Measurements of the Electrical Incidence Angle Modifiers of an Asymmetrical Photovoltaic/Thermal Compound Parabolic Concentrating-Collector

Reflector edges, sharp acceptance angles and by-pass diodes introduce large variations in the electrical performance of asymmetrical concentrating photovoltaic/thermal modules over a short incidence angle interval. It is therefore important to quantify these impacts precisely. The impact on the electrical performance of the optical properties of an asymmetrical photovoltaic/thermal CPC-collector was measured in Maputo, Mozambique. The measurements were carried out with the focus on attaining a high resolution incidence angle modifier in both the longitudinal and transversal directions, since large variations were expected over small angle intervals. A detailed analysis of the contribution of the diffuse radiation to the total output was also carried out. The solar cells have an electrical efficiency of 18% while the maximum measured electrical efficiency of the collector was 13.9 % per active glazed area and 20.9 % per active cell area, at 25 °C. Such data make it possible to quantify not only the electrical performance for different climatic and operating conditions but also to determine potential improvements to the collector design. The electrical output can be increased by a number of different measures, e.g. removing the outermost cells, turning the edge cells 90°, dividing each receiver side into three or four parts and directing the tracking, when used, along a north-south axis.

Construction of a Small Scale Laboratory for Solar Collectors and Solar Cells in a Developing Country

In the field of renewable energy, self-provided research in developing countries is barely present, but most welcomed. The creation of know-how and self-development of technologies should reduce the dependence on industrialized countries for both materials and knowledge. This work presents technological and social issues related to the construction of a low budget solar laboratory in Mozambique. The goal is to demonstrate that scientific level research can be carried out in developing countries by using affordable solutions without sacrificing quality of the results. For this investigation, a solar laboratory was built in 2011 at Universidade Eduardo Mondlane of Maputo. The laboratory enables measurements?to evaluate solar?thermal and?photovoltaic-thermal?hybrid collectors.?Thanks to the?flexibility of the system,?students and teaching staff can?add/remove equipment and develop customised local research programs. In addition, a course on the principles of solar energy and collector simulation for local students was taught. The needed data acquisition devices usually used in Europe were compared with cheaper and easy-maintenance ones. Calibration and estimation of the uncertainty were successfully performed. Approximately 9% of inaccuracy in the measurement was introduced by the cheaper equipment, but the investment cost was reduced by more than 90%. Other issues, results and future recommendations are shown.

Testing Bifacial PV Cells in Symmetric and Asymmetric Concentrating CPC Collectors

Bifacial PV cells have the capacity to produce solar electricity from both sides and, thus, amongst other advantages, allow a significantly increase both in peak and annual power output while utilizing the same amount of silicone. According to the manufacturer, the bifacial cells are around 1.3 times more expensive than the single-sided cells. This way, bifacial PV cells can effectively reduce the cost of solar power for certain applications. Today, the most common application for these cells is in stationary vertical collectors which are exposed to sunlight from both sides, as the relative position of the sun changes throughout the day. Another possible application is to utilize these cells in concentrating collectors. Three test prototypes utilizing bifacial PV cells were built. The initial two prototypes were built for indoor testing and differed only in geometry of the reflector, one being asymmetric and the other symmetric. Both prototypes were evaluated in an indoor solar simulator. Both reflector designs yielded positive electrical performance results and similar efficiencies from both sides of the cell were achieved. However, lower fill factor than expected was achieved for both designs when compared to the single cell tests. The results are discussed and suggestions for further testing are presented. A third prototype was built in order to perform outdoor evaluations. This prototype utilized a bifacial PV cells string laminated in silicone enclosed between 2 standard glass panes and a collector box with an asymmetric CPC concentrator. The prototype peak electrical efficiency and temperature dependence were evaluated. A comparison between the performance of the bottom and top sides of the asymmetric collector is also presented. Additionally, the incidence modifier angle (IAM) is also briefly discussed.