Driving electrical efficiency

Electricity is expensive – in the long term, often much more expensive than the motors it powers. Steve Brambley urges plant purchasers to look beyond the price tag and ask about efficiency.

Electric Motors electrical efficiency
Electric motors account for about two-thirds of all the electricity consumed by industry.

Picture yourself getting into your car for a short journey to the shops – except with a difference.

Your car doesn’t have an accelerator pedal or any other means of controlling the speed of the engine, so it will just rev away at 7500rpm, making lots of noise and burning fuel at maximum capacity.

You pull away with a screech of tyres and whiplash, accelerating down the road and rapidly approaching the first junction. Your only method of slowing down is to brake, so you push down hard on the brake and clutch and stop your car at the dotted line with the engine merrily spinning at top speed.

You turn the music up to drown out the engine and prepare for another launch.

Sounds ridiculous, doesn’t it? However, this is the way that many industrial electric motors are operated, wasting significant amounts of energy and incurring an unnecessary financial burden for that motor’s lifetime.

The solution is simple – control. Switch it off when not needed, or slow it down to an optimal speed – both are easily achievable with automation technology such as variable speed drives or soft starts.

This article first appeared in the April issue of The Manufacturer magazine. To subscribe, please click here.

Here’s a few reasons why this should matter to you:

  1. Electric motors account for about two-thirds of all the electricity consumed by industry
  2. The energy cost of a typical motor over 10 years is about 30 times the purchase cost
  3. A more efficient motor will gain about 3% efficiency, but controlling the motor can easily net 30% efficiency gains – with 50-70% not unusual.

Staying with the car analogy, your £25k saloon is going to cost you £75k per year in fuel! It’s the equivalent of petrol costing more than £220 per gallon (£50 per litre). If it cost you £15,000 to fill your tank up, you would be very, very interested in buying the most efficient car possible.

Motors are usually purchased as part of a system – for example, pumping fluid, air conditioning and conveyor systems.
Motors are usually purchased as part of a system – for example, pumping fluid, air conditioning and conveyor systems.

I’m going to put a new car on the market, with an automated speed control mechanism, which costs £50k to buy, but consumes only £50k in fuel for the same mileage.

Will you buy it? No way, you say, it costs twice as much as the other car and does the same job.

But hold on, after one year both cars cost the same £100k to buy and run. After three years, the car has saved your £75k and after 10 years that is £250k saved. Now which car will you buy?

So, what’s the problem?

If the savings are so significant, why the relatively low adoption rates of the solution? The answer lies with the approach to purchase cost vs lifetime cost and who pays the energy bill.

Just as you don’t tend to buy car engines separately, motors are usually purchased as part of a system – for example, pumping fluid, air conditioning and conveyor systems. The dominant factor in purchasing decisions is the capital cost of the system and so vendors will compete on purchase price.

If motor control technology will double the cost of the system, then it is difficult to sell against a competitor that leaves that out, even if that system will cost more to run.

GAMBICA is proposing a national standardised method for vendors to quote an annual energy cost for their systems, so purchasers can compare the lifetime cost and not just the up-front capital.

If that were to happen, it would highlight the true cost of ownership, influence purchasing behaviour and save manufacturers both energy and cost.

But you don’t need to wait to change your own purchasing process – insist on asking for the energy cost of any equipment.


Steve Brambley is chief executive of GAMBICA
Steve Brambley. chief executive, GAMBICA.

Steve Brambley is chief executive of GAMBICA –  the national organisation representing the interests of companies in the automation, control, instrumentation and laboratory technology industry in the UK

Find out more by visiting gambica.org.uk