A curious phenomenon responsible for the "singing" made...
- From: Sam Wormley <swormley1@xxxxxxxxx>
- Date: Thu, 31 May 2007 15:47:38 GMT
Physicists SCORE for third world
http://physicsweb.org/articles/news/11/5/23/1
31 May 2007
A curious phenomenon responsible for the "singing" made by hot glass
vessels during the glass blowing process could soon provide the
world's poorest communities with everyday conveniences such as a
cooker, a fridge and a generator -- all combined within one unit and
powered by simple biomass fuels such as wood.
Scientists have long known that sound waves can be generated by
irregularly heating a pressurized gas. Now, a new £2m project called
SCORE (Stove for COoking, Refrigeration and Electricity supply) is
aiming to exploit this "thermoacoustic" principle to develop an
affordable and versatile wood-powered generator that will be capable
of both cooking and cooling food across the developing world where
access to power is severely limited.
The project is being run by leading UK and US researchers along with
the charity Practical Action, industry and universities across Africa
and Asia. "Though the physical principles are well-understood and the
technology has been used before to provide power sources or cooling
units on satellites, there has been no research into producing a
combined device that can be mass-produced at a reasonable price,"
said SCORE researcher Mark Johnson of the University of Nottingham.
In the planned appliance, wood is burnt beneath a gas-filled pipe
containing a porous "stack" of small parallel channels. As the gas
heats up, it creates a temperature gradient across the stack. This
causes the gas molecules to oscillate back and forth against the
channel walls, exchanging heat and producing areas of high and low
gas pressure, which generate intense sound waves like a singing
kettle. Then, as the gas is constantly shifting to and fro between
the hot and cold sections of the pipe, it begins to "rhythmically"
compress and rarefy, thus enhancing the sound waves.
These sound waves can be harnessed in a linear alternator -- akin
to a loudspeaker operating in reverse -- which converts them into
electricity. However, they can also be passed to another
thermoacoustic engine working backwards to generate a cooling effect.
Here, the gas effectively picks up heat from one end of the pipe,
transports it, and drops it off at the other. The ensuing cool part
can then be used as a refrigerator. Not surprisingly, the heat from
the burning wood can also be used as a conventional cooker.
According to SCORE project director Paul Riley, the use of
thermoacoustics avoids moving parts, which will make the device far
more reliable than petrol or diesel generators. Moreover, it will
produce fewer pollutants and use wood far more efficiently than open
fires, which are the primary cooking method for two billion people
worldwide. The target is to produce the device for a mere £15 to £20
-- less than a tenth of what it currently costs to supply
electricity to a rural area.
Riley and his colleagues are now recruiting researchers so the
technology can be refined. They hope to produce their first prototype
in 18 months, with field trials and mass distribution of the devices
in target communities by the end of the five-year project.
.
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