Archive for the ‘Climate Change’ Category

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

Michael

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

Chorus

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?

Chorus

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

Chorus

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

Chorus

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)

Chorus

 

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.

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)

It’s been a sunny summer

September 1, 2022

Friends, it’s the 1st September: the first day of meteorological autumn. So this seems like a good time to look at solar PV generation this summer.

In case you can’t be bothered reading much further – and I would sympathise with you there – the précis is this:

  • It’s been a sunny summer.

Also comparing generation with consumption, I have devised a plan to try to increase the length of time the house is ‘off-grid’ from 4 months, to 6 months!

The Solar Installation

The 12 solar panels (340 W-peak Q-cells DUO BLK-G8) were installed in November 2020 and have been working flawlessly since.

They are installed on the sloping South and Western roofs of Podesta Towers in Teddington.

Click on image for a larger version. The arrangement of the solar cells on the roof of Podesta Towers.

2021 vs 2022

The figure below shows monthly generation for 2021 and 2022

Click on image for a larger version. Monthly generation – expressed as kWh/day – since installation in November 2020.

Looking at data above, it’s clear that (with the exception of April) generation in every month of 2022 has been larger than generation in the equivalent month in 2021

The sunny nature of 2022 also shows up in the cumulative generation data:

Click on image for a larger version. Cumulative generation in kWh throughout and 2021 and 2022. Also shown the are amounts of electricity exported.

Generation to date this year (3,140 kW) is 12% ahead of cumulative generation in 2021 (2,800 kWh). And exports to date (1,004 kWh) have already exceeded exports in the whole of 2021 (880 kWh).

For completeness, I also include the daily generation graph, but the fluctuations in this are so large that it can be difficult to interpret.

Click on image for a larger version. Daily generation in kWh/day for 2022 is shown in green. Also shown is a ±2 day running average from 20202021 and 2022. The yellow data show the expected generation based on the EU -PV sunshine database.

Analysis: Solar as a fraction of demand

The three charts below are not based upon the solar year – January to December – but the heating year July to June. Somehow this seemed more natural.

The first chart shows our typical demand for electricity through the year – an average of 9.8 kWh/day over the period July 2021 to June 2022.

Also shown (in darker green)  is the electricity used by the heat pump for space heating. This peaked in January 2022 at around 15 kWh/day making a peak demand of 25 kWh/day.

Click on image for a larger version. Average Daily electricity demand in kWh/day shown from July 2021 to June 2022. The light green section of the bars shows normally daily demand (9.8 kWh/day) and the dark green section shows electricity used by the heat pump for space heating.

The second chart shows the daily solar generation from 2021/2022. It’s clear that solar generation is irritatingly – but obviously – out-of-phase with demand.

Click on image for a larger version. Average Daily generation in kWh/day shown from July 2021 to June 2022.

The final chart shows the ratio of the two charts above showing the fraction of average demand that is met by average solar generation. This final chart is interesting.

Click on image for a larger version. The ratio of average generation to average electricity demand through the year.

First of all let’s note that this is based on just one year’s data and year-to-year variability is typically 10%. But this data shows that there are 4 months of the year (May, June, July and August) where average solar generation is able to meet average demand with more than 10% margin. And indeed with the aid of our battery, we have been off-grid for most of that time this year.

But the graph also shows that there are two more months – April and September – where average solar generation is able to meet average demand, but with a margin of less than 10%.

This means that if I could increase solar generation by even a relatively small amount, it might be possible (if the fluctuations are not too large) to take the house off-grid for a full 6 months of the year. Wow! I am getting excited at the very thought of this!

Plan

And friends that is my plan. I have asked a solar installer to add an additional 9 panels onto our array: 5 panels on the roof facing 25 °N or East and 4 on the flat roof nominal facing 25° east of south.

This addition takes the array over the 4 kW-peak installation that can be done without notifying the electricity distribution company, but the installer has told me the application is already submitted.

My hope is that over a year, the additional 9 panels will add ~1,500 kWh (167 kWh/panel) to the ~3,600 kWh (300 kWh/panel) generated by the existing 12 panels. This should be enough to raise generation in April and September above demand, and hopefully allow us to stay off grid for a whole half of a year.

