Archive for the ‘Nuclear Matters’ Category

Heating Degree Days:3: How do they vary?

March 15, 2022

Friends, having read the previous two posts (1, 2) about Heating Degree Days, you may be wondering.

  • How carefully do I need to be in choosing the baseline temperature?
  • How do heating degree days vary around the UK?
  • How do heating degree days vary from year-to-year?

If you were wondering things, then the text below should provide the answers you seek.

Seek on!

Choice of Base Temperature

Click on Image for a larger version. The graph shows annual running average of the number of heating degree days for the London St. James Park Weather station. Each curve corresponds to the number of heating degree days with a difference base-temperature. For each degree Celsius increase in the internal temperature, the heating demand increase by approximately 260 °C-days.

The choice of the base temperature is important when estimating heating demand.

The evidence in the previous article is that a ‘rule of thumb’ for choosing a base temperature is to pick a value 3.5 °C below the internal thermostat setting is probably OK.

  • 19 °C thermostat setting: use a base temperature of 15.5
  • 20 °C thermostat setting: use a base temperature of 16.5
  • 21 °C thermostat setting: use a base temperature of 17.5

Using data from St James Park in London, each 1 °C change in base temperature changes the annual degree-day estimate by roughly 260 °C-days/year. So if we estimate an average value of HDD(17.5 °C) is ~ 2,100, then turning down the thermostat by 1 °C would reduce heating demand (and hence gas consumption) by ~260/2,100 = 12.4%.

Variability over Time

Click on Image for a larger version. The graph shows annual running average of the number of heating degree days based on a 16.5 °C base temperature for London Heathrow Airport (in black). The dotted lines show the 20-year average and ± 1 standard deviation. Also shown are the monthly degree day totals (in purple) from which the annual averages are derived.

Looking at the data from Heathrow – which has a longer HDD record than most stations

  • The average number of HDD(16.5)s is 2053 °C-days/year and the standard deviation is roughly 8%.
  • The average number of HDDs(15.5)s is 1778 °C-days/year and the standard deviation is roughly 9%.

First we notice that the difference between HDD(15.5) and HDD(16.5) is 275 °C-days/year, similar to the 260 °C-days/year that we deduced from looking at the St James’s Park data.

Considering the variability, a standard deviation of 8% or 9% suggests that once in 20 years or so one might expect winters which have 16% or 18% more heating demand.

Variability with Location

The number of HDDs varies from place to place. The figure and table below show the number of HDDs based on a 16.5 °C base temperature averaged over the last 3 years.

  • A wide swathe of southern England, from Manchester southward, has heating demand within approximately 16% of the heating demand at Heathrow.
    • i.e. in the range 2,150 ± 150 °C-days/year
  • In Yorkshire, the North East, and Central Scotland, heating demand is about 25% greater than Heathrow.
    • i.e. ~ 2,500 °C-days/year

Click on Image for a larger version. The annual number of heating degree days based on a 16.5 °C base temperature for various UK locations averaged over the 3-year period from 1/3/2019 – 28/2/2022. The data are also shown as deviations from the number of HDDs(16.5 °C) at Heathrow Airport.

Click on Image for a larger version. Summary of the results in the previous figure.

In addition to large scale variations across the UK, there are smaller variations due to local factors, notably elevation and the city heating effect.

Based on the typical decline in temperature with height (typically 6.5 °C/km) then each 100 m of additional elevation would be approximately 0.65 °C colder. This will result in additional HDDs roughly equivalent to 275 x 0.65 °C or 165 °C-days/year.

To look at the urban heat island effect, I downloaded data from 4 locations around London.

Click on Image for a larger version. The annual number of heating degree days based on a 15.5 °C base temperature 4 locations around London.

Compared to data at Heathrow, there are significant changes in heating demand, with the centre of London being significantly warmer, and Gatwick Airport – just 38 km from the centre of London – being significantly colder.

Variability Summary

The heating demand at Heathrow Airport with base temperature of 16.5 °C (i.e. a likely thermostat temperature of 20 °C) is very roughly 2,000 °C-days per year.

This 2000 °C-day/year varies by typically:

  • 10% in nearby locations depending on more or less urban heating.
  • 12% to 15% per °C change in base temperature
  • -3% to + 15% over England and Wales south of the latitude of Manchester.
  • Up to 30% as far north as Aberdeen
  • Year to year variability of ±9% with occasional excursions to ±18%

So if one could not look up the number of degree days for a particular location (which one can easily at Degree Days!) one could characterise heating demand against a base temperature of 16.5 °C as likely to be within 15% of 2,300 °C-days per year almost anywhere in the  UK.

Nuclear Fusion is Irrelevant

February 14, 2022

Click for a larger image. News stories last week heralded a major breakthrough in fusion research. Links to the stories can be found below.

Friends, last week we were subjected to a press campaign on behalf of the teams of scientists and engineers who are carrying out nuclear fusion research.

Here are links to some of the stories that reached the press.

  • BBC Story
    • If nuclear fusion can be successfully recreated on Earth it holds out the potential of virtually unlimited supplies of low-carbon, low-radiation energy.”
  • Guardian Story #1
    • Prof Ian Chapman, the chief executive of the UK Atomic Energy Authority said “It’s clear we must make significant changes to address the effects of climate change, and fusion offers so much potential.”
  • Guardian Story#2 (from last year)
    • The race to give nuclear fusion a role in the climate emergency

The journalists add little to these stories – they mainly consist of snippets from press releases spun together to seem ‘newsy’. All these stories are colossally misleading.

Floating in the background of these stories is the idea that this research is somehow relevant to our climate crisis. The aim of this article is to explain to you that this is absolutely not true.

Even with the most optimistic assumptions conceivable, research into nuclear fusion is irrelevant to the climate crisis.

Allow me to explain how I have come to this conclusion.

Research into a practical fusion reactor for electricity generation can be split into two strands: an ‘old’ government-backed one and a ‘new’ privately-financed one.

The state of fusion research: #1 government-backed projects

The ‘old’ strand consists of research funded by many governments at JET in the UK and the colossal new ITER facility being constructed in France.

In this strand, ITER will begin operation in 2025, and after 10 years of ‘background’ experiments they will begin energy-generating experiments with tritium in 2035, experiments which are limited by design to just 4000 hours. If I understand correctly, operation beyond this limit will make ITER too radioactive to dismantle.

The key operating parameter for fusion reactors is called Q: the ratio of the heat produced to the energy input. And the aim is that by 2045 ITER will have achieved a Q of 10 – producing 500 MW of power for 400 seconds with only 50 MW of input energy to the plasma.

However ITER will only generate heat, not electricity. Also, it will not create any tritium but will instead only consume it. Following on from ITER, a DEMO reactor is planned which will have a Q value in the range 30-50, and which will generate electrical power, and be able to breed tritium in the reactor.

