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Introduction
Education
January 2010 - June 2017
September 2007 - September 2008
September 2003 - June 2007
Publications
Publications (42)
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...
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 s...
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 measu...
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....
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 o...
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. Keywords-rural 5G, satellite/5G integration, edge computing I. OVERVIEW One of the ambitions of 5G-and beyond-...
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...
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 pro...
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....
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....
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 pro...
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...
The scope of this paper is to present the development of failure detection routines (FDRs) that will operate on acquired data sets of grid-connected PV systems and determine and classify accurately the exhibited failures. The developed FDRs comprise of a failure detection and a classification stage. Specifically, the implemented failure detection s...
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 missi...
Degradation rates based on forecasting of performance ratio, Rp, time series are computed
and compared with actual degradation rates. A three year forecasting of monthly Rp, measured
from PV connected systems of various technologies is performed using the seasonal ARIMA
(SARIMA) time series model. The seasonal ARIMA model is estimated using monthly...
Poster presented at the 2017 NREL/SNL/BNL Photovoltaic Reliability Workshops 2017.
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 s...
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 monitorin...
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 e...
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 identification and classification of faults. pvpaR's ecosystem is based on the R statistical computing project, both for the back-...
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...
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 outd...
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 unc...
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...
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...
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 inclu...
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 mo...
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 poin...
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 f...
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 eart...
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. Th...
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...
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, γP...