Questions & Answers about Solar Electricity Systems

What are Photovoltaic’s?
Put simply, Photovoltaic’s, or PV, are electrical devices that convert light into DC electricity. The light can be from any source. As long as the light is the right colour (white light is all colours) some electricity will be produced from a solar cell. The more intense the light, the more electricity is produced. Each cell produces only a small amount of power, but when the cells are strung together in series to make solar modules they become more useful. A solar module can then be installed with other modules to form an array. The total energy output can be quite substantial.

How does a solar cell work?
A solar cell is a semiconductor diode that when stimulated with light, produces an electron and a positive charge on opposite sides of the cell. Wires collect the charge off each side of the cell and take this electricity to the load circuit, such as a light bulb. Wiring cells in series increases the voltage, and in parallel increases the current output. For the cells to be useful, they must be put together in a system with other components sometimes called a 'photovoltaic system' or a 'solar energy system' or a 'solar electric system' or a 'solar pv system'.

Do I need planning permission for the solar panels?
From April 6th 2008, all homeowners will be able to install micro generation equipment, like solar panels, without needing to get planning permission, as long as there is clearly no impact on others.

Can I power my whole building from a PV system?
With an 'off grid' system it would not be cost effective to power air conditioning, heat pumps, immersion heaters, electric boilers, electric cookers and electric room heaters as they draw a massive amount of electricity and would cost a fortune to run. But, when a PV system is 'Grid-Connected', under normal operating conditions, generally all the house loads are met by a combination of the PV system and the utility grid in the daytime. Although, sometimes these loads can be totally met by the PV system in the daytime and met by the utility grid at night.

Will a PV system heat my hot water?
No. Using PV to generate heat is extremely inefficient and uneconomical. You should use a solar thermal system to heat hot water.

Will my system have batteries?
Usually only if the system is 'Off-Grid'. Batteries will be essential for the storage of electricity so you can use electrical equipment when there is no sunlight. Grid Connected PV systems don't need batteries, however, you can have batteries with a grid connected installation if you wish to have power during power cuts, you need to determine this before the installation.Grid Connected PV systems usually don't have batteries so are simpler to install and have less hardware that could potentially fail. Because they are less expensive this makes them more cost effective. Whether you have a Grid Connected PV system with or without batteries, excess electricity produced by the solar panels will be directed back to the national grid. You will receive money back for any power that you 'sell' to the utility company.

What happens during a power cut?
With a grid connected solar PV system, the inverter will automatically disconnect itself from the utility grid when there is a power cut. This is to prevent back feeding the grid and putting engineers working to restore power in danger. But, if you have a grid connected PV system with battery back up it will automatically switch to backup power with little detection. Both these systems will automatically hook back up to grid once power is restored.

How much electricity will a PV system generate?
The amount of electricity that is generated will be estimated by our solar photovoltaic software and varies from system to system. We will be able to predict what the system will be capable of.

Can I sell excess electricity?
With a grid connected system you will have an inverter that imports and exports electricity as you need it. When you export electricity you will get paid for it.

Doesn't PV need bright sunshine to work?
PV cells will generate more electricity on bright days than when skies are overcast. But PV's do not need to be in direct sunlight to work, even on overcast days a PV cell will be generating some electricity.

How long will a system last?
The average lifetime of a PV module is in excess of 25 - 30 years; crystalline silicon modules in particular have a very long life span. In addition, they require very little maintenance. Other system components like the batteries for off-grid system should last 10 - 15 years if you buy a good brand.

How much will a Photovoltaic system cost?
As a guideline, for grid connected PV you will be looking at around £5,000 per kWp installed.

How much will I need to power my home?
The size of your system will depend on your location and power requirements both in AC and DC. According to the Energy Saving Trust, the average 3 bedroom house consumes 3,300 units of electricity (kWh) a year excluding cooking and heating. To find out how much electricity you use, call your electricity supplier or check your bills. You can then compare your consumption to the output of the system we size for you. By doing this you'll get a good idea how much you will save.

Why install a PV system?

There are many reasons to install a PV system:

• Fixed power costs for 30 years
• It is the most practical and economically viable option for many applications in remote areas.
• It is completely pollution free.
• Reduce the Carbon Tax for your home or office
• PV can be used instead of a roof covering
• Electricity can be supplied at the point of use.
• The system runs silently.
• There is very little maintenance required for a PV system.
• After the initial installation costs, there are no further fuel costs.
• PV systems are modular, and can be added to at any time.