Transformation Roadmap from High to Low Temperature District Heating Systems

The condensed Transformation Roadmap can be expressed as: 1. Eliminate temperature errors in existing distribution networks and substations in order to make existing systems more efficient. This will reduce existing temperature levels. 2. Avoid these temperature errors in new network parts and in new substations. 3. Use heat exchangers with longer thermal lengths in substations for indirect connection of customer heating systems and closed hot water preparation. This will reduce the temperature differences between the warmer distribution waters and the colder fluids to be heated. 4. Reduce existing customer temperature demands by elimination of local temperature errors, reduction of heat demands by means of energy efficiency measures, and by installation of larger heating surfaces in radiator and ventilation systems. 5. New low temperature network parts in conjunction with existing systems can be connected by concurrent operation of these parts as secondary networks. 6. The long-term vision is to deliver heat to substations with a supply temperature of 50°C, while obtaining a return temperature of 20°C as annual average. However, the technical solutions for obtaining this low return temperature have yet not been defined.