Getting there…

November 14, 2019

Life is a journey to a well-known destination. It’s the ‘getting there’ that is interesting.

The journey has been difficult these last few weeks. But I feel like I am ‘getting there

Work and non-work

At the start of 2019 I moved to a 3-day working week, and at first I managed to actually work around 3-days a week, and felt much better for it.

But as the year wore on, I have found it more difficult to limit my time at work. This has been particularity intense these last few weeks.

My lack of free time has been making me miserable. It has limited my ability to focus on things I want to do for personal, non-work reasons.

Any attention I pay to a personal project – such as writing this blog – feels like a luxurious indulgence. In contrast, work activities acquire a sense of all-pervading numinous importance.

But despite this difficulty – I feel like I am better off than last year – and making progress towards the mythical goal of work-life balance on the way to a meaningful retirement.

I am getting there!

Travelling 

Mainly as a result of working too much, I am still travelling too much by air. But on some recent trips to Europe I was able to travel in part by train, and it was surprisingly easy and enjoyable.

I am getting there! By train.

My House

The last of the triple-glazing has been installed in the house. Nine windows and a door (around £7200 since you asked) have been replaced.

Many people have knowingly askedWhat’s the payback time?

  • Using financial analysis the answer is many years.
  • Using moral and emotional analysis, the payback has been instantaneous.

It would be shameful to have a house which spilt raw sewage onto the street. I feel the same way about the 2.5 tonnes of carbon dioxide my house currently emits every winter.

This triple-glazing represents the first steps in bringing my home up to 21st Century Standards and it is such a relief to have begun this journey.

I will monitor the performance over the winter to see if it coincides with my expectations, and then proceed to take the next steps in the spring of 2020.

I am getting there! And emitting less carbon dioxide in the process

Talking… and listening

Physics in Action 3

Yesterday I spoke about the SI to more than 800 A level students at the Emmanuel Centre in London. I found the occasion deeply moving.

  • Firstly, the positivity and curiosity of this group of group of young people was palpable.
  • Secondly, their interest in the basics of metrology was heartwarming.
  • Thirdly, I heard Andrea Sella talk about ‘ice’.

Andrea’s talked linked the extraordinary physical properties of water ice to the properties of ice on Earth: the dwindling glaciers and the retreat of sea-ice.

He made the connection between our surprise that water ice was in any way unusual with the journalism of climate change denial perpetrated by ‘newspapers’ such as the Daily Mail.

This link between the academic and the political was shocking to hear in this educational context – but essential as we all begin our journey to a new world in which we acknowledge what we have done to Earth’s climate.

We have a long way to go. But hearing Andrea clearly and truthfully denounce the lies to which we are being exposed was personally inspiring.

We really really are getting there. 

The OTHER front in the fight against climate change

September 22, 2019

Well done to everyone who took to the streets last week to demand that our leaders face up to the challenges of climate change.

I too was fighting the good fight, but on another front, one which was frankly duller, less fun, and much more expensive.

I was arranging to have triple-glazing installed.

Triple Glazing

Ultralux Triple Glazing

All quiet on the insulation front

Imagine for a moment that the political battle to achieve immediate and drastic action on climate change has been won!

Imagine the glorious scene when the climate sceptics cower in humiliation and Prime Minister Corbyn/Johnson/Lucas/Swinson(*) declares that we will achieve zero carbon by 202X!

Hurray!

But then what? Just declaring a goal does not make it happen. The most important steps the government will take will not be about cool, high-tech projects such as electricity storage or solar cells or fuel cells or carbon capture or wind energy or electric transport.

They will be about thermal insulation of domestic houses

Overwhelmingly, the most important thing people will be compelled to do will be to insulate their houses.

The troopers on the front line of the battle against climate change won’t be radical vegans, activists or scientists. They will be builders and double-glazing triple-glazing salespeople.

