (a-Si) technology exhibited a different seasonal profile, with high RP during summer and autumn and low during winter. In addition, the trends extracted from the application of CSD and X-12-ARIMA on three-year, four-year and five-year RP time series were used to estimate linear performance loss rates. A comparison between standard linear regression (LR), CSD and X-12-ARIMA has shown that CSD and X-12-ARIMA resulted in higher rates overall for c-Si, 1.07 and 0.93\{\%\}/year respectively, but with significantly less uncertainty than LR. Lastly, it was shown that X-12-ARIMA provided statistical inference in the presence of outliers and produced model residuals that were uncorrelated, in contrast to CSD.},
  copyright = {All rights reserved},
  keywords = {arima,csd},
  file = {/home/alexis/Zotero/storage/X5BUTPSR/Phinikarides et al. - 2015 - Analysis of photovoltaic system performance time s.pdf}
}

In this work, the seasonality and performance loss rates of eleven grid-connected photovoltaic (PV) systems of different technologies were evaluated through seasonal adjustment. The classical seasonal decomposition (CSD) and X-12-ARIMA statistical techniques were applied on monthly DC performance ratio, RP, time series, constructed from field measurements over the systems' first five years of operation. The results have shown that the RP of crystalline silicon (c-Si) technologies was higher during winter. This was also the case for the coppereindium gallium-diselenide (CIGS) and cadmium telluride (CdTe) technologies but with lower seasonal amplitude. The amorphous silicon (a-Si) technology exhibited a different seasonal profile, with high RP during summer and autumn and low during winter. In addition, the trends extracted from the application of CSD and X-12-ARIMA on three-year, four-year and five-year RP time series were used to estimate linear performance loss rates. A comparison between standard linear regression (LR), CSD and X-12-ARIMA has shown that CSD and X-12-ARIMA resulted in higher rates overall for c-Si, 1.07 and 0.93\%\/year respectively, but with significantly less uncertainty than LR. Lastly, it was shown that X-12-ARIMA provided statistical inference in the presence of outliers and produced model residuals that were uncorrelated, in contrast to CSD.

@inproceedings{phinikaridesEstimationAnnualPerformance2015,
  title = {Estimation of Annual Performance Loss Rates of Grid-Connected Photovoltaic Systems Using Time Series Analysis and Validation through Indoor Testing at Standard Test Conditions},
  booktitle = {42nd {{IEEE PVSC}}},
  author = {Phinikarides, Alexander and Makrides, George and Georghiou, George E},
  year = {2015},
  pages = {1--5},
  address = {{New Orleans, LA}},
  doi = {10.1109/PVSC.2015.7355940},
  abstract = {This paper presents the results of an extensive testing campaign for validating the time series analysis approach to the estimation of the linear field performance loss rates (PLR) of grid-connected photovoltaic (PV) systems of different technologies operating side-by-side at the PV Technology test site of the University of Cyprus since June 2006. Fifteen-minute average measurements of the array power at the maximum power point, PA, were used to construct time series of the performance ratio, RP, of each array. The time series were analysed with regARIMA and classical seasonal decomposition (CSD) in order to extract the trend. Then, linear regression (LR) was used to calculate the slope. To validate the results, all arrays were disassembled and every module was tested at Standard Test Conditions (STC) in a class A+A+A+ solar simulator, in order to calculate the nominal array degradation rate. Comparison of both methods has shown good agreement between the time series analysis approach and the indoor testing approach, for PV arrays with no identified failures through electroluminescence (EL). On the contrary, for modules with identified failures through EL, the nominal array degradation rate was higher in comparison to the field PLR. Differences between the two methods have been shown to be due to cracked cells, hotspots and spectral response mismatch. Lastly, the comparison has shown that amongst the time series analysis methods, regARIMA produced statistically significant PLR with low uncertainty and the best agreement with the nominal array degradation rates.},
  bibbase_note = {<span style="color: white; background-color: green; font-weight: bold">Best Student Paper Award</span>},
  copyright = {All rights reserved},
  keywords = {arima,award,csd},
  file = {/home/alexis/Zotero/storage/MZT5KQU9/Phinikarides et al. - 2015 - Estimation of annual performance loss rates of gri.pdf}
}

This paper presents the results of an extensive testing campaign for validating the time series analysis approach to the estimation of the linear field performance loss rates (PLR) of grid-connected photovoltaic (PV) systems of different technologies operating side-by-side at the PV Technology test site of the University of Cyprus since June 2006. Fifteen-minute average measurements of the array power at the maximum power point, PA, were used to construct time series of the performance ratio, RP, of each array. The time series were analysed with regARIMA and classical seasonal decomposition (CSD) in order to extract the trend. Then, linear regression (LR) was used to calculate the slope. To validate the results, all arrays were disassembled and every module was tested at Standard Test Conditions (STC) in a class A+A+A+ solar simulator, in order to calculate the nominal array degradation rate. Comparison of both methods has shown good agreement between the time series analysis approach and the indoor testing approach, for PV arrays with no identified failures through electroluminescence (EL). On the contrary, for modules with identified failures through EL, the nominal array degradation rate was higher in comparison to the field PLR. Differences between the two methods have been shown to be due to cracked cells, hotspots and spectral response mismatch. Lastly, the comparison has shown that amongst the time series analysis methods, regARIMA produced statistically significant PLR with low uncertainty and the best agreement with the nominal array degradation rates.

@inproceedings{kyprianouRobustPrincipalComponent2014,
  title = {Robust {{Principal Component Analysis For Computing The Degradation Rates Of Different Photovoltaic Systems}}},
  booktitle = {29th {{EU-PVSEC}}},
  author = {Kyprianou, Andreas and Phinikarides, Alexander and Makrides, George and Georghiou, George E},
  year = {2014},
  pages = {2939--2942},
  address = {{Amsterdam}},
  doi = {10.4229/EUPVSEC20142014-5BV.2.41},
  abstract = {A new methodology for computing degradation rates of photovoltaic (PV) systems based on robust principal component analysis (PCA) is proposed. Conventional PCA demonstrates that performance ratio (PR), Rp, time series contain two significant features attributed to seasonality and uncertainty. Robust PCA is used in order to remove the effects of uncertainty from the original PR time series. The data obtained after removing the effects of uncertainty is then used for computing a newly defined degradation rate measure, which is based on the area enclosed by the curves of the PR time series of the first and the last year of evaluation. In addition, the degradation rate results are compared with those obtained in the previous studies using the conventional linear regression methodology.},
  bibbase_note = {<span style="color: white; background-color: green; font-weight: bold">Best Poster Award</span>},
  copyright = {All rights reserved},
  keywords = {award,degradation,experimental methods,pv modules},
  file = {/home/alexis/Zotero/storage/2PHI4DXN/Kyprianou et al. - 2014 - Robust Principal Component Analysis For Computing .pdf}
}

A new methodology for computing degradation rates of photovoltaic (PV) systems based on robust principal component analysis (PCA) is proposed. Conventional PCA demonstrates that performance ratio (PR), Rp, time series contain two significant features attributed to seasonality and uncertainty. Robust PCA is used in order to remove the effects of uncertainty from the original PR time series. The data obtained after removing the effects of uncertainty is then used for computing a newly defined degradation rate measure, which is based on the area enclosed by the curves of the PR time series of the first and the last year of evaluation. In addition, the degradation rate results are compared with those obtained in the previous studies using the conventional linear regression methodology.

