Science > Physics > New Desalination Technology Taps Waste Heat from Power Plants
| Topic: |
Science > Physics |
| User: |
"Dr. Jai Maharaj" |
| Date: |
08 Jan 2005 10:18:21 PM |
| Object: |
New Desalination Technology Taps Waste Heat from Power Plants |
New Desalination Technology Taps Waste Heat from Power Plants
Forwarded message from Fidyl <fidyl@yahoo.com>
[ Subject: New Desalination Technology Taps Waste Heat from Power Plants
[ From: Fidyl <fidyl@yahoo.com>
[ Date: Sat, 8 Jan 2005
New Desalination Technology Taps Waste Heat from Power Plants
Source: Clean Edge News
December 28, 2004
http://www.cleanedge.com/story.php?nID=3353
University of Florida researchers have developed a desalination
technology that can tap waste heat from electrical power plants as
its main source of energy, an advance that could significantly reduce
the cost of desalination in some parts of the world.
"In the future, we have to go to desalination, because the freshwater
supply at the moment can just barely meet the demands of our growing
population," said James Klausner, a UF professor of mechanical and
aerospace engineering, whose research was funded by the U.S.
Department of Energy. "We think this technology could run off excess
heat from utility plants and produce millions of gallons each day,"
said Klausner, lead author of an article on the system that appears
in the current issue of the Journal of Energy Resources Technology.
He co-invented the technology with fellow UF mechanical engineering
professor Renwei Mei.
More than 7,500 desalination plants operate worldwide, with
two-thirds of them in the Middle East, where there often is no other
alternative for fresh water, Klausner said. The technology is less
common in North America, with plants located mostly in Florida and
the Caribbean producing only about 12 percent of the world’s total
volume of desalinated water, he said. U.S. residents get less than 1
percent of their water from desalination plants, he said.
The need for desalination is likely to grow, however, as the
population increases and residents consume more fresh water. In
Florida, for example, desalination has been touted as one solution
for metropolitan areas where freshwater resources are becoming ever
more scarce. With more than 97 percent of the Earth’s water supply
composed of salt water, desalination is even more urgent in
developing nations, such as China, Klausner said.
"China has a large and growing demand, Japan has a large demand, the
Middle East, Sub- Saharan Africa - I look at it as a worldwide
problem," he said.
Most commercial desalination plants now use either distillation or
reverse osmosis, Klausner said. Distillation involves boiling and
evaporating salt water and then condensing the vapor to produce fresh
water. In reverse osmosis, high pressure pumps force salt water
through fine filters that trap and remove waterborne salts and
minerals.
Boiling the vast amounts of water needed for the distillation process
requires large amounts of energy. Reverse osmosis uses less energy
but has other problems, including mineral buildup clogging the
filters. That’s the main technical issue plaguing the largest
desalination plant in the United States, Tampa Bay Water’s $108
million plant in Apollo Beach. Although it was supposed to produce 25
million gallons of freshwater each day, the plant, beset by technical
and financial problems since opening in 1999, currently is shut down.
Employing a major modification to distillation, Klausner’s technology
relies on a physical process known as mass diffusion, rather than
heat, to evaporate salt water.
In a nutshell, pumps move salt water through a heater and spray it
into the top of a diffusion tower - a column packed with a
polyethylene matrix that creates a large surface area for the water
to flow across as it falls. Other pumps at the bottom of the tower
blow warm, dry air up the column in the opposite direction of the
flowing water. As the trickling salt water meets the warm dry air,
evaporation occurs. Blowers push the now-saturated air into a
condenser, the first stage in a process that forces the moisture to
condense as fresh water.
Klausner said the key feature of his system is that it can tap warmed
water plants have used to cool their machines to heat the salt water
intended for desalination, turning a waste product into a useful one.
He has successfully tested a small experimental prototype in his lab,
producing about 500 gallons of fresh water daily. His calculations
show that a larger version, tapping the waste coolant water from a
typically sized 100-megawatt power plant, has the potential to
produce 1.5 million gallons daily. The cost is projected at $2.50 per
1,000 gallons, compared with $10 per thousand gallons for
conventional distillation and $3 per thousand gallons for reverse
osmosis.
Because the equipment would have to extract as much heat as possible
from the coolant water, it would need to be installed when a plant is
built, he said. Another potential caveat is that a full-scale version
of the mechanism would require a football field-sized plot on land,
likely to be expensive in coastal areas where power plants are
located, Klausner said. Presumably a utility would sell the fresh
water it produces, recouping and then profiting from its investment,
he said.
Klausner said a miniature version of the full-scale system could be
run using solar or other forms of heat, which might be useful for
small towns or villages. UF has applied for a patent on the
technology. Klausner’s research was funded by a $200,000 grant from
the Department of Energy.
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| User: "Rene Tschaggelar" |
|
| Title: Re: New Desalination Technology Taps Waste Heat from Power Plants |
09 Jan 2005 01:38:32 PM |
|
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Multiposted to far too many newsgroups. Reply on s.p only
Contrary to the industrial perception, desalination is less
a matter of the energy source, but that those in need of it
don't have any money at all.
While bigger plants may deliver water at a lower price,
they leave the transportation problem.
Smaller systems operating on solar energy are cheap to
build, but when even 1000$ are beyond the budget of a town ...
When you want them to have water, you have to build the plant,
operate it and deliver the water for free. Or almost.
Rene
Dr. Jai Maharaj wrote:
New Desalination Technology Taps Waste Heat from Power Plants
Forwarded message from Fidyl <fidyl@yahoo.com>
[ Subject: New Desalination Technology Taps Waste Heat from Power Plants
[ From: Fidyl <fidyl@yahoo.com>
[ Date: Sat, 8 Jan 2005
New Desalination Technology Taps Waste Heat from Power Plants
Source: Clean Edge News
December 28, 2004
http://www.cleanedge.com/story.php?nID=3353
University of Florida researchers have developed a desalination
technology that can tap waste heat from electrical power plants as
its main source of energy, an advance that could significantly reduce
the cost of desalination in some parts of the world.
"In the future, we have to go to desalination, because the freshwater
supply at the moment can just barely meet the demands of our growing
population," said James Klausner, a UF professor of mechanical and
aerospace engineering, whose research was funded by the U.S.
Department of Energy. "We think this technology could run off excess
heat from utility plants and produce millions of gallons each day,"
said Klausner, lead author of an article on the system that appears
in the current issue of the Journal of Energy Resources Technology.
He co-invented the technology with fellow UF mechanical engineering
professor Renwei Mei.
.
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