Archive for the ‘The Future’ Category

Hydrogen in the UK

May 23, 2023

Isambard Kingdom Brunel

Friends, on Monday I visited a Brunel University Hydrogen Event. This meant getting up(!) and travelling far beyond the borders of Teddington on TWO buses – so when I arrived in Uxbridge at  11:00 a.m. it had already been an exciting day for a retiree like me.

It was the kind of event I might have attended when I worked at NPL, but when I worked for NPL I would have gone along to promote something, or to give a talk. So it was liberating to be there with no agenda: I went with the simple goal of educating myself. And I did learn a thing or two. So I thought I would jot down a few of the things I learned.

Thing#1: Electrolysers

I learned that ITM Power is one of the world’s leading manufacturers of electrolysers, with a capacity to manufacturer around 1 GW of electrolysers per year – in the UK! Remember that only hydrogen manufactured using electrolysis powered by renewable electricity has the capability to create green hydrogen with practically zero CO2 emissions.

Thing#2: Fuel Cell Vehicles

I learned that many people are still very keen on fuel-cell powered vehicles. Talking with a fellow delegate I pointed out the relative inefficiency of using fuel cell vehicles (FCVs) compared to battery electric vehicles (BEVs) – you can read my previous article on this here. However the delegate was dismissive of efficiency as a metric, whereas I consider it to be overwhelmingly important.

Remember that if we begin with 100 kWh of renewable electricity, after creating hydrogen we will have only 80% of the energy available, and only half of that makes it to the wheels of the vehicle – so only 40% of the initial energy is useful. However if we use that renewable electricity to charge a battery and discharge it, around 85% of the energy is useful.

What this means is that to run a fleet of vehicles using hydrogen fuel cells requires more than twice the renewable electricity resource. In the future we may have an excess of renewable electricity, but this will not be the case for many years.

The delegate explained that efficiency was only relevant if a BEVs had the capacity of a FCV, by which I think they were referring to power and range. So the delegate thought that fuel-cell drive trains would ‘win’ in this area. And it may be that for large vehicles or trains, there may be a niche for fuel cells, but I remain sceptical.

Things#3: Hydrogen Combustion Engines 

To my surprise some people are still pursuing hydrogen combustion for motive applications.

Some people are working on retrofit apparatus for existing diesel engines and some are working on radical new concepts which would operate at very high temperatures and have a thermodynamic efficiency approaching 70% compared with about 25% for a conventional  Internal Combustion Engine (ICE) car i.e. ICE cars throw away 75% of the energy of combustion as heat.

A 3-D printed model of a hydrogen internal combustion engine.

I would have dismissed this completely, but Japanese manufacturers are still clinging to the idea (News Story 18 May 2023) and one of the world’s leading manufacturer’s of construction equipment – JCB – is planning on using such engines in their vehicles.


Click on Image for a larger version. The discussion panel consisting of (from Left to Right): Ben Madden, Rita Wadey, Ben Todd and the keynote speaker, Graham Cooley.

The keynote presentation was given by Dr. Graham Cooley, CEO of ITM-Power, and I found it quite inspiring. I won’t try to précis the talk but instead just note one point.

He noted that technological cultures are built on both molecules and electrons. Historically we have started with hydrocarbon molecules (coal, oil and gas), and burned these molecules to make electricity. But in the current energy transformation, this pattern is being reversed. For a green technological culture, we start with renewable electricity and use that to make molecules – specifically hydrogen – which then seeds the synthesis of larger molecules. I guess this seems obvious to a man who runs an electrolyser firm!

The discussion panel was fascinating, consisting of an investor, an entrepreneur and a policy specialist. Collectively their comments painted a picture of an ever-changing forest of complex incentives, indecision in government, and continuing lack of support. In short, nothing new.

When I asked the panel’s views about heating, one panel member pointed out the astonishing extent and complexity of the gas distribution network, and commented that “...if they can’t find something to put in their pipes, they’re toast!“. I think this explains the desperate efforts of the gas companies to promote hydrogen for home heating – something which would be a disaster for the UK.


Friends, I went along to this event to learn, and I learned that there is a lot of experience in a range of hydrogen technologies in the UK and that Brunel University is full of smart, business-focussed engineers.

But overall I was surprised at the continued focus of research on hydrogen for transport. I wish all the companies involved well, but I didn’t understand their enthusiasm.

I didn’t see any work on hydrogen for aviation, and as I see it, hydrogen for terrestrial transport will only be a niche market – heavy equipment and large lorries. And this niche market is a market that will inevitably contract as battery technology improves, providing vehicles with ever improving specifications in terms of range, load and cost.

But what do I know? Time will tell.



Fusion is a failure.

September 21, 2022

Friends, I listened with astonishment this morning to a Radio 4 science-tainment program called The Curious Cases of Rutherford and Fry: The Puzzle of the Plasma Doughnut.

  • I think it may have been the worst science radio program I have ever heard.

Despite fusion’s seventy years of continuous world-wide failure, the program repeatedly claimed that fusion ‘could supply limitless clean electricity‘. This was mentioned in hallowed terms as though there were no other technologies which can already do that – such as solar power or wind turbines.

The program somehow contrived to assume that ‘success’ in this noble struggle was certain – and that after success was achieved it would then ADDITIONALLY provide the power source of our next generation of interstellar rockets, and be available in miniature versions.

Anyone listening without specialist knowledge would have no idea that this entire endeavour is a colossal waste of time of money which will, in all likelihood, never result in a single electron being put onto the grid.

Astonishingly for a program nominally celebrating ‘curiosity’, the hosts Rutherford and Fry (R&F) failed to ask a single challenging question in the 30 minutes allotted to this issue. They just swallowed PR tidbits.

