Modeling the Potential to Deploy Offshore Compressed Air Energy Storage in the Eastern United States

Abstract:

Wind and solar power generation potential is growing rapidly in many regions of the United States and the World but its temporally and seasonally intermittent nature is creating a demand for low-cost, long-duration energy storage. In this talk, we explore the potential for deploying a novel energy storage technology called Offshore Compressed Air Energy Storage (OCAES) in which compressed air is stored in subsurface saline aquifers when excess power is available and later extracted and used to drive a turbine when power is needed. Wind farms planned off the Eastern United States coast overlap a saline aquifer called the Baltimore Canyon Trough, so we consider the possibility of co-locating OCAES with a wind farm to reduce system costs. Water injection is used during compression and expansion to achieve near-isothermal processes resulting in higher round trip efficiencies, without the use of fossil fuels. A technoeconomic assessment of OCAES is carried out using a process model to assess the round trip efficiency and storage potential by simulating the fundamental physics relationships. Round trip efficiencies up to 80% are estimated but results are sensitive to geophysical parameters, particularly formation depth and permeability. Capital costs for OCAES are projected to be lower than current estimates for lithium ion batteries. The value of OCAES to the electric grid was evaluated by optimizing its operation over a year of wind generation and spot market price data in the Mid-Atlantic. It was found that OCAES increases the revenue of the wind farm by shifting when wind energy is sold to the electric grid. The process and optimization models we developed are open-source in Python and available for download. A number of CAES projects have failed over the past two decades because of some combination of engineering, geology, and management challenges and our modeling work will explore the sensitivity of this system to these factors in the current energy landscape and explore its potential for OCAES in the near-term.