Dust and Water

Dust by Jay Owens and The Three Ages of Water by Peter Gleick.

Friends, I have recently read two books that have caused me to re-evaluate – in the words of Peter Gleick – the true value of water. The first book, Dust, considers the role of dust in human culture. And the second, The Three Ages of Water, describes the critical importance of fresh water for all life on Earth. Partly to help me recall the contents, I thought I would write a précis of the two books, and I hopefully you will find this of interest too.

Dust

Dust may seem an odd topic for a book, but it in fact dust is an intrinsic part of the natural world and plays an outsize role in many geophysical processes. As materials break down, they turn into small and smaller particles and at some point – below around about a tenth of a millimetre or so – we somehow lose consciousness of them as individual particles. But the materials are still there. Crucially, when not bound by water, particles of this size are small enough to be lifted by the wind and held aloft.

Jay Owens begins her assessment of the significance of dust in her own flat as she reflects on the astonishing amount of otherwise invisible dust made visible in the beams of sunlight. This is the start of a world-wide journey.

She first revisits the origin of the concept of ‘dusting’ – a task which arose from combination of the appalling particulate pollution from coal burning, and the development of consumer goods which needed to be displayed. She argues that the idea of household cleaning as “women’s work” led to the oppression of women throughout the 19th and 20th Centuries.

She visits Owen’s Valley, California where in the 1920’s entrepreneurs from Los Angeles acquired – through techniques of dubious legality – water rights that underpinned the growth of Los Angeles and led to the destruction of Owen’s lake, which became a source of toxic dust, and led to the desolation of a fertile valley. And she visits the land at the heart of the creation of the dustbowl in the US in the 1930’s.

Likewise she visits the Aral Sea where in the 1960’s soviet planners re-directed the sources that fed the Aral Sea in order to grow cotton. Since then the sea has all but disappeared, leading to toxic dust storms that have led to the desertification of a once fertile ecosystem.

Click on image for a larger version. USGS Landsat images of the Aral Sea in 1992 and 2020. Even in 1990 the sea, once the 4th largest freshwater lake on Earth, had already undergone significant contraction.

She visits the areas around atomic bomb test sites and investigates the lasting impact of the clouds of invisible radioactive dust that spread across the USA from the explosions.

Click on Image for a larger version. From the Downwinders Website, this graph shows the dose of radioactive Iodine -131 at locations across the US as a result of dust particles from atomic bomb tests.

And she visits Greenland to see the effect of particles of black carbon on the melting of the ice sheet.

Click on Image for a larger version. The upper image from the American Museum of Natural History shows a section of an ice core from the Greenland Ice sheet. The yearly bands are clearly visible. The lower graph shows analysis of such ice cores revealing the amount of black carbon dust deposited year by year over the last 800 years.

Throughout all her travels, Jay Owens emphasises the outsize role that tiny particles of dust play, and notes that somehow it always the less powerful groups in society that suffer. Although her writing is polemical at times, I feel that the book has nonetheless raised my consciousness of dust. Previously I had thought of dust as being incidental or peripheral, but in fact, if you look for it, dust is everywhere.

Water 

We all know that water is important, but Peter Gleick’s aim in writing this book is to urge is to see the true value of water.

In the first age of water, he discusses the role of water in the prehistory of the solar system, our planet, and the development of life, and leads us eventually to the critical role of water in the first civilisations that we know of, circa 5,000 BC.

What I had not fully appreciated is the profound extent to which control of water – via the construction of dams and irrigation structures – was at the base of all of the activities of these civilisations. And that loss of control – either via floods or drought or conflict – led to the collapse of societies, over and over again.

The second age of water – the age in which we are now living – is the age in which we ‘mastered’ fresh water. We can now control the flow of water from mountains to the sea, and we can ‘mine’ water from deep underground. And we know how to create potable water almost anywhere on Earth. And yet after perhaps 150 years of mastery, we find ourselves in a very difficult place.

Most critically, despite the UN declaring water to be a fundamental human right – with a nominal target of 50 litres per day – millions of people on Earth still lack basic facilities for drinking and hygiene.

Click on Image for a larger version. Based on weekly meter readings, the graph shows the household usage of water for myself and my wife is on average around 100 litres per person per day.

Additionally, and I don’t need to tell this to UK readers, many of our rivers and water courses are polluted to the point where ecosystems have been damaged.

Perhaps the defining feature of the second age of water is that we have treated water as being “ours” and considered any water which is not captured or used to be wasted or ‘lost’.

And worldwide we have mined “fossil” water collected in aquifers over thousands of years to create agricultural systems that have flourished for a few decades, but which are – literally – unsustainable. If we run out of almost any other substance, we can find a substitute, but there is no substitute for water.

The third age of water is the age which Gleick believes we are entering, and age in which we truly value water as the unique element around which all ecosystems are constructed. Some features of this age are:

• Reduction of the amount of water that we use, domestically, industrially and agriculturally – but with no reduction in the utility we extract from the water.
• Valuing potable water for the wonderful product that it is and using ‘grey’ water for many of the functions for which we currently use potable water.
• Valuing the ecosystems within which all life exists, even to the point of giving rivers and ecosystems legal representation. Already, the US is removing dams to allow the slow re-building of natural water courses, and wetland restoration projects are underway world -wide.

I found the book by turns educational and inspiring. Although hearing of the phenomenal degradation left over from the second age of water, I feel that we have now universally accepted that it’s generally a bad thing when rivers catch fire. [Note added: Randy Newman wrote a song about one of the better known river fires]

As I was reading the book reports were unfolding of the appalling behaviour of Thames Water, the company that supplies my own water. And I was reminded that water is still of fundamental importance and that as in the civilisations of Early Mesopotamia, kingdoms could fail if water was not well-managed.