Here are three questions they might have asked:

Q#1: How much will fusion electricity cost?

Since they are looking to supply ‘limitless’ energy, R&F might have asked how much the electricity supplied by these fusion reactors would cost compared to the cost of renewable technologies such as solar or wind?

Of course, nobody knows the price of a product which won’t exist for decades and indeed may never exist. But it is inconceivable that it will cheaper than solar or wind.

A ball park guess would be that it might be around the same price as conventional nuclear power. Or more.

A fusion power station would use technology which was dramatically more complex and expensive than a conventional nuclear power station, and would likely to struggle in early generations to maintain 95% up-time.

And amazingly after all the hard work, since it’s fundamental output is heat – it would still throw away roughly 67% of the energy generated! Why? Because even nuclear fusion cannot beat the second law of thermodynamics that governs the extraction of electricity from hot gases.

In other words: the electricity produced will be very expensive.

Q#2: Tritium: Where will you get it from?

All fusion reactors face myriad technical challenges – I won’t go into them all here – and it would have been nice if perhaps R&F had mentioned one or two of these difficulties.

For example all fusion reactors planned aim to fuse two isotopes of hydrogen called deuterium (D) and tritium (T). Deuterium is available in vast quantities in seawater, but Tritium is amongst the rarest and most expensive radioactive substances on Earth. And fusion reactors require a lot of it. A 100 MWe fusion electricity power plant – a very small generator equivalent to say 10 modern wind turbines – would require roughly 5 kg of tritium per month. A year’s supply for a single reactor is likely more than all the tritium which currently exists on Earth.

Fusion engineers do have plans to use the fusion reactor to create tritium as part of routine reactor operation. But it is not at all obvious to me that a practical solution even exists.

Some mention of the ‘Tritium Problem’ or similar technical problems would have been nice.

Q#3: Timing: Can this help with the climate emergency?

The fusion-industry PR representative on the program said it was very important that they were ready to deploy reactors in 2050 to ‘contribute to Net Zero‘.

This is a misunderstanding. If by 2050 we have reached ‘Net Zero’, then we won’t need fusion! We will – by definition – be operating our economy without emitting CO2 and another source of expensive electricity will likely not find any market at all. Unless it’s really cheap – but electricity generated from a fusion reactor is unlikely to be ‘cheap’.

In fact, the climate emergency is right now and fusion has nothing to offer. Spending resources on fusion research now is channelling money away from things which could actually be helping humanity in the grim decades between now and 2050.

How does trash like this get on the air?

I honestly don’t know, but perhaps R&F left a clue in the additional ‘bonus’ material at the end of on-line version of the program.

After recounting an anecdote, R chuckled and said his mate Steve Cowley was someone important at a UK research lab investigating fusion and had got him a tour of the facility.

His ‘mate’ Steve would actually be Sir Steven Charles Cowley Kt FRS FREng FInstP, the CEO of the UK Atomic Energy Authority.

And it just felt like I was listening to members of a chumocracy discussing how clever they were and what whizz friends they had.

Curiously, you can actually hear R‘s mate Steve on another Radio 4 program, In our Time which discussed fusion in 2014 (link). Sadly, even this program provides only the weakest of sceptical voices.

Why am I writing this?

Normally, if I can’t find something good to write about something, I try to write nothing.

But fusion populists just take such silence as carte-blanche to propagate their delusional propaganda about ‘endless cheap renewable electricity’ and suggest that they are climate-change friendly.

In these coming decades, it is really important that we keep our eyes on ‘the prize’, and ‘the prize’ is not nuclear fusion.

In these decades we will face summers and winters of climatic extremes which will involve multiple humanitarian catastrophes.

‘The prize’ is avoiding even worse disasters in the future, and we will win ‘the prize’ by reducing carbon dioxide emissions now, as rapidly as we possibly can. By now, I mean today, and tomorrow, not next week or next year. Now.

Betting on fusion technology which has failed for decade after decade is nothing but a distraction.

So don’t be distracted: fusion is a serial failure.

Previous articles I have written about Fusion

Below is a selection of articles I written about this topic previously. Of these articles, the July 2020 article is the most-nuanced, trying to emphasise why fusion scientists are still clinging on.

Nuclear Fusion is Irrelevant (February 2022)

Are fusion scientists crazy? (July 2020)

Fusion Research is STILL a waste of money(June 2020)

Research into Nuclear Fusion is REALLY a waste of money. (December 2019)

Research into Nuclear Fusion is a waste of money (November 2019)

Controlled Nuclear Fusion: Forget about it (October 2013)

What else can I do?

July 14, 2022

Friends, while writing the slides for my recent talk to teenagers, I became very aware of the awfulness of the future facing the children I was addressing – and my own children who are only around 8 years older.

This awareness took the form of something between panic and gloom. And it caused me to reflect on my own efforts to reduce carbon dioxide emissions, and to ask myself “What else could I do?”.

In case you are short of time I will summarise my conclusion here: I have eliminated most of carbon emissions from my life that can be cut by simply spending money! To go further, requires significant lifestyle changes. And maybe trying harder to influence other people.

What am I doing already?

As summarised on the ‘My House‘ pages of this blog and this video, I have spent most of my life-savings (aka my ‘Pension Tax-Free Lump Sum’ of around £60,000) on steps to reduce carbon dioxide emissions from my house in Teddington.

Briefly, the money has been spent on:

  • Triple Glazing & External Wall Insulation reducing the heating demand by half.
  • 12 Solar Panels generating ~3,500 kWh/year of electricity, Together with a battery, this is enough to take us off-grid for roughly 90 days a year and to substantially reduce the use of grid electricity in all but the darkest months.
  • A heat pump eliminating the use of gas for heating.

