Estimating the performance of product integrated photovoltaic (PIPV) cells under indoor conditions for the support of design processes

To estimate the performance of PV products´ cells in an indoor environment we have developed an analytical model, which calculates the efficiency and power production of various types of PV technologies as a function of distance from natural and artificial light sources. The model aims to assist designers during the energy balance calculations when creating PV-integrated products for indoor use. To validate the model, PV cells of 10 commercially available PV-powered products in the power range of 0.8mWp to 4mWp, have been measured indoors, under three types of artificial illumination (halogen, fluorescent, LED lights) and natural light. Since the model´s purpose is to give a best estimation for design processes, the accuracy does not need to be high. Moreover, given the difficulty to accurately measure low irradiance (<; 20W/m²) so far it seems impossible to achieve highly accurate results. The measurements´ analysis showed that the model can sufficiently predict the performance of PV products´ cells under CFL and LED artificial lighting, as well as under mixed indoor light with a typical error around 25%. Measurements showed that under typical mixed indoor irradiance of up to 20W/m², a-Si cells´ efficiency ranges between 5-6W/m² (48%), c-Si cells´ between 5-7W/m² (72%) and mc-Si cells´ between 4-6W/m² (65%). Still, there are significant deviations on the model outcome for the halogen lamp, for which reason the model cannot be used in that situation yet.