Everyone has been getting very excited today with the news that GB has gone a whole week without using coal to generate electricity…the first time this has happened since we first started using coal in the late 19th century, and just 2 years since the country saw its first coal-free day. Inevitably, this has led to claims that we are in touching distance of getting rid of fossil fuels and moving to a fully renewable electricity system.

“Wind has become a mainstream power source for the UK, providing up to 35% of our electricity over the weekend. Renewables overall are playing a leading role in our energy mix – and have been crucial to phasing out dirty coal,”
– Emma Pinchbeck, deputy chief executive, RenewableUK

coal free days

The reality is rather less exciting, and will in fact surprise many people. Not only are we far from being able to get rid of all fossil fuels, we also still rely on coal to keep the lights on in the winter (although bizarrely we also burn coal in the winter in order to export electricity to France!).

While the Government has commited to phasing out coal-fired generation by 2025, the dream of 100% renewables remains just that, a dream – the majority of electricity in GB is produced from gas, and gas also dominates the heating sector with 78% of homes using gas for heating.


Why we can’t say goodbye to coal just yet

To understand why we are still some distance from waving goodbye to coal, it is worth examining recent generation and demand data. The following chart shows average daily demand (in red) and the contribution of demand met by different technologies, including interconnectors.

Without delving too deeply into the data, it is immediately obvious that there is a very large difference between summer demand and winter demand, so managing a few days without coal in the summer is not that significant. It is also obvious that gas is far and away the most important fuel in the generation mix.

coal free days


The chart shows daily average levels. Of course National Grid, in its role as system operator, must ensure that the system has sufficient capacity to meet peak winter demand. Those cold, frosty winter days when the country experiences high pressure weather systems, are characterised by low temperatures and little wind (and of course, minimal potential for solar generation with short days and lower solar intensity), which leads to high demand and low renewables output.

coal free days

There were days last winter when coal was meeting almost 20% of GB demand, illustrating the ongoing reliance on coal in meeting peak winter demand.

However, as the chart also shows, the utilisation of coal across the year is low, and has been falling over recent years. In order to ensure plant is available when needed to meet peak winter demand, the Government introduced the capacity market, through which non-renewable generation, interconnectors, batteries and demand-side response can all compete to provide this back-up capacity through annual auctions.

Unfortunately this market is currently under suspension following withdrawal of the EU state aid approval…unless the situation can be quickly resolved (or a form of Brexit occurs which means EU state aid rules can be ignored), National Grid may have to revert to older, less efficient means of procuring reserve capacity.


The zero-carbon dream is just a dream

National Grid has announced that it believes operation of a zero carbon electricity system will be possible by 2025, a bold statement that has been taken to mean that 100% renewables is achievable by 2025.

However, National Grid qualifies its claim with the phrase “whenever there is sufficient renewable generation on-line and available to meet the total national load.” Clearly the GB system is a long way from being able to meet demand with 100% renewables – National Grid is only saying it thinks it will be able to manage 100% renewables if it happens, not that it thinks we will be at 100% renewables in the electricity system in the next 5 years.

National Grid’s report goes on to set out (briefly) the challenges it must address in order to be able to safely operate the system in the case that enough renewable generation was available, particularly in relation to frequency control and voltage management. The system operator is currently developing new approaches to balancing and ancillary services, and it’s not inconceivable that the main hurdles could be overcome over the next five years.

“Zero-carbon operation of the electricity system by 2025 means a fundamental change to how our system was designed to operate – integrating newer technologies right across the system – from large-scale offshore wind to domestic-scale solar panels to increased demand-side participation, using new smart digital systems to manage and control the system in real-time,”
– Fintan Slye, director of National Grid ESO

However, this is all a far cry from actually having a zero carbon electricity system, never mind a zero carbon energy sector or even a zero carbon economy (and de-carbonising other sectors such as heating and transport will almost certainly increase demand for electricity, meaning the capacity gap to 100% renewables becomes even larger….)

Last week, the Committee on Climate Change (“CCC”) published a report calling for the UK to be “net zero emissions” by 2050, saying that many of the means of achieving this such as electric vehicles and energy efficient buildings already exist, but need to be pushed further in order for emissions to be radically cut. In addition, abatement measures such as the use of carbon capture and storage (“CCS”), and the planting of trees will be necessary to achieve net zero emissions.

“Carbon capture (usage) and storage, which is crucial to the delivery of zero GH Gemissions and strategically important to the UK economy, is yet to get started. While global progress has also been slow, there are now 43 large-scale projects operating or under development around the world, but none in the UK,”
– Committee on Climate Change

Unfortunately, CCS is far from being commercially viable on a standalone basis. Despite the CCC’s comments in its report, all of the large-scale CCS projects currently in operation or under construction around in the world rely on hydrocarbon fuel production for their economics, whether that is enhanced oil recovery, natural gas processing or ethanol production. Clearly, hydrocarbon fuel use would be incompatible in a zero carbon world, so there is a long way to go before these projects can be self-supporting.

