Photovoltaics (PV)

Solar energy can be converted into electricity using special photovoltaic (PV) cells. PV cells are used in simple applications e.g. calculators and watches, but can also be used for larger applications such as integrating them into buildings to provide all or some of the electricity requirement.

PV arrays are typically mounted on a roof facing south and angled around 30o with the horizontal. Light falling on the cells creates an electrical current that is fed via an inverter, converting 12 volt direct current into 240 volt alternating current to used in mains appliances. The panels are also connected to a two-way meter in urban areas. This allows the householder to sell the electricity to the grid when the panel is producing more energy than needed and to import energy from the grid when the panel is not producing enough electricity.

This technology is ideal to domestic buildings as it is pollution and noise-free and does not require extra space, there are many examples of PV already in the UK. PV panels are also available as roof tiles which is ideal for new buildings. PV is powered by both direct and diffused light, meaning that a system facing from south-east to south-west can work at up to 95% efficiency, but a north facing system can still operate at around 65% efficiency.

Planning permission is only required in some areas in conservation areas and for listed buildings.

The cost of a 1kWp system is around £7500 and a 2kWp system between £11000 and £13000. A 1kWp system generating around 750kWh per year and a 2kWp system generating around 1500kWh per year. A 2kWp system can provide around 50% of the average energy consumption of an average household with non electrical heating and hot water systems.

Before connecting your PV system to the electricity grid, you will need to meet the regulations of your local electricity distribution company. This varies with the installation size - if your PV system is rated at under 3.6kW for a single phase supply (or 11.2kW for a three phase supply) then you will only need to complete a G83 form that certifies that the system meets the applicable standards. These forms should be supplied by your installer or may be obtained from the local electricity distribution company. You should then have an automatic connection to the distribution network as long as you can comply with the terms set in G83. If your PV system is larger than this, you will need to contact your distribution company and negotiate directly for a connection.

You may also be eligible to earn additional payments for renewable electricity generated through the Government’s Renewables Obligation, by selling Renewable Obligation Certificates (ROCs). These ROCs are granted by the energy regulator, Ofgem, for every megawatt hour (MWh) of power generated from a renewable source. Each Certificate may be traded, and they currently have a value of around 3p per kWh, with the exact value dependent on the demand for, and availability of, renewable electricity. Some electricity companies, such as Good Energy, will aggregate renewable electricity production from their domestic customers, and pay you the value of the ROCs that they are able to sell on your behalf from this process on an annual basis. (A typical building-integrated renewable system will not generate enough electricity to earn a whole ROC in a year). There is normally a charge by the electricity company for acting as your agent in this aggregation process, and all small generators seeking ROCs must have a total generation meter approved by Ofgem. If your PV system installed is very small, it may not prove economic to claim ROCs.