ＥＥＥ会議（太陽光による脱塩システムを開発：フロリダ大学）..........................................2003.9.24


米国フロリダ州の大学の技術者グループが、太陽光を使った脱塩システムを
開発したというニューズです。飲料水に悩む多くの国々にとっては朗報でしょう。　
詳細は、国務省の最新情報（在日米大使館提供）でどうぞ。　ところで、原子力
で脱塩装置を、というアイディアは最近どうなったのでしょうか？
--KK
***********************************************

Subject:   U.S. Engineers Develop Desalination System Powered with
              Solar Energy

　　　　　　(Could provide solution to growing need for fresh water)

Engineers at the University of Florida have developed a system that uses
solar energy instead of electricity or fossil fuels to desalinate water --
a solution that could help meet the growing need for fresh water in many
parts of the world.

According to a September 16 press release, the new system is significantly
more efficient than previous solar "stills" for removing salt, yet is
simple and inexpensive enough to be built in remote locations where
conventionally powered technologies would be either too expensive or
impractical.

A paper about the system by Yogi Goswami, director of the University of
Florida's Solar Energy and Energy Conversion Laboratory, recently appeared
in the Proceedings of the 2003 International Solar Energy Conference.

The new system consists of a U-shaped pipe where a vacuum is created. The
pipe is surrounded by an evaporator that circulates water heated in a
solar collector. The heat forces the salt water to begin evaporating -- a
process facilitated by the vacuum -- and the resulting steam then enters a
condenser. The fresh water drips from the condenser down the pipe into a
tank.

Tests on a small, experimental version of the system revealed it is 90
percent efficient, which means 90 percent of the solar energy piped into
the evaporator was used in the desalination. Goswami said that although
the system produced only about a half cup of fresh water an hour, it can
be scaled up to provide more.

The World Water Development Report, released last March by the United
Nations, says many countries in the Middle East, Africa and Asia currently
face severe water crises, and the number is likely to grow in coming years
under the dual pressures of increasing populations and worsening
pollution.

Seawater desalination has long been seen as an attractive solution for
thirsty regions eager to tap the world's oceans, which contain 97.5
percent of the Earth's water. Current desalination systems are heavy
energy users, however, which make them impractical for poor countries
facing water shortages.

Following is the text of the press release:

(begin text)

University of Florida
September 16, 2003

HERE COMES THE SUN: ENGINEERS DEVELOP SOLAR DESALINATION SYSTEM

GAINESVILLE, Fla. - A solution to the growing need for fresh water in many
parts of the world may come from a natural source: the sun.

Engineers at the University of Florida have developed a system that uses a
gravity-induced vacuum and solar energy instead of electricity or fossil
fuels to desalinate water. The system is significantly more efficient than
previous solar "stills" for removing salt, yet is simple and inexpensive
enough to be built in remote locations where conventionally powered
technologies would be either too expensive or impractical.

"We know that nature uses solar energy to get fresh water from salt
water," said Yogi Goswami, a professor of mechanical engineering and
director of UF's Solar Energy and Energy Conversion Laboratory. "We use
the same process as nature, except we enhance the process."

A paper about the system by Goswami and a May UF doctoral graduate in
mechanical engineering recently appeared in the Proceedings of the 2003
International Solar Energy Conference.

A lack of potable water is a growing problem worldwide, according to a
United Nations report released in March. The World Water Development
Report says many countries in the Middle East, Africa and Asia currently
face severe water crises, and the number is likely to grow in coming years
as increasing populations and worsening pollution chip away at fresh-water
supplies. In less than half a century, 7 billion people in 60 countries
could face water scarcity, the report says.

Seawater desalination has long been seen as an attractive solution since
the world's oceans, which contain 97.5 percent of the Earth's water, are
inexhaustible. But current desalination systems are heavy energy users,
which makes them impractical for poor countries facing water shortages,
Goswami said.

Nature has its own process for desalination. Fresh water evaporates from
the ocean, forms clouds, condenses and falls to the ground as rain.
Goswami sought to recreate and enhance this process by exploiting solar
energy and natural barometric pressure.

The guts of their system consist of a U-shaped pipe placed upside down,
with one end of the pipe suspended in a tank of salt water and one in
fresh water. When the 32-foot-high pipe is filled with water, some of it
drops into the tanks, leaving behind a vacuum.

The area of the pipe where the vacuum occurs is surrounded by an
evaporator that circulates water heated in a solar collector. The heat
forces the salt water to begin evaporating - a process facilitated by the
vacuum because it significantly lowers the boiling or evaporating
temperature of the water. The resulting steam then enters a condenser. The
fresh water drips from the condenser down the pipe into the tank.

Tests on a small, experimental version of the system revealed it is 90
percent efficient, which means 90 percent of the solar energy piped into
the evaporator was used in the desalination. Previous "flat basin" solar
stills were only 50 percent efficient, according to Goswami. Although the
system produced only about a half cup of fresh water an hour, it can be
scaled up to provide more, Goswami said.

The system, which consists of off-the-shelf pipes and other readily
available parts, offers a potentially low-cost solution to desalinating
seawater in remote or inaccessible areas, said E. Delyannis, a scientist
and solar desalination expert at the National Center for Scientific
Research's Solar & Other Energy Research Laboratory in Athens, Greece.

"Dr. Goswami's system is promising (as) a new method that will improve
solar distillation efficiency," Delyannis said. "But you have to keep in
mind that all these systems are not compatible to conventional
desalination plants of large capacity. They can be applied in small
communities lacking fresh or good-quality water or to remote places to
provide the people living there with small quantities of water."

(end text)

(Distributed by the Bureau of International Information Programs, U.S.
Department of State. Web site: http://usinfo.state.gov)
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