Committee on Climate Change

The main technologies used to produce low-carbon heat are outlined below. Government will need to develop a portfolio of these technologies in order to roll out the use of low carbon heat through the 2020s. Financial support will also be needed to support the development of these technologies.

Heat pumps

Heat pumps use electricity to extract heat from the surrounding environment and transmit this for space and hot water heating. One unit of electricity from heat pumps can generate between two and four units of heat compared to less than one unit of heat via conventional electric heating systems such as storage or immersion heating.

Air source heat pumps (ASHPs)

Air source heat pumps (ASHPs) may be used in buildings with vent or wet (i.e. with radiators or underfloor heating) heating systems.

ASHPs work well in vent heating systems, and their flexibility to be used in reverse for air conditioning in summer has produced high penetration rates in the commercial sector. In the residential sector, ASHPs are most suitable for under-floor heating systems in highly efficient new houses.  For existing houses, ASHPs will often require larger radiators and upgraded insulation to operate effectively, thus substantially increasing the cost.

Ground source heat pumps (GSHPs)

Ground Source Heat Pumps (GSHPs) work well with the same type of buildings as ASHPs. The key consideration is the availability of outdoor space, as a large area is required to install ground loops. Alternatively, bore hole applications require less horizontal space but is more expensive.
 
As with ASHPs, GSHPs are most cost effective in well insulated new homes.   They tend to be more suited to non-urban areas, where space is less of a constraint for installing the ground loops. In some urban areas, more expensive bore hole applications are an option.

GSHPs are not subject to the fluctuations in outdoor temperatures in the same way as ASHPs and can this potentially provide slightly higher coefficience of performance, especially in residential applications.
Heat pumps with storage

These heat pumps are able to recharge during off-peak periods (e.g. overnight), thereby making use of spare low carbon power generation capacity.

Biomass
 
Biomass can be used in a range of applications to produce heat, including biomass boilers in homes and non-residential buildings, CHP for community and large scale district heating and process heat for industry.

In the residential sector, biomass boilers are more suitable in rural or sub-urban areas, both because they can substitute for more carbon intense fuels in off gas grid homes, and there are fewer space constraints and air quality considerations compared to some urban (especially inner-city) areas. There are currently around 4.3m homes without connection to the gas grid.

Biomass boilers and Combined Heat and Power (CHP) plants could potentially substitute for some of the use of oil in industry to produce steam and process heat.

Biogas

Biogas can be used to produce high grade heat, and can therefore be used as a substitute for fossil fuels in residential, non-residential and industrial sectors. It can be delivered either through grid injection or use in CHP plants or industrial boilers.
Biogas is primarily produced by the anaerobic digestion (AD) of agricultural and food wastes, although it can be produced from dedicated crops or a combination of waste and crops.

Solid biomass can also be gasified but development and deployment of such systems is still at an early stage.

Solar thermal

Solar thermal has the potential to supply on average up to a third of household hot water demand and a smaller proportion of household heat demand. In the summer, up to two thirds of hot water needs can be met by a solar thermal system.

The EST and Carbon Trust provide advice to homeowners and businesses on how best to implement renewable technology and the upfront costs.