Report of Investigations--KGS


Fossil fuel power plants in Kentucky have some of the highest emissions of greenhouse gasses in the United States. One potential strategy for mitigating greenhouse gasses from electric power generation is the co-installation of Compressed Air Energy Storage (CAES) and a renewable source such as photovoltaic solar electricity generation (PV solar generation). CAES with complementary co-installed PV solar generation enhances stand-alone PV solar generation because CAES power is available at night.

CAES, however, requires both a site where large volumes of compressed air can be stored in the subsurface, and a heat source to prepare the stored air prior to entering the electricity-generating turbines. Co-installed PV solar electricity can provide the required thermal energy, but compressed air storage can be problematic. The two existing CAES plants, in Germany and Alabama, store compressed air in subsurface solution-mined salt caverns, however the thick salt deposits necessary to develop a compressed air storage cavern are not a part of Kentucky’s geology. Six compressed air storage models were reviewed as part of this project: acid solution-mined caverns, abandoned limestone mines, advanced energy storage in mined air storage chambers, depleted gas fields aquifer storage; and cased wellbore energy storage. Each of these models has the potential for application in Kentucky.

Two issues need to be addressed in applying CAES and its variations in Kentucky: ownership of the subsurface pore space where compressed air would be stored in depleted geologic reservoirs and aquifers, and social equity of the CAES electric power generation process. Pore space ownership is addressed under both state and federal law, generally from the standpoint of natural gas storage in depleted gas fields. These storage reservoirs would require an Environmental Protection Agency (EPA) injection permit. CAES models that do not impact porosity or groundwater may require other state and federal operational permits. Because CAES is both site-flexible and easily scalable, it provides a starting point for the conversation surrounding energy equity in the U.S. CAES with co-installed PV solar electricity generation provides a path to equitable power generation for all Americans.

Publication Date




Report Number


Digital Object Identifier (DOI)


This project demonstrates the options for developing green energy storage, zero CO2 emissions, by co-installing PV solar power generation and repurposing abandoned limestone mines, reentering abandoned oil and gas fields, and redeveloping reclaimed mined-out coal lands for energy storage.

Core permeability data was acquired by student research assistant Kyle Skeese at the KGS Earth Analysis Research Library. Kyle was last working at the Kansas Department of Health and Environment, Topeka, Kansas.

Funding Information

This research was funded by a 2020 seed grant from the Energy Research Prioritization Partnership at the University of Kentucky. We appreciate their support of this study.

Included in

Geology Commons