Coal to clean – the UK's decarbonisation story

Growing up in Yorkshire in the 1970s you couldn’t miss the power of coal. The giant cooling towers of Eggborough, Ferrybridge and Drax, visible for miles, belched white steam into the sky; while over 50 collieries provided employment and a sense of community.

From the garden of my childhood home I could see these marvels of infrastructure, it sparked my interest and drove me to pursue a career in engineering.

When I first joined National Grid in 1989, we were still reliant on large coal-fired power stations to generate electricity for the country.That was simply how electricity was generated. The GB energy system has changed a lot since then.

With less than a year to go to COP 26 in Glasgow, I want to reflect on how the electricity system has evolved over the last few decades, moving away from coal and towards a clean energy system.

Over the next 12 months, the ESO will delve further into the specifics of the UK’s decarbonisation story.

We’ll set out the changes the UK made to policy, regulation and grid codes to enable the revolution from coal to clean.

The last 15 years have been truly transformative. The UK has led the world in decarbonisation, with the electricity sector slashing CO2 intensity by 60% between 2013 and 2019.

As the Electricity System Operator, we’ve played a key role in making this happen.

What happened and how did that change come about?

Until Calder Hall nuclear power station opened in 1956, almost all electricity in Great Britain was produced by burning oil or coal. Coal, and particularly oil, have environmental impacts producing carbon emissions alongside that iconic white steam, although this was well before the drive to cut carbon.

Our journey from coal to clean rapidly accelerated in 1992. That was the year that new legislation allowed the use of gas to generate electricity. Of course, gas is by no means a clean fuel, but the carbon output is substantially lower than coal.

The ‘Dash for Gas’ of the early 1990s transformed the industry, bringing more competition and a focus on consumers. By the early 2000s, gas power peaked, and new priorities emerged. The UK set itself ambitious decarbonisation targets, and the renewables revolution began.

Undertaking such a transformation makes you think more about the future. And the switch to gas prompted us to look at the network requirements for the next several decades.

This review led us to conclude that older coal-fired power stations would close to make way for newer, more efficient gas-powered generators.

However, power plant closures are not just a capacity issue – it is not as simple as replacing a GW of coal with a GW of gas. The location of the generators also matters.

The national electricity system was originally built around the concept of locating large generators near coal-fields.

These generators were connected to towns and cities by the network of large high-voltage overhead lines you see across the country. This is a simple and reliable concept requiring very little active management of the network.

Gas power plants are similar to coal, but many were in different locations spread out across the country. This created new operability challenges that the network was not designed for. As the Electricity System Operator, it is our job to foresee these challenges, and ensure the network evolves to overcome these them through working with our colleagues in the Transmission and Distribution network operators.

The changes we made in the 1990s enabled the closure of many of the most polluting generators and made gas the dominant form of electricity generation. It also set us on a pathway to think more about network management and put in place innovations that would lay the foundations for renewables.

Wind & Solar

Of course, without renewable generation sources net zero would be a distant dream. The birth of renewables began in 1991 with the UK’s first ever wind farm at Delabole in Cornwall. Solar PV came later, in 2010, with the first solar arrays at Benbole Farm near Wadebridge.

The 21st century has seen a huge growth in renewable electricity generation. Since 2004, the renewables share of electricity generation has increased tenfold.

In the past decade we’ve witnessed an ever-larger change – in 2011 under 5% of GB electricity was renewable; by 2019 that reached a record high of 37.1%.  

As with the transition to gas, this brings significant changes with it. Wind and solar farms are even more distributed across the country than gas, and they are variable in their output.

Providing connections to the network for renewables is not straightforward. Generators usually connect to the network on the basis that they can reach maximum output at any time – so the network is reinforced in their local area accordingly. However, with wind this is not the case.

If we approached wind in the same way as gas, we would overbuild the network. Therefore, in some areas, we allow wind to connect without undertaking the wider network reinforcements. This means we occasionally have to restrict output from wind generation, but it is a lower cost than building the transmission assets. This flexible approach promotes decarbonisation while protecting consumers from unnecessary costs.

This variability of renewables means that we need robust operability plans to ensure they can be utilised when they are available, and we have alternatives when they are not.

We’ve achieved this by developing new services, provided by both fossil fuel and renewable generators. These services support the network, enabling it to adapt to fluctuations in supply from renewables.

Today our greatest challenge is shifting the provision of these services from fossil fuel generators to renewable sources – many have doubted that this could be done.

However, through collaboration with partners across the electricity sector who all share our net zero goals, we are delivering world-leading innovations. These includes the first ever tendered contract to procure grid system inertia – replacing a key grid stability service that historically has been provided by traditional fossil fueled generation. This was the first time in the world that this approach to identifying and procuring grid inertia and stability had been delivered.

These innovations will empower us to take the next great step in the transition to a clean energy system – by 2025 we are planning to operate the network for periods of time without relying on any fossil fuel generation for energy or grid stabilising services.

Leading the way

The UK has been at the forefront of change, and we’re passionate about leading the way – working with others to deliver net zero both at home and abroad. That is why, as part of the journey to COP 26, we’ll be working with partners across the world to discuss how we can all accelerate decarbonisation and learn from each other’s experiences.  

Each country’s challenge is different, but through collaboration we can overcome any issue.

We are working with the Powering Past Coal Alliance, GO15 and the newly formed Global Power System Transformation Consortium to do just that. Through these international organisations we can share our knowledge and expertise with system operators, regulators, legislators, and policy makers across the world, helping each other on our decarbonisation journey.

We’ve proved that you can take an energy system with little renewable generation and transform it into a cleaner and greener system with deliverable plans for zero carbon operation.

I look forward to sharing more of this with you over the coming year.