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_aavaa_ 1 days ago [-]
The books is good(ish) for it's time, but some of its analysis and forecasts are fundamentally flawed since it falls for the primary energy fallacy by comparing the chemical potential energy (in J) directly to electrical energy (also in J). The two are fundamentally different things and called be compared 1:1. E.g. To heat up your home with natural gas you need ~1J of chemical energy to get 1J of heat into the home, but with a electric heat pump you only need 1/6 J to get 1J of heat.
It is also a product of its time in terms of wind/solar vs nuclear. His forecasts of the impact of solar and wind is based on prices and performance from 2008. Prices have come down an order of magnitude since then, and performance and lifespan have increased drastically.
azornathogron 1 days ago [-]
Heat pumps, and their efficiency (getting more than X Joules of heating for X Joules of electricity) are discussed in chapter 21 Smarter Heating, see for example the diagram and discussion on page 150: https://www.withouthotair.com/c21/page_150.shtml
I imagine the economics (and perhaps technical improvements) of some things may have changed more than the book could forecast. But heat pumps were definitely understood by the author.
_aavaa_ 1 days ago [-]
I’m not saying he was unaware of heat pumps, I’m saying he’s comparing apples to oranges simply because they use the same units.
Look at “3 - Cars” on page 29. He says the typical car uses 40 kWh/day. 40 kWh of what? Chemical energy in the gasoline.
The go to page 33 where he looks at how much energy onshore wind could produce per days in the UK. His number is 20 kWh/d. 20 kWh of what? electricity
He then compares those two numbers directly and uses that comparison as the basis of his arguments: “Britain’s onshore wind energy resource may be “huge,” but it’s evi-
dently not as huge as our huge consumption.”
This is simply incorrect. A combustion engine converts less than half of the chemical energy in the gasoline into mechanical work that can move the car. The electric model converts >90% of it. So we don’t have to replace 40 kWh/day, we have to replace less than half of that since the electric process is more efficient.
This same issues, the primary energy fallacy, underpins large parts of the book.
sideshowb 1 days ago [-]
He does correct for the efficiency of both electric cars, and heat pumps in later chapters. His line of argument is "here is the current energy supply and demand - now here are ways we can increase one and reduce the other".
The wind analysis was reasonable for the time, iirc the main error there was that he failed to foresee offshore wind dropping in price so much.
_aavaa_ 1 days ago [-]
I disagree. The framing of focusing on primary energy and then sprinkling efficiency afterwards has two issues: 1) it pulls focus away from the thing we want (the end result) and 2) it makes it much easier to misunderstand (or to misrepresent) because the efficiency differences can be omitted.
And graphs like the one comparing wind turbine output to petrol car consumption are inherently deceiving. Two values are put side by side with the same units and then talk about directly as if they are comparable. But they simply are not. A kWh of chemical energy and a kWh of electricity have as much in common as a US dollar and a Jamaican dollar.
ralfd 1 days ago [-]
I agree with you. I read it cover to cover at the time and felt like a smart ass ("AksHuALLy renewables can't work alone!"), then wondered a few years ago how his calculations turned out in the real world.
1. Sad that he died from cancer
2. Noticed he compared primary energy and felt stupid for missing that
kragen 1 days ago [-]
I never got a blanket claim of "actually renewables can't work alone" from the book. It seemed more like "actually you need to understand things quantitatively or you are doomed to talk nonsense".
MacKay's "renewables can't work alone" claim always seemed carefully scoped to the economics of 02008 (when solar modules cost 33× as much as they do now) and also his own densely populated, rather polar country. Renewables were already working nearly alone, at scale, in equatorial countries and more sparsely populated countries; I live in Argentina, whose grid was mostly hydroelectric at the time, and next door to Brazil, where a large fraction of the automotive fleet ran on sugar-cane-derived ethanol, which is a viable renewable energy source (unlike, apparently, corn ethanol).
PaulDavisThe1st 1 days ago [-]
There is nowhere that renewables are remotely close to working "nearly alone" if you are talking about total energy needs (which MacKay is/was).
There's some incredible progress for electricity generation, but there's still huge amounts of energy being used in ways that are not currently electrified and not close to electrifiable in the short term.
We should celebrate the forward progress, but also not be blind to what is not yet feasible (while also hoping that it may soon be so).
kragen 22 hours ago [-]
You're right, and I appreciate the correction — even Norway mostly runs its transport on fossil fuels, not electricity, and trucking and ships aren't going to be electrifiable in the short term. Here in Argentina, when we ran our grid mostly on hydroelectric, the cars were still running mostly on gasoline and compressed natural gas.
(Yes, I know that makes me sound like an LLM.)
mbgerring 23 hours ago [-]
Right, as long as you specify “without energy storage”, renewables “can’t work alone,” even though energy storage is included in most common sense definitions of “renewables”
Thankfully, energy storage is being deployed worldwide, so this is a moot point, and renewables can and will replace fossil fuel electricity generation.
kragen 21 hours ago [-]
We're going to need more than grid-scale batteries to electrify trucks, ships, and long-distance airplanes. PaulDavisThe1st is right about that! Solar-powered fuel production from CO₂ is one possibility.
DangitBobby 20 hours ago [-]
Not for trucks but probably ships and planes.
jarvist 23 hours ago [-]
No, the wind analysis was not reasonable for the time - he used data from a previous generation of turbines (and in turn, the next generation of turbines were certain to be 40% bigger & etc.), from a wind farm that had quite flukey winds.
I saw him present 18 years ago, and asked him why: he said that he didn't want to rely on any predictions or models, but only discuss real data. Which is sort of defendable as a position, but ignored the fact that renewable energy was progressing so incredibly fast, and that these engineering predictions were not speculative but very much concrete.
Similarly the silicon solar panel industry in 2008 had a roadmap to get to £1/Wp over the next few years (which they did, and which led to the ~2012 explosion in solar installations), by mass producing the 'expensive' ~20% efficient (mono-crystalline silicon) technology.
Mackay uses a 10% figure throughout.
So overall this was a bit like making predictions in the year 2000 assuming everyone will be stuck on 56k dial-up forever, because most people are on 56k dial-up.
These biases are present in all of the discussion of renewable technology, yet nuclear gets a free-ride / magical thinking in terms of uranium extraction, waste disposal and cleanup.
And then there is the persistent obsession with land use in the book.
This led me to the conclusion (which I still hold) that this was an example of the tail wagging the dog: David MacKay wanted the 'obvious' physicists answer of nuclear power to be the natural conclusion, and by construction made it so in his book. Just because you are a Bayesian does not mean that you are unbiased!
David MacKay was an amazing scientist, but I do not think this book is accurate (even for its time), or that useful in public understanding of what we now call 'Net Zero'. It certainly popularised the idea of actually thinking through individual energy budgets, which can only be a good thing, but it was a massive missed opportunity to treat heat (chemical) energy (maximum entropy) and electrical (which can directly do work) as equivalent, just because they have the same unit.
Later on, as the 'Climate Tsar' he made a web app where you could play with the future balance of generation with a simulated model of the UK, and set your own costs for the different technologies, which I thought was much more useful. You could choose your own energy mix, and understand some of the tradeoffs.
And yes, very sad that he died so young. In the context of this book it would have been interesting to see how he dealt with the increasing mismatch of reality and his predictions as time passed.
