Storing Wind Energy Underground

Wind is the fastest growing energy source in the United States. Over the last five years, wind energy output has increased tenfold. Unlike most other forms of energy used to produce electricity, wind is a variable energy source. Some wind energy may be wasted when too much energy is produced and more energy might be needed when there is not ample wind available.

A very promising technology is being developed called compressed air energy storage (CAES) that can store large quantities of wind energy. Surplus wind energy is used to pump air into layers of porous sandstone in the earth below. This underground cavern is sealed with dense shale and acts like a huge balloon. When demand for energy increases, air flows up into a natural gas-fired turbine, boosting its efficiency by 60% or more.

This technology is being implemented at the Iowa Stored Energy Park in Dallas Center, Iowa. The energy park is scheduled to be complete in 2011 after 8 years of construction. This 268-megawatt system will cost $200 million to construct, with funding from the Energy Department and municipal utilities across Iowa, North Dakota, South Dakota and Minnesota.

Batteries are also being developed that can store wind energy. American Electric Power and Siemens Wind Power are experimenting with large-scale batteries that could store a megawatt of energy. Such technologies are very pricey and could have a high environmental price tag and have a much smaller storage capacity than CAES.

The future looks bright for compressed air energy storage and wind energy. Being able to store off-peak wind energy until demand and electric rates are higher allows wind energy to be a more lucrative and consistent energy source.