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At least 469 records · Page 26

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NASA NTRS2008

5-kWe Free-piston Stirling Engine Convertor

The high reliability, long life, and efficient operation of Free-Piston Stirling Engines (FPSEs) make them an attractive power system to meet future space power requirements with less mass, better efficiency, and less total heat exchanger area than other power convertor options. FPSEs are also flexible in configuration as they can be coupled with many potential heat sources and various heat input systems, heat rejection systems, and power management and distribution systems. Development of a 5-kWe Stirling Convertor Assembly (SCA) is underway to demonstrate the viability of an FPSE for space power. The design is a scaled-down version of the successful 12.5-kWe Component Test Power Converter (CTPC) developed under NAS3-25463. The ultimate efficiency target is 25% overall convertor efficiency (electrical power out over heat in). For the single cylinder prototype now in development, cost and time constraints required use of economical and readily available materials (steel versus beryllium) and components (a commercially available linear alternator) and thus lower efficiency. The working gas is helium at 150 bar mean pressure. The design consists of a displacer suspended on internally pumped gas bearings and a power piston/alternator supported on flexures. Non-contacting clearance seals are used between internal volumes. Heat to and from the prototype convertor is done via pumped liquid loops passing through shell and tube heat exchangers. The preliminary and detail designs of the convertor, controller, and support systems (heating loop, cooling loop, and helium supply system) are complete and all hardware is on order. Assembly and test of the prototype at Foster- Miller is planned for early 2008, when work will focus on characterizing convertor dynamics and steady-state operation to determine maximum power output and system efficiency. The device will then be delivered to Auburn University where assessments will include start-up and shutdown characterization and transient response to temperature and load variations. Future activities may include testing at NASA GRC.

Chapman, Peter A.↗

NASA NTRSDate not supplied

Assessment of the Impact of an Advanced Power System on a Turboelectric Single-Aisle Concept Aircraft

Electrified aircraft propulsion concepts show potential in using propulsion airframe inte-gration in order to increase efficiency in flight and therefore decrease fuel burn and emissions.Electrification offers component efficiency values greater than 90 percent, but the loss is in the form of low grade waste heat. A major challenge of electrified aircraft propulsion is managing that heat while minimizing any penalties associated with a thermal management system. This paper explores the effect of two innovations in the management of waste heat at the aircraft system level for a turboelectric single aisle concept. The first innovation is achieving a 3 times reduction in heat by developing high-efficiency components rather than managing the high levels of heat. The second takes advantage of the outer mold line of the aircraft to reject heat directly to the environment passively instead of adding active cooling loops that negatively impact the weight, power, and drag of the aircraft. In order to fully grasp the impact of the advanced power system, we develop methods of modeling the power and thermal management systems to be integrated in the full aircraft conceptual model. We then model the aircraft with a state of the art DC transmission system and active cooling loops as a baseline for our study. Our second model includes the advanced power system with active cooling, which results in a fuel burn reduction of 2.5 percent. Finally, in our third model we assess the benefit of an outer mold line cooling scheme with the advanced power system. The outer mold line cooling scheme with an advanced power system yields an additional 0.8 percent reduction in fuel burn,for an overall fuel burn reduction potential of 3.3 percent in addition to aerodynamic benefits of electrified aircraft propulsion.

Electric Aircraft↗

DOE OSTI2024

Exploring Interferometry Diagnostics for Optical Stochastic Cooling at FAST/IOTA

Optical Stochastic Cooling (OSC) is an advanced beam-cooling technique that will precede the traditional stochastic cooling. This method leverages optical radiation and high-precision feedback to cool the particles more efficiently than traditional stochastic methods by more than three orders of magnitude. As such, it is an enabler for the development of next generation discovery science machines at the frontiers of energy and intensity. This paper focuses on the development of the second phase of OSC and improving extreme beam cooling technique in accelerators. Along with the assembly and use of an interferometer to provide diagnostics and optimization to OSC systems. The interferometer can allow for the observation and analysis of fringe patterns from a recreated simpler version in the laser room. By leveraging interferometric techniques, OSC can achieve higher efficiency, verification, stability and performance.

