Energy from the Sun
PUBLISHED: 16:01 08 January 2008 | UPDATED: 14:59 20 February 2013
The UK receives vast amounts of solar energy - equivalent in output to 1,000 power stations. It's a resource that's likely to be used more and more
'Active solar' uses panels or collectors of some kind to harness the sun's energy. 'Passive solar' refers to the orientation of a building to maximise the sun penetration, and thus to heat the building.
Solar panels can be either photo voltaic (PV) or solar thermal. The former is a silicone cell with a chemical inside that, when heated by the sun's radiation, produces electricity. A solar thermal collector is a black panel with water passing over it - a simple heat exchanger unit. So the former creates electricity, the latter heats water.
How do active solar heating systems work?
Solar thermal panels that are fitted to your roof collect heat from the sun which is piped into the house's hot water cylinder (you will need a new cylinder), where it joins water heated by your domestic boiler. On a sunny or light day the energy from the sun can provide all an average house's daily hot water - water temperatures of 70-90°C are common. On cloudy days the boiler will have to kick in to bring the temperature up but some hot water will be produced as the system utilises energy from diffused light - the radiation from the sun is still getting through.
In winter the system will pre-heat the water in your cylinder, meaning the solar system will make meaningful reductions to your gas, oil or electricity consumption throughout the year as it's 'topping up' all the time and reducing the work required by the boiler. And, because solar hot water systems are designed to store larger amounts of hot water, a correctly sized system will have hot water left over from the previous day. If you have a few cloudy days in a row the thermostat will turn the booster on to bring the water up to temperature.
Photo voltaic (PV) produces power, which is great for boats, camping, charging your mobile phone or powering lighting at home. It also only needs daylight, not direct sunlight and can still generate power on a cloudy day.
A roof-top installation with a solar thermal array will probably be the most popular choice for most homes. Solar thermal is the cheaper option. Commercially PV may be better, as there is a lower demand for hot water in a small office building and it is more expensive to install. For the average domestic PV system, costs can be around £5,000-8,000 per kWp installed (most domestic systems are between 1.5 and 3 kWp).
For successful solar power, all a property needs is an area of roof roughly south facing to give maximum exposure to the sun.
How much will it cost?
Typically a system for a new-build three-bedroom terrace house costs between 2,000-2,500, while a system fitted to an existing house will be in the order of 2,500-3,500. There is some disruption when swapping over the hot water cylinder but generally a good plumber and roofer can do all the work in around a day.
System life expectancies can exceed 30 years and there's very little maintenance required. A pump is the only moving part and these are available from a plumber's merchant at a reasonable cost.
Government-funded grants are available for installation. The DTI's Low Carbon Buildings Programme will provide grants for micro-generation technologies for householders and non-profit community organisations such as registered charities or community groups. However, in order to be eligible, you will need to insulate the whole of your loft to current approved levels; install cavity wall insulation (if you have cavity walls); fit low-energy light bulbs in all appropriate light fittings and install basic controls for your heating system to include a room thermostat and a programmer or timer.
Look into this simple technology sooner rather than later as there are savings to be had for both your pocket and greenhouse gas emissions. The Solar Trade Association (01908 442290) is a good place to start your research.
For more information contact Philip at pdmdesign, 01392 879218