ZeroGravitas 12 hours ago [-]
Just before he died in 2016 he gave an interview "revealing" his true thoughts on the matter but I think like you say it came through obviously enough in his work:
> There is this appalling delusion that people have that we can take this thing that is currently producing 1% of our electricity and we can just scale it up and if there is a slight issue of it not adding up, then we can just do energy efficiency,” he said. “Humanity really does needs to pay attention to arithmetic and the laws of physics – we need a plan that adds up.”
> Prof MacKay had previously avoided being drawn into the political debate about energy, but told Lynas: “I have always tried to avoid advocating particular solutions but maybe because time is getting thinner I should call a spade a spade.”
> The key for the UK, he said, was a zero-carbon solution that works in the winter, when energy demand is highest but sunshine is lowest and winds can drop for days at a time. “The sensible thing to do for a country like the UK, I think, is to focus on CCS, which the world needs anyway, and nuclear,” said Prof MacKay.
> The decision on a new nuclear power plant at Hinkley Point, which the government hopes will be the first of a new generation of plants, has been delayed until September.
> “Then if you ask what is the optimal amount of wind and solar to add in then the answer is going to be almost zero,” he said. “I love wind turbines – they are the cathedrals of the modern age – but they are a waste of money if you have a low carbon solution that gets you through the winter … because when the wind blows you are going to have to either turn them down or something else down that you have already paid for like nuclear or CCS.”
Maybe he would have changed his mind as prices and delivery timelines diverged but many of the people who were most enthusiastic about his work because it reflected their nuclear preference didn't, so who knows.
Though maybe his kind of person that liked nuclear and heat pumps and EVs all just changed their mind based on new evidence and we are left with the people who mysteriously like nuclear but don't want to use the output for heat and transport.
feoren 1 days ago [-]
> He does correct for the efficiency of both electric cars, and heat pumps in later chapters.
There's something really important to understand when evaluating non-fiction books: nobody reads the later chapters, and the authors generally know this. They can present tremendously one-sided information in the first few chapters, giving the spin that they want, and then in later chapters give a more balanced approach to shield themselves from criticism. Almost everyone who reads the book will read only the spin, but any criticism levied against the author will be met with "but I specifically say, in the later chapters ...". It's a slimy technique that you start to see everywhere once you're aware of it.
sideshowb 1 days ago [-]
Although in this case, iirc the argument that using renewables in isolation would be challenging came in an even later chapter
PaulDavisThe1st 1 days ago [-]
> There's something really important to understand when evaluating non-fiction books: nobody reads the later chapters
Asserted without evidence, and I very much doubt that it's true. I suspect it varies dramatically by subject matter, intended audience, book length, data density, and more. I have no evidence for any of that. Do you?
cycomanic 22 hours ago [-]
There was some statistics on capital in the 21st century by Picketty (maybe from Kindle readers?) that most owners of the books only read the first 10 pages or so. Am on mobile but should be easy to find.
Not necessarily saying this generalises to all non fiction books though
TeMPOraL 1 days ago [-]
I remeber the book differently - I remember it being primarily about getting exactly this right. Lot of space spent discussing efficiency and losses and comparing apples to apples.
(Admittedly, I read it many years ago, my memory may be off, though I strongly doubt it.)
hunterpayne 13 hours ago [-]
He did get it exactly right. 1500 pages of detailed analysis and you have people here making up nonsense to claim it isn't accurate. The posts on this article make me lose my faith in humanity...or at least HN...total clown show here tonight.
js8 1 days ago [-]
I think in 2008, it wasn't clear whether cars are going to be replaced by electric and what the final efficiency will be. It could also have been more because you would need to convert electricity to fuel first.
So I think as a conservative estimate, it kinda works.
ZeroGravitas 1 days ago [-]
Cost would depend on battery manufacturing but the original founders of Tesla created spreadsheets of well-to-wheel efficiency based on available data in 2002 and knew that electric came out as an obvious winner and so commited to starting the company based on that.
kragen 1 days ago [-]
A lot of companies started in 02002 based on spreadsheets of available data went bankrupt due to the available data being wrong, or due to things not included in the available data at all. A quick check of Wikipedia turns up:
And those are cherry-picked from companies that got big enough to be "notable" by Wikipedia's guidelines. Far more companies never reach that level.
The conservative estimate is that any time someone tries to deploy a new technology, it will fail. Most innovations (new technologies or companies) do.
Take a look at the HN front page from 10 years ago: https://news.ycombinator.com/front?day=2016-09-28 There we see Uber's self-driving truck initiative Otto (an acquisition), deep learning startup Skymind, a new static Linux distro called Stali, and a bunch of things that weren't innovations. All three of those things failed; Stali hasn't been updated since 02019. LuaTeX, Coinbase, Linux, Wikipedia, and dyeing with indigo are other innovations that feature on that page, but they were already very old.
ZeroGravitas 1 days ago [-]
It doesn't change the physics though. I think the author under discussion actually gets this right in some chapters with regard to the superior efficiency of EVs, though not sure if that was a later revision or not.
kragen 1 days ago [-]
That's true! What was holding up EVs 18 years ago, or for that matter 18000 years ago, was not physics, but the humans' ability to efficiently make things such as batteries and high-efficiency electric motors.
> In the last chapter, we learned that electrification could shrink transport’s
energy consumption to one fifth of its current levels; and that public transport and cycling can be about 40 times more energy-efficient than car-driving. How about heating? What sort of energy-savings can technology
or lifestyle-change offer?
and it goes on to talk about heat pumps, as today. So I think that even versions from 02008 got this right, though evidently that was at least the 13th numbered draft.
thelastgallon 1 days ago [-]
> replace less than half of that since the electric process is more efficient.
This is right. This shows 63% wasted (as of 2024).
I remember this was 67% just a few years back. May have gone down because of increase in solar.
sustainabilitybynumbers (Hannah Ritchie) had an article talking about this, that we need only 25%-ish in renewables. I am unable to find that article.
(edit) found the article
https://hannahritchie.substack.com/p/electrification-energy-...:
Global final energy demand today2 compared to a ‘post-transition’ energy system where suitable sectors are electrified, and the rest is fuelled by hydrogen. Electricity demand does increase – from 110 to 189 EJ, but total energy demand drops from 416 to 247 exajoules (EJ).
kragen 1 days ago [-]
Thermal energy and electrical energy really are the same thing, not two different quantities that happen to be measured in the same units, like grams of lead and grams of gold, or your example of US dollars and Jamaican dollars. When you convert less than half of the chemical energy in the gasoline into mechanical work to move the car, the other 50+% of the energy is converted into heat. Carnot gives us a reversible conversion factor between them, but it depends on the combustion temperature rather than being some kind of constant, as in your Jamaican-dollar example.
Technically you can interconvert grams of lead and grams of gold one to one, too, but interconverting electrical and thermal energy is so easy that it happens all the time unintentionally.
> In the last chapter, we learned that electrification could shrink transport’s
energy consumption to one fifth of its current levels; and that public trans-
port and cycling can be about 40 times more energy-efficient than car-
driving. How about heating? What sort of energy-savings can technology
or lifestyle-change offer?
And then he goes into not just household heat pumps, and their achievable coefficients of performance, but also municipal combined heat and power, which take that ≈50% of the chemical energy "lost" from thermal power plants as waste heat and pumps it into your house.
So, far from being ignorant of the issue as you seem to be implying, he presents a more complete picture of the issues than you are presenting.