@inproceedings{phinikaridesComparisonTrendExtraction2014,
  title = {Comparison of Trend Extraction Methods for Calculating Performance Loss Rates of Different Photovoltaic Technologies},
  booktitle = {40th {{IEEE PVSC}}},
  author = {Phinikarides, Alexander and Makrides, George and Kindyni, Nitsa and Georghiou, George E},
  year = {2014},
  pages = {3211--3215},
  address = {{Denver, CO}},
  doi = {10.1109/PVSC.2014.6925619},
  abstract = {In this work, the performance loss rates of eleven grid-connected photovoltaic (PV) systems of different technologies were evaluated by applying linear regression (LR) and trend extraction methods to Performance Ratio, RP, time series. In particular, model-based methods such as Classical Seasonal Decomposition (CSD), Holt-Winters (HW) exponential smoothing and Autoregressive Integrated Moving Average (ARIMA), as well as non-parametric filtering methods such as LOcally wEighted Scatterplot Smoothing (LOESS) were used to extract the trend from monthly RP time series of the first five years of operation of each PV system. The results showed that applying LR on the time series produced the lowest performance loss rates for most systems, but with significant autocorrelations in the residuals, signifying statistical inaccuracy. The application of CSD and HW significantly reduced the residual autocorrelations as the seasonal component was extracted from the time series, resulting in comparable results for eight out of eleven PV systems, with a mean absolute percentage error (MAPE) of 6.22 \{\%\} between the performance loss rates calculated from each method. Finally, the optimal use of multiplicative ARIMA resulted in Gaussian white noise (GWN) residuals and the most accurate statistical model of the RP time series. ARIMA produced higher performance loss rates than LR for all technologies, except the amorphous Silicon (a-Si) system. The LOESS non-parametric method produced directly comparable results to multiplicative ARIMA, with a MAPE of -2.04 \{\%\} between the performance loss rates calculated from each method, whereas LR, CSD and HW showed higher deviation from ARIMA, with MAPE of 25.14 \{\%\}, -13.71 \{\%\} and -6.39 \{\%\}, respectively.},
  bibbase_note = {<span style="color: white; background-color: green; font-weight: bold">Finalist for Best Poster Award</span>},
  copyright = {All rights reserved},
  keywords = {nomination},
  file = {/home/alexis/Zotero/storage/ZCAWT4C2/Phinikarides et al. - 2014 - Comparison of trend extraction methods for calcula.pdf}
}

In this work, the performance loss rates of eleven grid-connected photovoltaic (PV) systems of different technologies were evaluated by applying linear regression (LR) and trend extraction methods to Performance Ratio, RP, time series. In particular, model-based methods such as Classical Seasonal Decomposition (CSD), Holt-Winters (HW) exponential smoothing and Autoregressive Integrated Moving Average (ARIMA), as well as non-parametric filtering methods such as LOcally wEighted Scatterplot Smoothing (LOESS) were used to extract the trend from monthly RP time series of the first five years of operation of each PV system. The results showed that applying LR on the time series produced the lowest performance loss rates for most systems, but with significant autocorrelations in the residuals, signifying statistical inaccuracy. The application of CSD and HW significantly reduced the residual autocorrelations as the seasonal component was extracted from the time series, resulting in comparable results for eight out of eleven PV systems, with a mean absolute percentage error (MAPE) of 6.22 \%\ between the performance loss rates calculated from each method. Finally, the optimal use of multiplicative ARIMA resulted in Gaussian white noise (GWN) residuals and the most accurate statistical model of the RP time series. ARIMA produced higher performance loss rates than LR for all technologies, except the amorphous Silicon (a-Si) system. The LOESS non-parametric method produced directly comparable results to multiplicative ARIMA, with a MAPE of -2.04 \%\ between the performance loss rates calculated from each method, whereas LR, CSD and HW showed higher deviation from ARIMA, with MAPE of 25.14 \%\, -13.71 \%\ and -6.39 \%\, respectively.

@inproceedings{phinikaridesPerformanceLossRates2014,
  title = {Performance Loss Rates of Different Photovoltaic Technologies after Eight Years of Operation under Warm Climate Conditions},
  booktitle = {29th {{EU-PVSEC}}},
  author = {Phinikarides, Alexander and Philippou, Nikolas and Makrides, George and Georghiou, George E},
  year = {2014},
  pages = {2664--2668},
  address = {{Amsterdam}},
  doi = {10.4229/EUPVSEC20142014-5BV.1.27},
  abstract = {In this paper, the performance loss rates of different technology crystalline silicon (c-Si) and thin-film photovoltaic (PV) systems were estimated and compared over their first eight years of operation at the test site of the Photovoltaic Technology Laboratory, University of Cyprus (UCY) in Nicosia, Cyprus, by applying different statistical trend analysis methods on monthly Performance Ratio, RP, time series. The statistical trend analysis methods include Linear Regression (LR), Classical Seasonal Decomposition (CSD), Holt-Winters exponential smoothing (HW) and LOcally wEighted Scatterplot Smoothing (LOESS) and were applied on monthly constructed time series of RP, calculated from the fifteen-minute average array DC power at the maximum power point, PA, of each grid-connected PV system. The comparison of the estimated performance loss rates for each technology showed that the average performance loss rate of the c-Si systems was 0.75 {$\pm$} 0.17 \{\%\}/year. On the other hand, the average performance loss rate for the thin-film systems was 1.95 {$\pm$} 0.11 \{\%\}/year for all methods, with a 95 \{\%\} confidence interval. The good agreement in the results between the different methods for each system also provided evidence that the performance loss rates have started to converge to a steady value. Finally, it was demonstrated that trend extraction techniques produced similar estimates between them and with very low uncertainty, even with less than five years of outdoor exposure, whereas LR was the least robust method for all technologies, since it was greatly affected by the seasonality and outliers of the time series and needed more years of data to produce reliable estimates.},
  copyright = {All rights reserved},
  keywords = {nomination},
  file = {/home/alexis/Zotero/storage/KFB9F4DP/Phinikarides et al. - 2014 - Performance loss rates of different photovoltaic t.pdf}
}

