Denso Corp. will be ready in the event the auto industry adopts carbon dioxide (CO2) as an air-conditioning refrigerant in future vehicles.

The world's top supplier of climate control systems supports CO2 because it is an abundant refrigerant, has a negligible effect on the environment and can be used for heat-pump systems in electric or hybrid vehicles.

But using CO2 in automotive is no simple task. The operating pressure of a CO2 system is 10 times higher than that of a conventional AC system, so it requires a different heat exchanger and re-engineering of every component.

A CO2 system can provide both heating and cooling. In current systems, heat comes from, ironically, the engine coolant. CO2 is becoming necessary because today's engines are so efficient that they do not generate enough waste heat to warm the cabin adequately, Denso says.

Denso acknowledges the topic of CO2 is controversial because certain regions of the world, including parts of the U.S., may have no interest in switching to CO2 as a refrigerant.

At its own SAE press conference, Witzenmann GmbH says it expects to begin European production in 2004 of complex metal hoses for an automotive AC system that runs on CO2.

Witzenmann's end customer likely will be Mercedes-Benz, which has said it will use CO2 as a refrigerant in a vehicle around 2005. It is not clear which supplier will produce the AC system for Mercedes. Denso said it did not have a customer for a CO2 AC system.

Witzenmann would produce only the hoses necessary for carrying the CO2 gas as part of the AC system. The hoses are a crucial part because the gas is heavily pressurized, and the hose must withstand pressures of up to 10,000 lbs./sq.-in. (69,000 kPa).