Solar Photovoltaic (PV) panels generate electricity from sunlight. They are commonly mounted to the roof and produce free, green energy for your home or business. If you have a battery, excess PV energy can be stored for use later in the day.
Modern solar panels produce electricity from daylight and do not require direct sunlight, although more electricity is produced on bright, sunny days. Shading is still a problem, so an over-shading calculation will be performed on site before the estimating stage. Some PV cells have multiple internal junctions, to allow a branch to cast a shadow onto part of the panel, without compromising the output of the whole panel.
PV power output in the UK is typically 5 times greater in June than in December. We do not yet have batteries that are cheap enough to store energy between seasons, so PV is unlikely to completely cover a home's heating, but it can make a significant contribution to the daytime running costs.
PV can be mounted to rails on top of the roof. This helps to ensure that the array is free of shade and has good airflow over it. They can also be embedded into the roof structure, in a plastic tray. Roof integrated solar is now cheaper than slates and typically generates over £1000 per year in savings, although care must be taken to avoid the plastic degrading in the sunshine.
The PV panels produce DC electricity which needs to be converted into AC electricity by way of an inverter. Once converted, this energy can then be used to power appliances in your home or exported back into the National Grid. It is more cost effective to size an array for home demand than for export, because export rates (the amount you get paid for selling electricity back to the grid) are much lower than import rates (the amount you pay for the electricity you import).
Solar PV in the UK is relatively low maintenance. They may occasionally need to be washed clean of dust, to ensure they continue to operate effectively. PV located in the desert has to be cleaned much more often than PV on top of a hill in Wales, although bird droppings can still make a noticeable difference!
The electrical switchgear should also have a regular inspection schedule.
Usually PV falls under permitted development, so planning permission is not required, but for conservation areas and listed buildings, contact your local council planning office to check.
A team of 2 people will normally be able to complete a single roof installation in 1 -2 days. It may require scaffolding if your home is over 2 storeys or has complex extensions or inaccessible rear gardens.
Things to ask an installer:
Post install service contracts
Anti modern slavery checks.
Things to avoid: Micro inverters mounted behind PV, due to their reliability
Work to consider at the same time: Removing any redundant chimneys while the scaffolding is up, for added benefits to air quality, heat loss and to free up more roof space for PV!