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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

NASA Acoustic Stirling IRAD Thermal Recovery Energy Efficient System (TREES) Energy Conversion and Management in Aircraft

NASA Acoustic Stirling IRAD (Internal Research and Development) Thermal Recovery Energy Efficient System (TREES) Energy Conversion and Management in Aircraft. Presentation on energy conversion on aircraft. Thermal energy recovery changes aircraft thermal management from being a necessary burden on aircraft performance to a desirable asset. It improves the engine performance by recycling waste heat and ultimately rejecting all collected aircraft heat out through the engine nozzle.

Dyson, Rodger↗
NASA NTRS2019

Comparison of Energy Conversion Technologies for Space Nuclear Power Systems

A key element of space nuclear power systems is the energy conversion subsystem that converts the nuclear heat into electrical power. Nuclear systems provide a favorable option for missions that require long-duration power in hostile space environments where sunlight for solar power is absent or limited. There are two primary nuclear power technology options: (1) radioisotope power systems (RPSs) utilize the natural decay heat from 238Pu to generate electric power levels up to about 1 kW and (2) fission power systems (FPSs) rely on a sustained fission reaction of 235U and offer the potential to supply electric power from kilowatts to megawatts. Example missions utilizing nuclear power include Mars science rovers (e.g., Curiosity, Mars 2020), lunar and Mars surface landers, crewed surface outposts, deep space planetary orbiters, Ocean World science landers, and robotic space probes that utilize nuclear electric propulsion. This report examines the energy conversion technology options that can be used with RPSs and FPSs, and provides an assessment of their relative performance.

Lee S Mason↗
NASA NTRS2017

Forward Contamination of Ocean Worlds: A Stakeholder Conversation

A fundamental requirement for space missions designed to touch “potential habitats” is the single number 10−4, the allowable probability of a single Earth organism contaminating the potential habitat. Many aspects of a mission that affect its complexity and cost – hardware design and manufacture, assembly and test, and mission operations – are driven by this value, so it is important, on the threshold of an era of exploring ocean worlds, to have confidence in it. Yet despite its long pedigree and occasional reviews, we find that the current requirement lacks programmatically defensible justification. At issue are three weaknesses: 1) microbial biology, in particular the science of extremophiles, is a rapidly changing field; 2) forward contamination is both a scientific and an ethical issue, yet no ethics-based conversation is apparent within policy-setting circles; 3) because of these two factors, policy-setting cannot be static. We review the history of the requirement; how the evolving understanding of biology could drive it up or down; how the forward-contamination hazard relates to risk-management practice and to the ethics profession; and how a contemporary stakeholder conversation could adapt lessons already learned by other fields.

Waltemathe, Michael↗
NASA NTRS2019

Satellite-Based Assessment of Grassland Conversion and Related Fire Disturbance in the Kenai Peninsula, Alaska

Spruce beetle-induced (Dendroctonus rufipennis (Kirby)) mortality on the Kenai Peninsula has been hypothesized by local ecologists to result in the conversion of forest to grassland and subsequent increased fire danger. This hypothesis stands in contrast to empirical studies in the continental US which suggested that beetle mortality has only a negligible effect on fire danger. In response, we conducted a study using Landsat data and modeling techniques to map land cover change in the Kenai Peninsula and to integrate change maps with other geospatial data to predictively map fire danger for the same region. We collected Landsat imagery to map land cover change at roughly five-year intervals following a severe, mid-1990s beetle infestation to the present. Landcover classification was performed at each time step and used to quantify grassland encroachment patterns over time. The maps of land cover change along with digital elevation models (DEMs),temperature, and historical fire data were used to map and assess wildfire danger across the study area. Results indicate the highest wildfire danger tended to occur in herbaceous and black spruce land cover types, suggesting that the relationship between spruce beetle damage and wildfire danger in costal Alaskan forested ecosystems differs from the relationship between the two in the forests of the coterminous United States. These change detection analyses and fire danger predictions provide the Kenai National Wildlife Refuge (KENWR) ecologists and other forest managers a better understanding of the extent and magnitude of grassland conversion and subsequent change in fire danger following the 1990s spruce beetle outbreak.

