Thermal storage system with coupled tanks

Liu, Xiaobing; Qu, Ming; Warner, Joseph K.; Shi, Liang

Home/Archive/DOE OSTI

DOE OSTI · 1925018

Thermal storage system with coupled tanks

Liu, Xiaobing·Qu, Ming·Warner, Joseph K.·Shi, Liang

View original source ↗Read source document ↗Export metadata ↓

Abstract

Methods and apparatus are disclosed for high-efficiency thermal storage with a fluid-filled “battery” tank positioned within a fluid-filled “reservoir” tank. Fluid loops couple the tanks to a heat pump and a building. The heat pump can charge the battery tank or deliver thermal energy (cold or heat) to a building, using the reservoir tank or ambient air as a thermal energy source. The battery tank can discharge energy to the building jointly with the heat pump or, at periods of peak electricity usage, with the heat pump switched off. Operating modes allow significant savings in electricity usage and mitigate the “duck curve.” Low duty cycle usage of the reservoir enables efficient underground thermal storage with less digging than conventional geothermal technologies. Additional efficiency is achieved with phase change materials installed inside a tank or in a tank wall, providing temperature regulation. Control methods are disclosed.

Explore related subjects

15 GEOTHERMAL ENERGY 29 ENERGY PLANNING, POLICY, AND ECONOMY

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Liu, Xiaobing, Qu, Ming, Warner, Joseph K., Shi, Liang. 2022-08-23. Thermal storage system with coupled tanks. https://www.osti.gov/biblio/1925018

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related reports

DOE OSTI2026

Technical, economic, and load-following capabilities assessment of grid-connected geothermal and geothermal-solar hybrid systems

The technical and economic performance as well as the load-following capabilities of grid-connected geothermal hybrid systems were assessed in this work. The analyzed geothermal hybrid configuration is composed of a binary geothermal plant integrated with a concentrating solar-thermal system and underground thermal energy storage (UTES) through a primary heat exchanger. Physics-based models for the hybrid system for plant generation capacities of 1, 25, and 50 MW were developed from validated models for each subsystem. Also, an economic model was developed that accounts for different hybrid system capabilities, solar field sizes, and thermal storage duration. The advantage of the geothermal hybrid system was assessed by comparing the performance with the baseline benchmark geothermal plant with a similar configuration and generation capacity. It was found that hybridizing geothermal plants with concentrating solar and thermal energy storage not only improves the thermal efficiency by up to 8 percentage points when additional heat from the solar-UTES loop rises the evaporator temperatures from 70 to 125 °C, but also enhances the load-following capability for the geothermal plant, which can meet a typical residential load profile with a power rate of change 0.25 kW/s with an absolute error under 13 kW for a 1 MW plant. Other benefits of hybridization include resource preservation and a potential LCOE reduction of up to 56% for a 50 MW geothermal hybrid plant having a 50% solar share, a 1.4 solar multiple, and 24-h storage capacity. The results presented in this work demonstrate that hybridizing geothermal systems transforms them into a flexible and cost-effective solution for addressing the dynamic requirements of modern electric grids.

15 GEOTHERMAL ENERGY↗

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

Impact of Space Heating Options on Electricity Rates and Affordability

Electricity prices have increased in many regions of the U.S., with a national average of 18 cents/kWh projected for 2026, up from 16 cents/kWh in 2020. While the increases can be attributed to a number of factors, increasing electricity use in an efficient and strategic manner - with energy efficient building envelope upgrades and high performance HVAC systems - has the potential to increase revenue for utilities without significantly increasing electricity demand, and therefore could help moderate rate increases. This effect has been studied for electric vehicle charging[1] and dual-fuel heat pumps in Minnesota[2]. Leveraging a recently developed system cost methodology and FERC data on utility revenue, spending, and profits, this poster will present the direction and relative magnitude of rate impacts for efficient space heating upgrades in utility balancing areas across the contiguous U.S., using current prices and showing how the rate impacts would evolve under future grid scenarios.

15 GEOTHERMAL ENERGY↗