Wind in Reserve

Wind in Reserve

Nov 14 - Fiscal Notes

Texas looks to improve alternative energy rank

Each year, Texas generates more electricity from wind than any state except California. While researchers have discovered the secret to pulling kilowatts out of wind in the Lone Star State, they still haven't found a way to make that power source available at any time. A new process could make that feasible.

The Texas Comptroller's State Energy Conservation Office (SECO) and Houston-based Ridge Energy Systems (RES) are studying the possibility of storing compressed air in salt domes beneath the ground-a process called compressed air energy storage (CAES). Air stored in salt domes is used later to generate electricity.

Holes

The CAES process uses caverns left behind when miners finish mining and clearing salt domes. In CAES, generators compress air into the cavern and hold it under pressures between 1,000 and 1,500 pounds per square inch (PSI), according to Nisha Desai with RES. By comparison, scuba tanks hold air at about 3,000 PSI.

"The caverns in salt domes have been used for more than 50 years to hold things like natural gas and oil reserves," said Desai. "There's a whole industry that revolves around storage in salt domes. With natural gas, there's a lot of industry experience in holding gas at high pressure."

Houston-based PB Energy Storage Services Inc. (PB ESS) and its former German parent company designed the only two operating CAES facilities in the world in Alabama and Germany.

"Because of the abundance of salt formation and wind energy that exists in Texas, CAES can substantially expand the state's future electric generation capability by providing large, flexible and reliable electric power at competitive prices," said Roger Blair, who heads U.S. operations for PB ESS.

SECO and RES are beginning a study to identify the value of a potential CAES site in the Texas Panhandle. The study, which will examine whether a CAES facility could benefit the area, is expected to last through April 2005, said SECO's Pam Groce.

"Capturing the wind to generate electricity has made a huge impact in Texas, but as you know, the wind doesn't always blow," Groce said. "SECO is interested to know if a CAES plant will add more value to this already valuable resource."

A $70,000 grant from the U.S. Department of Energy will help fund the study, which will also receive funding from the Alternative Energy Institute at West Texas A&M University.

A mighty wind

Texas produces almost 1,300 megawatts (MW) of wind-generated electricity each year, according to the American Wind Energy Association. A megawatt, or 1 million watts, can provide electricity for about 300 homes over the course of a year. The state's transmission lines are only expected to transport about half the wind-generated electricity in Texas by the end of 2005, according to the Electric Reliability Council of Texas.

RES is working on a CAES project with an estimated price tag of up to $225 million near McCamey, Texas, which RES has dubbed the "Wind Capital of Texas." In 2002, the inability to transfer all of the 758 MW generating capacity of wind farms in the McCamey area cost operators 380,000 MW hours, according to RES. An average U.S. household uses about 12 MW hours per year, according to Duke Energy of Charlotte, N. C.

These energy shortfalls in the McCamey area cost operators about $30 million in 2002, according to an August 2003 report by the Lower Colorado River Authority.

Caverns of air

How it works

In the CAES process, an electric air compressor drives air into the cleared salt dome cavern, holding it under pressure. When electricity demand warrants more power than is available from wind generation in an area, plant operators bring air from the cavern back to the surface, where it is heated with natural gas, causing it to expand and rush through turbines that power a generator. Electricity created by the generator can then be delivered to customers.

Alabama Electric Cooperative's plant is a 110 MW facility. Its cavern sits 1,500 feet below the earth's surface and can hold 19 million cubic feet of air.

Pending the outcome of SECO's Panhandle study, it could be several years before any air is pumped into a CAES site in the area, said Desai.

Clint Shields