Cape Wind Will Harness Energy, But Are Giant Gravel Batteries The Secret To Storing It?
Denmark, China, Antarctica, and now the Nantucket Sound.
These locations all have one thing in common; they are ideal sites for generating enough electricity from strong ocean breezes to power hundreds of thousands of homes.
The subject of an almost decade-long debate, U.S. Secretary of the Interior Ken Salazar announced Wednesday that he had finally approved the construction of America’s first offshore wind farm on Horseshoe Shoal in Nantucket Sound off the coast of Massachusetts.
Cape Wind President Jim Gordon greeted the news with obvious jubilation. “It allows our nation to harness an abundant and inexhaustible clean energy source for greater energy independence, a healthier environment and green jobs,” Gordon said of Salazar’s decision.
While the fight to approve construction might be over, the challenge of proving that wind is a reliable source of residential and commercial electricity is just beginning.
A favorite criticism of alternative energy doubters is that “the sun doesn’t always shine, and the wind doesn’t always blow.” Although wind farm enthusiasts like to refer to offshore wind power as ‘inexhaustible’, provisions must be made for times when power generation is intermittent.
Theories about power storage in the past have varied widely.
Researchers have suggested the possibility of creating a network of small, energy-dense batteries in tens of millions of homes, or filling underground caverns with compressed air that can be released gradually to generate electricity by turning a turbine.
Most recently, researchers from Cambridge University have suggested that while the power might might be blowing in the wind, the secret to storing it resides in common rocks- gravel, to be exact.
The Guardian reports that, by filling two silos with a pulverised rock, such as gravel, electricity from offshore wind farms like Cape Wind could be stored onsite for up to three years with with no maintenance and only marginal losses.
“Electricity would be used to heat and pressurise argon gas that is then fed into one of the silos. By the time the gas leaves the chamber, it has cooled to ambient temperature but the gravel itself is heated to 500C.
After leaving the silo, the argon is then fed into the second silo, where it expands back to normal atmospheric pressure. This process acts like a giant refrigerator, causing the gas (and rock) temperature inside the second chamber to drop to -160C.
The electrical energy generated originally by the wind turbines originally [sic] is stored as a temperature difference between the two rock-filled silos. To release the energy, the cycle is reversed, and as the energy passes from hot to cold it powers a generator that makes electricity” (Guardian).
Isentropic, the private technology company responsible for the silo concept, claims that the giant gravel “batteries” would be 80% more efficient than hydro-electric dams, and, because gravel is cheap, the cost of a system per kilowatt-hour of storage would be between $10 and $55.
A February report published by Charles River Associates, a leading economic consulting firm, found that when completed, Cape Wind will place downward pressure on the wholesale clearing price of electricity by reducing operations of higher priced and polluting fossil fueled units. As a result, wholesale electric prices for the New England region are expected to decrease by $4.6 billion over 25 years.
If Isentropic’s future plans to build a 100kw demostrator facility are successful, we might soon see more wind farms like Cape Wind approved without a ten-year debate over cost-effectiveness.
Image Credit: Flickr Creative Commons - phault