It will cool the first container to around -160degC while heating the other container to around 500degC. In principle, this is same to but much bigger than the heat pump driven by electricity in a domestic fridge to chill the inside of the fridge and warm the back. Unlike a domestic refrigerator, which generally utilises a range of chemical working fluids, the Isentropic machine can use air or any other gas with significant implications for the reduction of harmful atmospheric chemicals.
“Britainfaces a looming shortfall in electrical generating capacity,” explains Jonathan Howes, Isentropic’s Technical Director. “Even now, the UKis not making efficient use of its power stations and yet we’re all being urged to use energy more efficiently. Building electricity storage would allow existing power stations to be used much more efficiently, reducing the need for new ones.
“Although we have sufficient electricity in total, a shortfall in generating capacity means we won’t have enough electricity at peak times.We already have more capacity than we need at night. Being able to store that excess night-time capacity and feed it into the grid during the day would allow the same number of power stations we have now to cope with greatly increased peak demand, rather than switching on inefficient and dirty generating plants to cover peak times as happens at present.”
The storage containers hold large volumes, so this heat and cold can be stored for a considerable time. When discharging the process is reversed and it acts as a heat engine with the heat from the hot container transferring back to the cold container via the machine and releasing most of the energy originally used in charging. This is used to drive a generator to release the stored energy as electricity.
With Isentropic’s technology, around 75% of the energy supplied to the system as electricity can be returned as electricity. This is comparable to pumped hydro electrical storage. However, the added advantage is that the engine and stores use 300 times less land and are not dependent on geography, so can be installed anywhere.
Told it would not be able to achieve the low pressure losses and internal system efficiencies it was seeking, Isentropic has proved the sceptics wrong by a considerable margin and now has its second prototype running. The next step is to build a demonstration storage plant for which it is currently looking for investor funding of GBP6.5 million.
