"Thermoacoustics" Cooks, Chills, Generates Elec.

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"Thermoacoustics" Cooks, Chills, Generates Elec.

Postby judasdisney » Tue Dec 25, 2007 11:02 pm

Stove cooks, chills and powers your mobile

A more versatile version of the wood fire will allow people to generate their own electricity as they cook, perhaps enough to sell the surplus power to other members of their community (Image: SCORE)
A stove that uses acoustic technology to cook and cool, and generates its own electricity, is being designed for developing communities in Africa and Asia.

The Stove for Cooking, Refrigeration and Electricity, or SCORE, could help improve the health and quality of life for the 2 billion or so people in the world who cook over open fires, its developers say.

When used in enclosed places, smoke from open fires can cause health problems. And the stoves can be notoriously inefficient.

A person can spend two hours a day collecting wood to burn in a fire that is so wasteful that 93% of the energy generated, literally, goes up in smoke.

"We make the burning more efficient so that they use less wood and have more time to spend on other things like education," says Paul Riley, the project director at the UK's University of Nottingham.

The efficiency comes from a technology known as thermoacoustics, which produces sound waves from heated gas and then converts them to electricity.

Wood is placed inside the stove and burned. The fire heats compressed air that has been pumped into specially shaped pipes located inside the stove's chimney and behind the stove.

The heated air begins to vibrate and produce sound waves. Inside the pipes, the noise is 100 times louder than a jet taking off.

Because the pipes are stiff and do not vibrate, the sound waves have nowhere to go. So outside the pipe, people hear only a faint hum.

Rear view of the stove showing cool box and electricity output (Image: SCORE)
At the end of a pipe, the sound waves vibrate a diaphragm attached to a coil of metal wires sitting inside a magnet.

As the wire coil vibrates, about 50 times per second, it generates an electrical current, which is captured by wires and converted to the proper voltage.

The stove has electrical sockets, where homeowners can plug in, for example, a mobile phone for charging. Or they can sell the electricity as a phone-charging service.

"In Bangladesh, people could use the electricity to power lights, radio or educational equipment, for example, computers," says Professor Choudhury Mahmood Hasan, chair of the Bangladesh Council of Scientific and Industrial Research.

For refrigeration, the heated, compressed air is sent through a different part of the pipe, where sound waves cause the air to expand. And as it expands, it cools to a temperature that can produce ice.

It takes about 2 hours of stove use to produce enough ice that will keep the fridge cold for 24 hours. But homeowners have the option of producing more ice to sell for income.

Riley and his team want to involve local universities to train a labour force that can build and manufacture most of the parts needed to make the stove.

In five year's time, they hope to be churning out about 1 million stoves a year that each sell for US$30-40.

[illustrations at link]
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