What is Solar Photovoltaic (PV)?
PV uses the sun’s energy to generate electricity. This is achieved by a chemical reaction usually using photosensitive silicon cells in a series of panels or tiles situated on a house roof. PV does not require direct sunlight – it operates on cloudy days too – just not as efficiently. Simply put, the greater the intensity of the light the greater the generation of electricity.
Why Install PV?
PV differs from most domestic renewable solutions in that it produces electricity, and electricity is a higher ‘grade’ of energy than heat. This means that it can be used for multiple applications such as powering appliances, generating light or indeed creating heat or cooling. Additionally, as electricity is ‘transportable’ it can be exported back to the grid and used to further offset overall electricity bills due to credits per kilowatt hour (kWh) paid by the electricity utility companies. The UK Government introduced ‘feed-in tariffs’ (FITs) from 1st April 2010; this is a mechanism that allows private householders to receive a premium rate from electricity utility companies for electricity that the household produces and uses as well as that which is fed back to the grid. The introduction of FITs has significantly changed the economics for Solar PV, enabling householders to achieve a significant return on investment (ROI) in the region of 6%-12% from their PV installations.
As PV installations have no moving parts, they are in most cases silent and have very few ongoing maintenance requirements, although the wiring and components of the system should be checked periodically by a qualified technician.
How does PV work?
PV systems capture energy from the sun and convert it to electricity usually using silicon cells as a semi-conducting material. The DC electrical current produced is then passed via an isolation switch to an inverter which converts it to AC current for domestic use. This AC supply is connected to the consumer unit (also known as ‘fuse board’) and appliances in the home draw the electricity in the normal way. Excess AC current (i.e the surplus energy not used in the building) is exported back the grid and this process is automated. When the sun is not shining (at night for example) electricity is drawn from the grid in the normal way.
Will it work for me?
The average house in the UK uses 3,000 – 4,000kWh of electricity per annum. A 1kWp power PV array will on average produce 800kWh per annum. A PV system requires approximately 8m2 of roof area (oriented within 90⁰ of South) for each kW of energy to be generated.
This means that for an average home in the UK, 25 – 35m2 of roof area would be required in order to generate all electricity requirements – a pretty substantial amount. Realistically therefore, most homes can expect to generate between 50% -70% of their electricity needs. However, by installing PV you will still be able to generate a significant amount of your electricity and reduce your CO2 emissions dramatically.
If you are not using the electricity being generated by your PV system (for example when you’re at work), remember that it is being exported back the grid. For most domestic PV installations, you would receive a minimum payment of 3p/kWh for electricity you export, and 43.3p/kWh for the electricity you generate and use.
As with solar thermal installations, shade from trees or nearby buildings will significantly reduce the effectiveness of the system. Also, solar panels are quite heavy and require your roof to be in a good condition. We take all of this into account via our online survey process and we request that you send us photos where relevant.