Solar Water Heating is a system for heating water using energy from the sun. Solar energy is collected by a panel, which is connected by pipes to a hot water storage device such as a hot water cylinder.

In these collectors, water circulates through a network of channels, getting warm as it moves though it. The warm water is then returned to the hot water tank or to a swimming pool.

Solar water heating systems are the most popular form of solar energy used in the UK, as there are now over 50,000 solar water heating systems installed.

The solar panel is fitted usually on a roof and is suitable for all house types, even those with flat roofs. A roof facing south is ideal, but between south east and south west is also quite good with little or no shading is best. Usually it would require 2 – 6 m2 of exposed roof for an average household’s domestic hot water system.

Solar water heating can be used for domestic water heating and also for larger scale applications including swimming pools. Most systems work in conjunction with some other form of water heating system to ensure hot water is available all year round.

There are many different system types and configurations for solar hot water systems. The most common commercially available systems are flat plate and evacuated tubes.

The simplest and most common type of solar panel is known as a ‘flat plate collector’ that consist of a large area (typically 2m2) absorber, which is housed in a well-insulated casing with a glazed front, which serves to limit heat losses to the atmosphere. Heat is transferred from the absorber to a fluid flowing through channels within or attached to the absorber plate.

In an evacuated tube collector the piping, coated in an absorber, is enclosed within a vacuum. This prevents heat loss by convection, so the fluid warms up quicker.

Evacuated tube systems occupy a smaller area and have an efficiency of approximately 40% but are generally more expensive. Flat plate systems have an efficiency of around 30% and are cheaper to install.

SWH depends on radiation, not direct sunlight, so it works even on dull days. Assuming it is properly sited, most systems would be able to supply all the domestic hot water needed by an average household during the summer months. In winter, depending upon the type of system installed, between 10% and 50% could be expected.

Most combi-boilers may not be compatible with this system as the water entering the boiler could be hotter than the water leaving. If that is the case, additional thermostatic boiler controls may be required or the boiler replaced with a compatible one.

Solar Water Heating will reduce your impact on the environment – the average domestic system can reduce carbon dioxide emissions by 0.4-0.75 tonnes per year, depending on the fuel replaced.

SWH will also stabilize energy costs for the future, as fossil fuels become more expensive. And the capital is recovered in around 15 years.

Planning permission may be required from you local authority in some cases, depending on where you live.

The table below gives an idea of the system requirements for various sized households. This is a rough guide as it depends on many factors.

Costs vary due to a range of factors such as size of collector, type of roof, existing hot water system and geographic location.

Low Carbon Buildings Programme offers grant of £400 on installed systems.

You can also fit or build the system yourself. It can work out cheaper but will take longer and you’ll need a certain level of skill. However, DIY jobs are not eligible for grant funding.

Links for Further Information:

http://www.solartradeassociation.org.uk       http://www.brookes.ac.uk/other/uk-ises