Compressed Air Storage Could Be Better Than Batteries

Compressed air energy storage systems can be used to store large quantities of power for weeks at less than the cost of batteries.
Published: Fri 08 May 2015

Compressed air energy storage (CAES) is becoming a serious contender in the energy storage market which is set to reach $21.5 billion by 2024. The current value of the market is $605.8 million.

Compressed air storage- a strong competitor

Used to power roller coaster rides, jackhammers and medical equipment, compressed air is up against some serious contenders like Tesla Motors which has just unveiled a suite of batteries to store electricity for households, businesses and utilities. [Engerati-Tesla Batteries Trial in US.]

But, compressed air energy storage systems (CAES) may have an edge-the technology can be used to store large quantities of power for weeks at less than the cost of batteries. Jim Heid, vice president at Dresser-Rand Group Inc., a supplier of compressed air products, is pretty certain that CAES is the only technology that can provide bulk storage of renewable generation.

According to Rocco Vita, director of emerging technology at pipeline company Enbridge Inc., which operates solar and wind farms across North America, compressed air can store hundreds of megawatthours of electricity for weeks at a time whereas batteries are useful for smaller volumes for shorter periods.

According to Navigant Research, in less than a decade, annual investment in compressed air will reach close to $5 billion which will support more than 11GW of installed capacity and help renewable power developers match demand with supply.

The way it works is simple: electricity from wind turbines and solar panels run compressors that fill man-made caverns also used for natural gas storage. When the pressurized air is released, it drives turbines that provide clean power when the sun doesn’t shine and the wind doesn’t blow.

It’s also not a brand new technology-Dresser-Rand built one of the world’s two commercial compressed air systems in Alabama in 1991 and is currently working on other projects in Texas. In Alabama, Power South Energy Cooperative’s 110MW system stores enough energy from nearby power plants to power 110,000 homes. The world’s first commercial application of the technology was in Germany in 1978 with a 290MW plant.

Air storage needs improvement

Currently CAES systems return only about 60% of the power used to fill caverns. This is according to Dresser-Rand Group.

Sam Shelton, senior fellow at the Strategic Energy Institute at the Georgia Institute of Technology explains, “When you put in one unit of energy, you want to get one unit out. Air is not very dense so compression storage is low efficiency.”

Advancements in technology will boost efficiency and eliminate the need to heat the pressurized air with natural gas, reducing carbon dioxide emissions. Developers are improving above-ground vessels for smaller-scale applications.

“Overall it’s a market that has a couple of niches,” said Brian Warshay, an analyst with Bloomberg New Energy Finance in New York. “A lot depends on the location and the proximity to demand.”

Utilities recognise the value of CAES

Also, investment could be better. Investors, who may not understand the advantages of the technology or are concerned that air storage systems are inefficient, have been slow to commit, according to Alissa Oppenheimer, managing director at Chamisa Energy. Chamisa Energy, based in Santa Fe, New Mexico, is seeking to raise about US$400 million to build a compressed air project in the Texas Panhandle that can store wind energy at night and release it when turbines are still.

In Canada, Ontario’s grid operator wants to add 16MW of storage, including CAES, to store the supply surge from wind turbines and solar panels. NRStor Inc., which is bidding for the contract, expects the efficiency and cost of air storage to improve.[Engerati-Ontario Energy Storage Procurement Enters Next Phase].Were Ontario to add 1,000MW of compressed air storage, consumers would save C$8 billion ($6.6 billion) over 20 years, said NRStor Chief Executive Officer Annette Verschuren. With this system in place, stored air could turn turbines for as long as 300 hours.

NRStor sees the price of compressed air systems falling fall to one-tenth that of the expected $350/kWh cost of battery storage in 2022.