Recent Progress in District Heating with Emphasis on Low-Temperature Systems

District heating plays an important role in future sustainable energy system by integrating any available heat source, including waste heat and renewable heat sources such as geothermal or solar heat. The low-temperature district heating system is the latest generation of district heating. It was introduced less than ten years ago in adaption to the need for lower heat demand of energy-efficient buildings. The low-temperature district heating system provides an infrastructure for a higher share of renewable energy sources while reduces heat loss in pipes. Several small-scale projects were commissioned since the introduction of the technology, and many existing district heating systems are in the process of adaptation. The recent progress of low-temperature district heating systems has been discussed here. First, the fundamental knowledge that is required to understand the main advantages of a low-temperature district heating system was explained briefly. Then the most recent and important projects were discussed with emphasis on solar and geothermal district heating systems. The results of case studies show that the low-temperature solution has the lowest capital costs and has a unique position to be the primary source for building heating demand