Thursday, 28 January 2016

John Guthrie, Energy Efficiency Manager, ABB writesA 25 m pool can hold as much as a million litres of water, and all this water has to be constantly circulated and heated to ensure that it’s clean and safe, as well as fun to splash around in. The air above it has to be constantly regulated too for temperature and humidity - switch off those systems for just an hour and you’ll very soon notice the difference.

These systems rely heavily on pumps and fans; applications in which variable-speed drives (VSD) are perfectly suited to help to achieve enormous energy and cost savings. With just a 10 percent improvement in the management of energy usage it’s estimated that UK leisure facilities could save up to £70 million each year, and with VSDs eliminating energy waste by up to 50 percent the savings could actually be much higher.

How variable-speed drives can help
VSDs are particularly well suited to swimming pools due to the fact that their circulation systems don’t have to be run at full power all the time, so if the pool is quiet or empty the systems can run at a reduced output. Most systems do this by throttling, so the motor is still running at full speed, but the flow is regulated by dampers or valves. This can result in vast amounts of energy wastage, but surely there’s a more efficient way?

With a VSD, the motor uses only the energy that is required, eliminating wastage by potentially huge amounts – a motor running at 80 percent speed consumes just 50 percent of the energy that it would at full power. The system can be programmed to run at or close to full speed during peak periods, and still maintain the required flow low flow when the pool is unoccupied.

But we can be even smarter still. By equipping the systems with PID controlled feedback loops the whole system can be automated. This enables the drive to react to how many people there are in the pool as well as to seasonal changes and other variables, adjusted accordingly to achieve optimum energy efficiency at any output demand.

LCC swimming pool motors will never work alone after VSD retrofit
Liverpool City Council is one example of just what savings are possible. It recently approached Central Group, an ABB authorised value provider (AVP), to find out how much energy VSDs could save in five of its swimming pools. Central Group estimated 10 to 15 percent. At first the council was sceptical, so a trial was agreed at one pool to prove that it would work.

The actual figure turned out to be 35 percent, prompting the council to retrofit 20 ABB variable-speed drives into four of its other swimming pools ranging from 7.5 to 18 kW. The project is now saving the council £60,000 a year, with a payback of around two years.

So that’s just one example of the difference variable-speed drives can make. Contact an AVP to find out how much energy VSDs can help you save.

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