Researchers have developed a device that harnesses the power of the sea to push water uphill to provide cheap renewable electricity.

According to a report in The Times, the invention, known as ‘Searaser’, is designed to pump water hundreds of feet above sea level from where it can gush downhill to drive hydroelectric generators.

Pumping is made possible by the motion of waves lifting the device, as it floats in the sea, and gravity bringing it down again in the wave troughs.

Alvin Smith, the engineer who developed Searaser, has already envisaged alternative uses of the device such as pumping desalinated water inland for irrigation in dry countries.

However, he said its main use would be to help Britain to end its reliance on fossil fuels and so reduce the man-made emissions of carbon dioxide that are blamed widely for causing, or at least contributing significantly to, climate change.

If successful, the device could help Britain to meet its target of getting 15 per cent of its energy from renewable sources.

According to Smith, one of the big advantages of the wave device is that the turbines that would be used to generate electricity are a proven technology and have been in use for years in hydroelectric installations in hilly areas where water can be held in reservoirs.

The wave pump consists of two floats, one above the other, fitted to a double-acting piston. Water is pumped as the floats are forced together and apart by the motion of the waves.

Chains and weights fix the device to the sea floor and the pump is able to operate in water as shallow as 30ft (9m) as well as in extreme weather conditions.

Each of the pumps has a capacity of just 0.25mw, but they are expected to be used together in their dozens, or even hundreds, side by side along the coast or further out at sea.

A prototype has just completed tests in which it pumped water more than 160ft (50m) uphill through a pipe the diameter of a saucer.

The full-size device is expected to pump water through a pipe the diameter of a dustbin lid up at least 650ft (200m).

A series of reservoirs would be built, and in some areas would be reopened, at the top of coastal cliffs and hills to store water until it was needed to generate electricity.

Smith, and his colleague Geoff White, have estimated that one full-size device would be able to pump enough water to keep 470 homes supplied with electricity