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TORONTO, Ontario, CA, November 15, 2006
(Refocus Weekly)
Adding solar thermal collectors to solar PV
modules will increase system efficiency by 300%, according to a
Canadian manufacturer.
The National Solar Test Facility monitored SolarWall ‘PV/T 700E’
panels for several days, using PV modules from BP Solar, Evergreen
and UniSolar. The modules were mounted on a 10 m2 SolarWall
collector panel, to capture heat from the PV panels into the solar
thermal air heating from the SolarWall perforated sheets.
The tests were conducted with Task 35 of the International Energy
Agency, and the results show the output of the combined system was
three times more than the electrical energy generated from the PV
modules, the company claims. Adding the solar thermal component
boosted total solar efficiency to 50%, compared with 10% to 15%
efficiency for most PV modules alone, it claims.
Recovering heat from the PV panels would minimize the build-up of
heat that can raise temperatures on roofs to 85°C, and would reduce
the system financial payback time by two-thirds.
“This is a landmark finding considering the growing prevalence of
PV,” says Conserval Engineering, which manufactures the SolarWall
transpired collector. The solar air heating system involves metal
cladding installed on the south-facing wall of a building, to
pre-heat air that is pulled into the building by interior
ventilation fans that create a negative pressure in the cavity
between the cladding and the wall.
“PV companies have been throwing away valuable heat energy,” says
John Hollick of Conserval, who invented the solar thermal collector.
“By collecting the hot air, the PV panel runs cooler and a solar
cogeneration system occurs. The heated air can be used for space
heating or water heating, and offers a simple solution to the hot
roof problem plaguing many building integrated PV installations.”
SolarWall also reduces building heat loss during winter, by
capturing warm air on the southern wall and returning it to the
building with the heated fresh air from the collectors. The company
says it has installed 1,000 projects in 25 countries, and claims
operating efficiency of 75%.
In sunny conditions, a SolarWall can raise air temperature by 40°C
depending on flow rate, and the cost of collectors in new
construction is less than the cost of a brick or metal-clad wall. A
typical SolarWall installation produces 500 to 700 kWh/m2, with
energy savings of C$10 to $60/m2 of wall, with an estimated payback
period of three years in new construction and eight years in
retrofit.
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