Raffaele Fucci

A procedure for assessing the reliability of short circuited concentration photovoltaic systems in outdoor degradation conditions

Abstract A procedure for assessing the reliability functions of photovoltaic concentration (CPV) systems, subjected to outdoor degradation, will be described in this work. The evaluation of the concentrator cells failure rate, the understanding of the origin of these degradation modes and how they affect the performances of concentration cells is an essential step to improve their reliability and to accelerate their competitiveness. The reliability evaluation methodology introduced here, as the cells are deployed outdoors and then are subjected to the actual sources of stress (e.g. ambient temperature, solar concentrated irradiance, cells working temperature and the variations of these parameters over days and seasons), will furnish values of failure rates very close to the true ones.

Results of the Fifth International Spectroradiometer Comparison for Improved Solar Spectral Irradiance Measurements and Related Impact on Reference Solar Cell Calibration

This paper reports on the results of the fifth spectral irradiance measurement intercomparison and the impact these results have on the spread of spectral mismatch calculations in the outdoor characterization of reference solar cell and photovoltaic (PV) devices. Ten laboratories and commercial partners with their own instruments were involved in the comparison. Solar spectral irradiance in clear sky condition was measured with both fast fixed and slow rotating grating spectroradiometers. This paper describes the intercomparison campaign, describes different statistical analysis used on acquired data, reports on the results, and analyzes the impact these results would have on the primary calibration of a c-Si PV reference cell under natural sunlight.

Induced degradation on c-Si solar cells for concentration terrestrial applications

Abstract There are several factors that can affect the reliability of concentration solar cells and influence the final devices performances. Electrical characterizations like the dark I – V curve in reverse and forward bias, the I – V curve under illumination and the quantum efficiency are generally used to test the stability of the cells. For this reason also in the packaging processes, used for making external connections, great attention is devoted to guarantee maximum reliability versus thermally induced expansions, contractions and/or stresses which might cause a degradation of the device performance. After the observation of the effects due to the packaging process of ENEA c-Si concentration solar cells, we analyze the attitude of the completely “packed” device to dissipate heat as compared to a commercial c-Si back contact concentration solar cell. Then we propose accelerated degradation tests to study, through electrical characterizations, the reliability of ENEA solar cell against high light intensities and humidity. In particular, for both ENEA and commercial devices the effects of each considered degradation mechanism on final behavior will be reported.

Characterization and validation tests on Ecosole C-modules first prototypes

ECOSOLE is an European collaborative Project started in August 2012 that involves several industrial and institutional partners with the aim to develop a complete and innovative concentrating photovoltaic system. During the first two years of activity, several specific components as cells, optics, modules and tracker have been designed and developed. This work reports the description of these devices and the main results of the characterization campaigns carried out to define their technical features.

Rating of CPV modules: Results of module round robins

The results of three CPV module round robins are presented. Ten test labs around the world participated to the round robins in total. Each round robin used a different CPV module technology (Daido Steel, Soitec, Suncore). The data gathered at the test labs was used to test CSOC power rating procedures as basis for the IEC draft standard 62670-3. The deviation between the minimum and the maximum power output rated at the test labs was in average 4.4 % with a standard deviation of 1.8 %abs. This underlines that power ratings or CPV modules are reliable and reproducible.

Indoor-outdoor measurement inter-comparison of c-Si concentrating photovoltaic cells at 1X to 300X

In this work the authors show results of a measurement inter-comparison campaign that saw the cooperation of the University of Applied Sciences and Arts of Southern Switzerland (SUPSI-ISAAC, indoor characterization), the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA, outdoor characterization) and the University of Cyprus (indoor and outdoor characterization). The measurement campaign is extremely useful to improve the know-how of the centres involved. Aside the well-known spectral mismatch effects, the importance of the “capacitive effect” is highlighted in this work, which arises when the tested high-efficiency CPV cell are characterized indoor on a pulsed solar simulator, depending on the duration of the pulse.

ENEA's activities on C-PV technology

ENEA, Italian Agency for new technologies, energy and sustainable development, has been involved in the Concentration-PhotoVoltaic (C-PV) technology for many years. The activities started in 2002 within the PhoCUS (Photovoltaic Concentrators Utility Scale) project. Now ENEA is involved in European (APOLLON - Multi Approach for high efficiency integrated and intelligent concentrating PV modules Systems) and National (SCOOP - Italian Solar Concentration technologies for Photovoltaic systems) projects. In this paper the main results achieved by ENEA in the C-PV technology will be presented.

Analysis of Ecosole HCPV system performances during two operation years

This paper reports the results of a performance analysis carried out by ENEA on a CPV system, produced by BECAR srl within a European collaborative Project named ECOSOLE, and installed at ENEA Research Center of Portici. Modules degradation after two operation years has been evaluated by means of detailed characterizations; tracker system accuracy has been monitored using a specific opto-electronic device. System performances during the period has been analysed based on the production and weather data: a deep performance analysis has been carried out in order to quantify the main losses causes in DC side. The behaviours of the two sub-fields of the system, the first one realized with one centralized inverter for 16 modules and the second one with 16 modules having each one its own inverter, have been compared from technical and economical point of view.

Set of protocols for overall testing for CPV

The success of a new CPV prototype depends on modules quality and assembly compliance with existing Standards, such as IEC 62108, 62670, 62787, and others still under development/approval for performance evaluation. The overall CPV system reliability is based on the quality of the subcomponents such as the optics, the cells, the electronics and the assembly of the whole system, but there is a dramatic lack of technical specifications for new prototypes to comply with. The Italian project SCOOP (SOLAR CONCENTRATION TECHNOLOGIES FOR PHOTOVOLTAIC SYSTEMS) was aimed at developing an Italian network of laboratories and industrial facilities to enter the CPV market. The project, funded by the Ministry of Industry, started in 2009 and ended at the end of 2013. SCOOP addressed the development of solar cells, optical systems and inverters, to be used in four different CPV prototypes. The development of a network of laboratories specialized to test, verify and check components such as plastic materials, optics, cells, electronics and module/assembly at prototype and industrial scale has been one of the main targets of the project. Within the project a set of protocols for the testing of subcomponents, components, modules and the final systems have been defined and validated.