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At least 1,189 records · Page 66

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DOE OSTI2023

Cost and Performance Analysis for Five Existing Geothermal Heat Pump-Based District Energy Systems in the United States

District energy systems supplied by geothermal heat pumps (GHPs) have been deployed across the United States for both heating and cooling end uses. To better understand their performance and potential, the geothermal research team at the National Renewable Energy Laboratory analyzed cost and performance of five existing GHP-based district energy systems in the United States. The five systems selected are Ball State University in Indiana, Colorado Mesa University in Colorado, Miami University in Ohio, West Union in Iowa, and Whisper Valley in Texas. The necessary information, including district size, operation period, GHP performance, and costs, was collected through literature review and interviews. The survey results indicated the five systems studied consist of geothermal borehole field(s) and ground loop(s) connected to central loop. While the GHPs were in central plants at Ball State University and Miami University, the central loops at Colorado Mesa University, West Wood, and Whisper Valley were connected through service lines to individual heat pumps in each building. Our analysis indicates the systems have been operating reliably and cost-effectively and contributed to a reduction in carbon emissions.

15 GEOTHERMAL ENERGY↗

DOE OSTI2026

Ductless Heat Pump Program

The Verde Ductless Heat Pump (DHP) Program expanded access to high-efficiency electric heating and cooling technologies for households in priority communities within the Portland Metro area. Funded by the U.S. Department of Energy’s Building Technologies Office (DE-EE0010132), the program combined residential ductless heat pump deployment with community-based outreach, participant support, contractor partnerships, and system development to improve program delivery.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2022

Impact of Quaternary-Pumped Storage Hydropower on Frequency Response of U.S. Western Interconnection with High Renewable Penetrations: Preprint

As renewable penetration increases in the United States, maintaining stability and reliability of low-inertia power grid by providing sufficient frequency control capability becomes a challenge. Advanced pumped storage hydro technologies (APSH) will be expected to play an important role for future grid as not only an energy supplier, but also as an ancillary services provider. This paper studies the impact of using quaternary pumped storage hydropower (Q-PSH), as one of the newly proposed APSH technology, to provide primary frequency response. To quantify the impact of Q-PSH on frequency response of the U.S. Western Interconnection, a user-defined dynamic model of Q-PSH is developed on the GE Positive Sequence Load Flow (PSLF) platform and is implemented in a set of detailed U.S. Western Electricity Coordination Council (WECC) planning cases in which renewable penetration levels are 20%, 40%, 60% and 80%. Simulation results show that Q-PSH can help improve frequency nadir and settling frequency comparing to the conventional PSH.

frequency response↗

DOE OSTI2018

Uncertainty Quantification and Global Sensitivity Analysis of Subsurface Flow Parameters to Gravimetric Variations During Pumping Tests in Unconfined Aquifers

We study the contribution of typically uncertain subsurface flow parameters to gravity changes that can be recorded during pumping tests in unconfined aquifers. We do so in the framework of a Global Sensitivity Analysis and quantify the effects of uncertainty of such parameters on the first four statistical moments of the probability distribution of gravimetric variations induced by the operation of the well. System parameters are grouped into two main categories, respectively, governing groundwater flow in the unsaturated and saturated portions of the domain. We ground our work on the three-dimensional analytical model proposed by Mishra and Neuman (2011), which fully takes into account the richness of the physical process taking place across the unsaturated and saturated zones and storage effects in a finite radius pumping well. The relative influence of model parameter uncertainties on drawdown, moisture content, and gravity changes are quantified through (a) the Sobol' indices, derived from a classical decomposition of variance and (b) recently developed indices quantifying the relative contribution of each uncertain model parameter to the (ensemble) mean, skewness, and kurtosis of the model output. Our results document (i) the importance of the effects of the parameters governing the unsaturated flow dynamics on the mean and variance of local drawdown and gravity changes; (ii) the marked sensitivity (as expressed in terms of the statistical moments analyzed) of gravity changes to the employed water retention curve model parameter, specific yield, and storage, and (iii) the influential role of hydraulic conductivity of the unsaturated and saturated zones to the skewness and kurtosis of gravimetric variation distributions. The observed temporal dynamics of the strength of the relative contribution of system parameters to gravimetric variations suggest that gravity data have a clear potential to provide useful information for estimating the key hydraulic parameters of the system.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2018

Generation and Nonlinear Self-Addition of Laser Frequencies Upon High-Energy Diode Pumping of Er:BaY{sub 2}F{sub 8} Crystals

Special features of laser line generation upon high-energy diode pumping of Er:BaY{sub 2}F{sub 8} crystals are investigated. The UV and visible laser lines are effectively formed via nonlinear self-addition of frequencies of induced Er{sup 3+} lines at 541 and 553 nm with the corresponding frequencies of IR Er{sup 3+} lines upon pumping of the Er:BaY{sub 2}F{sub 8} crystals with a diode laser beam having a wavelength of 457 nm.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2022

