How is electricity generated?
As we head towards a greener future, how we generate electricity is changing.
However, it’s important to have different fuel sources and technologies to generate electricity to ensure a constant supply and not be overly reliant on one type of power generation.
Notably, the shift from carbon-emitting fossil fuels, a reliance that was prevalent just a few decades ago, is now being replaced as we progress from coal to clean, marking a significant step towards a more sustainable future.
Renewables are key to all of this. And it’s great news that in 2023, coal was responsible for just 1% of electricity generation, down from 5.1% in 2018, and 39.6% in 2013.
To understand the process of electricity generation, we examine all sources – from nuclear and hydrogen, to solar and imports. We also lift the lid on electricity storage and its critical role in this energy transition.
In this section, you'll learn even more about generating electricity.
How is electricity generated using hydrogen?
Hydrogen can be produced from a variety of resources, such as natural gas, nuclear power, biogas and renewable power like solar and wind.
For some time now, we have used natural gas for these purposes - power stations have used gas to generate electricity. In fact, most of our homes, and around 40% of the UK’s total electricity generation, rely on gas.
Natural gas works in that it’s cost efficient, is a readily available resource, and a cleaner alternative to coal. But not as clean as some alternatives – when it’s burnt, it creates the waste product carbon dioxide which contributes to climate change.
When we burn hydrogen however, the only by product is water vapour, making it a potentially cleaner alternative to support our ambition of running a zero carbon grid by 2025, and Great Britain’s longer-term net zero 2050 goals.
Storage and transportation
Hydrogen is interesting because it has the potential to be stored for long periods. Currently battery storage is only a short-term option. There’s also the benefit of being able to transport it along existing infrastructure, though this is also not without its challenges.
“Hydrogen has the potential to act as a storage medium for times when you have excess generation from renewables, such as wind,” said Robert Gibson, Strategy Manager. “It would be produced via electrolysis, stored - potentially in large volumes for extended periods of time - and then when there is a requirement for additional electricity, the hydrogen could be used in a hydrogen-powered power station.”
Electrolysis can also offer flexibility to the network when it becomes congested during peak periods of generation by renewables.
“Electricity can be converted to hydrogen if there’s network congestion and then either transported to be used elsewhere in the country or stored until needed at a later date,” explains Robert. “You could even leverage existing natural gas infrastructure and pipe it straight to homes and businesses.
“There are potential cost efficiencies in converting hydrogen directly at electricity generation points. Studies across Europe are looking at doing this for offshore wind. Floating wind turbines way out at sea need cabling, and it’s expensive to bring the electricity on shore. It’s potentially cheaper to bring the energy onshore as hydrogen. It could then be piped across the country to heat people’s homes or used elsewhere in the energy system.”
Hydrogen as a fuel in action
For transport, there are already cars that run on hydrogen fuel cells. Japan has almost 100 public hydrogen refuelling stations, allowing you to fill up your car just as you would with petrol or diesel. Other countries including Germany and the US also have hydrogen stations.
“I’d say hydrogen fuel is promising for heavy good vehicles,” said Robert. “It’s more energy dense and can be offer quicker refuelling than electric. But they’re also building electric HGVs so there’ll be competition. In all our future energy scenarios, we look at the whole range.”
How is electricity generated using nuclear?
What is nuclear power?
Nuclear power stations work in a very similar method to coal and gas fired power stations.
A nuclear reactor is driven by the splitting of atoms, a process called fission, where a particle is fired at an atom, which then fissions into two smaller atoms and some additional neutrons. Some of the neutrons that are released then hit other atoms, causing them to fission too and release more neutrons. This is called a chain reaction, and the whole process creates a lot of heat.
The generated heat is removed from the reactor by a circulating fluid, typically water. This heat can then be used to generate steam, which drives turbines for electricity production.
What are the benefits of nuclear?
Firstly, in a sense a nuclear power plant is a traditional generator like coal or gas. It also provides vital system inertia. It’s also an ‘always on’ power source and isn’t dependent on the weather like wind and solar tends to be, and therefore can provide power 24/7.
