FAQ

Questions & Answers on Solar PV Systems

What are Photovoltaics?

Put simply, Photovoltaics, 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'.

What do kWp and kWh mean?

Watts are the units used to measure energy use or production and a kilowatt is a 1000 watts.

kWp stands for kilowatt peak, which is the power that a solar panel will produce if it has ideal conditions. Power specifications at 1000 W/m2 : 25C : AM 1,5

kWh stands for kilowatt hour, which is how many kW (kilowatts) are produced in one hour

Do I need planning permission for the solar panels?

From April 6th 2008, all homeowners will be able to install microgeneration 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 powercut?

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 considering a complex of factors that affect one system.A1kWp installed systemwill generate between 800kWh and 1350kWh per year depending on product, latitude, orientation, positioningangle, shading and many other.

Can I sell excess electricity?

With a grid connected system you will have ameter 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 sky is overcast. But PV cell does not need to be in direct sunlight to work, even on overcast days a PV sell 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 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 £4,000 - £6,000 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 4,500 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. Contact us so we can advise you how to save money and look after the environment.

What is the Feed-In Tariff and when is it being implemented?

A Feed-In Tariff (FIT) is a Government incentive scheme to encourage Micro-generation installations. FIT is apayment made for every kilowatt-hour kWh of renewable electricity you generate. Electricity utility companies are obliged to buy renewable electricity at fixed above-market rates set by the Government. The UK Government is bringing in The Feed-In Tariff in April 2010 . This will reduce installation payback times considerably and also guarantee rates for 25 years.

What is the Renewables Obligation (RO)?

The RO is the main support scheme for renewable electricity projects in the UK. It places an obligation on UK suppliers of electricity to source an increasing proportion of their electricity from renewable sources.

A Renewables Obligation Certificate (ROC) is a green certificate issued to an accredited generator for eligible renewable electricity generated within the United Kingdom and supplied to customers within the United Kingdom by a licensed electricity supplier. One ROC is issued for each megawatt hour (MWh) of eligible renewable output generated.

The Renewables Obligation, the Renewables Obligation Scotland and the Northern Ireland Renewables Obligation are designed to incentivise renewable generation into the electricity generation market. These schemes were introduced by the Department of Trade and Industry, the Scottish Executive and the Department of Enterprise, Trade and Investment respectively and are administered by the Gas and Electricity Markets Authority (whose day to day functions are performed by Ofgem).

The Renewables Obligation Order came into effect in April 2002, as did the Renewables Obligation Order (Scotland). The Renewables Obligation (Northern Ireland) Order came into effect in April 2005. These Orders have been and are subject to regular review.

The Orders place an obligation on licensed electricity suppliers in England and Wales, Scotland and Northern Ireland to source an increasing proportion of electricity from renewable sources. In 2005-06 it was 5.5 per cent (2.5 per cent in Northern Ireland). In 2006-07 the obligation is set at 6.7 per cent (2.6 per cent in Northern Ireland).

Suppliers meet their obligations by presenting sufficient Renewables Obligation Certificates (ROCs). Where suppliers do not have sufficient ROCs to meet their obligations, they must pay an equivalent amount into a fund, the proceeds of which are paid back on a pro-rated basis to those suppliers that have presented ROCs. The Government intends that suppliers will be subject to a renewables obligation until 31 March 2027.