Water & Dust 

As regular readers will know, I am personally immersed in issues around our Climate Crisis. And I try to avoid becoming too involved in our other ongoing ecological crises – things can get very depressing! But together these books have raised my consciousness without getting me down too much. The Three Ages of Water in particular sets out a very positive and achievable agenda for change.

Saving the World One Day at a Time

Friends, please accept my apologies, this post is another song. It’s on YouTube at this link. I think this thing with songs is probably just a ‘phase’ and I’ll get back to calculating something soon.

The YouTube version is just me singing and accompanying myself with a guitar, but if you prefer an amateur ‘rock’ arrangement, there is a version on Soundcloud at this link.

Why?

Friends, I write songs and sing about the things which affect my life. And I am immersed in the Climate Crisis. And I don’t think I am alone. Even people who are not active in any way understand that “something is not right”. And singing is a way to communicate with the clientele of The Mason’s Arms, very few of whom follow my blog.

Lyrics

Friends, I’m just an old man, trying to live my life in peace.
I’m no kind of… revolutionary.
But there’s something going on. Something really wrong.
And it affects my kids and that means I can’t sleep…

So… I’m trying to save the world, one day at a time,
Making up for what my generation’s done.
I’m trying to save the world, one day at a time,
Because my children have to live here when I’m gone.

The Good Earth gives us everything we need.
But the Earth’s in pain, she’s begun to scream and bleed…
The Good Earth doesn’t need us. Doesn’t need to feed us.
So when the Earth’s in pain – we’d best take heed.

So… I’m trying to save the world, one day at a time,
Making up for what my generation’s done.
I’m trying to save the world, one day at a time,
Because my children have to live here when I’m gone.

We’ve been burning oil and coal, for about two centuries.
And now the whole world’s getting hotter every year.
Some say we can’t afford to stop. But I say we can’t afford to not!
Because no amount of money, can repair Earth’s atmosphere.

So… I’m trying to save the world, one day at a time,
Making up for what my generation’s done.
I’m trying to save the world, one day at a time,
Because my children have to live here when I’m gone.

I am just one person, you’re one person too.
And these problems seem impossibly too grand.
But we all care for our kids. And if each of just did,
What we need to, then our kids might have a chance.

So… Let’s try to save the world together, one day at a time,
Let’s make up for what our generation’s done.
Let’s try to save the world together, one day at a time,
Because our children have to live here when we’re gone.

So… Let’s try to save the world together, one day at a time,
Let’s make up for what our generation’s done.
Let’s try to save the world together, one day at a time,
And hope our children will forgive us when we’re gone.

©Michael de Podesta 2024

Big Storm

Friends, today I offer you a song about Climate Change: Big Storm. (You Tube Link). If songs aren’t your thing, don’t worry, normal service will be resumed presently.

I spend a lot of my time writing and singing and recording songs. It’s a time-consuming business, but it is nothing compared to the hassle of making a video. This video passed the low bar I set for “good enough”, but I am aware that the lip-synching is poor, and that I occasionally become slightly transparent! There is also much more of my own face than I feel comfortable with. I can imagine a much better video – but I don’t have the technical ability to make it!

Nonetheless, I like the song. I hope you enjoy it too.

Big Storm Lyrics

There’s a big storm coming, I can feel it in the air.
If you care to look around, you’ll see the signs are everywhere.
There’s a big storm coming, it’s getting closer every day.
Stay with your family, you could all… be blown away.

Climate change is with us, Climate Chaos everywhere.
Climate Change Deniers on TV swear round is square.
Climate change is with us, feels like there’s no relief.
We’ve made a deal with the devil, and he’s turning up the heat.

There’s a big flood coming, the water’s rising every day.
Slow and relentless, that’s water’s way.
There’s a big flood coming, but you’re not ready yet.
No-one thinks the flood will really come… until their feet get wet.

The climate we grew up in, is gone, never to return.
The meadows we once wandered in, will turn to dust and burn.
The Good Earth once provided us with everything we need.
But now we’ve sacrificed its future, on the altar of our greed.

There’s long hot summer brewing, the grass has turned to straw.
Farmers are complaining, nothing’s growing anymore.
There’s long hot summer brewing, and we all know why.
No-one thinks the drought will really come… until their taps run dry.

Climate change is with us, Climate Chaos everywhere.
Climate Change Deniers on TV swear a circle is a square.
Climate change is with us, and there’s no relief.
We’ve made a deal with the devil, and he’s turning up the heat.

 

Local Councils and Climate Change

Friends, I love the phrase “Think Global, Act Local“. In the UK, it perfectly describes the important role of local councils in facing up to climate change.

I had cause to reflect on this role earlier this week when I spoke at an event organised by Kingston Council: a “bite-size” retrofit event  at which members of the public could meet with ‘retrofit’ installers and advisers. It seemed to be a happy affair and for anyone who was (or wasn’t) there, you can download the Powerpoint slides from talk here. There will be a larger Kingston’s Efficient Homes Show on 18th May 2024 but the booking arrangements don’t seem to have been published yet.

It was good to see suppliers and ‘punters’ coming together, but nothing about the event – except possibly my talk – implied that there was any urgency at all about getting things done. This is despite the fact that Kingston Council declared a climate emergency in 2019 and set a target of 2038 for the borough as a whole to reach net-zero emissions of carbon dioxide. Richmond Council gave themselves 5 more years. But as I wrote previously, this requires installing heat pumps and solar panels at scale right now. But – in my opinion – the attitude of the councils towards the people they serve is completely inappropriate. It’s as if they just don’t know how to be helpful.

So rather than just moan, I thought I would follow on from my previous words on this subject by describing what councils could do. Everything in green below this paragraph is what I think should be on the council’s web sites.

Please don’t concentrate on the details: these are just ideas off the top of my head of things which councils could do: a daydream. But do please notice the general tone. It’s a tone which shows awareness of the urgency of our situation, and the need for a radically different approach.

