Solar thermal

Renewable and low carbon technologies

Solar thermal systems use energy from the sun for heat, usually to provide hot water in the UK. They use a heat collector, usually mounted on the roof, which contains a fluid that is heated by the sun. This fluid then heats up water stored in a hot water cylinder (thermal store) inside the building. Once installed, they generate no CO₂ emissions.

Types of collector

• Flat plate
• Evacuated tube

Other components

• Separate hot water cylinder or twin coil hot water cylinder
• Usually installed with an additional heat source such as a gas boiler to maintain high enough temperatures year-round

Typical savings

Zero carbon renewable energy source. Energy savings average at around 454kWh/year saving per m2 of flat plate collector, or 582 kWh/yr per m2 for an evacuated tube system. A 4m² collector area typically provides 50% to 60% of a typical home’s hot water demand.

Indicative cost

£2,500 to £4,000 for a household system (4m2 collector). Larger variation in costs for non-domestic systems, due to site-specific issues.

Main issues affecting feasibility

• Hot water demand: there should be year-round demand, including summer.
• Location: the collector should ideally be mounted on a south-facing roof, south-east/south-west will also function successfully, at a pitch of between 10 and 60°. The hot water cylinder should be located as close as possible to it.
• Shading: shading will reduce output and should be avoided where possible.
• Visual impact: may need careful design for use in conservation areas.

Further information

London Renewable Energy Toolkit http://www.london.gov.uk/mayor/environment/energy/renew_resources.jsp