Click on image for a larger version. The location of the panels in Phase#2 of the Podesta Solar Array are shown in red.

These orientations aren’t the best, but actually they are not terrible! And generating over 1 MWh per year is not negligible!

Of course, I still don’t have a date, or even an expectation of a date for doing this work.  But hopefully the panels and inverters will eventually make themselves available in the first few months of next year – hopefully before April!

Note on Embodied Carbon

I am able to afford this because although my pension lump sum is all spent, living modestly and not having to pay big bills, I have been able to save enough of my monthly pension to buy the extra panels.

And having made rough estimates of what is done with my savings, I think the best thing I can do with any resource I have available is to spend it on things that reduce carbon emissions. And there are only one or two things out there that have better ‘carbon value’ than solar panels.

Anyway: That’s the plan…

Non, Je ne regrette rien: update

August 26, 2022

Friends, last week I wrote about my embarrassingly low energy bills, and compared them with the shockingly high energy bills I would be facing if I had spent my pension lump sum on a world cruise and a car: Non, je ne regrette rien.

But after writing that article, I quickly realised that it needed updating.

  • Firstly,  although I have agreed an electricity contract for the year to September 2023, I underestimated how much I would have had to pay for gas. These new ‘energy cap’ prices were estimated early this week and confirmed today.

Energy Cap Prices (Source: Cornwall Insight)

  • Secondly, several people were puzzled about how I did the calculations for both my actual gas and electricity use, and the counterfactual estimate.

In this article I hope to clarify both of these issues.

Modelling Consumption Patterns

Since November 2018 I have read my gas and electricity meters each Saturday morning and so I know my weekly gas and electricity consumption for the last 4 years or so.

This allowed me to get a characteristic consumption pattern from June 2019 to May 2020 before the External Wall Insulation, Solar Panels, Battery and Air Source Heat Pump were installed.

To model the alternative counterfactual reality I have imagined that the 2019/20 pattern of consumption simply repeated indefinitely. I could then compare that with what has actually happened.

Modelling Costs

I have then assumed different costs for different periods as summarised in the table below.

Click for larger version. These are the prices per unit and daily charges that I have assumed. See text for details.

Working out these costs has been tricky.

Historically, I don’t recall the price of either electricity or gas changing much for the many years we have been in the house. It was not until EDF increased the price of cheap electricity by 73% that I thought to look elsewhere, and I switched to Octopus energy a year ago in August 2021.

I signed a fixed-price 1 year deal for electricity that gave me 4 hours of electricity at 5p/kWh and a peak rate of 16p/kWh.

I recently renewed that deal at increased rates of 7.5p/kWh off-peak and 46p/kWh peak.

The gas charge changes with the market and has increased from around 3p/kWh to around 7.3p/kWh but I expect that to increase

Looking ahead I have assumed that in a year’s time I will renew the electricity contract with a similar deal that will be more expensive.

Regarding future gas prices, I have assumed ‘Energy Price Cap Prices‘ for October 2022 that have recently been published. I have made conservative guesses for how these prices will vary in future – but I expect them to increase throughout the whole of 2023.

I have not included any government interventions.

Actual Costs 

The graphs below show my actual electricity and gas costs over the last three and half years, and my projected costs for the next year and a half.

Click on image for a larger version. My weekly gas and electricity costs for the last three and a half years. Also shown in red is my projection for my bills based on currently signed contracts. The figures in boxes show yearly costs. Note the vertical scale is £120/week – much larger than the scale I used in my previous article.

 

Prior to 2021 electricity usage was pretty constant at around 10 kWh/day costing around £15/week.

But after the installation of solar panels and a battery, the pattern of consumption of grid electricity changed significantly, with the house being almost off-grid for three to four months a year, and with electricity consumption usage peaking in winter.

The winter costs of this are low – peaking at £15/week – because we buy most of our electricity ‘off-peak’ and store it in the battery and then run the household from the battery for most of the next day.

