Some buildings produce a lot of waste heat just by doing their normal job — a data centre's server racks, a supermarket's refrigeration compressors, a wastewater treatment plant's process tanks. On their own, that heat is simply vented into the air and lost. A district heating network connects buildings together with insulated underground hot-water pipes, so waste heat captured at one building can flow to other buildings nearby that need heating — homes, offices, a school — displacing the fuel or electricity those buildings would otherwise burn.
A single mid-size data centre can reject enough waste heat to warm hundreds of nearby homes — several European district heating schemes now route server-room exhaust heat straight into the network instead of running rooftop cooling towers.
A six-plot city block where you decide which buildings sit where — waste-heat sources like a data centre, a supermarket and a wastewater plant on one side, heat-hungry homes, offices and a school on the other — all tied together by an underground district-heating pipe loop.
How much waste heat a network actually recovers depends on matching supply to demand: recovered heat can never exceed whichever is smaller, the waste heat generated or the heat requested, so the comparison against a "no network" baseline shows the real fuel savings.
Assign a building to each of the six plots, adjust winter demand severity, and flip the network switch on and off to compare live fuel-consumption readouts with and without heat sharing.
A supermarket's refrigeration system rejects heat all year round — pairing it with a nearby swimming pool or apartment block through a heat network can cut both the supermarket's cooling bill and its neighbour's heating bill at the same time.