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At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Field Demonstration and Adoption Impacts of an Affordable Thermoelectric Heat Pump

This study presents the design, field validation, and utility impacts of an air source heat pump that uses thermoelectric (TE) technology to provide supplemental heating at outside air temperatures below 17°F. Conventional heat pumps experience reduced heating capacity and COP at low outdoor temperatures due to the temperature difference between the source and demand sides of the vapor compression cycle. Consequently, during colder months, supplemental heating such as electric resistance or natural gas furnace is often needed to provide additional warmth, which increases the overall equipment and energy costs. To address this challenge, a TE subcooler (an array of solid-state, thermoelectric modules that provides heat pumping using non-vapor compression technique) is fabricated and integrated with the vapor compression cycle of a conventional air-source heat pump. In colder ambient conditions, TE subcooler exchanges heat with the refrigerant to provide additional subcooling, thereby enhancing the capacity of the heat pump. The operation of thermoelectric-integrated heat pump was demonstrated in an occupied single-family home in Nashville, TN. The TE subcooler increased the system’s heating capacity at 15°F outdoor temperature by 25–30% and reduced electricity demand by 10%. It also met the heating load in the house without supplemental electric resistance down to 5°F outdoors, delivering the additional heat at nearly 80% greater efficiency compared to electric resistance heating. With a modest first cost increment of 10–15% over conventional single-speed heat pumps, this approach offers a promising, energy-efficient solution to accelerate residential heat pump adoption in the U.S.

KRISHNAMOORTHY, Sreenidhi [Electric Power Research↗
NASA NTRS2010

Optical Sidebands Multiplier

Optical sidebands have been generated with relative frequency tens to hundreds of GHz by using optical sidebands that are generated in a cascade process in high-quality optical resonators with Kerr nonlinearity, such as whispering gallery mode (WGM) resonators. For this purpose, the WGM resonator needs to be optically pumped at two frequencies matching its resonances. These two optical components can be one or several free spectral ranges (FSRs), equal to approximately 12 GHz, in this example, apart from each other, and can be easily derived from a monochromatic pump with an ordinary EOM (electro-optic modulation) operating at half the FSR frequency. With sufficient nonlinearity, an optical cascade process will convert the two pump frequencies into a comb-like structure extending many FSRs around the carrier frequency. This has a demonstratively efficient frequency conversion of this type with only a few milliwatt optical pump power. The concept of using Kerr nonlinearity in a resonator for non-degenerate wave mixing has been discussed before, but it was a common belief that this was a weak process requiring very high peak powers to be observable. It was not thought possible for this approach to compete with electro-optical modulators in CW applications, especially those at lower optical powers. By using the high-Q WGM resonators, the effective Kerr nonlinearity can be made so high that, using even weak seeding bands available from a conventional EOM, one can effectively multiply the optical sidebands, extending them into an otherwise inaccessible frequency range.

Strekalov, Dmitry V.↗
DOE OSTI2026

ResStock Measure Documentation: Residential Two-Stage Geothermal Heat Pump (4.0 COP, 20.5 EER) With Light Envelope Improvements

This report is part of series describing a variety of different ResStock(TM) measures. "Measures" refers to energy efficiency retrofits that can be applied to buildings during modeling. This documentation covers the "Residential Two-Stage Geothermal Heat Pump (4.0 COP, 20.5 EER) With Light Envelope Improvements" measure upgrade methodology and briefly discusses key results. All results can be accessed on the ResStock Open Energy Data Initiative "End-Use Load Profiles for the U.S. Building Stock" data lake and on the data viewer at resstock.nlr.gov.

15 GEOTHERMAL ENERGY↗
DOE OSTI2026

Virtual refrigerant charge sensing algorithm for residential CO₂ heat pumps

Natural refrigerants are increasingly adopted in next-generation heat pump systems, among which CO₂ heat pumps have attracted significant attention. However, due to their high operating pressures, the leakage risk is higher, resulting in undercharge conditions and degraded heat pump performance. Thus, developing an accurate refrigerant charge level detection technique is necessary to guarantee safe and efficient operation. Although virtual refrigerant charge (VRC) level calculation algorithms for CO₂ heat pumps exist, they typically rely on empirically selected features without a systematic selection framework, leading to multicollinearity and potential overfitting, which limit their prediction accuracy and generalizability. To address these issues, this study proposes a VRC algorithm framework with a systematic feature selection method that identifies physically meaningful and statistically significant features, and is applied using a residential CO₂ heat pump as a case study. The method is extended from previous work on conventional refrigerants to account for charge behavior in CO₂ gas coolers. The selected features include gas cooler outlet density, evaporator pressure, and superheat temperature. The results demonstrate that the proposed feature selection method significantly improves prediction accuracy compared to existing VRC approaches. A relatively small training dataset (∼30 samples) is sufficient for feature identification and model development. The developed algorithm achieves less than 3% prediction error under both undercharge and overcharge conditions, representing reductions of 46.7% and 35.3% compared to two recent reference VRC algorithms for transcritical CO₂ heat pumps reported in the literature. The proposed algorithm and feature selection method enhance leakage detection capability, facilitate the deployment of CO₂ heat pump systems, and contribute to reduced energy waste and maintenance costs.

