# US 7,611,789 B2 · Energy storage system

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- Number: US 7,611,789 B2
- Document ID: US7611789B2
- Status: Granted
- Kind: B2
- Application number: 11/981,202
- Filed: 2007-10-31
- Published: 2008-07-10
- Granted: 2009-11-03
- Earliest claimed: 2002-04-17
- Assignees: Aero Vironment, Inc.
- Inventors: Bart D. Hibbs; William M. Parks; Omourtag A. Velev
- Web page: https://patentgrep.com/patent/US7611789B2

## CPC

- H01M 8/04097: {with recycling of the reactants (H01M8/04119, H01M8/04104 take precedence)}
- B64D 27/33: Hybrid electric aircraft
- B64D 27/353: using solar cells
- B64D 27/355: using fuel cells
- B64D 27/357: using batteries
- H01M 8/04164: {by condensers, gas-liquid separators or filters}
- H01M 8/0656: by electrochemical means (H01M8/065 takes precedence)
- H01M 8/186: {by electrolytic decomposition of the electrolytic solution or the formed water product}
- B64D 2041/005: {Fuel cells}
- H01M 8/04373: {of auxiliary devices, e.g. reformers, compressors, burners}
- H01M 8/04768: {of the coolant}
- Y02E 60/36: Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
- Y02E 60/50: Fuel cells
- Y02P 20/133: Renewable energy sources, e.g. sunlight
- Y02T 50/40: Weight reduction
- Y02T 50/50: On board measures aiming to increase energy efficiency
- Y02T 50/60: Efficient propulsion technologies, e.g. for aircraft
- Y02T 90/40: Application of hydrogen technology to transportation, e.g. using fuel cells
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## 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.

## Claims

### Claim 1

A closed loop power plant for use in freezing ambient conditions, comprising:
a fuel cell stack configured to react a gaseous fuel with a gaseous oxidizer to produce a liquid product and electrical power;
a fuel storage tank configured to store dried gaseous fuel for subsequent reaction in the fuel cell stack;
an oxidizer storage tank configured to store dried gaseous oxidizer for subsequent reaction in the fuel cell stack;
a product storage container for storing the liquid product;
an electrolyzer stack configured to separate the liquid product into a humid fuel including the gaseous fuel and product humidity, and a humid oxidizer including the gaseous oxidizer and product humidity;
a heat exchanger configured to remove the product humidity from the humid fuel and the humid oxidizer to produce dried gaseous fuel and dried gaseous oxidizer; and
a thermal enclosure that encloses the fuel cell stack, the electrolyzer stack and the product storage container, wherein the fuel storage tank and the oxidizer storage tank are not thermally enclosed.

### Claim 2 (depends on 1)

The energy storage system of claim 1, wherein the heat exchanger is further configured to use excess heat from the fuel cell stack 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.

### Claim 3 (depends on 2)

The energy storage system of claim 2, wherein the product storage container is an oxidizer phase separator.

### Claim 4 (depends on 1)

The energy storage system of claim 1, wherein the product storage container is an oxidizer phase separator.