The de Podesta plan

Just like the putative National Plan, our domestic plan is constrained by the amount of cash my wife and I have available.

Just like the putative National Plan, our plans need to be negotiated between interested parties and our actions prioritised against other goals.

We can’t do everything at once. So this year we will:

  • Replace the last of the single-glazed windows and all the first-generation (30 year old) double-glazing in the house with triple-glazed windows.
  • We have bought a chimney blocker for our open fireplace – kind of obvious I know.
  • We will replace an old gas fire (which requires a chimney) with an electric fire (which doesn’t).

I will then monitor the effect these steps have over the winter and consider the steps we can take for next winter.

Currently I estimate that to keep my house at 20 °C when the external temperature falls below 20 °C requires about 280 watts per °C that the temperature falls below 20 °C. My estimate is that about 25% of that is due to the windows and I hope to reduce that component by more than half.

Overall I am hoping for a 15% improvement in the thermal performance of the house to about 240 watts per °C. This looks like a pitifully small improvement to me, but at the moment, its all I can manage.

Unlike the Political Front in the battle against climate change, the Thermal Insulation Front is dull and undramatic. And every gain comes at a price and has be hard fought for. But it is a battle that has to fought.

Hasta La Victoria Siempre!

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* delete as appropriate

Why does heating my house require 280 watts per degree Celsius above ambient?

August 18, 2019

Previously I explained how I learned that for each degree Celsius the outside temperature falls below 20 °C, it takes 280 watts of heating to keep my house at 20 °C.

In order to provide this heating, I burn gas which last winter resulted in the emission of around 17 kg of carbon dioxide per day – around 2.5 tonnes in all.

I would really like to reduce this shameful figure, but I have only finite resources. In order to act I need to know where best to spend my money.

In this article I will explain how I came to understand the relative significance of the windows, roof and walls in this heat loss.

Windows

It is easier to estimate the heat loss from windows than it is from walls.

This is because walls are opaque and (without expert knowledge) it is not obvious what the wall is made of. Moreover, different walls in the house can have different construction and thickness. However, being transparent, one can see directly the type and construction of windows.

The heat flow through a window(or wall) is characterised by a U-value. This states the amount of heat which flows across 1 square metre of the window when there is one degree Celsius of temperature difference across the window.

The units are for U-values are watts per metre squared per degree Celsius (W/m2/°C) or watts per metre squared per kelvin  (W/m2/K). These two units are equal to each other.

Roughly speaking U-values for windows are [Link]:

  • Old single-glazed windows: 6 W/m2/°C
  • Old double-glazed windows: 4 W/m2/°C
  • New double-glazed windows: 1.5 W/m2/°C
  • The best triple-glazed windows: 1.0 W/m2/°C

I proceeded as follows:

  • I made a list of the 21 windows, skylights and glazed doors in in my house.
  • I measured their area – width × height in metres.
  • I multiplied their area by their U-value to get the transmission per degree Celsius through that window.
  • I then added them all up.
Slide5

For each window in the house I multiplied the area by the estimated U-value to get the heat transmitted per degree Celsius of temperature difference. I colour-coded the column to highlight which windows were the worst. Adding up all the windows came to 75.7 watts per degree Celsius. If I replaced all the windows with the best available I might be able to reduce this to 24.0 watts per degree Celsius.

The estimated total transmission through all the windows and doors came to about 76 watts per degree Celsius. I concluded that:

  • Firstly,  I could see which windows lost the most energy – they are colour-coded red, amber, and green in the figure above. There are no surprises – the largest area windows lose the most energy.
  • Secondly, I could see that if I replaced all the old windows with modern ones (U = 1.5 W/m2/°C), I might hope to reduce the window losses by roughly half their current value, to around 36 watts per degree Celsius. If I spent a lot – on triple-glazed windows and used insulating blinds, I might hope to achieve U = 1.0 W/m2/°C and reduce the losses to 24 watts per degree Celsius.
  • Thirdly, since the house as a whole is losing 280 watts per degree Celsius, I could see that windows and doors account for about a quarter of the energy lost from the house.
  • And finally, logically, the remaining 75% of the losses (280 – 76 = 204) must be going the through the roof, walls, and floors or lost in draughts.

