From central heating to stove tops, you might think you know the role natural gas plays in your everyday energy usage. What you might not be aware of, however, is quite how important gas is in charging phones, powering TVs and keeping the lights on across the country.
In fact, natural gas is the largest single source of Great Britain’s electricity. It made up 41% of the electricity mix in the first quarter of 2019, followed by wind accounting for 21%.
Gas has far lower emissions than other fossil fuels, such as coal, diesel and oil, that are still part of the energy mix. More importantly, it plays an important role in helping the country to decarbonise.
Both the National Grid ESO’s Future Energy Scenarios and the Committee on Climate Change forecast gas remaining vital in the next few decades as we transition towards a carbon neutral UK. Here’s why.
One of the biggest steps toward achieving decarbonisation will be switching the majority of electricity production to renewable sources, predominantly wind and solar. But this will require technologies that have the capability to deliver power whatever the weather.
While wind currently accounts for between 10% and 20% of the annual electricity mix, it and other intermittent renewable sources, such as solar, can’t always be relied upon to deal with demand. For example when the wind’s not blowing and the sun’s not shining.
Gas, by contrast, can quickly and reliably start-up or shutdown to accommodate the variability of demand – such as during a major TV broadcast – and intermittent renewables.
What makes this even more important is the likely increase in electricity demand as the economy continues electrification of transport and heating. Catering for this demand will need flexible, fast power generation.
As a result, future-looking scenarios forecasting the UK achieving carbon neutrality by 2050 (for example, National Grid’s FES Net-Zero scenario) predict that, as well as renewables growing to become the biggest source of generation, there will also be a slight growth in gas power stations’ capacity to produce electricity.
It’s this gas power which will fulfil the need for fast, flexible electricity catering to sudden changes in demand. Crucially, these sites will facilitate the growth of zero carbon technologies like wind and solar at a time when we need to meet larger peaks in demand as a result of increased electrification.
For the country to get to this scenario, however, it will take investment and development. Many of the UK’s current gas power stations were built in the 1990s and are nearing the end of their lifetimes. Modernisation and new projects will be needed to ensure the country’s gas is used as efficiently as possible – and either built with carbon capture usage and storage (CCUS) or hydrogen in mind.
One of the major challenges an electricity system built around increased intermittency faces is keeping the grid balanced. Having a balanced grid means that electricity is transmitted to where it’s needed, when it’s needed, and safely.
The National Grid ESO currently does this by working with power generators to ensure all the necessary factors for a safe and stable grid are met through what are known as ‘ancillary services’. The challenge comes with what’s needed to provide these, which is often large spinning turbines that can be carefully controlled and adjusted.
One example of this is voltage control. Great Britain’s transmission system runs at a voltage of 400 kilovolts (kV) and 275 kV (Scotland also uses 132kV). This is ‘stepped down’ by transformers to 230 volts for homes, or 11 kV for heavy industrial users. On the transmission system, voltage must stay within 2.5% and under certain conditions 5% of 400 kV, otherwise it can begin to damage equipment.
To ensure voltage stays within that 2.5% safe zone, turbines have to be ready 24 hours a day, seven days a week to either generate or absorb what’s called ‘reactive power’. This acts as a partner to ‘active power’ – the type of power that actually lights up a light bulb.
Reactive power is generated the same way as active power and effectively ‘pushes’ active power around the system, moving it from power station to plug. By producing reactive power, a generator increases the voltage on a system, but by switching to absorbing reactive power it can help lower the voltage, keeping the grid’s electricity safe and efficient.
Another example is frequency control. Maintaining a consistent electrical frequency is important because multiple frequencies cannot operate alongside each other on the national system without damaging equipment.
In Great Britain, the grid frequency is 50Hz. Every generator in England, Scotland and Wales connected to the high voltage transmission system is synchronised to every other generator.
Heavy spinning generators provide inertia to the system. It’s their sheer weight that helps maintain system frequency near 50Hz whenever there is a mismatch between generation and demand.
The reduction in total inertia which accompanies the growth in intermittent renewables such as wind and solar presents a challenge for the system operator. The National Grid’s electricity control room works hard, around the clock, to ensure there is no risk of instability.
Wind and solar struggle to carry out these services in the way large turbines can. Gas’ fast response times allow it to offer ancillary services at short notice, helping to keep electricity safe and usable around the country.
Natural gas isn’t just a useful source of power generation, it is also an economical one. For a start, it is abundant. There is enough gas in reserve around the world to meet electricity and energy needs for the next 250 years.
The UK produces almost 50% of its gas domestically, while a further 40% is piped though an interconnector from Norway, making it a much more affordable fuel than coal. Its lower emissions mean it is not subject to the same levels of carbon taxes either, and these savings are passed on to suppliers and, ultimately, consumers.
Even constructing new gas power stations offers advantages over other sources, particularly nuclear. Building a new nuclear fleet is hugely expensive – often prohibitively so. As a result, a string of proposed nuclear projects at Moorside, Wylfa Newydd and Oldbury have been either put on hold or cancelled, leaving a 9.2 gigawatt (GW) hole in expected new low-carbon capacity.
Gas power stations, by contrast, are relatively straightforward and increasingly efficient. A Combined Cycle Gas Turbine (CCGT) uses the exhaust from a gas turbine. The heat that is recovered then turns water to steam in order to power a second turbine. This maximises the total power generated from its fuel.
Future-proofing gas power and the route to net zero
All recent forecasts by the National Grid and the Committee on Climate Change (CCC), predict natural gas playing a crucial role in meeting energy demand and providing balancing services as the UK moves towards carbon neutrality in 2050.
However, for it to take part in a zero-carbon landscape, carbon capture will be essential to future gas plants. This means that, while its role in the energy mix might slightly increase, its emissions will reduce drastically. Another way in which natural gas power stations could play an important role in a carbon neutral economy is in being repowered to run on hydrogen. Hydrogen can also act as a zero-carbon source of fuel for vehicles, industry and domestic heating.
But for all future scenarios what’s clear is the need for action now. That requires the modernisation and building of new gas power stations that can enable the transition to a future where gas remains a part of the energy mix – but rather than being its largest source, it will be the smallest.
Its role will be to act as a necessary and flexible stabiliser for the grid and as a partner to renewables, plugging gaps left by intermittency and catering to the growing demand electrification of the country’s economy will bring.
This won’t just mean we’ll have a more sustainable and stable electricity future, but a net-zero emissions one, too.