Collaboratrici e collaboratori

The spectral filtering low concentration photovoltaic system developed by Voltiris is an innova-tive solution for energy production in greenhouses without affecting food production. A first prototype was installed in the Swiss greenhouse research center Agroscope in Conthey, Swit-zerland. During an eight-month agronomic study from March to October 2022, I-V curves were recorded to evaluate the system performance, and the effect of concentration and filtering. The curves showed that the system can achieve a direct normal irradiation efficiency of 10.1 %. The results were benchmarked with those of conventional solar panels placed next to the Vol-tiris system. The specific power output of the system inside the greenhouse was comparable to the one of a conventional solar panel placed outside. Furthermore, to understand how the filters might affect photosynthesis, the optical properties of the filters were studied and com-pared to chlorophyll absorption spectra. Spectrometric and radiation analysis showed that the filters reflected 49 % of the incident global radiation and that the spectrum reduced by the reflectance did not impact photosynthesis. To transfer the performance of the system to other greenhouses, the transmittance of the test greenhouse was measured for global and diffuse radiation. The transmission coefficients allowed to separate the effects of the glass transmit-tance and the greenhouse specific metal structure. In the test greenhouse, the direct transmis-sion coefficient was found to reach a value of 0.28, hence limiting the system yield in indoor conditions to about 28 % of its outdoor value.