Looking ahead, (red) if I assume that the coming winter is similar to last winter, then these projected costs will increase in the year ahead.

Regarding gas usage, one can see the winter consumption declining year-on-year as a result of first triple-glazing and then External Wall Insulation.

And then in 2021 gas usage flatlines after the installation of the Air Source Heat Pump. The residual gas usage is just for cooking – roughly 1 kWh/day – which I hope to stop in the next few months by switching to an induction hob – that’s why the projected gas costs for 2023 are zero.

If I had done nothing 

The graphs below show my estimates for gas and electricity costs assuming I had not installed External Wall Insulation, Solar PV, a battery and an Air Source Heat Pump.

Click on image for a larger version. Estimated weekly gas and electricity costs for the last three and a half years assuming that I had not installed External Wall Insulation, Solar PV, a battery and an Air Source Heat Pump. Also shown in red is my projection for the coming year. The figures in boxes show yearly costs. Notice that the vertical scale of this graph is £120/week – much larger than the scale I used in my previous article.

The same patterns of electricity and gas usage are repeated year after year.

The effect of forthcoming price rises for 2023 are estimates based on Octopus Energy prices.

I have assumed that the electricity price is fixed and so not affected by energy price cap rises. I have not assumed any increase in September 2023 after the fixed deal comes to an end, but there will probably be a rise of some kind.

However gas costs are extremely high and subject to whatever the market demands.

The small reduction in 2023 electricity costs (£1,447) versus 2022 (£1,475)  is because the calculation is based on weekly consumption and one year has a nominal 53 weeks versus a nominal 52 in the other year.

Comparison

Finally, the graph below compares the actual bills I have paid with my estimate for what I would have paid if I had not improved the house. The graph combines gas and electricity costs.

Click on image for a larger version. Comparison of the actual annual combined gas and electricity bills with the counterfactual scenario in which I had not installed External Wall Insulation, Solar PV, a battery and an Air Source Heat Pump. Figures for 2023 are – obviously – projections. Notice that the project costs that I would have incurred are much larger than I estimated in my previous article.

I have stared at this graph over and over and thought: Michael: you have made a mistake. And that may be true. But if I have, I can’t find it.

The models have many assumptions and some may be not quite right. But I don’t think the figures are wrong by more than about 10%.

Payback Calculation

The difference between the two realities in the graph above is – in round terms – currently around £2,000/year and will likely grow to around £4,000 year in 2023 – much larger than I calculated in my previous article.

The difference in expenditure between the two realities is External Wall Insulation (£27k), Solar PV(£4k), a battery (£10k) and an Air Source Heat Pump (£8k) which comes to around £50k.

So the return on my investment is currently 4% and might rise to 8% – which is much better (for me) than I had thought.

Something must be done

The impact of forthcoming price rises is hard to comprehend. The consequences for people with low incomes are dire – and the consequences for hospitals, schools, libraries and business are also frightening.

Clearly ‘something must be done, but I have no confidence that any measures will be well-targeted. Obviously giving people like me more money is bonkers!

But whatever financial steps are taken, I hope the that one lesson will be learned: we need a renewable energy initiative on a wartime scale to build more wind and solar farms as rapidly as possible. If done at scale this could transform our energy infrastructure within a decade.

Non, Je ne regrette rien

August 18, 2022

=============================
UPDATE:

I have recalculated some of these costs using the latest ‘price cap’ figures.
Please see the next article for details.

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

Friends, one of the questions I am most often asked about the works I have had done on my house concerns the “Return on Investment” or “Payback Time”.

I hate this question for three quite distinct reasons.

Reason 1

Firstly, I hate it because it indicates that the questioner has misunderstood the nature of work I have undertaken.

For example, if someone has a leaking sewer repaired one doesn’t ask them about the “payback time”. Why? Because it’s just wrong to leak raw sewage into a public area. The repair is necessary.

That’s how I feel about putting carbon dioxide into the atmosphere when one has an alternative. It is similarly disgusting, except that carbon dioxide is dramatically more damaging in its effects than sewage.

