SOLAR ELECTRICITY

What is Solar Electricity?

It is the generation of electricity from the power of the sun, via photovoltaic (pv) cells. It is different from solar water heating, where water passes through panels to be heated directly, and no electricity is generated.
Photovoltaic cells are made from silicon; when particles of sunlight (photons) fall on the cells, they dislodge the outer electrons of their atoms, and push them along to the next atom; a chain of moving electrons is produced, and if a wire is attached to the panels, these electrons can be pushed down it to supply a useable electric current. This current is measured in amps, and to give some idea of the scale involved, one amp of current involves the movement of 6 million million million electrons per second.
The electricity produced this way (and also from batteries) flows in one direction only, and so is called direct current, whereas electricity from the grids is alternating current, as the flow of electrons changes direction 50 times per second. Direct current can be stored in batteries to power 12 volt appliances. However, these are more expensive and less readily available than ordinary domestic 240 volt appliances, so batteries and an inverter can be used to convert the 12 volt direct current to 240 volt alternating current, or the panels can be connected to the grid, with a meter to see how much electricity is put into the grid and how much taken from it. A grid-support system is one which charges batteries, and re-directs any surplus into the grid if the batteries are full.

What are the benefits?

As a renewable source of energy, the main environmental benefits of pv is that it doesn't cause the problems that other types of electricity generation do.
Burning fossil fuels in conventional power stations releases nitric oxides, nitrogen dioxide and sulphur dioxide, causing acid rain which damages forests, wildlife and human health; it also releases carbon monoxide, nitrous oxides, lead, particulates and hydrocarbons, which cause damage to plants, ecosystems, and human health, especially respiratory problems. Also, burning fossil fuels releases 5 billion tonnes of CO₂ into the atmosphere each year. CO₂ is the most important of the ‘greenhouse gases’ responsible for global warming.
With pv there are no emissions, no environmentally-damaging extraction and transport of coal and oil to feed power stations, and no radioactive waste, or the potential leaks and disasters associated with nuclear power stations.

Disadvantages :

• Pvs take around 5 years to generate the same amount of electricity as is used in their manufacture - see this research paper (pdf) from Pennsylvania State University.
• Large-scale use of lead-acid batteries would cause environmental problems in their manufacture and disposal, so connection to the grid would be better unless in a remote location.

What can we do?

A single panel can be used with a battery to power lights or animal fencing in a remote location, or you can attempt to supply all or most of your electricity with a large system.
The first thing to do is find out how much electricity (in kilowatt-hours, kWh) you use in a year (check your bills), and think about ways to reduce your usage:

• switch lights off when you leave the room.
• don’t leave appliances on standby.
• use a laptop (c. 18 watts) instead of a desktop (c. 180 watts).
• use Savaplugs and low-energy light bulbs and appliances.
• don’t overfill kettles.
• think about solar hot water and a wood-burning stove, and whether you need so much electrical gear at all.

SAVAplugs use electronic technology to regulate the electricity to match the actual demand required by the motor. SAVAplugs simply replace the original manufactured mains electrical plug

A typical family in UK will use about 3000-4000kWh per year, but if you are single, have no children and / or reduce your electricity use, we can work with a figure of 2000kWh / year. Taking the annual amount of sunshine into consideration, this will require a 2.4kW system, covering 20m², and costing around £16,000 installed. There is now a £2500 government grant in the UK for professionally-installed, grid-connected systems (see below), which will reduce this to £13,500. With electricity at around 11p per kWh this will save £220 per year, giving a payback time of 60 years and saving about 2 tonnes of carbon. The payback time is way too long at the moment, but will come down as fossil fuel prices rise, and if the UK government start supporting photovoltaics as much as the German govt. It could be cost-effective for remote locations where the cost of grid connection is prohibitive.
The cost can’t be reduced by self-build (like solar hot water), because the manufacturing process is too high-tech, but you could self-install if you have the know-how. Of course you could use pv in conjunction with a wind turbine to take advantage of all weather conditions.

Other factors to consider are: is your roof south-facing? is it big enough? (if not, panels could be located on a frame in the garden or on a flat roof) is it shaded? (panels can be damaged if parts of them are shaded) if you are using batteries they need to be deep-cycle (able to be continuously drained and re-charged) with a charge regulator to prevent overcharging.