In this paper, the performance loss rates of different technology crystalline silicon (c-Si) and thin-film photovoltaic (PV) systems were estimated and compared over their first eight years of operation at the test site of the Photovoltaic Technology Laboratory, University of Cyprus (UCY) in Nicosia, Cyprus, by applying different statistical trend analysis methods on monthly Performance Ratio, RP, time series. The statistical trend analysis methods include Linear Regression (LR), Classical Seasonal Decomposition (CSD), Holt-Winters exponential smoothing (HW) and LOcally wEighted Scatterplot Smoothing (LOESS) and were applied on monthly constructed time series of RP, calculated from the fifteen-minute average array DC power at the maximum power point, PA, of each grid-connected PV system. The comparison of the estimated performance loss rates for each technology showed that the average performance loss rate of the c-Si systems was 0.75 $±$ 0.17 \%\/year. On the other hand, the average performance loss rate for the thin-film systems was 1.95 $±$ 0.11 \%\/year for all methods, with a 95 \%\ confidence interval. The good agreement in the results between the different methods for each system also provided evidence that the performance loss rates have started to converge to a steady value. Finally, it was demonstrated that trend extraction techniques produced similar estimates between them and with very low uncertainty, even with less than five years of outdoor exposure, whereas LR was the least robust method for all technologies, since it was greatly affected by the seasonality and outliers of the time series and needed more years of data to produce reliable estimates.

@article{phinikaridesReviewPhotovoltaicDegradation2014,
  title = {Review of Photovoltaic Degradation Rate Methodologies},
  author = {Phinikarides, Alexander and Kindyni, Nitsa and Makrides, George and Georghiou, George E},
  year = {2014},
  journal = {Renewable and Sustainable Energy Reviews},
  volume = {40},
  pages = {143--152},
  issn = {13640321},
  doi = {10.1016/j.rser.2014.07.155},
  abstract = {This paper provides a review of methodologies for measuring the degradation rate, RD, of photovoltaic (PV) technologies, as reported in the literature. As presented in this paper, each method yields different results with varying uncertainty depending on the measuring equipment, the data qualification and filtering criteria, the performance metric and the statistical method of estimation of the trend. This imposes the risk of overestimating or underestimating the true degradation rate and, subsequently, the effective lifetime of a PV module/array/system and proves the need for defining a standardized methodology. Through a literature search, four major statistical analysis methods were recognized for calculating degradation rates: (1) Linear Regression (LR), (2) Classical Seasonal Decomposition (CSD), (3) AutoRegressive Integrated Moving Average (ARIMA) and, (4) LOcally wEighted Scatterplot Smoothing (LOESS), with LR being the most common. These analyses were applied on the following performance metrics: (1) electrical parameters from IV curves recorded under outdoor or simulated indoor conditions and corrected to STC, (2) regression models such as the Photovoltaics for Utility Scale Applications (PVUSA) and Sandia models, (3) normalized ratings such as Performance Ratio, RP, and PMPP/GI and, (4) scaled ratings such as PMPP/Pmax, PAC/Pmax and kWh/kWp. The degradation rate results have shown that the IV method produced the lowest RD and LR produced results with large variation and the largest uncertainty. The ARIMA and LOESS methods, albeit less popular, produced results with low variation and uncertainty and with good agreement between them. Most importantly, this review showed that the RD is not only technology and site dependent, but also methodology dependent.},
  copyright = {All rights reserved},
  keywords = {degradation,durability,photovoltaic,Statistical analysis,weathering},
  file = {/home/alexis/Zotero/storage/XED7USWT/Phinikarides et al. - 2014 - Review of photovoltaic degradation rate methodolog.pdf}
}

This paper provides a review of methodologies for measuring the degradation rate, RD, of photovoltaic (PV) technologies, as reported in the literature. As presented in this paper, each method yields different results with varying uncertainty depending on the measuring equipment, the data qualification and filtering criteria, the performance metric and the statistical method of estimation of the trend. This imposes the risk of overestimating or underestimating the true degradation rate and, subsequently, the effective lifetime of a PV module/array/system and proves the need for defining a standardized methodology. Through a literature search, four major statistical analysis methods were recognized for calculating degradation rates: (1) Linear Regression (LR), (2) Classical Seasonal Decomposition (CSD), (3) AutoRegressive Integrated Moving Average (ARIMA) and, (4) LOcally wEighted Scatterplot Smoothing (LOESS), with LR being the most common. These analyses were applied on the following performance metrics: (1) electrical parameters from IV curves recorded under outdoor or simulated indoor conditions and corrected to STC, (2) regression models such as the Photovoltaics for Utility Scale Applications (PVUSA) and Sandia models, (3) normalized ratings such as Performance Ratio, RP, and PMPP/GI and, (4) scaled ratings such as PMPP/Pmax, PAC/Pmax and kWh/kWp. The degradation rate results have shown that the IV method produced the lowest RD and LR produced results with large variation and the largest uncertainty. The ARIMA and LOESS methods, albeit less popular, produced results with low variation and uncertainty and with good agreement between them. Most importantly, this review showed that the RD is not only technology and site dependent, but also methodology dependent.

@inproceedings{makridesPerformanceLossRates2013,
  title = {Performance Loss Rates of Grid-Connected Photovoltaic Technologies in Warm Climates},
  booktitle = {Global {{Conference On Renewables}} and {{Energy Efficiency}} for {{Desert Regions}}},
  author = {Makrides, George and Phinikarides, Alexander and Georghiou, George E},
  year = {2013},
  pages = {300--304},
  abstract = {With the current uptake and market penetration of different technology photovoltaics (PV), important questions arise regarding their lifetime power decline and degradation. Another important consideration is the influence of different climatic conditions on the exhibited degradation rates, with warmer operating conditions theoretically affecting module components to a higher extent compared to lower temperatures. The purpose of this paper is to present a comparison of the annual performance loss rates of different photovoltaic (PV) systems, ranging from mono-crystalline silicon (mono-c-Si) to multi-crystalline silicon (multi-c-Si) and thin-film technologies, installed in Cyprus over a period of five years. The results of the performance loss rate investigation showed that the mono-c-Si and multi-c-Si systems exhibited average annual performance loss rates that were lower than the 1 \{\%\}/year stated by most PV module manufactures. Conversely, the average annual performance loss rate of the thin-film systems was -1.78 \{\%\}/year.},
  copyright = {All rights reserved},
  file = {/home/alexis/Zotero/storage/GJR5NAJ3/Makrides et al. - 2013 - Performance loss rates of grid-connected photovolt.pdf}
}

With the current uptake and market penetration of different technology photovoltaics (PV), important questions arise regarding their lifetime power decline and degradation. Another important consideration is the influence of different climatic conditions on the exhibited degradation rates, with warmer operating conditions theoretically affecting module components to a higher extent compared to lower temperatures. The purpose of this paper is to present a comparison of the annual performance loss rates of different photovoltaic (PV) systems, ranging from mono-crystalline silicon (mono-c-Si) to multi-crystalline silicon (multi-c-Si) and thin-film technologies, installed in Cyprus over a period of five years. The results of the performance loss rate investigation showed that the mono-c-Si and multi-c-Si systems exhibited average annual performance loss rates that were lower than the 1 \%\/year stated by most PV module manufactures. Conversely, the average annual performance loss rate of the thin-film systems was -1.78 \%\/year.

