Environmental impacts of balancing offshore wind power with compressed air energy storage (CAES)

• We model life cycle environmental impacts for compressed air energy storage.
• Both conventional (CAES) and adiabatic (ACAES) storage options are investigated.
• Addition of air storage to wind power generation increases impacts moderately.
• Main impact due to natural gas combustion (CAES) or thermal energy storage (ACAES).
• ACAES has potential for lower impact than CAES as no natural gas is combusted.

Using Life Cycle Assessment, we discuss the environmental impacts associated with a Compressed Air Energy Storage (CAES) system as a means of balancing the electricity output of an offshore wind farm with a capacity of 400 MW. We model both conventional CAES and adiabatic CAES (ACAES), with target for baseload production of respectively 200 MW and 150 MW. For the CAES system, wind power production and natural gas combustion are main contributors to the assessed life cycle environmental impacts. For the ACAES system, wind power production and thermal energy storage are significant contributors. Compared with the impacts of wind power alone, and for the modeled energy storage size and target output, we find that CAES increases acidification, particulate matter, photochemical oxidant formation, and climate impacts significantly, but decreases eutrophication, toxicity, and mineral resource depletion impacts. ACAES moderately increases environmental impacts across all assessed impact categories, and impacts are sensitive to the required capacity of the thermal energy storage. In comparison with impacts from the average European mix, both storage configurations in our base case have low impacts per kWh electricity delivered to the grid, with the exception of mineral resource depletion.