Q. What is solar water heating?
A. Solar water heating (or solar thermal) systems use energy from the sun to provide hot water. Solar water heating systems typically work in combination with conventional heating systems (i.e. your boiler) to provide you with free, clean energy to heat a significant amount of your total hot water requirements throughout the year.
Q. How does solar water heating work?
A. Filsol solar water heating systems are based on using flat plate solar collectors (or panels) which soak up and retain heat from the sun's rays. This heat is then transferred into the building using a heat transfer fluid that is pumped through the collector. Heat is then transferred into a hot water cylinder via a heat exchanger coil inside the tank where it is stored for later use as required.
For a more detailed description of how solar water heating systems work click here.
Q. Is there a difference in the effectiveness of solar panels in different parts of the UK?
A. The solar radiation received on a solar collector facing due south at an incline of 30° varies from around 900 kWh/m² per year in Scotland and the North of England, to around 1,200 kWh/m² per year in the South West. This illustrated in the map on the right.
(Click on the map to enlarge)
Q. How effective is solar water heating in the UK?
A. A correctly designed and installed solar water heating system can be very effective in providing a significant amount of your total hot water requirements throughout the year, even in the UK. About 4m² of Filsol solar collectors installed on a roof should provide the average household with around 50-60% of their hot water needs spread throughout the year (up to 100% on sunny summer days and even around 10% on a cloudy day in winter).
The best output from a solar water heating system will be achieved during the summer, spring and autumn. However, you can still expect some solar gain during winter months to make a useful contribution to the household's energy needs. On a cloudy day when there is little or no direct sunlight, there may still be 200 W/m² of solar radiation light falling onto the solar collectors. This is sufficiently intense to be usefully collected by solar panels.
The amount of hot water produced will vary depending on the time of year:
- During the summer, a sufficiently large solar water heating system can produce most or all of the hot water required (around 80 – 90% of the total summer hot water needs);
- In spring and in autumn, a solar system can significantly reduce the amount of energy required for water heating, by pre-heating the water in the hot water cylinder so the boiler needs to run less. In this way it can be expected to meet around 40 – 50% of spring and autumn hot water needs;
- In winter, SWH usually only makes a small contribution (around 10 – 15% of hot water needs) as the sunlight is weak and days are short.
It is possible to produce a greater proportion of hot water by installing more solar panels. However, as solar water heating produces most hot water in summer, adding more panels can lead to a situation where the panels produce more hot water than is actually required. Therefore, from a certain point on, every additional panel that is added will contribute less usable hot water than the panel before, and adding more panels eventually becomes uneconomic.
Because the solar radiation is much weaker in winter, and because a large amount of energy is required to heat typical UK houses, solar water heating is normally not used for space heating (radiators) in the UK.
Q. Is my home suitable for solar water heating?
A. The direction that your roof is facing (orientation), the slope or pitch of the roof and shading are all key factors in determining whether solar water heating is right for your home. To achieve the optimum level of efficiency, solar collectors should ideally be south facing, free of shade, and at an angle of 35° from the horizontal. Fortunately the average pitch of a house roof in the UK is about the optimum for receiving solar energy in the UK.
However, systems where panels are facing east or west can be installed and will still make a significant contribution to your hot water requirements. Similarly, roofs pitched anywhere between 20° and 50° will also be suitable although there will be a marginal loss in efficiency. The diagram on the right illustrates how performance of a solar water heating system will vary with tilt and orientation.
(Click on the diagram to enlarge)
Q. How many solar panels will I need?
A. Determining the right amount of solar collectors to suit the requirements of your household depends on a number of factors including your estimated hot water usage, the percentage of solar contribution to the annual hot water load, geographical location, orientation and inclination of the panels, etc.
As a rule of thumb, under typical UK conditions you will need about 1m² of Filsol solar collector per person in the household. A typical four person household would therefore expect to have a 4m² solar collector array.
Filsol solar collectors are available in three different sizes which enable us to design the optimum system to suit the requirements of your household.
Q. How long do solar water heating systems take to install?
A. The time needed to complete an installation will depend on the size and complexity of the job. However, our installers would expect to complete a typical household system in around 1-2 days.
Q. How much will a domestic solar water heating system cost?
A. A typical Filsol domestic solar water heating system will cost between £2,500 and £5,000, including full installation and the cost of a new twin coil hot water cylinder.
A big part of this cost is for plumbing and scaffolding, so you can sometimes save money by installing solar water heating while carrying out other repair work, or by integrating solar in the construction of a new building.
For more details on outline costs for the installation of solar water heating systems in homes click here.
Q. What is the typical payback for a solar water heating system?
A. Depending on a number of key factors including the geographic location of the system, insulation levels (amount of solar radiation) in that area and annual usage of the system, an average four person household can expect to recover the cost of a solar water heating system within 12-16 years depending on hot water consumption and making use of the Renewable Heat Incentive payments (due to come into effect in June 2011).
Q. What is the life expectancy of Filsol solar water heating collectors?
A. Filsol solar collectors have been manufactured and installed at our factory in Carmarthenshire for over 29 years with some of those first systems still functioning perfectly well today. Based on evidence of actual usage, the life expectancy of Filsol solar collectors is therefore in excess of 25 years. All Filsol collectors carry a 10 year warranty as standard.
Should you have any further questions please email enquiries@filsol.co.uk and we will respond as soon as possible.
