GSHPs would relieve stress on US electricity grid

USA: The widespread deployment of ground-source heat pumps in the USA would relieve the stress on the grid, lower energy costs and substantially reduce CO2 emissions, a new study claims.

A modelling analysis led by the US Department of Energy’s Oak Ridge National Laboratory (ORNL) takes a detailed look at how geothermal energy, along with building envelope improvements in single-family homes, could relieve the electric power system and reduce carbon emissions within the next few decades. 

The results were obtained from a simulation model of the mass deployment of geothermal heat pumps (GHPs) in commercial and residential buildings from 2022 through 2050.

ORNL’s Xiaobing Liu, who served as the primary researcher on the study, said that mass GHP deployment in both commercial and residential buildings, coupled with building envelope improvements in single-family homes, can reduce more than 7,000 million tonnes of carbon emissions through 2050, with more than 3,000 million tonnes of reduction coming from the electric sector and the remaining coming from the replacement of natural gas for heating in the building sector. 

Simulations

ORNL buildings and electrification researchers worked with the National Renewable Energy Laboratory (NREL) to build co-simulations of the US building stock and the electric power systems using ORNL’s GHP system simulation tool and building data available in NREL’s energy use load profiles. 

This first-of-its-kind study simulates the energy use impacts if GHPs were deployed into 68% of existing and new building floor space across the contiguous United States. Researchers studied three scenarios: continuing to operate the grid as it is today; reaching 95% grid emissions reductions by 2035 and 100% clean electricity by 2050; and expanding grid decarbonisation to include the electrification of wide portions of the economy, including building heating. The analysis team modelled each of these three scenarios with and without mass GHP deployment coupled with building envelope improvements in single-family homes.

“The results were developed using the current capability of existing tools and data,” said Xiaobing Liu. “We combined NREL’s Regional Energy Deployment System model and PLEXOS, a commercial software for more detailed simulation of electric power systems, to perform multiyear simulations of US electric power systems in different scenarios in contrasting regions, in different seasons and during times of peak and low energy demand.”

Regional variations

Although savings in electricity demand and reduction in carbon emissions were realised in almost all regions of the country, the simulations indicated that in cold climates, GHPs are more effective at reducing carbon emissions and energy consumption compared with conventional HVAC systems as the result of displacing natural gas furnaces and reducing the use of electric heaters. In warmer climates, such as in the south and other milder climate zones, GHPs generate higher electricity savings. Peak electric demand reduction is also highest in densely populated areas of the south. 

“We showed that a mass deployment of GHPs coupled with building envelope improvements can reduce the generation and capacity needs of the US electric power system by up to 11% and 13%, respectively, in 2050,” Liu said. “The peak electric demand in some hot climate zones can also be reduced up to 28%, which will ease grid operations.”

These percentages translate into saving approximately 600TWh of electricity in 2050 while eliminating more than 5,000 billion Mj of fossil fuels, which is equivalent to 5% of the primary energy consumed in the United States in 2022, including natural gas, heating oil and propane. 

Liu maintains that if GHP deployment were to increase steadily from 2022 through 2050, more than $300bn cumulative electricity payments would be saved, too. This would require the deployment of approximately five million GHPs per year.

Decreasing outages

GHPs could be a solution to improving grid stability. To prove the capability, the study analysed the impact of mass GHP deployment on the Texas electrical grid, which experienced significant power loss with winter storms in 2021. 

“During these intense weather events, mass deployment of GHPs could have improved the operation of the grid by reducing total electricity demand,” Liu said. “This preliminary analysis can provide insightful information to Texas and other regions that have experienced higher demand for electricity than the power plants can provide during periods of prolonged severe weather.”

Liu said that although the initial evaluation indicates that mass deployment of GHPs can improve grid reliability in Texas, a more detailed analysis is needed to get a precise picture of how they would perform in different regions.

Jamie Lian, who served as a co-investigator of the study, added that if GHPs were to be deployed across the United States, many installations would be done by utilities in district-scale systems so that ground drilling can be leveraged across numerous buildings. The study provides a basis for utilities to evaluate the investment of GHP deployment.

“A lasting benefit of this study is that we’ve developed a nationwide analysis that scales up from the building analysis to the regional impact and to the entire grid,” Lian said. 

Online tools

To better understand the cost and benefits of GHP applications, the ORNL research team has developed a consumer-friendly, web-based tool for estimating the cost and benefits of applying GHPs in residential and commercial buildings.

The free tool is openly accessible to homeowners, builders, installers, and manufacturers. It allows users to calculate the energy savings that can be achieved by GHPs when installed in any type of residential or commercial building in any US climate zone. 

The tool leveraged ORNL’s AutoBEM software, which can automatically create a building energy simulation model for almost any existing building in the nation based on minimal information, including the building footprint, vintage, principal function and other information from DOE’s prototype building models.

“When there is a massive deployment of GHP systems, we now have a starting point for what it would look like in terms of capacity, generation, emissions, cost and resilience for the electric power systems,” Liu said. “That picture looks very promising.”