Archive for the ‘Personal’ Category

Greta’s Climate Book: An antidote to hope

November 21, 2022

Friends, as I have written before, I love and admire Greta Thunberg.

So when I heard that Greta had edited a collection of short essays on Climate Change, I ordered a copy immediately. Quietly I thought to myself: “Well that is Christmas gifts for everyone sorted.”

And when I collected my copy from the local bookshop I was delighted to find that Greta herself had signed the book! When I got home I sat down eagerly to read.

The book is attractive, covered in Climate Stripes but at 446  pages and 1.383 ± 0.002 kg, it was larger and heavier than I had anticipated.

It is also well-written. Greta’s essays that introduce the various sections are excellent: she writes with outstanding clarity. And the general standard of the short essays is excellent. I learned a lot about many different aspects of Climate Change that I had not previously focussed on.

However, I will not be gifting this book to anyone I love. Why? Because I found it overwhelmingly depressing.

Antidote to hope

Friends, Climate Change scares me. I feel the fragility of our way of life and I feel terrified for my children. And I am acutely aware of just how profoundly bad our situation is. In many ways, I am a natural ‘Doomer‘. But I resist that temptation and prefer to focus on what I can do to try to improve things – however marginally.

My resistance is not really supported by the weight of evidence which is probably on the side of the doomers. It’s a choice I have made.

And that’s my problem with the book. It amplifies every negative aspect of our situation in a way which I found overwhelmingly depressing. I appreciate the book’s straightforward honesty, but it doesn’t help me get by from day to day.

The book implies that there is no solution to the problem of climate change without simultaneously solving multiple problems of inter-national, inter-ethnic, inter-gender and inter-generational justice – problems that seem to me to be much harder than the fundamentally technical problem of stopping emitting carbon dioxide.

There is more than one thing happening

At the moment on Earth there are two epochal changes taking place. Climate Change is one of them, and its multiple levels and scales and implications of that change are well-described by Greta’s book.

But we are also undergoing an Energy Transition which I estimate will have impacts on the same scale as the Industrial Revolution.

Solar Energy, Wind Energy and Battery storage have plummeted in price and their deployment is accelerating exponentially. I’ll be writing more about this in coming weeks, but by most measures, some combination of these technologies provides the cheapest electricity humanity has ever known.

As someone who is planning to operate their home entirely from solar power for 6 months of next year, this technological shift feels very real. And this change has taken place in my lifetime.

Cost is the key. Because these technologies are cheaper than building any other kind of power, they will – even in the face of strong opposition – inevitably win. In the end, the fossil fuel technologies will simply not be able to compete. In the end we will make the energy transition, not because it is the moral thing to do, but because it is economically essential.

And this transition seems to me to offer some hope to people living in both developed and developing countries.

The Energy Transition will not bring with it solutions to the multiple problems of inter-national, inter-ethnic, inter-gender and inter-generational justice. But it does offer at least a realistic opportunity to reduce carbon dioxide emissions relatively quickly.

And for me, that would be enough.


Is it possible to live a carbon-zero life?

November 21, 2022

Friends, on Monday 21st November 2022 – which as I write this is ‘later today’ – I will be talking to hundreds of 6th Formers in London on the topic of whether it’s possible to live a carbon-zero life.

This is part of the Physics in Action series of events. As a retired person, I had thought my days of addressing such groups were over, and I feel honoured to have been asked to speak.

In case people can’t attend, I have recorded a version of the 40 minute talk which you can see below. It’s a bit flat compared to the verve of a live event, but hopefully it’s better than nothing.

And in case people – particularly teachers – wanted them I thought I would put the Powerpoint slides here. They contain many slides which are hidden but may contain useful illustrations or animations. Somehow the file is 100 Mb in size (Link). Sorry.


The thesis of the talk is that at the moment there are two epochal changes taking place on Earth.

The first is Climate Change, and my aim in this talk is to explain exactly why our emissions of carbon dioxide matter so much.

The second change is the Energy Transition. Independent of our need to respond to Climate Change, renewable technologies (solar, wind and batteries) have become the cheapest way to make electricity in human history.

