Emissivity Tuned Emitter for RTPV Power Sources

Conference · Thu Mar 01 00:00:00 EST 2012

OSTI ID:1047203

Stoots, Carl M; O'Brien, Robert C; Howe, Troy M

Every mission launched by NASA to the outer planets has produced unexpected results. The Voyager I and II, Galileo, and Cassini missions produced images and collected scientific data that totally revolutionized our understanding of the solar system and the formation of the planetary systems. These missions were enabled by the use of nuclear power. Because of the distances from the Sun, electrical power was produced using the radioactive decay of a plutonium isotope. Radioisotopic Thermoelectric Generators (RTGs) used in the past and currently used Multi-Mission RTGs (MMRTGs) provide power for space missions. Unfortunately, RTGs rely on thermocouples to convert heat to electricity and are inherently inefficient ({approx} 3-7% thermal to electric efficiency). A Radioisotope Thermal Photovoltaic (RTPV) power source has the potential to reduce the specific mass of the onboard power supply by increasing the efficiency of thermal to electric conversion. In an RTPV, a radioisotope heats an emitter, which emits light to a photovoltaic (PV) cell, which converts the light into electricity. Developing an emitter tuned to the desired wavelength of the photovoltaic is a key part in increasing overall performance. Researchers at the NASA Glenn Research Center (GRC) have built a Thermal Photovoltaic (TPV) system, that utilizes a simulated General Purpose Heat Source (GPHS) from a MMRTG to heat a tantalum emitter. The GPHS is a block of graphite roughly 10 cm by 10 cm by 5 cm. A fully loaded GPHS produces 250 w of thermal power and weighs 1.6 kgs. The GRC system relies on the GPHS unit radiating at 1200 K to a tantalum emitter that, in turn, radiates light to a GaInAs photo-voltaic cell. The GRC claims system efficiency of conversion of 15%. The specific mass is around 167 kg/kWe. A RTPV power source that utilized a ceramic or ceramic-metal (cermet) matrix would allow for the combination of the heat source, canister, and emitter into one compact unit, and allow variation in size and shape to optimize temperature and emission spectra.

• Research Organization: Idaho National Laboratory (INL)
• Sponsoring Organization: DOE - NE
• DOE Contract Number: AC07-05ID14517
• OSTI ID: 1047203
• Report Number(s): INL/CON-11-24023
• Conference Information: Nuclear and Emerging Technologies for Space,The Woodlands, TX,03/21/2012,03/23/2012
• Country of Publication: United States
• Language: English

Related Subjects

08 HYDROGEN
30 DIRECT ENERGY CONVERSION
42 ENGINEERING
CERAMICS
DECAY
EFFICIENCY
ELECTRICITY
EMISSION SPECTRA
EMISSIVITY
GRAPHITE
HEAT SOURCES
NASA
NESDPS Office of Nuclear Energy Space and Defense Power Systems
NUCLEAR POWER
Photovoltaic
PLANETS
PLUTONIUM ISOTOPES
RADIOISOTOPES
Radioisotopic
SOLAR SYSTEM
TANTALUM
Thermal
THERMOCOUPLES
THERMOELECTRIC GENERATORS
WAVELENGTHS