Feed-in from Distributed Solar Thermal Plants in District Heating Systems

A District heating (DH)feed-in system is connected to the DH system outside themain central pumps. There are fourdifferent ways to connect a feed-in system to the DH main line but the most frequently used are return/return (R/R) and return/supply (R/S). R/S is the most beneficial system sinceit influencesthe DH system the least. For an R/S feed-in system, there are two basic control concepts; a temperature controlled system and a flow controlled system. In the temperature controlled system there is always a shunt flow which the flow controlled system lacks. It is possible to build a combination feed-in system but the risk of poor performance increases. More field testswill be done during the summer 2017