|Mr Gilmartin with his waterwheel invention|
It's a mechanical problem that's troubled scientists since Archimedes and the ancient Greeks but now an electrician has come up with a new invention that could help save consumers thousands of pounds in energy bills.
Scotsman Ian Gilmartin, 60, and his friend Bob Cattley, 58, both from Kendal, Cumbria have invented a mini-waterwheel capable of supplying enough electricity to power a house - for free.
The contraption is designed to be used in small rivers or streams - ideal for potentially thousands of homes across Britain. It is the first off-the-shelf waterwheel system which can generate a good supply of electricity from a water fall as little as 20cm.
Mr. Gilmartin, an electrician and inventor, was not prompted to think up his new device by high energy bills - he does not own a TV and has never lived in a house with electricity.
But he has a stream at the back of his house, the Beck Mickle, and with the help of Phd engineering student, Mr Cattley, now hopes to see the invention in the shops by the end of next year.
Mr. Gilmartin first began experimenting three years ago with yoghurt pots and wheelie bins in the stream, before test-running a proto-type. They took the results to the Lake District National Park, and secured a £15,000 grant from the organisation's sustainability fund.
The prototype has now been working successfully at St. Catherine's, a National Trust site near Windermere, opening up previously untapped energy. The waterwheel produces one to two kilowatts of power and generates at least 24 kilowatt hours of sustainable green energy in a day, just under the average household's daily consumption of around 28 kilowatt hours.
It will hope to cost around £2,000 to fully install - and will pay for itself in side two years.
The Beck Mickle 'low head' micro hydro generator could potentially provide electricity to more than 50,000 British homes and could be used industrially.
Mr. Gilmartin said: "While we cannot say this provides free electricity, because of the initial cost of buying the machine, it is expected to pay for itself within two years and then greatly reduce the owner's electricity bills after then."
Waterwheels of various types have been known since Roman times and hydropower was widely used in the Middle Ages, powering most industry in Europe.
But the energy produced from the flow of water depends on the height, or head, that the water falls.
A 'high head' like a traditional water-wheel, is large, expensive and needs civil engineering. But with 'low heads' - under a 18 inches, no one had yet invented a method of successfully recovering the energy generated.
Researchers have long sought out low cost technology to exploit the vast number of suitable low head hydro sites as a source of renewable energy.
A conventional waterwheel allows the water to escape prematurely as the wheel rotates, but the Beck Mickle Hydro generator contains the water for the full drop of the device, converting around 70 per cent of the energy into electricity.
Mr. Gilmartin explained, "This idea started off to answer the question, 'How do you recover energy from very, very low heads of fluid?'
"With a low head there is not very much flow, no velocity, the fluid has got to have speed, and the only way of doing it is with a water wheel, but they are big and expensive and need lots of civil engineering.
"I have come up with an answer and I don't know why anyone has not thought of it before."
Mr. Gilmartin added: "You have to have a good reason for not having one. There are enormous possibilities wherever there are water flows."