In Fig. 4, it is possible to comprehend the performance of a PVT hybrid system when it comes to thermal and electrical outputs interaction. As it is represented, when an electric load is connected to the electric circuit, electric power can be extracted. This means that part of the incoming irradiation is transformed into electricity by the PV cells instead of being absorbed by the thermal receiver. Hence, the thermal output decreases as much as the electrical output is extracted.

3.2. Reflector optical accuracy and design

Given that the measured system electrical efficiency (8.3% at 25°C) is significantly lower when compared with the bare cells efficiency (16% at 25°C), experiments were carried out in several components accuracy in order to estimate their influence in the final electric and thermal output breakdown. One of the most significant inaccuracies relates to the reflector. Ideally, every light beam perpendicularly incident to the glazed cover of the trough should be reflected to the PV module. Laser beam tests were carried out during the night and the glazed areas where the light was not focused on the PV cells were marked and are illustrated in Fig. 5. I-V curves were measured with and without the covers and the electrical output was roughly the same. The glazed marked area is approximately 15% of the total glazed area and can represent an optical efficiency margin of improvement on the reflector accuracy for future Simulation and calculation