Specifically for household climate control, I suspect that both heat pumps and CHP are much less relevant now that we have cheap solar. You can think of a heat pump as a way to reduce the amount of solar-panel area that you need to heat your house. The trouble is that solar panels cost €0.13 per peak watt, while heat pumps cost closer to €1 per peak watt, so it may be cheaper to "waste" energy on heating your house resistively with a nichrome wire than to use a carefully engineered heat pump.
rcxdude 1 days ago [-]
For the purposes of energy use, they are not. Heat is fundamentally worth less than the equivilent amount of electrical energy, due to these efficiency losses (which are not just a technology problem). It's misleading to compare them at any point in your analysis unless to highlight the problem with the comparison.
kragen 22 hours ago [-]
Usually it's fundamentally worth less, but not a specific amount less, the way Jamaican dollars and lead are. And, if you're using resistive heating, they're worth exactly the same amount.
rcxdude 22 hours ago [-]
You can convert electricty to heat at 1:1 in the absolute worst case. The opposite is not possible even in the absolute best case, and in practice you are looking at about a 60% exchange rate for 'high-grade' heat.
kragen 21 hours ago [-]
That "absolute worst case" happens in my house most of the winter, and it's common throughout the rich world. The only place it isn't common is where people don't have electricity yet. Even in Brazil, where nobody needs a space heater, electric water heaters are common.
When that absolute worst case is happening in the house's living space, we can and do "convert" heat to electrical energy savings 1:1, because every joule "wasted" by cooking food with gas, or heating the house with a corn stove, or warming up the floor with sunlight for passive solar gain, is another joule earlier that the space heater's thermostat will turn it off.
rcxdude 21 hours ago [-]
Sure, you're using the themodynamically worst heating technology possible (I don't think I have ever lived in a house that used resistive electric heating). That still doesn't make it a useful comparison overall where people often pick better options, nor does it make it so that you're actually converting the other way when you use better options.
kragen 21 hours ago [-]
As I explained 5 comments up this thread, people are going to stop picking those "better" options because they're no longer economical. I think you just didn't notice that part of my argument, because you never responded to it.
Also, I don't think it's accurate to describe electrical resistance heating as "the thermodynamically worst heating technology possible". Electrical resistance heating is generally close to 100% efficient. It's actually thermodynamically possible to make heaters that are less than 100% efficient; MacKay explains, for example, that he heats his house with a 90%-efficient condensing boiler, and it's common for fireplaces to be around 20% efficient, because most of the heat goes up the chimney instead of heating your house.
Fireplaces are actually thermodynamically possible machines. I understand that you've never seen one, but I assure you that they do exist.
I've actually lived in houses where the fireplace had negative efficiency at times, sucking more heat out of the house (in the form of warm air) than they added back in the form of radiation.
rcxdude 21 hours ago [-]
That only makes sense in a situation where renewables have already more than taken over, which kind of makes the point moot. I'll concede your point that traditional fireplaces are even worse than resistive heating, though not that a gas condensing boiler is because you're not getting 90% of the energy in the gas out as electricity.
namibj 4 hours ago [-]
I'm pretty sure the barrier to the lead-gold mass parity is that due to nuclear stuff they're gonna not trade equal proton/neutron count and while of you flip the ratio you are merely dealing with an energy deficit/excess incurred as you're rearranging the protons and neutrons to transmute between gold and lead which by e=mc² is equivalent to mass... You're gonna run head first into the problem that we with our current proven understanding of atomic nucleus quantum physics, expect the energy excess to need to be turned into an equal split of matter *and antimatter*, which will foul your plans.
We're suspecting there to be some symmetry breakage to explain why we don't really see any globs of antimatter with our telescopes (at least none that show any evidence of being antimatter), but so far no (real) luck.
As for the "0.13€ vs. 1€": you're not gonna get much solar yield in peak winter at least in Central Europe, especially it's gonna be that your PV is going to charge <100hour electricity storage when the sun shows up on those winter days and the heat pump (at least the part that spends a little electricity to lift a lot of heat energy from outside temps to indoor temps) runs approximately continuously.
You might have some kind of e.g. water/water heat pump with salted (not table salt though) water deliberately thawing during daytime (by turning on the circulation between it and outside air) to freeze at much warmer than night air temperatures to buffer those "only mildly freezing" temperatures to improve the efficiency (and at that point, likely also the thermal output power) of the heat pump.
The radiators inside and potential fans for them would also go up in flow to make up for the increased losses through the walls/window-glass.
A big reason why at least in e.g. Germany heat pumps are not at all irrelevant vs. electric resistance "space heaters" is that they're also very efficient at handling spring/autumn (lower thermal delta to lift against; referencing to a resistance heater for scale/reference purposes but clearly not expecting that to be a benchmark) while easily offering summer cooling (with relatively minor incremental complexity).
I don't really know how inherently expensive it is to keep around at least for parts of each city, but existing natural gas central heating boilers are very useful to not just trash before they're broken just because one uogrades to a heat pump, specifically because they are already there (sunk cost/little scrap value) and have basically zero issue delivering extremely spiky power during unannounced winter days (well, takes maybe a day of notice to actually get crew in to the storage&distribution facilities, but weather forecasts easily cope).
Sure, it's not _efficient,_ but we could just divert some synthetic methane during summer to refill the caverns: we kinda want that (at least for hydrogen but methane works too at least for storage) anyways for chemical synthesis factories if we're not just gonna feed them crude oil/natural gas, so other than that chemical factories probably/largely prefer direct hydrogen, continuing to use our existing seasonal storage even if it's not getting refilled from NordStream2 but from local summer-only electrolysis plants and with more hydrogen than methane where the geology allows, seems to me just frugal dealings with nature (reduce, Reuse, recycle).
kragen 41 minutes ago [-]
I think you can, in theory, break apart stable lead nuclei by spallation, transmuting some of them into somewhat lighter elements (first-row platinum-group elements, tungsten, that kind of thing), which you can fairly easily separate by chemical means, then bombard with neutrons and alpha particles until some of them become gold, go through another chemical separation step, and repeat. You need energy input for all of this, but I don't think you need to deal with significant quantities of antimatter, just the occasional positron emission.
I admit I don't know much about nuclear reactions, so please let me know if I'm talking nonsense here.
I agree that Central European capacity factors for solar are pretty bad, and that heat pumps are still economical in more polar countries, and will remain so for a few more years.
I'll answer the rest of your extremely interesting comment later, as I'm being drawn away at the moment, but I want you to know that I appreciate it very much.
pfdietz 1 days ago [-]
> A combustion engine converts less than half of the chemical energy in the gasoline into mechanical work that can move the car.
Much less. Your typical gasoline IC vehicle converts maybe 1/4 of the chemical energy into work.
bryanlarsen 1 days ago [-]
The average Brit drives under 20 miles per day. A Tesla will do 4 miles per kWh, meaning it requires 5 kWh per day. That's 1/8 of 40 kWh. I'm not sure where the discrepancy is.
leoedin 8 hours ago [-]
The book says 50km/30 miles per day in a petrol car is 40kWh. For a Tesla that would be 7.5kWh of electricity. It also assumes 12 km/litre - which in UK terms is 33 mpg. A Tesla has regenerative braking, so it would be better to compare the fuel efficiency to an aerodynamic hybrid. A Toyota Prius gets 61 mpg (UK) - which would mean 21.6 kWh per day.
