Challenges on low heat density district heating network design

While district heating is an energy efficient solution to provide heating to areas with high heat consumption, mature systems extending out to more demanding operational environment face challenges maintaining competitiveness over alternative heating systems. As the heat density falls below a certain level, district heating is no longer economically feasible. Studying the possibilities of extending this threshold by means of district heating system design and pointing out the operational challenges while approaching it are the main topic of this paper. The problem is investigated in a representative case of a low heat density area bordering a more extensive district heating network. A node-and-branch type network simulation model is used study the operation of the network and a simulation period of one year is used to get a realistic view of the system in a normal operational cycle. Not taking into account the characteristics of a low heat density area in network design can result in inefficient distribution system. Operational problems, especially maintaining the temperature level in summertime, must be solved. Only concentrating on minimizing the heat losses will not result in best possible design. The temperature level issue can be solved with a bypass valve, auxiliary heating or accumulators, but in overall more efficient system requires steps to be taken in the houses. Floor heating and a heat pump coupled with an accumulator enables the use of low temperature design where the heat losses can be cut significantly.