A dialytic battery with ion-exchange membranes: Dependence of the power output on the concentration of saline water

A dialytic battery (DB) with ion-exchange membranes can convert the mixing free energy into the electric energy. The solar membrane cell (SMC) which was proposed by one of the present authors consists of DB and a solar still. The seawater is separated into the fresh water and the concentrated seawater by flowing through the solar still. Therefore, in order to seek a feasibility of SMC it needs to make a performance test of DB at higher concentration than the seawater. In the present study, an experimental study has been made on the concentration dependence of the DB-performance. The dialytic battery constructed consists of 101 compartments and has an effective area of 475cm2 per a sheet of ion-exchange menbrane. The carbon plate electrodes were used, which would produce not only an electric power, but also useful materials such as Cl2-, H2-gas as a result of the electrode reaction. The saline water concentration cc ranged from 3.5-17wt%. The open circuit potential decreased from 9 to 7V with increasing cc. The power output, however, increased considerably with the increase in cc due to the decrease in the internal resistance: The maximum power of about 1100mW was obtained at the concentration of 17wt%. The Weinstein-Leitz model has been modified so as to be applicable to the present case. An good agreement was obtained between the calculated and the measured.