ACCURATE UPPER BOUND EFFICIENCY FOR SOLAR THERMAL POWER GENERATION

A class of accurate upper bounds for the efficiency of converting solar energy into work was derived in this paper by taking into account (i) the irreversibilities associated with the heat transfer inside the heat engine and (ii) details about the system considered, as the geometric (view) factor of the Sun, the dilution factors of solar and ambient radiation and the optical properties of the converter (concentration ratio, absorptance, reflectance and transmittance for both transparent cover and absorber), A simpler (but less accurate) upper bound efficiency is: where T s, and T0 are Sun and ambient temperatures, respectively. This upper bound is still more accurate than the upper limit efficiencies usually cited in literature.