District heating has become the favored method of heating of many cities in Europe. It has also risen in popularity and use throughout much of the rest of the world. District heating is actually more than 100 years old. It started in 1903 in Moscow, Frederiksberg and Copenhagen, all in the same year.
District heating systems as a modern concept were designed and introduced in the 1980’s (with constant breakthroughs since then), with automatic control, remote monitoring and un-manned operations. The district heating concept binds together available heat sources, which otherwise would be wasted, for heating or to produce cooling.
A typical district heating installation consists of a highly insulated "heat main" of flow and return pipes distributing hot water (or steam) past all buildings which are connected. A junction point allows easy connection to each building, from which hot water can be taken from the main to a heat exchanger (heat substation) within each building. The heating circuit within the building is thus isolated from the heat main.
Temperature measurements of the flow and return lines, plus a flow meter (together forming a heat meter), allow the actual heat usage within each building, or even apartment, to be separately measured, delivered and billed for accordingly. Remote meter reading, by a modern, secure web interface, or a drive-by, are both usually possible, as are remote diagnostics to ensure reliable operation.
Many district heating networks also use cogeneration, or combined heat and power (CHP). CHP is the production and use of electricity and heat simultaneously from a given energy source. The sources for CHP (and district heating) typically are: natural gas (dominantly), coal, oil, heat from waste incineration, waste heat from power production, industrial waste heat and biofuel boilers. Solar and geothermic energy are sources of renewable energy that are also used in district heating/ cogeneration systems. The market has further developed through the use of natural gas in district heating networks.
For any modern city with a dense population, a district heating supply offers the most significant contribution to ensuring energy efficiency that's readily available. District heating is used in many cities (especially in Europe), but needs to be used more in major cities throughout the world.