We need our Councils to imagine what a sustainable future might look like rather than trying to preserve the past. In the case of Richmond upon Thames and Kingston upon Thames, these boroughs will be regularly and inevitably flooded in the coming centuries unless we collectively take drastic action now. And then the ‘character’ they are trying to preserve with their restrictions on heat pumps and solar panels will be utterly worthless.

====================

Principles

Following on from the borough’s declaration of a climate emergency in 2019, a review of progress in 2024 revealed that our current policies are not on track to meet our goal – or even get close to it. In fact, the review identified the council as a major hindrance to progress on climate goals. Despite our public proclamations, we were guilty of what the Review Team called Institutional Passivism through which we failed to respond to the magnitude of the problem we face. We are now resolved to become “part of the solution” rather than continuing to be “part of the problem.” 

The review team reminded us that until the world as a whole reaches net zero emissions of carbon dioxide, Earth’s temperature will keep rising. And even after we reach net-zero, Earth will not cool for thousands of years. So we have already lost our stable climate, but by achieving net zero as rapidly as possible, we can still minimise the damage caused, and the chances of catastrophic changes. This is a global challenge but it requires a local response. Changing climate will affect every one of us, even in our comfortable borough. And so this Borough – like all towns and cities across the UK and the world – needs to play its part.

The task that we face is immense. Familiar habits will need to change and that will be uncomfortable for all of us. The following policies have been arrived in conjunction with the Scientific Review team, and represent a cross-party response to this threat. 

1. Methane (Natural Gas)

The burning of methane gas for heating and cooking is not compatible with net zero emissions and so the council have banned the installation of any new gas boilers in council-maintained buildings, including schools.

Cooking with gas will be stopped in council-maintained properties. Borough engineers will be retrained to install electric only replacements for boilers and cookers.

Because we anticipate that the gas network will not be needed beyond 2043, the council have withdrawn permission for all but emergency renewal of gas mains in the borough. This will result in reduced congestion and the road maintenance required after gas works.

2. Heat Pumps.

The carbon dioxide emissions from heating homes are currently the largest single source of carbon dioxide emissions in the borough. The task of changing heating from gas to clean electrical heating is enormous and we have been slow to start: it is imperative that we now begin to make rapid headway on this task.

It is clear that in order to meet our net-zero target, by 2040 the majority of homes in the borough will need to be heated with heat humps. As a council we cannot compel people to install heat pumps, but we can do everything we can to make it as easy as possible for people to install them. 

As part of this, the council has removed all restrictions on the installation of heat pumps with a rated heating power less than 12 kW. Any heat pumps with an accredited sound power output (EN 12102, EN 14511 LWA, A7/W55 of dB(A) 63 dB or below requires no further proof of suitability. This applies for both air-to-water and air-to-air heat pumps. We understand that residents may be unsure about installing heat pumps, so we have established a regular Saturday ‘heat pump clinic’ at which residents can ask questions of installers and council experts.

Additionally, in order to minimise duplication of effort in solving common problems, the Council have identified the 10 most common dwelling types in the borough and worked with local architects and installers to identify solutions to problems that people often encounter when installing heat pumps in these dwellings. These are:

• Terraced houses (Small)
• Terraced houses (Large)
• End-of-terrace house
• 1930’s style semi-detached homes
• 1930’s style Detached homes
• Edwardian town houses
• Basement Flats
• Ground Floor Flats
• First floor flats
• Second floor flats – and above

We have begun testing these ‘template’ solutions and if you would like to be part of our test program, please contact the Council. 

3. Solar Panels & Batteries.

The use of solar photovoltaic panels (Solar PV) is one of the technologies which will gives us a chance to create a sustainable way of living in the coming century. We are aware that some may consider solar panels unsightly, in this emergency we feel it essential to minimise carbon dioxide emissions as rapidly as possible. Adding solar panels does not harm a building and if in 50 years time the climate crisis has been solved, the panels can be removed and the original look and feel of the building restored.

Consequently, all  restrictions and guidance on the visual appearance of dwellings fitted with panels have been withdrawn. Residents are at liberty to fit as many solar panels as they choose – subject to District Network Operator (DNO) approval. The council have begun work with the local DNOs to establish the optimum location of neighbourhood batteries. These batteries will reduce the borough’s net draw on the UK grid network, and enable a higher fraction of solar generation to be used locally.

Starting immediately, all new housing in the borough will be required to generate at least 10 kWh/year of PV electricity for each square metre of floor space in a dwelling. Designs which cannot meet this criterion will not be considered.

Similarly, any development of a dwelling in the Borough that requires planning permission for any reason, must include a solar PV installation.

Any retail developments that include car parking for more than 50 cars, must incorporate a solar canopy for solar generation.

4. Insulation, draught-proofing, and secondary glazing.

Insulation and draught-proofing are among the simplest and most cost-effective was to reduce heating demand, and thus carbon dioxide emissions. Many draught-proofing solutions can be fitted by home-owners themselves. The Council have produced videos showing how to fit draught-proofing to the most common types of doors and windows in the borough.

No matter the architectural or historic merit of a dwelling, it’s residents are entitled to live comfortably. So the council is lifting all restrictions on the use of External Wall Insulation and secondary glazing in all buildings in the borough. These developments will be at the discretion of the owners. Examples of good practice have been developed for the application of EWI in typical homes in the borough. 

5. Public Transport and Electric Vehicles

Vehicles powered by combustion engines of any type are not compatible with Net-Zero. The Council’s own fleet of vehicles will electrified within the next three years. Following on from this, all Council suppliers and contractors will be required to use electric vehicles when working on Council contracts.