Guo, Fangzhou [Lawrence Berkeley National Laborato↗
NASA NTRS2007

Efficient Dual Head Nd:YAG 100mJ Oscillator for Remote Sensing

A diode pumped, Nd:YAG laser producing 100 mJ Q-switched pulses and employing a dual-pump head scheme in an unstable resonator configuration is described. Each head contains a side pumped zig-zag slab and four 6-bar QCW 808 nm diodes arrays which are de-rated 23%. Denoting 'z' as the lasing axis, the pump directions were along the x-axis in one head and the y-axis in the other, producing a circularized thermal lens, more typical in laser rod-based cavities. The dual head design's effective thermal lens is now corrected with a proper HR mirror curvature selection. This laser has demonstrated over 100 mJ output with high optical efficiency (24%), good TEM(sub 00) beam quality, and high pointing stability.

Coyle, Donald B.↗
NASA NTRS1979

Solar-pumped lasers for space power transmission

Multi-Megawatt CW solar-pumped lasers appear to be technologically feasible for space power transmission in the 1990s time frame. A new concept for a solar-pumped laser is presented which utilizes an intermediate black body cavity to provide a uniform optical pumping environment for the lasant, either CO or CO2. Reradiation losses are minimized with resulting high efficiency operation. A 1 MW output laser may weigh as little as 8000 kg including solar collector, black body cavity, laser cavity and ducts, pumps, power systems and waste heat radiator. The efficiency of such a system will be on the order of 10 to 20%. Details of the new concept, laser design, comparison to competing solar-powered lasers and applications to a laser solar power satellite (SPS) concept are presented.

Taussig, R.↗
NASA NTRS2001

Experimental Investigation of Local Oscillator Chains with GaAs Planar Diodes at Cryogenic Temperatures

This paper will describe a robust test-bed that has been built to measure multiplier performance over a wide range of temperatures and frequencies. In a 182-212 GRz designed balanced doubler the peak efficiency at 201 GHz improves from 22% to 28% upon cooling from 300 K to 120 K. This stage is then used to pump a 362-424 GRz balanced planar doubler. The peak chain efficiency increases from 3.4% to 6% when the two cascaded doublers are cooled from 300 K to 120 K. This enables the production of 10 mW of peak output power at 377 GHz, which ought to be sufficient for driving the next stage multiplier.

Maestrini, A.↗
NASA NTRS1988

Characterization of a centrifugal pump in He II

As part of an effort to determine the feasibility of helium transfer in space, a centrifugal pump was tested in He II at a variety of flow rates, pump speeds, and fluid temperatures. The pump, which has a straight bladed impeller 6.86 cm in diameter, generated a maximum pressure rise of 15 kPa and a maximum flow rate of 22 g/s for the conditions of the test. Pump performance seems to be independent of fluid temperature and is in good agreement with the values predicted by the manufacturer. Over the range of flow coefficients, the measured maximum efficiency is around 50 percent. Cavitation is observed in the pump and is thought to be highly dependent on the local heating of the helium in the pump. Preliminary measurements of the noise spectra of the pump suggest a possible mechanism to predict the onset of cavitation.