Roof and Walls 

By analysing the thermal transmission of the windows and doors (transmission = 76 watts per degree Celsius), I concluded that roof and walls must be transmitting about 204 watts per degree Celsius.

  • Is this estimate reasonable?

To answer this question I embarked on yet another tedious and difficult exercise.

  • The tediousness arises because I need to add up all the areas of the roof and walls, subtract the areas of the windows and skylights, and then estimate the U-value,
  • The difficulty arises because I don’t know the materials from which the walls of the house are constructed!

Most of the walls date from the 1930’s (I think) and are probably solid brick. A 1970’s extension is probably not much better thermally, but I don’t know. However, the extension we built 10 years ago was built to building regulations at the time and I have a pretty good idea of the appropriate U-value.

So I made measurements of the wall areas. And then I assumed (link) that:

  • The old walls had a U-value of 2 W/m2/°C – a value appropriate for a double-skin solid brick wall.
  • The new walls had a U-value of 0.3 W/m2/°C – a value specified by current building regulations.
Slide6

For each wall or roof, I multiplied the area by the estimated U-value to get the heat transmitted per degree Celsius of temperature difference. I colour-coded the column to highlight which were the worst. Adding it up came to about 229 watts per degree Celsius. If I clad all the walls to achieve a U-value of 0.3 watts per metre squared per degree Celsius, I might be able to reduce this to 54 watts per degree Celsius.

With these assumptions I estimated the heat transmission through the roof and walls. As shown in the table above, I arrived at an estimate of 229 watts per degree Celsius. This should be compared with estimate of 204 watts per degree Celsius that I arrived by analysing:

  • My gas meter readings
  • The average weekly temperature
  • The estimated properties of the windows.

Given all the uncertainties, I take this as confirmation that within about 10% uncertainty, I can understand the thermal properties of my house.

Summary

Slide7

Currently my house loses 280 watts for each degree Celsius the external temperature falls below ambient. Of those 280 watts,

  • roughly 76 watts flow through the windows and doors
  • the remaining 204 watts flow through the walls, floors and roof.

With modern double-glazing I could reasonably hope to reduce the glazing losses from 76 watts to around 36 watts, or possibly even lower with triple-glazing and thermal blinds.

Cladding the entire house I could hope to reduce the losses from around 204 watts to around 50 watts.

  • What should I do?

In the next article I will discuss my strategy.

What it takes to heat my house: 280 watts per degree Celsius above ambient

August 16, 2019

Slide1

The climate emergency calls on us to “Think globally and act locally“. So moving on from distressing news about the Climate, I have been looking to reduce energy losses – and hence carbon dioxide emissions – from my home.

One of the problems with doing this is that one is often working ‘blind’ – one makes choices – often expensive choices – but afterwards it can be hard to know precisely what difference that choice has made.

So the first step is to find out the thermal performance of the house as it is now. This is as tedious as it sounds – but the result is really insightful and will help me make rational decisions about how to improve the house.

Using the result from the end of the article I found out that to keep my house comfortable in the winter, for each degree Celsius that the average temperature falls below 20 °C, I currently need to use around 280 W of heating. So when the temperature is 5 °C outside, I need to use 280 × (20 – 5) = 4200 watts of heating.

Is this a lot? Well that depends on the size of my house. By measuring the wall area and window area of the house, this figure allows me to work out the thermal performance of the walls and windows. And then I can estimate how much I could reasonably hope to improve the performance by using extra insulation or replacing windows. These details will be the topic of my next article.

In the rest of this article I describe how I made the estimate for my home which uses gas for heating, hot water, and cooking. My hope is it will help you make similar estimates for your own home.