The borough will continue to develop safe cycling and walking infrastructure, and together with our already excellent public transport, we anticipate this will form an increasing part of resident’s travel within the Borough. But some use of personal cars will still be required. In line with Government targets, we anticipate that an increasing fraction of resident’s vehicles will be electric vehicles (EVs).

To meet the charging needs of residents who do not have access to an EV charging point, we will expand further our lamp-post chargers, and residents will be able to use a council-approved cross-pavement cable slot to charge cars near to their homes. Additionally from 2025, all businesses with a car park for more than 20 vehicles will be required to provide EV charging facilities for customers.

6. Schools

The burning of methane gas for heating and cooking will be banned in schools. Schools will transition to the use of heat pumps for heating, and school roofs and canopies will be used for solar PV installations. 

7. Drains

The more intense rainfall events predicted are already with us, and poor drain maintenance in the Borough has led to widespread temporary flooding. In order to minimise this, an improved regimen of drain clearing and street cleaning will be implemented to maximise the capacity of existing drains to avoid local flooding. 

Summary

The Borough Council exists to serve its residents. As the Review Team identified, the Climate Crisis will deepen in coming years in ways we cannot yet fully anticipate. The Council’s resources are limited and most of the steps required to transform the Borough into a zero-carbon Borough will need to be taken by residents themselves using their own money. But the Council is fully resolved to use all its powers to enable the Climate Actions that our residents are eager to undertake. 

Powerwall Battery Degradation: Winter#3

Friends, as you are no doubt all aware: everything is getting worse. But the other day I noticed that one thing in particular was not getting worse quite as quickly as I had expected: the nominal capacity of my Tesla Powerwall 2 battery.

The Tesla Powerwall 2: Capacity

The Tesla Powerwall 2 is a home battery with a nominal capacity of 13.5 kWh when new. However the capacity of all rechargeable batteries declines over time, and it can be quite difficult to assess the actual capacity of the battery in use. I wrote about this at the end of the winter of 2022/23 where I estimated that since the previous winter the battery capacity had fallen by about 3.5%. It’s only the start of the winter of 2023/24 but so far it looks like capacity has fallen by less than a further 1%.

Click on image for a larger version. Measurements over the last three winters showing the amount of electricity discharged from the battery as it goes from 100% full to empty within a single day. See the text for more details.

What do we mean by Battery Capacity?

Assessing the capacity of a battery while it is in use in a home is tricky. And one reason for that is that it is hard to define even what one means by ‘capacity’. Really? Allow me to explain.

The nominal capacity of the Tesla Powerwall 2 is 13.5 kWh, but the battery can only be charged from AC power with an efficiency of about 95%. And it can only be discharged with an efficiency of about 95%.

• So to ‘fill’ the battery requires 14.2 kWh of AC electricity, 95% of which will be stored in the 13.5 kWh of battery cells, with the additional energy ending up as heat.
• Similarly, when the battery is discharged at 95% efficiency, only 12.8 kWh of useful AC electricity will be produced.

In practice, I can only assess the capacity of the battery in winter on days when the battery is re-charged to 100% capacity overnight and then we run from the battery until it is drained again. In this way I can obtain a figure for the total energy discharged from the battery.

Click on image for a larger version. Four screenshots from the Tesla ‘App’ showing the complete discharge of the battery during the day. The lower section of each screen shows the battery state of charge. The upper section of each screen shows charging from the grid, discharging to meet the household load, and a few brief episodes of solar recharging.

One small complication arises from small amounts of solar generation during these winter days. If solar generation exceeds the household demand then the battery will start to re-charge (at 95% efficiency) and this extra charge will then discharge at 95% efficiency.  I only consider days in which this solar re-charging is small, and simply subtract it from the nominal capacity, but the simplest measurements to interpret are on those on dull days when there is no solar charging.

Click on image for a larger version. Measurements over the last three winters showing the amount of electricity discharged from the battery as it goes from 100% full to empty within a single day. See the text for more details. Each blue dot represents a single full-to-empty measurement. The large black circles show yearly averages and trends are shows as dotted lines.

The graph above (the same as the one at the head of the article) shows all the results since 2021. Each blue dot represents a day of full discharge. And each blue dot with a pink outer circle is day of full discharge in which there was no solar re-charging.

• Based on the specification we might hope for a discharge of around 95% of the 13.5 kWh nominal capacity i.e. 12.8 kWh.
• During the winter of 2021/22, the average daily discharge was 13.1 kWh – rather better than we might have hoped for.
• During the winter of 2022/23, the average daily discharge was 12.7 kWh – a decline of 3.4% in one year.

This article is simply to mention the good news that:

• So far, during the winter of 2023/24, the average daily discharge has been  12.6 ± 0.2 kWh – a decline of less than 1% since last year. Which is pleasing.

What should I expect?

If we extrapolate two trend-lines, one based on the decline in Years 1 & 2, and the other based on the decline in Years 2 & 3 (so far), then one trend line indicates a 20% decline in capacity over 6 years, and the other suggests a 20% loss in capacity after 20 years. My guess is that the answer will be somewhere in between the two.

Click on image for a larger version. Measurements over the last three winters showing the amount of electricity discharged from the battery as it goes from 100% full to empty within a single day. See the text for more details. Each blue dot represents a single full-to-empty measurement. The large black circles show yearly averages and trends are shows as dotted lines.

When I bought the battery I guessed that the battery degradation might be similar to that seen in early Tesla cars (Model S and X). This data (now 5 years old) is plotted versus kilometres travelled below.

Click on image for a larger version. 2018 data from Electrek showing battery capacity (%) for Tesla Model S and X cars versus kilometres travel. The trend indicates about 10% loss of capacity after 250,000 kilometres. Both graphs show the same data but the right-hand side ‘zooms in’ on the data.

The data shows two interesting things.