So really the comparison is 7.5kWh of electricity compared to 21.6kWh of petrol. The Prius gets 34% of the miles compared to the Tesla for a given energy input. In the olden days when renewables didn't do much, the chemical energy input for 7.5kW of electricity was probably 15 kWh. So the electric car is a little bit more efficient (taking advantage of the efficiency of large power plants).
These days, thanks to renewables the fossil fuel input into the electricity is lower.
pfdietz 7 hours ago [-]
> These days, thanks to renewables the fossil fuel input into the electricity is lower.
Also, natural gas to electricity in CC plants is ~60% efficient.
leoedin 4 hours ago [-]
Yeah, I assumed 50% to account for various losses and other less efficient generators. I don't know what the actual number is - probably in the 40-50% range.
Interestingly thanks to renewables the "carbon intensity" of a kWh of electricity is already better than a kWh of fossil fuels in some countries. A kWh of petrol releases about 250g of CO2, and quite a few countries (predominantly developed ones) have lower carbon intensities per kWh of electricity. Considering round trip efficiencies the carbon released by an electric car in those countries is easily 1/3 to 1/4 of the carbon released by a petrol car.
In the USA it's not as good, but electric cars are still releasing about half the carbon.
pfdietz 3 hours ago [-]
The big question in my mind for efficiency figures is whether it's with respect to the Lower Heating Value (LHV) or Higher Heating Value (HHV) of the fuel. The latter includes the latent energy from condensing the water of combustion.
pfdietz 1 days ago [-]
Regenerative braking? Or the IC engine not being operated at its most efficient power point.
ZeroGravitas 1 days ago [-]
Yes, I disagree with some of his takes but he was spot on regarding heat pumps:
> Let me spell this out. Heat pumps are superior in efficiency to condens-
ing boilers, even if the heat pumps are powered by electricity from a
power station burning natural gas. If you want to heat lots of buildings
using natural gas, you could install condensing boilers, which are “90% ef-
ficient,” or you could send the same gas to a new gas power station making
electricity and install electricity-powered heat pumps in all the buildings;
the second solution’s efficiency would be somewhere between 140% and
185%. It’s not necessary to dig big holes in the garden and install underfloor
heating to get the benefits of heat pumps; the best air-source heat
pumps (which require just a small external box, like an air-conditioner’s)
can deliver hot water to normal radiators with a coefficient of performance
above 3.
namibj 3 hours ago [-]
I want to remind that natural gas fired heat pumps operating with central European winter temperatures on the cold side and toasty warm indoors living room "by the fire place/any clothes are too warm just sitting not even exercising at all" are well established technology.
They're just usually deployed for frozen warehouses, factories that actively freeze large amounts of (usually food), and AFAIK the occasional ice(hockey) rink.
Shitty types that don't even bother with any decent controls/pumps (those 90% boilers use a water loop circulation pump and a combustion air blower together with a bunch of sensors and valves) run propane-fired in many camper vans to do the fridge.
But at the scale of an apartment building fit for 50+ residents, a natural gas fired central heat pump can be _quite_ efficient and economical.
Thermodynamically they're a heat engine with high combustion/flame temperature that uses the warm side as the heat sink, mated to a heat pump that consumes the produced "mechanical/electrical grade" power to pump heat from the cold side to _also_ the warm side.
You save the turbine! Also the electrics but they're probably not even that expensive relative to the rest of the 200MW-class combined cycle natural gas power plant.
bryanlarsen 1 days ago [-]
Which means that not including the conversion in the primary comparison is particularly egregious.
azornathogron 1 days ago [-]
Which are you referring to as the primary comparison?
If I'm understanding the book's structure correctly, the comparison at the end of Part 1 (chapter 18 "Can we live on renewables?") is based on estimating existing demand. Deployment of heat pumps in Britain even today is woefully low, and when the book was written it was no doubt even lower, so of course it wouldn't make sense to include heat pumps as a significant factor when comparing actual demand when the book was written with potential supply.
Chapter 27 "Five energy plans for Britain" discusses large scale ways to make the energy budget "work", and those hypothetical comparisons do include use of heat-pumps. Maybe those numbers are inaccurate and a better hypothetical could be produced today, but I would first put that down to the difficulty of forecasting the future.
It's been a long time since I read the book fully though. Did I miss something?
pfdietz 1 days ago [-]
When asking that question it's a mistake to assume no technological change/improvement. The process that would require the adaptation would drive changes in the technologies.
kragen 1 days ago [-]
> His forecasts of the impact of solar and wind is based on prices and performance from 2008. Prices have come down an order of magnitude since then
This is going to sound like one-upmanship or nitpicking, but I think it's important to know that this understates the change. https://web.archive.org/web/20100722072720/http://www.solars... says that in May 02009, crystalline solar cells in China cost €2.17 per peak watt, a decline of 26.4% from January 02009, whose price is not listed directly but which we can calculate as €2.95 per peak watt. If the price had declined by only an order of magnitude since January 02009, it would now be €0.295 per peak watt.
But, according to https://www.in2013dollars.com/europe/inflation/2009?amount=1..., "€100 in 2009 is worth €145.57 today." So, if we adjust for inflation — as we should — if the real price had declined by only an order of magnitude since January 02009, it would now be €0.429 per peak watt.
So the price of solar modules now is actually 3.3 times lower than what a careful reader would infer from your remark. Solar module prices have declined since January 02009 by not merely an order of magnitude but 33×. That's slightly closer to two orders of magnitude than to the single order of magnitude you said. Now they are at 3% of the price they were at when MacKay wrote his excellent book.
(Which does, as others have pointed out, explain the efficiency advantage of heat pumps.)
paimapi 1 days ago [-]
one thing to note is that the solar industry has receded quite a bit in the last two years in China due to overproduction (or, as the Chinese state likes to call it, 'involution' or 'too much competition'). solar is cheap now because 1) Chinese subsidies are reduced, shrinking their installation market and 2) overproduction leading to essentially fire sales. once production stabilizes against the market, costs will go back up. it's really never been a better time to buy panels than now
>Some observers estimate 20-30% capacity reductions are required, but demand shrinkage could increase that figure. “I’m particularly worried about the downstream side,” says Reis. “Even as prices collapsed, demand remained robust for three years, but power market reforms are now upending the entire renewables market.”
combine this with the global backing-off of the Paris Agreement (and subsequent subsidy defunding) and power utilities in the US abandoning clean energy goals in order to immediately increase output for proposed hyperscale facilities and you've got something of an enduring demand shortage
that said, there is a lot of automation happening in that industry right now (which is likely going to cause a small recession in China due to half a million to a million workers being out of a job, depending on how much the parts manufacturers also automate) so it's possible production with continue improving as more R&D is dedicated there. only time will tell!
kragen 21 hours ago [-]
"Overproduction" is nonsense, and solar panel prices have been continuously dropping dramatically for 50 years now; they're not likely to stop anytime soon.
Current solar panel production is only about a terawatt per year, which would take about 80 years to merely replace all of global marketed energy consumption (≈20TW, but those are not peak watts), and 90,000 years to reach Kardashev Type 1, where total solar power capture is roughly equal to the amount reaching the Earth. So current solar panel production is too low by roughly a factor of 1000.
We're very far from overproduction of solar panels. What we have is underconsumption of solar panels. But that has been improving dramatically year by year, and will probably continue to improve.
