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Thermal Management for Automobiles

Visteon Automotive Systems, the Environmental Energy Technologies Division, and Berkeley Lab's Engineering Division are collaborating on a research project to create the world's first thermally insulated car. With EETD-developed insulation inside body panels and insulated window units, the thermally insulated car will have better gas mileage than a conventional car and stay cooler in the summer and warmer in the winter.

The aim of this automotive thermal management project is to develop technology that helps reduce a car's total weight by 40%. That's is the ultimate goal of Partnership for a New Generation of Vehicles (PNGV), a federal/private-sector research collaboration that this project is part of. The 40% weight reduction, along with other improvements, will raise the gas mileage of a Taurus to 80 miles per gallon without a loss of performance or decreased occupant comfort.

This is the first time a car manufacturer is studying thermal insulation for passenger comfort. Adding insulation to the car allows its heating, ventilation, and air conditioning system to be smaller, reducing the car's weight and improving mileage. Insulation can also extend the range of electric vehicles by reducing the load on their batteries. The insulation and window film reduce heat gain or loss, smoothing out the temperature peaks and troughs inside the car, keeping it comfortably cooler or warmer, and reducing material degradation caused by ultraviolet light.

Project researchers are collaborating with Visteon. The Thermal Management Project is associated with the United States Council for Automotive Research (USCAR), the research consortium funded by Daimler-Chrysler, Ford, and General Motors to strengthen the domestic auto industry's technology base, as well as the PNGV initiative.

In February, Visteon sent the Berkeley Lab research team a factory-new white Taurus. The car was stripped down to sheet metal within two hours by a technician.

The windshield was modified by applying a spectrally selective solar-control film to the inner surface. The Berkeley Lab team fabricated double-pane insulated glazing units for the side windows. The insulated glazing units have spectrally-selective film on the inner surface of the outer pane and low-emissivity film on the inner surface of the inner pane. The solar control film consists of multilayer thin-film plastics, which create a narrow-band-pass filter that rejects ultra-violet and infrared wavelengths. The result is much less heat gain into the interior of the car and less degradation of interior surfaces. The low-e film suppresses radiative heat loss, helping to maintain comfortable conditions in the passenger compartment in both hot and cold weather.

Gas-Filled Panels

Berkeley Lab's patented gas-filled panel (GFP) insulation has a high performance-to-weight ratio. Adding two to five centimeters of insulation increased the weight of the car door by only 120 grams. The weight savings achieved by GFPs over other insulation options allowed the installation of double-pane windows, which were essential to achieve the overall goal of thermal performance.

Photo illustrating how the customized gas-filled panels fit a car's interior

Researchers designed customized gas-filled panels to fit the car's interior.

GFPs use thin polymer-film cellular baffles and low-conductivity gas filling to create a lightweight device with extraordinary thermal insulation properties. GFPs are essentially hermetic plastic bags that can take on a variety of shapes and sizes. GFPs can be up to three times as effective as conventional foam insulation, depending on the type of gas used.

Low-emissivity coatings for residential windows were pioneered by EETD and window manufacturers in the 1970s and 1980s. Spectrally selective low-e coatings reflect far-infrared radiation (for example, the sun's heat), preventing it from warming an interior space. These energy-efficient coatings are now claiming growing shares of the market for residential and commercial building windows.

Berkeley Lab Engineering Division's Deb Hopkins, Daniel Türler, and Phil Rizzo, EETD's Brent Griffith and Howdy Goudey, and technicians in five of the Lab's shops worked around the clock to retrofit the car by their March deadline. Goudey and Rizzo manufactured GFPs in EETD's infrared-thermography lab, a facility designed for developing and testing insulation and window technology [see sidebar on page 7]. With Türler, they installed the panels in the car body.

In this widely collaborative effort, everyone involved had to help out with the production of GFPs; never before had so many panels of the experimental insulation been assembled. Berkeley Lab's Technical Services Division was instrumental in providing technical support as needed. The Plastics Shop made the contoured interior pane of the dual-pane glazing systems installed on the back and side windows; the Coating Shop manufactured customized plastic parts with aluminum coatings; the Refrigeration Shop drained and tuned the car's air conditioner on short notice; and the Carpentry Shop made shipping crates to deliver the modified doors and parts to Detroit.

Hopkins, Türler, and Goudey went to Detroit in March. There they reinstalled the parts in another Taurus. Another team then tested the thermal characteristics of the refit Taurus in an environmental chamber under hot and cold conditions, as well as under driving conditions.

Berkeley Lab researchers Daniel Türler and Deb Hopkins at work in Detroit

Berkeley Lab researchers Daniel Türler and Deb Hopkins at work in Detroit.

The retrofitted car was also tested in environmentally controlled wind tunnels under driving conditions for hot (55°C) and cold (-18°C) temperatures. The thermal performance of the vehicle exceeded design goals; using advanced insulation and window technologies reduced the vehicle's heating and cooling loads by 80 and 75%, respectively.

With the first phase of Berkeley Lab's work complete, the team plans to use EETD's infrared thermography facility to evaluate the heat flow in the car's interior and refine and improve the design of the insulation.

— Allan Chen

For more information, contact:

  • Deb Hopkins
  • (510) 486-4922; fax (510) 486-4711
  • Daniel Türler
  • (510) 486-5827; fax (510) 486-4711

 

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