• Firstly  it shows a relatively rapid decline in retained capacity in the first 20,000 km of life – perhaps the first year of typical use, followed by a lower rate of decline out to 250,000 km.
• Secondly, there is a lot of variability in the data. This data is from 2018 and so would feature battery packs installed in perhaps 2012. Some batteries don’t seem to perform well at all. The cells in my Powerwall are still of this design type (so-called 2170 cells), but I suspect manufacturing quality has improved substantially since 2012.

However the battery packs (i.e. collections of battery cells) in a car battery and a domestic battery are subject to quite different duty cycles. Car batteries are only rarely filled to 100% or drained to 0 % and avoiding these extremes inhibits many of the physical processes which degrade the battery. In contrast, domestic batteries are frequently filled to 100% and emptied to 0%: this probably happens about 100 times each winter.

So we might think that a domestic battery pack will have a much tougher time than a car battery pack. However, the temperature at which charging and discharging take place is also important, and the Powerwall includes a heating and cooling system and with the battery pack in a semi-sheltered location in the UK, I would guess the cells experience less extreme temperatures during charging and discharging than an EV battery pack.

Summary

So to summarise,  the battery degradation observed so far this winter is less than I expected – and that is a good thing. I’ll be sure to write an update at the end of the winter.

Our Fragile Moment: A Review

Friends, recently I have been writing less because I have been reading and reflecting on “Our Fragile Moment” by Michael Mann.

Click on image for a larger version. The colourful geological graphic is from the NOAA web site.

The book takes a look at Earth’s climate from a geological perspective, highlighting climatic changes in Earth’s history and asking whether what we learn from these changes might be relevant to our current situation.

The answer is “Yes“: we can learn a lot about our current situation by looking at previous non-anthropogenic episodes of Climate Change.

An Epic – but difficult – story

Our Fragile Moment takes us on a rip-roaring tale through Earth’s history in which total global glaciation is followed by a hot-house Earth, and mass extinction ‘events’ appear to be rare, but inevitable occurrences.  But despite the epic scale of the drama, and our compelling motivation to understand such changes, this is not an easy read.

Firstly, the geological naming conventions are arcane and arbitrary. I had a similar sensation to reading novels with long and unfamiliar names (think Tolkien or Dostoevsky) and realising I mixed up two characters with similar names (e.g. Paleocene and Paleozoic).

Secondly, the time scale of Earth’s history is unimaginably long. Human history and prehistory – perhaps the last 3 million years – is less than 0.1% of the age of the Earth. And the rate of change of geological processes is so slow it almost hurts to think about them. It is easy to be unsure about whether ‘snowball Earth’ last millions of years, or tens of millions of years.

Thirdly, the way we infer past climates is not straightforward. Except for ‘recent’ changes (i.e. the last few hundred thousand years) all we have left are rocks, and we have to infer what has happened by evidence left – or not left – in rocks. It’s a kind of ultimate Crime Scene Investigation of the coldest of cold cases. And so there is inevitable uncertainty in working out what has happened.

All this being said, as we evaluate our current situation, the geological perspective is especially valuable, and as an overview of that perspective, the book is valuable. For most of time, no being has been able to understand the present and predict future events. Humanity’s ability to predict climate change is only decades old and is still imperfect – despite using the most detailed and complex computer models. Having historical systems to ‘calibrate’ the models is invaluable.

Lesson #1: The Players 

Some of the ‘characters’ with which have become familiar in discussing our current predicament, come up time and time again as Michael Mann describes what we know of Earth’s Climate Saga:

• water – in the oceans, as rainfall, as vapour, and as clouds.
• carbon dioxide – in the oceans and the atmosphere.
• methane – captured in the biosphere and free in the atmosphere.
• the Sun – it’s variability and stability.
• the Land – its motion around the Earth over geological time.
• life – and it’s influence on atmospheric composition.

As each episode of climate change is described – it eventually becomes clear that it is the same characters as play each time – but each time with a different starting position, and with interactions that are similar, but distinctly different, from previous episodes.

Lesson #2: Feedback 

Whatever event ‘initiated’ an episode of climate change, the evolution of the climate that results depends on the strengths of various responses to the initial change.

Some responses are ‘rapid’ on a geological timescale, and some are slow. For example, if I have remembered correctly, the creation of the Himalayas resulted in enhanced weathering of rock which slowly reduced carbon dioxide concentrations over millions of years, and thus reduced global temperature on a similar timescale.

Some responses re-inforce the initial change – positive feedbacks – and some responses act to reduce the effect of the initial change. In periods where the climate is reasonably stable, the stability is the result of negative feedbacks being larger than positive feedbacks. So in a stable climate small changes to say – the amount of sunlight reaching the Earth – result in changes in (say) ice albedo or cloud cover that negate the initial change.

But this stability only exists for a small range of initial perturbations. Larger perturbations can cause the stability to be lost and positive feedbacks can drive the climate into an entirely different state, which is generally not predictable.

The interplay between these feedbacks plays out time and time and time again through the episodes described in the book.

Lesson #3: The scale of human intervention

When we started emitting carbon dioxide on an industrial scale, humanity was unaware of climatic consequences of the emissions. Now, almost two centuries later, the energy we have released – and are continuing to release – has transformed the way we live – and altered Earth on a geological scale. Our emissions have changed the composition of the atmosphere – increasing the atmospheric concentration of carbon dioxide by about 50% about ten times faster than even the most rapid changes in the geological record.

Lesson #4: What’s going to happen next? 

Fascinating as the story of Earth’s Climate is, what I really wanted to know was whether my doomiest thoughts were justified. Are we already outside the range of change where negative feedbacks will resist us sliding into a new climate paradigm? Unfortunately, it’s still hard to tell. But Michael’s Mann’s interpretation is that the doomiest outlooks are probably not justified.