Altogether, these steps have reduced CO2 emissions associated with the house by around 80%, from 3.7 tonnes per year to about 0.8 tonnes per year.

And our lifestyle has not been impacted at all: in fact the house is more comfortable: warmer in winter and cooler in summer – cooled with solar-powered air conditioning.

These carbon emissions are real reductions of emissions – actions that result in no CO2 being emitted into the atmosphere when compared with the alternative of not taking these actions. And after the carbon payback period, emissions associated with the house will be around 3 tonnes less per year than they would have been.

But in this calculation I have not included three other things that could notionally be included.

  • Exports: Each year the house exports ~900 kWh of electricity to the grid. One can argue about how much this reduces emissions from other people’s use of electricity.  But this probably reduces emissions by between 0.2 to 0.4 tonnes per year.
  • Direct Air Capture: Each month I pay the Climeworks foundation £40 and in return they promise to directly capture 50 kgCO2 from the air and turn it into carbonate rock deep beneath the surface of Iceland. I really don’t know how well-validated this process is, but Climeworks promise that within 6 years of my payment, they will permanently remove 600 kgCO2/year from the atmosphere ‘in my name’. Notice this is not ‘offsetting’ which I believe to be tantamount to fraud.
  • Wind Farm: Earlier this year my wife & I paid Ripple £2,000 to buy a share of an 8-turbine wind farm they plan to build in Scotland. This share is sufficient to generate roughly 3,500 kWh/year of electricity – 100% of the electricity the house draws from the grid each year. It’s scheduled for completion in November 2023 and from that point onwards, the carbon emissions nominally associated with the house will fall by very roughly 600 kgCO2/year.

In accounting terms, this means that – as the graph below shows – the household could possibly be classified as ‘carbon negative’.

Click on image for a larger version. The graph shows cumulative carbon dioxide emissions from the house up to the year 2040 based on several different assumptions. The red line shows expected emissions if I had not done any work on the house. The green line shows the effect of those works. The dotted black line shows the effect of my paying for Direct Air Capture of CO2. And the dotted blue line shows the effect of my purchase of a fraction of a ‘Ripple’ Wind Farm. The carbon embodied in the modifications to the house is now (July 2022) just about paid off.

What else could I do?


There is only limited scope for further work on the house. Installing underfloor insulation could reduce the heating requirements by perhaps another 20%. And there is room for a few more solar panels and more batteries. However neither change would alter the graph above dramatically.

Additionally I am keen not to adopt a techno-utopian stance – forever consuming more of the latest tech to enable me to humble-brag about some sexy piece of equipment.

So what about emissions from other aspects of my life – Transport, Consumption and Pensions.


My wife and I still own and drive a car and we drive around 3,500 miles/year which corresponds to just over 0.8 tonnes of CO2 emissions.

It pains me every time I drive – wasting 70% of the energy in the petrol and emitting CO2 directly. However, although my wife might be able to afford an electric car, with our low annual mileage, the 10 tonnes of CO2 emitted during the manufacture of an EV is hard to justify.

Probably our the best strategy is just to reduce the amount we drive – cycling and using public transport even more than we do.

I guess at some time I will be obliged to travel by air again – but until that becomes necessary, I will simply try to avoid this. Although the idea of international travel is intermittently attractive (particularly to my wife), to me it seems too appalling to emit tonnes of CO2 in an afternoon on nothing more than a whim!


I have given up taking milk in my tea (and coffee) and this has resulted in our using 1 litre of milk less each week – saving 50 litres per year. Using figures from Our World in Data, this – apparently – reduces our annual carbon footprint by ~ 0.15 tonnes! Other sources suggest that UK milk does not have such high emissions, and the avoided emissions are more like 0.075 tonnes (75 kg). Whatever the actual answer is, I have made the switch and I don’t intend to switch back. And even 75 kg per year up to my planned date of death is 18 x 75 = 1,350 kg CO2.

My wife and I have both changed our diet significantly in recent years: reducing beef purchases to zero, and only eating other meats perhaps once a week. We eat vegetables and salads much more than we used to, including food from my wife’s allotment which has low associated ‘food miles’. However, we still eat eggs and cheese.

I am trying to buy fewer ‘things’. And as my perspective has slowly shifted, I have realised I really need very few new objects.


As I lamented in an earlier article, the money invested on my behalf by Legal and General and USS probably generates many tonnes of CO2 – probably more than all the other categories combined.

After writing that article, a correspondent suggested to me that considering emissions from my pension savings was double-counting. In other words, I was counting emissions from say petrol purchases already under the ‘travel’ category, so counting those again as part of a share portfolio that probably includes oil companies was not consistent. This is a fair point. The emissions associated with an oil company’s activities can either be assigned to the consumers of their products, or the shareholders, but not both.

However, my money is still invested in ways I would not personally choose. But I feel so unsure of myself as an investor that I am not confident that switching investment funds would result in an improvement.


Aside from emitting as little CO2 as I can, I also want to live a life which includes joyful activities and is not a relentless drudge.

But it seems that I am approaching the limits of what I can do personally to live a life with minimal emissions of carbon dioxide.

There are still actions I can take, – and I will – but at this point it seems that probably the most significant thing I can do is to try to influence other people to take action to reduce their carbon dioxide emissions.

Mmmmm. I will have a think about how best to do that.

Will aviation eventually become electrified?

March 2, 2022

Friends. I ‘have a feeling’ that aviation will eventually become electrified. At first sight this seems extraordinarily unlikely, but I just have this feeling…

Obviously, I could just be wrong, but let me explain my thinking.


The current technology for aviation – jet engines on aluminium/composite frames with wings – relies on the properties of jet fuel – kerosene.

There are two basic parameters for aviation ‘fuel’.

