Blue Heat built a demonstration project, using sewer water as a primary heat source to heat 92 social apartments. These apartments were built before the first energy crisis. Heating came from one central gas fired boiler room.  The housing company decided to revamp the apartments, insulating where possible, and adding better controls with thermostatic radiator valves.

The boiler room was modernised with new condensing gas fired boilers with a smaller capacity. Furthermore, Blue Heat installed a heat pump system, suitable for most of heating season. As a primary heat source the municipality sewer is used, coming from the nearby hospital.

The water is sieved before being cooled in a special Sigma 22 free flow plate heat exchanger. A heat pump is used to increase the temperature for use as boiler water for the building’s heating system. The system works well most of the time, but has to be switched off during rain showers in winter.

Conclusion

The Blue Hero system can be applied to well insulated buildings, using a heat pump with a COP of approx. 4 to 5, provided that the sewer water as a primary source is disconnected from the rain water system. The sewer heat exchanger needs to be cleaned only twice a year and therefore requires little maintenance cost or effort.

Advantages

The setup is similar to a ground source heat pump, but with a remarkable COP and higher yield. The sieving and extra free flow plate heat exchanger cost around the same as a ground heat capturing network would.