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- Nowadays, an engine without moving parts
may seem like a useless device, but the Department of Energy's Los Alamos
National Laboratory has created just that - an engine that runs despite
this major incongruency.
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- This very simple, energy-efficient engine
without moving parts is known as the thermoacoustic Stirling heat engine.
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- "The efficiency of conventional
heat engines is limited by both the laws of thermodynamics and practical
concerns over the cost of building and operating complex engines,"
said researcher Scott Backhaus, who had a hand in developing the engine.
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- "Typically, the highest efficiencies
can only be obtained from expensive engines like the large turbines used
by electrical utilities. Our engine is neither mechanically complex nor
expensive," Backhaus said.
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- Scientists at the UC-run laboratory were
motivated to develop a more energy-efficient engine because of environmental
concerns including pollution, global warming and fossil fuels. Today,
most engines are internal combustion or turbine, which lead to such problems.
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- "A long time ago, a bunch of us
tried to decide how to remove moving pistons in heat engines and refrigerators,"
said Greg Swift, another researcher who helped develop the engine.
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- "It is a very practical issue because
of cost and maintenance problems. We've been trying to figure it out for
18 years," he said.
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- The central concept behind this engine
is the expansion and contraction of a gas when it is heated and cooled.
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- The engine consists of a long, baseball
bat-shaped resonator with an oval handle on the lower end, filled with
compressed helium.
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- The gas then goes through numerous steps
during which the pressure is raised within the engine, resulting in the
expansion of the gas. The pressure is then lowered, causing the gas to
contract.
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- By applying pressure to the helium through
a heat exchanger located on the handle, the engine creates acoustic energy
in the form of sound waves. This energy can be used to power refrigerators
or to generate electricity.
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- A residential appliance that uses hot
water is normally attached to a water heater. But, instead of heating
gas to run the appliance, it may be possible to burn gas, creating acoustic
energy to run the appliance.
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- By using an acoustic magnet in a coil
of copper wire, the waste heat produced by the appliance could be used
to heat water. This process is environmentally friendly and up to 30 percent
more efficient than most internal combustion engines, Swift said.
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- "Small, low-cost engines like this
could be used in homes for cogeneration," Swift said.
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- "They could be used to generate
electricity while at the same time producing heat to warm the home or for
hot-water heating," he said.
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- The developers have been working with
industrial partners to produce a combustion-driven, thermoacoustic refrigerator
that liquefies natural gas.
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- When oil is pumped, gas bubbles out of
the ground. In a remote oil field, there is no economical way to take
the gas to market, so the oil companies burn it. This creates pollution
and greenhouse gases. But, if a fraction of the gas was burned to run
an acoustic engine, the gas could then be liquefied.
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- By liquefying natural gas, it can be
more easily transported to locations with pipelines that can utilize gas.
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- Backhaus and Swift are also working on
ways to use solar power to heat the engine and generate electricity.
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- The benefits of an engine of this sort
arise out of the fact it has no moving parts. It is cheap to build and
it requires low maintenance because there are no parts to wear out.
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- But the main drawback of the engine is
that acoustic energy is not 1quite as useful for producing power as the
rotating shaft, the more common source of power in today's world.
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- "I am excited if it's going to work
for the environment and fix the problems we have caused," said first-year
undeclared student Nicole Josefson about the future engine. "But
I'm totally p3ssimistic. We need to change our ways and find a new way
to help."
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- Though researchers are unsure when this
engine will be available to consumers, Swift said it could be available
within a few years. - -
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