Within TEMPO, the demonstration project for a new built urban network is in the design phase and several options for the best configuration of a 4-line system have been investigated. The task is to deliver heating, cooling and domestic hot water to row houses and apartment blocks from renewable sources, based on geothermal with HeatPump and Biofuel CHP.

In the project the experiences with LT DH from Sweden, Denmark and the Netherlands are used to design the piping network. In particular the 4th DH is applied by using the know-how of Halmstad University in optimizing the summer supply of domestic hot water, without heating up the return line. Hence a re-circulation line is introduced to keep the temperature of the substations for instant supply of hot water.

With this concept the flow temperatures of 55-65°C and return temperatures of 25°C in the DH net can be realized throughout the year. This 3rd re-circulation line is sized 2 diameters lower than the supply line and has to keep the temperature level of the flow line for instant hot water supply. With a 4th line cooling will be provided directly from geothermal for comfort cooling using the underfloor piping system.

With this concept of a 4 line system all requirements for heating, cooling and domestic hot water can be fulfilled. As the supply temperatures are below 70°C flexible plastic piping will be used with a lifetime of 100 years. Due to the flexibility a high degree of factory made pre-fabrication can be achieved, resulting in up to 75% faster installations.

Within TEMPO this configuration is tested and monitored in the coming years to get a clear view on the saving potentials of such solution compared to standard DH networks.