Thermal analysis of a BIPV system by various modelling approaches

This work presents various models developed and implemented within the SOPHIA European project in order to thermally characterize PV modules in a rooftop BIPV configuration. Different approaches have been considered, including a linear model, lumped elements models and models that make use of commercial software solvers. The validation of the models performed by comparing the results of simulations with experimental data recorded on a test bench over an entire year is presented and discussed on a seasonal basis. The results have shown that all the models implemented allow achieving a good prediction of the PV modules back surface temperature, with the minimum value of the coefficient of determination R2 around 95% on a yearly basis. Moreover, the influence of season weather conditions and of the incident solar irradiance magnitude on the accuracy of the considered thermal models is highlighted. The major result of the present study is represented by the fact that it has been possible to perform a better thermal characterization of the BIPV module by tuning some of the heat transfer coefficients, such as those relative to the effects of the wind velocity, and to the evaluation of sky temperature.The experimental data used for the thermal simulation of BIPV system behavior were obtained in the framework of the project Performance BIPV supported by the French research agency (ANR), within the research program ANR HABISOL. Authors would like to thank the European Community that supported the SOPHIA project with the funding of FP7-SOPHIA grant agreement no. 262533

Changes of solar cell parameters during damp-heat exposure

The electrical ageing of photovoltaic modules during extended damp-heat tests at different stress levels is investigated for three types of crystalline silicon photovoltaic modules with different backsheets, encapsulants and cell types. Deploying different stress levels allows determination of an equivalent stress dose function, which is a first step towards a lifetime prediction of devices. The derived humidity dose is used to characterise the degradation of power as well as that of the solar cell's equivalent circuit parameters calculated from measured current–voltage characteristics. An application of this to the samples demonstrates different modes in the degradation and thus enables better understanding of the module's underlying ageing mechanisms. The analysis of changes in the solar cell equivalent circuit parameters identified the primary contributors to the power degradation and distinguished the potential ageing mechanism for each types of module investigated in this paper. © 2016 The Authors. Progress in Photovoltaics: Research and Applications published by John Wiley & Sons Ltd. © 2016 The Authors. Progress in Photovoltaics: Research and Applications published by John Wiley & Sons Ltd.This work was supported in part by the European Commission under FP7 grant N° 262533 SOPHIA (INFRA-2010- 1.1.22_CP-CSA-Infra) and by the Research Councils UK (RCUK) under project ‘Stability and Performance of Photovoltaics (STAPP)’ (contract no: EP/H040331/1)

Changes of solar cell parameters during damp-heat exposure

The degradation of PV modules during damp-heat exposure is investigated. Power degradation is analysed in dependence of temperature and humidity during exposure. The module’s equivalent circuit parameters are calculated from I-V characteristics measured during ageing. A dose function is developed and degradations of power as well as equivalent circuit parameters can be analysed against the dose, which provides a better understanding of the module ageing behaviour. EL images of modules before and after ageing support the changes of solar cell parameters

Results of the Sophia module intercomparison part-1: stc, low irradiance conditions and temperature coefficients measurements of C-Si technologies

The results of a measurement intercomparison between eleven European laboratories measuring PV energy relevant parameters are reported. The purpose of the round-robin was to assess the uncertainty analyses of the participating laboratories on c-Si modules and to establish a baseline for the following thin-film round-robin. Alongside the STC measurements, low irradiance conditions (200W/m2) and temperature coefficients measurements were performed. The largest measurement deviation from the median at STC was for HIT modules from -3.6% to +2.7% in PMAX, but in agreement with the stated uncertainties of the participants. This was not the case for low irradiance conditions and temperature coefficients measurements with some partners underestimating their uncertainties. Larger deviations from the median from -5% to +3% in PMAX at low irradiance conditions and -6.6% to +18.3% for the PMAX temperature coefficient were observed. The main sources of uncertainties contributing to the spread in measurements were the RC calibration, mismatch factor and capacitive effects at STC and low irradiance conditions as well as the additional light inhomogeneity for the latter. The uncertainty in the junction temperature and the temperature deviation across the module were the major contributors for temperature coefficients measurements

Uncertainty in energy yield estimation based on C-Si module roundrobin results.