Overall Thermal Performance

The first step to assessing the thermal performance of the house was to read the gas meter – weekly: I did say it was tedious. I began doing that last November.

One needs to do this in the winter and the summer. Gas consumption in winter is dominated by heating, and the summer reading reveals the background rate of consumption for the other uses.

My meter reads gas consumption in units of ‘hundreds of cubic feet’. This archaic unit can be converted to energy units – kilowatt-hours using the formula below.

Energy used in kilowatt-hours = Gas Consumption in 100’s of cubic feet × 31.4

So if you consume 3 gas units per day i.e. 300 cubic feet of gas, then that corresponds to 3 × 31.4 = 94.2 kilowatt hours of energy per day, and an average power of 94.2 / 24 = 3 925 watts.

The second step is to measure the average external temperature each week. This sounds hard but is surprisingly easy thanks to Weather Underground.

Look up their ‘Wundermap‘ for your location – you can search by UK postcode. They have data from thousands of weather stations available.

To get historical data I clicked on a nearby the weather station (it was actually the one in my garden [ITEDDING4] but any of the neighbouring ones would have done just as well.)  I then selected ‘weekly’ mode and noted down the average weekly temperature for each week in the period from November 2018 to the August 2019.

Slide3

Weather history for my weather station. Any nearby station would have done just as well. Select ‘Weekly Mode’ and then just look at the ‘Average temperature’. You can navigate to any week using the ‘Next’ and ‘Previous’ buttons, or by selecting a date from the drop down menus

Once I had the average weekly temperature, I then worked out the difference between the internal temperature in the house – around 20 °C and the external temperature.

I expected that the gas consumption to be correlated with the difference from 20 °C, but I was surprised by how close the correlation was.

Slide2

Averaging the winter data in the above graph I estimate that it takes approximately 280 watts to keep my house at 20 °C for each 1 °C that the temperature falls below 20 °C.

Discussion

I have ignored many complications in arriving at this estimate.

  • I ignored the variability in the energy content of gas
  • I ignored the fact that less than 100% of the energy of the gas is use in heating

But nonetheless, I think it fairly represents the thermal performance of my house with an uncertainty of around 10%.

In the next article I will show how I used this figure to estimate the thermal performance – the so-called ‘U-values’ – of the walls and windows.

Why this matters

As I end, please let me explain why this arcane and tedious stuff matters.

Assuming that the emissions of CO2 were around 0.2 kg of CO2 per kWh of thermal energy, my meter readings enable me to calculate the carbon dioxide emissions from heating my house last winter.

The graph below shows the cumulative CO2 emissions…

Slide4

Through the winter I emitted 17 kg of CO2 every day – amounting to around 2.5 tonnes of CO2 emissions in total.

2.5 tonnes????!!!!

This is around a factor of 10 more than the waste we dispose of or recycle. I am barely conscious that 2.5 tonnes of ANYTHING have passed through my house!

I am stunned and appalled by this figure.

Without stealing the thunder from the next article, I think I can see a way to reduce this by a factor of three at least – and maybe even six.

BAMS State of the Climate 2018

August 14, 2019

Reading the annual ‘State of the Climate’ report in the Bulletin of the American Meteorological Society (BAMS) has done nothing to help with my anxiety.

If you dare, you too can read it here:

Summary 

Imagine learning that your friend was in hospital. You race to the hospital and find your friend hooked up to every conceivable monitoring device.

If your friend is “the Climate”, then reading the BAMS State of the Climate report is like reading their autopsy before they have died.

You can foresee every tiny detail of their future suffering.

And yet the doctors don’t seem to be doing anything. Your friend is on the table, haemorrhaging, and the doctors are in an endless series of meetings!

The alarms on the monitors are beeping and flashing. But nobody comes to attend your friend.

