Solar Thermal Water Heating
What is solar energy?
The sun provides an abundant and free source of clean energy in the form of heat and light. Some of the heat energy provided by the sun can be harnessed to provide hot
water in your home.
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.
What are the benefits of 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.
One of the problems with solar thermal water heating is that it is comparatively expensive to install when compared to the level of savings that the resident would experience. It is currently found mostly in new build, where it is helps developers achieve required carbon emissions reductions.
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 diagram above shows the main parts typically found in a solar water heating system.
Solar panels: Generally located on your roof, these capture the sun’s energy converting it into domestic hot water. 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.
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. 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.
As fuel prices increase so will the savings from using a solar water heating system. By generating your own clean energy you will help protect yourself from rising fuel costs. However, the overall financial benefits of a solar water heating system will depend on a number of factors including:
• what fuel is being displaced
• how much hot water is used in the home, when it is used and how much you depend upon the primary heat source (e.g. gas boiler)
Residents with solar thermal water heating should not expect to save more than £75 per year.
Getting the most out of your system
• Make sure you use your heating controls to adjust your heating running times in accordance with your needs throughout the year.
• Make sure you use hot water later in the day (if possible), once the solar water heating system has had the chance to heat the water, for showering or washing the dishes. Only use back-up heating when you need it; ideally have it set to come on immediately before hot water use or at the end of the day.
• Be careful not to waste water just because it’s heated for free. Even before the water reaches your home it requires energy to clean and transport it.