A Building-Integrated Bifacial and Transparent PV Generator Operated by an “Under-Glass” Single Axis Solar Tracker

Nearly Zero Energy Buildings (NZEBs) play a key role in the world energy transition. This is motivating the scientific community to develop innovative electrical and thermal systems characterized by very high efficiency to specifically address the energy needs of modern buildings. Naturally, the integration of the latest generation photovoltaic (PV) systems into buildings helps to satisfy this need, and, with this objective in mind, an innovative and highly efficient building-integrated photovoltaic (BIPV) system is presented and discussed in this paper. The proposed PV system is purpose-built to be fully integrated into a variety of buildings (preferably into their rooftops) and assumes the form of a PV skylight. It is based on a certain number of innovative rotating bifacial PV modules, which are specifically made to be installed "under-glass" within a custom-made transparent casing. Thanks to their properties, the PV modules can be rotated using a very low-power, reliable, and efficient mono-axial solar tracking system, fully protected against adverse atmospheric agents. Once the proposed PV skylight is fully integrated into a building, it generates electricity and, additionally, helps to improve both the energy performance and the aesthetic appearance of the building. The electricity generation and illuminance performances of the proposed PV skylight are experimentally tested using a low-power homemade prototype driven by different solar tracking logics and under different operating conditions; the most relevant results are summarized and extensively discussed. The main outcome of the experimental study is that the most effective performance of the PV skylight is obtained by installing, in its available surface, the maximum possible number of rotating bifacial PV modules, side by side and with no empty spaces between them.