So on this ITER-proposed time-line we might expect the first actual electricity generation – may be 100 MW of electrical power – in maybe 2050.

And then assuming that these reactors take 10 years to build and that the design will evolve a little, it will be perhaps 2070 before there are ten or so operating around the world.

You may consider that research into a technology which will not yield results for 50 years may or may not be a good idea. I am neutral.

But it is definitely irrelevant to our climate crisis: we simply do not have 50 years in which to eliminate carbon dioxide emissions from electricity generation in the UK.

And this is on the ITER-proposed timeline which I consider frankly optimistic. If one considers some of the technical problems, this optimism seems – to put it politely – unjustified.

Here are three of the issues I keep at the top of my file in case I meet some fusion scientists at the folk club.

  • Q is the ratio of heat energy injected into the plasma to the heat energy released. But in order to be effective we have to generate net ELECTRICAL energy. So we really need to take account of the fact that thermodynamics limits the electrical generation to ~30% of the thermal energy produced. Additionally we need to include the considerable amounts of energy used to operate the complex machinery of a reactor. So we really need to consider a wider definition of Q, one that includes the ratio of input to output energies involving the entire reactor. Sabine Hossenfelder has commented on this issue. But basically, Q needs to be a lot bigger than 10.
  • Materials. The inside of the reactor is an extraordinarily hostile place with colossal fluxes of neutrons passing through every part of the structure. After operation has begun, no human can ever enter the environment again – and it is not clear to me that a working lifetime of say 35 years at 90% availability is realistic. Time will tell.
  • Tritium. The reactor consumes tritium – possibly the most expensive substance on Earth – and for each nucleus of tritium destroyed a single neutron is produced. The neutrons so produced must be captured to produce the heat for electrical generation. But the neutrons are also needed to react with lithium to produce more tritium. Since some neutrons are inevitably lost – so the plan is for extra neutrons to be ‘bred’ by bombarding suitable materials with neutrons, which then produce a shower of further neutrons – 2 or 3 for every incident neutron. And these neutrons can then in principle be used to produce tritium. But aside from being technically difficult, this breeding process also produces long-lived radioactive waste – something fusion reactors claim not to do.

If short, when one considers some of these technical problems, optimism that this research path will produce significant power on the grid in 2070 seems to me to be unjustified.

But what about this new ‘breakthrough’?

The breakthrough was not a breakthrough. It was undertaken because the walls of the previous reactor were found to absorb some of the fuel! So this ‘breakthrough’ represented a repeat of a previous experiment, but with new materials in place.

You can relive the press conference here.

Starting with a much larger amount of energy, they managed to produce 59 megajoules (MJ) of energy from fusion in about 8 seconds.

59 MJ is about 16.4 kWh of energy, which is sufficient to heat water for around 500 cups of tea, more than a cup of tea each for all the scientists and engineers working on the project.

For comparison, the 12 solar panels on my house will produce this easily in a day during the summer. To generate the energy in 5 seconds rather than 12 hours would require more panels: a field of panels roughly 200 m x 250 m, which would cost a little under 1 million pounds.

So the breakthrough is modest in absolute terms. But as I mentioned above, after billions more in funding, and another 20 years of research, the scientists expect to extend this generating ‘burn’ from 5 seconds to 400 seconds at a much higher power level.

In my opinion, JET and ITER are a complete waste of money and should be shut down immediately. The resources should be transferred to building out solar and wind energy projects alongside battery storage.

The state of fusion research: #2 privately-backed projects

The ‘new’ strand of fusion research consists of activities carried out primarily by privately-funded companies.

What? If the massive resources of governments can only promise fusion by 2070, how can private companies hope to make progress?

The answer is that JET and ITER were planned before a technical key advance was made, and they are committed to proceeding without incorporating that advance! Its a multi-billion pound version of “I’ve started so I’ll finish“. It is utter madness, and doubly guarantees the irrelevance of ITER.

The technical advance is the achievement of superconducting wire which can create magnetic fields twice as large as was previously possible. It turns out that the volume of plasma required to achieve fusion scales like the fourth power of the magnetic field. So doubling the magnetic field makes the final reactor potentially 16 times smaller!

This also makes it dramatically cheaper requiring amounts on the order of $100 million rather than billions of dollars. Critically, reactors can exploit the concept of Small Modular Reactors (SMRs) which can be mass-produced in a factory and shipped to a site. Potentially the first reactors could be built in years rather than decades, and the technology iterated to produce advances.

I have written about this previously. With some qualifications, I think this activity is generally not crazy  (it is certainly much less crazy than JET and ITER) but success is far from guaranteed.

A key unresolved question with this technology concerns its potential timeline for delivery of a working power plant.

The reactors face exactly similar problems to those in the much larger ITER reactor, and these are not problems that can be solved in months. So let’s suppose that the first demonstration of Q>1 is achieved in just 5 years (2027), and that all the technical problems with respect to electricity generation required only a further 10 years (2037). Given the difficulties in planning, let’s optimistically assume that the first production plant could get built just 5 years after that in 2042.

The ‘S’ in SMR means reactors would be small, with a thermal output of perhaps 150 MW and an electrical output of perhaps 50 MW. This is small on the scale of typical thermal generation plant. For example Hinckley C is designed to output 3,200 MW of electrical power i.e. more than 60 times larger than a hypothetical SMR fusion reactor.

So if we assume a rapid roll out and no technical or societal problems, then perhaps these reactors might generate significant power onto the grid in perhaps 2050. Nominally this is 20 years ahead of ITER.


With optimistic assumptions concerning technical progress, we might hope for fusion reactors to begin to make a significant contribution to the grid somewhere between 2050 and 2070, depending on which route is taken.

That is already too late to make any contribution to our climate crisis.

We need to deploy low-carbon technologies now. And if we have a choice between reducing carbon dioxide emissions now, or in 30 – 50 years, there is no question about what we should do.


We also need to consider the likely cost of the electricity produced by a fusion reactor.

Like conventional fission-based nuclear power, the running costs should be low. Deuterium is cheap and the reactor should generate a surplus of tritium.

The majority of the cost of conventional nuclear power is the cost of the capital used to construct the reactor. If I recall correctly, it amounts to around 95% of the cost of the electricity.

It is hard to imagine that a fusion reactor would be cheaper than a fission reactor – it would be at the limit of manageable engineering complexity. So we might imagine that the costs of fusion-generated electricity would be similar to the cost of nuclear power – which is already most expensive power on the grid.

In contrast, the cost of renewable energy (solar and wind) has fallen dramatically in recent years. Solar and wind are now the cheapest ways to make electricity ever. And their cost – along with the cost of battery storage – is still falling.

So it seems that after waiting all these years, the fusion-based electricity would in all likelihood be extraordinarily expensive.


The idea of generating electricity from nuclear fusion has been seen as technological fix for climate change. It is not.

