Photovoltaic (PV) cells generate and store electricity directly from the sun"s energy to operate appliances and lighting within the home. Through the use of rechargeable modules electricity is generated by daylight, not direct sunlight so that power can be created on a cloudy day, whilst emitting no greenhouse gases.
Solar PV cells can be organized in panels on a building’s roof or walls and with the most modern PV technology, cells can also be incorporated into the roof tiles themselves. There are many PV technologies available including polycrystalline, monocrystalline and thin-film. Grouping solar PV cells can increase the levels of power for use in domestic households.
There are many small scale PV powered systems functioning in the UK, ranging from street lights, road signs and phone booths to battery charging on boats, motor-homes and in garden applications such as lighting.
How it works
The Photovoltaic system is made up of cells, each consisting of one to two layers of semi-conducting material. This is usually silicon and as the light glistens on each cell, an electrical field is created across the layers. The cells convert daylight into electricity, and the stronger the intensity of the light, the more electricity is produced.
The amount of energy produced by a PV cell is measured in kilowatt peak or kWp, which quantifies the level of energy the cell creates when there is full sunlight. Each module creates energy, which can be bound together to get a total amount, so 10 PV modules produces 225 watts, hence creating a system size of a 2.25kWp and approximately 750kWp can be generated a year.
There are two different types of PV systems available:
- Stand-Alone or Retro-Fit modules
- Building Integrated PV (BIPV)
The stand-alone modules are positioned on a flat and pitched roof. They are mounted to complement any roof coverings such as tiles or concrete, and are the most common PV cells used.
The Building Integrated PV (BIPV) integrates with the roof tops and form part of the fabric of a building. Examples of these are the C21e modules which replace tiles on a roof, solar cladding and solar louvres.
PV cells can be purchased in many shapes and colours so that they blend into your house. Grey "solar tiles" look like roof tiles and there are panels and transparent cells available to use on conservatories and glass.
From the solar cells Direct Current (DC) electricity is produced from daylight, which need to be converted into Alternating Current (AC). For this an Inverter is required so that the sun’s energy can be used in the home or building.
Benefits
- Solar electricity has no carbon emissions as it is green and is a renewable energy. A typical home can save around 1200 kg of carbon dioxide per year and approximately 30 tonnes over its lifetime.
- There is a wide range of installation options so can be applied to a wide range of roofs.
- Grants are also available to cut costs.
- Sunlight is free so after initial costs electricity bills would be greatly reduced.
- Minimal maintenance is required and there are no moving parts.
- Leftover electricity generated can either be stored or sold to the National Grid.
Installation and where it can be used
The system is relatively easy to install; however, there are many factors to consider such as aspect, weather, shade and tilt.
Planning permission is generally not required.