  • Energy density – which characterises the volume required to carry fuel with a certain energy content. It can be expressed in units of megajoules per litre (MJ/l).
  • Specific energy – which characterises the mass required to carry fuel with a certain energy content. It can be expressed in units of megajoules per kilogram (MJ/kg).

Wikipedia have helpfully charted these quantities for a wide range of ‘fuels’ and this figure is shown above with five technologies highlighted:

  • Lithium batteries,
  • Liquid and Gaseous Hydrogen,
  • Kerosene and diesel.

Click on image for a larger version. Chart from Wikipedia showing the specific energy and energy density of various fuels enabled energy technologies.

A general observation is that hydrocarbon fuels  have a much higher density and specific energy than any current battery technology. Liquid Hydrogen on the other hand has an exceptionally high specific energy, but poor energy density: better than batteries but much worse than hydrocarbon fuels.

Lessons from the EVs transition:#1

I think the origin of my feeling about the aviation transition stems from the last 20 years of watching the development of battery electric vehicles (BEVs). What is notable is that the pioneers of BEVs – Tesla and Chinese companies such as Xpeng or BYD – are “all in” on BEV’s – they have no interest in Internal Combustion Engine (ICE) vehicles or hybrids. They have no legacy market in ICE vehicles to protect.

‘Legacy Auto’ (short hand for VW, GM, Ford, Toyota etc) had poked their toe in the waters of alternative drive-trains quite a few years ago. GM’s Volt and Bolt were notable and Toyota’s Mirai hydrogen fuel cell car was a wonder. But Legacy Auto were comfortable manufacturing ICE vehicles and making profits from it, and saw these alternative energy projects as ‘insurance’ in case things eventually changed.

As I write in early 2022, all the legacy auto makers are in serious trouble. They can generally manufacture BEVs, but not very well – and none of them are making money from BEVs. Aside from Tesla, they have very poor market penetration in China, the world’s largest EV car-market. In contrast Tesla are popular in China and America and Europe and make roughly 20% profit on every car they sell.

So one lesson from the BEV transition is that the legacy industry who have invested billions in an old technology, may not be the pioneers of a new way of doing things.

Lessons from the EVs transition:#2

How did BEV’s overcome the awesome advantages of hydrocarbon fuels over lithium batteries in terms of energy density and specific energy?

First of all, ICEs throw away about 75% of their advantage because of the way they operate as heat engines. This reduces their energy density advantage over batteries to just a factor 10 or so.

Secondly, there is the fact that ICE cars contain many heavy components – such as engines, gearboxes, and transmissions that aren’t needed in a BEV.

But despite this, BEV cars still generally have a weight and volume disadvantage compared to ICE cars. But this disadvantage has been overcome by careful BEV-specific design.

By placing the large, heavy, battery pack low down, designers can create pleasant vehicle interiors with good handling characteristics. And because the ability to draw power rapidly from batteries is so impressive, the extra mass doesn’t materially affect the acceleration of the vehicle.

EV range is still not as good as a diesel car with a full tank. But it is now generally ‘good enough’.

And once EVs became good enough to compete with ICE vehicles, the advantages of EVs could come to the fore – their ability to charge at home, low-running costs, quietness, potential low carbon emissions and of course, zero in situ emissions.

And significantly, BEV’s are now software platforms and full electronic control of the car allows for some capabilities that ICE vehicles will likely never have.

Lessons from the EV transition:#3

Despite Toyota’s massive and long-term investment in Hydrogen Fuel Cell (HFC) cars, it is now clear that hydrogen will be irrelevant in the transition away from ICE vehicles. Before moving on to look at aviation, it is interesting to look at why this is so.

The reason was not technological. HFC cars using compressed hydrogen fuel were excellent – I have driven one – with ranges in excess of 320 km (200 miles). And they were excellent long before BEVs were excellent. But the very concept of re-fuelling with hydrogen was the problem. Hydrogen is difficult to deal with, and fundamentally if one starts with a certain amount of electrical power – much less of it gets to the wheels with a HFC-EV than with a BEV.

The very idea of a HFC car is – I think – a product of imagining that there would be companies akin to petrochemical companies who could sell ‘a commodity’ in something like the way Oil Companies sold petrol in the 20th Century. BEV’s just don’t work that way.

Interestingly, the engineering problems of handling high-pressure hydrogen were all solved in principle. But this just became irrelevant.

Cars versus Aeroplanes

So let’s look at how energy density and specific energy affect the basic constraints on designs of cars and aeroplanes.

50 litres of diesel contains roughly 1,930 MJ of energy. The table below shows the mass and volume of other fuels or batteries which contains this same energy.

Mass (kg) Volume (l)
Kerosene 45 55
Diesel 42 50
Hydrogen HP 14 364
Hydrogen Liquid 14 193
Lithium Battery 4,825 1,930

We see that batteries look terrible – the equivalent energy storage would require 4.8 tonnes of batteries occupying almost 2 cubic metres! Surely BEVs are impossible?!

But as I mentioned earlier, internal combustion engines waste around 75% of their fuel’s embodied energy in the form of heat. So a battery with the required stored energy would only need 25% of the mass and volume in the table above.

Mass (kg) Volume (l)
Lithium Battery 1206 483

So, we see that the equivalent battery pack is about a tonne heavier than the fuel for a diesel car.

But this doesn’t include the engine required to make the diesel fuel work. So one can see how by clever design and exploiting the fact that electric motors are lighter than engines, one can create a BEV that, while heavier than an ICE car, is still competitive.

Indeed, BEVs now outperform ICE cars on almost every metric that anyone cares about, and will continue to get better for many years yet.

