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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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Geothermal heat pumps can be great alternatives to air conditioners and furnaces, and require less electricity to run. This case study focuses on Louisville Muhammad Ali International Airport and is part of a series: https://www.energy.gov/eere/geothermal/geothermal-heat-pump-case-studies.
Geothermal heat pumps can be great alternatives to air conditioners and furnaces, and require less electricity to run. This case study focuses on Central New Mexico Community College and is part of a series: https://www.energy.gov/eere/geothermal/geothermal-heat-pump-case-studies.
This project was part of an effort by ComEd's emerging technology program to evaluate the energy saving potential of new energy efficiency technologies. The focus of this technology assessment was to determine energy and peak demand savings potentials of a high efficiency variable speed, air-source, split system heat pump designed for cold climate applications. The results of this technology assessment will be used by CLEAResult to develop a new energy efficiency measure for Commonwealth Edison Company's incentive programs. The project utilized the National Renewable Energy Laboratory's (NREL) Thermal Test Facility to experimentally characterize cooling and heating performance of a high efficiency heat pump split system under varying outdoor climate conditions. The selected climate conditions represented summer and low temperature winter conditions in ComEd's service territory. The laboratory experimentation results were used to develop equipment performance curves required by EnergyPlus hourly simulation engine. Using typical meteorological year 3 weather data for the Chicago O'Hare airport, hourly building simulations (using the EnergyPlus engine) was utilized to estimate the annual energy savings of the high efficiency heat pump in comparison to a standard efficiency unit in the following U.S. Department of Energy (DOE) building codes program energy prototypes: Single-family residence; Strip mall; and Low-rise office.
Pumped Thermal Energy Storage (PTES) is a promising technology for electricity storage applications. Grid electricity drives a heat pump which moves energy from a cold space to a hot space, thereby creating hot and cold thermal storage. The temperature difference between the storage is later used to drive a heat engine and return electricity to the grid. In this article, supercritical carbon dioxide (sCO2) is chosen as the working fluid for PTES, and results are compared to ‘conventional’ systems that use an ideal gas. Molten salts are used for the hot storage which means that a CSP plant with thermal storage and an sCO2 power cycle could potentially be hybridized with PTES by the addition of a heat pump. This article describes some of the benefits of this combined system which can provide renewable power generation and energy management services. Two methods by which an sCO2 heat pump can be combined with an sCO2 power cycle for CSP are described and techno-economic results are presented. Results indicate that these systems can achieve reasonable technical performance, but that costs are currently high.
This report describes the implementation and impacts of a geothermal heat pump, envelope, and lighting upgrade package. This measure scenario involves replacing existing HVAC systems with geothermal heat pumps, upgrading wall insulation, roof insulation, and windows, and replacing lighting with LEDs.
High-performance HVAC solutions are central to residential energy management. A substantial share of these are electric, reversible-cycle systems, with heat pumps representing the largest portion of current and near-term adoption. This review synthesizes peer-reviewed and grey literature on residential space heating and cooling heat pumps. The academic literature is dominated by modeling (73.8%), with limited field measurement (13.1%). Grey literature from United States serve as a supplemental resource providing measured savings. Conversions from electric-resistance heating consistently show the largest site energy reductions, while oil/propane baselines yield moderate savings, and gas baseline scenario often deliver small and region-dependent savings. This study cross-checks the grey literature measured data with simulation data filtered from the ResStock dataset. The comparison indicates a discrepancy between simulations and measured data: simulated site EUIs are typically lower than measured EUIs, but percentage energy savings fall in similar ranges, implying simulations capture directional effects while underestimating energy use. Factors associated with variability and model–measurement differences include system characterization and control representation (e.g., backup heat engagement, thermostat/setpoint strategies, commissioning/installation quality), occupant behavior, weather normalization, metering scope, and envelope characterization. This paper also outlines the proposed methodology for comparing simulation and measured data for heat pumps. It emphasizes the metrics used for comparison and units harmonization, building characteristics matching, and compact metadata are needed for simulations to match measured data. The proposed methodology is expected to improve the credibility of simulated savings as measured evidence grows.