@inproceedings{phinikaridesARIMAModelingPerformance2013,
  title = {{{ARIMA}} Modeling of the Performance of Different Photovoltaic Technologies},
  booktitle = {39th {{IEEE PVSC}}},
  author = {Phinikarides, Alexander and Makrides, George and Kindyni, Nitsa and Kyprianou, Andreas and Georghiou, George E},
  year = {2013},
  pages = {797--801},
  address = {{Tampa, FL}},
  doi = {10.1109/PVSC.2013.6744268},
  abstract = {In this paper, the performance of different technology photovoltaic (PV) systems was modeled using autoregressive integrated moving average (ARIMA) processes. Measurements from mono-crystalline (mono-c-Si), multi-crystalline (multi-c-Si) and amorphous (a-Si) silicon, cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS) systems were used to construct monthly dc performance ratio (PR) time-series, from outdoor measurements. Each PR time-series was modeled a) with multiplicative ARIMA, b) with linear regression and c) with Seasonal-Trend Decomposition by Loess (STL) using the first 4 years of each time-series in order to compare the accuracy of the different methods. The models were used to forecast the PR of the 5th year of the different PV technologies and the results from the aforementioned statistical methods were compared based on the root-mean-square error (RMSE). The results showed that ARIMA produced the lowest RMSE for crystalline silicon (c-Si) technologies, whereas for thin-film technologies, STL was more accurate. The results from ARIMA also showed that thin-film technologies were optimally modeled with identical model orders, whereas for c-Si, each technology required a different optimal model order.},
  copyright = {All rights reserved},
  isbn = {978-1-4799-3299-3},
  file = {/home/alexis/Zotero/storage/HQ79BHXR/Phinikarides et al. - 2013 - ARIMA modeling of the performance of different pho.pdf}
}

In this paper, the performance of different technology photovoltaic (PV) systems was modeled using autoregressive integrated moving average (ARIMA) processes. Measurements from mono-crystalline (mono-c-Si), multi-crystalline (multi-c-Si) and amorphous (a-Si) silicon, cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS) systems were used to construct monthly dc performance ratio (PR) time-series, from outdoor measurements. Each PR time-series was modeled a) with multiplicative ARIMA, b) with linear regression and c) with Seasonal-Trend Decomposition by Loess (STL) using the first 4 years of each time-series in order to compare the accuracy of the different methods. The models were used to forecast the PR of the 5th year of the different PV technologies and the results from the aforementioned statistical methods were compared based on the root-mean-square error (RMSE). The results showed that ARIMA produced the lowest RMSE for crystalline silicon (c-Si) technologies, whereas for thin-film technologies, STL was more accurate. The results from ARIMA also showed that thin-film technologies were optimally modeled with identical model orders, whereas for c-Si, each technology required a different optimal model order.

@inproceedings{phinikaridesComparisonAnalysisMethods2013,
  title = {Comparison of Analysis Methods for the Calculation of Degradation Rates of Different Photovoltaic Technologies},
  booktitle = {28th {{EU-PVSEC}}},
  author = {Phinikarides, Alexander and Makrides, George and Georghiou, George E},
  year = {2013},
  pages = {3973--3976},
  address = {{Paris, France}},
  doi = {10.4229/28thEUPVSEC2013-5BV.4.39},
  abstract = {The degradation rates of crystalline silicon (c-Si) and thin-film photovoltaic (PV) systems of different manufacturers and different technologies were calculated and compared for the systems' first five years of outdoors exposure, by applying a host of different analysis methods, in order to quantify the differences between each method. These include linear regression using linear least squares (LLS), classical seasonal decomposition (CSD) and seasonal-trend decomposition by Loess (STL) on daily and monthly time series of two performance metrics, performance ratio (PR) and PR with temperature correction (PR-TC). The comparison of the resulting degradation rates for each PV group (c-Si and thin-film) showed that the monthly PR-TC-STL method provided the lowest standard deviation and a mean degradation rate of 1.12 \{\%\}/year for the c-Si PV systems. On the other hand, the daily PR-TC-LLS method demonstrated the lowest standard deviation and an average degradation rate of 2.47 \{\%\}/year for the thin-film PV systems. Linear regression using LLS produced the lowest degradation rates overall, but when temperature correction was applied, the calculated degradation rates were increased by 0.4 \{\%\}/year. LLS also showed the lowest standard deviation for the thin-film PV systems, which was further reduced by applying temperature correction.},
  copyright = {All rights reserved},
  keywords = {crystalline,degradation,Grid-connected,thin film},
  file = {/home/alexis/Zotero/storage/6RNW2XKX/Phinikarides et al. - 2013 - Comparison of analysis methods for the calculation.pdf}
}

The degradation rates of crystalline silicon (c-Si) and thin-film photovoltaic (PV) systems of different manufacturers and different technologies were calculated and compared for the systems' first five years of outdoors exposure, by applying a host of different analysis methods, in order to quantify the differences between each method. These include linear regression using linear least squares (LLS), classical seasonal decomposition (CSD) and seasonal-trend decomposition by Loess (STL) on daily and monthly time series of two performance metrics, performance ratio (PR) and PR with temperature correction (PR-TC). The comparison of the resulting degradation rates for each PV group (c-Si and thin-film) showed that the monthly PR-TC-STL method provided the lowest standard deviation and a mean degradation rate of 1.12 \%\/year for the c-Si PV systems. On the other hand, the daily PR-TC-LLS method demonstrated the lowest standard deviation and an average degradation rate of 2.47 \%\/year for the thin-film PV systems. Linear regression using LLS produced the lowest degradation rates overall, but when temperature correction was applied, the calculated degradation rates were increased by 0.4 \%\/year. LLS also showed the lowest standard deviation for the thin-film PV systems, which was further reduced by applying temperature correction.