Yes, there is currently a shakeout where lots of solar companies are likely to go bust. That's what happens in industries that are growing rapidly: you have to place big bets to stay in the game, and sometimes you fuck it up and your company blows up. It's been happening for 20 years already — the article you linked mentions three big shakeout cycles that I remember, and I think there have been others I just wasn't paying attention to.
Speaking of not paying attention, if you think "it's really never been a better time to buy panels than now", you clearly haven't been watching module prices, even though I linked the historical data in the comment you are replying to, and I even quoted some prices. Prices are up 20–30% since the beginning of this year, and since November (€0.065/Wp low-cost, €0.100/Wp mainstream, €0.130/Wp high efficiency) they're up by 30–40%.
There had never been a better time to buy solar panels than last November. That's the usual situation with technological progress, actually: there has never been a better time to buy a thing than right now, and if you wait another month, it will get even cheaper. Last year, prices were mostly flat; November was the low for low-cost modules and high-efficiency modules, while mainstream panels were actually 5% higher than their low, which they had first hit in November 02024. But, still, high-efficiency panels hit record lows last year in January, August, September, and November, while low-cost panels hit record lows in July and November. The year before was one of vertiginous price declines: high-efficiency panels hit record lows in January, February, March, May, July, August, September, October, and November; mainstream panels hit record lows in January, March, June, September, and November; and low-cost panels hit record lows in January, April, August, October, and November.
This followed a three-year gradual rise in prices starting in late 02020, but we also saw record-low monthly prices in most months of 02020, most months of 02019, and all months of 02018.
In any of those months, you could have correctly said, "it's really never been a better time to buy panels than now," even though an even better time was coming up, in most cases, a month or two later. Prices have shot up this year, just like they did in 02020–02022, but within three or four years at most, they'll be lower again. Swanson's Law https://en.wikipedia.org/wiki/Swanson%27s_law remains in operation, and on the Wikipedia page you can find a nice graph from 01975 to 02024.
You said, "combine this with the global backing-off of the Paris Agreement (and subsequent subsidy defunding) and power utilities in the US abandoning clean energy goals in order to immediately increase output for proposed hyperscale facilities and you've got something of an enduring demand shortage", but this is nonsense reasoning, because you've buried a false premise: you think that solar panels are a more expensive way to generate energy than fossil fuels, which is wrong.
In fact, as should have been immediately obvious from the prices I already quoted in the comment you were responding to, solar panels are now enormously cheaper than thermal power plants, even before you add in the cost of the fuel. The proposed hyperscale datacenter facilities are precisely where the demand for today's ultra-cheap solar energy is going to come from — people in the US are spinning up portable gas turbine generators to power their data centers for regulatory reasons, but that's a desperate stopgap, not a long-term solution.
Energy is one of the largest cost items for any datacenter, so ultimately nobody can run a competitive datacenter on fossil fuels, not when they're competing against solar.
ShadowOfThePit 7 hours ago [-]
why do you prepend a zero on every year
bryanlarsen 1 days ago [-]
> Prices have come down an order of magnitude since then
$10/W to 0.30/W is closer to 2 orders of magnitude than 1.
LogicFailsMe 1 days ago [-]
Not bad at all for an early amazingly influential AI researcher and Hopfield graduate who died tragically of pancreatic cancer just as AI took off.
Another thing to point out is that the geography in the book, the UK, has spectacularly bad resources for solar, just astoundingly bad.
So even with updated technology pricing numbers, the conclusions from it should not be lifted to other geographies without adjusting for that. We're talking worse resources than Germany (worse than an US state), and into Finland territory:
Didn't he also assume a significant amount of bioenergy, which ended up greatly inflating the land area needed?
sideway 1 days ago [-]
Any book recommendations on the subject (or similar subjects)?
nikilr 21 hours ago [-]
wait how does that work? because you're borrowing the heat from somewhere else?
dragonwriter 20 hours ago [-]
Yes, that’s why it is called a “heat pump”. It leverages the temperature change from compression expansion of a refrigerant that cycles in a loop to gather heat from one environment and deliver it to another, so that (within limits of temperature on both ends) it can heat or cool a targeted space, doing the opposite elsewhere—outside (or in the ground, for a geothermal system), when we are talking about the first space as a building, generally.
quickthrowman 22 hours ago [-]
> with a electric heat pump you only need 1/6 J to get 1J of heat
The COP of a heat pump is not fixed at 6, it’s dependent on the delta T between the evaporator and condenser. As delta T grows, efficiency drops.
An air source heat pump will have a COP of 2 with a delta T of 70F/39C and a COP of ~4-5 with a 10F/5.5C delta T.
I’ve only ever seen a COP higher than 6 in a system that had a chilled water loop with chillers and cooling towers.
antisthenes 1 days ago [-]
That doesn't mean it's flawed. It means the arguments are even MORE in favor of what is stated in the book.
The underlying fundamentals did not change since 2008. If Solar was good/viable back then, it can only get better if it got cheaper over time.
Same goes for the nuclear debate. Nuclear was losing back then, and now it has finally lost absolutely.
aaron695 22 hours ago [-]
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zbs1970 1 days ago [-]
Not commenting on the physics of this; I want to point out that I thought the narrative structure of this book was amazing. I have not read a hard-core piece of analysis in any field before or since that I thought was a page-turner the way this was. When I read it in 2008 I remember completing each chapter and feeling like "we're screwed" and then the next chapter feeling like "ok, we're going to make it." Presenting such analysis in the form of a race between supply and demand was narrative genius and I think should serve as an example of how ideas can be presented in a way that is both exciting and not-dumbed-down.
Risking the HN hug of death here, but my own prototype of a car miles model inspired by the David's approach can be found at https://trafred.cardiff.ac.uk/
ajb 1 days ago [-]
Oh, very interesting. Not sure it's working correctly though: set everything to ambition level 4, which takes us to net zero minus 4. Then, the following knobs have no effect: efficiency, nuclear power, carbon intensity, solar (!) and wave & tidal. That can't be true, so I think it's buggy
cs1996 1 days ago [-]
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sam1r 1 days ago [-]
The original author was blogging just a couple days prior to his death. Rest in peace
That book significantly decreased my appreciation of our statistics professor @uni, because it presented the same topics in a much more interesting and digestible way. Can recommend.
That book and Gershgorin circles (to work around all the stupid, constructed 3x3 matrix eigenvalue problems that they love to sprinkle into literally every early stem exam) helped more in university than anything else.
esafak 1 days ago [-]
The late author.
ml_basics 1 days ago [-]
The untimely death of David MacKay was a tragic loss for the scientific community. It's astonishing that he wrote the textbook on information theory for the ML community as well as his contributions to rational discussion about energy policy.
He had a direct personal impact on my life since my introduction to ML came from video recordings of his lectures on ML and information theory. I am grateful to have learned from such an excellent teacher. Like a Feynman of our times.
I find it interesting that the average energy consumption of a person (or household?) is roughly 30kWh/day and the energy usage of a car is roughly 40kWh/day. I wonder if it's some kind of truism that our transportation needs roughly equal our energy needs.
I'd be interested to know if that's just a coincidence or whether there's an underlying reason.
tomjakubowski 1 days ago [-]
A person riding a bicycle expends an order of magnitude less energy than does a car ferrying the same person the same distance. So I don't think this really holds.