Let’s do the same analysis for aeroplanes. A modern jet aeroplane typically carries 100 tonnes of kerosene with an energy content of around 43 x 105 MJ. This is sufficient to fly a modern jet (200 tonnes plus 30 tonnes of passengers) around 5,000 miles or so.

The table below shows the mass and volume other fuels or batteries which contains this same energy. Notice that the units are no longer kilograms and litres but tonnes and cubic metres.

Mass (tonnes) Volume (m^3)
Kerosene 100 123
Diesel 94 111
Hydrogen HP 31 811
Hydrogen Liquid 31 430
Lithium Battery 10,750 4,300

Now things look irrecoverably impossible for batteries! The batteries would weigh 10,000 tonnes! And occupy a ridiculous volume. Also, turbines are more thermodynamically efficient than ICEs, so assuming say 50% efficiency, batteries would still weigh ~5,000 tonnes and occupy 2,000 m3.

Even with a factor 10 increase in battery energy density – which is just about conceivable but not happening any time soon – the battery would still weigh 1,000 tonnes!.

Does it get any better for shorter ranges? Not much. Consider how much energy is stored in 10 tonnes of kerosene (~43 x 104 MJ). This is sufficient to fly a modern jet – weighing around 50 tonnes unladen and carrying 20 tonnes of passengers around 500 miles or so.

Mass (tonnes) Volume (m^3)
Kerosene 10 12
Diesel 9 11
Hydrogen HP 3 81
Hydrogen Liquid 3 43
Lithium Battery 1,075 430

Even assuming 50% jet efficiency, batteries with equivalent energy would still weigh ~500 tonnes and occupy 200 m3. Even after a factor 10 increase in battery energy density, things still look pretty hopeless.

So can we conclude that battery electric aviation is impossible? Surprisingly, No.

And yet, it flies.

Jet engines burning kerosene have now reached an astonishing state of technological refinement.

But jet engines are also very expensive, which makes the economics of airlines challenging. And despite improvements, jets are also noisy. And of course, they emit CO2 and create condensation trails that affect the climate.

In contrast, electric motors are relatively cheap, which means that electric aeroplanes (if they are possible) would be much cheaper, and require dramatically less engine maintenance. These features are very attractive for airlines – the people who buy planes. And the planes would be quiet and have zero emissions – attractive for people who fly or live near airports.

And several companies are seeking to exploit these potential advantages. Obviously, given the fundamental problem of energy density I outlined above, all the projects have limitations. Mostly the aeroplanes proposed have limited numbers of passengers and limited range. But the companies all impress me as being serious about the engineering and commercial realities that they face. And I have been surprised by what appears to be possible.

Here are a few of the companies that have caught my attention.


In the UK, Rolls Royce and partners have built an impressive single-engined aircraft which flies much faster than equivalent ICE powered aircraft.

Their Wikipedia page states the batteries have a specific energy of 0.58 MJ/kg, about 50% higher than I had assumed earlier in the article. The range of this plane is probably tiny – a few 10’s of kilometres – but this number will only increase in the coming years.

This aeroplane is really a technology demonstrator rather than a seedling commercial project. But I found it striking to see the plane actually flying.

In Sweden, Heart Aerospace have plans for a 19-seater short-hop passenger craft with 400 km of range. Funded by Bill Gates amongst others, they have a clear and realistic engineering target.

In an interview, the founder explained that he was focussing on the profitability of the plane. In this sense the enterprise differs from the Rolls Royce project. He stated that as planned, 2 minutes in the air will require 1 minute of re-charging. He had clear markets in mind in (Sweden, Norway, and New Zealand) where air travel involves many ‘short hops’ via transport hubs. And the expected first flights will be soon – 2025 if I have it correct.

In Germany, Lillium are building innovative ducted-fan planes. Whereas Heart’s planes and Rolls Royce’s demonstrator projects are conventional air-frames powered by electric motors, Lillium have settled on completely novel engineering possibilities enabled by electrical propulsion technology. Seeing their ‘Star Wars’ style aircraft take off and land is breathtaking.

Back in the UK, the Electric Aviation Group are advertising HERA as a 90-seater short route airliner with battery and hydrogen fuel-cell technology (not a turbine). This doesn’t seem to be as advanced as the other projects I have mentioned but illustrates the way that different technologies may be incorporated into electric aviation.

What about Hydrogen Turbines?

Legacy Aeromaker Airbus are advertising development of a hydrogen turbine demonstrator. It’s a gigantic A380 conventional jet airliner with a single hydrogen turbine attached. (Twitter video)

Stills from a video showing how the hydrogen turbine demonstrator will work. A single turbine will attached to kerosene driven aeroplane by 2035.

The demonstrator looks very clever, but I feel deeply suspicious of this for two sets of reasons: Technical reasons and ‘Feelings’.


  • Fuel Volume: To have the same range and capabilities as an existing jet – the promise that seems to be being advertised – the cryogenic (roughly -250 °C) liquid hydrogen would occupy 4 times the volume of the equivalent kerosene. It likely could not be stored in the wings because of heat leakage, and so a big fraction of the useful volume within an aeroplane would be sacrificed for fuel.
  • Fuel Mass: Although the liquid hydrogen fuel itself would not weigh much, the tanks to hold it would likely be much heavier than their kerosene equivalents. My guess is that that there would not be much net benefit in terms of mass.
  • Turbine#1: Once the stored liquid hydrogen is evaporated to create gas, its energy density plummets. To operate at a similar power level to a conventional turbine, the volume of hydrogen entering the combustion chamber per second will have to be (very roughly) 40 times greater.
  • Turbine#2: Hydrogen burns in a different way from kerosene. For example embrittlement issues around the high pressure, high temperature hydrogen present at the inlets to the combustion chamber are likely to be very serious.
  • I don’t doubt that a hydrogen turbine is possible, but the 2035 target advertised seems about right given the difficulties.
  • Performance: And finally, assuming it all works as planned, the aircraft will still emit NOx, and will still be noisy.


