Swimming pool De Blinkerd heated with sewage water
- Worldwide involvement
- January 2, 2025
- 5 min read
Since September 2024, swimming pool and sports centre De Blinkerd in The Hague has been heated with heat extracted from the local sewer. It sounds a bit strange and perhaps a bit unhygienic, but it is actually very clean and sustainable. It even saves no less than 170.000 m³ of gas per year! How? We will explain it to you!
Wesley Verschoof, manager of Sportcentrum De Blinkerd, and Patrick Wagemans, project leader on behalf of the municipality of The Hague, are both responsible for this project. Years ago, they already considered this option for energy transition, but at the time it did not seem worth the investment. However, when gas prices started to rise, the idea was reconsidered. An external agency made calculations and everyone realized that saving 170.000 m³ of gas per year was more than worth the investment. Not so strange, because 170.000 m³ of gas is equal to the gas consumption of 170 households! Now that is a sustainable solution.
Work in progress at De Blinkerd
In addition, the techniques of heat pumps and the possibilities to store heat in the ground have improved considerably in recent years. Last but certainly not least, this project also fits in seamlessly with the mission of the municipality of The Hague to take major steps in the energy transition.
'Within the municipality there are various initiatives for energy transition. However, De Blinkerd is the first swimming pool in the city that has moved away from natural gas. Worldwide there are only a few swimming pools that are heated with this type of heat source. The technology is fairly new and cannot be applied everywhere. The building and the location are of great importance in this. We are fortunate that there is a large sewage pumping station for waste water and a large field next to it just 50 meters away.' - Patrick Wagemans, project leader for the energy transition of De Blinkerd
How does it work technically?
Great, heating a swimming pool with sewage water, but how does this work exactly? De Blinkerd uses thermal energy from sewage water, also known as sewage heat. In other (and simpler) words: the heat that the sewage water gives off is stored and used as a heat source for heating the swimming pool.
Sewage water has a temperature of approximately 18°C in summer and 12°C in winter, which is a stable and reliable source of heat. A submersible pump is placed in the buffer reservoir of the sewage pumping station, which pumps up the dirty but warm water and pushes it through a 100-metre long underground pipe to the sports facility and back again. Two other pipes are wound around this 'dirty water pipe': one with coolant (glycol) and the other with clean water that is heated during the flow. These two pipes then enter the sports facility, while the dirty water flows back to the buffer reservoir.
Sewage water has a temperature of approximately 18°C in summer and 12°C in winter, which is a stable and reliable source of heat. A submersible pump is placed in the buffer reservoir of the sewage pumping station, which pumps up the dirty but warm water and pushes it through a 100-metre long underground pipe to the sports facility and back again. Two other pipes are wound around this 'dirty water pipe': one with coolant (glycol) and the other with clean water that is heated during the flow. These two pipes then enter the sports facility, while the dirty water flows back to the buffer reservoir.
Heat storage in the ground
Heat storage in the ground was introduced at a later stage. In the summer, the sewer provides higher temperatures, while extra heat is needed in the winter. To prevent heat loss, the heat is stored in the ground at a depth of 200 metres. Two wells are drilled: one to store heat in the summer and recover it in the winter, and the other to return cooled water to the ground. This system is called Aquifer Thermal Energy Storage (ATES) and is already used to heat and cool the city hall of The Hague.
Sustainability measures in the past
De Blinkerd has already implemented various sustainable measures. All lighting has been replaced by LED lighting and the windows are fitted with HR++ glass. Wesley gives another example: 'For ventilation, we have equipment that recovers heat from the air that is blown outside. This allows us to heat up the cold outside air. In addition, we cover the swimming pools with blankets when they are closed. The less heat loss, the less energy is needed.'
- 170.000 m³ of gas is equal to the gas consumption of 170 households.
- The municipality wants to make all swimming pools in the city more sustainable.
- The sewer management is carried out by the Delfland Water Board. This project is also a new experiment for them that they will carefully evaluate.
'However, De Blinkerd is the first swimming pool in the city to switch from natural gas.'
Patrick Wagemans