Sub-surface Energy and Storage
“Subsurface energy and storage” refers to the practice of storing energy within underground geological formations, like depleted oil and gas reservoirs, aquifers, or deep saline formations, utilizing the Earth’s subsurface as a storage medium for various forms of energy, including heat (geothermal), compressed air, hydrogen, or carbon dioxide, allowing for energy to be captured and accessed when needed.
Key aspects of subsurface energy storage:
Applications
- Geothermal energy: Storing heat extracted from the Earth’s subsurface for later use.
- Carbon capture and storage (CCS): Injecting captured carbon dioxide underground to prevent its release into the atmosphere.
- Compressed air energy storage (CAES): Storing compressed air in underground caverns to generate electricity when needed.
- Hydrogen storage: Storing hydrogen underground for future use in fuel cells.
Benefits
- Large storage capacity: The Earth’s subsurface offers vast storage potential compared to surface-based options.
- Long-duration storage: Energy can be stored underground for extended periods, enabling seasonal energy management.
- Potential for renewable energy integration: Can help balance fluctuations in renewable energy sources like solar and wind.
Challenges
- Geological characterization: Understanding the subsurface geology to identify suitable storage sites.
- Injection and extraction technologies: Developing efficient methods to inject and retrieve stored energy.
- Environmental considerations: Ensuring the safety and long-term integrity of storage sites, including potential impacts on groundwater.
Geothermal Energy Data and Potential
As a contributing partner of a national coalition, the Michigan Geological Repository for Research and Education at Western Michigan University has been collecting data from across the state that will aid industry in the identification and development of geothermal energy, and it has integrated that data into the National Geothermal Data System. These data are available to all those interested in developing geothermal energy resources.
The National Geothermal Data System is a distributed data system providing access to information resources related to geothermal energy from a network of data providers. Data are contributed by academic researchers, private industry and state and federal agencies. Funded by the Department of Energy’s Geothermal Technology Office, the NGDS provides information to help accelerate the development of United States geothermal resources and can be used to:
- Assess geothermal potential.
- Help potential investors evaluate potential income, expenses and long-term cash flow.
- Reduce risks in exploration and development of this energy source.
- Guide land-use planners and governmental agencies in making decisions about community development.
Geothermal Energy Potential for Michigan
Dr. William B. Harrison, III, research director, had led efforts to assess Michigan’s geothermal energy potential. Unlike western states with easily accessible geothermal resources like geysers, Michigan’s geothermal energy comes from hot brines in deep rock formations. Harrison gathered data from deep wells drilled by oil and gas companies, focusing on temperature and pressure records, as well as water chemistry and lithology information.
Research focused on shallow formations to evaluate heat flow for geothermal heat exchange systems, which are already widely used in Michigan for heating and cooling. Michigan’s low geothermal gradient means high-temperature geothermal power generation is challenging, requiring depths over 10,000 feet. However, shallow geothermal systems can still offer economic benefits.
Other states are exploring the use of existing deep wells for geothermal energy, and Harrison suggests that Michigan might have similar potential, but more data is needed to identify the locations of hot brine fluids. Compiling geothermal data from across the U.S. is crucial for developing this renewable energy resource.