wildfire↗
NASA NTRSDate not supplied

Nuclear Electric Propulsion Modular Power Conversion Model

This work builds upon a previously examined single loop power conversion cycle for nuclear electric propulsion systems. The intent of this model is to enable examination of trends within the system and extract system parameters that could be used in a mass model to understand how technology performance may impact overall system mass.Several model upgrades were made since the previous work which included physics-based sizing of the turbomachinery and pressure loss inside the radiator. A higher fidelity and modular fluid property code was also developed to help understand the impact of variable fluid properties more accurately and allow for the analysis of different fluids in the same model. The upgraded model features radiator and reactor loops with separate fluids from the Brayton cycle to understand advantages and disadvantages of using multiple working fluids as well as the capability of simulating off nominal system performance. The latter provides a steppingstone for modeling the transient performance of the power conversion system.

NEP↗
NASA NTRSDate not supplied

Mass Modeling of NEP Power Conversion Concepts for Human Mars Exploration

The specific mass (mass per unit of electric power output) of an NEP power conversion system is an important metric for the performance and feasibility of a crewed NEP vehicle. This work explores a component level buildup of the specific mass for a crewed NEP vehicle. The buildup is highly parametric and avoids being tied to specific technologies where practical. This allows the specific mass to be calculated for a variety of assumptions and operating conditions and be used to optimize particular design variables or compare different system configurations. The values of specific mass are dependent on assumptions with significant uncertainty; comparison between cases and trends observed in the models are the main goal of the work presented here. To demonstrate the level of insight this type of modeling can provide, the impacts of compressor inlet temperature, turbine inlet temperature, and radiator pressure drop on specific mass are explored. In addition, the specific mass can be used to assess the benefit of separating the radiator and reactor loop from the power conversion cycle.

NEP↗
NASA NTRSDate not supplied

Thermoradiative Arrays: A New Technology for Conversion of Heat into Electrical Power

The thermoradiative cell is a recently developed solid-state device for generating electrical power from heat energy. Thermoradiative arrays could be used as the conversion technology for production of electrical power from thermal sources such as nuclear reactors or radioisotope heat sources in space. The technology has the potential for efficient conversion compared to existing technologies used for space, but as yet is in a low state of development, with considerable work to be done. A roadmap of key research needs is given.

heat into electrical power↗
NASA NTRSDate not supplied

Nuclear Electric Propulsion Brayton Power Conversion Working Fluid Considerations

NASA has considered Nuclear Electric Propulsion (NEP) for high V missions since the late 1950’s, but the current technology readiness level of the requisite powertrain needs to be raised for such a mission. The powertrain includes reactor, power conversion, power management, electric propulsion, and thermal management components that must be integrated to minimize system (kg/kWe) and to finalize a propulsion system architecture within the 2025-2027 timeframe requires advancing these component technologies to technology readiness level (TRL) 5 and Advancement Degree of Difficulty (AD2) 3 in an expeditious manner with minimal risks. This paper will only address the power conversion (heat to electric) components of that system. Based on both internal and industry studies, a primary conclusion of this work is that a single-spool supercritical Xe-He radial flux Brayton heat engine combined with a permanent magnet synchronous alternator can potentially be developed with the least technical risk to meet the technology readiness schedule and required NEP system performance metrics.

Nuclear↗
NASA NTRSDate not supplied

Mass Modeling of NEP Power Conversion Concepts for Human Mars Exploration

The specific mass (mass per unit of electric power output) of an NEP power conversion system is an important metric for the performance and feasibility of a crewed NEP vehicle. This work explores a component level buildup of the specific mass for a crewed NEP vehicle. The buildup is highly parametric and avoids being tied to specific technologies where practical. This allows the specific mass to be calculated for a variety of assumptions and operating conditions and be used to optimize particular design variables or compare different system configurations. The values of specific mass are dependent on assumptions with significant uncertainty; comparison between cases and trends observed in the models are the main goal of the work presented here. To demonstrate the level of insight this type of modeling can provide, the impacts of compressor inlet temperature, turbine inlet temperature, and radiator pressure drop on specific mass are explored. In addition, the specific mass can be used to assess the benefit of separating the radiator and reactor loop from the power conversion cycle.

