Solar Water Heating

Solar energy There has long been a misconception that levels of solar radiation in the UK are too low and inconsistent for realistic use in providing heat and power. However, even in the UK, with its uncertain weather patterns, solar water heating can provide around 50% of a household's annual hot water requirements.

Solar energy is one of the most affordable and accessible forms of renewable energy for both the domestic and commercial market. Hot water systems can be installed in homes, community centres, industrial units and even swimming pools. A typical domestic hot water solar system
How does it work?

Solar water heating systems are straightforward and reliable. They need minimal maintenance and have a proven life span of 20 years plus. The sun's heat is absorbed by collectors(panels) mounted on an approximately south facing roof. The panels work throughout daylight hours, even if the sky is overcast and there is no direct sunlight.

There are two types of collector:

It is important to have an informed choice about which is the most appropriate to provide the optimum efficiency for a particular application.

A sensor detects when the collector is at a certain temperature and turns on a pump. Fluid (usually a mixture of water and antifreeze) then flows continuously through the solar collector and is heated by the suns energy. The hot water cylinder contains two heating coils - one for the solar system and one for the boiler system.
The fluid which has been heated by the sun flows through the bottom coil (known as a heat exchanger). This heats up the water in the boiler system. Hot water can then be drawn from the tank in the normal way. The fluid in the solar system will at no point come into direct contact with the water to be used in the building.

The back up of a conventional boiler or electric immersion heater is still needed for those times when the demand is greater than the amount of stored hot water or at times when the solar system is not producing hot water e.g. at night. Correct sizing of the solar system will minimise this requirement.

What does it look like?

Solar installation
Solar installation
The size of the installation depends on the water use of the property. The panels will be situated on a south facing roof and the typical size of a flat plate collector system for a family of up to 4 persons is 3 - 5m2. An evacuated tube collector system will measure 2 - 4m2. However, these are only general guidelines.

Not all houses are suitable for solar panels due to the orientation of house. Panels need to be mounted on a south facing roof to obtain the maximum amount solar energy required.

What does it cost?
The cost of installing a solar hot water system varies from house to house. It depends on the design of the house, the type of collectors used, the number of occupants and the amount of hot water required. Systems can cost between £2,000-£5,000 (plus VAT) for an installed system.

For many people the primary reason for installing a solar hot water system is not finance. Many install this equipment because they want to "do their bit" for the environment using a relatively simple technology. In addition, the rising cost of fuel means the installation of a solar system will become a more attractive and cost effective solution to providing hot water.

What are the cost savings?
Annual hot water bills should be halved and between April and October up to 80% of the domestic hot water required should be provided. Systems can provide hot water heated to a temperature of 70ºC in the summer and 40ºC in winter. For a family of four a well designed system should contribute between 1,500 and 2,000kWh per year.

Realistically, annual savings of between £100 - £150 per year should be expected. It is important to note that the extent of the savings depends on both current hot water use and current fuel used for heating water within the house. For instance, if a lot of water is used and it is currently being heated using on-peak electricity then considerable savings can be made.

Why should I use solar power?
Most of the energy we use in our homes and cars comes from fossil fuels such as coal, oil and gas. When we burn fossil fuels large amounts of Carbon Dioxide (CO2) is released into the atmosphere. The increase in the amount of CO2 concentrated in the atmosphere prevents heat from being radiated out into space. This greenhouse effect results in the heating up of the earths surface, oceans and atmosphere which causes Climate Change. As more harmful gases get trapped in the Earths atmosphere the global temperature rises resulting in more adverse weather conditions. The recent freak weather patterns that we have witnessed, such as El Niño, large tornados and massive floods may all be caused by Climate Change. The increase in flooding occurrences seen across the UK in the past couple of years brings home the effects of Climate Change.

The impacts of unchecked Climate Change will be felt around the world, resulting in increased levels of flooding, famine and water shortages. In the UK rising seas will threaten our coastal communities; higher summer temperatures and less rainfall in the south and east may result in water shortages, and the north west of England is likely to suffer from heavier rain and more flooding. The cost to our society, environment, health and economy will far outweigh any benefit we might gain from having a warmer climate.

There is at present no technology which will prevent the release of CO2. In addition to global warming, burning fossil fuels causes other environmental problems such as acid rain, reduced air quality and habitat destruction during the extraction and transport of coal, oil and gas.

By reducing the amount of CO2 released from your home, you will be helping to reduce the impact of Climate Change.

Can solar power heat my home?
In theory, it is possible. However, in the UK the practical answer to this question is no because the size of collectors needed for such a task would be massive. Here solar water heating systems will only provide enough hot water for washing and cooking purposes, they cannot normally be used to supplement your space heating requirements.

Will a Solar Hot Water System freeze in cold weather, and will snow or dirt affect it's performance?
No. The majority of systems are protected against the cold. Most use antifreeze within the pipes, or have a drainback system which removes the heat transfer fluid from the collector in freezing conditions. Some solar collectors are made from a "freeze-tolerant" material which will not crack when the frozen water inside expands. These frost protection systems are reliable and ensure that your system will not be damaged in low temperatures.
Although snow may form a layer over the collector, the system will still work but with reduced performance.

Dirt on the collector will not affect the system as it works on temperature differential between the absorber and external air rather than sunlight on the surface of the plate. Minimal cleaning is required due to the angle of the collector - rainwater will effectively clean the collector for a long period of time.

Do these systems break easily?
No. This technology has been in use for over 20 years, and has proven extremely reliable. Toughened glass or plastic is used in the manufacture of the collectors, which protects against potential destructive forces. On the whole, these systems are very difficult to damage.

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