The typical configuration of a district energy system is to connect piping trunk lines to the source of energy (e.g., centralized boiler plant, centralized chillers) and for these trunk lines to be buried under streets, where they connect to smaller branch lines which feed individual buildings with heated or chilled fluid. In a multi-building campus setting such as a university, hospital, or industrial complex, pipelines are sometimes run through underground tunnels for maintenance access to equipment such as valves and pumps.
So-called four-pipe systems include heated fluid supply and return pipes plus chilled fluid supply and return pipes to allow buildings to switch from heating to cooling mode as needed. Each building typically utilizes an energy meter device that measures flow rate and change in fluid temperature to calculate its energy consumption for billing purposes.
In geothermal district energy systems (see above), buildings in the same district network can exchange thermal energy with the fluid in a single main pipeline, utilizing heat pumps within buildings to extract or return thermal energy to the main pipeline. In such a system, one building may be heating while another is cooling, with each building exchanging energy with the district pipeline (i.e., ambient temperature loop). In this case, the total energy consumption for the network is greatly reduced, minimizing the use of fossil fuels for energy production.
Heated water can be used for applications such as traditional hydronic heating for space conditioning, radiant heating, outdoor snow and ice melting, and more. Chilled water is used for traditional hydronic heating for space conditioning, radiant cooling, and more.