Ourpower Guides - Solar Photovoltaic (PV) - Details

Every day the Earth receives more energy from the Sun than the whole world consumes in a year.
- Solar PV produces electricity.
- Direct sunlight is best, but significant electricity is also produced in cloudy conditions.

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Uses

Solar PV systems are used for:

• Producing electricity at home, with solar panels typically attached or integrated into the roof.
• Remote applications, to charge lighting systems or road traffic signs.

How does Solar PV work?

A photovoltaic system comprises:

• Modules (panels) -usually on your roof - to convert solar energy into electricity
• A wiring system to connect to your electric system, including inverter and controller to convert the DC electricity to 240V AC for use in the home or to export back to the grid.

A module consists of a number of photovoltaic cells made from 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.
These are typically bolted onto your roof, or incorporated into the roof structure for a 'new build'.

The benefits - why install?

• You will be at the forefront of renewable energy developments.
• You will help alleviate global warming because a home system reduces carbon dioxide emissions by up to 3/4 of a tonne per year.
• A small home system can typically provide 25% of your electricity needs, and in certain cases a lot more, particularly if you are more careful with your energy use. Some properties can generate 100% of their energy needs
• A solar system will increase the value of your home.
• The systems are expected to last 30 years or more, need very little maintenance and are very reliable.
• Solar systems help safeguard against future rises in fuel prices, providing-inflation proof electricity for 30 years and more.

Is it suitable for my home?

Factors that need to be considered are typically:

• South-East to South-West facing roof space that receives direct sunlight throughout the day - shading by trees or other buildings will reduce the amount of electricity produced.
• Roof space, you need about 10 square meters, which must be able to sustain the increased weight of the panels. However, modern panels are relatively light-weight.
• Planning permission needs to be considered and you should consult your local authority. Roofs facing the road, period houses or those in conservation areas may need plannig consent.

An accredited installer or supplier will help you plan the best system for your circumstances and budget.

Different designs used

Depending on your circumstances and the system installed, there may be certain differences in your system. Examples are:

• Solar PV cells come in 2 distinct types:
  o Crystalline - the most common and efficient construction, requiring less space for the same electricity. There are various types of crystalline cells.
  o Thin film - tend to perform better in low light, but require a larger surface area. The costs are generally similar.
• The panels can be constructed differently depending on the situation:
  o Typically, the modules are bolted into frames to then be attached to the roof tiles.
  o The modules can be integrated within roof tiles or other similar roofing materials to replace current tiles.
  o Or the PV modules can be incorporated into thin, flexible sheets to be bonded to your roof or incorporated within glazing.
• Grid connection or not?
  o On-grid systems require electrical components to convert the current to 240V AC and to allow selling of excess power to the grid.
  o Off-grid systems will require batteries to store the electricity for use, for instance, at night.

Installation, maintenance and costs

Prices for PV systems vary, depending on the size of the system to be installed, type of PV cell used and the building on which the PV is mounted. Systems are typically rated using the term 'kwp' - peak kilowatt. In the UK, a 1 kwp system is, if correctly sited, to produce about 750 kilowatt hours (or units) of electricity per year. One household uses about 3,500 units per year.
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. 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.
Grants are available from the Low Carbon Buildings Programme. Currently up to £2,500 per kilowatt (or to £2,500/50% of total cost maximum) is available for Solar PV installations.
Systems connected to the national grid 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 occasionally by a qualified technician. For stand-alone systems, i.e. those not connected to the national grid, further maintenance is required on other system components, such as batteries.

Where can I find out more?

The DTI funded low carbon buildings programme provides grants to help with the costs of installing Solar PV technologies.
To be eligible for a grant you will need to use a certified installer and products.
Or visit the following sites:

Visit: Energy Saving Trust

Visit: Centre for Alternative Energy

Find: Local Energy Advice Centre

Look for Ourpower Pioneers in the Ourpower Community who have fitted Solar PV systems near you so you can ask and read about their experiences. Then use the Ourpower Directory to find local installers and suppliers - reading about what they can offer and what they have done, before asking a number to consider your situation and to quote. Always, get at least 2 quotes - more if possible.

To download in pdf format, click here.