Development and study of a dense array Concentration PhotoVoltaic (CPV) system

In the past several years there has been a growing commercial interest in Concentration PhotoVoltaics (CPV) thanks to its promise of low cost electrical power generation. While the technology of CPV using point-focus Fresnel-like optical elements is reaching maturity, the systems based on dense array receivers still need further scientific progress. This thesis explores the field of CPV applied to a parabolic concentrator prototype and to a dense array receiver made of multijunction solar cells. The solar concentrator, completely designed and built at the University of Trento, is characterized, in order to get the illumination distribution on the PV receiver. The non-uniformity in incident flux results in a current mismatch among cells and strongly impacts the system performance. In order to solve this issue, we have proposed a new type of electrical connection by fitting each cell of the array with an individual DC-DC converter. This method is shown to increase the power transfer efficiency with respect to classical series connection, at least for the tested illumination levels and unbalances. The other main problem with dense array systems is the reliability of the PV receiver, with special attention to the high thermal flux to be dissipated. Several types of water-cooled receivers have been built, with different material configurations that were previously studied with 3D thermal modeling. In particular the building of a multi-cell receiver has required the design of the insulation/interconnection between the cells, the tuning of the cell soldering and the realization of front contact connections.