@article{makridesTemperatureThermalAnnealing2012,
  title = {Temperature and Thermal Annealing Effects on Different Photovoltaic Technologies},
  author = {Makrides, George and Zinsser, Bastian and Phinikarides, Alexander and Schubert, Markus and Georghiou, George E},
  year = {2012},
  journal = {Renewable Energy},
  volume = {43},
  pages = {407--417},
  issn = {09601481},
  doi = {10.1016/j.renene.2011.11.046},
  abstract = {The effect of temperature on different grid-connected photovoltaic (PV) technologies installed in Cyprus was analyzed in this study. Initially, the performance losses due to the temperature effect on the annual energy yield of each technology were investigated using measurements of module temperature and the manufacturer provided maximum power point (MPP) temperature coefficients, gPMPP. The same methodology was also applied using outdoor evaluated gPMPP coefficients for comparison. When using the manufacturer's temperature coefficient, the results showed that over the evaluation period the highest average thermal losses in annual dc energy yield were 8\{\%\} for mono-crystalline silicon (mono-c-Si) and 9\{\%\} for multi-crystalline silicon (multi-c-Si) technologies while for thin-film technologies, the average losses were 5\{\%\}. Similar losses were found when using the outdoor evaluated temperature coefficients. Additionally, temperature effects on the seasonal performance of the different technologies were evident on the monthly average performance ratio (PR). For the amorphous silicon (a-Si) technologies, a performance increase from spring until early autumn was observed and was attributed to thermal annealing. The effect of thermal annealing on the performance was evident by filtering dc MPP power measurements at high irradiance (greater than 800 W/m2) and restricting the values at geometric air mass (AM) in the range 1 \{\textbackslash textless\}= geometric AM \{\textbackslash textless\}= 1.5. The extracted dc MPP power was corrected for irradiance and temperature at standard test conditions (STC) using the manufacturer provided gPMPP over a period of two years. Subsequently, the effect of thermal annealing was further investigated by extracting dc MPP power measurements at geometric AM in the range 1.4 \{\textbackslash textless\}= geometric AM \{\textbackslash textless\}= 1.6 in order to minimize the spectral influences on the performance of a-Si technologies. An increase in power for all the a-Si technologies was obvious during the warm summer season and was recorded over the period of March until September for both years.},
  copyright = {All rights reserved},
  file = {/home/alexis/Zotero/storage/48MZUB6M/Makrides et al. - 2012 - Temperature and thermal annealing effects on diffe.pdf}
}

The effect of temperature on different grid-connected photovoltaic (PV) technologies installed in Cyprus was analyzed in this study. Initially, the performance losses due to the temperature effect on the annual energy yield of each technology were investigated using measurements of module temperature and the manufacturer provided maximum power point (MPP) temperature coefficients, gPMPP. The same methodology was also applied using outdoor evaluated gPMPP coefficients for comparison. When using the manufacturer's temperature coefficient, the results showed that over the evaluation period the highest average thermal losses in annual dc energy yield were 8\%\ for mono-crystalline silicon (mono-c-Si) and 9\%\ for multi-crystalline silicon (multi-c-Si) technologies while for thin-film technologies, the average losses were 5\%\. Similar losses were found when using the outdoor evaluated temperature coefficients. Additionally, temperature effects on the seasonal performance of the different technologies were evident on the monthly average performance ratio (PR). For the amorphous silicon (a-Si) technologies, a performance increase from spring until early autumn was observed and was attributed to thermal annealing. The effect of thermal annealing on the performance was evident by filtering dc MPP power measurements at high irradiance (greater than 800 W/m2) and restricting the values at geometric air mass (AM) in the range 1 \\ textless\= geometric AM \\ textless\= 1.5. The extracted dc MPP power was corrected for irradiance and temperature at standard test conditions (STC) using the manufacturer provided gPMPP over a period of two years. Subsequently, the effect of thermal annealing was further investigated by extracting dc MPP power measurements at geometric AM in the range 1.4 \\ textless\= geometric AM \\ textless\= 1.6 in order to minimize the spectral influences on the performance of a-Si technologies. An increase in power for all the a-Si technologies was obvious during the warm summer season and was recorded over the period of March until September for both years.

@inproceedings{phinikaridesInitialPerformanceDegradation2012,
  title = {Initial Performance Degradation of an A-{{Si}}/a-{{Si}} Tandem {{PV}} Array},
  booktitle = {27th {{EU-PVSEC}}},
  author = {Phinikarides, Alexander and Makrides, George and Georghiou, George E},
  year = {2012},
  pages = {3267--3270},
  address = {{Frankfurt, Germany}},
  doi = {10.4229/27thEUPVSEC2012-4BV.2.16},
  abstract = {The initial performance degradation of an a-Si/a-Si tandem PV array has been analysed using temperature corrected dc maximum power point (mpp) measurements from a 1 kWp system, Pmpp,dc, and periodic ratings at STC, Pmpp,STC, of a separate, field exposed module. The measurements from the PV system showed a 16.9\{\%\} percentage reduction of the Pmpp,dc from the initial unstabilized Pmpp,dc in the first 3 months of operation. In the next 4 months, a further 8.6\{\%\} reduction was observed. The indoor measurements at STC showed comparable results; 13.66\{\%\} reduction of the Pmpp,STC in the first 3 months and 6.95\{\%\} in the next 4 months. It is evident then, that there was rapid degradation during the first 3 months of operation of the PV system, which was reduced in the subsequent months.},
  copyright = {All rights reserved},
  keywords = {a-si,degradation,pv array,pv module,stc,tandem},
  file = {/home/alexis/Zotero/storage/5WJF9IG4/Phinikarides et al. - 2012 - Initial performance degradation of an a-Sia-Si ta.pdf}
}

The initial performance degradation of an a-Si/a-Si tandem PV array has been analysed using temperature corrected dc maximum power point (mpp) measurements from a 1 kWp system, Pmpp,dc, and periodic ratings at STC, Pmpp,STC, of a separate, field exposed module. The measurements from the PV system showed a 16.9\%\ percentage reduction of the Pmpp,dc from the initial unstabilized Pmpp,dc in the first 3 months of operation. In the next 4 months, a further 8.6\%\ reduction was observed. The indoor measurements at STC showed comparable results; 13.66\%\ reduction of the Pmpp,STC in the first 3 months and 6.95\%\ in the next 4 months. It is evident then, that there was rapid degradation during the first 3 months of operation of the PV system, which was reduced in the subsequent months.

