Energy storage system

Abstract

A closed loop energy storage system configured with a hydrogen tank, an oxygen tank, a fuel cell stack and an electrolyzer. A heat exchanger freeze-dries the hydrogen and oxygen prior to their storage in their respective tanks. The heat exchanger also uses excess fuel cell heat to preheat streams of hydrogen and oxygen coming from the tanks. Phase separators serve both to separate water from hydrogen and oxygen, and to store the water. A thermal management system encloses all the system components except the tanks. An airfoil-shaped shell covers the system, and the larger of the two tanks extends substantially across the shell at its point of greatest camber thickness. The tanks are composed of polymer liners integral with composite shells.

1 . A method for storing available energy and providing needed energy, using a fuel tank configured to store dried gaseous fuel; an oxidizer tank configured to store dried gaseous oxidizer; a fuel cell stack configured to react gaseous fuel with gaseous oxidizer to form a liquid product; an electrolyzer stack configured to separate the liquid product into humid fuel and humid oxidizer; and a heat exchanger, comprising:
 operating the fuel cell stack using gaseous fuel from the fuel tank and gaseous oxidizer from the oxidizer tank to produce the liquid product and electrical energy during times when energy is needed;   operating the heat exchanger during fuel cell stack operation to preheat the gaseous fuel from the fuel tank and the gaseous oxidizer from the oxidizer tank prior to the gaseous fuel and the gaseous oxidizer being reacted in the fuel cell stack;   operating the electrolyzer stack to separate liquid product into humid fuel that includes gaseous fuel and product humidity, and humid oxidizer that includes gaseous oxidizer and product humidity, during times when energy is available;   operating the heat exchanger during electrolyzer stack operation to freeze the product humidity out of the humid fuel and the humid oxidizer to produce dried gaseous fuel and dried gaseous oxidizer.   
   
   
       2 . The method of  claim 2 , wherein during fuel cell stack operation, heat from the fuel cell is used by the heat exchanger to preheat the gaseous fuel and gaseous oxidizer.