Reason 2

Secondly, I hate it because the answer is quite difficult to work out!

I have never paid much attention to the magnitude of electricity or gas bills – I could afford them and I had no alternative but to pay!

I am conscious that the bills now are much smaller than they used to be, but it’s quite a lot of work to figure out exactly how much smaller. But that is what I have have done in this article.

Method

Since November 2018 I have read my gas and electricity meters each Saturday morning and so I know my weekly gas and electricity consumption for the last 4 years or so.

I have then trawled back through my records to find historical standing charges and unit rates, and re-constructed the actual weekly costs.

I have then modelled what the weekly costs would have been if we had not installed External Wall Insulation, Solar Panels, a Battery and an Air Source Heat Pump.

To do this I took the consumption between mid-2019 to mid 2020 and assumed that these patterns of consumption were repeated in future years. I have then re-calculated the weekly and annual costs.

Actual Costs 

From this data I can calculate weekly costs for electricity and gas, and then by adding up the costs for 52 weeks I can get an estimate of the annual costs. The results for my actual electricity and gas costs are shown in the figures below.

Click on image for a larger version. My weekly gas and electricity costs for the last three and a half years. Also shown in red is my projection for my bills based on currently signed contracts. The figures in boxes show yearly costs.

=============================
UPDATE:

I have recalculated some of these costs using the latest ‘price cap’ figures.
Please see the next article for details.

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

These graphs tell quite a story.

Prior to 2021 electricity usage was pretty constant at around 10 kWh/day costing around £15/week.

But after the installation of solar panels and a battery, the pattern of consumption of grid electricity changed significantly, with the house being almost off-grid for three to four months a year, and with electricity consumption usage peaking in winter.

The winter costs of this are low – peaking at £15/week – because we buy most of our electricity ‘off-peak’ and store it in the battery and then run the household from the battery for most of the next day.

Looking ahead, (red) if I assume that the coming winter is similar to last winter, then these projected costs will increase in the year ahead.

Regarding gas usage, one can see the winter consumption declining year-on-year as a result of first triple-glazing and then External Wall Insulation.

And then in 2021 gas usage flatlines after the installation of the Air Source Heat Pump. The residual gas usage is just for cooking – roughly 1 kWh/day – which I hope to stop in the next few months by switching to an induction hob – that’s why the projected gas costs for 2023 are zero.

If I had done nothing

The graphs below show my estimates for gas and electricity costs assuming I had not installed External Wall Insulation, Solar PV, a battery and an Air Source Heat Pump.

Click on image for a larger version. Estimated weekly gas and electricity costs for the last three and a half years assuming that I had not installed External Wall Insulation, Solar PV, a battery and an Air Source Heat Pump. Also shown in red is my projection for the coming year. The figures in boxes show yearly costs. Notice that the vertical scale of this graph (£50/week) is different to the earlier graphs (£30/week).

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UPDATE:

I have recalculated some of these costs using the latest ‘price cap’ figures.
Please see the next article for details.

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The same patterns of electricity and gas usage are repeated year after year.

The effect of forthcoming price rises for 2023 are estimates based on Octopus Energy prices.

Comparison

Finally, the graph below compares the actual bills I have paid with my estimate for what I would have paid if I had not improved the house. The graph combines gas and electricity costs.

Click on image for a larger version. Comparison of the actual annual combined gas and electricity bills with the counterfactual scenario in which I had not installed External Wall Insulation, Solar PV, a battery and an Air Source Heat Pump. Figures for 2023 are – obviously – projections.

=============================
UPDATE:

I have recalculated some of these costs using the latest ‘price cap’ figures.
Please see the next article for details.

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

Payback Calculation

So now we come to the third reason that I dislike calculating ‘Payback’: it is not very large.

The difference between the two realities in the graph above is – in round terms – currently around £1,000/year and will likely grow to around £2,000 year in 2023.

But the difference in expenditure between the two realities is External Wall Insulation (£27k), Solar PV(£4k), a battery (£10k) and an Air Source Heat Pump (£8k) which comes to around £50k.

