An air-conditioned cabin is the best way to drop a car’s fuel efficiency on a hot day. This is true of electric vehicles (EV) as much as it is for gas-guzzlers. Researchers in Singapore, who know something about hot-weather driving, say they’ve found a way to help an EV to run up to 20 percent longer between recharges during air-conditioning use.
Their idea: a “2-in-1 electric motor” that consolidates the air-conditioning compressor into the same housing as the main traction motor powering the vehicle’s wheels. This creates efficiencies and frees up additional space for auxiliary batteries to power other electrical accessories, thereby reducing the load on the main battery. Automobile A-C systems can drain up to half of a vehicle’s battery charge, according to researchers at Nanyang Technological University in Singapore.
Components common to the compressor and traction motor could be shared, eliminating duplicate parts such as mounting brackets, casing, inverter housing, seals, cooling mechanism and electromagnetic shielding. Building the refrigerant compressor into a vehicle’s main power plant would also enable the compressor to tap at least some portion of the energy produced by a vehicle’s regenerative braking system.
The integrated motor took about two years to design, and Nanyang plans to build a proof-of-concept prototype within the next six months, says lead developer Satheesh Kumar, a research scholar at the university’s Energy Research Institute. Once the prototype is tested in the lab and tweaked, the German Aerospace Center—that country’s aerospace agency—plans to prepare the motor for commercialization, creating a ruggedized version that can withstand the heat, vibration and other extreme conditions it will encounter under the hood while speeding down the highway.
And despite sharing the same housing, the two motors operate independently—while the vehicle is stopped the compressor can run at full capacity, for example. “Our invention is not coupled with the main drive motor in any manner during normal drive mode,” Kumar adds. “The main drive connects with the compressor only during regenerative braking mode.”
The idea of a two-in-one motor bucks a trend both in the automotive and aviation industries to decouple subsystems from the main engine, says Angelo Patti, a mechanical engineer in Ford’s Climate Control Systems Engineering department and chairman of SAE International's Interior Climate Control Committee. (Patti was not involved in Nanyang’s research and commented on the motor as a technical expert, not on behalf of Ford or SAE.) Such separation enables different computer-controlled motors to operate independently and, as a result, more efficiently. Still, when it comes to electric vehicles, extra battery capacity is a big advantage, he adds.