Solar photovoltaic – or PV – is probably one of the most familiar types of renewable energy technology, generating electricity from light which can either be stored in batteries or fed into the national grid.
As a result, although PV solar panel systems are often seen as an ideal way for getting an electrical supply to remote places where a grid connection might be difficult or expensive, their use is not restricted to out of the way locations. Indeed, in some respects, PV comes into its own as an addition to existing conventional electrical arrangements.
How Does It Work?
PV solar panels consist of a collection of photo-electric cells, made up from one or two semi-conductor layers – typically silicon. When light shines on the solar panel, an electric field is formed across these layers – and the electricity flows.
One of the great attractions of this form of renewable energy is that it works on daylight – not direct sunlight like solar water heating – so it allows solar energy to be harnessed even when the sky is overcast. However, the more light, the greater the electrical generation, so obviously it does work best when the sun shines for hours at a time!
For an installation which does not have a grid connection, it will be necessary to use batteries to store the power generated for use when there is little light or at night. The solar panels charge the batteries during the day and then they provide a source of renewable energy when the panels themselves cannot.
Lead-acid batteries are the most common in PV systems; although normal car batteries can be used in this role, there are more suitable types, so it’s worth getting some expert help to make sure you get the right kind.
Alternatively, if you opt for a suitable grid-connected installation, the electricity can be sold to your utility company. With this kind of system, during the hours of daylight, when your solar panels are busily producing, the electricity is used to meet household needs first, with any excess renewable energy being supplied to the grid – for which you get paid.
Grid connected PV generally needs less maintenance than an off-grid approach and is normally simpler to run. If you do choose to go down this route, you might also want to think about partnering your PV array with wind-power for those shorter winter days.
Economics of PV Renewable Energy
Unfortunately, installing PV systems tends to work out more expensive than many other forms of renewable energy, with a typical grid-connected installation costing between £5,000 to £8,000 per kW – which makes pay-back times long.
Never-the-less, PV still has some advantages. Although installing a PV solar energy unit costs more than a similar output wind turbine for example, PV is better suited to a greater number of locations and the solar panels will require less in the way of ongoing maintenance.
The exact price of a PV system depends on a number of factors, including the amount of electricity it is intended to produce, the type of solar panels used and the ease of installation. Modern solar panels come is a surprising range of designs, with solar roofing tiles costing more than the traditional types – and integrated panels being more expensive than those simply added on top of an existing roof.
According to the Centre for Alternative Technology a 1kW PV array – covering an area of between 8 and 20 square metres – on a south-facing roof should generate around 750kW hours of electricity a year.
However, it is from the point of view of environmental economics that PV really scores. World Energy Council studies suggest that the life-cycle carbon cost of 1kWh of renewable energy electricity from PV amounts to between 0.01 and 0.1 kg of CO2.
By comparison, the equivalent figures for gas-fired power are around 0.5 kg of carbon dioxide per kWh and between 0.8 and 1.4 kg for coal-fired power stations. As a result, according to the UK Department of Business Enterprise and Regulatory Reform – the DTI’s successor – a typical domestic PV installation will save an annual total of over 1 tonne of CO2 emissions – equating to around 30 tonnes over its lifetime.
Although solar photovoltaic electricity installations are not the cheapest option for renewable energy projects, there is no denying that the promise of solar energy is an alluring one and from a green standpoint, there are few better ways to generate electricity.