You bang on the windows of the doctors’ meeting room and the doctors turn and glance at you, and then turn back to their conference.

You ask to see the hospital administrator. But they are too busy. An assistant assures you that they understand your distress.

You explain that this is not just A. N. Other Climate. This is the Climate, the one we all depend on for our food and air and water.

And the assistant agrees with you, sympathetically. But they patiently explain that the administrator is busy with IMPORTANT budget meetings right now.

And then you realise that your friend has been on the table for years…

…and that the doctors meeting has been going on all this time.

With each passing year the doctors become more and more certain of the exact manner in which your friend will die. But no treatment has begun.

You begin to feel angry. And depressed. And frustrated. And you consider acting irrationally.

You begin to consider that acting – rationally or irrationally – is the only chance to save the friend you love.

Being alive at the peak of the carbon age

July 22, 2019

View from aeroplane

Friends, we collectively wish the best for our families, friends and the wider communities to which we belong. But how do we avoid having conversations like this with our grandchildren?

Granny, what was it like to live at the peak of the carbon age?”

Our teacher said that back in the 2020’s you could still fly around the world for the cost of a few weeks wages and that planes then emitted hundreds of TONNES of carbon dioxide on every flight?

“And she said that those old aeroplanes left clouds that changed the look of the sky!”

“Is that true Granny? Did the planes really do that?”

“Yes, darling, that’s what it was like back then.”

But why Granny? In History we learned that everyone knew for decades that carbon dioxide emissions would melt the Arctic ice. And now that the Greenland Ice Sheet has begun its strong melt, we have rising sea levels and strange weather and its harder to grow food. “

“Didn’t you know what you were doing?”

“Darling, yes, we knew, but, we sort of didn’t really want to think about it.”

“For example, Michael, your grandad, wanted your parents to see what the Mediterranean was like, so we flew to Greece one year. It was so good to swim in the warm clear water and we all had a great time. We just didn’t discuss the extreme heat or the carbon.”

“And Michael wanted to show your parents California where his friend from school lived. We had a couple of great holidays there. It was so, so beautiful. We even saw the Sequoias before the Great Fire.”

“And more recently, I ached to see you and your parents again. After your parents left the UK in their twenties, the thought of not seeing them again felt like a death sentence.”

“And the tele-screens weren’t like the tele-presence systems we have now, so we both needed to travel for work.” 

“Everyone knew we were storing up problems for the future, but it wasn’t as socially unacceptable as it is now. Now everyone boasts about how far under-quota they live. But back then some people took exotic holidays several times a year. Even Climate Scientists flew on aeroplanes – every one did it.

“A few people went on and on and on and on about it, but while flying was easy and cheap we just tried not to talk about it.”

“And there didn’t seem to be an alternative.” 

But there were alternatives Granny! If you had just begun to really do something twenty years earlier, things would be so different for us now.” 

(C) Tina Meyer https://www.pinterest.co.uk/tmeyersd/

Granny, what was it like to live at the peak of the carbon age?”

 

 

 

 

The Moon as a symbol of hope

July 19, 2019

Eclipse July 2019

I sat out by the Diana Fountain in Bushy Park on Tuesday night and took a picture of the eclipsed Moon.

As I sat in the peaceful darkness, I thought about the fact that when I was nine-years old, human beings had sent a rocket ship to the moon, and men had walked about and collected some rocks.

As technology has advanced since the 1960s, the engineering in the Apollo program has not been eclipsed. Indeed, it seems ever more remarkable.

And amongst the moths and the bats, I reflected that “…if human beings can do that, then we can do anything that can be done…”. 

That qualification “…that can be done…” is there because although the aim of the Apollo programme was built on a whimsical folly, the engineers who made it happen could only use practical steps to make it real.

Some of the steps they took seem astonishing, but there was – obviously – nothing ‘impossible’. No steps relied on wishful thinking.

