Reducing energy consumption is a bit like exercise. People tend to agree it's a good idea and should do it regularly — but oftentimes they don't quite make it to the gym. Yet if energy costs keep rising, engineers won't be able to sit on the sidelines much longer and will have to work out new ways to trim the energy consumption of the machines they build. This growing energy awareness was on display throughout the recent Hannover Fair, where the major suppliers and users of motors, drives and related automation equipment showed that saving energy doesn't so much require new technology as the smart application of existing technologies.
Bosch Rexroth displayed a diverse collection of drive units optimized for reduced energy consumption. Among them was a pneumatic system whose open-loop electronic controls help optimize speed and air usage for total energy savings that can reach 25 percent. Likewise, the company showed how variable speed pumps can reduce energy consumption by roughly 30 percent compared to constant-speed models. And the company showed electric drive systems whose regenerative capabilities and energy exchange between multiple linked motors contributed to a 35 percent reduction in energy consumption for the 18.5 kW system used in the display. “None of these ideas is new. Some of them have been around for years,” says Wolfgang Walter, an engineer and energy specialist with Bosch Rexroth Drives and Controls.
The increased use of high-efficiency motors also looms large as a relatively untapped source of energy savings. The German Electrical and Electronic Manufacturers' Assn., or ZVEI, estimates the adoption of the most efficient motor class across all possible applications would save 5.5 kWh or 440 million in power costs per year in Germany alone. And Meinhard Schumacher, SEW-EURODRIVE's manager for geared motors and ac drives, says he likes the idea of more higher-efficiency motor use, but he warns they're not a cure-all when it comes to energy reduction. “It doesn't make sense to have a more efficient motor if the other components in the system aren't efficient,” he says, citing inefficient gear boxes as one threat to overall energy efficiency. This system's mentality led SEW-EURODRIVE to come up with its MOVIGEAR, a combination of motor, gear unit and electronics in one housing. Schumacher says its speed-control capabilities and optimized interfaces between all the components can save a significant amount of energy. For example, he says a MOVIGEAR system saves about 300W as compared to a traditional 1.5 kW ac motor and gear box.
At Mercedes-Benz, there's an ongoing effort to save energy by turning off production machines when they're not needed. It's not as simple as it sounds. “You don't just flip a switch. The machine may turn off, but will it turn on again when you need it?” says Gerhard Haeberle, an engineer with the automaker's controls technology group. He and his colleagues have begun an analysis of the company's manufacturing systems to see what things should be turned off and under what circumstances. Haeberle calls the strategy “intelligent shutdown” and says the goal is to implement it — ultimately as PLC function blocks — in the company-wide control standards. The savings promise to be huge. Haeberle didn't have energy consumption figures but he did cite a closely related metric of emissions reduction. “If you look at the life cycle of the car, 20 percent of the CO2 emissions are created during production. Our goal is to reduce that 20 percent by 20 percent through intelligent shutdown by itself,” he says. The emissions and energy savings would be even higher with the adoption of other energy-saving technologies, he says.