Contact Chelsfield Solar and Chelsfield Electrical for solar electrical installations

Solar Electricity - The Basics

Electricity generated from solar PV systems can either be connected to your normal mains supply, which is what we do, or the electricity can be stored in batteries if you do not have a mains supply.

Chelsfield Solar install grid-connected solar electric systems for domestic, commercial and community projects. We will advise on the best solution, provide a fully inclusive quote and help with obtaining the government solar grant.

With a grid connected solar PV system, the solar generated electricity is used at the time of generation first by any electrical appliances that require electricity at that time. If the PV system is generating more electricity than your property requires then the excess is automatically exported to the National Grid. If the PV system is not producing enough electricity to cover your usage then any additional is pulled from the National Grid in the normal way.

With grid connected solar PV there is no maintenance or batteries to worry about and all the equipment is tried and trusted with extensive guarantees. Solar PV produces electricity without producing carbon dioxide in the process, which is the main global warming gas that is produced by current coal and gas generated electricity. The UK government's aim is to drastically reduce carbon dioxide emissions and as electricity accounts for at least 25% of these emissions from UK homes, Solar PV for your own building is the one largest differences you can make.

There is more solar information on the Solar FAQS page.

Benefits of Solar Electricity

Your own clean power source to help combat Global Warming
Huge reduction in carbon dioxide emissions
Lower electricity bills - energy from the Sun is free
Inflation-proof electricity
Increased value of your property
Renewable technology ideally suited to the urban environment

Output of a solar PV system

Solar PV generation

This graph shows the output of a 6 panel 'Hybrid' system for the individual months through 2005 and 2006 - see the bottom of this page for an overview of the main types of technology.

A PV system will generate more electricity through the summer months as the days are longer. The system that the graph is based on is using 6 x 190W Hybrid panels and the higher the output of each panel the more electricity you will generate.

The amount of electricity that can be generated will depend largely on the weather. Therefore, you do need to look at the output over a longer period of time, for example, an annual basis.

How a Solar Cell Works

Solar PV cell A solar PV module (sometimes called a panel) consists of a number of photovoltaic cells joined together to create a module - this is the basic building block of a solar PV system.

A number of modules are connected together to create an array and the size of the array makes up the kWp (kilowatt peak) size that can be fitted on your roof. This kWp dictates the output of the system under Standard Test Conditions. The various module technologies have different expected annual outputs in the UK - see below for an overview of the most common solar PV technologies.

Put simply, when exposed to light the cells generate electrical energy (DC current) which is conducted away to an inverter to create mains electricity (AC current). This can then be used in and around your property at the time your array is generating it.

PV cells are manufactured from silicon, a semi conducting material, which is also found in many modern devices such as PCs and TVs. PV cells are either classified as a form of crystalline, thin film or a combination of these two technologies, as highlighted below. It is the combined form of cells that produce the most efficient solar PV module commercially available.

Main Types of Solar PV

Solar PV systems are sized in kWp (kilowatt peak), which is a measure of their maximum output in Standard Test Conditions. However, in the UK, we don't see much in the way of ideal conditions and so a system needs to be considered in terms of its electrical output. This output is measured in kWh (kilowatt hours), which is the same measurement as the electrical units shown on an electricity bill. Different technologies give different outputs per kWp and as a general rule:

Technology	Characteristics	Appearance
Polycrystalline ('multicrystalline' or 'thickfilm')	Similar to mono-crystalline (below) but slightly less efficient. Power output c720 units/kWp/year Power density = 120 Wp/m2	Shiny and spangly blue or a darker blue
Monocrystalline	This is the most efficient technology in high light conditions but performance drops away in low light conditions. Power output c780 units/kWp/year Power density = 120 Wp/m2	Charcoal or dark blue
Amorphous ('thinflim')	This is very efficient in low light or cloudy conditions. However, you do need a large area per kWp. Power output c930 units/kWp/year Power density = 62 Wp/m2	Dark brown or dark blue
Hybrid	The most efficient in the UK and works well in high light as well as low-light conditions - it is a combination of mono-crystalline and thin-film technologies. Power output c930 units/kWp/year Power density = 156 Wp/m2	Charcoal

For clarity:

Polycrystalline gives around 700-750kWh per kWp
Monocrystalline gives around 750-800kWh per kWp
Thin-film gives up to 930kWh per kWp
Hybrid gives around 930kWh per kWp

We would advise you of the best technology for your property once we have details of your specific project.

Solar Roof Tiles C21 installation

If you are building a new home or re-roofing your property you may want to consider using the new Solarcentury solar roof tiles (known as “C21e”) rather than conventional roof tiles. Each C21e tile replaces four conventional roof tiles and is attached straight to the roof battens. The C21e tiles integrate with a range of modern concrete interlocking tiles. For more information see:http://www.solarcentury.co.uk/products/solar_photovoltaics/c21e_solar_electric_roof_tile_black.

We would provide information to your roofers regarding the roof preparation work they would need to do. We would then design, supply and install the C21e system at the appropriate stage of the build programme.

C21e photo courtesy of solarcentury.