Even the most optimistic assumptions possible indicate that fusion will not make make any significant contribution to electricity supplies before 2050.

This is too late to help in out in our climate crisis which is happening now.

Additionally the cost of the electricity might be expected to exceed the cost of conventional nuclear power stations – the most expensive electricity currently on the UK grid.

If as an alternative, we invested in renewable generation from wind, solar and tidal resources, together with ever cheaper storage, we could begin to address our climate crisis now in the knowledge that the technology we were deploying would likely only ever get better. And cheaper.



The World Set Free

June 26, 2021

I recently re-readThe World Set Free” by H.G. Wells, a book which has a decent claim to being the most influential work of fiction of the 20th Century.

Written in 1913, a central theme of the book is that access to energy is central to the advance of global civilisation.

In the prologue, he imagines early humans wandering over the Earth and not realising that, first coal, and then later nuclear fuel, was literally under their feet.

Rendering of the gigantic planned SunCable solar farm. Copyright SunCable.

I had revisited the text because I realised that Wells had ignored the energy in the sunlight falling on the Earth, of which we require just 0.01% to power our advanced civilisation.

And so now, we can simply collect the largesse of energy that falls on the Earth everyday.

But it is unfair to criticise a futurist for what they omitted – getting anything right at all about the future is hard.

But re-reading the book I realised that Wells’ imagined vision of the future has been – I think – profoundly influential. Let me explain.

The Most Influential Book of the Twentieth Century?

The book initially follows a scientist (Holsten) who uncovers the secret of what he calls “induced radio-activity” – allowing the controlled release of nuclear energy.

And eventually a world of atomic-powered planes and automobiles follows.

But the political institutions of the world remained archaic and unsuited to the possibilities of this new world.

And in a stand-off broadly following the divisions of the actual World Wars, he foresees a global war fought with atomic weapons – a phrase which I think he must have invented.

Fictional Atomic Bombs

Of course in 1913, atomic bombs did not exist. H G Wells envisaged them as follows.

“…the bomb-thrower lifted the big atomic bomb from the box and steadied it against the side [of the plane]. It was black sphere roughly two feet in diameter. Between its handles was a little celluloid stud, and to this he bent his head until his lips touched it. Then he had to bite in order to let air in upon the inducive. Sure of its accessibility, he craned his neck over the side of the aeroplane and judged his pace and distance. Then very quickly he bent forward, bit the stud, and hoisted the bomb over the side.

“Never before in the history of warfare had there been a continuing explosive… Those used by the allies were lumps of pure Carolinum, painted on the outside with un-oxidised cydonator inducive enclosed hermetically in a case of membranium. A little celluloid stud between the handles by which the bomb was lifted was arranged so as to be easily torn off and admit air to the inducive which at once became active and set up the radioactivity in the outer layer of the Carolinum sphere. This liberated fresh inducive and so in a few minutes the whole bomb was a blazing continual explosion.

Carolinum belonged to the beta group of Hyslop’s so-called ‘suspended degenerator’ elements, [and] once its degenerative process had been induced, continued a furious radiation of energy and nothing could arrest it. Of all of Hyslop’s artificial elements, Carolinum was the most heavily stored with energy and the most dangerous to make and handle. To this day it remains the most potent degenerator known. What earlier 20th Century chemists called its half-period was seventeen days; that is to say, it poured out half the huge store of energy in its great molecules in the space of seventeen days, the next seventeen days’ emission was half of that first period’s outpouring and so on…. to this day, the battle-fields and bomb fields of that frantic time in human history are sprinkled with radiant matter, and so centres of inconvenient rays

“A moment or so after its explosion began, [the bomb] was still mainly an inert sphere exploding superficially, a big inanimate nucleus wrapped in flame and thunder. Those that were thrown from aeroplanes fell in this state, they reached the ground mainly solid, and, melting soil and rock in their progress bored into the earth. There, as more and more of the Carolinum became active, the bomb spread itself out into a monstrous cavern of fiery energy at the base of what became very speedily a miniature active volcano. The Carolinum, unable to disperse, freely drove onto and mixed up with the boiling confusion of molten soil and superheated steam, and so remained spinning furiously and maintaining an eruption that lasted for years or months or weeks according the size of the bomb…

“Once launched the bomb was absolutely unapproachable and uncontrollable until its forces were nearly exhausted, and from the crater that burst open above it, puffs of heavy incandescent vapour and fragments of viciously punitive rock and mud, saturated with Carolinum, and each a centre of scorching and blistering energy, were flung high and far.

“Such was the crowning triumph of military science, the ultimate explosive that was to give the ‘decisive touch’ to war…

Actual Atomic Bombs

Of course almost every detail of the account above is wrong.

But qualitatively, it is spot on: a single weapon which could utterly destroy a city not just at the time of its detonation, but have effects which would persist for decades afterwards: the “ultimate explosive”

And critically, the book was read by Leo Szilard, a man with a truly packed Wikipedia page!

On September 12, 1933, having only recently fled Germany for England, Szilard was irritated by a Times article by Rutherford, who dismissed the possibility of releasing useful amounts of nuclear energy.

And later that day, while crossing Southampton Row in London, it came to him how one could practically release nuclear energy by making a nuclear chain reaction. He patented his idea and assigned the patent to the UK Admiralty to maintain its secrecy.

In the following years he was influential in urging the US to create a programme to develop nuclear weapons before the Germans, and so he came to be present in Chicago when Fermi first realised Szilard’s chain reaction on December 2nd 1943.

On seeing his invention work, he did not rejoice. He recalls…

“There was a crowd there and when it dispersed, Fermi and I stayed there alone. Enrico Fermi and I remained. I shook hands with Fermi and I said that I thought this day would go down as a black day in the history of mankind.

I was quite aware of the dangers. Not because I am so wise but because I have read a book written by H. G. Wells called The World Set Free. He wrote this before the First World War and described in it the development of atomic bombs, and the war fought by atomic bombs. So I was aware of these things.

But I was also aware of the fact that something had to be done if the Germans get the bomb before we have it. They had knowledge. They had the people to do it and would have forced us to surrender if we didn’t have bombs also.

We had no choice, or we thought we had no choice.

Was the book really influential?

Of course I don’t know.

But it is striking to me that by merely imagining that such terrible weapons might one day exist, and feasibly imagining the circumstances and results of their use, H.G. Wells placed this idea firmly into Szilard’s mind.

And Szilard was a man who – with good reason – feared what the German regime of the time would do with such weapons.

And so when recalling the first sustained and controlled release of atomic energy in Chicago, he immediately recalled H.G. Wells vision of a war fought with atomic bombs.


“The World Set Free” is fascinating to read, but it is not – in my totally unqualified opinion – a great work of literature.

The characters are mainly implausible, and the peaceful and rational world government Wells envisages would follow nuclear devastation might be better characterised by George Orwell. (Scientific American contrast Orwell and Wells’ ideas about science and society in an interesting essay here.)

