Turn off 4,500 lights or switch on one variable speed drive.... Which would you prefer?

Here we go again. The Independent on Sunday (18th July 2010) has just written a lead news item with the headline: UK's emissions could be cut at the flick of a switch. Why do I know what's coming? Yet another article applauding the concept that switching off the lights will save the planet. Don't get me wrong. Anything that reduces CO2 emissions is a good thing. And when you consider the eye-watering statistics revealed by the article ("...turning electrical appliances off at the mains and installing energy-efficient light bulbs could slash the UK's carbon dioxide emissions by about 40 megatonnes a year*") I am definitely a supporter of the lights-off concept.


But there is just as compelling a CO2 message that really deserves the big national headlines, yet does not seem to be getting through. Take a look at these statistics: a single 110 kW motor without any form of speed control consumes 770,880 kWh per year when running for 8,760 hours**. This is the same as running 6,111 high efficiency light bulbs. However, if you add a simple variable speed control device to the same motor, the energy consumption falls to 376,189 kWh per year, which is the same as running 2,689 energy saving light bulbs.


Therefore adding ONE variable speed drive to ONE electric motor can be the same as switching off 3,422 low voltage light bulbs. How amazing is that!


So why is it that, of the estimated 10 million electric motor population in the UK, only 5 percent have variable speed drives applied? There really is no logical reason.


These are the typical electric motors found, for example, throughout the water industry. It is only during the last five years that the effect of weather patterns has started to filter down as to the likely impact on the water cycle. And already it is affecting the way water is managed. The more that the water cycle is managed, the more energy intensive it becomes. The more that is pumped the more energy is used. The more sewage removed, the more methane is generated.


As such some 4 to 6% of the world's greenhouse gases come from the water industry. A typical water company consumes around 270 GWh a year, 80 percent of its usage (over 215 GWh) is from the pumping of water and sewage. And it is in the speed control of pump motors where variable speed drives can have their biggest impact.


These are figures that urgently need to be addressed through energy efficient pumping. So come on Nationals, give some exposure to the big CO2 savers.



*40 megatonnes of CO2 is equivalent to the annual CO2 produced by 7 million houses in the UK.

**ABB has just created a good old traditional slide rule that offers a rule-of-thumb measure of just what you can save by switching a direct-on-line motor to variable speed control. To order, email energy@gb.abb.com ref. 'slide rule'.

ABB Water Team

Topics: edie
Tags: | CO2 | population | water | weather
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