Teriba, Folashade↗

DOE OSTI2023

Accelerating Adoption of Energy-Efficient Technology with the Thermalize Model

The accelerating impacts of climate change destabilize food systems and ecosystems alongside the communities that rely on them. Thus, climate resilience is a health equity issue at both a physical (relating to biological impacts of pollution and environmental degradation) and a cultural level (loss of subsistence lifestyles, languages, etc). With roughly 20% of US energy-related greenhouse gas emissions stemming from heating, cooling, and powering households, accessible energy-efficient home retrofits are a critical element of climate change mitigation strategies. For communities already producing electricity from renewable sources, like Juneau, incentivizing ductless heat pump upgrades and energy efficiency retrofits provides an accessible pathway to transition households away from oil heating and drastically reduce emissions. Thermalize Juneau is a pilot program that will explore a repeatable framework for accelerating the adoption of energy-efficient technology in Alaska communities. This poster will describe Thermalize Juneau's goals and framework, progress through spring 2021, and future plans.

ductless heat pumps↗

NASA NTRS1998

Performance of the CELSS Antarctic Analog Project (CAAP) Crop Production System

Regenerative life support systems potentially offer a level of self-sufficiency and a concomitant decrease in logistics and associated costs in support of space exploration and habitation missions. Current state-of-the-art in plant based, regenerative life support requires resources in excess of resource allocations proposed for candidate mission scenarios. Feasibility thresholds have been identified for candidate exploration missions. The goal of this paper is to review recent advances in performance achieved in the CELSS Antarctic Analog Project (CAAP) in light of likely resource constraints. A prototype CAAP crop production chamber has been constructed and operated at the Ames Research Center. The chamber includes a number of unique hardware and software components focused on attempts to increase production efficiency, increase energy efficiency, and control the flow of energy and mass through the system to achieve enhanced performance efficiency. Both single crop, batch production, and continuous cultivation of mixed crops Product ion scenarios have been completed. The crop productivity as well as engineering performance of the chamber will be described. For each scenario, energy required and partitioned for lighting, cooling, pumps, fans, etc. is quantified. Crop production and the resulting lighting efficiency and energy conversion efficiencies are presented. In the mixed-crop scenario, with up to 25 different crops under cultivation, 17 sq m of crop area provided a mean of 515 g edible biomass per day (83% of the approximately 620 g required for one person). Lighting efficiency (moles on photons kWh-1) approached 4 and the conversion efficiency of light energy to biomass was greatly enhanced compared with conventional growing systems. Engineering and biological performance achieved place plant-based life support systems at the threshold of feasibility.

Bubenheim, David L.↗

DOE OSTI2025

A dynamic 2D Borehole Thermal Energy Storage (BTES) model for enhanced computational efficiency

Progressing toward a future increasingly reliant on renewable energy sources, the development of effective, durable energy storage solutions becomes essential to balance supply and demand fluctuations. Borehole Thermal Energy Storage (BTES) is a long-duration thermal energy storage technology that captures excess heat generated from renewable energy sources and stores it underground for later use, enabling the efficient utilization of sustainable energy. This approach is particularly valuable in district energy networks when integrated with Ground Source Heat Pumps (GSHP) to provide stable heating and cooling. However, traditional three-dimensional (3D) numerical models of BTES systems demand extensive computational resources, limiting their practicality for real-time and large-scale applications. This study introduces a novel two-dimensional (2D) modeling approach that reduces computational costs while maintaining high accuracy. By employing a radial ring-based discretization method, the model simulates heat injection, retention, and retrieval dynamics over seasonal cycles. A new thermal-mass weighted-average temperature parameter is introduced to evaluate the performance of BTES systems. Model validation against FEFLOW simulations demonstrates a 17-fold improvement in computational speed compared to traditional Computational Fluid Dynamics (CFD) models while achieving a mean absolute percentage error (MAPE) of 2 % during charging and 4 % during discharging. Additionally, a trade-off analysis between computational efficiency and accuracy is conducted, ensuring the model's applicability for real-world scenarios. The findings of this research contribute to the development of computationally efficient BTES models, facilitating better optimization, control, and integration into renewable energy systems. This work provides a foundation for further studies in techno-economic analysis, multi-year performance evaluation, and real-time operational strategies for BTES applications, supporting a more sustainable energy future.