By contrast, some of the plot twists are strikingly plausible. I was struck in particular when – after the declaration of World Government from a conference in Brissago in Switzerland – one single monarch held out.

In what might now be called “a rogue state”, a conniving ruler – “a Fox” – sought to conceal some “weapons of mass destruction”. After an attempted pre-emptive strike on the World Government was foiled, an international force searched the rogue state, grounding its aeroplanes, and a search eventually unearthed a stash of atomic bombs hidden under a haybarn.

Perhaps George Bush had been reading “The World Set Free” too!



A Bright Future?

May 3, 2021

Click for a larger Image of the book covers.

Friends, a few weeks ago I reviewed two books about our collective energy future: Decarbonising Electricity Made Simple and Taming the Sun.

Summarising heavily

  • Decarbonising Electricity Made Simple
    • A detailed look at how the UK can attain very low carbon intensity electricity – perhaps less than 50 gCO2/kWh in 2030 – by just doing more of what we are already doing
  • Taming the Sun
    • A look at the role of solar power globally, addressing the fact that every ‘market’ will reach the point where super-cheap solar electricity is so abundant that nothing else will compete – during the day. But because of the lack of storage, solar will never be a sufficient answer.

This weekend I read A Bright Future by Joshua Goldstein and Staffan Qvist. The strapline is “How some countries have solved climate change and the rest can follow”.

Their answer is simple:

Start building nuclear power stations now and don’t stop for the next 50 years.

The authors point out

  • The astonishing safety record of nuclear power which is in direct contrast to the coal industry in which thousands of people die annually – and which releases more radioactivity and toxic compounds than nuclear power stations ever have.
  • The enormity of the climate peril into which we are collectively entering.
  • The scale of output which is achievable with nuclear power stations – generating capacity can potentially be added much faster than renewable generation.
  • The reliability of nuclear power and they contrast this with the variability of wind and solar generation.

And while I could disagree with the authors on several details, the basic correctness of their assertion is undeniable.

  • In the UK if we had one or two more nuclear power stations our climate goals would be dramatically easier to meet.
  • Globally, there are currently 450 nuclear power stations undramatically providing emission-free electricity. If there were 10 times this number our collective climate emergency would be easier to address.

And while it would be an understatement to say that nuclear power is without controversy – it seems to me that a massive investment in nuclear power plants worldwide would be a good move.

But it is not going to happen.

I am sure the authors know that their arguments are futile.

Although I personally would welcome a nuclear power plant in Teddington, most people would not.

Similarly most people in Anytown, Anywhere would not welcome a nuclear power station.

But as the authors point out – correctly – there is no renewable energy technology that match the characteristics of nuclear power.

And we need every possible low-carbon generating source to address humanity’s needs

Despite the authors’ positivity, I have never felt more depressed after reading a book than this.


Are fusion scientists crazy?

July 8, 2020


I was just about to write another article (1, 2, 3) about the irrelevance of nuclear fusion to the challenges of climate change.

But before I sharpened my pen, I thought I would look again to see if I could understand why a new breed of fusion scientists, engineers and entrepreneurs seem to think so differently. 

Having now listened to two and a half hours of lectureslinks at the bottom of the page – I have to say, I am no longer so sure of myself.

I still think that the mainstream routes to fusion should be shut down immediately.

But the scientists and engineers advocating the new “smaller faster” technology make a fair case that they could conceivably have a relevant contribution to make. 

I am still sceptical. The operating conditions are so extreme that it is likely that there will be unanticipated engineering difficulties that could easily prove fatal.

But I now think their proposals should be considered seriously, because they might just work.

Let me explain…


Deriving usable energy from nuclear fusion has been a goal for nuclear researchers for the past 60 years.

After a decade or two, scientists and engineers concluded (correctly) that deriving energy from nuclear fusion was going to be extraordinarily difficult.

But using a series of experiments culminating in JET – the Joint European Torus, fusion scientists identified a pathway to create a device that could release fusion energy and proceeded to build ITER, the International Thermonuclear Experimental Reactor.

ITER is a massive project with lots of smart people, but I am unable to see it as anything other than a $20 billion dead end – a colossal and historic error. 

Image of ITER from Wikipedia modified to show cost and human being. Click for larger view.

In addition to its cost, the ITER behemoth is slow. Construction was approved in 2007 but first tests are only expected to begin in 2025; first fusion is expected in 2035; and the study would be complete in 2045.

I don’t think anyone really doubts that ITER will “work”: the physics is well understood.

But even if everything proceeds according to plan, and even if the follow-up DEMO reactor was built in 2050 – and even if it also worked perfectly, it would be a clear 40 years or so from now before fusion began to contribute low carbon electricity. This is just too late to be relevant to the problem of tackling climate change. I think the analysis in my previous three articles still applies to ITER.

I would recommend we stop spending money on ITER right now and leave it’s rusting carcass as a testament to our folly. The problem is not that it won’t ‘work’. The problem is that it just doesn’t matter whether it works or not.

But it turns out that ITER is no longer the only credible route to fusion energy generation.

High Temperature Superconductors

While ITER was lumbering onwards, science and technology advanced around it.

Back in 1986 people discovered high-temperature superconductors (HTS). The excitement around this discovery was intense. I remember making a sample of YBCO at Bristol University that summer and calling up the inestimable Balázs Győrffy near to midnight to ask him to come in to the lab and witness the Meissner effect – an effect which hitherto had been understood, but rarely seen.

But dreams of new superconducting technologies never materialised. And YBCO and related compounds became scientific curiosities with just a few niche applications.

But after 30 years of development, engineers have found practical ways to exploit them to make stronger electromagnets. 

The key property of HTS that makes them relevant to fusion engineering is not specifically the high temperature at which they became superconducting. Instead it is their ability – when cooled to well below their transition temperature – to remain superconducting in extremely high magnetic fields.

Magnets and fusion

As Zach Hartwig explains at length (video below) the only practical route to fusion energy generation involves heating a mixture of deuterium and tritium gases to immensely high temperatures and confining the resulting plasma with magnetic fields.

Stronger electromagnets allow the ‘burning’ plasma to be more strongly confined, and the fusion power density in the burning plasma varies as the fourth power of the magnetic field strength. 

In the implementation imagined by Hartwig, the HTS technology enables magnetic fields 1.74 times stronger, which allows an increase in power density by a factor 1.74 x 1.74 x 1.74 x 1.74 ≈ 9. 

Or alternatively, the apparatus could be made roughly 9 times smaller. So using no new physics, it has become feasible to make a fusion reactor which is much smaller than ITER. 

A smaller reactor can be built quicker and cheaper. The cost is expected to scale roughly as the size cubed – so the cost would be around 9 x 9 x 9 ~ 700 times lower – still expensive but no longer in the billions.

