Energy from mine is more than hot air

A team of researchers from the US Department of Energy's Sandia National Labs are working with Haddington Ventures and its subsidiary Norton Energy Storage LLC to determine the feasibility of using a 2,200-foot-deep inactive mine in Ohio, as the storage vessel for a compressed air energy storage power plant.

'The intent is to cycle air pressure into the mine using compressors during off-peak electrical power at times like evenings and weekends to increase air pressure in the mine,' said Sandia researcher Steve Bauer. 'During the daily peak needs for electricity, air pressure will be bled off through modified combustion turbines to generate electricity. The energy is stored as pressure, but the mine must hold air to store the pressure.' Working pressures in the 'air-tight' mine will range between about 1,600 and 800 psi.

While the concept of compressed air energy storage is more than 30 years old the Norton plant will be the first in a limestone mine.

Sandia's role has been to characterise the rock mechanics and air-flow properties of the limestone and overlying shale in response to pressure cycling. The characterisation included analyses to assess the geologic, hydrologic, and rock physics data.

The Sandia team found that the mine consisted of a very dense rock with low permeability. It was stiff and strong and had few, if any, natural fractures.

'This all led to the conclusion that the mine would likely hold air at the required storage pressures and would work well as an air storage vessel for a compressed air energy storage power plant,' Bauer said.

The power plant will be built in units brought on line in increments of 300 megawatts as units are completed. Up to about 2,700 megawatts will be built, which will be enough generating capacity for about one million homes.

The power from the plant will not be sold directly to consumers. It will generate wholesale electric power for sale to utilities and marketing companies for use during peak energy usage times.

In addition to providing more power during peak times — and possibly helping Ohio and the surrounding region avert blackouts — the compressed air energy storage power plant has the advantage of being environmentally friendly.

'During electric generation, some natural gas will be burned to super-expand the compressed air,' Bauer said. 'When at its full production stage of 2,700 megawatts, it will produce the same amount of emissions as a 600-megawatt gas-powered combustion turbine power plant.'

Haddington and Norton Energy plan to have the plant on line in two years.