From: Gina Miller (nanogirl@halcyon.com)
Date: Thu Jun 03 1999 - 23:35:25 MDT
Energy-Efficient Engine With No Moving Parts Developed
In a step toward finding alternatives to conventional engines, scientists at
the Department of Energy's Los Alamos National Laboratory have developed a
remarkably simple, energy-efficient engine with no moving parts. The engine
is described in a paper published in today's issue of Nature.
Pollution concerns, global warming and shrinking fossil fuel reserves have
focused world attention on how engines generate electrical and mechanical
power. Engines with higher efficiency help conserve fossil fuels and reduce
emissions by consuming less fuel to generate an equivalent amount of power.
Today most engines are internal combustion or turbines.
In today's Nature paper, Los Alamos researchers Scott Backhaus and Greg
Swift describe a thermoacoustic Stirling heat engine consisting of a long,
baseball-bat-shaped resonator with an oval "handle" on the lower end. Filled
with compressed helium and constructed of inexpensive steel pipe, the device
is highly reliable and decidedly low-tech.
By applying heat to the compressed helium contained within the system
through a heat exchanger located on the "handle," the engine creates
acoustic energy in the form of sound waves. This intense acoustic energy can
be used directly in acoustically powered refrigerators or to generate
electricity. The power production process is environmentally friendly and up
to 30 percent efficient while typical internal combustion engines are 25 to
40 percent efficient.
According to Backhaus, "the efficiency of conventional heat engines is
limited both by the laws of thermodynamics and practical concerns over the
cost of building and operating complex engines. 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."
The idea behind the engine comes, in part, from the Stirling cycle where a
confined volume of gas expands at high pressure and contracts at low
pressure, thereby doing work on the surrounding environment. The expansion
and contraction of the gas is driven by the absorption and rejection of heat
at the engine's hot and cold heat exchangers.
The discovery of this principle by Robert Stirling in 19th century Scotland
laid the groundwork for the conventional Stirling engine in which a fixed
amount of helium is compressed in a cool chamber and then transferred to a
chamber heated by an external burner. As the gas expands it drives a piston
that delivers energy. As it cools it returns to the cool chamber and the
cycle begins again.
According to Swift, there are many possible applications for his engine.
"For instance, small low-cost engines like this could be used in homes for
cogeneration. That is, they could be used to generate electricity while at
the same time producing heat to warm the home or for hot-water heating."
Because the thermoacoustic Stirling heat engine contains no moving parts and
is constructed of common materials, it requires little or no maintenance and
can be manufactured inexpensively.
The future seems to hold great promise for the thermoacoustic Stirling
engine. Backhaus and Swift are working on ways to use solar power to heat
the engine and, in turn, generate electricity. There may even be uses for
the exhaust heat from internal combustion engines to power a car's air
conditioning.
The Los Alamos group is also collaborating with Cryenco of Denver on a
combustion-driven thermoacoustic refrigerator that liquefies natural gas.
"Associated" natural gas that is currently flared (burned off) at remote oil
wells worldwide creates pollution and greenhouse gases without producing any
useful energy. Liquefying the natural gas makes it economically feasible to
transport the gas to locations with existing pipelines.
The research is funded by DOE's Office of Basic Energy Sciences.
Los Alamos National Laboratory is operated by the University of California
for the Department of Energy. - By Todd A. Hanson
Gina "Nanogirl" Miller
Nanotechnology Industries
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http://www.nanoindustries.com
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nanogirl@halcyon.com
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"Nanotechnology: solutions for the future."
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