Monday, October 02, 2006

Solar PV

Hello There,

In response to a comment posted onto one of my earlier entries I have written about solar PV today to try and give more information.

Solar PV (photovoltaic) technology uses energy from the sun to create electricity to run appliances and lighting. PV requires only daylight - not direct sunlight - to generate electricity.
So yes there is sufficient daylight to operate these systems even in the UK !

How it works:

Photovoltaic systems use cells to convert solar radiation into electricity. The PV cell consists of one or two layers of a semi conducting material, usually silicon. When light shines on the cell it creates an electric field across the layers, causing electricity to flow. The greater the intensity of the light, the greater the flow of electricity...PV systems generate no greenhouse gases, saving approximately 325kg of carbon dioxide emissions per year - adding up to about 8 tonnes over a system's lifetime - for each kilowatt peak (kWp - PV cells are referred to in terms of the amount of energy they generate in full sun light).

PV arrays now come in a variety of shapes and colours, ranging from grey 'solar tiles' that look like roof tiles, to panels and transparent cells that you can use on conservatories and glass to provide shading as well as generating electricity. As well as enabling you to generate free electricity they can provide an interesting alternative to conventional roof tiles!

Solar PV and your home - You can use PV systems for a building with a roof or wall that faces within 90 degrees of south, as long as no other buildings or large trees overshadow it. If the roof surface is in shadow for parts of the day, the output of the system decreases. Please note Solar panels are not light and the roof must be strong enough to take their weight, especially if the panel is placed on top of existing tiles. Very importantly Solar PV installations should always be carried out by a trained and experienced installer and the LCBP grants can only be accessed when using approved contractors.

Cost and maintenance:

Prices for PV systems vary, depending on the size of the system to be installed, type of PV cell used and the nature of the actual building on which the PV is mounted. The size of the system is dictated by the amount of electricity required. For the average domestic system, costs can be around £4,000- £9,000 per kWp installed, with most domestic systems usually between 1.5 and 2 kWp (so thats between £6,000 - £18,000). Solar tiles cost more than conventional panels, and panels that are integrated into a roof are more expensive than those that sit on top. If you intend to have major roof repairs carried out it may be worth exploring PV tiles as they can offset the cost of roof tiles. Grid connected systems require very little maintenance, generally limited to ensuring that the panels are kept relatively clean and that shade from trees has not become a problem. The wiring and components of the system should however be checked regularly by a qualified technician. Stand-alone systems, i.e. those not connected to the grid, need maintenance on other system components, such as batteries.

Payback period:

Very much dependant upon the cost of the installation - on average around 30 years to recoup the total financial investment but this is based upon todays electricity rates. If rates increase the payback period is reduced, and as the market grows competitive influences may also effect the installation costs?


Manufacturers/installers are offering warranty periods ranging from five years to twenty years on average with regular maintenance checks required (rather like servicing a central heating boiler to maintain the manufacturers' warranty).

Planning considerations:

Some local authorities require planning permission to allow you to fit a PV system, especially in conservation areas or on listed buildings. Always check with your local authority about planning issues before you have a system installed. Obtaining retrospective planning permission can be difficult and costly.Interested in introducing a renewable energy technology into your home? The low carbon buildings programme will provide grants towards installing this technology.

From Your Friend The Energy Angel


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