Compressed Gas Energy Storage Using Depleted Unconventional Shale and Tight Sandstone Gas Formations

Stage: Development

As renewable energy technologies proliferate, it is becoming increasingly necessary to store energy from these variable generation sources in an economical way. In 2018 alone, over 750 MWh of storage were deployed in the United States, with expected doubling in 2019, followed by a tripling in 2020. Although lithium ion batteries are typical in today’s storage projects, they are best suited for grid ancillary services and short-term energy storage. Compressed air energy storage (CAES) is a technology under investigation, because it can store energy for long durations and can be deployed in a wide range of locations. To reduce costs, CAES can be accomplished using depleted hydraulically-fractured unconventional shale and tight sandstone gas wells as a storage medium, but there are a number of problems with this approach. Oxygen in air can corrode well equipment and mix with hydrocarbons to create a potentially explosive mixture inside the well. 



Further innovation is required to make this technology safe and effective enough for widespread use.

Researchers at NREL have devised a method to store energy in depleted hydraulically-fractured shale gas wells that avoids these problems. By substituting natural gas for air energy storage, projects can avoid problems related to corrosion and safety. Unlike conventional CAES, this technique is suitable for a range of wells which can be found in a variety of geographies. The new technique proposes injecting compressed natural gas without post-cooling and expanding the gas without pre-heating. The elimination of this equipment decreases system complexity, thereby reducing cost. The storage of thermal energy with the gas increases round trip efficiency. The resulting technology is both safer and much more cost effective than traditional proposed CAES designs.

For more information, please contact Erin Beaumont at:

Erin.Beaumont@nrel.gov

ROI 18-05

Applications and Industries

  • Utility scale energy storage

Benefits

  • Safe, reliable long duration energy storage
  • Simplified design that can be implemented cheaply
  • Can be installed on wells in a variety of locations