Solar cells, in general, perform under light source of solar influx, while the heat energy of solar radiation remains unutilized. Using an aqueous suspension of copper doped zinc oxide nanoparticles in specially-designed electrochemical cells we have observed significant voltage (maximum 632.0 mV) and storage duration (similar to 47 h) upon thermal excitation. The cells exhibit reasonable energy conversion efficiency (maximum 1.36%). These cells generate voltage even at room temperature (similar to 30 degrees C) and the voltage increases gradually with increasing temperature. When the platinum foil separating the two compartments of the electrochemical cell is replaced by a planar lipid membrane, all the parameters e.g., thermovoltage, storage capacity and the energy conversion efficiency increase significantly. (C) 2014 Elsevier B.V. All rights reserved.