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Innovation: Reward Heat project successfully in operation

Demonstration project investigates heating networks with renewable heat sources and the integration of waste heat

Buildings Energy Act implementation

News | March 2024

REWARDHeat research project

Within the European H2020 research project Renewable and Waste Heat Recovery for Competitive District Heating and Cooling Networks (REWARDHeat), innovative solutions for sustainable heating networks with renewable heat sources and the integration of waste heat have been developed for four years and implemented and analyzed in operation in several demonstration projects in Europe.

As part of the research team, enisyst GmbH is responsible for the innovative control and optimization system with predictive control implemented in the demonstration project in Topusko, Croatia. This is a heating network operated with geothermal water, which was converted, renovated and optimized as part of the project. The geothermal water is used to heat and fill pools in the neighboring hotels, spa and leisure facilities. Heat is also supplied via heat exchangers to a heating network, which is responsible for space heating and domestic hot water generation to the buildings in the district.

As part of the project, the heating network was renewed and the central distribution station for the geothermal water and heating network was completely renovated. The heating network is now primarily heated with geothermal water, which is then used to heat and fill the pools. The water is cooled from approx. 65°C to approx. 43°C during heating the pools. To fill the pools, the geothermal water needs to be cooled further to approx. 32°C using a cooling tower. Before the geothermal water is fed into the pools, it is temporarily stored in two large storage tanks at the central station, one with a higher temperature for heating the pools and one with a lower temperature for filling the pools. 

These two storage tanks enable more continuous heat recovery and optimized operation of the cooling tower. In winter, significantly more geothermal water is needed to heat the heating network than is required for the pools. The excess cooled geothermal water is then discharged into the sewage system. However, the optimized control system has made it possible to cool the geothermal water much more efficiently, which significantly reduces consumption.

The conversion and the optimized control system have resulted in considerable savings. For example, around 28% less geothermal water and around 33% less electricity is required on a yearly basis to operate the pumps and cooling tower; this also reduces CO2 emissions by 33%. enisyst is currently optimizing the control of the heat transfer stations in the buildings connected to the heating network, which will contribute to a reduction in network return temperatures and thus to further savings.