Five key ways to get the best from your solar hot water system
Posted by Cathy Debenham on 19 October 2011 at 1:17 am
Solar hot water systems work best when the user takes control of them, yet only 36 per cent of the householders taking part in the Energy Saving Trust's solar hot water field trial said that their installer gave them information on how they might make best use of their system.
When they did give advice, most of it related to advice on modifying the time of day people use hot water (have showers, baths or use appliances), and only a quarter to advice on hot water system settings and integration - which can make much more of a difference.
The key ways to improve the performance of a solar water heating system identified in the trial are:
1. Use boiler timers and/or solar controllers to ensure that water is only heated by the back-up heating source (ie the boiler or immersion) after the water has been heated to the maximum extent possible by the sun. This is likely to be after the sun has left the panels (solar collector). When you use hot water during the evening and early morning hot water, you will ensure that there is plenty of cold water in the cylinder for the sun to heat the next day. Using back-up heat in the morning means less opportunity for the sun to contribute.(We tend to turn our boiler off altogether from around mid April to mid September, just using it to boost the cylinder when necessary).
2. Have an adequately-sized section of the hot water storage vessel that can only be heated by the solar water heating system. This will generally be a twin coil cylinder where one section is only heated by the solar collector, or a thermal store. If a dedicated solar volume is not used, for example in systems that do not require the existing cylinder to be changed, the timing of back-up heating has a even more important impact on performance.
3. Adequate insulation of cylinder and pipes is vital. Systems with poorly insulated cylinders can suffer from inadequate hot water provision in the mornings.
4. Use of electric showers, which heat water themselves rather than using the solar-heated water, will reduce overall hot water use, meaning that you won't get maximum benefit from having a solar water heating system.
5. Allow the hot water temperature to vary. If you do not need high temperatures all the time, you will have less need for back-up heating. You will also reduce heat loss. However, it is important to make sure your cylinder reaches more than 60 degrees centrigrade at least once a week to avoid risk of Legionella.
MCS standards require installers to communicate the how the timing of back-up energy sources can impact overall system performance to householders. Let us know if you got the best advice from your installer, by commenting below.By Cathy Debenham
If you have a question about anything in the above blog, please ask it in the comments section below.
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