This provides an economic imperative for action where moral imperatives have failed. The switch to renewable technologies will become inevitable, not  because it’s ‘the right thing do’, but because it is the cheapest thing to do.

So the second part of the talk is about some of the technologies which will enable this transition: heat pumps, solar PV and batteries.

My aim is to provide the audience with a visceral understanding of the need to change. But I hope to also provide a clear understanding that massive reductions in carbon dioxide emissions are possible right now, without the need for any new inventions or discoveries, and without the need for degradation of our quality of life.

What I did on the hottest day of the year.

November 6, 2022

Friends, do you remember 19th July 2022: The day when temperatures in the UK reached 40 °C for the first time?

I wrote about that day on the 20th July – reflections here – but I didn’t mention that I had also had a conversation that day with Gregg from the Take it EV podcast.

It was a long conversation (80 minutes) because I tend to go on on and on and Gregg is a kind interviewer, but it is now available for your delectation either as a podcast (link) or as a YouTube video below.



New Solar Panels

October 27, 2022

Friends, back at the start of September, I noted that it had been a sunny summer and I resolved to add more solar panels to the house in order to increase the solar harvest next year.

I ordered the system just a few days after writing that article and it is now being installed.

In this article I thought I would describe the new installation and how it will (hopefully) integrate with the existing installation.

Click on image for a larger version. The arrangement of the solar cells on the roof of Podesta Towers. The grey panels have been installed for two years, and the red panels were installed this week. I had hoped to fit four panels on the flat roof, but in fact I can only fit three.

The Existing Installation

The existing system was installed back in November 2020 and consists of:

Why did I select these items? The installer recommended them and they seemed to have adequate performance. And happily, they do seem to have worked OK.

Some key features of these items are:

  • 340 watts is the nominal output of a panel illuminated perfectly by sunlight with an intensity 1000 W/m^2 – this is roughly full sunlight on a UK summer day.
  • Since the panels are 1.7 m x 1.03 m one can work out that around 20% of the solar energy is converted to electrical power.
  • The panel is constructed as two half-panels wired in parallel, each with 60 individual solar cells.
  • A silicon solar cell generates around 0.6 V so the 60 cells on a half-panel together generate around 36 V.
  • Splitting the panel like this improves the panel performance when one half of the panel is shaded.
  • The MPPT acronym stands for Maximum Power Point Transfer and is system for extracting maximum power from solar panels as the intensity of illumination changes.

The quotation suggested that I might reasonably expect 3,780 kWh of generation each year and this year we look on track to exceed that. Last year we generated only 3,517 kWh.

Click on image for a larger version. Cumulative generation from the existing solar panels in 2021 and 2022. The dotted blue lines are based on the expected output according the installer’s initial calculation.

This first installation was done quickly to take advantage of the fact we had scaffolding around the house for the external wall insulation. Because of this, we couldn’t wait six weeks for permission for a larger installation from the local Distribution Network Operator (DNO): these are the people who manage the local electricity networks.

So I opted for a standard installation (for which no permission is required) with a maximum output of 3.6 kW peak and we used the best sites available. I resolved to learn what I could about solar power, and after two years, I feel I served my apprenticeship.

The New Installation

To move beyond the standard system one needs to apply to the DNO, a process that takes about 6 weeks and which was thankfully handled on my behalf by the installer.

My aim was to get as much solar PV on the roof as I could – while not making the house look horrible! For that reason, we avoided using a patchwork of panels across the roof – sacrificing some performance for aesthetics.

Since the best sites had been taken by the first installation – I simply went with what was available.

I had noticed during the summer that in the mornings the Sun rises well north of east, and the east-facing roof of Podesta Towers was in full sun up until solar midday. Similarly, the flat roof was more or less un-shadowed over the same period.

My performance calculations using the excellent Easy PV site were very similar to the suggested performance from the installer.

