Blackburn with Darwen Borough Council

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Blackburn with Darwen Borough Council is the largest employer in the Blackburn area, and has a commitment to reduce carbon emissions by 25% by 2013, in line with government targets. Meeting these targets will not simply encompass the usual good housekeeping measures; in fact, significant savings can come from far less obvious initiatives. Lee Kinder, Property Manager at the council, reveals to the Low Carbon Innovation Network how an unusual project is making considerable savings.

“One area where we really needed to make an energy saving was the local swimming pool,” said Lee Kinder. “Evaporation of the water accounts for the majority of pool heat loss, where it is important to cover the pool when not in use. However, the Waves Centre is an unusual lagoon shape, and a conventional cover would not fit. Pools need to be heated overnight to maintain temperature for the next day, but without a cover, this costs a huge amount of energy and carbon.”

The solution came in the form of ‘liquid pool cover technology’, a product developed by HeatSavr, and used by Butlins. The product is, in effect, a liquid blanket which acts like a conventional blanket and, by increasing the surface tension of the swimming pool water, significantly reduces evaporation. Since evaporation can account for anything between 70% and 90% of pool water heat loss the technology substantially reduces heating costs.

The liquid pool cover is constituted by a mixture of ingredients which are lighter than water, allowing it to float to the surface. The technology incorporates a spreading mechanism which forms a monomolecular layer by making use of the repulsive forces generated by dissociation of ionic compounds when dissolved in water. Negative ions repel each other, as do positive ions, and quickly spread the film forming agents, creating a very thin insulating layer over the whole pool surface, regardless of the pool shape. The thin cover breaks apart whenever the water is disturbed, but when the water becomes calm the liquid particles regroup to reform the protective layer, adjusting to changing activity levels in the pool throughout the day.

In addition to savings on water heating, the technology also reduces the overall energy usage which includes dehumidification and air heating. Reduced evaporation means less load on any dehumidification plant, and when the pool is unoccupied the air temperature can be reduced to a set back level, resulting in reduced air heating costs.

Installing the technology at the Waves Centre was straightforward. The pump and controller cost £350, whilst installing a dosing line took the total installation cost to £550. The chemical itself costs around £2,000 a year, 30ml of which pumped into the filtration system at the end of each day and fed into the pool tank. This produces an immediate saving within the first year of use, compared with the gas bill when the pool was not covered at all. (HeatSavr expect a 500% return on investment, e.g. if you spend £100 on this technology, you save £500 of what you’d otherwise have paid in energy costs.)

“We also took the opportunity to replace the boilers with highly energy efficient models, so we are seeing a large gas saving,” added Lee. “To maintain daytime heat, pool water has to stay at a constant 30 degrees throughout the night. To illustrate how effective this was, the boilers never had to operate during the night, which means the liquid pool cover effectively retained enough heat to eliminate the need for energy usage during the night.”

Other councils are already looking into this technology, following the success at Blackburn and Darwen. Lee Kinder highlights how important the research stage was for the project. “We got detailed references from others using the technology. But for me, the biggest challenge was making sure we were not using any chemical that was going to be hazardous in anyway.” Accordingly, the liquid pool cover is non-toxic and biodegradable, gradually filtering out of the pool, and has been fully tested by numerous independent authorities to ensure that it meets the required health and safety standards.

“For unconventionally shaped pools, this is the only way to save heat lost overnight,” concludes Lee. It’s a nice example of how carbon saving isn’t all about utilitarian cut backs on luxuries like interesting shaped pools, but an opportunity for technological innovation, and is certainly a significant step towards the council’s target of a 25% reduction in carbon emissions by 2013.


Lee Kinder will be facilitating a discussion session at the Low Carbon Best Practice Exchange on 20th November at the Manchester Central Conference Centre. To learn more about the Best Practice Exchange, or to secure a place for the day, please contact Martyn James or Ellie Hooper on 01883 344 799.