Heating a public pool: two textbook cases of how to combine sustainability and efficiency

16 Feb 2017

Heating a public swimming pool is a huge expense… in both financial and energy terms. But times are changing, and a host of innovative projects are springing up. 2016 saw two major innovations regarding this very issue of finding more economical and environmentally-friendly ways to heat the water in public pools. Both projects are “Made in France”, and we are going to tell you about them today.

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Butte-aux-Cailles' swimming pool heated by Stimergy © Stimergy

Heating a pool while surfing the internet

Data centres are facilities where computer servers are grouped together. And these servers collect up all the data generated every day by thousands of web users on thousands of websites. The trouble is, these data centres are very energy-intensive: they operate round the clock and have to be kept cool – because they get hot! So to prevent the equipment from overheating, it has to be housed in large, air-conditioned server rooms.

As an alternative to simply carrying on cooling data centres down, a start-up called Stimergy based in SE France decided to recover the heat they produce, with a view to supplying it to buildings. The concept has already been adopted to heat hot water at the University of Lyon Jean-Moulin, and is due to be deployed in early 2017 to heat the water at La Butte-aux-Cailles swimming pool in Paris.

In the latter case, Stimergy servers are being installed in the facility’s basement (with plenty of protection!) and a digital boiler will recover the heat produced by the servers, recycle it, and use it to heat pool water.

On the environment front, this approach greatly reduces energy consumption. It dispenses with the need to cool the servers, and less electricity is required to heat the pool water. And this dual energy saving also generates considerable financial savings.

Harnessing energy from… the sewers of Paris

After recovering heat from data centres, let’s move on to a subject that’s a bit less appetising but just as efficient: recovering energy from sewers. That’s right – sewers. But how?

In this case, the heat takes the form of low-temperature thermal energy. Sewers do not produce heat, but they are warm. At least, the water flowing through them has a temperature of between 13° and 20°C. With a view to harnessing this energy, heat collector systems (metal plates) were thus fitted in the sewers beneath Aspirant Dunand swimming pool in Paris. But don’t worry: it’s not the water that’s recovered; it’s the heat it conveys! The additional heat required by the pool is then provided by a pumping system. This system has been in use since 5 October 2016 to help heat the water in the pools and showers to 26° and 35°C respectively.

Here too, the impact is two-fold: in financial terms, less electricity is required to heat the pool water (a considerable saving for the local authority’s budget!), and in environmental terms, this system reduces the greenhouse gas emissions produced by the facility.

Of all public amenities, swimming pools are the most energy-intensive (to heat the water and air and to ventilate the premises). All this comes at a cost, both for local authorities’ budgets and for the environment. Energy efficiency is increasingly becoming a key issue in pool refurbishment and construction projects. Thankfully, France seems to be on the right track! 

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