energy bursts
Mighty
Mite
Emergency
generators—the kind used to run some household appliances during
a blackout—now take up less space than a dishwasher. But what if
you needed a generator just to run a cell phone? Engineers at the Georgia
Institute of Technology in Atlanta now have an answer: a generator about
the size of a sugar cube.
The microgenerator produces electricity much the way a gigawatt-scale
power plant does. Magnets spinning near coiled wire induce an electric
current. Coupled with a gas-microturbine to make an engine, the magnet
turns some 100,000 times a minute to produce a little more than a watt
of power.
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| Small world: This tabletop microgenerator produced enough power to run a cell phone. |
At revolutions that fast, high-performance magnets tend to break under
centrifugal pressure. The Georgia Tech team, led by Mark Allen, overcame
this problem in part by sheathing the magnet in titanium.
Microgeneration is not a new idea, and research labs across the country
have been working on small-scale devices for years. But the Georgia Tech
team claims that theirs is the first microgenerator capable of powering
a small electronic appliance.
The system is expected to provide power for a longer time than a similarly
sized battery pack. The researchers project that a microengine system
such as theirs could eventually produce as much as 50 watts—enough
power to run a laptop. Sweet.
Waste Into Water
Island
communities have long been faced with a choice: scrimp on water or conserve
electricity. That's because the desalination plants that could
supply clean drinking water require lots of energy to run.
Now engineers at the University of Florida in Gainesville have developed
a means of operating a desal plant by using waste heat from an electrical
power plant. Rather than compete, both water and electricity can be made
from the same fuel.
Desalination on a commercial scale involves either distillation—
boiling saltwater and then condensing the resultant vapor—or reverse
osmosis, in which powerful pumps force water through special membranes.
James Klausner, a professor of mechanical and aerospace engineering, developed
an offshoot of distillation called mass diffusion. Pumps push saltwater
through a heater and spray it into the top of a column stuffed with plastic
slats. As the water trickles over the slats, warm air blows up through
the column and evaporates the water. A condenser wrings the water vapor
out of the blowing air.
Waste heat from power plants can be used to warm the water, Klausner says,
cutting energy costs. Based on data from an experimental prototype, a
diffusion desalination system hooked to a 100-megawatt power plant could
produce 1.5 million
gallons a day for about a quarter-cent per gallon.
Yukon Gas
As
the battle over the status of the Arctic National Wildlife Refuge still
rages, another Alaska wilderness has now slipped into the crosshairs of
energy developers. In December, the United States Geological Survey released
an estimate of oil and gas reserves in the Yukon Flats region that will
likely lead to calls for opening up the area to prospectors.
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Yukon Flats is a largely unsettled area about 100 miles northeast of
Fairbanks; the territory lies within an 11-million-acre national wildlife
refuge. The USGS assessed a 13,500-square-mile tract using new information
obtained by recent field and laboratory studies.
The estimates of as-yet-undiscovered oil reserves in Yukon Flats was fairly
low—only 173 million barrels. By comparison, the National Petroleum
Reserve on the North Slope contains more than nine billion barrels. While
the prospect of oil is probably too small to entice exploration at Yukon
Flats, the gas reserves are thought to be more substantial. At an estimated
5.5 trillion cubic feet, the undiscovered gas reserves might be developed
profitably. In fact, one of the areas studied lies within 75 miles of
the Trans-Alaska Pipeline.
This section was written by Editor Jeffrey Winters.
© 2005 by The American Society of Mechanical Engineers