Energy Saving News
The Ups & Downs of Saving Energy
The UK’s Guardian newspaper runs several blogs and this week Dave Hill’s blog had an interesting post after he received an email from a regular reader which is of interest to those involved in energy saving.
The email describes an experience he had on Wednesday evening this week in one of London’s Underground stations:
At Victoria Station tonight at 8.00pm London Underground closed down one of the up escalators from Victoria Line to the main concourse.
They put up a sign saying it was "switched off to save energy".
It goes on to say that this would happen during quieter times of the day as a way of saving energy.
But this happened at 8.00pm on a weekday night when trains were still pretty full, which meant there was a queue of people trying to get up one escalator, forcing others to walk up a non-moving escalator.
The post goes on to conclude that the savings were not worth the inconvenience - using the Transport For London’s own figures for the cost of running an escalator.
Yet the reality is that all the escalators, in all the underground stations across the whole of greater London must use a massive amount of energy.
How can you save energy when the escalators are necessary and in many places irreplaceable, particularly from the deeper London stations.
Many energy saving experts would point towards intelligent smart motor controls as the answer for this problem.
Even in a busy underground station the use of the escalators varies considerably - a train comes in to the station and a whole mass of people will load onto the escalator to rise to the exit, often having to use more than one. A couple of minutes later the escalator is empty, no load but still running at full power.
An escalator is generally driven by a fixed speed ac induction motor. The motor will have been sized to move the escalator in an upward direction with 2 above average weight men on each and every step, and engineers normally actually err on the side of caution and oversize the motor.
The motor has no intelligence and is unaware of how much load (or people) is on the motor. The result is huge amounts of wasted energy.
Some motor controllers can reduce the energy used by recognising how much power is needed and make sure the motor only outputs the correct amount to do the job, delivering only the amount of energy needed for the escalator to operate - if the escalator is full the motor will be at full power but as the load decreases the amount of energy to the motor will be reduced, intelligently by the controller.
No inconvenience, no energy waste and less wear on the motor.
N.B. This is general, non-technical article. Each situation and installation will vary and a full energy and mechanical survey is needed to ascertain the right method of energy saving and motor control in any given situation.
Friday 12th March 2010