@inproceedings{makridesPhotovoltaicModelUncertainties2011,
  title = {Photovoltaic Model Uncertainties Based on Field Measurements},
  booktitle = {37th {{IEEE PVSC}}},
  author = {Makrides, George and Zinsser, Bastian and Phinikarides, Alexander and Norton, Matthew and Georghiou, George E and Schubert, Markus and Werner, J{\"u}rgen H},
  year = {2011},
  pages = {2386--2390},
  address = {{Seattle, WA}},
  doi = {10.1109/PVSC.2011.6186430},
  abstract = {Mathematical and empirical models have long been used to describe the output behaviour of photovoltaic (PV) systems. The purpose of this paper is to compare the combined uncertainties inherent in the results when using three of these models; the single-point efficiency, the single-point efficiency with temperature correction and the PVUSA model. This evaluation was performed using outdoor measurement data from 12 different grid- connected PV systems of 1 kWp each, operating in Cyprus since June 2006 along with measurement data from the meteorological sensor network on-site. The models showed a wide variation in combined uncertainties, demonstrating the dependence of accurate energy yield predictions on the model and sensing equipment. In particular, it was shown that the application of temperature correction on the single-point efficiency model using the manufacturer provided temperature coefficients (\$\textbackslash gamma\$MPP) resulted in a reduction of the combined uncertainty. In the case of the single-point efficiency model, the uncertainties were in the name-plate efficiency at standard test conditions (\$\textbackslash eta\$STC) and the global irradiation measured on the plane of array (GPOA), producing a combined uncertainty of {$\pm$}7\{\%\} on the annual dc energy yield of all PV systems. By applying temperature correction on the model, the combined uncertainties dropped to an average of {$\pm$}5.60\{\%\}, despite the introduction of additional uncertainties from \$\textbackslash gamma\$MPP and Tmodule. Lastly, the PVUSA model showed even lower combined uncertainties, in the realm of {$\pm$}1.60\{\%\}. The paper also presents the combined uncertainties inherent in the three models separately for four different years (2006-2007, 2007-2008, 2008-2009 and 2009-2010).},
  copyright = {All rights reserved},
  isbn = {978-1-4244-9965-6},
  file = {/home/alexis/Zotero/storage/5XSXJHUS/Makrides et al. - 2011 - Photovoltaic model uncertainties based on field me.pdf}
}

Mathematical and empirical models have long been used to describe the output behaviour of photovoltaic (PV) systems. The purpose of this paper is to compare the combined uncertainties inherent in the results when using three of these models; the single-point efficiency, the single-point efficiency with temperature correction and the PVUSA model. This evaluation was performed using outdoor measurement data from 12 different grid- connected PV systems of 1 kWp each, operating in Cyprus since June 2006 along with measurement data from the meteorological sensor network on-site. The models showed a wide variation in combined uncertainties, demonstrating the dependence of accurate energy yield predictions on the model and sensing equipment. In particular, it was shown that the application of temperature correction on the single-point efficiency model using the manufacturer provided temperature coefficients ($\ gamma$MPP) resulted in a reduction of the combined uncertainty. In the case of the single-point efficiency model, the uncertainties were in the name-plate efficiency at standard test conditions ($\ eta$STC) and the global irradiation measured on the plane of array (GPOA), producing a combined uncertainty of $±$7\%\ on the annual dc energy yield of all PV systems. By applying temperature correction on the model, the combined uncertainties dropped to an average of $±$5.60\%\, despite the introduction of additional uncertainties from $\ gamma$MPP and Tmodule. Lastly, the PVUSA model showed even lower combined uncertainties, in the realm of $±$1.60\%\. The paper also presents the combined uncertainties inherent in the three models separately for four different years (2006-2007, 2007-2008, 2008-2009 and 2009-2010).

@inproceedings{makridesTemperatureThermalAnnealing2011,
  title = {Temperature and Thermal Annealing Effects on Amorphous Silicon {{PV}}},
  booktitle = {26th {{EU-PVSEC}}},
  author = {Makrides, George and Zinsser, Bastian and Phinikarides, Alexander and Schubert, Markus and Georghiou, George E},
  year = {2011},
  pages = {3600--3603},
  address = {{Hamburg, Germany}},
  doi = {10.4229/26thEUPVSEC2011-4AV.2.38},
  abstract = {The effect of temperature on a single-junction a-Si, grid-connected, photovoltaic (PV) system installed in Cyprus was analysed in this study. Initially, the energy yield losses due to temperature were investigated based on acquired measurements of module temperature and using the manufacturer's maximum power point (MPP) temperature coefficients, \$\textbackslash gamma\$PMPP. The same thermal loss investigation was also carried out, using the experimentally evaluated \$\textbackslash gamma\$PMPP coefficients for comparison. In the case of the manufacturer's \$\textbackslash gamma\$PMPP, the results showed that the thermal losses in the annual dc energy yield were 3 - 4 \{\%\}. Similar thermal losses were found when using the experimentally evaluated \$\textbackslash gamma\$PMPP. In addition, temperature effects on the seasonal performance were evident on the monthly average performance ratio (PR) values. An increase in performance from spring until early autumn was observed and was attributed to thermal annealing. The effect of thermal annealing on the performance was revealed by filtering dc MPP power measurements at high irradiance (greater than 800 W/m2) and restricting the values at geometric air mass (AM) in the range 1 {$\leq$} geometric AM {$\leq$} 1.5. The extracted dc MPP power was corrected for irradiance and temperature at standard test conditions (STC) using the manufacturer's \$\textbackslash gamma\$PMPP for a period of two years. The effect of thermal annealing was further investigated by extracting dc MPP power measurements at geometric AM in the range 1.4 {$\leq$} geometric AM {$\leq$} 1.6 in order to minimize the spectral effects on the performance of the a-Si system. The results showed that thermal annealing caused a 7.5 \{\%\} increase in power from March to September 2008 and a 7 \{\%\} increase for the same period in 2009.},
  copyright = {All rights reserved},
  keywords = {amorphous silicon,Grid-connected,Thermal annealing,thermal losses},
  file = {/home/alexis/Zotero/storage/6XX48Z6R/Makrides et al. - 2011 - Temperature and thermal annealing effects on amorp.pdf}
}

The effect of temperature on a single-junction a-Si, grid-connected, photovoltaic (PV) system installed in Cyprus was analysed in this study. Initially, the energy yield losses due to temperature were investigated based on acquired measurements of module temperature and using the manufacturer's maximum power point (MPP) temperature coefficients, $\ gamma$PMPP. The same thermal loss investigation was also carried out, using the experimentally evaluated $\ gamma$PMPP coefficients for comparison. In the case of the manufacturer's $\ gamma$PMPP, the results showed that the thermal losses in the annual dc energy yield were 3 - 4 \%\. Similar thermal losses were found when using the experimentally evaluated $\ gamma$PMPP. In addition, temperature effects on the seasonal performance were evident on the monthly average performance ratio (PR) values. An increase in performance from spring until early autumn was observed and was attributed to thermal annealing. The effect of thermal annealing on the performance was revealed by filtering dc MPP power measurements at high irradiance (greater than 800 W/m2) and restricting the values at geometric air mass (AM) in the range 1 $≤$ geometric AM $≤$ 1.5. The extracted dc MPP power was corrected for irradiance and temperature at standard test conditions (STC) using the manufacturer's $\ gamma$PMPP for a period of two years. The effect of thermal annealing was further investigated by extracting dc MPP power measurements at geometric AM in the range 1.4 $≤$ geometric AM $≤$ 1.6 in order to minimize the spectral effects on the performance of the a-Si system. The results showed that thermal annealing caused a 7.5 \%\ increase in power from March to September 2008 and a 7 \%\ increase for the same period in 2009.

