No abstract

In this paper we report on research activities at the Fraunhofer Institute for Solar Energy Systems (ISE) and Concentrix Solar in the area of secondary optics for FLATCON ® modules. This concentrator photovoltaic (CPV) technology is based on Fresnel-lenses as primary optics, passive heat spreaders and triple-junction III-V solar cells. In the first part of the paper, a field performance analysis is presented for Concentrix CPVsystems recently installed in Spain. Subsequently, the performance of the first FLATCON ® modules with reflective and refractive secondaries are evaluated (FLATCON ® II) in indoor and outdoor measurements. As a result of this development, the first module with automated assembly process of the secondary optics could be manufactured. The highest outdoor efficiency measured for this kind of module is 29.1 %, which is the highest module efficiency achieved at the Fraunhofer ISE so far.

This paper reports on the development of secondary optics for concentrator photovoltaic (CPV) modules. It focuses on reflective secondary optics designed for high concentration modules using fresnel lenses as the primary concentrating optics. The development of the secondary optics was guided by the idea of designing an optical element suitable for cost effective mass production. The primary concentrating optics of a CPV module can direct only a limited part of the solar aureole (the immediate surroundings of the sun) onto the solar cell. The same applies to light impinging non-perpendicular to the optical axis of the module (e.g., due to misalignment of the module). Therefore, one of the main functions of reflective secondary optics is to redirect light onto the solar cell that would otherwise not reach it. In order to analyze the performance of secondary optical elements ("secondaries"), a measurement setup is introduced that measures the angular photocurrent response of a CPV device with highly parallel light. This response is referred to as the "angular acceptance function" (AAF). The AAF is used to estimate the performance of the CPV device under various conditions with differing circumsolar radiation (CSR). A CPV test module was manufactured featuring III-V triple-junction solar cells, a fresnel lens panel as the primary concentrator optic, and the newly developed reflective secondary. The results of a 6-month outdoor measurement period are presented and compared to the performance of a reference module as well as to the results of the indoor AAF measurements

Solar cells used in photovoltaic (PV) crystalline silicon modules commonly feature grid fingers and bus bars as front contacts. The grid fingers and bus bars partially block the sunlight from reaching the semiconductor layers of a solar cell and therefore reduce the efficiency of a solar module. In this paper, we present experimental results of different technologies to reduce the shadowing effect that bus bars and grid fingers impose. We focus on two technologies that can be easily integrated into standard PV module technology and help to increase the module's efficiency. In the first technology, a laser is used to create a scattering pattern on the front glass of the module. This pattern directs light away from the bus bars and grid fingers. In the second technology, the bus wires are coated with a diffuse reflective coating. The sunlight is diffusely reflected at this coating. A part of it is reflected at such angles that internal reflection at the front surface of t he cover glass occurs. From there the light is reflected back to the solar cell and contributes to the generated photocurrent

No abstract