[Note added on 8/2/2021: I think this large factor is justified: see my response to the comment from Dr Brian VonHerzen for an explanation]

And crucially it would take just a few years to build rather than a few decades. 

And that gives engineers a chance to try out a few designs and optimise them. All of fusion’s eggs would no longer be in one basket.

The engineering vision

Dennis Whyte’s talk (link below) outlines the engineering vision driving the modern fusion ‘industry’.

A fusion power station would consist of small modular reactors each one generating perhaps only 200 kW of electrical power. The reactors could be produced on a production line which could lower their production costs substantially.

This would allow a power station to begin generating electricity and revenue after the first small reactor was built. This would shorten the time to payback after the initial investment and make the build out of the putative new technology more feasible from both a financial and an engineering perspective.

The reactors would be linked in clusters so that a single reactor could come on-line for extra generation and be taken off-line for maintenance. Each reactor would be built so that the key components could be replaced every year or so. This reduces the demands on the materials used in the construction. 

Each reactor would sit in a cooling flow of molten salt containing lithium that when irradiated would ‘breed’ the tritium required for operation and simultaneously remove the heat to drive a conventional steam turbine.

You can listen to Dennis Whyte’s lecture below for more details.


Dennis Whyte and Zach Hartwig seem to me to be highly credible. But while I appreciate their ingenuity and engineering insight, I am still sceptical.

  • Perhaps operating a reactor with 500 MW of thermal power in a volume of a just 10 cubic metres or so at 100 million kelvin might prove possible for seconds, minutes or hours or even days. But it might still prove impossible to operate 90% of the time for extended periods. 
  • Perhaps the unproven energy harvesting and tritium production system might not work.
  • Perhaps the superconductor so critical to the new technology would be damaged by years of neutron irradiation

Or perhaps any one of a large number of complexities inconceivable in advance might prove fatal.

But on the other hand it might just work.

So I now understand why fusion scientists are doing what they are doing. And if their ideas did come to fruition on the 10-year timescale they envision, then fusion might yet still have a contribution to make towards solving the defining challenge of our age.

I wish them luck!




Video#1: Pathway to fusion

Zach Hartwig goes clearly through the MIT plan to make a fusion reactor.

Timeline of Zach Hartwig’s talk

  • 2:20: Start
  • 2:52: The societal importance of energy
  • 3:30: Societal progress has been at the expense of CO2 emissions
  • 3:51: Fusion is an attractive alternative in principle. – but how to compare techniques?
  • 8:00: 3 Questions
  • 8:10: Question 1: What are viable fusion fuels
  • 18:00 Answer to Q1: Deuterium-Tritium is optimal fuel.
  • 18:40: Question 2: Physical Conditions
    • Density, Temperature, Energy confinement
  • 20:00 Plots of Lawson Criterion versus Temperature.
    • Shows contours of energy ration Q
    • Regions of the plot divided into Pointless, possible, and achieved
  • 22:35: Question 3: Confinement Methods compared on Lawson Criterion/Temperature plots
    1. Cold Fusion 
    2. Gravity
    3. Hydrogen Bombs
    4. Inertial Confinement by Laser
    5. Particle accelerator
    6. Electrostatic well
    7. Magnetic field: Mirrors
    8. Magnetic field: Magnetized Targets or Pinches
    9. Magnetic field: Torus of Mirrors
    10. Magnetic field: Spheromaks
    11. Magnetic field: Stellerator
    12. Magnetic field: Tokamak
  • 39:35 Summary
  • 40:00 ITER
  • 42:00 Answer to Question 3: Tokamak is better than all other approaches.
  • 43:21 Combining previous answers: 
    • Tokamak is better than all other approaches.
  • 43:21 The existing pathway JET to ITER is logical, but too big, too slow, too complex: 
  • 46:46 The importance of magnetic field: Power density proportional to B^4. 
  • 48:00 Use of higher magnetic fields reduces size of reactor
  • 50:10 High Temperature Superconductors enable larger fields
  • 52:10 Concept ARC reactor
    • 3.2 m versus 6.2 m for ITER
    • B = 9.2 T versus 5.3 T for ITER: (9.2/5.3)^4 = 9.1
    • Could actually power an electrical generator
  • 52:40 SPARC = Smallest Possible ARC
  • 54:40 End: A viable pathway to fusion.

Video#2: The Affordable, Robust, Compact (ARC) Reactor: and engineering approach to fusion.

Dennis Whyte explains how improved magnets have made fusion energy feasible on a more rapid timescale.

Timeline of Dennis Whyte’s talk

  • 4:40: Start and Summary
    • New Magnets
    • Smaller Sizes
    • Entrepreneurially accessible
  • 7:30: Fusion Principles
  • 8:30: Fuel Cycle
  • 10:00: Fusion Advantages
  • 11:20: Lessons from the scalability and growth of nuclear fission
  • 12:10 Climate change is happening now. No time to waste.
  • 12:40 Science of Fusion:
    • Gain
    • Power Density
    • Temperature
  • 13:45 Toroidal Magnet Field Confinement:
  • 15:20: Key formulae
    • Gain 10 bar-s
    • Power Density ∝ pressure squared = 10 MW/m^3
  • 17:20 JET – 10 MW but no energy gain
  • 18:20 Progress in fusion beat Moore’s Law in the 1990’s but the science stalled as the devices needed to be too big.
  • 19:30 ITER Energy gain Q = 10, P = 3 Bar, no tritium breeding, no electricity generation.
  • 20:30 ITER is too big and slow
  • 22:10 Magnetic Field Breakthrough
    • Energy gain ∝ B^3 and ∝ R^1.3 
    • Power Density ∝ B^4 and ∝ R 
    • Cost ∝ R^3 
  • 24:30 Why ITER is so large
  • 26:26 Superconducting Tape
  • 28:19 Affordable, Robust, Compact (ARC) Reactor. 
    • 500 MW thermal
    • 200 MW electrical
    • R = 3.2 m – the same as JET but with B^4 scaling 
  • 30:30 HTS Tape and Coils.
  • 37:00 High fields stabilise plasma which leads to low science risks
  • 40:00 ARC Modularity and Repairability
    • De-mountable coils 
    • Liquid Blanket Concept
    • FLiBe 
    • Tritium Breeding with gain = 1.14
    • 3-D Printed components
  • 50:00 Electrical cost versus manufacturing cost.
  • 53:37 Accessibility to ‘Start-up” entrepreneurial attitude.
  • 54:40 SP ARC – Soomest Possible / Smallest Practical ARC to Demonstart fusion
  • 59:00 Summary & Questions

Research into Nuclear Fusion is a waste of money

November 24, 2019

I used to be a Technological Utopian, and there has been no greater vision for a Technical Utopia than the prospect of limitless energy at low cost promised by Nuclear Fusion researchers.