2D modeling↗

DOE OSTI2021

Advanced Water-Related Technology Performance Development

This U.S. Department of Energy/National Energy Technology Laboratory techno-economic analysis evaluates those parameters having the greatest performance and cost impact on wet flue gas desulfurization (FGD) effluent wastewater treatment systems, and air cooled condensers for dry cooling systems. Two supercritical pulverized coal power plants are considered: 1) an existing plant (modified for surface water discharge and air emissions consistent with limits for existing plants) retrofitted with wet FGD effluent wastewater treatment and 2) a greenfield plant constructed with an air-cooled condenser (ACC). Sensitivity analyses are completed on various process parameters associated with the wet FGD effluent wastewater treatment system and ACC to determine the impact on the net plant efficiency and levelized cost of electricity (LCOE). Research and development targets are recommended for the parameters shown to have the greatest potential impact on cost or performance.

20 FOSSIL-FUELED POWER PLANTS↗

DOE OSTI2023

FWP FEAA149: “Next Generation Environmental Barrier Coatings”

Environmental barrier coatings (EBCs) are required coatings for utilization of SiC/SiC ceramic matrix composite (CMC) components in gas turbines, where the EBC represents the life-limiting factor for such components. EBC/CMC systems have shown success in aero-engine applications with increased turbine inlet temperatures and improved efficiencies, which are achieved through higher temperature stability, lower density, and decreased reliance on cooling air compared to traditional superalloys. While industrial gas turbines (IGTs) do not currently utilize SiC/SiC CMCs, the current shift towards low-carbon or carbon-free fuel sources for power generation could result in a need for EBC/CMC components with higher temperature capabilities. In this work, three tasks were outlined to improve understanding of EBC lifetimes to encourage use in IGTs with carbon-free fuel such as hydrogen: 1. Define the bond coating oxidation kinetics and EBC failure criteria, 2. Measure thermal expansion coefficients of each layered material, and 3. Perform advanced characterization and modeling to assess EBC lifetimes. Cyclic steam oxidation tests were conducted on various EBC/Si/SiC chemistries and EBC/SiC architectures to define substrate oxidation kinetics and EBC failure modes. An open-source code was developed to quantify the undulating thermally grown oxide thickness with thousands of measurements from specimen cross-section images. Bond coating oxidation kinetics were determined and used to develop a kinetic and thermodynamic model for predicting EBC lifetimes. High-temperature Raman spectroscopy was utilized for determining the SiO 2 thermally grown oxide phase transformation as the life-limiting feature for EBCs. Model efforts supported the claim that the SiO 2 phase transformation causes elevated stress during thermal cycling with associated cracking that decreases the adhesion strength of the EBC, eventually resulting in coating spallation. The finite element model subroutine will be made publicly available upon internal review. Further development of an EBC lifetime model for IGTs involves definition of a critical SiO 2 thickness for EBC spallation and must also consider both environmental (gas velocity, pressure, etc.) and specimen (EBC dopants, layer architectures, etc.) effects into predicted bond coating oxidation kinetics for long-lifetime components.

36 MATERIALS SCIENCE↗

NASA NTRS1975

Performance simulation for the design of solar heating and cooling systems

Suitable approaches for evaluating the performance and the cost of a solar heating and cooling system are considered, taking into account the value of a computer simulation concerning the entire system in connection with the large number of parameters involved. Operational relations concerning the collector efficiency in the case of a new improved collector and a reference collector are presented in a graph. Total costs for solar and conventional heating, ventilation, and air conditioning systems as a function of time are shown in another graph.

Mccormick, P. O.↗

NASA NTRS1978

Effect of thermal barrier coatings on the performance of steam and water-cooled gas turbine/steam turbine combined cycle system

An analytical study was made of the performance of air, steam, and water-cooled gas-turbine/steam turbine combined-cycle systems with and without thermal-barrier coatings. For steam cooling, thermal barrier coatings permit an increase in the turbine inlet temperature from 1205 C (2200 F), resulting in an efficiency improvement of 1.9 percentage points. The maximum specific power improvement with thermal barriers is 32.4 percent, when the turbine inlet temperature is increased from 1425 C (2600 F) to 1675 C (3050 F) and the airfoil temperature is kept the same. For water cooling, the maximum efficiency improvement is 2.2 percentage points at a turbine inlet temperature of 1683 C (3062 F) and the maximum specific power improvement is 36.6 percent by increasing the turbine inlet temperature from 1425 C (2600 F) to 1730 C (3150 F) and keeping the airfoil temperatures the same. These improvements are greater than that obtained with combined cycles using air cooling at a turbine inlet temperature of 1205 C (2200 F). The large temperature differences across the thermal barriers at these high temperatures, however, indicate that thermal stresses may present obstacles to the use of coatings at high turbine inlet temperatures.

