What are Solar Thermal Heating Systems?

A Solar thermal heating system will provide a significant proportion of a typical household’s annual hot water requirements, as opposed to space heating. The proportion of hot water provided and the subsequent energy savings will depend on the level of hot water demand. The higher the hot water demand, then the greater the energy savings. Most manufacturers will claim that a typical system can provide between 50 and 70% of domestic annual hot water requirements. A typical household will normally use about a quarter of their gas or oil bill on hot water heating. Ultimately, if you have a higher than average annual hot water demand, then the greater the potential savings. If you are already frugal with your hot water, then you probably won’t save that much.

This is a genuinely “green” technology utilising sunlight. The only energy input in most systems is the operation of a 50 watt pump. Solar thermal systems are different to photovoltaic panels, which produce electricity.

How does it work?

The principal behind the technology is simple enough. It involves a black metal surface known as a “collector”, with a tube of liquid (usually an antifreeze mixture) running through it. Light radiation from the sun warms the collector, and the liquid is then transferred through pipe work to a heat exchanger in the hot water cylinder.

Most households will need a new twin coil hot water cylinder. This means that there are 2 heat exchangers in the cylinder. One heat exchanger is for the solar circuit and the other is for the main boiler. These cylinders are usually much better insulated than the ones that they replace, so there will be less heat wasted.

What types of collector are there available?

There are 2 types, Flat Plate collectors and Evacuated Tubes. There are advantages and disadvantages to both systems. In the UK, the majority of installations tend to be use flat plate collectors.

Can a solar system be used in conjunction with a combination boiler?

A system can be used with combination boilers that are able to use pre heated water. For which there are a handful of certified boilers on the market. Ideally, you need a hot water store, so for some people, this will mean a new boiler as well.

Where will the collectors be mounted?

For most households, the collectors will be roof mounted, preferably in a South facing position, although anywhere between South East and Southwest. East / West arrays are not ideal, but they can still be effective, although often such a system will need to be oversized to compensate for any efficiency losses.

Usually scaffolding will be needed to safely mount the collectors on the roof.

The distance from the collectors to the hot water cylinder can also be a factor, in terms of any system losses, so the hot water cylinder should be situated as close as possible to the site of the collectors.

How hot do the panels get?

During the summer months, temperatures in the solar circuit can reach boiling point, which is why there are a number of safety features in a well designed system to limit the temperature in the hot water store.

Does it work on cloudy days?

A typical system will work on a cloudy day, but at lower levels.

Will it work in winter?

Yes, there will be a benefit in winter, even if it is only to preheat your water, which will take some of the load off your boiler. If it is a cloudy dark day in January, then any benefit will be minimal. It is also worth noting that these systems work in freezing temperatures, as it is the amount of solar radiation available that is crucial, not the air temperature.

Are there any grants available?

The Government has proposed a Renewable Heat Incentive. To qualify for these annual payments, the system will need to be installed by someone accredited under the Microgeneration Certification Scheme (MCS). At the time of writing, the Government’s public consultation had finished and the final announcement to confirm the RHI is awaited.

Can I install a system myself?

Yes you can, but you will be paying VAT at the normal rate (17.5% at the time of writing). An installer accredited under the MCS will charge you VAT at the current reduced rate of 5%

Where can I get further information from?

Read more on this website, or contact us for information regarding your specific needs. We cover Nottingham, Lincoln, Leicester and Derby.