nep↗
NASA NTRSDate not supplied

Thermoradiative Conversion for Space Power Systems

The thermoradiative cell is a new method for converting heat energy to electrical power, first detailed by Strandberg in 2015. The cell is structurally similar to a photovoltaic cell, in that it is a p-n junction semiconductor device, but thermodynamically operates in the reverse direction, converting the thermal dark current into electrical power by utilizing the recombination radiation from thermally-generated electron hole pairs to radiate waste heat to space. This technology may have application for space missions in converting thermal energy produced by a radioisotope source or from a nuclear reactor into power. The power and efficiency can be calculated as a function of bandgap in the detailed-balance case (the Shockley-Queisser limit), in which all of the thermal emissivity of the cell is due to the recombination of thermally generated electron-hole pairs, and all other recombination losses are ignored. The current produced is directly proportional to the recombination radiation, and thus the more thermally generated pairs, the higher the current. The voltage is proportional to the external bias. These two constraints allow optimization of the optimum bias point for maximum power, and allow calculation of the efficiency at maximum power point. Unlike photovoltaic cells, the maximum power operating point is not the same as the maximum efficiency point, and higher efficiency can be achieved at a higher (negative) bias in the ideal case. Incorporating non-ideal losses, however, shifts the maximum efficiency point toward lower bias. Since a thermoradiative cell operates by radiating directly to space, the current produced by a themoradiative cells will increase with the Stefan-Boltzman radiative efficiency; roughly the fourth power of the temperature. Thus, in contrast to a photovoltaic converter, the power produced is highest at high operating temperatures. Likewise, in contrast to conventional thermal conversion, high radiator temperature increases, rather than decreases the efficiency. Thus, the thermoradiative conversion may fill a mission niche in which small radiator size is required. The basic operation will be summarized, applications to space power discussed, and the requirements for further research outlined.

Photovoltaic Cell↗
DOE OSTI2024

Dynamic Modeling of Power Conversion Stages for an Exascale Supercomputer

In this paper a power conversion and energy consumption model for an exascale supercomputer is investigated. Power consumption, energy loss and efficiency are derived for the 27.2 MW liquid-cooled, centralized, High Performance Computing (HPC) power system, which is supplied directly from the 480 V three-phase mains. Two energy conversion stages are analyzed, measured and modeled. The model is developed in order to be adapted and implemented in a digital twin platform utilizing a Resource Allocator and Power Simulator (RAPS) module. RAPS enables estimation of potential energy savings in the direct AC power supply architecture via both conventional rectifier load sharing (commonly used in HPC systems), as well as smart rectifier load sharing. Moreover, besides the direct AC supply architecture analysis, the full direct DC supply architecture with with 1 kV DC bus were also studied. Comparison of 10 hour time frame operation of the system, with direct 480 V AC voltage supply with conventional and smart load sharing and medium dc voltage supply were done. For the direct AC supply architecture, with conventional and smart load sharing the predicted power loss was approximately 840 kW and 820 kW, respectively and the predicted total system efficiency was 92.87% and 93.05%, respectively. For the direct DC supply architecture with the 1000 V DC supply bus power loss was approximately 340 kW and the predicted total system efficiency was 97.02%.

Wojda, Rafal↗
DOE OSTI2024

Electromagnetic field-assisted method for chemical conversion

Embodiments relate to methods for enhancing chemical conversions. One or more embodiments relate to a method for enhancing a multi-step chemical conversion reaction. The method includes providing a reactant mixture comprising one or more reacting specie(s); and providing a catalyst or sorbent comprising one or more support materials and one or more deposited catalytically active materials. The method further includes applying an electromagnetic field with a prescribed power, frequency, and pulsing strategy specific to interactions of reactant species and an electromagnetic field with at least one of the support materials, sorbent, and catalytically active materials in a particular chemical reaction.