So the return on my investment is just 2% and might rise to 4% – with payback periods of many decades.

But on the other hand, most people in the UK are at least slightly anxious about energy bills in the coming years, but I am not in the least concerned. And surely that has to be worth something too.

I honestly don’t regret a penny of the expenditure.

=============================
UPDATE:

I have recalculated some of these costs using the latest ‘price cap’ figures.
Please see the next article for details.

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

How big is that fire?

August 12, 2022

Click on the image for a larger version. The picture is courtesy of Michael Newbry.

Friends, you may have noticed that we have recently entered a period of what is euphemistically called “enhanced risk of wildfires”.

And reports of wildfires from around the world include some truly apocalyptic images.

But many of these reports fail to communicate clearly one of the key metrics for fires: the size of the fire.

Some reports do mention the area affected in hectares (abbreviated as ha) or acres, but while I can just about grasp the meaning of one acre or one hectare – I struggle to appreciate the size of a fire covering, say, 6,000 hectares.

In order to convert these statistics to something meaningful, I work out the length of one side of a square with the same area.

Areas expressed in hectares.

A hectare is an area of 100 m x 100 m, or 0.1 km x 0.1 km so that there are 100 hectares in a square kilometre.

So to convert an area expressed in hectares to the side of the square of equal area one takes two steps.

  • First one takes the square root of the number of hectares.
  • One then divides by 10.

So for a fire with an area of 6,000 hectares the calculation looks like this:

  • √6,000 = 77.4
  • 77.4÷10 = 7.74 km

Since the original area was probably quite uncertain I would express this as being equivalent to a square with a side of 7 or 8 km.

Areas expressed in acres.

An acre is an area of 63.6 m x 6.36 m, or 0.64 km x 0.64 km so that there are roughly 2.5 acres in a hectare.

I can’t think of an easy way to get a good approximation for acres, but a bad approximation is better than no estimate at all. So I recommend, the following 3- or 4-step process:

  • First one divides the number of acres by 2
  • Then one takes the square root of half the number of acres.
  • One then divides by 10.
  • This answer will be about 10% too large.

So for a fire with an area of 15,000 acres the calculation looks like this:

  • 15,000÷2 = 7,500
  • √7,500 = 86.6
  • 86.6÷10 = 8.7 km

At this point one can either just bear in mind that this is a slight over-estimate, or correct by 10%. In this context, the overall uncertainty in the estimate means the last step is barely worthwhile.

How bad is the situation in Europe?

Click on Image for larger version. Estimates of the cumulative area (in hectares) burned by wildfires in each of the EU countries. The red bars show data for this year, and the blue bars show the average area burned between 2006 and 2021.

There is a wonderful website (linkwhich publishes estimates of wildfire prevalence in all the countries of the EU. One output of the website is shown above:

  • The blue bars shows the average area burned from 2006 to 2021
  • The red bars shows the average area burned so far this year.

You can immediately see that Spain, Romania, and France are having bad years for wildfires.

But how big an area is 244,924 hectares – the area burned in Spain so far? Using the rule above, one can see that it is an area equivalent to a square with a side of 50 km – roughly equivalent to (say) the area of Cheshire.

The area burned in France so far this year is 60,901 hectares. Using the rule above, one can see that it is an area equivalent to a square with a side of 25 km.

Michael, what was the point of this article?

When trying to visualise large areas expressed in hectares (or acres) I find it useful to work out the length of side of a square which would have the same area.

Tips for talking about Climate Change

August 8, 2022

Friends, isn’t it funny how sometimes you come across something at just the right time.

And since I have now become one of the ‘mad people’ you have to avoid eye-contact with as you walk past me in the street, I was happy to come upon these notes on Talking about Climate Change.

The notes were prepared by Richard Erskine as part of his work to raise consciousness of Climate Change in his local area. And the aim is to simply share some experiences and ideas about dealing with some of the most common situations one encounters.

  • You can find Richard’s blog here
  • You can follow him on Twitter here.
  • And you can download the notes as a pdf file here.