In the doomiest outlooks, the consequence of the CO2 we have already emitted is that we are already committed to warming way beyond the initial likely warming of 3 °C by 2100. In these outlooks we are already committed to losing the Greenland Ice Sheet and parts of the Antarctic Ice Sheet. This will result in unknown climatic consequences, but will raise global sea levels over the next few centuries by more than 10 metres. Teddington where I live will – along with most of London – be submerged.

Michael Mann’s view is that this outcome – while possible – is not the most likely result. “Our situation is urgent, but we have agency“. He considers that if we act to reduce CO2 emissions now, reaching zero emissions in the coming decades, then the lesson from the relatively-recent Eemian period (about 130,000 years ago) is that we are unlikely to suffer a ‘methane-runaway’ – because the Earth was warmer then and that did not occur then. Sea levels were also higher – but we did not totally lose the ice sheets.

Précis

Michael Mann’s summary is that the reality of the climate change that we are facing right now – this year and in the coming years – is bad enough. We don’t need to motivate ourselves with doomsday scenarios. But we do need to act urgently, because the lesson from Earth’s history is that if we do push the complex, interlinked climate system too far from its stable state – then doomsday scenarios can ensue. And then Our Fragile Moment could be over.

Forthcoming Talks

Friends, have you ever thought “Oh, I wish that nice Michael de Podesta would come and give a talk to our local group about heat pumps, or whether it’s possible to live a ‘net zero’ life.”

Well all you have to do is ask. And if it’s not too far away from Teddington and I’m not too busy, I would be happy to help. There’s a contact form at the end of the article.

My next talk – on Heat Pumps – will be on Wednesday, 6th December 2023 from 7:00 p.m. to 9:00  p.m. upstairs at The Adelaide pub, close to Teddington Railway Station. The talk is organised under the auspices of the IET and is free, but booking is essential – use the link on this page listing my forthcoming talks.

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Heat Pumps: COP envy is pointless

Friends, this week I remembered that I am an idiot.

You may have been aware of this for sometime, and indeed I have known it too, but amidst the buzz of day-to-day activities I forgot. Realisation of my status as a level-10 idiot was triggered by events in my ongoing quest to improve the efficiency (seasonally-averaged COP or SCOP) of my heat pump.

Over the last two winters, the SCOP of my heat pump has been around 3.5, which is a really excellent result – much better than I hoped for when I had the heat pump installed. But the data wizards at Open Energy Monitor have established a dashboard that allows one to monitor dozens of heat pumps across the UK – and many of those installations with the same make and model of heat pump as mine, are achieving SCOPs of 4 and above!

Click on Image for a larger version. Graph showing the performance of the heat pump through the heating seasons of 2021/22 and 2022/23. The red data (read against the left-hand axis) shows the weekly-averaged COP and the red dotted line shows the annually-averaged SCOP. The blue data (read against the right-hand axis) shows the average amount of heat pumped per day in kWh/day. Averaged weekly, 60 kWh/day corresponds to 2.5 kW continuous power.

And friends, I began to wonder what might be causing my system to underperform. Being an experimental physicist, I thought I would try an experiment. This led me to hire HeatGeek elite heat pump ninja Syzmon Czaban to remove the Low Loss Header in my heat pump installation. You can read about that adventure here. But early data indicates that this has made very little difference!

And then I remembered the Golden Rule of Experimental Physics (Do it quick. Then, do it right) and its corollary which states that “Two weeks in the laboratory can save a whole afternoon in the library“. In other words, thinking about things first is harder than just messing about, but it can save a lot of time.

And after thinking about things, I realised something very very obvious: that the SCOP figure is not always a good indicator of heat pump performance, and that my SCOP envy was consequently pointless.  Doh! Allow me to explain.

A model of heat pump performance

Making a model of how a heat pump works is tricky. So I made the simplest possible model with the fewest possible assumptions. And I then considered how the same heat pump would perform in three different dwellings with three different levels of ‘fabric efficiency’ i.e. insulation. I then embedded my model in a spreadsheet which you can download here. Most of the parameters are changeable so you can see how the insights gained might apply to your installation and in the description below I have included my default assumptions in [square brackets].

Click on image for a larger version. Screenshots from the tastefully coloured spreadsheet.

Firstly, for each dwelling I worked out how much heating it required. This assumed:

• There was a background level of space heating due to human heating and electrical dissipation [300 W or 7.2 kWh/day] and that the balance of the heating was supplied by the heat pump. Dwellings with a larger heat transfer coefficient (HTC) require more heat to raise them 1 °C above the outside temperature. [100, 200, 300 W/°C or 2.4, 4.8, 7.2 kWh/day/°C]
• Hot water was suppled by the heat pump [3 kWh/day]
• The total amount of heat supplied was the sum of the two figures above. In summer this would be mostly water heating and in winter this would be mostly space heating.

Secondly, I assumed that each dwelling had the same heat pump installation and that the COP was determined by the indoor and outdoor temperature only. In other words, the COP was not affected by whether the heat pump had to pump just a little heat or lots of heat. I assumed the COP declines linearly as the outside temperature falls, with the COP for the DHW operation being lower because it heated water to a higher temperature.

Click on graph for a larger version. The graph shows how COP is assumed to vary with outdoor temperature for both DHW and space heating. Indoor temperature is assumed to be 20 °C.

Finally I estimated how much electrical energy the heat pump would use by adding three terms together.

• The electrical energy used for space heating is the amount of heat supplied each day divided by the COP for space heating.
• The electrical energy used for DHW is the amount of hot water supplied each day divided by the COP for DHW.
• The background electrical consumption by the computer that operates the heat pump. [20 W or 0.48 kWh/day]

Then I estimated the overall COP for each dwelling by dividing the total amount of heat supplied for DHW and space heating by the total amount of electricity used. The results are shown below.

