FOR IMMEDIATE RELEASE:                  NIST 94-35
Sept. 13, 1994

Contact:  Jan Kosko                     NEW NIST SOLAR DEVICE
          (301) 975-2767                MAY ONE DAY KEEP
                                        AMERICANS IN HOT WATER

     Researchers at the Commerce Department's National Institute
of Standards and Technology have invented a novel solar water
heating system that is lieved to be the first to use photovoltaic
cells in combination with computer technology to capture the
sun's energy.

     "We think this system is going to be a real competitor for
thermal solar hot water heaters, which have had many problems
over the years, and some day even traditional electric or gas
water heaters," says Hunter Fanney, an engineer in NIST's
Building and Fire Research Laboratory and the system's inventor.

     Photovoltaic cells are semiconductor devices that convert
the energy in sunlight into electrical energy.  The novel NIST
system, which recently received a patent, uses an array of PV
cells on the roof of a house to deliver solar power directly to
multiple heating elements in a hot water tank.

     A computerized controller measures the energy coming in and
controls which element or combination of elements receives the
energy.  "Using multiple heating elements connected to computer
technology enables the system to take maximum advantage of the
varying intensity of solar energy that strikes the cells
throughout the day," says Fanney.

     Solar thermal water heaters were first widely used in
Florida homes starting in the 1920s.  Water is pumped through
pipes up to a rooftop solar collector where it is heated and
returned to the storage tank.  But over the years, these systems
have had numerous problems, including freezing or leaking fluid;
failure of temperature sensors, controllers and pumps; and
significant heat losses through piping.  In addition, pipe
installation often is complicated.

     A big advantage of the NIST system, says Fanney, is that it
directly heats the water in the tank, eliminating the need for
piping and its associated problems.

     "This system offers the potential for a lower-cost means of
supplying a significant portion of the energy consumed for
domestic water heating," says Fanney.  Currently, approximately
90 million residential water heaters are used in the United
States; only a million or so use solar.  According to the
Department of Energy, an electric hot water heater for a typical
household of two adults and two children uses almost as much
energy a year as an automobile driven 12,000 miles averaging 24
miles per gallon.

     In the Washington, D.C., area, Fanney estimates that a solar
water heater with a PV array of about 4 meters by 4 meters could
supply up to 60 percent of the hot water needed for that same
four-member household.

     While the PV water heater has many advantages, it does have
one disadvantage--cost of solar photovoltaics.  According to the
Commerce Department's U.S. Industrial Outlook 1994, the average
cost per peak watt of solar photovoltaics is expected to be
approximately $4 by the end of 1994.   But, that is a far cry
from the early 1980s when the average cost was more than $100.

     With the introduction of new, more efficient PV technologies
and an increased worldwide demand, PV prices are expected to
decline to $1.50 per peak watt within the next decade.  At this
cost, a PV water heater could be installed for approximately
$4,000, about the same cost as a solar thermal water heater.  If
the U.S. Department of Energy's National Photovoltaic Program
reaches its long-term goal of $0.50 per peak watt, a PV solar
water heating system could cost about $1,875 and pay for itself
in reduced energy costs in about six years.  Photovoltaic panels
can last more than 20 years.

     Fanney and his colleague Brian Dougherty, a mechanical
engineer, are building a full-scale PV hot water system at NIST's
laboratories in Gaithersburg, Md.  They expect to have it
operational in January 1995 and will monitor the system's
performance for a year.

     Fanney welcomes inquiries from industries interested in
"partnering" with NIST on this project.  He can be reached by
telephone at (301) 975-5864 or by e-mail at hunter@micf.nist.gov
(via Internet).

     NIST has been involved in solar energy research since the
1970s.  For example, Fanney helped develop a test method to
characterize the performance of solar thermal water heating
systems, which was adopted as an industry standard by the
American Society of Heating, Refrigerating and Air Conditioning
Engineers in 1988.     

     A non-regulatory agency of the Commerce Department's
Technology Administration, NIST promotes U.S. economic growth by
working with industry to develop and apply technology,
measurements and standards.

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(Note to editors:  An illustration of the NIST-developed solar
water heating system is available.)