There is no point in me re-writing what Richard has written, but I thought I would just highlight some of the things the document covered that I felt were especially delightful. And the main feature I liked was the subtitle: you don’t have to be an expert.

On my first day out, I went equipped with a laptop loaded up with key graphs and animations. On contact with the public it immediately became obvious that these would not be needed. Talking to people in the street is absolutely NOT about lecturing clearly. And although Richard’s notes include some well-referenced ‘facts’, it is not about knowing the very latest facts.

The point of speaking to people in the street lies in the power of conversation, and the sheer pleasure humans take in ‘having a chat’. And meeting someone who is honest and straightforward and concerned, and not trying to sell anything is a pretty powerful event in most people’s days.

Contents

The document starts with some tips on starting conversations and some key Climate Facts. And then there are 10 questions which I have listed below together with my précis of the Richard’s more expansive comments.

Q1. CO2 is only a trace gas (0.04%) of the atmosphere. How can that affect the climate?

  • This drink contains 0.04% cyanide, would you like some?

Q2. CO2 is used by plants so isn’t more of it a good thing

  • Yes, CO2 is used by plants, but it also affects the climate, and many plants can’t cope with heat-induced stress. Look at the grass…

Q3. We’ve had heat waves before (1976) so what’s the fuss?

  • Heat waves have become more likely year-on-year, and this one has extended across much of the northern hemisphere. Reaching 40 °C in the UK would have been impossible without the underlying warming.

Q4. Aren’t Electric Vehicles (EVs) environmentally bad?

  • EVs are much better for the environment than petrol and diesel cars, but they are not perfect.

Q5. Don’t we need better public transport rather than Electric Vehicles (EVs)?

  • This is not an “either-or” decision.

Q6 What about China; our emissions are tiny compared to theirs?

  • China’s per person and historic emissions are much lower than ours, and they have become the factory of the world. Many items you own were probably made in China. 

Q7. The problem is population growth, so what can we do, and is it even worth trying?

  • This places the blame on the poorest people in the world who have NOT caused global warming. The problem is caused by our society’s consumption.

Q8. “What’s the big deal about the world warming by 1°C or 2°C?”

  • Like your body, the climate and ecology of the Earth are adapted to living at a particular temperature. Just like you, a rise in temperature of 2  °C or 3 °C is very serious.

Q9. Arctic methane and other tipping points have already been crossed, so we need to now just prepare for the worst, don’t we?

  • We don’t have runaway Climate Change yet – and we want to avoid that. So every action matters, every bit of warming matters, every choice matters.

Q10. I am not a denier, but we can’t afford to rush it; Net Zero by 2050 is just an arbitrary target, we need more time

  • It is not a choice between the economy and climate change measures. With consistent policies and investment in a low carbon economy, we can actually have a flourishing future, good for jobs and the planet.

Conclusion

Friends, Climate Change is real and terrifying, and it is easy to feel petrified into inaction. But having honest conversations with friends and acquaintances is a great way to clarify one’s own thoughts and to help others clarify theirs.

But our conversations have been seeded – deliberately I believe – with false narratives that

  • either deny that Climate Change exists,
  • or if it exists that it is important,
  • or if it is important that it’s our responsibility,
  • or if its our responsibility that we can afford to do anything
  • or if we do anything that it is just as bad as everything else

These notes might just help you to avoid getting sucked into those awful conversational paths.

Good Luck!

Sodium Acetate: Fun in the Kitchen with Phase Change Experiments

August 7, 2022

Friends, you may recall that in a recent article I wrote about Phase Change Materials (PCMs) used for thermal storage. I illustrated that article with a measurement of the temperature versus time as some molten candle wax solidified. I then tried to work out how much so-called ‘latent’ heat was released as the wax solidified.

A Twitter source then told me that the actual material used in commercial thermal storage units was sodium acetate trihydrate, and within 18 hours, a kilogram of the substance was delivered to my door.

NOTE: In this article I have used the term sodium acetate to mean sodium acetate trihydrate and in some locations it is abbreviated to SAT.