Of course another approach would be to replace existing thermal generation with new nuclear. Nuclear power is zero carbon, and could be considered a viable alternative, except huge capital costs are involved, and poor technology choices have left us trying to develop a highly complex and largely unproven European Pressurised Water Reactor (“EPR”) when a more sensible approach might have been to pursue Advanced Boiling Water Reactors (“ABWR”) which had a proven track record in Japan prior to the Fukushima disaster. There is still some hope for small modular reactors, or new technologies such as molten salt reactors, but these are some way from commercialisation.


The decline in coal use has been faster than expected, and renewable generation has become a significant part of the energy mix also faster than expected. While a few coal-free days in the summer is certainly progress compared with the year-round reliance we had on coal until relatively recently, there is really no prospect of eliminating fossil fuels from the generation mix any time soon. Coal continues to be essential for security of supply in the winter while gas is by far the most important component of today’s electricity market.





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12 thoughts on “Why the excitement about coal-free days is overblown

  1. “*Everyone* has been getting very excited today with the news that GB has gone a whole week without using coal to generate electricity”

    Certainly the BBC, and other parts of the Green Industrial Complex, but not everyone. If you value diversity of fuel supply, and the ability to turn up the output in response to demand increases (try doing that with wind or solar), you will be dismayed at the news that some power stations are now idle for many consecutive days. The Capacity Market is only sufficient to allow existing paid-for power stations to make enough money to survive, no way will anyone invest in new ones, so there will be an inevitable continuing decline in proper power stations, with obvious consequences for security of supply.

    Ask not for whom the bell tolls.

    1. I searched coal on Twitter and didn’t find a single tweet about this that wasn’t all about how “historic” and amazing going a week without coal is. The speed of the transition is impressive (whether you agree with it or not!) but the way this is being reported and discussed makes it sound as if we on the verge of getting rid of fossil fuels when we’re not even close to getting rid of coal.

      I agree that the capacity market hasn’t delivered the new plant that was hoped for. The problem is that even if the Government does manage to continue with the planned auction this summer, no-one will bid in new capacity while the market is suspended. Depending on what happens with the various legal processes and the state aid review there is a prospect of historic payments being clawed back, but Brexit might make those processes irrelevant.

      To be fair to the BBC though, they did interview me about this last week (More or Less on R4) and we discussed the challenges of going coal-free never mind 100% renewables.

  2. Please remember the high CO2 producing biomass woodchips at Drax, and that all power from the Netherlands on the BritNed connector comes from the coal and woodchip fired Maasvlakte power stations at the mouth of the Rhine in Rotterdam. We cannot claim a coal free day unless we import zero from the Netherlands. I’m not certain of the power flows over the NEMO link to Belgium, but these may also include coal fired power.

    1. Drax is an abomination…the idea that you would cut down trees in the US, expend energy drying and pelletising them, and then shipping them in bunker-fuelled ships across the Atlantic is insane, and I cannot believe how anyone thinks this remotely sustainable.

      The other interesting interconnector fact is that in the winter it’s not that ususual for us to export on IFA while running coal…

    1. Thanks, I found it. I added a comment of my own over there – it’s a shame their article presents such a misleading impression of the significance of this news.

      I love the link to the original Edison article though!

      1. Hi Kathryn,
        I see The Engineer removed your post + the reply from the odious ‘green zealot’ Silvia Leahu-Aluas

        ((Silvia Leahu-Aluas 14th May 2019 at 9:15 pm
        @Kathryn are you saying that you are long on coal and short on RE? Let us know in 2025 how much you made from this investment strategy.))

        The Engineer used to be the go-to place for reliable engineering facts, run by people with practical engineering backgrounds, sadly these days they only like their own ‘journalistic facts’, anything else is on thin ice; much like ‘The Conversation’ who claim – “Academic rigour, journalistic flair” …until you question the consensus… then you are excommunicated !

        1. It looks as if both comments are there now, although my reply to Silvia seems to have disappeared…I’ll check again later.

          Fine to moderate, but not fine to censor, and it’s disappointing when apparently serious publications start being selective with data and removing perfectly legitimate data that don’t fit their narrative.

          I allow all comments on here except for spam/junk and specific rants (eg I’ve had people try to let off steam on my smart meters posts about how much they hate their supplier, and accusing them of theft and fraud etc, which isn’t what my blog is for…)

    1. Thanks Julian!

      That report is really interesting and shows that in terms of NOx and PM, wood biomass is much worse than gas or light fuel oil. I’m surprised by the CO2 but wonder if they are offsetting the pre-felling absorption since they mention whole life-cycle from cultivation. I don’t actually think that’s a reasonable way of analysing it because it doesn’t take into account plant maturity, biodiversity etc.

      It also illustrates really well the problems with focusing on CO2, when NOx and PM – PM in particular – are more immediately damaging to health. I worry that there is a level of hysteria about CO2 now that will push us into environmentally damaging policy decisions… displacement of food crops for biomass crops, impact of windfarms on biodiversity, consumption of rare elements in battery production (and the pollution associated with their extraction) and so on.

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