  • The 5 panels on the east-facing roof will hopefully generate ~1,300 kWh/year
    • The panels are tilted at ~ 40° and face roughly ~ 20° north of east.
  • The 3 panels on the flat roof – might generate ~900 kWh/year
    • The panels are tilted at ~ 12° but face roughly 20° east of south –

This would correspond to 2,200 kWh/year, an additional 60% of generation bringing the total close to 6,000 kWh/year. If actual performance gets anywhere close to this I would be delighted.

To put these figures in perspective, we can compare them with household consumption.

  • Last year the house used ~5,400 kWh –
  • Roughly 3500 kWh of that (~65%) was for day-to-day household ‘stuff’
  • Roughly 1,900 kWh of that (~35%) was used for the heat pump.
  • The heat pump operated with an average COP of 3.6 to deliver 6,800 kWh of heat.

So the enlarged system will hopefully generate more electricity than we use in a year. Sadly the peak of generation (in May or June) is quite out of phase with the peak of demand (in January or February). But nonetheless, it’s a milestone of sorts.

The new system consists of:

Again, I just accepted the installer’s recommended suggestions.

The Panels.

The new panels are similar to the old ones: the 390 W nominal peak output of the new panels is larger than the 340 W peak of the previous panels simply because the new panels are larger. The efficiency remains around 20%.

Each panel consists of two half-panels, each with 9 rows of 6 rectangular half-cells.

Click on image for a larger version.

When illuminated, each individual cell generates a voltage between 0.5 V and 0.7 V between the top of the cell (the part you can see) and the bottom of the cell (that is at the back of the panel).

Fine aluminium wires cover the top of the cell to collect the generated electrons, and the wires then connect the top of one cell to the underside of the neighbouring cell so that their generated voltages add together. In each half-panel, 54 cells in series generate a voltage ~ 36 V at a current of roughly 5 amps.

Click on image for a larger version. Top: Illustration of the way in which sunlight generates a voltage between the bottom and the top (illuminated) surface of the cell. Right: The fine wires collect electrons generated from within the silicon. The filigree wiring pattern is optimised to collect as many photo-electrons as possible, while not blocking the sunlight. Left: Details of the wiring showing the top surface of the lower scale is connected to the underside of the neighbouring cell.

The two half panels are wired together in parallel so that the peak output of the whole panel is ~ 36 V at a current of roughly 10 amps.

Panels which are similarly illuminated are wired in series in a so-called ‘string’. In this installation, the 5 panels on the east-facing roof are wired in one string and the 3 panels on the flat roof are wired in another.

The inverter design has two independent inputs and the DC currents from the two ‘strings’ are combined to create an AC current at 220 V.

This arrangement works excellently when all cells in a panel and all panels in a string are illuminated similarly. But if one cell in a panel is shaded, then not only does that cell not generate a current, its electrical resistance increases dramatically, and this can restrict the current which is able to flow through the whole string of which it is a part. Fortunately, clever electrical tricks can minimise the shading problem as explained in this excellent video.

Peak Power.

One aspect of the installation which concerns me is whether all the electrical circuits can cope with the sheer amount of power this system might generate.

To estimate this, I downloaded generation data from 22 June this year, a day which was nearly perfect for solar generation: close to the solstice and almost completely cloudless. This data is shown in red on the graph below.

I then made guesstimates of the generation from the two new strings:

  • I guessed the 5-panels on the east-facing roof would begin generating earlier in the day and reach maximum power (5 x 390 W = 1,950 W) just before solar noon (1:00 p.m. BST). This is shown as a green dotted line.
  • I guessed the 3-panels on the flat roof would generate roughly symmetrically around solar noon (1:00 p.m. BST) with a maximum power of 3 x 390 W = 1,170 W. This is shown as a blue dotted line.

Click on image for a larger version. Graph comparing a perfect midsummer generating day with the existing system (red curve) with the likely generation from the expanded system (purple curve). See text for details.

Altogether (dotted purple line) the total power could potentially exceed 5 kW – a worryingly high power level.


Friends, as usual, I have gone on for too long. But this is a significant – and possibly final – step in the house refurbishment.

