New Approach to Radioisotopic Energy Sources for Improved Efficiency and Lifespan

Science

Beta-voltaic radioisotope (RPS) power sources are devices that directly convert beta particles (electrons) from a source of beta-emitting radioisotopes (such as nickel-63) into electrical energy. These devices have a high power density, which means that they can release a large amount of energy quickly when needed. They also have a high energy density, which means that they store large amounts of energy. They are ideal for applications such as spacecraft that require power sources that can operate for many years under harsh conditions without human intervention. Researchers recently explored a new approach to make beta-voltaic RPSs more efficient at converting heat into electricity. These NextGen RPSs apply isotopes in new ways to improved converters. This gives NextGen RPSs excellent potential to provide long-term compact power in remote and extreme environments.

The impact

Small sensors often used in remote and / or extreme environments on earth and in space require power sources that provide high energy and power density to operate continuously for 3 to 25 years. Chemical batteries can only provide short-term solutions. A beta-voltaic RPS is an alternative to a chemical battery. These RPSs can store 1,000 times more than a chemical battery, allowing them to power small sensors for many years. This research shows how the performance of beta-voltaic RPS can be improved by improving the efficiency with which they convert radioactive decay into electricity. This breakthrough will help make RPS even more efficient for small devices requiring small amounts of power and represents a promising first step in increasing the power density of nuclear batteries from microwatts to milliwatts per 1000 cm.3 with the implementation of more energetic beta sources.

Summary

Beta-voltaic batteries are a type of RPS. Radioisotopes used in beta-voltaic batteries (eg, Ni-63, Pm-147) are produced by the DOE Isotope Program. In traditional beta-voltaic batteries, the radioisotope is deposited on a metal foil which is placed on top of a semiconductor converter. The interaction between the radioisotope and the converter can limit RPS performance. This research has demonstrated an approach where long-lived beta-emitting radioisotopes can be used to match the power density (the ability to release energy) of chemical batteries while outperforming them in energy density. (the ability to store energy). Researchers investigated how converter geometry and beta conversion can influence performance by improving source efficiency and surface power density. The researchers focused on a beta-voltaic battery configuration consisting of nickel-63 directly applied to a beta-voltaic cell of polytype of 4-H silicon carbide (4H-SiC). Switching from a planar converter geometry to a textured 4H-SiC beta-voltaic cell has improved the power density by seven times. The efficiency of the converter was doubled compared to a silicon cell when the researchers applied nickel-63 directly to the 4H-SiC textured beta-voltaic cell. Beta conversion can be captured from both sides of the radioisotope source. This allows two cells to collect beta conversion instead of one cell and increases the surface power density. This research has shown that the interaction between the radioisotope and the converter is essential for efficient energy conversion. These NextGen beta-voltaic RPSs have excellent potential to meet compact, long-life power requirements for applications in remote and / or extreme environments.

Funding

This work was supported by the US Army Research Laboratory and the National Aeronautics and Space Administration using nickel-63 radioisotopes provided by the Department of Energy Isotope Program, managed by the Office of Isotope R&D and Production. 4H-SiC cells were provided by Widetronix Inc.

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Rosemary C. Kearney