Examples of how district heating is used

Here you will find more detail about how district heating works.

How the heat is generated, distributed and used

The three main elements to district heating are heat generation, distribution and energy use.

Heat generation

Generation can be heat only, combined heat and power (CHP) or in specifically designed systems combined cooling, heat and power (CCHP). This can be done from the very large scale, providing heat for many thousands of users, right down to a single building. A flue is necessary to remove exhaust gases from any boiler or CHP engine.

Energy sources can include:

  • gas
  • biomass
  • biogas
  • geothermal heat
  • solar heat
  • surplus heat from industrial processes
  • conventional fossil fuel power stations
  • nuclear power.

Plant room at Seaton This plant serves the district heating scheme at Aberdeen Seaton
Phase 1 for around 600 flats. It is a 1 MW gas-fired CHP with a back-up boiler serving.

 

Distribution

Heat is distributed in the form of hot water or steam via insulated ‘flow' (also called ‘feed') pipes from the plant to buildings. It is then returned from the buildings to the plant via ‘return' pipes. Normally pipes are installed below ground, though it is possible for them to be above.

Energy use

Distributed heat is used to centrally heat homes and other buildings and to provide hot water. Water or steam can be used directly in a building's water or heating system. More normally, the district heating pipes connect to a building's heat exchanger, where heat is transferred to the central heating system.

Suitability for district heating

Whether or not an area is suitable for district heating will depend on the following factors:

  • development density
  • demand loads - how much heat is required in the area
  • load diversity - the mix of uses of buildings
  • the age of the buildings
  • anchor loads - the availability of buildings requiring a large amount of heat
  • the presence of physical barriers (for example, railway lines, roads and rivers).

District heating can be part of a new development or retrofitted into existing development. Different scales offer different opportunities. For example, you could have the following scales serving different urban areas.

Block-based: with each block in a development having its own system.

Site-wide: where a single energy generation source or small number of sources serves a number of buildings connected by a network.

District-wide: where a neighbourhood, parts of a town or a whole town centre are served by a network supplied by a large single source or several sources.

City-scale: where several large heat sources are connected to a network supplying several districts.

Managing installation and maintenance

Installation

District heating projects are complex to install because they involve the connection of new and existing development, multiple land and building owners, and disruption to road networks. They are also likely to be expensive. For these reasons, it is likely that local authorities will play a major role in their planning and implementation.

The disruption, complexity and expense are likely to be less for the installation of networks serving a single new development. But local authorities will almost certainly need to lead more strategic networks serving multiple developments.

Different parts of the project may be led, owned or operated by a combination of public, private or third-sector organisations.

Maintenance

The pipes will need almost no maintenance once installed. Pipes should include a leak detection system.

The plant and boilers require operational staff and annual routine maintenance.

The heat exchanger requires annual routine maintenance.

 

1 May 2012

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