It offers the possibility of being off-grid for 6 months a year and of generating more electricity than the household consumes (averaged over a year). I think these are significant upgrades.

The cost is not completely clear yet, but looks like it will be just under £5,000. This is more than the initial system (£4,200 in November 2020) but this seems reasonable given the extra scaffolding required.

As I write, the panels are installed but the internal electrical wiring is not complete – but hopefully that will be done soon!

And if you have read this far, thank you! Please allow me to reward you with a video of the installation.



Grounds for Cautious Hope on Climate

October 19, 2022

Friends, ‘doomerism is – understandably – everywhere. But it is such a corrosive perspective.

So I was pleased to encounter a one hour talk by Zeke Hausfather on the The Case for Cautious Climate Hope.

This is Zeke’s précis to which I have added some punctuation.

The world is currently on the brink of both potential climate catastrophe and rapid decarbonization.

On one hand the climate crisis has become too severe to ignore; what was once a problem that people thought their children would face is now something that is impossible to ignore, with record-breaking heat, droughts, wildfires, flooding, and other climate impacts happening on a daily basis. While climate change is not necessarily happening faster than we thought, many of the impacts of climate change are proving more severe than we initially expected. Atmospheric CO2 has now risen to levels last seen more than four million years ago, and current global temperatures are likely higher than any multi-century period in at least the last 125,000 years.

At the same time, the energy transition is happening far faster than anyone predicted a decade ago. Solar and battery prices have fallen by a factor of ten in a decade, global coal use peaked back in 2013, around 14% of new vehicles sold globally are electric, and the darkest climate futures where emissions doubled or tripled by the end of the century are now receding from view.

Close to 90% of global emissions are covered by pledges to get to net-zero around the middle of the 21st century, and countries are starting to pass meaningful climate policy to put us on a path toward achieving those goals.

But it is increasingly clear that the world will overshoot our most ambitious climate change target of limiting warming to 1.5°C in the next decade or two, even though our ability to limit warming to below 2°C is growing much stronger.

It is a time for a cautious climate hope that both acknowledges the progress we have made and how far we still have to go. 

If you have an hour to spare, the talk is worth listening to. In particular because it realistically acknowledges the depth of the hole we are in – which is deep –  while pointing out that we have made real and measurable progress.

If you only have 30 minutes, then just listen to the start. Despite a few IT problems it does manage to convey that although things are still bad, they are not as bad as we thought they were going to be.

Heating My Home

October 18, 2022

Friends, I have made a 5-minute video about heating my home with a heat pump.

It’s nonsense, but once I had thought of the idea of using coloured water to represent heat, I felt compelled to make the video: I hope you enjoy it.

Talk about Heat Pumps

October 5, 2022

Friends, this evening I will be giving a talk about Heat Pumps to the Richmond and Twickenham Branch of Friends of the Earth.

Specifically the talk is about switching from using a gas boiler to a heat pump

But I have already given the talk!

I recorded a version of the talk this morning and you can see it below!

If you want you can download the Powerpoint Slides using this link  (15 Mb)

Sadly, the talk is an hour long, but given the list of 25 things I had to talk about, I guess that was inevitable.

Viewers who liked that talk may also be interested in…

How heat pumps work

A Rule of Thumb for sizing heat pumps

Our EV is an EB

September 30, 2022

Friends, in an unexpected turn of events my wife has gone mad and bought a boat.

The Boat

It’s a 51-year old boat which has been converted to run on batteries.

The boat is a Freeman 23 model and in the same way that some makes of old cars are considered ‘classics’ – think perhaps of a Morris Minor –  this too is a ‘classic’ of a kind.

However its petrol engine – which was from an old Ford Anglia – has been replaced with a 10 kW electric motor powered by eight ‘leisure-grade’ lead acid batteries.

The total battery capacity is 8 x 12 V x 110 Ah which amounts to 10.5 kWh. However the battery technology is so archaic that one is never supposed to discharge the batteries below 50%. Hence the effective capacity is about 5 kWh. And together they weigh a humongous 200 kg!

