Dynamic modeling for evaluation of triple-pipe configuration potential in geothermal district heating networks

Highlights: • Triple-pipe configurations for extension of existing DH reduce return temperatures. • The rate of renewable energy of geothermal/gas thermal plants is improved. • Triple-pipe distribution is more efficient than heat exchanger cascading. • The benefits of these solutions are sensitive to network extension heat load. - Abstract: District Heating (DH) systems will play an important role in future sustainable energy systems. Existing networks can be optimized by lowering primary return temperatures in order to improve the use of geothermal resources. This can be done by installing triple-pipe systems. This paper defines the concept of triple-pipe configurations as it is understood in France. The objective of this paper is to demonstrate the relevance of those configurations for optimizing geothermal DH system efficiency. A dynamic thermal-hydraulic model was developed using the programming language Modelica. A generic case study is modeled considering the extension of an existing network. It is shown that triple-pipe configurations offer lower return temperatures and gas consumption, while increasing of the renewable energy share in the network energy mix.