Design and performance of a multi-level cascading district heating network with multiple prosumers and energy storage

Urban city districts nowadays contain heterogenous mixes of buildings with different age classes, usage profiles, heating demands and temperature requirements. Furthermore, increasing numbers of new and refurbished buildings are equipped with renewable energy sources that partially or entirely cover the building’s heat demand. These sources often have the potential to generate heat surpluses, turning the building into a ‘heat prosumer’. The successful integration of prosumers into district heating networks (DHN) is paramount to their decarbonization but is often limited by the high supply temperatures required by unrefurbished buildings.To respond to this challenge, this paper presents a concept for a cascading three-level DHN with multiple prosumers and thermal storage which aims to increase the efficiency and the share of renewable energy integration in the heat supply. The concept has been developed and is currently being implemented for a complex of five university buildings at the Technische Universität Berlin which exhibit a variety of heat consumers and decentralized sources such as waste heat from data centers and geothermal energy.