But glowing descriptions of the Utopia which awaits us all, and statements by fusion Utopians such as:

Once harnessed, fusion has the potential to be nearly unlimited, safe and CO2-free energy source.

are deceptive. And I no longer believe this is just the self-interested optimism characteristic of all institutions.

It is a damaging deception, because money spent on nuclear fusion research could be spent on actual solutions to the problem of climate change. Solutions which exist right now and which could be implemented inside in a decade in the UK.

Reader: Michael? Are you OK? You seem to have come over a little over-rhetorical?

Me: Thanks. Just let me catch my breath and I’ll be fine. Ahhhhhh. Breathe…..

What’s the problem?

Well let’s just suppose that the current generation of experiments at JET and ITER are ‘successful’. If so, then having started building in 2013:

  • By 2025 the plant should be ready for initial plasma experiments.
  • Unbelievably, full deuteriumtritium fusion experiments will not start until 2035!
    • I could not believe this so I checked. Here’s the link.
    • I can’t find a source for it, but I have been told that the running lifetime of ITER with deuterium and tritium is just 4000 hours.
  • The cost of this experiment is hard to find written down – ITER has its own system of accounting! – but will probably be around 20 billion dollars.

And at this point, without having ever generated a single kilowatt of electricity, ITER will be decommissioned and its intensely radioactive core will be allowed to cool down until it can be buried.

The ‘fusion community’ would then ask for another 20 billion dollars or so to fund a DEMO power station which might be operational around 2050. At which point after a few years of DEMO operation, commercial designs would become available.

So the overall proposal is to spend about 40 billion dollars over the next 30 years to find out if a ‘commercial’ fusion power station is viable.

This plan is the embodiment of madness that could only be advocated by Technological Utopians who have lost track of the reason that fusion might once have been a good idea.

Let’s look at the problems in the most general terms.

1. Cost

Fusion will not be cheap. If we look at the current generation of nuclear fission stations, such as Hinkley C, then these will cost around £20 billion each.

Despite the fact the technology for building nuclear fission reactors is now half a century old, previous versions of the Hinkley C reactor being built at Olkiluoto and Flamanville are many years late, massively over-budget and in fact may never be allowed to operate.

Assuming Hinkley C does eventually become operational, the cost of the electricity it produces will be barely affected by the fuel it uses. More than 90% of the cost of the electricity is paying back the debt used to finance the reactor. It will produce the most expensive electricity ever supplied in the UK.

Nuclear fusion reactors designed to produce a gigawatt of electricity would definitely be engineering behemoths in the same category of engineering challenge as Hinkley C, but with much greater complexity and many more unknown failure modes. 

ITER Project. Picture produced by Oak Ridge National Laboratory [CC BY 2.0 (]

The ITER Torus. The scale and complexity is hard to comprehend. Picture produced by Oak Ridge National Laboratory [CC BY 2.0 (

Even in the most optimistic case – an optimism which we will see is not easy to justify – it is inconceivable that fusion technology could ever produce low cost electricity.

I don’t want to live in a world with
nuclear fusion reactors, because
I don’t want to live in a world
where electricity is that expensive.
Unknown author

2. Sustainable

One of the components of the fuel for a nuclear fusion reactor – deuterium – is readily available on Earth. It can be separated from sea water at modest cost.

The other componenttritium – is extraordinarily rare and expensive. It is radioactive with a half-life of about 10 years.

To  become <irony>sustainable<\irony>, a major task of a fusion reactor is to manufacture tritium.

The ‘plan’ is to do this by bombarding lithium-6 with neutrons causing a reaction yielding tritium and helium.

Ideally, every single neutron produced in the fusion reaction would be captured, but in fact most of them will not be lost. Instead, a ‘neutron multiplication’ process is conceived of, despite the intense radioactive waste this will produce.

3. Technical Practicality

I have written enough here and so I will just refer you to this article published on the web site of the Bulletin of Atomic Scientists.

This article considers:

  • The embedded carbon and costs
  • Optimistic statements of energy balance that fail to recognise the difference between:
    • The thermal energy of particles in the plasma
    • The thermal energy extracted – or extractable.
    • The electrical energy supplied for operation
  • Other aspects of the tritium problem I mentioned above.
  • Radiation and radioactive waste
  • The materials problems caused by – putatively – decades of neutron irradiation.
  • The cooling water required.

I could add my own concerns about neutron damage to the immense superconducting magnets that are just a metre or so away from the hottest place in the solar system.

In short, there are really serious problems that have no obvious solution.

4. Alternatives

If there were no alternative, then I would think it worthwhile to face down all these challenges and struggle on.

But there are really good alternatives based on that fusion reactor in the sky – the Sun.

We can extract energy directly from sunlight, and from the winds that the Sun drives around the Earth.

We need to capture only 0.02% of the energy in the sunlight reaching Earth to power our entire civilisation!

The complexity and cost of fusion reactors even makes fission reactors look good!

And all the technology that we require to address what is acknowledged as a climate emergency exists here and now.

By 2050, when (optimistically?) the first generation of fusion reactors might be ready to be built – carbon-free electricity production could be a solved problem.

Nuclear fusion research is, at its best, a distraction from the problem at hand. At worst, it sucks money and energy away from genuinely renewable energy technologies which need it.

We should just stop it all right now.

Hinkley C: An alternative response

August 1, 2016

My earlier article on Hinkley Point C received a well-conceived and written response that deserves to be somewhere better than a comment page: here it is:

Hi Michael,
I am no economist either but I will make a few comments on your article about the Hinkley C project. Your conclusion is that overall the project is neither the best thing nor the worst thing could do and therefore sort of Ok. This rather equivocal judgement is made on the basis that the ongoing cost (of £1.15 billion p.a. for 35 years) is probably worth the price because it frees the UK government is from any upfront investment or later costs due to failure or delays. I think this is a very naive view.

This project aims to provide at least 7% of the nation’s power. As far as I am aware the UK government has no Plan B to meet this energy gap. This makes the Hinkley Point C scheme simply “too big to fail”. And if it falters or fails it will be for the UK government to salvage it regardless of contracts agreed at the beginning. The deals will be renegotiated when problems arise and the government / nation needs this power so it cannot just walk away or buy an alternative power station off the shelf.

The situation strikes me as analogous to the Private Finance Initiative (PFI) used to build public sector infrastructure for the last few years. This was sold as a wonderful risk free way of financing new hospitals and schools by using the private sector. Certainly new infrastructure has been built (though often not what was wanted) but at enormous cost which will cripple the public sector for decades. The scheme was devised to avoid government borrowing (even though the costs of this are much lower that for the private sector) but still has to be paid for year in & year out. (It is estimated that the UK owes £222 billion to banks & businesses via the PFI. (The Independent 11 April 2015)

By seeking to avoid public borrowing to finance Hinkley C the government has made a political and ideological choice which reduces it’s control (through lack of ownership), inflates the cost (even if kicked a few decades into the future) and does nothing to reduce the risks (because the government / nation really needs this energy so has no choice but to stick with it).