Results of the European FP7 Sophia project roundrobin of c-Si module power measurements at STC and low irradiance and temperature coefficients were used to calculate annual energy yield at four sites. The deviation in the estimates solely due to the different measurement results is reported, neglecting the uncertainty in the meteorological data and losses unrelated to the performed measurements. While minimising the deviation in Pmax measurements remains the key challenge, the low irradiance and temperature coefficient contributions are shown to be significant. Propagating the measurement deviation in c-Si module measurements would suggest that expanded uncertainty in energy yield due to module characterization alone can be as high as ±3-4%

Quantifying Environmental Effects for Different Device Technologies Based on Proposed Energy Rating Standard

The most common parameter for comparison of photovoltaic (PV) modules is the output power at Standard Test Conditions (STC), which is a static set of test conditions which is reproducible under laboratory conditions but not necessarily a good indicator of operating performance in the field. Profitability of PV-systems has become more important and consequently the energy production or energy rating of modules. Therefore an easy to use energy comparator is required for industry, installers and customers. A method for the determination of module energy was proposed in the draft standard IEC 61853, which currently is under discussion. This paper investigates the importance of the different measurements suggested in the original draft on the absolute energy yield for three module technologies, thus providing a sensitivity analysis of the expected modelling accuracy.JRC.H.8-Renewable energie

A database for positive energy districts (PED)

The development of Positive Energy Districts (PEDs) is a complex process that involves the integration of various technologies, stakeholders, and policies. To facilitate this process, a database for PEDs has been developed as a joint effort of COST Action ‘PED-EU-NET’, IEA EBC Annex 83, and JPI Urban Europe. This paper reports on the realization of the PED-Database framework and its online implementation as a modular web interoperable platform, giving details on the development life cycle since the scoping phase up to the testing phase. The PED-Database offers a variety of implementation strategies and conceptualizations for the PED concept, making it a valuable resource for urban planners, policymakers, and researchers. The testing phase has shown that there is no one-fits-all solution for PED implementation, and the overall PED framework definitions require further detailing in the local context. However, the database allows users to visualize and compare different PED scenarios by customizing their selection, accessing to the information provided by real PED cases that best meets their expectations and goals. Overall, the PED-Database provides a valuable tool for the development of sustainable and energy-efficient urban areas

PV Module Output Power Characterisation in Test Laboratories and in the PV Industry - Results of the European Performance Project

The EC-funded Integrated Project PERFORMANCE1 completed in December 2009 included a sub-project on the Traceable Performance Measurements of PV Devices devoted to improving the comparability of PV module power measurements between European test laboratories. The aim of the research work was to fill existing gaps of knowledge for defining specific measurement procedures for various PV technologies, to translate research results into best practice guidelines for PV industry and to provide input for standardisation working groups. To this end, various round-robin tests were conducted among test laboratories covering the range of commercially available crystalline silicon and thin-film PV modules. This paper presents the final results of our research work. It focuses on the progress achieved for PV module output power characterisation, but also sketches measurement problems remaining to be solved.JRC.DDG.F.8-Renewable Energy (Ispra

Validation of proposed photovoltaic energy rating standard and sensitivity

PV devices are currently compared on the basis of the power measurements, which might not be as meaningful as a comparator as the energy yield. The energy rating standard proposed by the IEC promises to overcome this shortcoming. It has been implemented in three institutes and the issues with the current drafts are evaluated. The data required as the input for the energy rating is normally not available and synthetic datasets will have to be used or parts need to be estimated for validation studies. The validation against outdoor data shows that the uncertainty of the input data, specifically the angular distribution of the diffuse irradiance, makes the energy prediction part virtually not applicable for energy yield calculations. The validation effort shows a reduction of the standard deviation in the measurements, indicating that all environmental effects are considered. The evaluation of the originally proposed standard days shows that there is little information to be gained in their application as they are not representative of realistic conditions; they are enveloping the possible environments. This will in some cases over-emphasise the importance of certain effects, as their contribution to the overall energy yield might be negligible. Overall, the proposed standard represents an important advance on power rating. The standard is able to identify differences in device technologies. Further work might be required to make the output more relevant to a wider variety of users, though