Sunlight is a renewable energy source. Solar panels convert sunlight into usable energy.
Solar panels turn energy from the sun’s rays directly into useful energy that can be used in homes and businesses. There are two main types: solar thermal and photovoltaic (or PV.)
Solar thermal panels use the sun’s energy to heat water that can be used in washing and heating. PV panels use the photovoltaic effect to turn the sun’s energy directly into electricity, which can supplement or replace a building’s usual supply.
A PV panel is made up of a semiconducting material – usually silicon-based – sandwiched between two electrical contacts. To generate as much electricity as possible, PV panels need to spend their time in direct sunlight (1a). A sloping, south-facing roof is the ideal place to mount a solar panel.
A sheet of glass (1b) protects the semiconductor sandwich from hail, grit blown by the wind, and wildlife. The semiconductor is also coated in an antireflective substance (1c), which makes sure that it absorbs the sunlight it needs instead of scattering it uselessly away.
When sunlight strikes the panel and is absorbed, it knocks loose electrons from some of the atoms that make up the semiconductor (1d). The semiconductor is positively charged on one side and negatively charged on the other side, which encourages all these loose electrons to travel in the same direction, creating an electric current. The contacts (1e and 1f) capture this current (1g) in an electrical circuit.
The electricity PV panels (2) generate is direct current (DC). Before it can be used in homes and businesses, it has to be changed into alternating current (AC) electricity using an inverter (3). The inverted current then travels from the inverter to the building’s fuse box (4) and from there to the appliances that need it.
PV systems installed in homes and businesses can include a dedicated metering box (5) that measures how much electricity the panels are generating. In the UK, as an incentive to generate renewable energy, suppliers pay the owner a fixed rate for each unit of electricity it generates – plus an additional amount for units the owner doesn’t use, because these can supply the national grid.
Installing a PV system is not cheap, but this deal can help the owner earn back the cost more quickly – and potentially earn a profit. If a household or business installs solar panels, suppliers can reward them through the Feed-in Tariffs (FiT) set up by the Government to encourage householders and business owners to produce low-carbon electricity. If consumers want to support a range of renewable energy sources, they can choose a green tariff.
Solar power is a renewable and almost inexhaustible energy source and can be considered a secure source because it does not need to be imported – but the amount of energy that can be harnessed to generate electricity is limited by current technology and the UK climate.
In countries with much intense sunlight, PV panels can be a cost-effective way to generate electricity as solar panels are most effective in direct sunlight. The UK's latitude and cloud cover reduce their effectiveness. UK peak electricity demand also tends to be in early evening and in winter, but the electrical output from solar PV systems tends to peak around midday and in the summer.
The carbon footprint of solar PV is small and shrinking, as the materials used in PV panels are increasingly being recycled. Solar capacity in the UK is growing at a significant rate. However, given its relatively low load factor, its contribution to total UK generation is relatively small (about 1% in 2014).