District heating is a proven technology commonly used in many parts of the world. It is not a technology we have to test or to research. It is here today, it works today, and it holds great promise for London and the UK.

District heating systems use steam or hot water produced at a central plant and then pipes that heating out to buildings in the district for space heating and domestic hot water. Consequently individual buildings don't need their own boilers or furnaces, chillers or air conditioners. The district heating system does that work for them.

The network will make a significant contribution to London’s built environment, both in terms of the speed with which the project can be deployed and its potential to evolve over time, incorporating new heat sources and new developments.

Current heating systems are characterised by a phenomenon known as “lock-in,” which describes why and how some technologies have remained dominant despite the existence of newer and sometimes more heating efficient technologies. The Network overcomes this problem by encouraging a variety of heat inputs to the system, including changing the heat sources to low and zero carbon options from the outset.

Instead of expelling waste heat to the atmosphere, the system could capture heat from various existing power stations around the capital.

Heat can also be captured from existing and yet to-be-built low and zero carbon sources, such as anaerobic digestors, high temperature fuel cells and biomass boilers.

By producing heat more efficiently and transmitting it to where it is needed, the Network will mitigate the Urban Heat Island Effect, a phenomenon that will become increasingly important as our climate changes.

Building owners and managers can count on district heating systems since heating professionals operate around-the-clock and have backup systems readily available. Most district heating systems operate at very high reliability. Thecity scale district heating such systems in Helsinki and Copenhagen have a seasonal reliablity of 99.99%

You may not have heard of district heating, yet these systems operate in nearly every major city in the United States, from Manhattan to Seattle, and in Europe, from Northern Italy to the Polar Circle. District heating is also used in the UK from Edinburgh to London and in Southampton. In Northern Europe, city scale district heating systems cover 50 to 95% of heating demand in almost all cities.

Many people may not be familiar with district heating because it quietly does its job – with rarely a crisis to report. Plus, the pipes that deliver the steam or hot water and/or chilled water are usually buried underneath the streets, so most people don’t know they are there.

The Mayor of London has an ambitious target of reducing London’s CO₂ emissions by 60% from a 1990 baseline by 2025. To help meet that target, the priority is to move 25% of London’s energy supply to local decentralised energy systems by 2025.

Decentralised energy (local generation with district heating where applicable) is seen as a major contributor to meeting this target.

Combined heat and power (CHP)– also known as cogeneration – is a way to increase the efficiency of power plants. Standard power plants effectively use just 40 percent of the fuel they burn to produce electricity. Sixty percent of the fuel used in the electric production ends up being rejected or "wasted" in the process.

CHP uses this reject heat in industrial process or to heat buildings in a surrounding area through a district heating system. CHP is only possible when there is sufficient heat load / requirement near the plant.

Today one of the key challenges confronting the UK is a need to conserve power/energy; what if we doubled the efficiency of as many power plants as possible and got more energy for each unit of fuel they burn? CHP can help us do just that – and even help the environment in the process since less heat and fewer emissions will be rejected into the atmosphere.

Decentralised Energy, CHP and district heating, is more environmentally friendly as it reduces the level of carbon emissions for useable energy - electricity and heat. The reduction is made possible through an increase in overall efficiency and a reduction in losses. The illustration below shows how energy is saved and where there is a reduction in losses.

Illustration taken from Powering Ahead: Delivering low carbon energy for London