  • I feel this a legacy aero-maker trying to create a future world in which they are still relevant despite the changed reality of climate crisis.
  • I suspect these engines assuming the technical problems are all solved –  will be even more expensive than current engines.
  • I feel the timeline of 2035 might as well be ‘never’. It allows Airbus to operate as normal for the next 13 years – years in which it is critical that we cut CO2 emissions.
  • I suspect that in 13 years – if electric aviation ‘gets off the ground’ (sorry!) – then it will have developed to the point where the short-haul end of the aviation business will be in their grasp. And once people have flown on smaller quieter aircraft, they will not want to go back.
  • Here is Rolls Royces short ‘Vision’ video.

And so…

I wrote this article in response to a Twitter discussion with someone who was suggesting that cryogenic liquid-hydrogen-fuelled jets would be the zero-emission future of aviation.

I feel that that the idea of a cryogenic hydrogen aircraft is the last gasp of a legacy engine industry that is trying to stay relevant in the face of a fundamentally changed reality.

In contrast, electrical aviation is on the verge of becoming a reality: planes are already flying. And motors and batteries will only get better over coming decades.

At some point, I expect that electrical aviation will reach the point where its capabilities will make conventional kerosene-fuelled aeroplanes uneconomic, first on short-haul routes, and then eventually – though I have no idea how! – on longer routes.


…I could be completely wrong.

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.


The Last Artifact

October 5, 2020

A long long time ago (May 2018) in a universe far far away (NPL), I was asked to take part in a film about the re-definition of four of the seven SI base units: The Last Artifact

The team – consisting of director Ed Watkins, videographer Rick Smith and sound recordist Parker Brown – visited my lab and I spent a happy afternoon and morning chatting.

I later heard that a version of the film was shown to VIPs in May 2019 when the kilogram, kelvin, candela and ampere were re-defined, and I was told that some my words had made the cut!

But then the film disappeared!

I wrote to director Ed Watkins earlier this year and he shared a version with me privately, and I was impressed. But there was still no version to share.

I am writing this because a set of clips have now emerged which will hopefully be relevant for classroom use.

I don’t think the clips individually make as much sense as the film as a whole because they lack the continuing narrative that the film provides. But they are still beautiful and provide views of otherwise unseen laboratories and artifacts and people.

Personally, I was shocked to see myself on film – so shocked I found it difficult to see the rest of the film clearly. But as my shock subsided, I grew to like the film.

This film is a not made for people like me, and it is not the film I would have made. Rather it is a film for non-scientists and schoolchildren. It is by turns gorgeous, colourful, engaging, and humorous. And when I showed it to a UK Science TV producer they said it worked for them!

The colour and music and sound quality are outstanding and make watching it a simple pleasure. I recall at the time noting that they were shooting at ‘8K’ resolution when I had only ever heard of ‘4k’: Now I know why!

This page contains links to all 12 films or you pick from the list below – the links are in the film’s title: Films with a red asterisk (*) feature me! (sometimes just my voice).Clips

Film 1: (Re)Defining The Universe  (1 miniute 55 seconds)

An introduction to what is meant by an ‘artifact’ ending with a beautiful shot of the international prototype of the kilogram itself.

Film 2 *: What is Metrology? (3 minutes 33 seconds)

An introduction the International Bureau of Weights and Measures and its role in the international measurement system: the SI.

Film 3 *: Metrologists (1 minutes 18 seconds)

Metrologists speak!.

Film 4 *: Measurement: System International (3 minutes 14 seconds)

An introduction the SI.

Film 5 *: The Hunk of Metal (3 minutes 33 seconds)

An introduction the international prototype of the kilogram.

Film 6 *: The History of Measurement (7 minutes 10 seconds)

A nice summary of the history of measurements.

Film 7 *: Redefinition and Fundamental Constants (2 minutes 48 seconds)

The idea of moving away from artifacts..

Film 8 : Avogadro’s Constant  (1 minutes 24 seconds)

One option for re-defining the kilogram

Film 9 : The Avogadro Sphere (2 minutes 37 seconds)

How to make an Avogadro Sphere.

Film 10 : Planck’s Constant (2 minutes 16 seconds)

Some chit chat about the Planck Constant.

Film 11 : Watt Balance (4 minutes 29 seconds)

The concept of weighing with electricity using a Kibble Balance. A chance to hear Ian Robinson speak.

Film 12 *: The Next  Frontier (3 minutes 31 seconds)

What changes after re-definition of the SI units?

I hate it when it’s too hot

August 7, 2020


I find days when the temperature exceeds 30 °C very unpleasant.

And if the night-time temperature doesn’t fall then I feel doubly troubled.

I have had the feeling that such days have become more common over my lifetime. But have they?

The short  summary is “Yes”. In West London, the frequency of days on which the temperature exceeds 30 °C has increased from typically 2 days per year in the 1950’s and 1960’s to typically 4 days per year in the 2000’s and 2010’s. This was not as big an increase as I expected.

On reflection, I think my sense that these days have become more common probably arises from the fact that up until the 1980’s, there were many years when such hot days did not occur at all. As the graph at the head of the article shows, in the 2010’s they occurred every year.

Super-hot days have now become normal.

You can stop reading at this point – but if you want to know how I worked this out – read on. It was much harder than I expected it would be!

Finding the data

First, please notice that this is not the same question as “has the average summer temperature increased?”

A single very hot day can be memorable but it may only affect the monthly or seasonal average temperatures by a small amount.

So one cannot merely find data from a nearby meteorological station….

