An oven-fridge-generator powered by sound
Several UK universities are teaming to develop an inexpensive all-in-one appliance for developing countries. In "Burning wood to power fridges," Nature reports that the SCORE (Stove for Cooking, Refrigeration and Electricity) project will use "thermoacoustic technology to convert biomass fuels, such as wood, into energy to power the appliance." In fact, this multipurpose device will be powered by sound waves. Thermoacoustic technology has been used before for expensive applications like cooling units on spacecrafts. But this innovative stove could be useful for the two billion people who use open fires as their primary cooking method.
The above diagram shows the various components of this all-in-one cooker, fridge and electricity generator (Credit: Paul Riley, SCORE project leader). Here is link to a page containing other pictures about SCORE project.
Here are more details about the SCORE device given by Nature.
In the SCORE device, says the project director Paul Riley at the University of Nottingham, UK, "burning wood heats a gas-filled pipe at one end. The gas moves from the hot part, where it expands, to the cold part, where it contracts. The pipe then resonates rather like an organ pipe." This produces acoustic pressure waves, which can be harnessed to produce electricity in the reverse process to how a loudspeaker turns electrical signals into vibrations.
The sound waves are also used to drive a second engine that operates as a heat pump to remove heat from a nearby refrigeration unit. And the heat from the burning wood can also be used for cooking in a conventional cooker stove. The fridge and the cooker are connected by "the pipes necessary to carry the hum," says Riley — but are kept apart so that the heat from the stove doesn't interfere with the cooling. The system will only generate electricity and cool the fridge while it is operating as a stove.
The University of Nottingham gives more details about the thermoacoustic technology used to build this stove in this news release (May 10, 2007).
The concept of the proposed device is based on proven thermoacoustic engines and refrigerators developed for applications such as combustion-fired natural gas liquefaction and radioisotope-fuelled electric power generation. Los Alamos Laboratories, in collaboration with several industrial partners, has played a lead role in the development of thermoacoustic technology.
Using thermoacoustic technology is a more efficient way of using wood as a fuel than using an open fire to cook. It produces less pollutants. The device will also have few moving parts making in more reliable.
For more information, please visit all the links shown on the SCORE project home page. In particular, you should read the Score Research Summary and the Acoustic Stirling Heat Engine page at the Los Alamos National Laboratory.
Sources: Philip Ball, Nature, May 14, 2007; and various websites
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