Calibrating underwater photovoltaic performance: Demonstration using monocrystalline and polycrystalline silicon solar cells

The present investigations discuss methodologies to report the photovoltaic efficiency of solar cells in submerged conditions measured using simulated AM 1.5G using Xenon and LED lamps. These protocols have been arrived at from the photovoltaic measurements in encapsulated monocrystalline and polycrystalline silicon solar cells immersed in water up to a depth of 20 cm. Three equations are proposed to judge the efficiency of the solar cells in underwater conditions based on the input irradiance that is incident on the cells. It is suggested that the helpful efficiency metric is the one in which a corrected irradiance falls on the cells. The correction factors for the irradiance are based on the properties of the light source used in the solar simulator and the spectral response limitations of the pyranometer used for the experimental irradiance measurements underwater. Experimental data from monocrystalline and polycrystalline silicon solar cells show efficiency reductions of 43 % and 56 % at a depth of 20 cm compared to the efficiencies at the water surface due to reduced irradiance underwater. The present investigations indicate that solar cell efficiencies are overestimated by 59 % and 64 % for monocrystalline silicon solar cells and polycrystalline silicon solar cells underwater at 20 cm if the corrections are not considered. The efficiency calibration procedures applied to a commercially available solar panel predict a decrease in the photovoltaic efficiency of 45 % at 20 cm depth underwater. Furthermore, the suitability of different materials for applications at various depths is also discussed based on the absorption efficiency calculations of a solar cell material in submerged conditions. The experimental measurements of illuminations underwater could be improved by using a submersible pyranometer with a spectral response that matches the AM 1.5 G radiation.