Propane is an environment-friendly refrigerant, having a 20-year GWP (global warming potential) of 0.072 and a 100-year GWP of 0.02, as compared to R-410A having a GWP > 2000. It has superior thermodynamic cycle performance and heat transfer characteristics. However, propane is classified as a A3 refrigerant, which is highly flammable, and not allowed to be used indoor if the system charge is higher than 150 grams. It is a challenge to use propane in residential applications requiring a rated capacity larger than 10 k Watts. A hydronic heat pump, i.e., containing propane in an outdoor unit and distributing the cooling and heating capacity through a hydronic coil to the indoor space addresses the flammability issue, while maintaining a high efficiency. We developed a hydronic heat pump with propane, it uses a two-stage compressor, a brazed plate indoor heat exchanger, and a microchannel outdoor heat exchanger. It achieves a rated cooling capacity larger than 10 k Watts, and a cooling SEER (cooling seasonal energy efficiency rating) > 16.0 (cooling seasonal COP > 4.7) and a heating HSPF (heating seasonal performance factor) > 9.5 (heating seasonal COP > 2.78), while requiring a system charge < 1200 grams. Additionally, the hydronic heat pump was evaluated in a laboratory water heating loop to heat a 50-gallon water tank in a full condensing mode. Experiments of heating the tank water from 58F(14.4°C) to 150F(65.6°C) were conducted under ambient temperatures from 17F(-8.3°C) to 75F(23.9°C), at the compressor high and low stages.
Heat pump water heaters (HPWHs) offer an efficient alternative to electric resistance water heaters, but they suffer from limited market penetration. This paper reviews the current state of HPWHs in the USA, focusing on technology developments and programs to increase adoption. What technological improvements are needed to make HPWHs a good fit in more homes? Additionally, what are the best ways of promoting HPWHs to consumers? Improved communication and controls will allow HPWHs to provide demand response and follow dynamic utility rates. To enable fuel-switching, HPWHs are being developed that only need a standard 120V outlet. Split HPWHs can alleviate the cooling and noise that limit the use of HPWHs in small homes, multifamily buildings, and cold climates. Additionally, new utility programs aim to train installers and provide incentives to distributors to increase the number of HPWHs installed. Some utilities offer novel incentive programs that have led to increased customer uptake. Those advances, coupled with improved controls for load shifting and new products such as split HPWHs and HPWHs that can run on 120V power, may finally move the market forward.
Supercritical water desalination (SCWD) is zero liquid discharge technology that can potentially control the solubility of different electrolytes. However, SCWD is an energy-intensive process and requires high-quality thermal heat (> 450 °C). This study proposes the integration of a high-temperature heat pump to reduce the SCWD energy requirement. The integrated system energy consumption improves by 36% for 3.5% feed concentration and 14% for 20% feed, and the distillate cost reduces by 15% and 10%. Another benefit of the proposed integration is the system can be operated using only electricity as a heat source, as is the case with commonly used high-recovery thermal desalination technology. The integrated SCWD-heat pump system shows superior performance compared to the commercially used brine concentrator and crystallizer system. It is approximately 20% more energy-efficient for 25% feed concentration and 8% cheaper. Hence, the integrated SCWD-heat pump has the potential to outperform the pre-existing high-recovery desalination technology.
An air-source integrated heat pump (ASIHP) is a multifunctional unit, capable of space cooling, space heating, and water heating. We developed a packaged cold climate ASIHP, using a multi-stage compressor, capable of working down to -25°C, and providing 100% rated capacity down to -15°C with a heating COP > 2.2. An innovative system configuration and related controls were developed to solve charge balance in the integrated heat pump, smooth charge migration, and mode transition among multiple working modes. Extensive laboratory investigations for individual modes were performed to verify the performance. Its integrated heating capability provides speedy water heating to meet domestic hot water use and store heating energy in a phase change material ceiling/panel. The heating energy storage can be used to shift the load when the electricity price is high. Based on the performance data and a calibrated model from the laboratory testing, we conducted building energy simulations driven by a model predictive control, using EnergyPlus in one U.S. cold climate zone to investigate the grid-responsive control strategy and estimate the utility cost reduction potential.
Geothermal heat pumps can be great alternatives to air conditioners and furnaces, and require less electricity to run. This case study focuses on The Inn on Boltwood and is part of a series: https://www.energy.gov/eere/geothermal/geothermal-heat-pump-case-studies.