The excellent bookHow Apollo Flew to the Moon” , (my review is here) highlighted some of most astonishing facts:

  • The total mechanical output power of five first stage rockets was 60 GW. This is equivalent to peak electrical supply of the entire United Kingdom.
  • On its return from the moon, its speed just before entry into the Earth’s atmosphere was more than 11 kilometres per second.
  • Since Apollo 17 returned in 1972. no human being has been more than 700 kilometres from Earth’s surface.

And sitting in the dark I reflected that if we could achieve all these things then, surely we can – and eventually will – get our act together on Climate Change.

It may seem impossible now, but even the most politically deaf regimes will eventually dance to the theme of climate change – they have no choice.

And if the US were to devote to this problem even a small fraction of the energy and enterprise that it devoted to Apollo, they could yet inspire us all again, and leave a legacy to be proud of for all our children.

Travelling too much

July 5, 2019

Its been a while since I wrote here and the main reason for this silence is that I have been travelling too much.

And by ‘travelling’ I specifically mean flying. So far this year I travelled far enough to fly clear around the Earth – more than 40,000 km. And in every sense, it is just too much.

There is always a good reason to travel – work and ‘business’ always provide sound reasons for travel. But the undeniable fact of the matter is that flying is bad for the environment.

So while I greatly enjoyed a secondment in New Zealand the trip caused the emission of 7.6 tonnes of carbon dioxide – an amount which overshadows the steps I take to minimise emissions at home.

And the carbon dioxide emissions are not even the worst part. I was reminded by a recent Physics World news item that:

… contrail cirrus clouds are the single largest source of the aviation industry’s contribution to climate change, far outpacing the impact of aircraft carbon dioxide emissions. 

It is hard to just say ‘No’

I have asked my colleagues in many fields how they feel about flying. Everyone I have asked thinks it is a really important issue.

Some have, bravely in my opinion, shunned air travel, refusing offers to travel because of the emissions they would cause.

While not underestimating how hard that choice is, it is easier for those who live in large cultural centres such as London. London offers a great many local opportunities for work and pastimes, and also has ground-based National and International travel networks, that are not available to those who, for example, live in New Zealand.

And the freedom to not travel is not open to everyone. Some are obliged to travel internationally for work.

For colleagues working in the field of climate change, many of whom forswear personal air travel, international meetings are an essential part of seeking international solutions to this international problem.

But even these colleagues who don’t fly for personal reasons normally have funerals to attend. And perhaps when their children grow they may ache to see their grandchildren who may be living far away.

The bridge to the future

If we imagine a future more sustainable world, then flying around the world must surely become less common.

In market economies the only ways to achieve this are to either

  • (a) raise the price of air travel, or
  • (b) ration the amount of air travel or
  • (c) some combination of (a) and (b).

None of these look like options that people will vote for without a great deal more understanding of the problem at hand.

To misquote LP Hartley,

The future is a foreign country, they do things differently there.

But how do we get there?

World Metrology Day 2019

May 19, 2019

This slideshow requires JavaScript.

Monday 20 May – World Metrology Day 2019 – is a day towards which I have been working for the last 14 years.

Back in 2005, my NPL colleagues Richard Rusby,  Jonathan Williams and I compiled a report on possible methods for measuring the Boltzmann constant. The aim of the measurement would be to obtain an estimate of the Boltzmann constant with sufficiently small uncertainty that the International Bureau of Weights and Measures (BIPM) would feel able to redefine what we mean by ‘one kelvin’ and ‘one degree Celsius’ in terms of this new estimate.

To cut a very very long story short, we succeeded. And tomorrow, that project comes to fruition.

Of course it wasn’t just me. Or even me and my immediate colleagues in the thermal team at NPL. We were helped by colleagues from across the laboratory, and from other institutions. Notably:

  • Cranfield University who manufactured the key component in the experiment,
  • The Korean National Laboratory KRISS and the Scottish Universities Environmental Research Council who helped with isotopic analysis of argon gas.
  • Colleagues helped us from:
    • LNE-CNAM in France,
    • INRIM in Italy,
    • NIST in the USA,
    • PTB in Germany,
    • CEM in Spain.