NOTE: Sodium acetate is pretty safe from a toxicity perspective: it’s an allowed food ingredient E262, but one needs to be careful not to scald oneself – or others – when handling the hot liquid.

So I began a series of experiments in which I made a great variety of very different, but similarly basic, errors. There really is nothing like a practical experiment for making one feel incompetent and stupid! Part of the problem was that I was trying to do other things at the same time as reading the temperature of the two samples (wax and sodium acetate).

To overcome these difficulties,  I eventually bought a thermocouple data-logger which can read up to 4 thermocouples simultaneously and save the data on an SD card. This allowed me (a) get on with life and (b) to do something clever: to measure the cooling curve of a sample of water at the same time. I’ll explain why this was important later.

Eventually – after a series of new basic mistakes such as setting the logging interval to 30 minutes rather than30 seconds – I began to get some interesting data. And sodium acetate really is an extraordinary substance.

Of course my experiments are not complete and I would really like to repeat the whole series of experiments based on the golden rule, but I really need to the clean up the kitchen.

Experiment#1

As shown below, I heated three samples of equal volumes of wax, sodium acetate and water to roughly 90 °C for around 10 minutes – sufficient to melt all the SAT.

I then transferred the samples – while logging their temperature – into a cardboard stand where I guessed that the cooling environment of each sample would be similar.

The results of the first experiment are shown below.

Click on image for a larger version. The temperature of the three samples of water, wax and sodium acetate as a function of time.

The first thing to notice is how odd the curves are for the wax and the sodium acetate. They both have discontinuities in their rate of cooling.

And strikingly, although they start at similar temperatures, they both stay hotter than the water for longer – this is what makes them candidate thermal storage materials. But precisely how much more heat have they released?

To work this out we need to start with the cooling curve for the water which (happily) behaves normally i.e. smoothly. We would expect…

  • …the cooling rate (°C/s) to be proportional to…
  • …the difference between the temperature at any particular time, and the temperature of the environment (roughly 27 °C during Experiment #1).

Using the magic of spreadsheets we can check if this is the case, and as the graph below demonstrates, it is indeed approximately so.

Click on image for a larger version. The cooling rate of the water  as function of the difference between water temperature and the temperature of the environment.

Because the heat capacity of water is reasonably constant over this temperature range, we can now convert this cooling rate into an estimate of how much heat was leaving the water sample at each temperature. To do this we note that for each °C that each gram of water cools, 4.2 J of heat must leave the sample. So if 1 gram of water cools at a rate of 1 °C/s, then the rate of heat loss must be 4.2 J/s or 4.2 W.

Click on image for a larger version. Estimate for the rate of loss of heat (in watts) of the water as function of the difference between water temperature and the temperature of the environment.

This last graph tells us that when the temperature difference from the environments is (say) 10 °C, then the water is losing 0.104 x 10 = 1.04 watts of heat. Based on the closeness of the fit to the data, I would estimate there is about a 10% uncertainty in this figure.

Finally, if we add the amount of heat lost during the time interval between each data point, we can estimate the cumulative total amount of heat lost.

It is this cumulative total that indicates the capacity of a substance to store heat.

Importantly, because all the samples are held similarly, at any particular temperature, I think the heat loss from each of the other samples must be the similar to that for water when it was at the same temperature – even though the cooling rates are quite different.

Using this insight, I converted the cooling curve (temperature versus time) for these materials – into curves showing cumulative heat loss curves versus time.

Click on image for a larger version. Estimates for the cumulative heat lost from the water, wax and SAT (sodium acetate) samples as a function of time. Also shown as dotted lines are the limiting extrapolations from (a) the first part of the cooling curve of the SAT and (b) the final part of the cooling curve. The difference between these two extrapolations is an estimate for the latent heat of the SAT.

We can apply a couple of sanity checks here. The first is that the heat lost from the water comes to about 10.7 kilojoules. Since the 60 g of water cooled from 70 °C to 28 °C then based on a heat capacity of water of 4,200 J/°C/kg we would expect a heat loss of (0.06 x 4200 x 42 =)10.6 kJ. This rough numerical agreement just indicates that the spreadsheet analysis has not resulted in any gross errors.