Geothermal heat pumps can be great alternatives to air conditioners and furnaces, and require less electricity to run. This case study focuses on Westwood Hills Nature Center and is part of a series: https://www.energy.gov/eere/geothermal/geothermal-heat-pump-case-studies.
Geothermal heat pumps can be great alternatives to air conditioners and furnaces, and require less electricity to run. This case study focuses on Medford Site Veterans Home and is part of a series: https://www.energy.gov/eere/geothermal/geothermal-heat-pump-case-studies.
This package replaces existing gas and electric resistance rooftop units (RTUs) with standard efficiency heat pump RTUs and improves roof insulation. The purpose is to couple heat pumps retrofits with an improved envelope to investigate the combined effect.
Geothermal heat pumps can be great alternatives to air conditioners and furnaces, and require less electricity to run. This case study focuses on Dallas-Fort Worth U.S. 287 Bridge and is part of a series: https://www.energy.gov/eere/geothermal/geothermal-heat-pump-case-studies.
Ejector heat pump (EHP) is an efficient-energy technology with a promising potential to replace the vapor compression cycle in heating and cooling applications. It can be powered by low-grade waste heat and uses environmentally friendly working fluids. EHP has also become a viable solution in research seeking cooling applications. However, little attention has been paid to using EHP for heating purposes. In order to investigate this, a steam EHP for domestic water heating was designed and built. The coefficient of performance (COP) is evaluated at various operating and design conditions in sub-critical operational modes to achieve higher condensation temperatures. Two primary nozzles with a throat diameter of 1.5 mm and 2.0 mm were investigated. The primary nozzle is movable along the ejector’s axis, allowing investigation of its positional effects on the EHP’s COP. Further, experimental measurements revealed that using a smaller throat diameter results in a high COP and low back pressure. The EHP COP and back pressure increase when the LTE temperature increases. Using a throat diameter of 1.5 mm, the EHP COP increases as the nozzle exit position (NXP) becomes closer to the constant area section. A COP of 2.42 and a back pressure of 4.28 kPa are achieved at a high-temperature evaporator (HTE) temperature of 130 °C and a low-temperature evaporator (LTE) temperature of 30 °C using a primary nozzle with 1.5 mm.
Full decarbonization in buildings requires the replacement of combustion appliances with electric ones, and air source heat pumps (ASHP) are a candidate alternative. However, technical limitations, such as the efficiency decrease when operating in cold weather, limit their adoption in the global heating market. Among several options to improve ASHP efficiency operating in colder climates, thermal energy storage (TES) has been considered, as it may provide heating when it is cold and shift ASHP operation to times when the weather is warmer. It may also take advantage of time of use electricity rates and support defrosting when necessary. The evaluation of ASHP-TES systems, however, is still limited because traditional metrics do not capture their full economic and environmental benefits. In this work, a python framework is presented to model the ASHP with and without the presence of TES. Metrics are proposed to analyze the system performance in terms of costs, equivalent CO2 emission, and efficiency metrics to evaluate and compare alternative systems. Model validation against experimental data obtained for a commercial heat pump is provided, as well as an application example using Denver, Colorado, to highlight the model capabilities.
The intended purpose of this project was to bring alternative heat and ventilation options to rural communities off the road system in Northwestern Alaska. Most of the residents of these communities are reliant upon kerosene or other fossil fuels to provide heat to their homes. Our intention was to offer an alternative to using those sources by providing heat pumps to 45 homes in the communities of Elim and Koyuk. When projecting energy use for these units based on the fuel prices at the time, it was discovered that energy costs for heat pumps would equal or slightly exceed the costs of existing kerosene units. Secondly, as part of our E&l grant we installed 45 energy recovery ventilators (ERV’s) in those same homes. This was important given our experience over the years with moisture and comfort issues in most homes within this region. Exhaust-only systems are rarely used due to the high heating costs. Additionally, exhaust-only systems have a potential risk of back drafting due to tight building construction. Balanced systems like this eliminate that risk while improving indoor air quality. Another benefit to these types of systems is the fact that they help transfer heat from a single heat source equally throughout the building. Our overall goal was to offer new technology options to improve these structures and the families that reside in them where, given their location and extreme seasonal temperature swings, they have historically never been offered.