Smart district heating networks – A simulation study of prosumers’ impact on technical parameters in distribution networks

• A district heating network with decentralized solar collectors was simulated.
• Contribution from solar collectors may result in lower supply temperature locally.
• Contribution from solar collectors may result in increased flow velocity locally.
• Contribution from solar collectors may change the differential pressure locally.
• Pipes near the solar collectors will not be influenced by increased fatigue.

Environmental awareness increases, with demands for environmental certifications of new communities and buildings as a result. In the district heating industry, enabling of decentralized energy production is one way to meet requirements from customers. In this paper the technical impact of small-scale local solar collectors and heat pumps on district heating distribution networks is investigated. Customers that in this way can both produce and consume district heating are in this paper called prosumers. The study has mainly been performed through simulations in the computer programme NetSim. The results show that since the supply temperature from prosumers often is lower than the typical supply temperature, contribution from prosumers may result in lower supply temperature and thus increased velocity. The differential pressure decreases when water from the prosumers is mixed with supply water from the rest of the network and increases in the area where the prosumer creates a new pressure cone. Areas that are not reached by water from prosumers are affected differently depending on how the control of the differential pressure is managed. The results also show that prosumers’ lower supply temperature may cause migratory temperature fronts that lead to increased fatigue in the pipes. This was further investigated by the local district heating company and the result showed that migratory temperature fronts generally has little impact on the lifetime of the pipes, since corrosion remains to be the limiting factor. In summary, this paper indicates that introduction of prosumers is possible, but demands management and control.