System-level Testing of the Advanced Stirling Radioisotope Generator Engineering Hardware

Chan, Tak Shing

doi:10.2514/6.2014-3966

Cited by 8 publications

(3 citation statements)

References 2 publications

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“…Further refinements to the DC bus voltage compensation algorithm could reduce the sensitivities. 8 The EDU 4.1 sensitivities were significantly smaller than sensitivities observed during EU testing with EDU 1.…”

Section: F DC Bus Voltage Variationmentioning

confidence: 80%

Characterization of the Advanced Stirling Radioisotope Generator EU2

Lewandowski

Oriti²,

Schifer³

2015

13th International Energy Conversion Engineering Conference

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Significant progress was made developing the Advanced Stirling Radioisotope Generator (ASRG), a 140-watt radioisotope power system. While the ASRG flight development project has ended, the hardware that was designed and built under the project is continuing to be tested to support future Stirling-based power system development. NASA GRC recently completed the assembly of the ASRG Engineering Unit 2 (EU2). The ASRG EU2 consists of the first pair of Sunpower's ASC-E3 Stirling convertors mounted in an aluminum housing, and Lockheed Martin's Engineering Development Unit (EDU) 4 controller (a fourth generation controller). The ASC-E3 convertors and Generator Housing Assembly (GHA) closely match the intended ASRG Qualification Unit flight design. A series of tests were conducted to characterize the EU2, its controller, and the convertors in the flight-like GHA. The GHA contained an argon cover gas for these tests. The tests included: measurement of convertor, controller, and generator performance and efficiency, quantification of control authority of the controller, disturbance force measurement with varying piston phase and piston amplitude, and measurement of the effect of spacecraft DC bus voltage on EU2 performance. The results of these tests are discussed and summarized, providing a basic understanding of EU2 characteristics and the performance and capability of the EDU 4 controller. Nomenclature FA, FB= Total dynamic force for ASC A, ASC B (N); sum of piston and displacer inertial forces FD

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Section: F DC Bus Voltage Variationmentioning

confidence: 80%

Characterization of the Advanced Stirling Radioisotope Generator EU2

Lewandowski

Oriti²,

Schifer³

2015

13th International Energy Conversion Engineering Conference

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“…The units were then provided to Lockheed Martin for successful controller functional testing. 8 The units have been returned to GRC, completed receipt checkout tests, and are being prepared for integration into the ASRG EU2. The ASC-E3 Pair 1 convertors have each accumulated over 3,100 hours of operation at GRC with steady flat-line performance.…”

Section: B Continued Asc-e3 Production At Sunpower and Asrg Eu2 Assembly At Grcmentioning

confidence: 99%

Advanced Stirling Convertor (ASC) Development for NASA RPS

Wong¹,

Wilson²,

Collins³

2014

12th International Energy Conversion Engineering Conference

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Sunpower's Advanced Stirling Convertor (ASC) initiated development under contract to the NASA Glenn Research Center (GRC) and after a series of successful demonstrations, the ASC began transitioning from a technology development project to flight development project. The ASC has very high power conversion efficiency making it attractive for future Radioisotope Power Systems (RPS) in order to make best use of the low plutonium-238 fuel inventory in the U.S. In recent years, the ASC became part of the NASA-Department of Energy Advanced Stirling Radioisotope Generator (ASRG) Integrated Project. Sunpower held two parallel contracts to produce ASC convertors, one with the Department of Energy/Lockheed Martin to produce the ASC-F flight convertors, and one with NASA GRC for the production of ASC-E3 engineering units, the initial units of which served as production pathfinders. The integrated ASC technical team successfully overcame various technical challenges that led to the completion and delivery of the first two pairs of flight-like ASC-E3 by 2013. However, in late Fall 2013, the DOE initiated termination of the Lockheed Martin ASRG flight development contract driven primarily by budget constraints. NASA continues to recognize the importance of high efficiency ASC power conversion for RPS and continues investment in the technology including the continuation of ASC-E3 production at Sunpower and the assembly of the ASRG Engineering Unit #2. This paper provides a summary of ASC technical accomplishments, overview of tests at GRC, plans for continued ASC production at Sunpower, and status of Stirling technology development.

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“…Despite the promised high power, a mechanical system may not have the longevity for deep space missions . [28][29][30][31][32][33][34][35][36] Figure 1. Comparison of conventional semiconductor-based thermoelectric concept (a) to the new metallic junction thermoelectric concept (b).…”

Section: Introductionmentioning

confidence: 99%

Metallic junction thermoelectric device simulations

Duzik

Choi

2017

SPIE Proceedings

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Thermoelectric junctions made of semiconductors have existed in radioisotope thermoelectric generators (RTG) for deep space missions, but are currently being adapted for terrestrial energy harvesting. Unfortunately, these devices are inefficient, operating at only 7% efficiency. This low efficiency has driven efforts to make high-figure-of-merit thermoelectric devices, which require a high electrical conductivity but a low thermal conductivity, a combination that is difficult to achieve. Lowered thermal conductivity has increased efficiency, but at the cost of power output.An alternative setup is to use metallic junctions rather than semiconductors as thermoelectric devices. Metals have orders of magnitude more electrons and electronic conductivities higher than semiconductors, but thermal conductivity is higher as well. To evaluate the viability of metallic junction thermoelectrics, a two dimensional heat transfer MATLAB simulation was constructed to calculate efficiency and power output. High Seebeck coefficient alloys, Chromel (90%Ni-10%Cr) and Constantan (55%Cu-45%Ni), produced efficiencies of around 20-30%. Parameters such as the number of layers of junctions, lateral junction density, and junction sizes for both series-and parallel-connected junctions were explored.

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System-level Testing of the Advanced Stirling Radioisotope Generator Engineering Hardware

Cited by 8 publications

References 2 publications

Characterization of the Advanced Stirling Radioisotope Generator EU2

Characterization of the Advanced Stirling Radioisotope Generator EU2

Advanced Stirling Convertor (ASC) Development for NASA RPS

Metallic junction thermoelectric device simulations

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