Solar PV – Frequently Asked Questions

What does PV mean?
PV stands for photovoltaic which comes from Latin: photo (meaning light) + voltaic (meaning energy).

How does a solar photovoltaic system work?
Photovoltaic (PV) panels convert solar radiation (sunlight) into electricity. A typical PV panel consists of multiple mono-crystalline or poly-crystalline cells, which in turn consist of a wafer of semi-conducting material, usually silicon, manufactured with two electronically different layers. When the solar radiation hits the cell it excites the electrons in the silicon, creating an electric field and causing a flow of electricity. An inverter is required which turns the electricity generated by the panels from DC (direct current) to AC (alternating current) which is useable in the home.

What is the difference between solar thermal and solar photovoltaics (PV)?
Solar photovoltaics (PV) technology is using the power of the sun to produce electricity. Solar thermal technology is using the power of the sun to heat water. Both systems can be incorporated upon a single roof space.

What is the difference between mono-crystalline and poly-crystalline solar PV panels?
A PV panel is made up of multiple cells and these cells are either mono-crystalline or poly-crystalline. Mono-crystalline cells are made from a single large crystal and have a higher output per kW rating but tend to be more expensive. Poly-crystalline cells are made of blocks of silicon which contain many smaller crystals. They are slightly less efficient than mono-crystalline panels, but are cheaper. Mono-crystalline panels are black and poly-crystalline panels have a dark blue colour. In practice, for a typical residential property, there is very little difference in performance.

What is shading and how does it affect solar PV performance?
Shading is anything such as trees, overhead wires or neighbouring buildings that cast a shadow upon the solar PV panels. Shading can have a large effect upon the performance of solar PV systems as each PV cell is interconnected. If one cell is shaded it has a knock on effect that prohibits the whole panels from generating electricity. To work effectively the whole PV system needs to be free from shade for the majority of the day.

How long will the installation of solar PV panels take?
Typically a solar PV installation will take 1-2 days to install, however all WDS Green Energy systems are bespoke designs and, especially if installing in conjunction with a heat pump or solar thermal system, could take a little longer.

Where can I place solar PV panels?
Solar PV systems can be mounted in a range of locations, the simplest and easiest being the roof of a building. Solar PV panels can also easily be installed on frames on your land, or upon outbuildings with suitable roofs. Flat roofs whilst not ideal are also suitable for PV installations utilising the same type of frames as installations set upon the ground. The only restrictions are thatched roofs which cannot house PV panels.

How much roof space do I need for a solar PV installation?
PV systems are modular allowing a great degree of flexibility in design and specification. In practice this means that the size of the system is usually deemed by the available roof space, or the energy requirements of the property. 1kW of PV panels will take up approximately 8m2 of roof space and typical systems are between 2.5kW and 4kW.

Does my roof have to face south?
A south facing roof is the ideal for a solar photovoltaic (PV) system for optimum performance however anything between south east and south west also performs well and will generate ample electricity for your home.

Do I need planning permission for a solar photovoltaic installation?
Generally no, solar PV installations fall under permitted development, however if your property is a listed building or in a conservation area you may need planning permission.

Do solar PV panels still produce electricity in cloudy weather? Or at night?
Solar PV panels require solar radiation (sunlight) to work so they do still work on cloudy or overcast days. Unfortunately the stellar and lunar radiation (starlight and moonlight) are not strong enough so solar panels do not work at night. During the night any electricity your property needs will come from the national grid.

Are there grants and incentives available for solar PV?
Solar Photovoltaic systems are eligible for feed in tariffs (FiTs), which is a Government scheme which pays per unit of electricity generated regardless of whether it is then used in the property or exported back to the national grid. You will need to use an MCS accredited installer, such as WDS Green Energy Ltd, to be able to claim the feed in tariffs.

What happens if I move house?
If you have solar PV panels installed and are claiming the feed in tariff (FiTs) and you decide to move home then you need to inform your FiTs provider who will transfer the tariff over to the new owners.

What maintenance will my solar PV installation require?
Solar panels are very robust and can withstand the normal stresses subjected by nature such as wind and snowfall, as such they have little to no maintenance requirements although WDS Green Energy.

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