|Automobile interiors can become unbearably hot. Car
makers in Detroit traditionally have solved the cooling problem with the use of large,
heavy, and inefficient air conditioners, typically of the same size that would be used to
cool a small house. Now, researchers are exploring an alternative approach, one that
could save more than a billion gallons of gasoline per year.
Using energy-efficient technologies developed for buildings, they have created the world's first thermally insulated car. Engineers recently completed an evaluation of the experimental vehicle. Tests show that the car's heating and cooling loads were reduced by 80 and 75 percent, respectively.
Insulating a vehicle allows the downsizing of heating and cooling systems. This downsizing translates into lighter, more energy-efficient transportation and much more comfortable vehicles.
"This is the first time that a car manufacturer is studying thermal insulation to
reduce heating and cooling loads," says Deb Hopkins of Berkeley Lab's Engineering
BENEFITS OF THERMAL INSULATION
The Thermal Management Project teams the Lab's Engineering and Environmental Energy Technologies divisions with Visteon Automotive Systems and the U.S. Government's Partnership for a Next Generation of Vehicles (PNGV). Hopkins collaborators here at the Lab include Daniel Turler, Howdy Goudey, and Brent Griffith.
Several months ago, researchers here in Berkeley retrofitted a conventional passenger automobile (1998 Ford Taurus) with advanced lightweight insulation and window technologies. Berkeley Lab's patented gas-filled panel (GFP) insulation is a winning technology for transportation applications because of the panel's high performance-to-weight ratio.
GFPs use thin polymer-film cellular baffles and low-conductivity gas to create a lightweight device with extraordinary thermal insulation properties. These hermetic plastic bags can take on a variety of shapes and sizes and can be up to three times as effective as conventional foam insulation. The weight savings achieved by GFPs over other insulation options made it possible to retrofit the test vehicle with double pane windows.
The Berkeley Lab team fabricated double-pane insulated glazing units for the side and back windows. Then, a spectrally-selective film that rejects ultraviolet and infrared wavelengths was applied to the inner surface of the outer pane and to the inner surface of the front windshield. Additionally, a low-emissivity (Low-E) film was applied to the inner surface of the inner pane of the side and back windows. The Low-E film suppresses radiative heat loss, helping to maintain comfortable conditions in the passenger compartment in both hot and cold weather.
To measure the degree of success of the project, the experimental vehicle was tested under driving conditions for both hot (55° C) and cold (-18° C) temperatures in a wind tunnel testing facility in Canada.
Tests showed that the thermal performance of the vehicle exceeded design goals. Using advanced insulation and window technologies, the vehicle's heating and cooling loads were reduced by 80 and 75 percent, respectively.
Hopkins says advanced insulation and window technologies provide a cascade of benefits. They include: