Domenico Chianese

Energy rating of PV modules: comparison of methods and approach

The Matrix and Performance Surface Methods of Energy Rating are related techniques under development for the determination of electrical yield that is intended to be a more useful predictor of performance for installers than Wp alone. Here a power matrix or performance surface as a function of irradiance and ambient temperature P(Gi; Ta) is linked to a climatic condition occurrence matrix N(Gi, Ta) for a particular location. The use of just two independent variables has the advantage of simplicity but it is important to evaluate the possible cost of reduced accuracy due to the exclusion of other variable parameters such as Air Mass for example. The power matrix may be determined by outdoor or indoor measurements, and the complete matrix may also be extrapolated from a reduced data set using models of cell behaviour thereby reducing measurement time. The present paper relates solely to crystalline Si and reports on the comparison of outdoor measurements at two sites, and their further comparison with indoor measurements.

The Effects of Solar Cell Capacitance on Calibration Accuracy When using a Flash Simulator

A model for investigating the dynamic behaviour of solar cells, which allows the simulation of the measurements process with flash solar simulators, is presented in this paper. This model is then applied to the simulation of measurement processes currently employed by common solar simulator types. It is shown that the cell capacitance, the series resistance and cell area can all influence the measurements, giving rise to transient errors, especially in short flash solar simulators. It is also shown that point distribution as well as scan time also has significant importance

Photovoltaic Performance Measurements in Europe: PV-Catapult Round Robin Tests

Two sets of modules have been sent around to different testing installations across Europe, one set to laboratories performing indoor calibrations and one set to laboratories performing outdoor power and energy ratings. The results show that for crystalline and poly-crystalline devices, a very good agreement between laboratories has been achieved. A lower agreement between laboratories has been achieved for thin film devices and further need for research is identified

Fast and accurate methods for the performance testing of highly-efficient c-Si photovoltaic modules using a 10 ms single-pulse solar simulator and customized voltage profiles

Performance testing of highly efficient, highly capacitive c-Si modules with pulsed solar simulators requires particular care. These devices in fact usually require a steady-state solar simulator or pulse durations longer than 100?200?ms in order to avoid measurement artifacts. The aim of this work was to validate an alternative method for the testing of highly capacitive c-Si modules using a 10?ms single pulse solar simulator. Our approach attempts to reconstruct a quasi-steady-state I?V (current?voltage) curve of a highly capacitive device during one single 10?ms flash by applying customized voltage profiles?-in place of a conventional V ramp?to the terminals of the device under test. The most promising results were obtained by using V profiles which we name ?dragon-back? (DB) profiles. When compared to the reference I?V measurement (obtained by using a multi-flash approach with approximately 20 flashes), the DB V profile method provides excellent results with differences in the estimation of Pmax?(as well as of Isc, Voc?and FF) below ?0.5%. For the testing of highly capacitive devices the method is accurate, fast (two flashes?possibly one?required), cost-effective and has proven its validity with several technologies making it particularly interesting for in-line testing.

Accuracy of Energy Prediction Methodologies

In the current market, the specific annual energy yield (kWh/kWp) of a PV system is gaining in importance due to its direct link to the financial returns for possible investors who typically demand an accuracy of 5% in this prediction. This paper focuses on the energy prediction of photovoltaic modules themselves, as there have been significant advances achieved with module technologies which affect the device physics in a way that might force the revisiting of device modelling. The paper reports the results of a round robin based evaluation of European modelling methodologies. The results indicate that the error in predicting energy yield for the same module at different locations was within 5% for most of the methodologies. However, this error increased significantly if the nominal nameplate rating is used in the characterization stage. For similar modules at the same location the uncertainties were much larger due to module-module variations

A fast and accurate method for the performance testing of high-efficiency C-Si photovoltaic modules using A 10 Ms single-pulse solar simulator

Performance testing of high-efficient, highly-capacitive c-Si modules with pulsed solar simulators requires particular carefulness in order to avoid measurement artifacts. These devices in fact usually require a steady-state solar simulator or pulse durations longer than 100 ms. The aim of this work was to validate an alternative method for the testing of highly capacitive c-Si modules using a 10-ms single pulse solar simulator. Our approach attempts to reconstruct a quasi steady-state IV curve of a highly-capacitive device during one single 10-ms flash by applying customized voltage profiles - in place of a conventional V ramp - to the terminals of the device under test. The most promising results were obtained by using V profiles which we name “dragon-back” (DB) profiles. When compared to the reference IV measurement (obtained by using a multi-flash approach), the dragon-back V profile method provides excellent results with differences in the estimation of Pmax below ±0.5% (as well as of Isc, Voc, and FF). For the testing of highly-capacitive devices the method is accurate, fast (two flashes - possibly one - required), and cost-effective.

Thermal Isolated BIPV Design Matched to A-Si Modules Behaviours

In BIPV design with c-Si cells, ventilation is important in order to keep cells as cool as possible. To allow a good ventilation it is therefore generally preferred to mount the modules separated from the existing roof. In the case of sloped roofs the modules are superimposed to the existing roof and for flat roofs separated tilted mounting structures with wind loads are used instead, but both are no real building integrations. In this paper we analyse the behaviour and the energy yield of a 15.36 kWp PV system based on flexible triple-junction thin-film amorphous silicon modules laminated together with a single ply roofing system based on a flexible polyolefine (FPO) membrane which acts as a waterproofing system. Compared to c-Si modules, a thermal isolated BIPV design matches the best the thermal behaviour of a-Si technologies

High-speed multi-channel system for solar simulator irradiance non-uniformity measurement

We present a new tool for the measurement of the non-uniformity of a large-area pulsed solar simulator according to IEC 60904-9. We realized a prototype portable unit that can be controlled via a single USB port of a notebook. The system is composed by several photovoltaic cells and a series of custom designed electronic boards, allowing a high-speed multi-channel sampling of a single pulse. We describe the main components and the design solution, which is using readily available standard electronic and software components, allowing a possible industrialization of the system. Finally we present preliminary results of the prototype unit testing.