Solar Hot Water - FAQ
Q. What is Solar Hot Water (SHW) technology?
A. Solar Heating technology means using utilising the sun’s natural radiation for heating hot water. In this way, the abundant free energy from the sun can be harnessed to meet a large part of the domestic hot water demand, and reduce the consumption of conventional fuels. The use of these fuels is now widely recognised as causing climate change, and pollution.
The UK receives a vast amount of solar energy which on average equals to 60-65% of the annual amount received on the equator. The available range of high quality products enables householders to make effective use of the sun. This, even in Spring and Autumn, and on clear but cold winter days, the solar hot water system can prove useful.
The principle system components are solar collectors, a pre-heat cylinder (optional), pump, controls, connecting pipes, the normal hot water cylinder (or a replacement dual coil cylinder) and a conventional heat source.
Q. Are SHW systems suitable for domestic usage?
A. SHW technology is ideally suited for use in residential buildings, providing hot water. The use of active solar heating in households has grown substantially over the last few years. SHW systems can be incorporated into buildings in various ways. Sloping rooftops are an ideal site, where collectors can simply be mounted using frames. Systems can also be incorporated into the actual building/roof fabric. In most SHW systems, only the collectors are visible. In practice, they look similar to darkened roof lights. The overall area of a collector array may be 3-4 square metres.
Q. How does a typical system work?
A. The principle is straight forward. When the sun is shining, water/glycol mixture is pumped through the solar array, and is heated by solar energy. This heated water then flows through a heat exchanger, or cylinder coil, warming the water stored within the hot water cylinder. A boiler or other external heating source provides top up heating. In addition, standard type immersion heaters may be employed.
An electronic controller constantly compares the temperature of the solar collectors within the temperature at the lower end of the hot water cylinder. Whenever the array is hotter than the cylinder (by about 3°C) the controller will switch on the circulating pump. A mixture of water/antifreeze solution is then circulated through the array and the cylinders heat exchange, heating the cylinder in the same way as a central heating boiler.
Q. Temperatures
A. In the summer the water in the cylinder can reach a temperature of 80°C within half a day, and good quality insulation on the cylinder will keep the water warm for the next day. Typically a solar hot water system will reduce domestic hot water costs by around 45%-60%.
Q. What is the energy contribution of an SHW system?
A. For a family of 3-4, a well designed SHW system should contribute between 1,500kWh and 2,000kWh, which would normally be the equivalent to 40%-50% of the household’s water heating energy needs. The value of this saving will depend upon the type of energy displaced (natural gas, electricity, etc).
Q. What are the costs?
A. Typically, SHW systems installed into existing households are priced in the range of £3,750 to £6,000 (depending on the size of the property, type of collector, etc). To encourage uptake, the government offers grants.
Q. Grants available?
A. Home owners can apply for grants of up to £2,500 per property towards the cost of installing a certified renewables or green energy product by a certified installer. The grants are provided by Phase 1 of the Low Carbon Buildings Programme (previously the Clear Skies grant scheme). Details of grants available and how to apply can be found at the LCBP website www.lcbp.org.uk
Public and non-profit sector applicants can now only apply to the Low Carbons Buildings Programme, Phase 2. Grants for up to 50% of the installation costs of microgeneration technologies are available to public sector buildings (including schools, hospitals, housing associations and local authorities) and charitable bodies. Phase 2 of the Low Carbon Buildings Program is managed by BRE on behalf of BERR (previously the DTI). Full details can be found at the LCBP Phase 2 website: www.lowcarbonbuildingsphase2.org.uk
The Community Sustainable Energy Programme (CSEP) is an open grants programme run by BRE, an award partner of the Big Lottery Fund. Part of the Fund’s Changing Spaces programme, CSEP has been set up to help not-for-profit community based organisations in England to reduce their energy bills and environmental impact. Both capital and project development grants are available under this scheme. Capital grants are available for the purchase and installation of a range of low carbon technologies such as solar water heating, photovoltaic or wood fuelled boilers, along with various energy efficiency measures such as cavity wall insulation. Project Development Grants are available for feasibility studies. See www.communitysustainable.org.uk
Q. Will the system work in winter?
A. A standard solar system in the UK cannot provide enough heat to supply hot water at the desired temperature, throughout the year. Most modern SHW systems will typically convert 40%-55% of the solar energy falling into the collectors into useful hot water. Modern evacuated tube systems can reach a peak of 80%-90%.
Although there is normally enough sunshine in the winter to pre-heat your water, you will require a conventional water heating system to back up the solar system during the deeper winter period, or for when demand is high.
Q. Will it require regular servicing?
A. Most modern systems are designed to run virtually maintenance free. As part of the installation package a complete control and running guide, explaining the components and what checks are required are performed.
Q. What guarantee will I get with my system?
A. All the system components are covered by a manufacturer’s warranty (up to 2 years). However, the solar collectors we currently provide have a guarantee of up to 20 years.
Q. Will I need to replace my hot water tank?
A. Most modern systems are designed to fully maximise the power savings made, so normally your existing hot water tank would be changed.
Q. Will Solar work with a Combi Boiler?
A. Most modern combi boilers are designed to accept a hot water feed. Solar hot water can be used to a pre-feed to enable the combi boiler to run off-line.
Q. What size of system will I need?
A. Your system will normally be designed around the number of people living in your house, not the size of house. The solar collector area will depend on the hot water needs of the household.
Q. Do I need planning permission?
A. SHW on roofs do not normally require planning permission, and typically fall within what is known as ‘permitted development rights’. However, if you are dealing with a house that has been divided into flats, building is listed or within a conservation area, you should check with your local council upon policy.
Q. How long will it take to install a system?
A. A fully working system will typically take 1-2 days to install.
Q. Where to put a SHW system?
A. A house roof is ideal for installing a SHW system – there is plenty of ‘unused’ space, the visual intrusion is minimal and direct exposure to sunlight is at its greatest. Roof conditions vary greatly and several key factors should be considered when assessing the solar polarity of a property.
* Orientation - SHW systems are most efficient when installed on roofs facing south, south-west or south-east (up to 95% efficient). In the UK, a north facing SHW roof will normally be 40%-50% efficient
* Tilt – SHW systems can be installed on most flat surfaces. Ideally if roof mounted, they should be inclined, to maximise exposure to solar radiation, and to allow the array to keep clean.
* Available area – a typical SHW array will occupy 2-4m².
* Shadowing or Shading – Preferably the array will not be shaded by neighbouring buildings or tall trees.
Q. What are the benefits of an individual domestic hot water system?
A.
* Provides you with your own clean source of hot water that also helps reduce global warming
* Reduces energy bills
* Can in certain circumstances, increase the value of the property
* Extremely low maintenance, with a long service lifetime of 20-30 years
* Silent in operation and visually unobtrusive
* Increases awareness of energy usage, and encourages more energy efficient behaviour