  The conversion of heat into current can be obtained by a process with two
stages. In the first one, the heat is used for distilling a solution and
obtaining two flows with different concentrations. In the second stage, the two
flows are sent to an electrochemical cell that produces current by consuming
the concentration difference. In this paper, we propose such an electrochemical
cell, working with water solutions of zinc chloride. The cell contains two
electrodes, made respectively of zinc and silver covered by silver chloride.
The operation of the cell is analogous to that of the capacitive mixing and of
the "mixing entropy battery": the electrodes are charged while dipped in the
concentrated solution and discharged when dipped in the diluted solution. The
cyclic operation allows us to extract a surplus of energy, at the expense of
the free energy of the concentration difference. We evaluate the feasibility of
such a cell for practical applications, and find that a power up to 2 W per
square meter of surface of the electrodes can be achieved.
