Giant Gravel Batteries to Improve Renewable Energy Technologies
New Technology Could Offer Solution to Seemingly Unreliable Renewable Energy Technologies-
An avant-garde technology is being implemented into wind turbines and solar panels which may potentially offer secure energy storage even when wind and sunlight is not readily available. By allowing electricity to be stored while environmental elements are out of reach, giant-sized batteries made with gravel are anticipated to improve renewable energy generation and will dampen constant criticism of opponents who claim that the renewable energy technology is not economically viable. “If you bolt this to a wind farm, you could store the intermittent and relatively erratic energy and give it back in a reliable and controlled manner,” says Jonathan Howe, founder of Isentropic and previously an engineer at the Civil Aviation Authority. The gravel-based battery would, according to Isentropic, be capable of storing energy equal to that of the former all while using less space – and cash. The company’s technology begins with two silos filled with a pulverized rock such as gravel. Then, electricity is employed to heat and pressurize argon gas which is fed into one of the silos; and, by the time the gas escapes the chamber, it has cooled to an ambient temperature while the gravel itself is heated to 500°C (or 932°F).
The gas is then directed into the second silo where it expands back to normal atmospheric pressure. This stage acts as an oversized refrigerator – causing the gas and rock temperature inside the second chamber to drop to -160°C (or -256°F). Any energy originally produced by the wind turbines is stored as a temperature variation between the two rock-filled silos – so to release the energy, the cycle is reversed, and as the energy changes from hot to cold it powers a generator that makes electricity. Isentropic guarantees an energy efficiency of up to 80 percent and, because gravel is inexpensive, the cost of a system per-kilowatt-hour of storage would be between $10 and $55. According to Howe, the energy in the sizzling silo can be easily stored for extended periods of time; and by his calculations, a silo that stands 50m tall and was 50m in diameter would only lose half of its energy through its walls if left undisturbed for three years. David Bott, director of innovation programs at the Technology Strategy Board, one of the sponsors of the 2010 Clean and Cool trade mission said: “Isentropic have done something very exciting, by revisiting scientific theory and coming up with a new technology that answers the need to match the generation of electricity with its use. For instance, the system could enable the more efficient use of wind power, by storing the energy generated by a turbine until it is needed. We need ways to store the energy we generate when we have a surplus, so that it can be used when we need extra and this innovative new system could provide the answer.”