…and plot it versus time. These datasets contain just the so-called ‘monthly mean’ data. i.e.. the maximum or minimum daily temperature is measured for a month and then its average value is recorded. So individual hot days are not flagged in the data. You can see my analysis of such data here.

Instead one needs to find the daily data – the daily records of individual maximum and minimum temperatures.

Happily this data is available from the Centre for Environmental Data Analysis (CEDA). They host the Met Office Integrated Data Archive System (MIDAS) for land surface station data (1853 – present). It is available under an Open Government Licence i.e. it’s free for amateurs like me to play with.

I registered and found the data for the nearby Met Office station at Heathrow. There was data for 69 years from 1948 to 2017, with a single (comma separated variable) spreadsheet for maximum and minimum temperatures (and other quantities) for each year.

Analysing the data

Looking at the spreadsheets I noticed that the 1948 data contained daily maxima and minima. But all the other 68 spreadsheets contained two entries for each day – recording the maximum and minimum temperatures from two 12-hour recording periods

  • the first ended at 9:00 a.m. in the morning: I decided to call that ‘night-time’ data.
  • and the second ended at 9:00 p.m. in the evening: I decided to call that ‘day-time’ data.

Because the ‘day-time’ and ‘night-time’ data were on alternate rows, I found it difficult to write a spreadsheet formula that would check only the appropriate cells.

After a day of trying to ignore this problem, I resolved to write a program in Visual Basic that could open each yearly file, read just a relevant single temperature reading from each alternate line, and save the counted the data in a separate file.

It took a solid day – more than 8 hours – to get it working. As I worked, I recalled performing similar tasks during my PhD studies in the 1980’s. I reflected that this was an arcane and tedious skill, but I was glad I could still pay enough attention to the details to get it to work.

For each yearly file I counted two quantities:

  • The number of days when the day-time maximum exceeded a given threshold.
    • I used thresholds in 1 degree intervals from 0 °C to 35 °C
  • The number of days when the night-time minimum fell below a given threshold
    • I used thresholds in 1 degree intervals from -10 °C to +25 °C

So for example, for 1949 the analysis tells me that there were::

  • 365 days when the day-time maximum exceeded 0 °C
  • 365 days when the day-time maximum exceeded 1 °C
  • 363 days when the day-time maximum exceeded 2 °C
  • 362 days when the day-time maximum exceeded 3 °C
  • 358 days when the day-time maximum exceeded 4 °C
  • 354 days when the day-time maximum exceeded 5 °C


  • 6 days when the day-time maximum exceeded 30 °C
  • 3 days when the day-time maximum exceeded 31 °C
  • 0 days when the day-time maximum exceeded 32 °C
  • 0 days when the day-time maximum exceeded 33 °C
  • 0 days when the day-time maximum exceeded 34 °C

From this data I could then work out out that in 1949 there were…

  • 0 days when the day-time maximum was between 0 °C and 1 °C
  • 2 days when the day-time maximum was between 1 °C and 2 °C
  • 4 days when the day-time maximum was between 2 °C and 3 °C
  • 4 days when the day-time maximum was between 3 °C and 4 °C


  • 3 days when the day-time maximum was between 30 °C and 31 °C
  • 3 days when the day-time maximum was between 31 °C and 32 °C
  • 0 days when the day-time maximum was between 32 °C and 33 °C
  • 0 days when the day-time maximum was between 33 °C and 34 °C

Variable Variability

As I analysed the data I found it was very variable (Doh!) and it was difficult to spot trends amongst this variability. This is a central problem in meteorology and climate studies.

I decided to reduce the variability in two ways.

  • First I grouped the years into decades and found the average numbers of days in which the maximum temperatures lay in a particular range.
  • Then I increased the temperature ranges from 1 °C to 5 °C.

These two changes meant that most groups analysed had a reasonable number of counts. Looking at the data I felt able to draw four conclusions, none of which were particularly surprising.

Results: Part#1: Frequency of very hot days

The graph below shows that at Heathrow, the frequency of very hot days – days in which the maximum temperature was 31 °C or above has indeed increased over the decades, from typically 1 to 2 days per year in the 1950’s and 1960’s to typically 3 to 4 days per year in the 2000’s and 2010’s.

I was surprised by this result. I had thought the effect would be more dramatic.

But I may have an explanation for the discrepancy between my perception and the statistics. And the answer lies in the error bars shown on the graph.

The error bars shown are ± the square root of the number of days – a typical first guess for the likely variability of any counted quantity.

So in the 1950’s and 1960’s it was quite common to have years in which the maximum temperature (at Heathrow) never exceeded 30 °C. Between 2010 and 2017 (the last year in the archive) there was not a single year in which temperatures have not reached 30 °C.

I think this is closer to my perception – it has become the new normal that temperatures in excess of 30 °C occur every year.

Results: Part#2: Frequency of days with maximum temperatures in other ranges

The graph above shows that at Heathrow, the frequency of days with maxima above 30 °C has increased.

The graphs below shows that at Heathrow, the frequency of days with maxima in the range shown.

  • The frequency of ‘hot’ days with maxima in the range 26 °C to 30 °C has increased from typically 10 to 20 days per year in the 1950s to typically 20 to 25 days per year in the 2000’s.

  • The frequency of ‘warm’ days with maxima in the range 21 °C to 25 °C has increased from typically 65 days per year in the 1950s to typically 75 days per year in the 2000’s.

  • The frequency of days with maxima in the range 16 °C to 20 °C has stayed roughly unchanged at around 90 days per year.

  • The frequency of days with maxima in the range 11 °C to 15 °C appears to have increased slightly.

  • The frequency of ‘chilly’ days with maxima in the range 6 °C to 10 °C has decreased from typically 70 days per year in the 1950’s to typically 60 days per year in the 2000’s.