Weisend, J. G., II↗
DOE OSTI2020

Smart technologies enable homes to be efficient and interactive with the grid

Oak Ridge National Laboratory researchers compare two different approaches to test how advanced, energy-efficient building technologies such as smart thermostats, heat pump water heaters, and advanced heat pump HVAC (heating, ventilation and air conditioning) can be optimized within a home and connected at a neighborhood-scale load to a community microgrid in the Alabama Power Smart Neighborhood located in Hoover. Working with Southern Company and Alabama Power, ORNL researchers are pioneering that future where smart homes and smart neighborhoods can benefit both homeowners and utilities, by reducing energy consumption by 44% and peak demand by 34%.This project is one of two neighborhoods in the U.S Department of Energy’s (DOE’s) Connected Neighborhood project, supported by Building Technologies Office , where ORNL researchers leverages DOE investment in micro-grids and responsive, flexible building loads research to improve grid reliability – a goal of DOE’s Grid-interactive Efficient Buildings (GEB) Initiative. Researchers control the neighborhood and microgrid to enable utilities achieve their desired load and cost profiles while ensuring the comfort of homeowners in the Smart Neighborhood. This transactive control approach maximizes the utilization of technical resources of the microgrid and controllable loads, while reducing costs for both the homeowners and Alabama Power. These tests partially seek to determine a more precise range of tolerance with respect to occupant comfort as researchers work to facilitate customer acceptance and perception of new building technologies that enable energy savings.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS2010

Performance Testing of a Prototypic Annular Linear Induction Pump for Fission Surface Power

Results of performance testing of an annular linear induction pump are presented. The pump electromagnetically pumps liquid metal (NaK) through a circuit specially designed to allow for quantification of the performance. Testing was conducted over a range of conditions, including frequencies of 33, 36, 39, and 60 Hz, liquid metal temperatures from 25 to 525 C, and input voltages from 5 to 120 V. Pump performance spanned a range of flow rates from roughly 0.16 to 5.7 L/s (2.5 to 90 gpm), and pressure head <1 to 90 kPa (<0.145 to 13 psi). The maximum efficiency measured during testing was slightly greater than 6%. The efficiency was fairly insensitive to input frequency from 33 to 39 Hz, and was markedly lower at 60 Hz. In addition, the efficiency decreased as the NaK temperature was raised. While the pump was powered, the fluid responded immediately to changes in the input power level, but when power was removed altogether, there was a brief slow-down period before the fluid would come to rest. The performance of the pump operating on a variable frequency drive providing 60 Hz power compared favorably with the same pump operating on 60 Hz power drawn directly from the electrical grid.

Polzin, K. A.↗
DOE OSTI2021

A robust plasma-based laser amplifier via stimulated Brillouin scattering

Brillouin amplification in plasma is more resilient to fluctuations in the laser and plasma parameters than Raman amplification, making it an attractive alternative to Raman amplification. In this work, we focus on high plasma densities, n 0 > n cr /4, where stimulated Raman scattering is not possible and laser beam filamentation is the dominant competing process. Through analytic theory and multi-dimensional particle-in-cell simulations, we identify a parameter regime for which Brillouin amplification can be efficient while maintaining filamentation of the probe at a controlled level. We demonstrate pump-to-probe compression ratios of up to 72 and peak amplified probe fluences over 1 kJ cm -2 with ≃50% efficiency. High pulse quality is maintained through control of parasitic filamentation, enabling operation at large beam diameters. Provided the pump and probe pulse diameters can be increased to 1 mm, our results suggest that Brillouin amplification can be used to produce sub-picosecond pulses of petawatt power.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Validated model of a thermoelectric heat pump clothes dryer using secondary pumped loops

The energy associated with clothes drying makes up 4% of the total residential electrical energy consumption in the US. The cost is high since most clothes dryers use electric resistance heating which is inexpensive but also energy inefficient. State-of-the-art vapor-compression heat pump clothes dryers offer significant energy savings but have limited market penetration in the US. Here, a new configuration of clothes dryer was studied that utilizes a solid-state thermoelectric heat pump with pumped secondary water loops and conventional fin-and-tube water-to-air heat exchangers. Experimental results are presented for the thermoelectric dryer prototype with a combined energy factor of 6.89 lb BDW /kWh (specific moisture extraction rate of 1.71 kg w /kWh) and a dry time of 84 min for a standard load size of 8.45 lb (3.83 kg) with 57.5% starting moisture content. This is a 85% energy efficiency improvement over baseline electric resistance dryers. The efficiency and drying time results achieved are similar to vapor compression heat pump dryers. Compared to previous air-based thermoelectric clothes dryers, the energy efficiency has been increased by 6%, but drying time has been reduced by as much as 47% using secondary pumped loops and separate heat exchangers, which represents a significant advancement in the technology. In addition to the experimental prototype, a model was also developed to study the performance. The model was validated against experimental prototype data and used to identify the range of performance (dry time and efficiency) that could be expected of the design.

