‘Green electricity’ means electricity produced from renewable sources such as wind, solar and hydro. They have a much lower environmental impact than fossil fuels like coal and gas.
Of course, every type of electricity generation will have some impact, but the cleanest energy sources are those which utilise the natural energy flows of the Earth. They are collectively referred to as renewable energy sources, because they don’t use up a limited resource. And when used to generate electricity, it is called green electricity.
Green electricity makes up about 30% of all Britain’s electricity. Green tariffs supply green electricity to consumers in preference to electricity from other sources.
The winds that blow across the UK can be harnessed by turbines to provide electricity. Wind turbines provide about half of Britain’s green electricity, around 14% (2017) of all Britain’s electricity. Wind turbine technology has greatly improved over the last twenty years, making wind turbines quieter and more efficient so that electricity generated from the onshore wind is now often competitive with traditional coal-fired and nuclear power stations. Around 40% of Britain’s windpower electricity now comes from turbines sited at sea — that’s about 6% of all Britain’s electricity and in the future much of our electricity could come from offshore windfarms.
Solar photovoltaic (PV) panels work by converting sunlight directly into electricity (even on cloudy days) using semiconductor technology. They can be integrated into buildings and even made into roof tiles virtually indistinguishable from normal tiles. Solar PV contributes about 3% of Britain’s electricity supply.
Solar energy can also be used to heat water directly using specially designed collectors. Even in winter a useful amount of hot water can be produced from roof top collectors.
Water turbines have been used to provide electricity for over 100 years and presently provide over 1-2% of the Britain’s electricity. Although most of the possible sites for large hydropower stations in the UK have already been developed, there is significant potential for smaller schemes. These can either use a small dam or work as a ‘run of the river’ system which has a minimal impact on the local environment.
Britain is blessed with some of the most powerful waves in the world. Many different devices have been designed over the years to try and capture some of this huge energy resource. With the proper support, wave power could provide a significant proportion of the UK’s electricity needs in the future.
Tidal power has been used in Britain for over a thousand years — at the time of the Doomsday book over 5,000 tide powered mills were recorded. Unlike other renewable energy sources, which depend on the weather, tidal power is as predictable as the tides themselves. One way to capture tidal energy is to build a barrage across an estuary, storing water behind it as the tide rises and then releasing the stored water through turbines at low tide. Several sites around the UK could be suitable for this type of tidal system, the largest being the Severn Estuary. Another way is to use ‘marine current turbines’, which work like underwater wind turbines, harnessing tidal currents rather than the wind.
Geothermal energy comes from hot rocks deep underground. In some parts of the world steam comes to the surface and can be used to run steam turbines to produce electricity directly. In other places water can be pumped down and heated by the rocks to make steam. Geothermal energy can also be used to provide hot water and heating for buildings.
Bioenergy covers various different sources of energy derived from organic material. Together they produce about a third of Britain’s green electricity, around 9% of all Britain’s electricity.
Anaerobic digestion is a collection of processes by which micro-organisms break down biodegradable material in the absence of oxygen. The process is used for industrial or domestic purposes to manage waste or to produce fuels. Biomethane can be used to power vehicles, generate electricity or added to the national gas grid.
Agricultural wastes and specially grown plants can be used as a fuel to run small power stations. As plants grow they absorb carbon dioxide (the main gas responsible for climate change) which is then released when the plants are burnt. So using biomass does not add any extra carbon dioxide into the atmosphere. Specially grown ‘energy crops’ can provide not only an environmentally sound source of electricity, but also an important new opportunity for farmers. However, there are concerns about the sustainability of sourcing biomass from countries where forests are being cleared to make way for fast growing plants that are then used as biomass and with transporting biomass long distances.
As rubbish decomposes in the landfill sites where our household waste is dumped, it gives off methane gas. This gas can be captured and burnt in a gas turbine to produce electricity. Burning the gas does give off carbon dioxide but since methane, which is emitted from the landfill site, is a much more powerful greenhouse gas it is better to burn it than to allow the methane to escape into the atmosphere. There are already many landfill gas systems operating in the UK.
The UK generates an enormous amount of waste, and space at landfill sites is quickly running out. The best solution would be to recycle as much of the waste as possible, but instead incinerators are being constructed to burn waste. In some cases heat from the incinerator is used to generate electricity.
The number of incinerators in the UK is set to double in a decade from 2019. However many environmentalists are concerned about air pollution, including the emission of harmful dioxins from some types of waste, and the loss of a resources that could have been recycled.
Green electricity tariffs
Some electricity suppliers provide details the different types of green electricity included in their tariffs. If there are particular sources you want or don’t want, then check out the different suppliers.
 The UK will burn more than half its rubbish as it doubles the number of incinerators over next 10 years, i News, 11 January 2019