Nainiger, J. J.↗

NASA NTRS1989

Heat pipes for low-humidity applications

A novel application of an air-to-air heat pipe heat exchanger (HPHX) in a cooling and dehumidification process of an air-conditioning system is described which provides significant energy savings in applications requiring reheat of cold supply air to maintain low humidity. The efficiency of the system has been demonstrated in an application requiring a humidity of 40 percent. The use of the HPHX and fine tuning of the air-conditioning system and controls has resulted in significant energy savings. The technology can be advantageously used in many low-humidity applications commonly encountered in high-tech and aerospace facilities.

Khattar, Mukesh K.↗

NASA NTRS1997

An Initial Multi-Domain Modeling of an Actively Cooled Structure

A methodology for the simulation of turbine cooling flows is being developed. The methodology seeks to combine numerical techniques that optimize both accuracy and computational efficiency. Key components of the methodology include the use of multiblock grid systems for modeling complex geometries, and multigrid convergence acceleration for enhancing computational efficiency in highly resolved fluid flow simulations. The use of the methodology has been demonstrated in several turbo machinery flow and heat transfer studies. Ongoing and future work involves implementing additional turbulence models, improving computational efficiency, adding AMR.

Steinthorsson, Erlendur↗

NASA NTRS1999

The Astro-E High Resolution X-Ray Spectrometer

The Astro-E High Resolution X-ray Spectrometer (XRS) was developed jointly by the NASA/Goddard Space Flight Center and the Institute of Space and Astronautical Science in Japan. The instrument is based on a new approach to spectroscopy, the X-ray microcalorimeter. This device senses the energies of individual X-ray photons as heat with extreme precision. A 32 channel array of microcalorimeters is being employed, each with an energy resolution of about 12 eV at 6 keV (the Fe-K region). This will provide spectral resolving power 10 times higher than any other non-dispersive X-ray spectrometer. The instrument incorporates a three stage cooling system capable of operating the array at 60 mK for about two years in orbit. The array sits at the focus of a grazing incidence conical mirror. The quantum efficiency of the microcalorimeters and the reflectivity of the X-ray mirror system combine to give high throughput over the 0.3-12 keV energy band. This new capability will enable the study of a wide range of high-energy astrophysical sources with unprecedented spectral sensitivity. This paper presents the basic design requirements and implementation of the XRS, and also describes the instrument parameters and performance.

Kelley, Richard L.↗

NASA NTRS1995

A Unique Facility For Metabolic and Thermoregulatory Studies

A unique exercise facility has been developed and used to perform tipper body ergometry tests for space applications. Originally designed to simulate the muscular, cardiovascular and thermoregulatory responses to working in zero gravity, this facility may be used to conduct basic thermoregulatory investigations applicable to multiple sclerosis patients. An environmental chamber houses the tipper body ergometer and permits control of temperature, air now and humidify. The chamber is a closed system and recirculate-s air after conditioning if. A Cybex Lipper body ergometer has been mounted horizontally on the wall of the environmental chamber. In this configuration, the subject lies underneath the arm crank on a supine seat in order to turn the crank. The supine seat can be removed in order to introduce other equipment into the chamber such as a stool to allow upright arm cranking, or a treadmill to allow walk-run experiments. Physiological and environmental signals are fed into a Strawberry Tree data acquisition system while being monitored and logged using the Workbench software program. Physiological monitoring capabilities include 3-lead EKG using an H-P patient monitor, 5 site skin temperature and core temperature using YSI thermistors, and O2 consumption and CO2 production using AMFTFK Applied Electrochemistry analyzers and sensors. This comprehensive data acquisition set tip allows for calculation of various thermoregulatory indices including heat storage, evaporative heat loss, latent heat loss, and metabolic rate. The current system is capable of adding more data acquisition channels if needed. Some potential studies that could be carried out using the facility include: 1) An investigation into the efficiency of cooling various segments of the body to lower Tc 1-2 F. 2) A series of heat and mass balance studies comparing various LCG configurations.