And I have probably missed an important institution or partner from this list because – frankly – it has been a long haul!

But even this list doesn’t include all the other teams involved in the wider kelvin re-definition project.

Several other institutions also sought to independently measure the Boltzmann constant using a range of different techniques and the value chosen by the International Bureau of Weights and Measures (BIPM) was the weighted average of estimates from this international effort.

In all, hundreds of scientists, engineers and technical staff around the world have supported this effort and I feel humbled to have had the opportunity to take part in a project of this scale.

And it is not just the kelvin, today three other units will also be be redefined – the mole, the ampere and the kilogram.

In this troubled world, it is a real comfort to me to feel the friendships built and professional relationships created during these last 14 years.

I think it shows that the International System of Units is a living international institution which really works; which brings people together from around the globe to make measurements better. The SI is an institution of which the whole world can feel proud.

Happy World Metrology Day 🙂

Should I still be using gas?

May 6, 2019

TL/DR The carbon emissions associated with electrical generation in the UK have fallen so much it is has become greener – but not necessarily cheaper – to cook and heat using electricity.

Electricity Generation

The carbon intensity of a source of electricity is a measure of how much carbon dioxide (measured in kg) was emitted to make one unit of electrical energy: an electrical kilowatt hour (kWe).

The chart below shows the carbon intensity of electricity generated by various techniques. The average carbon intensity depends on generating mix – and how that varies with time.

Carbon Intensity of different generating sources

When I began talking about Climate Change back in 2004, Coal, Gas and Nuclear were the main generating sources for UK electricity. And the average carbon intensity – if I remember correctly – was around 0.50 kg CO2 per kWe.

The generating mix in 2019 is radically different. The carbon intensity varies daily and seasonally between about 0.1 kg CO2 per kWe (at times of low demand and high renewable generation) and 0.4 kg CO2 per kW(at times of high demand and low renewable generation). The average value is less than 0.3 kg CO2 per kWand falling.

The chart below shows how the carbon intensity of electricity varied through the month of December 2018. The average value was 0.243 kg CO2 per kW.and the maximum and minimum values were 0.390 kg CO2 per kWand 0.094 kg CO2 per kWrespectively.

Carbon Intensity in December 2018

In my home

I can choose to heat by using electricity or gas.

  • If I heat using electricity then I can convert electrical energy into heat with 100% efficiency, so for every kW of electrical power I use, I generate 1 kW of thermal power (kWth). And hence release roughly 0.3 kg of carbon dioxide.
  • If I heat using gas then I can convert chemical energy in the gas into heat with high efficiency – but not generally 100%. So (looking at the chart at the start of the article) for every 1 kWth, I emit at least 0.47 kg of carbon dioxide.

Now the price per kWh (one kilowatt hour) that I am charged by EDF, the French government-backed company that supplies my electricity and gas is:

  • 26.6 pence for 1 kWh of electrical/thermal energy during the day.
    • Generally higher carbon intensity ~ 0.4 kg CO2 per kWe.
  • 5.0 pence for 1 kWh of electrical/thermal energy during the night.
    • Generally lower carbon intensity ~ 0.15 kg CO2 per kWe
  • 4.2 pence for 1 kWh of thermal energy (via gas) at any time.
    • Always at least ~ 0.46 kg CO2 per kW

So the reduction in the carbon intensity of the UK’s generating mix means that switching to electricity now makes ‘green sense’. i.e. If I generate 1 kW heat in my house using electricity then less carbon dioxide is emitted than if I just burned the gas directly

But in order to make financial sense I would need to make sure that I didn’t use any ‘daytime’ electricity.

Mmmm. Well at least I have a choice!

Resources

 


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