@inproceedings{nortonFieldPerformanceEvaluation2011,
  title = {Field Performance Evaluation and Modelling of Spectrally Tuned Quantum-Well Solar Cells},
  booktitle = {37th {{IEEE PVSC}}},
  author = {Norton, Matthew and Dobbin, Alison and Phinikarides, Alexander and Tibbits, Tom and Georghiou, George E and Chonavel, Sylvain},
  year = {2011},
  pages = {534--537},
  address = {{Seattle, WA}},
  doi = {10.1109/PVSC.2011.6186011},
  abstract = {Monolithic multi-junction solar cells are becoming prevalent in concentrator photovoltaic (CPV) systems due to their high demonstrated conversion efficiencies. However, these devices often operate at sub-optimal levels due to current mismatch losses arising between each p-n junction as a result of natural variation in the solar spectrum at the earth's surface. The use of quantum wells in solar cell design affords improved control over the spectral response of the cells via band-gap engineering. This makes it possible to tailor the spectral response of a cell for optimum performance under a given annual spectral resource. Establishing the optimum spectral response for a given location is a major challenge of this approach to cell design, and relies heavily on averaged and modelled data based on combinations of satellite and sparse ground measurements. In addition, there is only limited field experience of such technology to date. The purpose of this work is to investigate through experiment the effect of incorporating multi-quantum-well (MQW) structures into photovoltaic cells to respond to a specific range of annual irradiation spectra and to compare the results obtained with those predicted through modelling. A number of triple-junction cells of different design have been placed side-by-side on an accurate solar tracker, and current-voltage characteristics of each taken at regular intervals over a few months. The outputs are then compared to those predicted by a model of cell performance that includes simulated spectra, generated with the SMARTS program, specific to that location and period of time. Results obtained from outdoor testing indicate that the cells designed to provide improved current matching under the spectral conditions in which they have been tested have performed more consistently than conventional cell designs. This is evident when the short-circuit current is normalised to a fixed direct normal irradiation and temperature, and plotted against atmospheric depth. Detailed analysis of the spectral resource is expected to reveal additional information on the performance of the cells.},
  copyright = {All rights reserved},
  isbn = {978-1-4244-9965-6},
  file = {/home/alexis/Zotero/storage/9WKKS5U3/Norton et al. - 2011 - Field performance evaluation and modelling of spec.pdf}
}

Monolithic multi-junction solar cells are becoming prevalent in concentrator photovoltaic (CPV) systems due to their high demonstrated conversion efficiencies. However, these devices often operate at sub-optimal levels due to current mismatch losses arising between each p-n junction as a result of natural variation in the solar spectrum at the earth's surface. The use of quantum wells in solar cell design affords improved control over the spectral response of the cells via band-gap engineering. This makes it possible to tailor the spectral response of a cell for optimum performance under a given annual spectral resource. Establishing the optimum spectral response for a given location is a major challenge of this approach to cell design, and relies heavily on averaged and modelled data based on combinations of satellite and sparse ground measurements. In addition, there is only limited field experience of such technology to date. The purpose of this work is to investigate through experiment the effect of incorporating multi-quantum-well (MQW) structures into photovoltaic cells to respond to a specific range of annual irradiation spectra and to compare the results obtained with those predicted through modelling. A number of triple-junction cells of different design have been placed side-by-side on an accurate solar tracker, and current-voltage characteristics of each taken at regular intervals over a few months. The outputs are then compared to those predicted by a model of cell performance that includes simulated spectra, generated with the SMARTS program, specific to that location and period of time. Results obtained from outdoor testing indicate that the cells designed to provide improved current matching under the spectral conditions in which they have been tested have performed more consistently than conventional cell designs. This is evident when the short-circuit current is normalised to a fixed direct normal irradiation and temperature, and plotted against atmospheric depth. Detailed analysis of the spectral resource is expected to reveal additional information on the performance of the cells.

@inproceedings{phinikaridesComprehensiveMethodologyOutdoor2011,
  title = {A Comprehensive Methodology for Outdoor and Indoor Degradation Studies on Photovoltaic Modules},
  booktitle = {3rd {{International Conference}} on {{Renewable Energy Sources}} \& {{Energy Efficiency}}},
  author = {Phinikarides, Alexander and Makrides, George and Georghiou, George E},
  year = {2011},
  pages = {85--93},
  address = {{Nicosia, Cyprus}},
  url = {http://www.mse.com.cy/energy/2011.pdf},
  abstract = {The scope of this paper is to present a methodology for evaluating the performance of photovoltaic (PV) modules installed outdoors on the plane of array (POA) and operating at maximum power point (MPP). The methodology is based on the installation of a 1 kWp, grid- connected photovoltaic system and 2 additional modules of the same make/model on the POA, with the additional modules connected to a computer controlled dc load. The dc load will keep each module operating at MPP, while performing I-V scans at regular intervals. This serves two purposes: a) the modules are operating and degrading as if they were connected to an inverter that keeps them at full load conditions and b) the I-V scans allow for the periodic measurement of the electrical characteristics of the PV modules, all essential in the study of their degradation. The additional modules will be periodically dismounted from the POA and put on a testbed, to acquire the STC (Standard Test Conditions) rating and the dark I-V characteristics, according to the IEC 60904-1 standard. The grid-connected system will serve as the basis for PV performance evaluation and degradation rate determination from a system standpoint. The paper will present important issues arising when comparing the outdoor and indoor measurements. These are: 1) the spectrum utilization, 2) how the time between when a module is dismounted from the POA and tested under the solar simulator can affect the internal stability of the module, 3) the I-V scanning sweep rate and, 4) the duration of the light pulses of the solar simulator and how the measured Pmax, with mismatch factor (MMF) corrections as described in standard IEC 60904-7, compares to the outdoor measurements of the PV technologies.},
  copyright = {All rights reserved},
  keywords = {degradation,field,indoor,photovoltaic,spectrum,testing,thin-film},
  file = {/home/alexis/Zotero/storage/B4C7PVCK/Phinikarides et al. - 2011 - A comprehensive methodology for outdoor and indoor.pdf}
}

