Introduction to Solar PV
Solar panels which generate electricity (known as solar PV) capture the sun’s energy using photovoltaic cells. Even on a cloudy day, the cells can still generate electricity which can be used to run household appliances and lighting.
How does solar PV work?
- solar PV systems use cells, consisting of one or two layers of semi-conducting material (generally silicon), to convert solar radiation into electricity. Light shines on the cell creating an electric field across the layers which causes electrons to flow creating electricity
- an inverter converts the direct current (DC) to alternating current (AC – or mains equivalent) electricity which is suitable for running appliances
- grid connected systems can export electricity they don’t use to the grid, and import it from the grid when there is not enough energy being generated by the system to power appliances
- some systems store excess electricity in a battery.
The advantages of Solar Electricity
- reduce your carbon footprint
- reduce energy bills
- be more self sufficient
- some financial return
Is Solar right for my home?
The ideal situation for solar panels is facing due south, although they are effective facing anywhere between south east and south west, and they should be free of shade. For best performance they should be angled at 30 to 40 degrees – although you will still catch a reasonable level of sunlight at angles of 20 – 50 degrees.
How shade affects performance
Shade falling on the roof will reduce the performance. How much it affects it by depends on type of shading: close structures such as gable windows or chimney stacks can reduce output significantly as they will tend to throw shade on the panels for most of the day.
Further away objects such as trees or a neighbouring house may not block the sun during summer but create shade when the sun is lower in the sky in winter. Having your PV panels linked to a series of microinverters (rather than a single inverter) can help address any issues with shading or where you have an array of solar panels with differing orientations.
Solar panels weight
Solar panels weigh quite a bit, so your roof must be strong enough to hold them. If you need to re-roof, you can do so using solar tiles.
These are more expensive than retrofitting panels, but if you are re-roofing anyway it can be more cost-effective to re-roof with solar tiles than to use conventional tiles and put panels on top. Alternatively, panels might be mounted on a frame on the ground or a flat roof.
Size of the system
The size of the system installed depends on how many panels you can fit on your roof. A 3.5kWp system requires about 20m2 of roof space. Panels come in different sizes and the power of a panel is measured in watts. More than one panel makes up an array. Typically, a domestic property will have an array of up to 4kWp installed.
Get the most from your solar PV system
To get the best out of your solar PV system you want to use as much of the electricity it produces as possible. This is because the price you get for exporting the electricity generated is less than the cost of buying in electricity from the grid.
Use appliances when the sun is shining and the modules are generating. While you must be present for some of these, you can put others on timer to run when the sun is forecast to be out and you’re at work.
Heat your water with solar
Another popular method is to divert excess solar electricity to your immersion to heat your water. This is something you can do manually if you are at home and watching the meter. Alternatively, you can buy a solar switch device to do this for you automatically.
The simplest way of knowing whether you’re generating electricity is to look at your generation meter, or you can look out of the window and see if the sun is shining.
Costs of solar PV
The Energy Saving Trust reports that a 3.5kWp (3,500w) solar PV system will cost about £4,000 – £5,000.
You can use the solar PV calculator on the Energy Saving Trust’s website to calculate how much electricity a system might generate for you.
Solar PV planning permission
Permitted development regulations
The installation of solar PV system on residential properties is likely to be classed as ‘permitted development’, meaning there is no need to apply to the local planning department for planning permission however, there are certain exemptions.
You should contact your local planning department to check conditions will be met.
Installation for solar PV
Solar PV systems are easy to install, need virtually no maintenance and are estimated to last 25 years.
With no moving parts, there is little to go wrong.
You may need to replace the inverter within the lifetime of the system.
Battery for Solar PV
The ultimate way of using more of your own electricity is to keep hold of it in a battery. A battery can store the solar energy that’s generated but not used at the time, so you can use it later on when your system isn’t generating
Read more about batteries here.
Solar PV and batteries can also be used with electric vehicles. Read more about electric vehicles here.
An installer may try to sell you other devices with your solar PV system like voltage optimisers which are meant to reduce the voltage used in your home and reduce your energy bills. Or a device to divert surplus energy from your PV system to heat water in your hot water tank (if you have one), instead of exporting it to the grid. You should do your research on the benefits of these devices before purchasing.
Smart Export Guarantee
The Smart Export Guarantee (SEG) means you can get paid for the surplus energy your solar PV system generates and exports back to the grid. You should shop around for the best SEG tariff.