Best Wishes

It is also the case that the UK government has explicitly underwritten £2 billion of costs through the Treasury’s (infrastructure) Guarantee Scheme. This was announced by George Osbourne on a visit to China in September 2015 as an incentive to get the Chinese to invest in the project. EDF itself, in its own press release on the deal refers to “further amounts [being] potentially available in the longer-term.” So there is real chance that the UK government will increase the amount of the project it will explicitly underwrite.

I basically agree with everything you are saying. And if I had had the time I might already have written some of it myself.

However the point of the article was that in narrowly financial terms, this deal isn’t as insane as it is being made to sound.

Concerning Plans A and B, here are some other thoughts.

  • If we want nuclear power, then the current EDF design is one of the very few options available. The real missed opportunity here is that the decision to build was delayed so long that the option for using UK technology was lost.
  • Like you, I find the government’s aversion towards state ownership bizarre. How can it be OK for foreign governments to own our infrastructure, but not the UK government? That is just bonkers. As you say, if this is critical infrastructure then the owners of the infrastructure – the Chinese and French governments – will be able to hold us to ransom in the future.
  • Assuming the project goes ahead, then – taking a positive view – the government will have freed up the capital resources to invest in what I think is the real challenge facing us: integrating energy storage into our generating mix. But that is a story for another evening.

Thanks for your thoughts.



[August 1st  2016: Weight this morning 73.4 kg: Anxiety: Very High]

Road to Nowhere

September 21, 2015

A road to nowhere. This road is 60 metres below the surface of the Finnish peninsula on Olkiluotu and leads to giant silo - the end of the road for low-level and intermediate-level radioactive waste in Finland.

A road to nowhere. This road is 60 metres below the surface of the Finnish island of Olkiluotu and leads to two giant silos – the end of the road for low-level and intermediate-level radioactive waste in Finland.

I wrote last week that one of the things we in the UK need to build in ‘someone’s back yard’ is a Nuclear Waste Repository.

Last week during a progress meeting for the European Metrodecom project, I joined a visit to the site of such a repository in Finland, on the island of Olkiluoto.

Olkiluoto Island houses two working nuclear reactors, each generating approximately 400 MW of electricity for more than 95% of the time. It is also home to the first construction of a new type of reactor which may (or may not) be built at Hinkley Point in the UK. When completed this third reactor should generate approximately 1600 MW of electricity.

But more important than nuclear generation, Olkiluoto is home to Onkalo (meaning ‘Cave’ or ‘Cavern’) the world’s first final disposal site for high-level waste.

The lower levels of Onkalo are still under construction and so sadly we were not able to visit the tunnels 400 m below the surface. But we did visit the 60 m deep repositories for low-level and intermediate-level radioactive waste .

Importantly, these are not ‘storage’ facilities, but represent sites for the final disposal of this waste. When they are full, they will be sealed off and left.

The visit

After three briefings on Olkiluoto in general and Onkalo  in particular, we boarded a bus for a tour of the site, ending up at the entrance to the so-called VLJ repository.

We were asked not to take pictures of the site, but once inside the repository we were told that we could ‘fill up our memory cards’.

We put on obligatory hard hats, and after a large roller-door was raised, we descended on a sloping roadway mined from solid granite.

The tunnel descends, carved out of solid granite.

The tunnel descends, carved out of solid granite.

After 15 minutes or so we reached a large chamber containing two gigantic silos, each about 20 metres in diameter and about 40 metres deep.

Panoramic picture of the Low-level (on the left) and intermediate level (on the right) wast repository.

Panoramic picture of the low-level (on the right) and intermediate level (on the left) waste repository. (Picture from Simon Jerome). Click for larger version.

Above ground, waste is packed into concrete crates about 2 m x 2 m which are then driven along the ‘road to nowhere’ aka the repository. And then lowered by crane into the silo where they are carefully stacked.

Waste is packed into these concrete containers and lowered into the silo

Waste is packed into these concrete containers and lowered into the silo

We weren't allowed to peek into the silos, so this my photograph of a stock photograph of the silo showing the stacks of waste.

We weren’t allowed to peek into the silos, so this my photograph of a stock photograph of the silo showing the stacks of waste.

Most of this waste is ‘operating waste’ from the two existing nuclear reactors on site: typically single-use garments used by maintenance workers and operators, and ion-exchange resin used in maintaining water purity.

The current plan calls for three similar silos to be built to accommodate the decommissioned remains of the two existing reactors at the end of their lives.


By the time that Olkiluoto 1 and 2 reactors are being decommissioned, the Onkalo deep repository will be ready to take all the high-level waste that the reactors have produced over their lifetime.

The fuel rods from the reactors will be removed and placed in water storage for about 10 years – a backlog of fuel awaits the availability of the repository. Bundles of fuel rods are then placed inside a strong cast-iron frame and sealed inside a 4 metre long copper cylinder.

Fuel rod bundles (one visible) are placed in a cast Iron frame (right) chosen for its strength. This is then plced inside a copper cylinder chosen for its corrosion properties.

Fuel rod bundles (one visible) are placed in a cast iron frame (right) which is then placed inside a copper cylinder. Cast iron is chosen for its strength and copper is chosen for its corrosion properties.

Significantly, no attempt is made to reprocess to the fuel. This is somewhat wasteful since useful nuclear material remains unburnt in the fuel rods. But this choice dramatically simplifies the disposal.

Simulated gallery in Onkalo. The tops of several cylinders are visible. When the gallery is full, the space will be back-filled with clay and sealed with a concrete plug.

Simulated gallery in Onkalo. The top of one cylinder is visible and locations of its neighbours can be seen in the distance. When the gallery is full, it will be back-filled with clay and sealed with a concrete plug.

Comparison with the UK

The contrast between the rational Finnish approach and the UK’s ‘let’s put this off and make it someone else’s problem’ approach could not be greater.

Admittedly, Finland’s ‘back yard’ is bigger than the UK’s: they have one tenth our population and twice our land area. And additionally they require a much smaller repository than the UK will require.

However, Finland has begun preparing for disposal of waste before their first generation of reactors have reached the end of their life.

In contrast the UK has been generating about 20% of our electricity from nuclear power for around 50 years, so we have benefited profoundly from nuclear power. Our first generation reactors are now being decommissioned and we have lots of spent fuel and other types of radioactive waste.

But despite spending hundreds of millions of pounds planning, in practical terms, we have done absolutely nothing about safely disposing of nuclear waste – including high level waste.

Some is stored in warehouses, but shamefully a great deal is stored in filthy outdoor pools.

Outdoor storage of nuclear waste at Sellafield

Outdoor storage of nuclear waste at Sellafield.