Nonetheless, this is sufficient to cruise for maybe 5 or 6 hours a day depending on the boat’s speed and whether one is going upstream or downstream.

And the cruising is pleasantly quiet.

Once we have worked out how the boat works and come to terms with our new ‘boatowner lifestyle’, I suspect my wife will invest in some Lithium Iron Phosphate Batteries. These have the same form factor as lead-acid batteries, but weigh around half as much, have twice the useable capacity and can be charged and discharged many thousands of times.

Electricity changes everything

Talking with the people in the sales office, I was surprised to learn that about half the boats they sold now were electric. It seems that just like with electric cars, once people have experienced electric boats, they don’t want to go back.

The absence of the noise and pollution from petrol and diesel engines is a positive pleasure.

For me personally, the fact that the boat is electric transforms my feeling about it. And I feel very lucky to have a wife who shares this sensibility.







Long Rainy Summers: A Lament for a Lost Climate

September 25, 2022

Friends, something different: here is a song about Climate Change.

In the song I am trying to evoke the deep sadness I feel that my children and – entirely putative – grandchildren, will never experience something as basic as the climate in which I grew up.

The lyrics of the song are listed below and the video is just the song with a few images set against a background of the ‘Climate Stripes‘ representation of rising global temperature.

For those who care, you can listen to an acoustic version below.

All the best




Oh I long for the long rainy summers
I used to know in my youth
I long for the long rainy summers
I wish you could know them too.

Now summers bring us endless heat
And we dream of cooling rain
We lie in bed but we cannot sleep
We feel the heat inside our brain

And when the rain comes, it comes in storms
Like none we’ve ever seen
What has become of England,
Once so pleasant and so green?


We burned the coal, the gas and oil
Without a second care
And we drove our cars and we flew in planes
And put tonnes of (CO2) See-Oh-two in the air

Even after we were were warned,
We ignored the facts like fools
And the Earth has warmed like they said it would
And it will never ever cool


The Daily Mail told us we must serve
The needs of our economy
And that Climate Change would be alright
If we could just grow our GDP

But the Daily Mail told us Daily Lies
The heat gets worse each year
It turns out no amount of money can
Repair our atmosphere


It is our children who will reap
The whirlwind we have sown
They will have to pay the price
For this long party we have thrown

But it’s not too late, we can still act
and stop things getting worse.
If we choose now to do all we can
We may yet escape our children’s curse(s)



Finally off gas! Well, Almost Finally.

September 23, 2022

Friends, yesterday was a happy day. Two technicians finally removed our gas hob and installed a new induction hob.

The gas oven and grill was replaced last week, and so this was the last step in a journey which has taken nearly four years.

And finally, we have no need to burn gas in this house ever again. I feel emotionally exhausted.

The Journey

The household’s smoothed daily gas consumption (kWh/day) along the journey is shown in the graph below.

Click on image for a larger version. Based on weekly readings of the gas meter, the graph shows Gas consumption in kWh per day for the last four years years, with the time-axis showing the number of days elapsed since the start of 2019. The data are averaged over 5 weeks to smooth out the noise. The pink boxes show the dates of key interventions which affected gas consumption.

Back in 2018/19 peak mid-winter gas consumption was over 110 kWh/day. This fell to first 70 kWh/day in 2019/20 and then 50 kWh/day in 2020/21.

In August 2021, the gas boiler was replaced with an Air Source Heat Pump, and since then we have just used gas for cooking – using an average of just over 1 kWh gas/day.

The graph also shows the heat output of the heat pump over the winter of 2021/2022.

The graph below shows details from the graph above.

Click on image for a larger version. Details of the graph above showing periods where gas usage was low.

Looking at summer consumption, back in summer 2019 (with my son and his girlfriend staying with us) we were using gas for hot water and cooking and our usage was around 6 kWh/day. In summer 2020 (with just my wife and I in the house) this fell to ~4 kWh/day.

Since 2021, we have used gas solely for cooking, an average of just over 1 kWh gas/day. Combined with the heat pump output of roughly 3 kWh/day for domestic hot water, this roughly matches the 4 kWh/day of gas consumption we used back in 2020.

