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Solar Thermal Bedfordshire

Experts in solar thermal across Bedfordshire


How does solar water  heating work?


Energy from sunlight is absorbed by the solar panel and converts it to heat energy. This is then removed by a heat transfer  liquid usually water or anti-freeze. In most systems, a small pump is required to circulate the heat transfer fluid to where it is immediately needed, or to a store from which it can be used later. In the case of solar hot water systems, this is usually a hot water cylinder. A back-up heat source is required to ensure that the water is heated to a sufficient temperature on days when light levels are limited. The water in the cylinder is then fed to your taps and showers to provide hot water for your home. There are many different types of solar water heating systemsand we will be able to advise which is best for you.

What are the benefits of solar water heating?

There are numerous benefits to installing solar water heating:
• One of the cheapest and most established of all the renewable energy technologies
• Designed to work alongside the majority of heating systems
• Provides roughly half of your hot water requirements across the year and during
the summer months they can contribute towards nearly all of your hot water needs. During the winter months you may need to top up the system with your primary heat source e.g a boiler.

Costs and Bill Savings

Solar thermal technology has lots of advantages – it’s low maintenance, it will save money year after year and the system is relatively inexpensive compared with other microgeneration technologies. So how much do you need to invest, and what will you get back?

The cost of your solar thermal installation  will depend on a number of things  including the number of panels, the complexity of the plumbing and the suitability of your existing hot water system. A typical system would cost between £4,000 and £5,500, and you’ll be able to get £300 towards this from the government as part of the  Renewable Heat Incentive, visit  to find out more.

Depending on how you use it, a well-designed and properly sized solar thermal system can help you make a substantial saving on your bills. You can expect it to provide:

  • 80-90% of your hot water in the summer
  • 40-50% of your hot water in the spring and autumn
  • 10-15% of your hot water in the winter

You’ll make the biggest saving if your hot water is currently heated by electricity, followed by oil and then gas. However, the actual savings you’ll make on your bills will depend on how you use your hot water. The best way to find out what you could save is to talk it through with one of our advisors.

Is solar water heating suitable for my home?

Solar water heating systems can be designed to fit into most existing heating systems. Typically, all that is required is a roof facing within 90° of south and a space for storing the hot water. A range of factors will affect what is best for your needs. We will be able to assess your situation and discuss with you the best option to meet your requirements. A few points to consider before installing:

Are there any energy efficiency measures that can be implemented, such as draught proofing, loft and cavity wall insulation?

These simple measures will provide long term financial and carbon savings

Roof orientation
Unobstructed roofs facing south are ideal. Shadows from trees, chimney stacks and other buildings will reduce the amount of heat produced from your solar water heating system. The majority of roofs should have a suitable roof pitch, although for flat roofs angled mounting frame kits are available. However, this arrangement will make your installation more complex and probably more expensive. It is not advisable to install solar panels on a north east, north or north-west facing roof.

Space requirements
Roof space: typical hot water panels vary in size from around 2-4m2, though some systems may be even larger depending on hot water demand.
Internal space: Additional space may be required internally, either through a sufficiently sized replacement hot water tank, or a separate storage vessel alongside your current hot water cylinder. Other factors affecting space requirements include: householder hot water use, the number of occupants and the expected performance from a system to meet overall hot water demand

What are the key components of a solar water heating system?

There are a number of key components that make up a solar water heating system. The solar panels are generally located on your roof, these capture the sun’s energy converting it into domestic hot water. There are currently two main types of panels available on the market: flat plate and evacuated tube.

Solar Panels

Flat plate panels

These consist of a glazed, flat, dark surfaced absorber plate, which can either contain metal (copper or aluminium)or rubber (silicon) tubing. The plate absorbs incoming solar heat energy and the casing minimises heat loss. A fluid is circulated through the tubing and this fluid heats up as it passes through the absorber plate. Water or anti-freeze can be used as the fluid, though this depends on the system and type of tubing used.

Evacuated tubes


These consist of parallel rows of transparent glass tubes which contain an absorber insulated by a partial vacuum. These can be more effective throughout the year than flat plate panels but tend to be more expensive.Both system types are designed to be freeze tolerant and will therefore continue to function during the UK winter season.

Hot water cylinder –  To make the most of the available solar energy you need a hot water cylinder to store the heat between the time it is collected and the time you use it. Generally this would be found in your airing cupboard. The two most common types of hot water cylinder used for solar water heating are:

Twin coil cylinder – most common type used in the UK. Replaces a standard single coil cylinder with a twin coil cylinder, where one coil is located above the other.

Pre heat cylinder – Another option is to keep your original cylinder and have an additional single coil cylinder known as a pre heat cylinder. The water is heated with solar energy before it passes to your existing cylinder.

Other options include heat to base cylinders where both coils are contained at the bottom of the tank. You can also have a thermal store which can act as a ‘thermal battery’ for storing your hot water. This is often found when combining with another renewable technology such as a heat pump. If necessary your boiler or immersion heater can be timed to top up the heat in the evening after the sun has gone down. The water can then be used later that evening or the following morning. If the hot water is heated by the boiler or immersion all day the solar panel will not be able to contribute very much heat.


The most common method to circulate solar heated transfer fluid from the panels to your hot water cylinder is with a pump. The power source of a pump is typically derived from the grid mains electricity but can also be powered by solar photovoltaic panels.  When you install a solar water heating system, there will be additional pipe work required to circulate the fluid to and from your solar panel. This is known as the flow and return pipe work. For the system to perform at its best, it is important that the pipe work is the shortest length possible and is well insulated.

System controls

Your solar water heating system will have a number of temperature sensors which feed information back to a central control unit. The main control unit will serve a number of functions including:

  • Letting the system know when to switch the pump on or off. The temperature of thesolar panels will be compared with the temperature of the water in the storage cylinder(s). If the panel temperature exceeds the storage cylinder temperature by more than a set amount, the controller will switch the pump on.
  • To notify the existing heating source (i.e. boiler) when to switch on if there is insufficient solar energy.
  • Turning the pump off when the system is overheating.
  • To inform you of the operational temperatures at various points in the system, for example in the solar storage cylinder and solar panels.
  • To notify you of any system malfunctions. There are also a number of ways in which the solar water heating system can be set up including circulation and pressure options for the fluid in the panels. We can advise which is best for you.

Integrating with existing heating systems – If your home has a conventional boiler and a hot water cylinder

Installing a Solar system is usually just a case of fitting the panels to the roof with the associated pipe work and then replacing the existing hot water cylinder with a twin coil, thermal store or connecting a separate pre-heat tank to the existing cylinder.

If your home has a combi boiler or an electric water heater

Your system may not be designed to receive heated hot water. However, some appliances may display a mark to indicate suitability for pre-heating, when internal components have been tested to a higher temperature. We would recommend that you check with your boiler manufacturer to see whether your hot water system is ‘solar ready’.


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