A device is provided which comprises a solar cell section formed in a plate and a storage battery section. The solar cell section includes one or more solar cells which generate electrical power when they receive light. The storage battery section is lying under the solar cell section and comprises one or more storage battery cells separated by bulkheads. Each of the storage battery cells comprises two chambers containing electrolytic solutions and a membrane dividing the chambers, whereby ions solved in the solutions undergo a change in valences, while maintaining their status as solved ions. Holes are extending through the bulkheads to exchange the electrolytic solutions in the storage battery cells, thereby the concentration of the cells can be maintained to be substantially uniform.