Pumped Thermal Energy Storage With Liquid Storage

Pumped Thermal Energy Storage (PTES) uses electricity to power a heat pump; transferring heat from a cold space to a hot space forms a hot and a cold thermal reservoir, thereby storing energy. To discharge, the temperature difference between the two stores is used to drive a heat engine which generates electricity. In this chapter, PTES systems which store energy in liquids will be described. The chapter will concentrate on Joule-Brayton power cycles with molten salt storage. Part-load operation of Joule-Brayton PTES with liquid storage can be managed with "inventory control," and it is demonstrated that this control method leads to relatively good performance over a range of operating points.

Carnot batteries↗

DOE OSTI2018

Experimental evaluation and thermodynamic system modeling of thermoelectric heat pump clothes dryer

Electric clothes dryers consume about 6% of US residential electricity consumption. Using a solid-state technology without refrigerant, thermoelectric (TE) heat pump dryers have the potential to be more efficient than units based on electric resistance and less expensive than units based on vapor compression. This study presents a steady state TE dryer model, and validates the model against results from an experimental prototype. The system model is composed of a TE heat pump element model coupled with a psychrometric dryer sub-model. Experimental results had energy factors (EFs) of up to 2.95 kg of dry cloth per kWh (6.51 lb c /kWh), with a dry time of 159 min. A faster dry time of 96 min was also achieved at an EF of 2.54 kg c /kWh (5.60 lb c /kWh). The model was able to replicate the experimental results within 5% of EF and 5% of dry time values. Finally, the results are used to identify important parameters that affect dryer performance, such as relative humidity of air leaving the drum.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2024

Dual-module humidity pump for efficient air dehumidification: Demonstration and performance limitations

Condensation dehumidification in conventional air conditioning technologies is energy-intensive, accounting for up to 50% of building cooling energy used in some climates. Selective vacuum membrane dehumidification (VMD) is one of the leading alternative dehumidification technologies due to its potential for significant energy savings, and the “dual-module humidity pump” is one of the most promising VMD concepts. Here, this work is the first to provide experimental proof-of-concept for the dual-module humidity pump system and provides the first thermodynamic modeling framework that accounts for realistic steady-state operating limitations, both of which are lacking in the current literature. Additionally, this work is the first to provide a system design solution that overcomes practical challenges associated with air accumulation in the vacuum channels. The experimental results in this work show that the current prototype can remove up to 45% of the water vapor in the air stream, and the vapor pressure difference in the vapor rejection module needs to be approximately 2–4 times greater than that of the dehumidification module in order to maintain balanced mass transfer. The thermodynamic model applied to typical air conditioning conditions shows that the ideal dehumidification (latent) COPs can reach up to 40, but practical COPs are limited to approximately 10. Furthermore, the model shows that the overall energy efficiency increases as the membrane air selectivity increases, though this improvement gradually starts to diminish when the membrane selectivity is increased above 10,000.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2015

Data, exergy, and energy analysis of a vertical-bore, ground-source heat pump to for domestic water heating under simulated occupancy conditions

Evidence is provided to support the view that greater than two-thirds of energy required to produce domestic hot water may be extracted from the ground which serves as renewable energy resource. The case refers to a 345 m2 research house located in Oak Ridge, Tennessee, 36.01 N 84.26 W in a mixed-humid climate with HDD of 2218 C-days (3993 F-days) and CDD of 723 C-days (1301 F-days). The house is operated under simulated occupancy conditions in which the hot water use protocol is based on the Building America Research Benchmark Definition (Hendron 2008; Hendron and Engebrecht 2010) which captures the water consumption lifestyles of the average family in the United States. The 5.275 (1.5-ton) water-to-water ground source heat pump (WW-GSHP) shared the same vertical bore with a 7.56 KW water-to-air ground source heat pump for space conditioning the same house. Energy and exergy analysis of data collected continuously over a twelve month period provide performance metrics and sources of inherent systemic inefficiencies. Data and analyses are vital to better understand how WW-GSHPs may be further improved to enable the ground to be used as a renewable energy resource.

15 GEOTHERMAL ENERGY↗

DOE OSTI2025

Development and evaluation of a multi-functional heat pump with embedded thermal storage

We developed and tested a novel multi-functional packaged vertical heat pump designed for multi-family buildings, capable of providing space cooling, space heating, water heating, and energy storage integration. The system employs a 3-speed scroll compressor and supports energy-efficient cooling and heating across different ambient conditions, while utilizing both indoor and outdoor air sources for water heating. Key performance metrics include an integrated energy efficiency ratio of 18.0 for cooling, a heating seasonal performance factor of 10.0, and a coefficient of performance (COP) of 2.1 for heating in cold climates down to −15 ˚C. Additionally, the system delivers an annual water heating COP greater than 4.0, with outstanding performance in combined space cooling and water heating modes, achieving a total COP of 8.8 by recovering condenser waste heat. The heat pump also demonstrated thermal energy storage capabilities, integrating with phase change material systems to store heating and cooling energy. Furthermore, this versatile system offers a promising solution for improving energy efficiency and sustainability in multi-family buildings, providing high-performance heating, cooling, and water heating across a range of climates.

