Energy storage based on reversible heat pump

At the moment, grid managers match demand by generating just enough electricity at any given time. But power from renewable sources, particularly the wind and the sun, is intermittent.

Nevertheless, as costs come down and efficiency increases, renewable energy is being used more widely. Solar power is already the cheapest form of electricity in most sunny climes, and in America the Department of Energy wants it to provide 27% of the country’s electricity by 2050, up from less than 1% today. But without efficient grid-scale storage, costly backup generation will be needed to keep the lights on.

A number of technologies are being developed to store energy on the grid, such as flow batteries which can accumulate energy in liquids and discharge rapidly. Giant flywheels and supercapacitors are also being explored.

Isentropic has developed several prototypes of pumped-heat electricity storage (PHES), a system based on a heat pump—a device like an air-conditioner that transfers heat from one place to another. In this case, though, the device is reversible, and when the heat flows back it works like a heat engine, converting thermal energy to mechanical power like a car engine.

The firm is now completing a demonstration unit with an output of 1.5 megawatts for further testing at its factory near Fareham, on Britain’s south coast.

Source: Monitor: Pumping heat