The 'Searaser' uses the power of the ocean to pump water inland for electricity generation. Mark Anslow reports on the simple invention that could soon be making waves in renewables. From the Ecologist , part of the Guardian Environment Network

Alvin Smith had his eureka moment not in the bath, but in the swimming pool. 'I was swimming round the pool, making little waves, and it struck me how much power there was in the displacement of the water,' he remembers. 'You think of a 500-tonne boat: a wave comes along, lifts that whole boat, and then drops it down again. You must be able to harness some of that, I thought.'

His subsequent invention would have made Archimedes proud, and should be making the renewables industry very excited.

Dubbed 'Searaser', it consists of what looks like a navigation buoy, but is in fact a simple arrangement of ballast and floats connected by a piston. As a wave passes the device, the float is lifted, raising the piston and compressing water. The float sinks back down on the tail of the wave on to a second float, compressing water again on the downstroke.

What is particularly clever about Searaser, however, is its simplicity. Where most marine energy devices have sealed, lubricated innards and complex electronics, Searaser is lubricated entirely by seawater, has no electronic components and is even self-cleaning. Smith describes it as 'Third-World mechanics', but this belies the sophistication of the concept.

'The beauty of it is that we're only making a pump, and bringing water ashore,' he explains. 'All the other technology needed to generate the electricity already exists.'

Searaser is designed to pump water either straight through a sea-level turbine to generate electricity, or up to a clifftop reservoir, where the water could be stored until needed, then allowed to flow back down to the sea through turbines, generating electricity on demand.

The second option is the one about which Smith is most passionate. By effectively storing the energy generated by Searaser to be used on demand, his system would solve a problem that dogs almost all renewable technologies – their variability. Energy that can be summoned at will is not only more valuable, but also allows the grid to compensate for other, less easily controlled renewables such as wind and solar.

Early trials of the prototype Searaser, one of which was completed in April, have proved encouraging. Despite being less than a tenth of the size of the version he hopes will eventually be supplying power to our homes, Smith's homemade machine managed to pump some 112,000 litres of water a day during the trial, at times operating from waves a mere 6in high.

The eventual machine will be capable of generating 1 megawatt of electricity – enough to supply some 1,700 homes – at prices that the team behind Searaser believe will be lower than most other renewable technologies.

As an intermediate step, a trial of two midsize machines should go ahead towards the end of this year, with a university invited to monitor the trial and provide independent accreditation of the results. Although these machines won't generate electricity (they will simply pump water through a flow meter to determine their potential) they will demonstrate whether the technology can work for prolonged periods and in rough conditions.

For Smith, however – a man who could use a welder by the age of eight – the incremental steps between prototype and commercial deployment seem almost an irritation. His vision is already far advanced, and includes using the pressurised saltwater generated by Searaser to produce drinking water, using the same reverse osmosis process used in conventional, energy-hungry desalination plants.

'All you'd have to do is reduce the size of the piston and increase the size of the floats to increase the pressure,' he explains.

He has also put plenty of thought into how he would persuade planners and landowners to allow him to build reservoirs on top of cliffs to provide the energy storage for Searaser.

'The planning will frighten everyone,' he says, 'but if you were trying to produce as much energy from wind turbines, they'd be very visible; a reservoir you'd only see from above.'

Smith has also put thought into how the reservoir could be made as water-tight as possible – vital to avoid saltwater leaching into soils. By double-lining the reservoirs and including an outlet pipe in between the two linings, you would instantly be able to see if the uppermost lining had a puncture by watching the end of the outlet pipe.

'If you saw any water coming out, you'd know you had a leak and you could drain down the reservoir and sort it out,' he says.

Beyond being simply functional, however, Smith believes the reservoirs could be beautiful, providing recreational spaces for watersports or sites for shellfish farmers. 'I bet the birds would love it, too,' he adds.

Although Searaser is clearly a commercial project and Smith hopes to see a return on his patents, he is also keen to see the technology deployed abroad, given that its simplicity lends itself to installation and maintenance in the less-industrialised world.

'It's a modular system: a community could start off with two or three machines, and expand as necessary. It can go round the globe, it really can,' he says.

• Mark Anslow is the Ecologist's News Editor. This article appeared in the June issue of the Ecologist, part of the Guardian Environment Network