  • The frequency of ‘cold’ days with maxima in the range 0 °C to 5 °C has decreased from typically 30 days per year in the 1950’s to typically 15 days per year in the 2000’s.

Taken together this analysis shows that:

  • The frequency of very hot days has increased since the 1950’s and 1960’s, and in this part of London we are unlikely to ever again have a year in which there will not be at least one day where the temperature exceeds 30 °C.
  • Similarly, cold days in which the temperature never rises above 5 °C have become significantly less common.

Results: Part#3: Frequency of days with very low minimum temperatures

While I was doing this analysis I realised that with a little extra work I could also analyse the frequency of nights with extremely low minima.

The graph below shows the frequency of night-time minima below -5 °C across the decades. Typically there were 5 such cold nights per year in the 1950’s and 1960’s but now there are more typically just one or two such nights each year.

Analogous to the absence of years without day-time maxima above 30 °C, years with at least a single occurrence of night-time minima below -5 °C are becoming less common.

For example, in the 1950’s and 1960’s, every year had at least one night with a minimum below -5 °C at the Heathrow station. In the 2000’s only 5 years out 10 had such low minima.

Results: Part#4: Frequency of days with other minimum temperatures

For the Heathrow Station, the graphs below show the frequency of days with minima in the range shown:

  • The frequency of ‘cold’ nights with minima in the range -5 °C to -1 °C has decreased from typically 45 days per year in the 1950’s to typically 25 days per year in the 2000’s.

  • The frequency of ‘cold’ nights with minima in the range 0 °C to 4 °C has decreased from typically 95 days per year in the 1950’s to typically 80 days per year in the 2000’s.

  • The frequency of nights with minima in the range 5 °C to 9 °C has remained roughly unchanged.

  • The frequency of nights with minima in the range 10 °C to 14 °C has increased from typically 90 days per year in the 1950’s to typically 115 days per year in the 2000’s.

  • The frequency of ‘warm’ nights with minima in the range 15 °C to 19 °C has increased very markedly from typically 12 days per year in the 1950’s to typically 30 days per year in the 2000’s.

  • ‘Hot’ nights with minima in the above 20 °C are still thankfully very rare.



Thanks to Met Office stars

  • John Kennedy for pointing to the MIDAS resource
  • Mark McCarthy for helpful tweets
  • Unknown data scientists for quality control of the Met Office Data


Some eagle-eyed readers may notice that I have confused the boundaries of some of my temperature range categories. I am a bit tired of this now but I will sort it out when the manuscript comes back from the referees.

COVID-19: Day 212 Update: Population Prevalence

July 31, 2020

Summary This post is an update on the likely prevalence of COVID-19 in the UK population. (Previous update).

The latest data from the Office for National Statistics (ONS) suggest even more clearly than last week that there has been a small increase in prevalence.

The current overall prevalence is estimated to be 1 in 1500  but some areas are estimated to have a much higher incidence.

Overall the ONS estimate  that 6.2 ± 1.3 % of the UK population have been ill with COVID-19 so far.

Population Prevalence

On 31st July the Office for National Statistics (ONS) updated their survey data on the prevalence of people actively ill with COVID-19 in the general population (link), incorporating data for six non-overlapping fortnightly periods covering the period from 4th May up until 26th July

Start of period of survey End of period of survey   Middle Day of Survey (day of year 2020) % testing positive for COVID-19 Lower confidence limit Upper confidence limit
04/05/2020 17/05/2020 132 0.35 0.23 0.52
18/05/2020 31/05/2020 144 0.15 0.08 0.25
1/05/2020 14/06/2020 160 0.07 0.03 0.13
15/06/2020 18/06/2020 174 0.09 0.05 0.16
29/06/2020 12/07/2020 188 0.05 0.03 0.09
13/06/2020 26/07/2020 202 0.09 0.06 0.14

Data from ONS on 26th July

Plotting these data  I see no evidence of a continued decline. ONS modelling suggests the prevalence is actually increasing.

Click for a larger version.

Because of this it no longer makes sense to fit a curve to the data and to anticipate likely dates when the population incidence might fall to key values.

Click for a larger version.

In particular, things look grim for an untroubled return to schools. Previously – during full lock down – we achieved a decline of the prevalence of COVID-19 by a factor 10 in roughly 45 days.

The start of the school term is just 35 days away and – given the much greater activity now compared with April – it is unrealistic to expect the prevalence to fall by a factor 66 to the 1 in 100,000 level in time for the start of the school term.


As I have mentioned previously, we are probably approaching the lower limit of the population prevalence that this kind of survey can detect.

Each fortnightly data point on the 31 July data set above corresponds to:

  • 51 positive cases detected from a sample of 16,236
  • 32 positive cases detected from a sample of 20,390
  • 13 positive cases detected from a sample of 25,519,
  • 18 positive cases detected from sample of 23,767
  • 19 positive cases detected from sample of 31,542
  • 24 positive cases detected from sample of 28,325

I feel obliged to state that I do not understand how ONS process the data, because historical data points seem to change from one analysis to the next. But I suspect they are just doing something sophisticated that I don’t understand.

Daily Deaths

Below I have also plotted the 7-day retrospective rolling average of the daily death toll along with the World-o-meter projection from the start of June.

Click for a larger version.

A close up graph shows the death rate is not convincingly falling at all and so unless there is some change in behaviour, death rates from coronavirus of tens of people per day are likely to continue for several months yet.

Click for a larger version.

The trend value of deaths (~65 per day) is consistently higher than the roughly 12 deaths per day that we might have expected based on trend behaviour at the start of June.

In future updates I will no longer plot the World-o-meter projection because it is clearly to no longer relevant to what is happening in the UK.

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

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