A power generation system utilizing an electrochemical cell comprising a reactive metal anode, a cathode spaced from the anode and an electrolyte comprising an aqueous solution of the hydroxide of the reactive metal is disclosed. The hydroxide concentration in the electrolyte is controlled by contacting the electrolyte with an acid anhydride to form an insoluble compound of the reactive metal. The insoluble compound is separated from the electrolyte and the electrolyte is recirculated to the electrochemical cell.