Recycling heat from bathwater helps cut bills

HOT water is too important to let it go to waste and so a French company is recycling the heat from waste hot water to cut the energy bills of residents in blocks of flats.

The average family of four in France lets 280 litres of warm water down the drain every day but the Biofluides Environnement collection system captures this ‘grey’ water from washing machines, showers, baths and dishwashers and uses the free heat to warm the incoming supply.

Waste water and clean water never mix and the Seine-et-Marne company’s heat pump transfers heat to the hot water system in a heat exhanger unit in the basement of the flats. The machines keep a constant record of temperatures and energy savings which can be consulted online.

The group is installing 60 such machines in blocks of flats around France and estimates they can cut the costs of a metre cubed of hot water (1,000l) from €9.50 to €4.

The system can only currently work in large recently built blocks that have two water circuits. “It only works at the moment for from 50-60 homes or apartments, but we’re working on a compact model for copropriétés of 10-39,” said company director Alain Mouré.

The group is also looking for further investment to design machines to capture the hot water and air produced by air-conditioning units.

Another project is to create a new version of the heat pump unit that instead of allowing the grey water to flow down the drain once it had heated the incoming cold water, would recirculate it to be used in toilets in the building.

Mr Mouré said 100 homes could spend €9,000 a year just on water to flush toilets – a cost that would be removed by this new model.

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