A Fuel Cell Power Supply for Long Duration Balloon Flights Using Stored Cryogens

Abstract

LBNL-40618 A FUEL CELL POWER SUPPLY FOR LONG DURATION BALLOON FLIGHTS USING STORED CRYOGENS M. A. Green a , A. Manikowski b , G. Noland b and R. L. Golden c a b c E. O. Lawrence Berkeley National Laboratory University of California Berkeley, CA 94720 Procyon Power Systems Inc. Alameda, CA 94501 New Mexico State University R. L. Golden Particle Astrophysics Lab Las Cruces, NM 88003 ABSTRACT Large balloon launched cosmic ray experiments can require up to 1.8 kW of power for the duration of the mission. Present day battery packs, which have a mass of 550 kg, limit the mission time for such experiments to less than 60 hours. Long duration polar balloon missions require a power supply that can deliver power at the rate of 1.5 to 2 kW for a period of time from 10 to 21 days. A hydrogen-oxygen fuel cell is an attractive option for a power supply because 20.6 kg (291 liters) of hydrogen and 165 kg (144 liters) of oxygen can provide the 1.42 kW of power for a 18 day mission at a fuel cell efficiency of 80 percent. If the water produced by the oxidation of the hydrogen in the fuel cell can be dumped during the mission, the required ballast needed for the mission can be reduced by almost 190 kg. The waste heat from the fuel cell can be used to preheat the fuel and oxidizer before they enter the fuel cell. The remainder of the waste heat must be transferred away from the balloon by radiation. This report describes a fuel cell power supply configuration. INTRODUCTION Much of today's cosmic ray physics is being done on balloon platforms operating at a distance of 30 to 40 km (100000 to 130000 feet) above the earth's surface. At this altitude all but 0.3 percent of the earth's atmosphere is below the experiment. Modern balloon experimental payloads can have a mass of more than 3000 kg (6600 lb.). Included in a typical particle astrophysics payload mass would be the gondola, possibly a superconducting magnet, particle detectors such as drift chambers and calorimeters, the electronics needed to detect and record the particle tracks, the payload control electronics, the telemetry to connect the experiment to the ground, and some ballast (perhaps 200 to 300 kg) for altitude control. As with ground based particle physics detectors, physics detectors carried in a balloon gondola require electric power to run the detectors and the electronics associated with these detectors 1 . In addition, electric power is needed for the telemetry used to communicate with the ground and temperature control within the gondola. In a typical balloon experiment, the power is supplied by lithium chloride batteries, which can store about 140 Whr (0.5 MJ) of electrical energy per kilogram of battery mass. (By comparison, lead acid batteries, which