Secondly, while we fully understand the concerns with the decommissioning of nuclear plants while operating, nuclear is zero carbon and adds no emissions to the atmosphere. This means they can deliver large amounts of electricity with no CO2 emissions resulting.
One of the benefits of nuclear is that it can run 24 hours a day with no additional fuel required. Although they require a lot of maintenance, some nuclear power stations are now certified for 80 years of operation, far longer than a gas or coal generator.
What is the future of nuclear electricity generation?
As we as NESO drive towards zero carbon operation in 2025, and the UK heads for net zero by 2050, the mix of electricity generation will change. 2020 saw the longest period of coal free generation, along with record wind and solar.
The Prime Minister discussed the role of nuclear in his recent 10-point plan, stating the UK government would be ‘Advancing nuclear as a clean energy source, across large scale nuclear and developing the next generation of small and advanced reactors’
Sizewell C is currently under consultation with proposed generation of 3.2GW.
In addition, the future may see the introduction of Small Modular Reactors. These are smaller version of nuclear power plants, similar to those that power nuclear submarines and ships e.g. very small reactors are used in Russian ice breaking ships. The benefit of these, as they are modular, is that they can be manufactured, shipped to locations near to demand, and then setup on site. At the end of their lifespan, they can be dismantled and sent back to the manufacturer.
The power output is substantially less than a full-scale nuclear power station, but they may still produce 200-500MW.
The UK is committed to the expansion of zero carbon renewables like wind and solar. However, nuclear power will continue to be a key generation source on the road to net zero in 2050.
How is electricity generated using solar?
solar power works by converting energy from the sun into power. There are two forms of energy generated from the sun for our use – electricity and heat.
Solar is an important part of NESO’s ambition to run the grid carbon zero by 2025. But how does solar power work, how much does the UK produce and what happens to solar on a cloudy day?
How does solar power work?
Solar power works by converting energy from the sun into power. There are two forms of energy generated from the sun for our use – electricity and heat.
Both are generated through the use of solar panels, which range those found on rooftops of our homes and businesses to ‘solar farms’ stretching across acres of land.
How is electricity from solar energy produced?
solar panels are made out of photovoltaic cells (which is why generating electricity with solar panels is also called solar PV) that convert the sun’s energy into electricity.
Photovoltaic cells sit between layers of semi-conducting materials such as silicone. Layers have different electronic properties that energise when hit by photons from sunlight, creating an electric field. This is known as the photoelectric effect – which creates the current needed to produce electricity.
Did you know? “1839 – Edmond Becquerel discovered the photovoltaic effect, the first step towards solar power.”
Solar panels generate a direct current of electricity. This is then passed through an inverter to convert it into an alternating current, which is funnelled into the grid, or used by homes and businesses which have panels installed.
How is electricity generated using wind?
Wind is all around us. It’s clean, it’s free (at point of generation) and is a reliable source of energy for countries all around the world. Every day, wind turbines capture the wind’s power and convert it into electricity.
It’s a fairly simple process: When the wind blows the turbine's blades spin, capturing energy – this energy is then sent through a gearbox to a generator, which converts it into electricity for the grid with a special device called an inverter.
There’s never been a more exciting time to work in energy.
We have around 23 gigawatts of wind-powered electricity capacity on the grid – several times that of nuclear. And in 2020 around 25% of Britain’s electricity was generated by wind, second only to gas in the sources that power our grid.
The UK’s geographical position means wind provides a fairly reliable source of energy. But we need turbines, and lots of them, to turn it into useful energy.
“There’s a perception that turbines are huge structures standing still at the side of the road not doing much,” says James. “But the stats show a different story. Just one turbine can make the electricity to power 16,000 homes a year. When you think we have multiple wind farms all around the UK, you can see that adds up to an awful lot of power.”
The UK government plans to invest £160m in offshore wind power to ensure the UK produces enough electricity to power every home in the country by 2030.
The latest turbines are super-efficient too. Unlike the older turbines (the first ones date back to the 1980s), they can operate well whatever the weather, and last for decades. Turbines are also much more flexible than say, a nuclear reactor (which currently operates to supply part of the base load), as you don’t have to have the entire wind farm running and can even feather the individual turbines to optimise their outputs.