Shekhawat, Dushyant↗
DOE OSTI2026

Adaptive spectra-to-exposure conversion using ridge regularized polynomial response models

Real-time gamma spectra-to-exposure conversion in aerial and ground monitoring commonly relies on calibration-derived, detector- or system-specific conversion coefficients that are assumed to generalize across operational environments. In practice, deployment specific differences in spectral composition and transport conditions can introduce systematic bias relative to reference instruments, motivating methods that adapt coefficients using minimal field supervision while explicitly limiting overfitting. In this work, we present a conservative coefficient adaptation framework that updates a baseline polynomial energy-weighting function using ridge-regularized regression, with leave-one-out cross-validation (LOOCV) used to select the regularization strength. The findings support ridge-constrained minimal-supervision adaptation as a practical mechanism to suppress site-specific bias without destabilizing a calibration-derived baseline.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2025

A modeling study of ocean thermal energy conversion resource and potential environmental effects around Kailua-Kona, Hawaii

Ocean Thermal Energy Conversion (OTEC) offers a promising renewable energy solution through a heat exchange process using the temperature difference between warm surface seawater and cold deep seawater. Because accurate resource characterization is critical for the optimal design and implementation of OTEC systems, a high-resolution numerical model is employed to better characterize the OTEC resource at Kona, Hawaii. Our model provides detailed spatial and temporal variability of the thermal gradient, which is essential for assessing the viability and efficiency of OTEC systems. The model results reveal distinct patterns and dynamics not captured by existing observations or models (e.g., lower-resolution information). These findings highlight the importance of using high-resolution models for accurate predictions of thermal gradient variability, ultimately supporting more efficient and sustainable OTEC deployment. Additionally, the study investigates the impacts of mixed water discharge from OTEC plants that can cause shock to organisms living in the surface water and potentially destabilize the water column. Understanding these effects is vital for minimizing any potential negative environmental consequences and ensuring the long-term viability of OTEC operations. Further, our model improves OTEC resource characterization, which can lead to optimal design and deployment of OTEC systems. The analysis of OTEC water discharge impacts can accelerate the development of OTEC technologies, overcoming permitting/consenting challenges. These findings contribute to the broader adoption of high-resolution modeling in ocean energy resource characterization, particularly for OTEC applications.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2026

The Chemistry of CO 2 Conversion: A Review

For much of the past century, carbon dioxide (CO 2 ) has received little attention scientifically outside of its role as a byproduct in the industrialization of the global economy. This trend has recently been upended where, due to mounting environmental concerns, CO 2 has been brought squarely into the public consciousness. This surge in activity has contributed to a once unimaginable idea now pervading the scientific community: could CO 2 , a highly stable byproduct of hydrocarbon combustion, be recycled and converted back into useful chemicals and fuels? Owing to its ubiquitous nature and availability at truly massive quantities, it is thought that CO 2 -based products could offer a meaningful pathway toward lowering the environmental impact of many of the top industrial products while also enhancing supply chain diversification and resilience. In this manuscript we provide a holistic review of the pathways for CO 2 conversion, the underlying chemistry and challenges involved in the transformation to products, and considerations for commercialization.

09 BIOMASS FUELS↗
DOE OSTI2024

Electrochemical CO 2 Conversion Commercialization Pathways: A Concise Review on Experimental Frontiers and Technoeconomic Analysis

Technoeconomic analysis (TEA) studies are vital for formulating guidelines that drive the commercialization of electrochemical CO 2 reduction (eCO 2 R) technologies. In this review, we first discuss the progress in the field of eCO 2 R processes by providing current state-of-the-art metrices (e.g., faradic efficiency, current density) based on the recent heterogeneous catalysts’ discovery, electrolytes, electrolyzers configuration, and electrolysis process designs. Next, we assessed the TEA studies for a wide range of eCO 2 R final products, different modes of eCO 2 R systems/processes, and discussed their relative competitiveness with relevant commercial products. Finally, we discuss challenges and future directions essential for eCO 2 R commercialization by linking suggestions from TEA studies. We believe that this review will catalyze innovation in formulating advanced eCO 2 R strategies to meet the TEA benchmarks for the conversion of CO 2 into valuable chemicals at the industrial scale.

54 ENVIRONMENTAL SCIENCES↗