For comparison: at 50 MPG, traveling one mile by car uses 0.02 gallons of gasoline. This is about 675 Wh of energy or 580 kcal. Travel by bicycle for a ~180lb person is about 60 kcal per mile.
abcd_f 1 days ago [-]
And a straight angle is just 10 degrees away from the water's boiling point. Might be something in it too :)
1 days ago [-]
hungryhobbit 1 days ago [-]
Dear god, this page is like an argument against every person who has ever said "graphic design doesn't matter".
The colors are gross, it took me ten minutes just to figure out what I was looking at (a book), and heaven help me if I actually wanted to read that book in that format!
slibhb 24 hours ago [-]
Hmm, I kind of like it. It comes across as hand-crafted and I spent longer there than I planned.
I remember him giving this talk to my physics class when I was in University. It was so inspirational to me that the UK just might be able to go 100% renewable.
From what I remember, the calculation worked out how we could do it all with Solar. I don't think he quite saw how close we are to achieving the goal, not with Solar, but with Wind within the next decade.
PaulDavisThe1st 1 days ago [-]
The publisher of this book (and the series) was my second programming mentor, and the person who introduced me to the GNU Project and libre software in general, back in 1986/87. I call him Dr. X and he calls me "The Professor".
mbgerring 23 hours ago [-]
Site last modified in 2015
Lots of us working in clean energy read this book, and everything that’s happened since it was published makes the projections here useless
throwawayffffas 1 days ago [-]
I see a lot of hot air in this.
Two quick points:
1. Gasoline powered energy metrics do not translate to electric vehicles, due to the much higher efficiency of electric motors.
2. There are about twice as many people as cars in the UK so the comparison between 40 kwh/d per car and 20 kwh/d per person for the wind energy is at minimum misleading.
citizenfishy 1 days ago [-]
Lings Cars!
1 days ago [-]
rekabis 22 hours ago [-]
Holy 1997 web design, Batman.
perennialreport 1 days ago [-]
Worth reading even with the dated numbers. MacKay's lasting contribution isn't any specific forecast - it's the discipline of expressing everything in the same units (kWh per day per person), which makes energy arguments commensurable instead of vibes-based. Once you've internalized that, most energy coverage in the media starts reading like category errors. The specific figures have moved - solar costs, EV adoption, heat pump uptake - but the arithmetic habit hasn't aged at all.
bryanlarsen 1 days ago [-]
kWh of work and kWh of primary energy are two different measurements with the same unit. Mixing the two is invalid.
It is also a product of its time in terms of wind/solar vs nuclear. His forecasts of the impact of solar and wind is based on prices and performance from 2008. Prices have come down an order of magnitude since then, and performance and lifespan have increased drastically.
I imagine the economics (and perhaps technical improvements) of some things may have changed more than the book could forecast. But heat pumps were definitely understood by the author.
Look at “3 - Cars” on page 29. He says the typical car uses 40 kWh/day. 40 kWh of what? Chemical energy in the gasoline.
The go to page 33 where he looks at how much energy onshore wind could produce per days in the UK. His number is 20 kWh/d. 20 kWh of what? electricity
He then compares those two numbers directly and uses that comparison as the basis of his arguments: “Britain’s onshore wind energy resource may be “huge,” but it’s evi- dently not as huge as our huge consumption.”
This is simply incorrect. A combustion engine converts less than half of the chemical energy in the gasoline into mechanical work that can move the car. The electric model converts >90% of it. So we don’t have to replace 40 kWh/day, we have to replace less than half of that since the electric process is more efficient.
This same issues, the primary energy fallacy, underpins large parts of the book.
The wind analysis was reasonable for the time, iirc the main error there was that he failed to foresee offshore wind dropping in price so much.
And graphs like the one comparing wind turbine output to petrol car consumption are inherently deceiving. Two values are put side by side with the same units and then talk about directly as if they are comparable. But they simply are not. A kWh of chemical energy and a kWh of electricity have as much in common as a US dollar and a Jamaican dollar.
1. Sad that he died from cancer
2. Noticed he compared primary energy and felt stupid for missing that
MacKay's "renewables can't work alone" claim always seemed carefully scoped to the economics of 02008 (when solar modules cost 33× as much as they do now) and also his own densely populated, rather polar country. Renewables were already working nearly alone, at scale, in equatorial countries and more sparsely populated countries; I live in Argentina, whose grid was mostly hydroelectric at the time, and next door to Brazil, where a large fraction of the automotive fleet ran on sugar-cane-derived ethanol, which is a viable renewable energy source (unlike, apparently, corn ethanol).
There's some incredible progress for electricity generation, but there's still huge amounts of energy being used in ways that are not currently electrified and not close to electrifiable in the short term.
We should celebrate the forward progress, but also not be blind to what is not yet feasible (while also hoping that it may soon be so).
(Yes, I know that makes me sound like an LLM.)
Thankfully, energy storage is being deployed worldwide, so this is a moot point, and renewables can and will replace fossil fuel electricity generation.
I saw him present 18 years ago, and asked him why: he said that he didn't want to rely on any predictions or models, but only discuss real data. Which is sort of defendable as a position, but ignored the fact that renewable energy was progressing so incredibly fast, and that these engineering predictions were not speculative but very much concrete.
Similarly the silicon solar panel industry in 2008 had a roadmap to get to £1/Wp over the next few years (which they did, and which led to the ~2012 explosion in solar installations), by mass producing the 'expensive' ~20% efficient (mono-crystalline silicon) technology. Mackay uses a 10% figure throughout.
So overall this was a bit like making predictions in the year 2000 assuming everyone will be stuck on 56k dial-up forever, because most people are on 56k dial-up.
These biases are present in all of the discussion of renewable technology, yet nuclear gets a free-ride / magical thinking in terms of uranium extraction, waste disposal and cleanup. And then there is the persistent obsession with land use in the book.
This led me to the conclusion (which I still hold) that this was an example of the tail wagging the dog: David MacKay wanted the 'obvious' physicists answer of nuclear power to be the natural conclusion, and by construction made it so in his book. Just because you are a Bayesian does not mean that you are unbiased!
David MacKay was an amazing scientist, but I do not think this book is accurate (even for its time), or that useful in public understanding of what we now call 'Net Zero'. It certainly popularised the idea of actually thinking through individual energy budgets, which can only be a good thing, but it was a massive missed opportunity to treat heat (chemical) energy (maximum entropy) and electrical (which can directly do work) as equivalent, just because they have the same unit.
Later on, as the 'Climate Tsar' he made a web app where you could play with the future balance of generation with a simulated model of the UK, and set your own costs for the different technologies, which I thought was much more useful. You could choose your own energy mix, and understand some of the tradeoffs.
And yes, very sad that he died so young. In the context of this book it would have been interesting to see how he dealt with the increasing mismatch of reality and his predictions as time passed.
> There is this appalling delusion that people have that we can take this thing that is currently producing 1% of our electricity and we can just scale it up and if there is a slight issue of it not adding up, then we can just do energy efficiency,” he said. “Humanity really does needs to pay attention to arithmetic and the laws of physics – we need a plan that adds up.”
> Prof MacKay had previously avoided being drawn into the political debate about energy, but told Lynas: “I have always tried to avoid advocating particular solutions but maybe because time is getting thinner I should call a spade a spade.”
> The key for the UK, he said, was a zero-carbon solution that works in the winter, when energy demand is highest but sunshine is lowest and winds can drop for days at a time. “The sensible thing to do for a country like the UK, I think, is to focus on CCS, which the world needs anyway, and nuclear,” said Prof MacKay.
