Economic viability and scalability of a novel domestic hot water substation for 4th generation district heating: A case study of temperature optimization in the Viborg district heating network

District heating (DH) is transitioning towards 4th generation district heating (4GDH), which requires low-temperature operation in the network and building heating system. Large buildings with domestic hot water (DHW) circulation systems are a problem area for low-temperature operations, but the decoupling DHW system using a heat pump is a promising solution. In this study we investigated the techno-economic efficiency of renovating a critical mass of buildings with this solution in a DH network on the scale of a small city. We also propose a new business model in which the DH company owns the substations. The results show that the supply and return temperature s at the level of the network can be reduced by 4.6 °C and 0.43 °C, respectively. This would generate at least EUR 297,000 in production savings annually, which could reduce the heating price for users by 2.7 %. Compared to the traditional user-owned substation business model, the new business model is also more economically competitive. • Apartment buildings with DHW circulation loops are the bottleneck for achieving LTDH. • Renovating a critical mass of buildings achieves considerable network temperature reduction. • An economically competitive business model of company-owned substations is proposed. • A case study shows this method's profitability in both liberalized and non-liberalized markets.