A medium-sized industrial company with an electricity spend of £50,000 ($78,000) could save £5,000 per year by fitting variable speed drives and higher efficiency motors, the Carbon Trust has said, as it publishes a pair of new technology guides.
In its Motors and Drive Technology Overview, the trust says that a running motor’s energy use in one year can cost up to ten times its purchase cost. Typical running costs for a fully loaded motor range from £1,770 a year for a 2.2kW motor to £25,970 a year for a 37kW motor, the guide says, assuming an electricity price of £0.08/kWh.
The Carbon Trust says that because motors are so widespread, and often hidden within machinery, they tend to be left running even when they are not needed. It recommends that companies identify equipment that can be switched off, and consider the risks of doing so: for example, what is the potential for the operator to switch off the wrong motor, or switch off at the wrong time? Does flipping the switch pose health and safety risks?
Enterprises should consider automatic switch-off using timers, interlocks or load-sensing devices. If using manual switch-offs, companies should consider writing a switch-off procedure, and placing it where operators can easily see it.
The Carbon Trust has also published its Variable Speed Drives Technology Guide, showing various ways that VSDs can be used to reduce energy use in a range of motor applications.
According to the guide, about half of all motor applications have some kind of varying demand. This includes fans, pumps, winding reels and precision tools.
VSDs, also known as drives, frequency converters, adjustable speed drives or inverters, are electronic power controllers that can adjust the electrical supply to an AC induction motor, changing the motor’s speed and torque output. Using a VSD to slow down a fan or pump motor from 100 percent to 80 percent can cut energy use by as much as 50 percent, the trust says.