COP↗

DOE OSTI2019

Regression-based approach to modeling emerging HVAC technologies in EnergyPlus: A case study using a Vuilleumier-cycle heat pump

This paper presents a regression-based approach for modeling emerging heating, ventilation, and air-conditioning (HVAC) technologies using the user-defined coil object in the building simulation software EnergyPlus. The approach can use output from HVAC system models or experimental data to create regression-based performance curves, which are then used within the building simulation. The regression approach is an alternative to modeling new HVAC technologies directly in EnergyPlus or performing co-simulation with a system model in a separate program. The proposed approach connects component and system level designs, and their associated performance, with annual energy use and costs in a variety of climates. This study focused on a Vuilleumier-cycle heat pump for a commercial building. We describe (1) the design and modeling of this system, (2) methods for translating this performance into a simplified model in EnergyPlus, and (3) building energy simulation results in United States climate zones 4-6. The results predict that the Vuilleumier-cycle heat pump will use 34 to 44% less source heating energy than an 80% efficient gas furnace, and more source cooling energy than a SEER 13 air conditioner. Total energy costs are lower when electricity prices are high and natural gas prices are low.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2022

Bottom-up assessment of industrial heat pump applications in U.S. Food manufacturing

Decarbonization of the industrial process heat supply through electrification could contribute significantly to climate change mitigation efforts. In the U.S. industry, thermal processes accounted for more than two-thirds of the total final energy demand in 2021. Cross-cutting electrification technologies like industrial heat pumps are suitable for the process heat supply to several industrial unit operations in a sustainable way while also improving overall energy efficiency. This study employs a bottom-up approach to investigate the techno-enviro-economic potentials of deploying high-temperature and steam-generating heat pumps in the major U.S. food manufacturing sectors in different timeframes. The results show that the annual technical potential energy and CO 2 savings by electrifying process heat supply are 325 PJ (or approximately 20% of the total final energy demand in U.S. food manufacturing) and 31 MtCO 2 (equivalent to the annual CO 2 emissions from over 6 million cars in the U.S.) in 2050, respectively; however, these incur additional costs in each sector. Although there may be individual cost-effective opportunities for electrifying heat supply in specific industrial sites, the overall costs are estimated to be high in the food sectors due to the large disparity between electricity and natural gas prices and low heat source temperatures. To overcome the identified techno-economic barriers, comprehensive action plans for different stakeholders are needed. In conclusion, this study provides novel insights that should inform policymakers’ and executives’ decisions about the electrification of the current and future U.S. industrial heat supply in relevant industrial sectors.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

DOE OSTI2026

Investigation of a thermocapacitive cycle by aqueous supercapacitors for multifunctional heat pump and energy storage

Thermocapacitive cycles are promising thermal and energy storage cycles using supercapacitors, which can achieve thermal efficiencies over 50% of the Carnot limit. There is a lack of work investigating the use of thermocapacitive effects in practical heat pumps. Here, this paper explores the design of thermocapacitive cells with higher temperature changes to be better suited for heat pumping applications. To evaluate the cell designs on temperature changes, pouch type cells are prototyped and modeled, and tested using a micro-calorimeter. A peak adiabatic temperature span of a LiCl aqueous cell is 2.7 °C. By arranging the cells in a cascade manner, the projected adiabatic temperature span can reach up to 12 °C with a heating density of 15 kW m −3 and an energy storage density of 0.83 kWh m −3 . Models predict that this could be increased to 30 °C and 1.65 kWh m −3 through improvements to cell capacitance and thermopower. Incorporating the energy storage capabilities into heating and cooling devices can be beneficial to building thermal management as energy storage becomes increasingly important for energy system integration.

25 ENERGY STORAGE↗

DOE OSTI2016

A novel method to determine air leakage in heat pump clothes dryers

A heat pump clothes dryer offers the potential to save a significant amount of energy as compared with conventional vented electric dryers. Although heat pump clothes dryers (HPCD) offer higher energy efficiency; it has been observed that they are prone to air leakages, which inhibits the HPCD's gain in efficiency. This study serves to develop a novel method of quantifying leakage, and to determine specific leakage locations in the dryer drum and air circulation system. The basis of this method is the American Society of Testing and Materials (ASTM) standard E779 10, which is used to determine air leakage area in a household ventilation system through fan pressurization. This ASTM method is adapted to the dryer system, and the leakage area is determined by an analysis of the leakage volumetric flow - pressure relationship. Easily accessible leakage points were quantified: the front and back crease (in the dryer drum), the leakage in the dryer duct, the air filter, and the remaining leakage in the drum. The procedure allows investigators to determine major components contributing to leakage in HPCDs, thus improving component design features that result in more efficient HPCD systems.