Click on graph for a larger version. The graph shows how overall COP varies with the amount of heat pumped each day for three properties with good, average and poor insulation. Notice that except in very mild weather (when little heat is delivered), the COP for the poorly insulated home is better than the COP for the well-insulated home.

What this calculation shows is that for identical heat pump installations, a heat pump operating in a well-insulated home will have COP values which are systematically less than a heat pump operating in a poorly-insulated home.

What this means is that over a year, the seasonally-averaged COP (SCOP) will inevitably be larger (better) for a house which requires more heating.

I think this result is both surprising and obvious. It’s counter-intuitive because in general a well-insulated home is easier to heat (with a heat pump or in any other way). But it is also quite obvious because the overall COP is the average of the DHW COP and space-heating COPs, and the more space heating that is performed, the better the expected COP.

Click on graph for a larger version. This is the same graph as shown at the start of the article but with additional labels. It shows how COP for a heat pump is assumed to vary with outdoor temperature for both DHW and space heating. In Summer the average COP is due mainly to domestic hot water heating. As one journeys into winter, the average COP is influenced more by the space heating COP.

Model versus Reality 

All this modelling is very well. But does it correspond to reality? In fact the assumptions I have made are pretty reasonable.

Since my heat pump was installed in August 2021, I have each week recorded the amount of heat it has pumped and the amount of electricity it has consumed. From this I have calculated the weekly-averaged COP. The results for the last three seasons are shown in the figure below.

Click on graph for a larger version. The graph showing weekly-averaged data for my heat pump installation over the last three heating seasons. The graph shows the overall COP versus the amount of heat pumped on average each week. Also shown as a dashed green line is a fit to the 2022/23 data which suggest the maximum achievable COP (on warm days) is about 4.9.

During the coldest days last December 2022, I also evaluated the COP daily (rather than weekly). This was the overall COP including both DHW and space-heating. I noticed that the COP fell roughly linearly with external temperature. Based on this data I think the model describes the basic behaviour of my installation.

Click on graphs for a larger version. Graphs showing data from the cold weather in December 2022. The left-hand graph shows how the daily COP varied as a function of the average external temperature. It fits modestly well to a straight line falling from about ~5 to about ~2 at -10 °C. The right-hand graph shows how the average amount of heat pumped each day varied with the average external temperature.

So I conclude from this that it is reasonable to assume that the COP varies linearly with the external temperature.

COP Envy: A discussion 

So if the model matches the reality,  then my envy of those installations with superior SCOP results is probably misplaced. The most likely cause of my ‘low’ SCOP (and 3.5 is not really low) is that the heat pump simply doesn’t need to do very much space heating: this makes it super-cheap to operate. But it means that in the bulk of the heating season – the times which contribute most to the SCOP – the pump overhead and the amount energy used for DHW was probably the reason that the SCOP did not reach 4.0.

This analysis does not rule out the idea that the installation could be improved. For example, there could be a flow impedance that makes the hydraulic pump work harder than it should. Or my assumption that the COP does not depend on the amount of heat delivered could be flawed because of the way the heat pump cycles on and off at low load. But despite these possibilities, this calculation makes me suspect that the installation probably cannot be improved by much – unless I turn down the temperature to which I heat my hot water – or leave the windows open!

An article about Heat Pumps

 

Click on Image for a larger version. (a) the generic action of a heat pump. It uses electrical energy to draw in heat and move it to a new location at a higher temperature. (b) If insulation is placed around the cold end, a heat pump can create a refrigerator. (c) If insulation is placed around the hot end, a heat pump can create warm a home.

Friends, a few months ago I was asked by Waterline magazine if I would write an article about heat pumps for their Autumn edition. I was puzzled.  Waterline is the journal of the Water Management Society, the trade body for people who specialise is ensuring water is safe from Legionella infection and other related hazards. Why would they want an article about heat pumps?

It turned out not to be a mistake! Being a forward-thinking organisation, they thought their members might want to learn about how wider installation of heat pumps might affect their core ‘mission’. And so I agreed to write an article for them.

I spent a ridiculously long time writing the article. This was partly because of my decaying intellectual capacity and partly because it contains a few original features and graphics that I have not used elsewhere: these took ages to get right.

My contribution is one of several covering a range of aspects of heat pumps.

• The Challenge of Reduced Temperatures in Heating Systems. This article discusses the way various types of bacteria grow and colonise a system involving water storage.
• Heat Pumps: An Overview by David leacher from BSRIA. This is a standard introduction to heat pumps in domestic installations.
• Going ‘Green’ at home: Real Life Costs and Savings by Steve Munn from Hevasure. This is a detailed look at the costs of installing a heat pump and report on the first four months of operation.
• Why so few UK homes are installing Air-Source Heat Pumps – and how to encourage take up, by Emmanuel Pothos and Lee White from City University. These psychologists highlight three fascinating effects: Ambiguity aversion, Loss aversion, and Availability.
• Heat Pumps: The Future of Heating by Michael de Podesta: Me!

Waterline didn’t set a strict word limit, and consequently my article is so long that they only published the introduction in the magazine, and the rest of the article is available on-line. If you would like to read it you can download either Waterline’s nicely-formatted pdf version, or alternatively download my boringly-formatted version. Please note that my version is copyright free – but Waterline’s typesetting is copyrighted.

Contents.

This is a description of the contents of the article. As I now do at all my talks, I start by clearly addressing the so-called ‘climate sceptics’ that lurk in every audience I address.

In this article I will look at what heat pumps do and how they do it (Section 3), and then look at some details of their design (Section 4). I will then (Section 5) describe a typical domestic installation of a heat pump and its role in space heating and the preparation of domestic hot water. I will then (Section 6) discuss the costs of a domestic heat pump installation. Finally (Section 7), I will briefly outline applications of heat pumps for process heating in different industrial sectors.