> The decision on a new nuclear power plant at Hinkley Point, which the government hopes will be the first of a new generation of plants, has been delayed until September.
> “Then if you ask what is the optimal amount of wind and solar to add in then the answer is going to be almost zero,” he said. “I love wind turbines – they are the cathedrals of the modern age – but they are a waste of money if you have a low carbon solution that gets you through the winter … because when the wind blows you are going to have to either turn them down or something else down that you have already paid for like nuclear or CCS.”
Maybe he would have changed his mind as prices and delivery timelines diverged but many of the people who were most enthusiastic about his work because it reflected their nuclear preference didn't, so who knows.
Though maybe his kind of person that liked nuclear and heat pumps and EVs all just changed their mind based on new evidence and we are left with the people who mysteriously like nuclear but don't want to use the output for heat and transport.
There's something really important to understand when evaluating non-fiction books: nobody reads the later chapters, and the authors generally know this. They can present tremendously one-sided information in the first few chapters, giving the spin that they want, and then in later chapters give a more balanced approach to shield themselves from criticism. Almost everyone who reads the book will read only the spin, but any criticism levied against the author will be met with "but I specifically say, in the later chapters ...". It's a slimy technique that you start to see everywhere once you're aware of it.
Asserted without evidence, and I very much doubt that it's true. I suspect it varies dramatically by subject matter, intended audience, book length, data density, and more. I have no evidence for any of that. Do you?
Not necessarily saying this generalises to all non fiction books though
(Admittedly, I read it many years ago, my memory may be off, though I strongly doubt it.)
So I think as a conservative estimate, it kinda works.
- https://en.wikipedia.org/wiki/MStar (patent infringement, the remains bought by MediaTek)
- https://en.wikipedia.org/wiki/Green_Flash_Brewing_Company (succumbed to competition from local craft breweries, lender foreclosed, the remains bought by private equity)
- https://en.wikipedia.org/wiki/Primaris_Airlines (bankrupt in 02008, unclear why)
And those are cherry-picked from companies that got big enough to be "notable" by Wikipedia's guidelines. Far more companies never reach that level.
The conservative estimate is that any time someone tries to deploy a new technology, it will fail. Most innovations (new technologies or companies) do.
Take a look at the HN front page from 10 years ago: https://news.ycombinator.com/front?day=2016-09-28 There we see Uber's self-driving truck initiative Otto (an acquisition), deep learning startup Skymind, a new static Linux distro called Stali, and a bunch of things that weren't innovations. All three of those things failed; Stali hasn't been updated since 02019. LuaTeX, Coinbase, Linux, Wikipedia, and dyeing with indigo are other innovations that feature on that page, but they were already very old.
Chapter 21 of draft 2.9.3 from 02008 https://web.archive.org/web/20080906132444/http://www.infere... begins:
> In the last chapter, we learned that electrification could shrink transport’s energy consumption to one fifth of its current levels; and that public transport and cycling can be about 40 times more energy-efficient than car-driving. How about heating? What sort of energy-savings can technology or lifestyle-change offer?
and it goes on to talk about heat pumps, as today. So I think that even versions from 02008 got this right, though evidently that was at least the 13th numbered draft.
This is right. This shows 63% wasted (as of 2024).
https://flowcharts.llnl.gov/sites/flowcharts/files/2026-08/2...
I remember this was 67% just a few years back. May have gone down because of increase in solar.
sustainabilitybynumbers (Hannah Ritchie) had an article talking about this, that we need only 25%-ish in renewables. I am unable to find that article.
(edit) found the article
https://hannahritchie.substack.com/p/electrification-energy-...: Global final energy demand today2 compared to a ‘post-transition’ energy system where suitable sectors are electrified, and the rest is fuelled by hydrogen. Electricity demand does increase – from 110 to 189 EJ, but total energy demand drops from 416 to 247 exajoules (EJ).
Technically you can interconvert grams of lead and grams of gold one to one, too, but interconverting electrical and thermal energy is so easy that it happens all the time unintentionally.
MacKay does in fact cover the Carnot factor you're talking about; his Chapter 21 http://www.withouthotair.com/c21/page_140.shtml begins:
> In the last chapter, we learned that electrification could shrink transport’s energy consumption to one fifth of its current levels; and that public trans- port and cycling can be about 40 times more energy-efficient than car- driving. How about heating? What sort of energy-savings can technology or lifestyle-change offer?
And then he goes into not just household heat pumps, and their achievable coefficients of performance, but also municipal combined heat and power, which take that ≈50% of the chemical energy "lost" from thermal power plants as waste heat and pumps it into your house.
So, far from being ignorant of the issue as you seem to be implying, he presents a more complete picture of the issues than you are presenting.
Specifically for household climate control, I suspect that both heat pumps and CHP are much less relevant now that we have cheap solar. You can think of a heat pump as a way to reduce the amount of solar-panel area that you need to heat your house. The trouble is that solar panels cost €0.13 per peak watt, while heat pumps cost closer to €1 per peak watt, so it may be cheaper to "waste" energy on heating your house resistively with a nichrome wire than to use a carefully engineered heat pump.
When that absolute worst case is happening in the house's living space, we can and do "convert" heat to electrical energy savings 1:1, because every joule "wasted" by cooking food with gas, or heating the house with a corn stove, or warming up the floor with sunlight for passive solar gain, is another joule earlier that the space heater's thermostat will turn it off.
Also, I don't think it's accurate to describe electrical resistance heating as "the thermodynamically worst heating technology possible". Electrical resistance heating is generally close to 100% efficient. It's actually thermodynamically possible to make heaters that are less than 100% efficient; MacKay explains, for example, that he heats his house with a 90%-efficient condensing boiler, and it's common for fireplaces to be around 20% efficient, because most of the heat goes up the chimney instead of heating your house.
Fireplaces are actually thermodynamically possible machines. I understand that you've never seen one, but I assure you that they do exist.
I've actually lived in houses where the fireplace had negative efficiency at times, sucking more heat out of the house (in the form of warm air) than they added back in the form of radiation.
We're suspecting there to be some symmetry breakage to explain why we don't really see any globs of antimatter with our telescopes (at least none that show any evidence of being antimatter), but so far no (real) luck.
As for the "0.13€ vs. 1€": you're not gonna get much solar yield in peak winter at least in Central Europe, especially it's gonna be that your PV is going to charge <100hour electricity storage when the sun shows up on those winter days and the heat pump (at least the part that spends a little electricity to lift a lot of heat energy from outside temps to indoor temps) runs approximately continuously.
You might have some kind of e.g. water/water heat pump with salted (not table salt though) water deliberately thawing during daytime (by turning on the circulation between it and outside air) to freeze at much warmer than night air temperatures to buffer those "only mildly freezing" temperatures to improve the efficiency (and at that point, likely also the thermal output power) of the heat pump.
The radiators inside and potential fans for them would also go up in flow to make up for the increased losses through the walls/window-glass.
A big reason why at least in e.g. Germany heat pumps are not at all irrelevant vs. electric resistance "space heaters" is that they're also very efficient at handling spring/autumn (lower thermal delta to lift against; referencing to a resistance heater for scale/reference purposes but clearly not expecting that to be a benchmark) while easily offering summer cooling (with relatively minor incremental complexity).
