In order to maintain the competitiveness and improve the environmental performance of district heating in the future it may be of essence to transition to lower operating temperatures over those of the current third generation district heating systems. This is due to the fact that heat demands are expected to decrease as buildings become more energy efficient as well as new types of heat sources are likely to be integrated. The third generation district heating systems operate at annual average temperatures of 75-90°C supply and 40-50°C return in Sweden today. However, these temperatures are well above the customer temperature demands which are to heat buildings to approximately 20°C and provide domestic hot water at 50°C. Therefore, future supply and return temperatures of 50-55/20-30°C for the next fourth generation district heating systems have been suggested.
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