42 ENGINEERING↗
DOE OSTI2024

Phase control of spin waves in the van der Waals antiferromagnet NiPS 3

Here we demonstrate phase control of magnons in the van der Waals antiferromagnet NiPS3 using optical excitation by polarized light. The sign of the coherent precession of spin amplitude changes upon (i) reversing the helicity of a circularly polarized pump beam, or (ii) rotating the polarization of a linearly polarized pump by π/2. Because these two excitation pathways have comparable generation efficiency, the phase of spin precession can be continuously tuned from 0 to 2π by controlling the polarization state of the pump pulse. The ability to excite magnons with a desired phase has potential applications in the design of a spin-wave phased array and ultrafast spin information processing.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Sustainable Energy Solutions for Thermal Load in Buildings—Role of Heat Pumps, Solar Thermal, and Hydrogen-Based Cogeneration Systems

Economic and population growth is leading to increased energy demand across all sectors—buildings, transportation, and industry. Adoption of new energy consumers such as electric vehicles could further increase this growth. Sensible utilization of clean renewable energy resources is necessary to sustain this growth. Thermal needs in a building pose a significant challenge to the energy infrastructure. Potential technological solutions to address growing energy demand while simultaneously lowering the carbon footprint and enhancing the grid flexibility are presented in this study. Performance assessment of heat pumps, solar thermal collectors, nonfossil fuel-based cogeneration systems, and their hybrid configurations is reported in this study. The impact of design configuration, coefficient of performance (COP), electric grid’s primary energy efficiency on the key attributes of total carbon footprint, life cycle costs, operational energy savings, and site-specific primary energy efficiency are analyzed and discussed in detail. In conclusion, heat pumps and hydrogen-fueled solid oxide fuel cells (SOFCs) are highly effective building energy resources compared to traditional approaches; however, the carbon intensity of electrical energy and hydrogen production are keys to the overall environmental benefit.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2024

Residential Integrated Heat Pump to Meet All the Home Comfort Needs

This paper will introduce development and field trial of a residential air-source integrated heat pump for cold climates. The heat pump is multi-functional to meet all the home comfort demands, including space cooling, space heating, domestic water heating. The integrated heat pump is an ideal solution to decarbonize northern homes via providing efficient space heating and water heating to replace natural gas. It uses a three-stage compressor and a single set of heat exchangers and valves to deliver all the functions, and thus achieve cost reduction. We developed an innovative system configuration and related controls to solve typical charge unbalance, accelerate charge migration and smoothen mode transition in integrated heat pumps. Laboratory investigations were conducted for individual modes and verified the control functions. Laboratory tests demonstrated that the unit delivered outstanding performance. It achieved 17.0 SEER (seasonal cooling energy efficiency rating) and 11.0 HSPF (heating seasonal performance factor). In the most efficient mode (combined space cooling and water heating mode), the unit reached a total energy efficiency > 30.0 EER and required only 25 minutes to heat a 50-gallon tank of water. One heat pump prototype is going through a field trial since April, 2023 in Syracuse, New York. The one-year field test results are summarized.

Shen, Bo↗
DOE OSTI2021

Negligible spin–charge conversion in Bi films and Bi/Ag(Cu) bilayers

Spin pumping experiments using ferromagnetic metals have reported highly efficient spin–charge conversion in Bi and at the Bi/Ag interface, possibly due to the inverse Rashba–Edelstein effect. However, longitudinal spin Seebeck effect experiments using the yttrium iron garnet ferrimagnetic insulator in Bi films and Bi/Ag bilayers do not show evidence of appreciable spin-to-charge conversion except the large Nernst signal inherent to Bi. These contrasting conclusions highlight the differences between magnetic metals and magnetic insulators as spin current injectors. Only the detected voltages that adhere to the inverse spin Hall effect of j C = (2e/h)θ SH j S x σ are due to spin currents.

36 MATERIALS SCIENCE↗
NASA NTRS1987

High energy efficient solid state laser sources

Investigations continue of diode-laser-pumped solid-state laser oscillators and nonlinear processes using them as sources. Diode laser array pumped Nd:YAG and Nd:glass lasers have been demonstrated. Theoretical studies of non-planar oscillators have been advanced, producing new designs which should be more resistant to feedback and offer better frequency stability. A monolithic, singly resonant Optical Parametric Oscillator in MgO:LiNbO3 has been operated.

Byer, Robert L.↗
NASA NTRS1994

A review of vibration problems in power station boiler feed pumps

Boiler feed pump reliability and availability is recognized as important to the overall efficiency of power generation. Vibration monitoring is often used as a part of planned maintenance. This paper reviews a number of different types of boiler feed pump vibration problems describing some methods of solution in the process. It is hoped that this review may assist both designers and users faced with similar problems.

France, David↗