42 ENGINEERING↗

DOE OSTI2020

Design screening and analysis of gas-fired ammonia-based chemisorption heat pumps for space heating in cold climate

Thermally-driven ammonia-based chemisorption heat pumps (CSHP) have the potential to provide high-efficiency space heating in cold climates. Using the reversible chemical bond between sorbent salt and ammonia, CSHP thermochemically pumps heat from the cold ambient to the end-uses of space heating at 50 °C. The heating coefficient of performance (COP) of a CSHP largely depends on the selection of the sorbent salts, cycle configuration, and the system operation. This study uses a thermodynamic model to investigate the performance of six CSHP system configurations, including four single-effect and two double-effect cycles. The feasibility and performance of 121 available NH 3 /salt reactions are studied for each configuration. The thermal COP of the cycles and the primary energy COP of the gas-fired CSHP systems are evaluated assuming 50 °C supply temperature for building space heating and the optimal system designs are identified. The highest thermal COP for single-effect and double-effect cycles under -25 °C ambient temperatures are predicted to be 1.22 and 1.57, respectively. The corresponding primary energy COPs are above 1.0 and 1.15, which are 30% higher than condensing furnaces and is sustained into the same cold temperatures.

42 ENGINEERING↗

DOE OSTI2021

High-temperature Pumping of Silicon for Thermal Energy Grid Storage

As the cost of renewable energy falls below fossil fuels, the key barrier to widespread sustainable electricity has become availability on demand. Energy storage can enable dispatchable renewables, but only with drastic cost reductions compared to current batteries. One electricity storage concept that could enable these cost reductions stores electricity as sensible heat in an extremely hot liquid (>2000 °C) and uses multi-junction photovoltaics (MPV) as a heat engine to convert it back to electricity on demand, hours or days later. This paper follows previously reported technoeconomics and liquid containment, examining equipment that would be needed to exchange heat between resistive heaters, a molten silicon storage tank above 2000 °C, and a heat engine. Herein, we report on a pump that was designed and tested to circulate the liquid silicon between these three regions and the effect of spatial thermal cycling was simulated in models and experiments. While the pump successfully circulated silicon between 1800-2080 °C for ten hours, circulation with a temperature gradient caused it and other non-isothermal experiments to dissolve significantly due to the temperature dependent solubility of not only carbon, but also silicon carbide which otherwise protected the graphite infrastructure. Furthermore, methods to reduce dissolution and an alternative embodiment are presented.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2017

Methodology for energy strategy to prescreen the feasibility of Ground Source Heat Pump systems in residential and commercial buildings in the United States

Geothermal resources have potential to reduce dependence on fossil fuels. The viability of geothermal heat pumps or ground source heat pumps (GSHPs) is significant as a potential alternative energy source with substantial savings potential. While the prospect of these systems is promising for energy efficiency, careful feasibility analysis is required before implementation. Here, this paper presents the results of evaluation of the application feasibility for GSHPs in buildings across seven climate zones in three United States regions. A comprehensive methodology is developed to measure the integrated feasibility of GSHPs using compiled data for energy use intensity, energy cost and design parameters. Four different feasibility metrics are utilized: ground temperature, outdoor weather condition, energy savings potential, and cost benefits. For each metric, a corresponding feasibility score system is developed. The defined integrated feasibility score classifies the locations into five different feasibility levels ranging from Fair (0–20), Moderate (21–40), Good (41–60), High (61–80), and Very High (81–100). Conclusions show the GSHP feasibility level is High for 3 sites, Good for 8 sites and Moderate for 4 sites. Through the methodology, it is possible to develop a practical energy strategy for more economic and sustainable GSHP systems at an early design stage in the various viewpoints of geometries, climate conditions, operational factors, and energy costs.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2019

Demonstration of femtosecond broadband X-rays from laser wakefield acceleration as a source for pump-probe X-ray absorption studies

Here, we present X-ray absorption measurements near the K-edge of laser heated aluminum in a pump-probe configuration using X-rays generated in a laser wakefield accelerator. A 30 fs duration laser pulse from the Hercules laser system was split into two beamlines, with one used to heat a 4 $μ$m thickness Al foil and the second to drive a laser wakefield accelerator. The laser-heated plasma was probed at various pump- probe delays using the femtosecond duration X-rays generated by betatron oscillations of the electrons in the wakefield. We observe an apparent blue-shift of the K-edge occurring on a sub-picosecond timescale in the transmission spectra.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