Thermodynamic limits on conversion of solar energy to work or stored energy—Effects of temperature, intensity and atmospheric conditions

For more than two decades the subject of thermodynamic limits on conversion of light to work and/or chemical energy via photovoltaic or photochemical processes has been of considerable interest. Three distinct approaches have been taken to the problem; however, all three have recently been shown to be equivalent and to give identical results. Most earlier calculations have been carried out using AMO or AM1.2 solar spectral distributions. In this paper, we use AM1.5 spectra and concentrate primarily on the effects of variation of atmospheric conditions on calculated power-conversion efficiencies. The conditions we examine are: absorber temperature, total solar intensity, air mass, ozone and water-vapor content of the atmosphere, and the turbidity and visibility of the atmosphere. In addition we have computed efficiencies for the diffuse component of global solar radiation as an approximation to turbid conditions. The results are displayed as plots of solar conversion efficiency vs. bandgap wavelength for each set of conditions. Conclusions are then drawn as to the important variants which can serve to guide the design of photochemical and/or photovoltaic systems for a given environment.