Gore-Tex, best known for outdoor clothing, is now being used for thermal management in base stations used to transmit signals for emerging WiMAX data transmission systems.

Design engineers are using the engineered material to replace heat exchangers and air conditioning units for outdoor stations as OEMs such as Motorola, Nokia and Alcatel-Lucent push for smaller, more energy-efficient and more cost-effective approaches to remove heat from electronic enclosures.

"We've been field trialing it as a systems solution for a year in a collaboration with Gore," comments Mark Shiring, vice president of sales and marketing for ebm-papst, a leading manufacturing of fans and blowing systems. Gore will formally introduce its new Cooling Filter Thermal Management Module incorporating ebm-papst high-performance fans at WiMAX World at Chicago's McCormick Place Sept. 25-27.

"In the wireless base station, it allows use of direct air cooling," says Bob Rodriguez, a spokesman for Gore. "And the value of that is that it has better thermal properties; there is a better thermal transfer using ambient air than with heat exchangers or air conditioners."

Also, the unit is just a filter with a fan, so it is much smaller than a compressor, which may be too big to mount on a telephone pole. Obviously, it also uses much less energy. "We also find that it is a much more reliable solution because there are no moving parts," adds Rodriguez.

Gore-Tex consists of a urethane-coated fluoropolymer membrane that is bonded to a fabric - usually nylon or polyester. Key to the technology is the structure of the membrane, which has about 9 billion pores per square inch (1.4 billion pores per square centimeter). Each pore is 20,000 times smaller than a water droplet. As a result, water and dust cannot penetrate easily. In the base station application, the fan blows hot air through the membrane, while keeping out water. It's expected that the Thermal Management Module will only be used outdoors. Ebm-papst established the specifications on the air flow technology.

Rodriguez said the new Gore Module will cost 75 percent less than base stations cooled with air conditioners and about one third less than models equipped with heat exchangers. The modules use optimized control logic to operate as many as three ebm-papst fans.

The biggest selling point may actually be long-term reliability, since the Gore-Tex modules have no moving parts. Multiple alarms communicate system output.

Unlike WiFi, WiMAX is aimed at transmitting data over very long distances. It's short for Worldwide Interoperability for Microwave Access. One of the goals is to provide an alternative to cable and DSL for last mile broadband access. Another is to allow laptops to connect to the Internet over a wide geographic area. Locations for the base stations that transmit signals are rented from utilities and other sources, triggering a drive to make the stations as small as possible. "We can pretty much go down to any size required by industry right now," says Rodriguez. "We're not the restraining factor now."