My visit filled me with a sense of national shame. But overall I feel pleased to have seen this site with my own eyes. Finland has shown the world that safe disposal of nuclear waste is possible, and not at an extravagant cost.

And if they can do it, then why can’t we?


Ready for final disposal

Ready for final disposal

The coolest sandpit in the world.

November 17, 2014

At the end of October 2014 I visited the British Geological Survey, (BGS) in Keyworth, near Nottingham.

I was attending a meeting about ‘geological repositories for either nuclear waste or carbon dioxide.

In the foyer of the BGS  was an ‘interactive sandpit’ in which the height of the sand was monitored by a  Kinect sensor (as used with an X-box games console). From the sand height measurements a computer then calculated an appropriate ‘contour’ image to project onto the sand.

The overall effect was magical and I could have played there for much longer than felt appropriate.

Schematic diagram of the ‘interactive sand pit’. A Kinect sensor determines the sand hight and a computer then calculates an appropriate image to project onto the sand.

The meeting itself was fascinating with a variety of contributors who had completely different perspectives on the challenges.

However what is holding back the construction of a UK repository for nuclear waste is nothing to do with the scientific or engineering challenges: it is a failure of political leadership.

The UK has been a pioneer of nuclear power, the technology through which  we reap the benefits of nuclear power.

But we have been a laggard at cleaning up the radioactive waste generated by the nuclear industry. In this field Sweden and Finland have led the way.

Admittedly their repositories will be smaller than the UK’s, and so easier to construct: I have been informed that the UK’s repository will need to be ‘about the size of Carlisle‘. But it is all do-able.

And when the UK eventually builds a repository, its cost will be inflated by the need to ensure the safety of the repository for a million years. What?…did I just say … one million years? ‘Yes’ I did. And ‘Yes’, that’s bonkers.

This time-scale makes for a number of unique challenges. At the meeting I attended, scientists were confident of the safety for a time-span somewhere between 10,000 and 100,000 years. And frankly, for me that would be good enough.

The ridiculous specifications required to be guaranteed before construction can begin, contrast with the laissez faire attitude towards burning carbon and affecting Earth’s climate. Why do we not have a moratorium on emitting carbon until we can be sure it is safe?

For example one area of uncertainty is the potential significance of microbiological fauna within rocks deep below the Earth, something about which we know very little. Do we have to wait until we can understand the millions of as yet undiscovered microbes before we can proceed?

Of course the main uncertainty – which is ultimately unresolvable – arises from the extreme lengths of time under consideration. This leads to consideration of extremely unlikely scenarios

For example, the Swedish repository company SKB is carrying out extensive research on what will happen to the repository if there is another ice age, and the repository is covered by several kilometres of ice.

First of all, given the problem de jour of global warming, this is frankly unlikely. And secondly, if Sweden is covered by several kilometres of ice, then of course all the people in Sweden would already be dead! At that point the safety of the repository would be frankly a moot point.

You can learn about this research in three short but intensely dull videos here.

Wind versus Nuclear: The real story in pictures

November 3, 2014

Graph showing the electricity generated by nuclear and wind power (in gigawatts) every 5 minutes for the months of September and October 2014. The grey area shows the period when wind power exceeded nuclear power.

Graph showing the electricity generated by nuclear and wind power (in gigawatts) every 5 minutes for the months of September and October 2014. The grey area shows the period when wind power exceeded nuclear power. (Click Graph to enlarge)

For a few days in October 2014,  wind energy consistently generated more electricity in the UK than nuclear power. Wow!

You may have become aware of this through several news outlets. The event was reported on the BBC, but curiously the Daily Mail seems not to have noticed .

Alternatively, you may like me, have been watching live on Gridwatch – a web site that finally makes the data on electricity generation easily accessible.

I was curious about the context of this achievement and so I downloaded the historically archived data on electricity generation derived from coal, gas, nuclear and wind generation in the UK for the last three years. (Download Page)

And graphing the data tells a powerful story of the potential of wind generation – but also of the engineering challenges involved in integrating wind power into a controllable generating system.

The challenges arise from the fluctuations in wind power which are very significant. The first challenge is in the (un)predictability of the fluctuations, and the second challenge is coping with them – whether or not they have been predicted. Both these challenges will grow more difficult as the fraction of wind energy used by the grid increases over the next decade.

As an example, consider in detail an event earlier in October shown in the graph at the top of the page

Graph showing the electricity generated by nuclear and wind power (in gigawatts) every 5 minutes for the months of September and October 2014. The grey area shows the period when wind power exceeded nuclear power.

Detail from the graph at the top of the page showing how earlier in October, wind power went from an impressive 6 GW to less than 1 GW in a period of around 18 hours . (Click Graph to enlarge)

The grid operators have a wind forecast running 6 to 24 hours ahead and would have planned for this. The forecasts are typically accurate to about 5% and so at the high end that amounts to a margin of error of 0.3 GW – which is within the reserves that the grid can cope with routinely.

However the fluctuations in wind power are becoming larger as the amount of wind power increases. The graph below shows the monthly averages of electricity produced by Wind and Nuclear since May 2011. Also shown in pink and light blue are the data (more than 300,000 of them!) taken every 5 minutes.

Monthly averages of electricity produced by Wind and Nuclear since May 2011. Also shown in grey are the data (more than 300,000 of them!) taken every 5 minutes. It is clear that the fluctuations in wind power are large - and getting ever larger. (Click Graph to enlarge)

Monthly averages of electricity produced by Wind and Nuclear since May 2011. Also shown in pink and light blue are the data (more than 300,000 of them!) taken every 5 minutes. It is clear that the fluctuations in wind power are large – and getting ever larger. (Click Graph to enlarge)

Incorporating wind energy is a real engineering challenge which costs real money to solve. Nonetheless, as explained in this excellent  Royal Academy of Engineering report, we expect capacity to double to ~20 GW by 2020, and to at least double again by 2030. So these problems do need to be solved

Because wind-generated electricity supply does not respond to electricity demand, as the contribution of wind energy grows we will reach two significant thresholds.

  • When demand is high, unanticipated reductions in wind-generated supply could exceed the margins within which the grid operates.
  • When demand is low, unanticipated increases in wind-generated supply could exceed the base supply from nuclear power which cannot be easily switched off

These challenges will require both economic and engineering adaptations. At the moment, because the marginal cost of wind power is so low, we basically use all the wind power that is available.

However, it is possible to ‘trim’ wind turbines so that they do not produce their maximum output. In a future system with 40 GW of wind generating capacity, we might value predictability  and controllability over sheer capacity. Then as the wind falls, the turbines could adjust to try to keep output constant.

These challenges lie ahead and are difficult but entirely solvable. And their solution will be essential if we really want to phase out fossil fuels by 2100.

But for the moment wind is providing on average about 2 GW of electrical power, which is around 6% of UK average demand. This is a real achievement and as a country we should be proud of it.

Perhaps someone should tell the Daily Mail.

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