We flip on a light, plug in a device, flick on a gas cooker to make dinner, and never consider how the energy needed for those activities has reached our sockets and switches.
Most of us don’t know how the electricity our computer needs to run has been transformed from coal or wind or how the gas our boiler uses to heat our homes has been pumped from the ground and piped into our homes.
Your energy takes a long journey to your plug and your hob and it starts from wind turbines churning off the coast, from gas wells thousands of feet beneath the North Sea, from nuclear reactors, even from fields of cow manure. The UK harnesses a variety of natural resources, from fossil fuels to the rays of the sun, to power our grid: this is our energy mix.
UK’s Energy Mix
At any given time the UK national grid is it up with power from coal, gas, nuclear, solar, water, and wind energies. You can see a live estimates of the breakdown on the National Grid Status website. In the last quarter of 2017, 8% of the UK’s energy came from coal (a steep decline from the 25% to 40% that was standard even just a few years ago and reflecting concerns about the role of burning coal for fuel in pollution and climate change), 35.5% came from gas, 15% was nuclear, 18% came from wind and solar sources, 6.5% was from bio-energy, and the rest from various smaller sources.
The exact energy mix that reaches your home will be different depending on your provider. Your supplier should provide this information on their website or you can consult this list of the fuel mix of the UK’s main domestic electricity suppliers. If you use ‘green’ energy supplier like Bulb, Ecotricity, or Good Energy, 100% of your energy will be from renewable sources, including solar, wind, and even wave power.
But how does a breeze or a lump of coal become power that can be used to charge devices and switch on your TV? Let’s take a look at how electricity is generated from the main fuels in the UK energy mix.
From Fuel to Electricity
Coal: Coal is a fossil fuel extracted from the earth by mining. The UK has extensive coal reserves and used to mine millions of tonnes every year but extractions have fallen steeply since the 1960s and Britain now imports more coal (primarily from Russia, Columbia, and the United States) from than it produces.
To generate energy, pulverised ‘thermal coal’ is burned, creating heat that turns water into steam. At high pressure that steam is used to turn a turbine connected to an electrical generator. This takes place at coal-fired power stations throughout the UK: they’re recognisable by their huge cooling towers, which have replaced ‘smoke stacks’ on older, mostly decommissioned power stations.
Gas: Natural gas is another fossil fuel extracted from the earth, via drilling, pumping, or, controversially, fracking. Half of the UK’s gas comes from offshore drilling in gas fields in the North Sea and the rest of it is imported, reaching our shores via pipelines from Europe or on tankers in the form of Liquefied Natural Gas (LNG).
Natural gas is converted into electricity in several ways: by being burned to create steam that powers turbines (similar to how coal becomes electricity) or in a gas turbine, which is effectively a huge combustion engine where heated gas causes turbine blades to spin. Combined cycle gas turbines combine the two processes
Nuclear: In nuclear power plants, the heat released during nuclear reactions powers steam turbines which generate electricity. The UK currently has seven nuclear power plants with fifteen reactors, although more than half our nuclear capacity is scheduled to be retired by 2025.
Wind: Wind power is generated when airflow turns turbines which mechanically power generators. With large stretched of coastline and ocean and brisk winds, the UK is one of the world’s leading generators of wind power. Most of our wind farms are offshore: the largest by megawatt capacity is the London Array, with 175 turbines in the Thames Estuary.
Solar: When a sun beam hits a solar panel, photons of light excite electrons in the panel’s silicon cells, producing electricity. The UK isn’t exactly known for its sun-drenched seasons but many people have installed solar panels on their homes business and, using feed-in electricity tariffs, generate power for their own use and to sell back to the grid.
From the Power Station to Your Home
So we know how the main fuels are harnessed to generate electricity but how does that power then travel from the power station or wind farm to your home?
Electricity journeys to your home through the wires and cables of the National Grid—but takes a few transformations and turns along the way. The wires and cables of the National Grid cross large distances between cities in the air, suspended on pylons or poles. Nearer settlements, they are often buried for safety.
As it travels along wires, electricity loses some energy through heat. The higher the current the more heat is lost so the National Grid transports electricity at a low current, which means a high voltage. Power stations produce electricity at 25,000 V—much lower than the 400,000V, 275,000V or 132,000V used by the National Grid—so the electricity is ‘stepped up’ via transformers at the power station and then “stepped down” again at substations for use in train stations, factories, and homes—for the last one, at a gentle 230 V that won’t fry your appliances.
Most UK homes use two different types of energy: electricity and natural gas. Natural gas, as we read above, is used to generate electricity but is also delivered to your home for use in cookers and to power boilers. The National Transmission System starts with terminals on the coast that receive and process gas extracted through offshore drilling and then transmits it through a series of pipelines to power stations that turn it into electricity and gas distribution companies that serve households and businesses. Altogether the UK has a staggering 169,000 miles of gas pipes, 2,600 miles of which is repaired or replaced every year—the equivalent of fixing or repaving the entire UK motorway system