Cheap turbine makes most of wind

A question put to an Oxford physicist by one of his students has led to the invention of a cheap domestic wind turbine that gets the most out of variable wind power.

As this Guardian article explains John Gregg of Oxford University's Department of Physics specialises in spintronics and magnetic instrumentation but, as part of an introductory physics course, a student asked: How can an induction motor work as a generator?

In trying to find a satisfactory answer John discovered that the sort of simple induction motor used in many domestic appliances could be turned into a cheap machine for turning wind energy into power.

The real breakthrough came when he realised that the heating elements in hot water tanks aren't bothered about variable voltages or frequencies - one of the barriers to manufacturing cheap and efficient conventional wind turbines. He told The Guardian's Michael Pollitt: 'That's why we can make it cheaply and why it performs well because we are not handcuffed by the necessity to deliver 240V 50Hz.'

At the heart of the turbine is a 7.5kW induction motor that generates power continuously, feeding it into the home hot water system with any surplus energy channelled into central heating through a heat exchanger.

John explained: 'Because the generator is configured as a constant power source and acts effectively as a generator and a continuously variable electronic gearbox, the turbine aerofoils operate on the peak of their performance curves at all times, and all the power they deliver is harvested and channelled to the load. So, the diminished wind power that you get at low altitude is used to maximum effect.' 

The team who worked with John to develop and patent the new turbine through Oxford's Oxford University Innovation (they are currently setting up a spinout called RenewOx) believe that the system could generate up to 60 per cent of a household's domestic energy needs.

The turbine could be mass-produced for a very low manufacturing cost and could potentially pay for itself in between 3-7 years (a massive improvement over conventional turbines that take up to 50 years to pay for themselves).

As John comments, this just goes to show how teaching smart undergraduates can challenge tutors and inspire exciting new projects - and that those who shun undergraduate teaching to concentrate on research just might be missing out.

The turbine was developed by John Gregg and built by Reg Bendall of the Clarendon Laboratory. It uses a 10 kilowatt set of blades supplied courtesy of Eirecomposites.