Deep shaft plan for pumped storage schemes
NEW PRODUCTS and INNOVATIONS Deep shaft plan for pumped storage schemes Apr 2010
Patrick Reynolds, Freelance Reporter
Research between a venture capital-backed US energy start-up company and some tunnelling machine manufacturers is underway to help develop excavation technology for a new pumped storage system that would eventually need shafts sunk up to 2,000m deep.

Deep shaft power generation

California-based Gravity Power, LLC, is seeking a patent for a pumped storage system that would work with a pair of deep shafts, one large and one small, joined at the top and bottom to form a closed circuit of water, and operate on a simple piston action. The larger shaft would have a diameter of at least 6m, and up to a possible 10m, for commercial operations, and be sealed to contain water and a 6,000 tonne concrete weight.
Using the pumped storage concept, cheap energy would be used to pump water into the larger shaft and raise the heavy weight, and so lock-in the potential energy. At times of peak demand, the water would be allowed to flow back to a turbine under the pressure of the weight, working in a slow, steady plunger-like action.
Deep bore technology currently rests mainly with the oil and gas exploration industries with holes being drilled to well beyond 2km depth. But the shafts bored are too narrow. The mining sector also has the capability of sinking deep shafts but it is to the tunnelling sector that Gravity Power is looking for a major breakthrough for the shaft system.
Details are being kept confidential. There is no public announcement as yet of discussions with tunnelling companies, agreements made, commercial terms, or the nature of the tunnelling technology concepts being examined.
Gravity Power, LLC's, Vice President Chris Grieco, told TunnelTalk: "We have discussions ongoing with more than one firm and some discussions are farther along than others. The nature of the work is competitive."
A field demonstration of the modular system is planned for Texas later this year with the pair of shafts to be excavated to 100m deep, which is a fraction of the minimum commercial depth of 500m. The location has yet to be decided. In a second phase of trials the depth of the shafts is to be extended.
The configuration of the shaft pair - the smaller shaft being about 2m diameter - replaces an earlier concept for a single shaft that would hold internal pipelines to allow the necessary water circulation system.

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