Looking at the difference between the extrapolation of the first part of the SAT curve, and the extrapolation of the final curve, we see a difference of approximately 23.8 kJ. This heat evolved from 88 g of SAT in the tube and so corresponds to 23.8/0.088 = 270 kJ/kg. We can check that against an academic paper, which suggests values in the range 264 to 289 kJ/kg. So that too seems to check out.

With everything sort of working, I tried the experiment a couple more times

Further Experiments: coping with super-cooling

The most striking feature of these experiments is that when the sodium acetate freezes, it releases its ‘latent heat’ and warms up to its equilibrium freezing temperature of roughly 58 °C.

From the first experiment – and the experiments I had done previously – it became clear that the sodium acetate tended to supercool substantially. This is the process whereby a substance remains a liquid even when it is cooled below its equilibrium freezing temperature.

[The physics of supercooling is fascinating but I don’t really have time to discuss it here. In facile terms, it is like when a cartoon character runs over the edge of a cliff but doesn’t fall until it realises that there is nothing holding it up!]

In this context, the supercooling is just an irritation! So I tried different techniques in each of the three difference experiments

  • In Experiment #1, I stirred the sample to initiate the freezing.
  • In Experiment #2, I placed spoons in each sample in the hope that some additional cooling would initiate the freezing. It didn’t.
  • In Experiment #3, I left the sample for as long as was practical in the hope it would spontaneously freeze. It didn’t.
  • In Experiment #4, I left the sample for longer than was practical. But it still didn’t freeze spontaneously.

So I didn’t manage to control the supercooling – in each case I initiated the freeze by poking, shaking or stirring. I’ll comment on this failure at the end of the article.

The data and analysis from experiments 2, 3 and 4 is shown below.

Click on image for a larger version. The upper three graphs show 3 cooling curves for wax and SAT. The water sample is not shown to simplify the graphs. The Lower 3 graphs show estimates for the cumulative heat lost from the wax and SAT samples as a function of time. Also shown as dotted lines are the limiting extrapolations from (a) the first part of the cooling curve of the SAT and (b) the final part of the cooling curve. The difference between these two extrapolations is an estimate for the latent heat of the SAT.

Conclusions

The most important conclusion from the analysis above is that a given volume of SAT releases much more thermal energy on cooling than the equivalent volume of either water or wax. This what makes it useful for thermal storage.

If we consider heat released above 40 °C, then the SAT releases around 3 times as much heat as a similar volume of water. This means an equivalent thermal store built using SAT can be up to 3 times smaller than the equivalent thermal store using a hot water cylinder.

The experiments gave four estimates for the heat related as latent heat which are summarised in the table below. Pleasingly all are in reasonable agreement with the suggested likely range of results from 264 to 289 kJ/kg.

Click on image for a larger version. Three estimates of the latent heat of Sodium Acetate Trihydrate (SAT)

Practical Devices

Scaling to a larger sample, 100 kg of sodium acetate would occupy a volume of 68 litres and fit in a cube with a side of just 40 cm or so, and release around 27MJ (7.5 kWh) of latent heat. This is roughly the equivalent of the heat stored in a 200 litre domestic hot water cylinder.

Sodium acetate is the thermal storage medium in a range of devices that can serve the same purpose as a domestic hot water cylinder but which occupy (in practice) rather less than half the volume. Clever!

Heat is stored by melting the sodium acetate in an insulated box, and released by running cold water through pipes immersed in the sodium acetate: the water is heated and emerges piping hot through your taps! As the sodium acetate freezes, the temperature remains stable – and the water delivered similarly remains piping hot.

But what about the supercooling? How do the devices prevent from the sodium acetate from supercooling? I’m afraid I don’t know. This paper discusses some practical considerations for thermal storage devices made using SAT, and it lists a number of additives that apparently rectify shortcomings in SAT behaviour. One of the additives is – curiously – wallpaper paste. I did try experiments with this but I didn’t observe any regular change in behaviour.

In any case, have fun with your sodium acetate experiments. It is available from here.


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