Great Britain’s electricity system is on track to be powered free of fossil fuels
and at 100% zero carbon in just four years’ time according to a new National Grid Electricity
System Operator (ESO) report. This is a key enabler for a zero carbon electricity system by
2035, in line with the 6th Carbon Budget.

Data released ahead of the COP26 climate summit in November, along with recent
electricity records, illustrates the growth in renewable electricity generation and
progress towards periods of zero carbon operation of the GB electricity system, an ambition
the ESO first announced in April 2019.

At present its control room needs to draw on conventional power plants (typically gas) to
deliver system reliability and manage properties such as voltage and frequency. By 2025 it
will have transformed its operation of the electricity system, so that when there is enough
zero carbon generation available, it can deliver electricity to Great Britain without using any
fossil fuels.

Since 2016 Britain’s electricity has been over two-thirds zero carbon for 5,000 half hour
periods, over 100 days cumulatively. In 2019 zero carbon sources outstripped fossil fuelled
electricity generation for the first time ever and 1.30pm on 17th August of that year saw the
highest share of zero carbon power ever seen at 85.1% (wind 39%, solar 25%, nuclear 20%
and hydro 1%). Wednesday 12 February 2020 saw the highest ever output from zero carbon
generators– 28.8GW – enough to power 10m homes for a week.

This latest update on progress towards zero carbon forms part of a new National Grid ESO
report ahead of the COP26 climate summit on November which showcases how Great
Britain’s electricity system has decarbonized in recent times, charting the key industry and
policy developments that have made it possible.

Fintan Slye, National Grid ESO Executive Director said:

“We’re confident that by 2025 we will have periods of 100% zero carbon electricity,
with no fossil fuels used to generate power in Great Britain. As with coal free
operation of the grid these may be short periods at first but will still be a significant
milestone on the road to net zero, and these periods will quickly extend.

“The growth in renewable sources of power, with record levels of wind and solar,
means there will be enough zero carbon generation to meet demand. A
key challenge is ensuring the electricity system is ready to accommodate that power.
Our engineers are deploying innovative, world first approaches to transform how the
power system operates, such as removing the need to draw on
fossil fuel based generation for critical stabilizing properties.“There’s still plenty of hard work ahead but it’s an exciting time and getting to this
position has been a huge team effort from everyone across the entire energy

“We look forward to the opportunity that COP26 brings and sharing GB’s progress
towards zero carbon with countries around the world. Electricity systems are at the
forefront of the energy transition and have the potential to be a catalyst to accelerate
decarbonisation on a global basis. Now is the time to come together, share learnings
and bring about lasting change.”

Energy Minister Anne-Marie Trevelyan said:

“The UK is leading the world in cleaning up our energy system and we continue to
break new records in wind and solar power, while coal has all but been eliminated
from the grid.

“Today’s report shows that the industry and the public’s hard work to drive up
renewables is paying off and we are on the cusp of achieving periods of 100% zero
carbon electricity generation with no fossil fuels used.

“There’s still some way to go, which is why we are powering forward with our
ambitious commitments to increase renewable power across the UK and invest in
new, green technologies so that we build back greener from the pandemic and tackle
climate change.”

May 23rd 2020 presents an example of how the ESO must transform the operation of the
power system ready for zero carbon.

On the day, the electricity market provided a near-100% zero carbon solution –
but the ESO’s control room had to intervene to ensure system stability, pulling back some
wind and hydro and replacing it with synchronous plant like gas and biomass which provided
sufficient inertia. That reduced the zero carbon proportion of the generation mix to around
83% over the day.

Its Stability Pathfinder project is finding new ways to source inertia, through synchronous
compensators, hydroelectric power stations or repurposed gas turbines, which means that
by 2025, if the market again presents 100% zero carbon power, it will no longer need to
reduce zero carbon generation.

More recent electricity records and statistics include:

• At 1pm on Easter Monday 5th April 21 the carbon intensity of electricity – the
measure of CO2 emissions per unit of electricity consumed – dropped to 39 gCO2,
the greenest Great Britain’s electricity grid has ever been.
• Coal generated only 1.6% of electricity in 2020, compared with almost 25% five years
• Spring 2020 saw Britain’s longest run since the industrial revolution generating
electricity without using coal, stretching almost 68 days (1,630 hours) between April
10 and June 16.• The record for the highest ever level of wind generation and proportion of the mix
was broken on 21st May 21 (17.7GW and 62.1%)
• At 1pm on Easter Monday 5th April 21 the carbon intensity of electricity – the
measure of CO2 emissions per unit of electricity consumed – dropped to 39 gCO2,
the greenest Great Britain’s electricity grid has ever been.
• Early afternoon on Sunday 11 June 2017 was the first time zero carbon power
contributed over 75% to Britain’s electricity mix.
• The same month – June 2017 – saw zero carbon power outstrip fossil fuel generation
across a month for the first time ever.

About National Grid ESO
National Grid Electricity System Operator – a legally separate business within the
National Grid Group – operates the electricity transmission system in Great Britain,
balancing supply and demand for electricity 24/7.
It does not own or operate any electricity generation or transmission but it’s engineers
and National Electricity Control Centre play a central role in managing electricity, liaising
with generators and regional distribution networks operators. Central to this is managing
key properties of electricity such as frequency and voltage ensuring a safe, secure and
reliable supply across Great Britain.

More on the ESO’s Zero Carbon ambition
In 2019 the ESO initiated a series of ‘pathfinder’ projects to identify and trial solutions to
procuring new services to provide frequency response, voltage, stability, restoration of
power and thermal constraints. This approach encouraged the market to come forward
with solutions – to bring in new sources of capital spend, new players into markets, and
new technologies. This contrasts with the typical approach in the rest of the world
whereby a monopolistic transmission owner identifies its preferred solution and builds it

For example, under the stability pathfinder, Drax has been contracted to provide inertia
through its Cruachan hydroelectric pumped storage plant located in a hollowed-out
mountain in Scotland, Welsh Power is installing a synchronous condenser and flywheel
at its site at Rassau in Ebbw Vale. Statkraft is developing two “Greener Grid Parks” in
Liverpool and Keith, Scotland. These new or modified assets will draw energy from the
grid to power their turbines and create inertia – rather than inertia being a by-product of
producing electricity. So, the same generators can continue providing inertia for the
system, but with dramatically reduced need to burn fossil fuels. It also means that wind
and solar power can stay online, rather than being paid to switch off, saving consumers
more than £100 million over the six-year duration of the contracts.

The ESO’s wider access programme has removed barriers to entry for a wider range of
technologies to access Great Britain’s balancing mechanism (BM) market. The BM isone of the main tools the ESO uses to balance supply and demand on the electricity
system in real-time, alongside balancing services like frequency response and reserve.
Through the BM, providers can offer to increase or decrease their generation or demand
to help balance the system.

‘Wider access’ enables the ESO to accept offers and bids from smaller providers, a
change that will improve system flexibility, allow more renewable power to contribute to
balancing the grid, and bring better value to consumers.

Late in 2020 the ESO also launched Dynamic Containment, the first in a suite of new
fast-acting frequency services to be introduced by the ESO to maintain the system close
to 50Hz – the frequency Britain’s grid must be kept at by balancing electricity supply and
demand second by second.

It’s designed to act rapidly when triggered by a fault on the system – for example the loss
of a generator – with providers, typically battery storage, injecting power into the grid to
catch and ‘contain’ the resulting deviation in frequency


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