The scope of this paper is to present a methodology for evaluating the performance of photovoltaic (PV) modules installed outdoors on the plane of array (POA) and operating at maximum power point (MPP). The methodology is based on the installation of a 1 kWp, grid- connected photovoltaic system and 2 additional modules of the same make/model on the POA, with the additional modules connected to a computer controlled dc load. The dc load will keep each module operating at MPP, while performing I-V scans at regular intervals. This serves two purposes: a) the modules are operating and degrading as if they were connected to an inverter that keeps them at full load conditions and b) the I-V scans allow for the periodic measurement of the electrical characteristics of the PV modules, all essential in the study of their degradation. The additional modules will be periodically dismounted from the POA and put on a testbed, to acquire the STC (Standard Test Conditions) rating and the dark I-V characteristics, according to the IEC 60904-1 standard. The grid-connected system will serve as the basis for PV performance evaluation and degradation rate determination from a system standpoint. The paper will present important issues arising when comparing the outdoor and indoor measurements. These are: 1) the spectrum utilization, 2) how the time between when a module is dismounted from the POA and tested under the solar simulator can affect the internal stability of the module, 3) the I-V scanning sweep rate and, 4) the duration of the light pulses of the solar simulator and how the measured Pmax, with mismatch factor (MMF) corrections as described in standard IEC 60904-7, compares to the outdoor measurements of the PV technologies.

@phdthesis{phinikaridesImprovingCascodeAnaloguetodigital2008,
  type = {{{MSc}} Dissertation},
  title = {Improving the Cascode Analogue-to-Digital Converter Using Switched-Current Techniques},
  author = {Phinikarides, Alexander},
  year = {2008},
  month = sep,
  address = {{Southampton, United Kingdom}},
  abstract = {This dissertation presents the work done for improving the cascode analogue-to-digital converter by using switched-current techniques. Various current copier cells and their effects on the copied current were investigated. This included techniques for reducing the error caused by charge injection, large current inputs and low output resistance. The result of the investigation was that active current copier cells offered the best performance by solving the low output resistance problem and that capacitors added in parallel to the gate and source of the memory transistor solved the problem of large input currents. The converter was redesigned with active current copier cells which were used to replicate the operation of the original cascode ADC. The same technology with the original cascode ADC was used (Mietec 2.4{$\mu$}m). Simulations done in HSpice have shown that the converter is operating correctly and has decreased the conversion errors by more than 200\%, up to the last stage, when the current is fed into the current comparator. The comparator was kept the same as the original cascode ADC and could not be adapted for use in the new circuit. The error was reduced to less than half though, which proves that this type of converter has potential. The simulations have also shown that the switched-current ADC had a maximum power consumption of 1.45mW /bit, which is less than half the consumption of the original cascode ADC (3mW /bit).},
  copyright = {All rights reserved},
  langid = {english},
  school = {University of Southampton},
  file = {/home/alexis/Zotero/storage/9A35XG23/Phinikarides - 2008 - Improving the cascode analogue-to-digital converte.pdf}
}

This dissertation presents the work done for improving the cascode analogue-to-digital converter by using switched-current techniques. Various current copier cells and their effects on the copied current were investigated. This included techniques for reducing the error caused by charge injection, large current inputs and low output resistance. The result of the investigation was that active current copier cells offered the best performance by solving the low output resistance problem and that capacitors added in parallel to the gate and source of the memory transistor solved the problem of large input currents. The converter was redesigned with active current copier cells which were used to replicate the operation of the original cascode ADC. The same technology with the original cascode ADC was used (Mietec 2.4$μ$m). Simulations done in HSpice have shown that the converter is operating correctly and has decreased the conversion errors by more than 200%, up to the last stage, when the current is fed into the current comparator. The comparator was kept the same as the original cascode ADC and could not be adapted for use in the new circuit. The error was reduced to less than half though, which proves that this type of converter has potential. The simulations have also shown that the switched-current ADC had a maximum power consumption of 1.45mW /bit, which is less than half the consumption of the original cascode ADC (3mW /bit).

@phdthesis{phinikaridesDesignImplementationStandalone2007,
  type = {{{BSc}} Dissertation},
  title = {The Design and Implementation of a Stand-Alone Photovoltaic System with Data Logging and Remote Monitoring via the Internet},
  author = {Phinikarides, Alexander},
  year = {2007},
  month = may,
  address = {{Nicosia, Cyprus}},
  abstract = {The purpose of this project was the design and implementation of a stand-alone photovoltaic system used for powering a 40W conventional AC incandescent lamp for 4 hours during the night, with DC voltage and current measurements, from the photovoltaic panel, recorded and stored in a database. The measurements were made remotely available via a dynamic web site, able to display real-time data and construct graphs of voltage, current and power over time for a specified time interval. The major aspect of this project was the installation of the photovoltaic and data acquisition subsystems and subsequently, the real operation of the system. The installation took place at the University of Cyprus' Photovoltaic Park, using photovoltaic components and wires whose specifications have been calculated to comply with the project's specifications and the 16th edition of the IEE Wiring Regulations in the design part of this project. The actual operation of the system has been recorded and the design has been verified. This process was made easier by observing the measurements taken by the data acquisition system and comparing them with the theoretical values. In addition to the design and implementation of the project, this dissertation provides an insight on the status of the photovoltaic market in Cyprus.},
  copyright = {All rights reserved},
  langid = {english},
  school = {University of Cyprus},
  file = {/home/alexis/Zotero/storage/WLCGGDZE/Phinikarides - 2007 - The design and implementation of a stand-alone pho.pdf}
}

The purpose of this project was the design and implementation of a stand-alone photovoltaic system used for powering a 40W conventional AC incandescent lamp for 4 hours during the night, with DC voltage and current measurements, from the photovoltaic panel, recorded and stored in a database. The measurements were made remotely available via a dynamic web site, able to display real-time data and construct graphs of voltage, current and power over time for a specified time interval. The major aspect of this project was the installation of the photovoltaic and data acquisition subsystems and subsequently, the real operation of the system. The installation took place at the University of Cyprus' Photovoltaic Park, using photovoltaic components and wires whose specifications have been calculated to comply with the project's specifications and the 16th edition of the IEE Wiring Regulations in the design part of this project. The actual operation of the system has been recorded and the design has been verified. This process was made easier by observing the measurements taken by the data acquisition system and comparing them with the theoretical values. In addition to the design and implementation of the project, this dissertation provides an insight on the status of the photovoltaic market in Cyprus.