No iron ore, but
a lot of air
Looking at an
old mine, envisioning a power plant.
NEW MORGAN, Pa. - Bob Hoe and Ken
Broome are either fools or visionaries.
They recently signed a lease for an iron ore mine that has run out of
iron ore. A hole in the ground. A hole in the ground they'd never seen. A
hole in the ground that, by the way, is flooded by water a half-mile deep.
But even visionaries get nervous. "This is it?" Hoe asked
Broome the other day as they stood atop a concrete slab covering the shaft
of Bethlehem Steel's old Grace Mine. "There's a hole under
Hoe and Broome don't care about extracting ore from the rolling Berks
No. Thar's air in them thar hills.
Hoe, a Philadelphia developer, and Broome, a Reading engineer, have
formed a company that intends to pump the abandoned mine full of air by
night, and then release the pressurized air during the day to drive
turbines and generate electricity.
That may sound far-fetched, but an Alabama utility has been operating
such a compressed air system for more than a year using a cavern bored out
of a salt dome. Another plant has operated in Germany for 15 years.
The $75 million project might also be the first electrical generating
station that doubles as a tourist attraction.
That's because the owner of the mine, developer Raymond H. Carr, has
long-standing plans to build a Victorian resort and amusement park on the
4,200-acre property he bought eight years ago from Bethlehem Steel. His
other ideas for the tract, which last year became the independent borough
of New Morgan, include a housing complex, an industrial park and a garbage
Carr did not anticipate renting or using the excavations, which have
filled with water since Bethlehem stopped production in 1977.
"I thought that mine was something that was concreted shut to stay
shut forever," he said.
But when Hoe and Broome approached him with their notion, Carr not only
agreed to the lease, but also asked that the plant be included in any
potential tourist attraction at the site, which lies 45 miles west of
Philadelphia near the Morgantown interchange of the Pennsylvania Turnpike.
"It's going to be the most exciting thing to happen on the East
Coast," he said.
Compressed air systems are simply the latest method to store electrical
energy that is generated at night, when rates are low, and use it during
the day, when electrical demand and prices rise.
Some utilities, including Philadelphia Electric Co., operate water
storage systems that employ the same principle: Water is pumped into a
reservoir at night and then is released during the day to run generators.
Other utilities are building enormous batteries to store electricity
generated at night.
LIKE A SCUBA TANK
Hoe and Broome, who have collaborated on other energy projects, say
their system would be the first time a hard-rock mine was used like a
scuba tank to store compressed air.
The dense limestone contains about 2.7 million cubic feet of tunnels
and shaftways, some of them thousands of feet long and as deep as a
Broome, 68, an engineer who has long been interested in energy projects
- he built a hydroelectric generator at the Ontelaunee Dam in Reading and
has been involved in several other power projects - perked up five years
ago when he heard about the mine's potential.
He and Hoe, 47, who had worked in previous partnerships, formed the
CAES Corp. in 1989 - it stands for Compressed Air Energy Storage.
Since then, Broome has pored over underground maps and interviewed the
engineers who bored the 18-foot-diameter tunnels for transporting train
cars containing iron ore. The tunnels criss-cross the property at
But it was only recently that they signed the lease with Carr's
company, Morgantown Properties. The lease gives them five years to build
the plant, and then runs for 29 1/2 years once the plant is operating.
They say the plant would produce 110,000 kilowatts of electricity,
enough to supply 66,000 homes.
Broome and Hoe angered environmentalists several years ago by proposing
to build a 2,500-kilowatt hydroelectric generator at the Flat Rock Dam on
the Schuylkill near Manayunk (the project did not pan out).
They said that the air-compression system should have insignificant
The machines that pump the air underground would be conventional
electrical compressors, they said. And the turbines that power the
generators would be the same gas-powered machines that utilities use to
produce peak electrical power.
The use of underground chambers for energy storage is not novel. Oil
companies already keep petroleum reserves and pressurized natural gas in
Broome and Hoe have applied for a grant from the Electrical Power
Research Institute in Palo Alto, Calif., the research arm of the electric
power industry. The institute helped finance Alabama Electric
Cooperative's $65 million compressed-air operation in McIntosh, Ala.
"The key issue is cost," said James Birk, a scientist at the
research institute. "If you already have the cavern there, you're way
ahead of the game."
Broome and Hoe plan to seal off the ends of the vertical shafts and
tunnels to create a series of subterranean chambers. The concrete plugs
would prevent the pressurized air from escaping into porous rock where
iron ore was extracted with explosive blasts.
"The real significant unknown is whether this mine will hold
air," Hoe said. "We're confident it will."
Each night the plant operators would turn on compressors and pump air
into the mine until it reached a pressure of 1,000 pounds per square inch
(atmospheric pressure is 14 pounds per square inch).
During the day, the operators would open valves, causing a blast of air
to rush out and run the turbines.
As the air rushed out, it would expand rapidly and become very cold. It
would need to be heated with natural gas to prevent it from freezing the
Because the air would already be pressurized, the turbines would
consume about a third of the gas that a conventional gas turbine requires.
Still, energy storage systems like the one Broome and Hoe envision do
not conserve electricity. In fact, they use 20 percent to 30 percent more
energy than they generate.
They are attractive to energy planners because they use electricity at
night, when utilities like to keep their generators running because it is
more efficient than turning them off. And they produce power during the
afternoon hours, when utilities strain their generators to meet peak
"What we're banking on is the differential between peak and
off-peak power," Hoe said. "As long as the differential remains,
the economics work."
Hoe said that to secure financing, his venture would need to reach a
deal with a utility to buy the power.
Two utilities - Pennsylvania Power & Light Co. and Metropolitan
Edison Co. Inc. - serve the mine property. Philadelphia Electric's
territory is also nearby. The plant could also sell electricity to a more
Carr, the mine owner, says the tenants of his industrial park or his
Victorian village also might contract to buy the power.
Never short of ideas, Carr also saw potential uses for the seven-acre
water reservoir that Hoe and Broome want to build on the surface. The
reservoir would store water that would flow into and out of the mine as it
was alternately filled with and emptied of compressed air.
"The water would flow in and out of the reservoir like the
tide," said Carr, who envisions the water flowing through elaborate
channels, fountains and moving sculptures.
"You could sit there and watch the water ebb and flow."
project has never been built. Nor has the amusement park or the housing
development. But the garbage dump was completed at New Morgan.