The latest windfarm being built in the UK, Dogger Bank, will be the biggest yet. More than 80 miles from land, it will house around 200 of the world’s most powerful wind turbines, each almost as tall as The Shard, and populate an expanse of sea as large as North Yorkshire. Some of the newest turbines can power a home for a day with just one rotation of its blades.
Investments such as this help our progress in decarbonising British electricity. Learn more about carbon intensity and download our app.
But as with most things, there are downsides too.
“The UK is never going to be at a position where it’s 100% dependent on wind energy alone, it’s always a cocktail.” says James. “On the rare occasions when there’s no wind, we still need power. Demand is typically highest in the South East of England so you need to figure out how to distribute the energy from our wind farms, which are typically in windy places, like the North Sea." The Western Link subsea power cable which carries power from Scotland to England, is one way of allowing the flow of more clean energy south.
“Predicting can also be a challenge as we do that based on the weather, so there’s always an element of forecast uncertainty. But we use machine learning techniques and statistical modelling for this backed up with ancillary services and extensive planning. Therefore, we can top up the rest irrespective of how sunny it is or how windy.”
While we expect zero carbon sources like wind to dominate electricity supplies in the future, we also expect to have a diverse generation mix – including wind, solar, storage, nuclear and interconnectors.
“The key thing with electricity is it's made up like a cocktail mixture of all different types of ingredients and we combine these different flavours to produce a balanced grid second by second,” added James. “Just like changing your diet to be healthier, the grid’s fuels are changing to be greener, with carbon emitting fuels on the decline being replaced with zero carbon solutions to allow us to reach net zero.
There has never been a more exciting time to work in energy.”
What is embedded generation?
Generators (those who create power) connect onto the network in two ways – either as transmission connected generation or embedded generation.
It can help to think of it like a road network. The transmission network is like a motorway network which moves high voltage electricity around Great Britain, while the distribution network is like the smaller B roads, piping electricity locally into towns and cities.
Embedded generation (also known as distributed generation or distributed energy resources) refers to electricity generation or storage plants connected to a distribution network rather than the transmission network.
These plants are ‘embedded’ into the distribution network, generating and feeding electricity into it at a local level (the B roads).
NESO does not have real time visibility of most of this embedded generation, which accounts for 23% (ES1 FES 2024) of generation capacity on the electricity network.
Assumptions on embedded generation affect our demand forecasting and also how we manage frequency.
Embedded generation also adds to the overall system inertia which is an important tool for maintaining the system frequency within the statutory limits.
There are several different types of embedded generation, including combined heat and power (CHP) plants, onshore wind, solar farms, and storage devices such as lithium ion batteries.
Small plants that come on to meet peak demand, for example diesel generators and gas reciprocating engines, are also a type of embedded generation.
What is transmission connected generation?
Generators connect onto the network in two ways – either as transmission connected generation or embedded generation.
It can help to think of it like our roads network. The transmission network is the motorway network which takes high voltage electricity around Great Britain, while the distribution network is the smaller B roads, piping electricity locally into towns and cities at a lower voltage.
Transmission connected generation means the generator feeds straight into the transmission network (the motorways).
It's almost always large-scale generators who connect in this way, such as coal-fired power stations. Other types of transmission connected generation include onshore and offshore wind farms, nuclear, hydro, gas, biomass and battery storage.
At NESO, we have visibility of all transmission connected generation and around 65% (by Capacity – ES1 FES 2024) of Great Britain’s electricity connects in this way. However, we don’t have sight of embedded generation. So for example, if a small embedded solar farm started producing electricity, NESO would not see an increase in supply, but rather a reduction in demand, because it connected onto the network at a local level.
This is important because in order to balance generation and demand, NESO conducts close to real-time demand forecasting to predict the minute-by-minute demand change. When we can see the generation available, it helps us with our balancing role.
We only expect to see more types of embedded generation in the future as renewable generation becomes more common. This is a good thing, because it helps us towards a carbon free future. But it makes the network for more challenging for NESO to operate.
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