A Novel High-Performance Mission-Enabling Multi-Purpose Radioisotope Heat Source

Durka, Michael J.; Fleurial, Jean‐Pierre; Wielgosz, Sarah E.; Riley, Shane P.; Barry, Matthew; Woerner, David; Barstow, Brian; Drymiotis, Fivos; Nesmith, Bill

doi:10.1109/aero53065.2022.9843667

Cited by 5 publications

(4 citation statements)

References 10 publications

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“…The low-temperature nand p-type segments, denoted n LT and p LT , have a maximum allowable temperature of 873 [K], as per the allowable limits of the MOD2 materials [13,14]. If the interfacial temperature within either of the n LT or p LT segments exceeds the established limits, the solution is considered invalid.…”

Section: Methodsmentioning

confidence: 99%

“…These methods include linear parameter sweeps, parameter sweeps with physics-based logical checks, one-axis Golden Section Search (GSS), and successive refinement algorithms. The methodologies presented herein were instrumental in the TFEC-2022-40925 execution of a much larger trade study performed by Durka et al [13], which used a GSS-based algorithm to determine optimal RTG designs using novel heat sources and converter materials. Without the speedup provided by GSS, the optimization problem in that work would not have been computationally tractable.…”

Section: Introductionmentioning

confidence: 99%

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Optimization Methods for Segmented Thermoelectric Generators

Riley

Wielgosz

et al. 2022

Proceeding of 7th Thermal and Fluids Engineering Conference (TFEC)

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Future National Aeronautics and Space Administration deep-space missions are seeking radioisotope propulsion systems (RPS) to have specific powers above 8 [W e /kg], while having thermal conversion efficiencies greater than 12%. The design and optimization of segmented thermoelectric unicouples used within RPS requires a multi-faceted approach to maximize device performance. The design space of a unicouple can span multiple dimensions, requiring immense computational resources to conduct parametric studies. These dimensions include, but are not limited to, the independent cross-sectional areas of the nand p-type legs, the total height of the unicouple, the length of the high-temperature nand p-type segments, the cold-side junction temperature and the load resistance applied to the couple, considering a fixed hot-side junction temperature, fixed per-couple heat input, and desired output voltage. To this end, computationallyinexpensive methods that optimize segmented unicouples are presented and compared. These methods include physics-based algorithms that dynamically reduce the design space when nonviable configurations are found, implementation of Golden Section Search (GSS) algorithm when uni-modal behavior is observed for a specific degree of freedom, and successive design space refinement. When using both GSS and successive design space refinement algorithms, an optimum geometry was found with 5,755 times fewer solver calls in comparison to the conventional parametric study without any loss of fidelity. This comparison indicates the proposed optimization methods are robust and accurate, while also drastically reducing the computation time to find the optimum unicouple configuration that maximizes system-level power output. These methods allow for exhaustive trade studies to be conducted of newly proposed heat sources, converter materials and designs, and heat exchange systems.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Optimization Methods for Segmented Thermoelectric Generators

Riley

Wielgosz

et al. 2022

Proceeding of 7th Thermal and Fluids Engineering Conference (TFEC)

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“…RTG systems have been found to be reliable, uninterruptable energy sources; however, they have low specific power (~2.4 W/kg to 8.1 W/kg) and many safety concerns (Hendricks et al, 2019;Durka et al, 2022). RTGs generally utilize Plutonium-238 oxide as a fuel with a half-life of 88 years to generate the residual heat and produce electrical power (Gusev et al, 2011;Urban-Klaehn et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Assessment of the calendar aging of lithium-ion batteries for a long-term—Space missions

et al. 2023

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Energy availability is a critical challenge for space missions, especially for those missions designed to last many decades. Space satellites have depended on various combinations of radioisotope thermoelectric generators (RGTs), solar arrays, and batteries for power. For deep space missions lasting as long as 50 + years, batteries will also be needed for applications when there is no sunlight and RTGs cannot support peak power demand due to their insufficient specific power. This paper addresses the potential use of lithium-ion batteries for long-term space missions. Using data collected from the literature and internal experiments, a calendar aging model is developed to assess the capacity fade as a function of temperature, state-of-charge and time. The results for various LIB chemistries are used to identify the best candidate chemistries and determine the conditions, with a focus on low temperatures, that can best enable deep space missions.

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“…Though numerical models have been used to evaluate the performance of thermoelectric generators in lieu of experimental data, they are computationally intensive and there is variability of predicted results based on the inclusion and treatment of thermoelectric phenomena. Thus, robust analytic models are desirable for the rapid and accurate design and optimization of TEGs, such as in trade studies [16], where any compromise in fidelity is far out-weighed by reduced computational cost.…”

Section: Introductionmentioning

confidence: 99%

Mathematical Modeling of a Thermoelectric Generator Unicouple

Wielgosz

Riley

et al. 2022

Proceeding of 7th Thermal and Fluids Engineering Conference (TFEC)

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To ascertain the simultaneous thermal and electrical performance of a thermoelectric (TE) unicouple with interconnectors, a thermal-electric coupled iterative mathematical model is introduced. The non-linear constitutive equations describing TE phenomena within the unicouple are linked to a thermal resistance network describing the interconnectors' behavior. Thereupon, the thermal resistance of the interconnectors, and Joule heat generated within, are considered. Temperature dependent material properties are handled by integral-averaging techniques and an iterative solution methodology. Model form uncertainty is quantified by evaluating four unique analytic models. The first, the Implicit Thomson Model (ITM), considers the Thomson effect via integral averaging of the Seebeck coefficient. The second, the Explicit Thomson Model (ETM), decouples the Thomson effect from the Peltier effect; Thomson heat is explicitly solved using the Thomson coefficient. The third, the zT model, uses the figure of merit to describe the optimum efficiencymaximizing load resistance, and quantify device efficiency under maximum power scenarios. The last, the Differential Equation Model, does not assume distributions of Joule and Thomson heats to the cold-and hotside interfaces as do the ITM, ETM and zT model. The predictive ability of each analytic model used within the unicouple-level model is compared to high-fidelity numeric results obtained from a three-dimensional, thermal-electric coupled model implemented in ANSYS CFX. Considering a range of hot-side unicouple temperatures, each analytic model exhibits agreement with one another, and with the numeric model. With increasing load resistance values, model form uncertainty and disagreement between analytic and numeric predictions decreases to a couple of percent at optimum operating points.

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A Novel High-Performance Mission-Enabling Multi-Purpose Radioisotope Heat Source

Cited by 5 publications

References 10 publications

Optimization Methods for Segmented Thermoelectric Generators

Optimization Methods for Segmented Thermoelectric Generators

Assessment of the calendar aging of lithium-ion batteries for a long-term—Space missions

Mathematical Modeling of a Thermoelectric Generator Unicouple

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