District heating network modelling for future integration of solar thermal energy

Abstract

A key advantage of district heating networks is their ability to integrate different renewable energy sources, from geothermal to solar. However, the success of this integration depends on a variety of design and technical decisions, such as feed-in locations or operating temperatures, which need to be compared and analysed. For this purpose, dynamic models of district heating grids, which allow for an hourly representation of the thermodynamic conditions, are necessary. This type of models are nevertheless still uncommon, drastically limiting options to perform these comparisons accurately. To address this challenge, an open-source tool to model district heating networks is presented here and successfully applied to two case studies in western Switzerland. These simulations are then used in conjunction with simplified models of storage and solar thermal collectors to investigate, in a preliminary way, the impact of solar thermal integration on the mass flow and temperature of the network pipes, illustrating the interest of the proposed method to compare different configurations of renewable heat injections in district heating networks.