Sewer thermal energy

Sewage is a promising energy source thanks to sewer thermal energy technology. After all, the water in a sewer is far more than a waste product. It still contains plenty of residual heat from washing machines and showers, for example. And this makes an excellent basis for heating buildings.

With sewer thermal energy, a heat exchanger is installed in the sewer system. The hot or cold waste water flow, from showers, washing machines, dishwashers, etc. is used to bring a conductor liquid to the desired temperature. The heat conductor liquid then enters a heat pump in a building, to supply the necessary heat or cooling.

New or existing sewers have to fulfil a number of requirements in order to be able to apply sewer thermal energy: the diameter of the waste water pipe must be large enough. We opt for a waste water pipe with a minimum diameter of 800 mm and a minimum flow rate of 15 l/s. In a collector sewer transporting the waste water of at least 7,000 residents, we can recover up to 75% of the heat. The distance between the collector sewer and the housing units is also important: this can be up to 900 metres.

Aquafin and sewer thermal energy

Sewer thermal energy is still a relatively unknown piece of the renewable energy jigsaw. The technology is mainly used where traditional geothermal energy is out of the question. It’s also often a considerably less expensive alternative than geothermal energy, for which multiple drillings are required. Sewer thermal energy is also very reliable in operation. Waste water is always there and it is an easily exploitable source of green energy.

As sewer specialists, at Aquafin, we know exactly when sewer thermal energy is a promising option. We manage more than 300 waste water treatment plants and almost 7,000 km of sewers throughout Flanders.

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