Today’s step corresponds to Day 1360 and I have presumed to fill in ‘zeros’ ahead of time out to the end of the year.

In terms of carbon dioxide emissions the graph below shows that 3 tonnes of carbon dioxide that the house used to emit, is now finally falling to exactly zero.

Click on image for a larger version. Cumulative emissions of carbon dioxide from burning gas in the house. 

What’s wrong with ‘cooking with gas’?

Fundamentally, cooking with gas is a barely-evolved version of cooking on an open fire: it releases carbon dioxide and toxic pollutants (NOx) directly into our kitchens – a critical issue for anyone with asthma or children.

Although each installation differs, careful measurements reveal that domestic gas installations typically leak around 1% of the methane gas they consume – which practically doubles the global warming effect of using gas.

Gas cooking also wastes a large fraction of it’s embodied energy heating the room  – with typically just 40% of the gas’s energy being delivered to the food in a saucepan.

Click on image for a larger version. Left: measuring the rate of heating of 1 kg of water in a saucepan on a gas hobRight: the equivalent measurement on an an induction hob. The lid was kept on through the experiment except for occasional stirring, and the temperature was inferred from the average temperature of two thermocouples.

The graph below shows the rate at which 1 kg of water is heated on a gas hob and on our new induction hob. The effective heating power is a factor 3.6 larger.

Click on image for a larger version. Measured rate of heating of 1 kg of water in a saucepan on a gas hob and an induction hob. The induction hob heats the water between 3 and 4 times faster than the gas hob.

What’s so good about induction hobs?

Fundamentally, the key advantage of cooking with electricity is that the electricity can come from any source, including solar PV or wind. This afternoon, as I carried out the heating experiment on the hob, the electricity was being supplied entirely by the Sun.

Installing this hob means that we have finally broken this archaic link where ‘cooking’ implies that something must be burned and carbon dioxide emitted.

Induction hobs – aside from being quick and powerful – also combine features which gas cookers never could – such as temperature-related feedback control.

And it’s not just hobs: we have also replaced our cooker, and it was such a blessed relief to get rid of that appalling gas oven. The gas oven spewed it’s exhaust gases (steam and CO2) into the oven chamber itself meaning that they had to be continually cleared out  – wasting lots of energy heating the kitchen.

Now having a high temperature in the oven no longer means that the kitchen temperature needs to rise also!

Michael: what did you mean by ‘Almost’ off gas?

Friends, nothing in life is easy.

In order to change the cooker and hob I needed to have the backing of my wife who, while not hostile to my endeavours, does not share my enthusiasm.

And as a quid pro quo for the purchase of the cooker and hob from our joint savings, my wife suggested that we retain a gas fire in the front room.

I had planned to get rid of the gas fire – which we have not used for a year or more – and have the gas supply cut off, saving the standing charge of around £98/year. But my wife suggested that we may have power cuts this winter – and she has a point –  and that having more than one kind of heating might be useful.

So for another winter season we will retain the possibility of burning gas.

In case you care, this is what we bought.

Click on image for a larger version. Features which helped us choose our particular models of cooker and hob. For the hob we liked this simple way of setting power levels rather than having to repeatedly press a button.  For the cooker, we liked the way the controls recessed into the panel for cleaning.

My wife and were both unfamiliar with cooking with electricity and so bought mainstream models from Bosch on the principle that Bosch probably know what they are doing better than we do.

For the hob, my wife was concerned that the controls might be fiddly to use if we had to repeatedly press a “+” or “-” button to set a cooking level.

To avoid that situation we picked a model (Serie 6 PXE651FC1E) in which the cooking power is set by first selecting the relevant control area, and then touching a point on a scale: based on our experiments this afternoon, this works as sweetly as we had anticipated.

For the cooker, we chose a model (Serie 4 MBS533BS0B) in which the knobs could be recessed because that seemed very pleasing.

On balance, we thought both these items were very expensive for what they were and there are probably much better bargains to had.

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