But before embarking on this journey, I hope you will please allow me to explain briefly why this matters as much as it does. In every audience I have addressed over recent years I have found that there are people who feel – despite the indisputable facts of the warming globe – that our climate crisis is a hoax of some sort and that – to quote our former Prime Minister – renewable technologies are just ‘green crap’. This section is addressed to those people reading this who choose to disbelieve the overwhelming evidence of the harmful effects of carbon dioxide emissions and who apply to themselves the label: ‘climate sceptic’.

Anyway: if you are looking for a general article about heat pumps, this may fit the bill.

Heat Pump Experiment: First Results

Friends, it’s been a couple of weeks now since I had the Low-Loss Header (LLH) removed from my heat pump installation (description here) and I thought you might like to know how the installation was performing.

In short, it’s performing very similarly to how it was performing with the LLH. The longer version follows:

Performance: Temperatures

Below are various graphs showing 3½ days of data from midnight on 15th October.

The first graph shows the internal temperature through the period. The set temperature was 20 °C and heating control was entirely by weather compensation i.e. the heating power is determined entirely by the outside temperature.

Click on graph for a larger version. The internal temperature of the house slowly approaching the set temperature of 20 °C. The heating is controlled entirely by weather compensation i.e. the heating power is set solely by the outside temperature.

The graph below shows how shows various system temperatures varied during the monitoring period.

Click on graph for a larger version. The graph shows how various system temperatures measured during the days following 15th October. The blue line is the outside temperature.  The orange line is the internal temperature also shown in detail in the graph above. The grey dots show the flow temperature in the radiators measured every 2 minutes, and the red line shows the same data averaged hourly. The purple dots show the temperature of the water used to heat the domestic hot water tank. The cycle in the early hours of the 18th is the weekly anti-legionella cycle.

Concentrating on the space-heating performance alone we can simplify the graph above by just using hourly averages and omitting the hot-water heating cycle.

Click on graph for a larger version. Simplified version of the previous graph. The blue line is the outside temperature.  The orange line is the internal temperature and the red line shows the flow temperature.

This allows us to see much more clearly the astonishing perfection of weather compensation: the flow temperature is increased (and decreased) in response to the decreases (and increases) in the external temperature: no internal thermostat is used. The setting to achieve this result was as follows:

• The ‘heating curve’ was set to 0.45. This number is a label for one of a set of curves which describe the heat loss of a dwelling as the external temperature falls.
• The ‘O/T threshold’ (O/T is short for outside) was set to 14 °C. This is the temperature above which the heating circuit will be inactivated.
• R/T modulation (R/T is short for room temperature) was set to ‘inactive’ which corresponds to just using the outside temperature to set the heat pump power.

There are a couple of interesting features of this data.

• Firstly, the outside temperature shown is captured by the monitoring system from a weather station a few miles from my home. In operation, the heat pump uses a temperature sensor place outside the house. The two sensors give similar results, but heat pump operation is based only on the local sensor. I think this is why there is a lag between the flow and outside temperatures which is particularly clear on the morning of the 16th.
• Secondly, since the LLH removal (on 7th October 2023) the main problem had been that the house had stayed too hot – typically 22 °C – and didn’t seem to cool. But finally, on the night of 16th October 2023, the outside temperature fell to 3 °C – passably cold – which helped the heating system to come into equilibrium.

So regarding the system performance, it is clear that the heat pump can keep the house warm when it gets cold outside. In some sense, this is all that matters. But how was the efficiency of the heat pump during these few days?

Performance: Heating and Electrical Power

Below are graphs showing the electrical power consumed and the thermal power delivered. The first graph shows data taken every two minutes, and it is clear that as the weather gets colder on the night of the 15th, the heat pump operates on longer and longer cycles. These increase in length from about 30 minute on-off cycles at midday on the 15th, to operating continuously once the outside temperature falls below roughly 7 °C.

Click on graph for a larger version. Top: Graph showing electrical power consumption (kW) and thermal output (kW) over the monitoring period. Data are taken every 2 minutes. Bottom: details of the cold night from midday on the 15th October to midday on the 16th.

We can see that in the early hours of the 16th October, the electrical power is around 600 W, and the heating power is around 1.8 kW corresponding to a COP of about 3. This is not bad, but not great either.

This view is interesting – showing the dynamics of the heat pump – and indicating that it needs a heating demand of approximately 1.8 kW – approximately 36% of its nominal output – in order to operate continuously.

We can get a more general idea of what is happening if we average the power measurements over an hour. This data is shown below.

Click on graph for a larger version: Graph showing electrical power consumption (kW) and thermal output (kW) over the monitoring period. This is the same data shown in the previous graph but now averaged over 1 hour.

Based on these averaged power measurements we can calculate the COP by dividing the thermal output data by the electrical consumption data. This is shown below.

Click on graph for a larger version: Graph showing Coefficient of Performance (COP) over the monitoring period obtained by dividing the thermal output data by the electrical consumption data. Also shown against the right-hand axis in blue is the external temperature (°C)

We see that the COP falls to around 2.5 to 3.0 during DHW or Anti-legionella cycles. When the heat pump is used for space-heating, the COP varies between ~3.0 when the outside temperature is 3 °C, and ~3.9 when the outside temperature is 12 °C. I don’t have exactly comparable data, but looking back at data from December 2022 , this data looks similar.

Click on graph for a larger version. Graph showing COP versus external temperature when the internal temperature is 20 °C. The blue dots show daily averages of COP (including DHW cycles) from December 2022. The green circles show rough estimates of COP (excluding DHW cycles) from October 2023.

Conclusion

The good news from this preliminary examination is that the installation does not appear to perform obviously worse than it did with the Low-Loss Header.

However the bad news is exactly the same: the installation does not appear to perform noticeable better than it did with the Low-Loss Header.

As you might expect, I will be gathering data as the winter progresses.