A electrochemical direct heat to electricity converter having a low temperature membrane electrode assembly array and a high temperature membrane electrode assembly array is provided. Additional cells are provided in the low temperature membrane electrode assembly array, which causes an additional amount of the working fluid, namely hydrogen, to be pumped to the high pressure side of the converter. The additional pumped hydrogen compensates for the molecular hydrogen diffusion that occurs through the membranes of the membrane electrode assembly arrays. The MEA cells may be actuated independently by a controller to compensate for hydrogen diffusion.