Williamson, Rebecca C.↗

NASA NTRS2007

Heat Transfer Analysis of a Closed Brayton Cycle Space Radiator

This paper presents a mathematical analysis of the heat transfer processes taking place in a radiator for a closed cycle gas turbine (CCGT), also referred to as a Closed Brayton Cycle (CBC) space power system. The resulting equations and relationships have been incorporated into a radiator sub-routine of a numerical triple objective CCGT optimization program to determine operating conditions yielding maximum cycle efficiency, minimum radiator area and minimum overall systems mass. Study results should be of interest to numerical modeling of closed cycle Brayton space power systems and to the design of fluid cooled radiators in general.

Juhasz, Albert J.↗

NASA NTRS2012

Terrestrial Applications of Extreme Environment Stirling Space Power Systems

NASA has been developing power systems capable of long-term operation in extreme environments such as the surface of Venus. This technology can use any external heat source to efficiently provide electrical power and cooling; and it is designed to be extremely efficient and reliable for extended space missions. Terrestrial applications include: use in electric hybrid vehicles; distributed home co-generation/cooling; and quiet recreational vehicle power generation. This technology can reduce environmental emissions, petroleum consumption, and noise while eliminating maintenance and environmental damage from automotive fluids such as oil lubricants and air conditioning coolant. This report will provide an overview of this new technology and its applications.

Dyson, Rodger. W.↗

DOE OSTI2020

High-Temperature Heat Transfer Fluid Circulator for Concentrating Solar Power Systems

Concentrating Solar Power (CSP) plants with Thermal Energy Storage (TES), require compressors capable of circulating supercritical carbon dioxide (sCO2) heat transfer fluids (HTFs) at temperatures from 500 to 700+°C and pressures from 8 to 25 MPa (80 to 250 Bar or 1160 to 3626 psia) in order to achieve thermal-to-electric efficiencies >50%. A review of papers relating to SCO2 compressors reveals that in almost every case the conditions being considered either allow for cooling of the SCO2 working fluid or are considering operating conditions close to the critical point at a temperature and pressure of approximately 31°C and 1070 psi). While the technology reported in these papers is relevant to most turbomachinery, the current CSP gas pathway circulator operating pressures are well above the CO2 critical point and do not allow for cooling of the main HTF flow. The purpose of this paper was to describe the key system issues affecting the design of a HTF circulator that could be scaled from a small size research and proof of concept circulator compressor to sizes supporting power plants producint upwards of 100 to 300 Mega Watts of electrical power. Due to the high temperatures and pressures the research scale HTF circulator was designed to be hermetically sealed to prevent leakage of the super critical carbon dioxide to the environment. In order to achieve hermetic sealing the drive motor and centrifugal impeller were fully integrated in a single shaft system configuration. From a preliminary assessment of compression power as a function of operating speed and impeller diameter it was determined that a smaller, higher speed impeller would result in a more efficient circulator. However, due to the high pressure and corresponding density of the sCO2 coupled with high operating speeds, large windage losses (i.e., viscous drag on the high speed rotating shaft) would occur which could result in a substantial reduction in efficiency of the system. Therefore tradoff studies were complerted to identify the operating speeds and system component sizes to achieve high efficiency. Based on the trade studies, the final design was a 55 mm diamter compressor impeller operating at speeds to 85,000 rpm. The unit will be built and tested in the future. Key Words: Super Critical Carbon Dioxide, Heat Transfer Fluid, Turbomachinery, Compressor, Circulator, Critical Point, Concentrating Solar Power, Solar Energy

Super Critical Carbon Dioxide, Heat Transfer Fluid↗

NASA NTRS1977

The design of a solar energy collection system to augment heating and cooling for a commercial office building

Analytical studies supported by experimental testing indicate that solar energy can be utilized to heat and cool commercial buildings. In a 50,000 square foot one-story office building at the Langley Research Center, 15,000 square feet of solar collectors are designed to provide the energy required to supply 79 percent of the building heating needs and 52 percent of its cooling needs. The experience gained from the space program is providing the technology base for this project. Included are some of the analytical studies made to make the building design changes necessary to utilize solar energy, the basic solar collector design, collector efficiencies, and the integrated system design.

Basford, R. C.↗