Solar Thermal: Hot Water from the Sun

Solar thermal collectors

Flat-plate collector efficiencies can be
over 85% in summer. But system
efficiencies over the year are typically
50%.

 

Solar thermal collectors

Most solar thermal systems require a
hot water store and a back up boiler

Solar thermal hot water systems use the Sun’s energy to generate hot water for your household needs.

An installation of between 4m2 and 6m2 on your roof will provide up to 60% of your hot water needs each year.

There are two solar thermal panel options:

  • Flat plate panels typically comprise a sheet of metal in an insulated box with a transparent lid. This absorbs the Sun’s energy and transfers it to pipe work attached to the collector plate.
  • Evacuated tube panels comprise a heat collector plate within a glass tube containing a vacuum. Evacuated tube panels are more efficient during colder weather, as less heat is lost back to the air outside the panel. However, they are slightly more expensive than flat plate collectors.

For solar thermal, you’ll need space for a new hot water storage tank. These are specially designed with an extra coil to accept the solar contribution.

The latest systems commonly include what’s known as a thermal store or heat bank. These provide mains pressure hot water, and also allow excess solar energy to contribute to your room heating requirements in the spring and autumn.

A typical solar thermal installation takes two days, and includes the following tasks:

  • Take out old hot water cylinder
  • Install solar twin coil cylinder or thermal store
  • Install solar panels on roof
  • Install pipework.(usually through the loft space), to the hot water cylinder
  • Install control and pump units
  • Fill up and commission the system.

After installation, most suppliers will provide a follow-up call to ensure that the system is working properly.

Key factors in choosing solar thermal

There are a few things that you should consider with relation to solar thermal:

  • Do you have around 6m2 on your roof to install the panels required?
  • Do you have space inside for a hot water storage tank (around 1m x 1m x 2m high)?
  • What’s your budget? A typical solar thermal system costs between £3,000 and £5,500

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