Wastewater heats social houses

The demonstration project in Leuven is part of work package 2 of the INNERS project and demonstrates a sewage heat recovery system in a residential context. Sewage heat is used for the heating of 93 apartments, using a heat exchanger and a heat pump. Inside the heat exchanger the heat of warm sewage water is withdrawn and given to the heating water. In between is a heat pump concentrating the heat and delivering it to the heating water. This means 10l wastewater loses 1 °C and 1l heating water is heated 10°C. For every 4,5 kWh added to the heating water, the heat pump consumes 1 kWh electricity (COP=4,5). When 2,5 kWh heat is produced with a standard gas boiler, the CO2 emissions correspond to the ones for the production and distribution of 1 kWh electricity. For the same amount of CO2 emissions we have almost twice as much heat. That is why these systems have a positive effect on the CO2 emissions.
In this demonstration project we aim to maximize the CO2 reductions and match the available sewage heat with the residential heat demand in a renovated apartment of 1980.

Vlario technicalIn the Monseigneur Van Waeyenberghlaan, Leuven (BE) an apartment was found meeting the above mentioned selection criteria. The public sewer in the street collects the wastewater of the city hospital, discharging  1000-1500 m³ waste water pro day with temperatures never below 15°C. The city hospital itself wasn’t interested in heat recovery because they couldn’t find an application for low temperature heat as the temperature of the heating water is > 60°C and the use of hot water is negligible relative to the disposed volume.
The apartment is owned by a social housing department (Dijledal), consists of 93 units and is heated with a central heating system.