A product's efficiency is only part of the equation. Intelligent control can make much larger efficiency gains by switching off or turning down the load, says Steve Brambley of Gambica.
In motor-driven systems, a small decrease in speed can yield a large reduction in energy consumption.
Used for power pumps, fans, compressors, conveyors, hoists and many other loads, electric motors consume 66% of industrial energy.
In 2011, the Ecodesign directive introduced a mandatory minimum requirement, increasing the minimum efficiency standard for certain electric motors from IE1 to IE2, with further increases to IE3 coming in 2015. This is a necessary step to ensure that only energy-efficient products are placed on the market.
By choosing a a premium-efficiency IE3 motor over an IE2 motor, you will benefit from approximately one to three per cent reduction in energy consumed.
That saving is achieved while the motor is on, but what if you could turn it off for 20% of the time. That’s a 20% energy saving by just automating an off switch, a much bigger gain than the new motor alone.
What if you could reduce the speed of the motor by 20%? For fans and pumps, that a huge 50% saving in energy.
Now we start to see why system efficiency can give you big gains. Many motor systems suffer from inefficiency due to ‘specification creep’ and lack of automated control.
Engineers are generally risk-averse and build in lots of flexibility into their designs. The final motor specification for an application usually starts by coping with the highest imaginable load, adds some safety margin just in case and then selects the next motor size up.
The end result is a system that often operates at a fraction of the design specification and consumes far more energy than it needs to.
Using control and automation, motor systems can be continuously monitored and automatically controlled to meet the real output requirements. Switching off when not needed and turned down to optimum speed, the system efficiency can often be improved by double-digit percentages.
Combined with high-efficiency products, this approach can save such a significant amount of energy that the payback on any investment required is often measured in months rather than years.