Low-temperature district heating distributed from transmission-distribution junctions to users: energy and environmental modelling

Abstract

We herein discuss a smart district heating (DH) grid whereby smooth operation is achieved, and individual heating solutions, and passive or energy+ building-specific systems are implemented by means of flexible heat demands, thermal energy storages, and transmission resources. For future energy systems, low-temperature district heating lines combined with heat savings and reduced environmental impact represent a promising alternative to integrating fluctuating renewable sources. What makes this study relevant is scientific need of having a low-temperature distribution branch within an existing exclusively high-temperature district heating system. Non-renewable heat production is partially replaced with heat pumps and thermal energy storage facilities. Heat pumps use renewable electricity to produce completely renewable heat. Fundamental technical and consumer-oriented aspects of the power system will have to be adapted to using heat pumps and thermal energy storages.We created a large database of validated heating uptime values for specific buildings and outdoor conditions. We herein dwell upon an alternative heating design. The new concept is based on using transformation units as well as branch lines going from street mainlines to consumers’ substations, whereby a branch line consists of two single pipes, a dual pipe, or a triple pipe. Such branching creates a subnetwork with different heating parameters. The temperature for such a subnetwork is specifically optimized. Optimization relies on such as data as use of thermal energy, heat loss rates, and parental-system data. As a result, we modeled a network whose primary nodes had a low operating temperature. This reduces heat loss as well as fuel consumption while enabling less environmentally harmful heat production. Besides, such use of thermal energy combined with self-production can be important for creating renewable energy systems in the future. Therefore, future research and development shall be targeted at creating low-enthalpy facilities that use renewable energy to produce and store thermal energy as simulated when modeling such a modified subsystem (subnetwork).