I don't really know how inherently expensive it is to keep around at least for parts of each city, but existing natural gas central heating boilers are very useful to not just trash before they're broken just because one uogrades to a heat pump, specifically because they are already there (sunk cost/little scrap value) and have basically zero issue delivering extremely spiky power during unannounced winter days (well, takes maybe a day of notice to actually get crew in to the storage&distribution facilities, but weather forecasts easily cope).
Sure, it's not _efficient,_ but we could just divert some synthetic methane during summer to refill the caverns: we kinda want that (at least for hydrogen but methane works too at least for storage) anyways for chemical synthesis factories if we're not just gonna feed them crude oil/natural gas, so other than that chemical factories probably/largely prefer direct hydrogen, continuing to use our existing seasonal storage even if it's not getting refilled from NordStream2 but from local summer-only electrolysis plants and with more hydrogen than methane where the geology allows, seems to me just frugal dealings with nature (reduce, Reuse, recycle).
I admit I don't know much about nuclear reactions, so please let me know if I'm talking nonsense here.
I agree that Central European capacity factors for solar are pretty bad, and that heat pumps are still economical in more polar countries, and will remain so for a few more years.
I'll answer the rest of your extremely interesting comment later, as I'm being drawn away at the moment, but I want you to know that I appreciate it very much.
Much less. Your typical gasoline IC vehicle converts maybe 1/4 of the chemical energy into work.
So really the comparison is 7.5kWh of electricity compared to 21.6kWh of petrol. The Prius gets 34% of the miles compared to the Tesla for a given energy input. In the olden days when renewables didn't do much, the chemical energy input for 7.5kW of electricity was probably 15 kWh. So the electric car is a little bit more efficient (taking advantage of the efficiency of large power plants).
These days, thanks to renewables the fossil fuel input into the electricity is lower.
Also, natural gas to electricity in CC plants is ~60% efficient.
Interestingly thanks to renewables the "carbon intensity" of a kWh of electricity is already better than a kWh of fossil fuels in some countries. A kWh of petrol releases about 250g of CO2, and quite a few countries (predominantly developed ones) have lower carbon intensities per kWh of electricity. Considering round trip efficiencies the carbon released by an electric car in those countries is easily 1/3 to 1/4 of the carbon released by a petrol car.
In the USA it's not as good, but electric cars are still releasing about half the carbon.
> Let me spell this out. Heat pumps are superior in efficiency to condens- ing boilers, even if the heat pumps are powered by electricity from a power station burning natural gas. If you want to heat lots of buildings using natural gas, you could install condensing boilers, which are “90% ef- ficient,” or you could send the same gas to a new gas power station making electricity and install electricity-powered heat pumps in all the buildings; the second solution’s efficiency would be somewhere between 140% and 185%. It’s not necessary to dig big holes in the garden and install underfloor heating to get the benefits of heat pumps; the best air-source heat pumps (which require just a small external box, like an air-conditioner’s) can deliver hot water to normal radiators with a coefficient of performance above 3.
They're just usually deployed for frozen warehouses, factories that actively freeze large amounts of (usually food), and AFAIK the occasional ice(hockey) rink.
Shitty types that don't even bother with any decent controls/pumps (those 90% boilers use a water loop circulation pump and a combustion air blower together with a bunch of sensors and valves) run propane-fired in many camper vans to do the fridge. But at the scale of an apartment building fit for 50+ residents, a natural gas fired central heat pump can be _quite_ efficient and economical.
Thermodynamically they're a heat engine with high combustion/flame temperature that uses the warm side as the heat sink, mated to a heat pump that consumes the produced "mechanical/electrical grade" power to pump heat from the cold side to _also_ the warm side. You save the turbine! Also the electrics but they're probably not even that expensive relative to the rest of the 200MW-class combined cycle natural gas power plant.
If I'm understanding the book's structure correctly, the comparison at the end of Part 1 (chapter 18 "Can we live on renewables?") is based on estimating existing demand. Deployment of heat pumps in Britain even today is woefully low, and when the book was written it was no doubt even lower, so of course it wouldn't make sense to include heat pumps as a significant factor when comparing actual demand when the book was written with potential supply.
Chapter 27 "Five energy plans for Britain" discusses large scale ways to make the energy budget "work", and those hypothetical comparisons do include use of heat-pumps. Maybe those numbers are inaccurate and a better hypothetical could be produced today, but I would first put that down to the difficulty of forecasting the future.
It's been a long time since I read the book fully though. Did I miss something?
This is going to sound like one-upmanship or nitpicking, but I think it's important to know that this understates the change. https://web.archive.org/web/20100722072720/http://www.solars... says that in May 02009, crystalline solar cells in China cost €2.17 per peak watt, a decline of 26.4% from January 02009, whose price is not listed directly but which we can calculate as €2.95 per peak watt. If the price had declined by only an order of magnitude since January 02009, it would now be €0.295 per peak watt.
But, according to https://www.in2013dollars.com/europe/inflation/2009?amount=1..., "€100 in 2009 is worth €145.57 today." So, if we adjust for inflation — as we should — if the real price had declined by only an order of magnitude since January 02009, it would now be €0.429 per peak watt.
In fact, today, "mainstream" solar modules are currently €0.130 per peak watt, according to https://www.solarserver.de/photovoltaik-preis-pv-modul-preis..., and those are Chinese monocrystalline modules.
So the price of solar modules now is actually 3.3 times lower than what a careful reader would infer from your remark. Solar module prices have declined since January 02009 by not merely an order of magnitude but 33×. That's slightly closer to two orders of magnitude than to the single order of magnitude you said. Now they are at 3% of the price they were at when MacKay wrote his excellent book.
(Which does, as others have pointed out, explain the efficiency advantage of heat pumps.)
https://dialogue.earth/en/energy/behind-the-layoffs-in-china...
>Some observers estimate 20-30% capacity reductions are required, but demand shrinkage could increase that figure. “I’m particularly worried about the downstream side,” says Reis. “Even as prices collapsed, demand remained robust for three years, but power market reforms are now upending the entire renewables market.”
combine this with the global backing-off of the Paris Agreement (and subsequent subsidy defunding) and power utilities in the US abandoning clean energy goals in order to immediately increase output for proposed hyperscale facilities and you've got something of an enduring demand shortage
that said, there is a lot of automation happening in that industry right now (which is likely going to cause a small recession in China due to half a million to a million workers being out of a job, depending on how much the parts manufacturers also automate) so it's possible production with continue improving as more R&D is dedicated there. only time will tell!
Current solar panel production is only about a terawatt per year, which would take about 80 years to merely replace all of global marketed energy consumption (≈20TW, but those are not peak watts), and 90,000 years to reach Kardashev Type 1, where total solar power capture is roughly equal to the amount reaching the Earth. So current solar panel production is too low by roughly a factor of 1000.
We're very far from overproduction of solar panels. What we have is underconsumption of solar panels. But that has been improving dramatically year by year, and will probably continue to improve.
Yes, there is currently a shakeout where lots of solar companies are likely to go bust. That's what happens in industries that are growing rapidly: you have to place big bets to stay in the game, and sometimes you fuck it up and your company blows up. It's been happening for 20 years already — the article you linked mentions three big shakeout cycles that I remember, and I think there have been others I just wasn't paying attention to.
Speaking of not paying attention, if you think "it's really never been a better time to buy panels than now", you clearly haven't been watching module prices, even though I linked the historical data in the comment you are replying to, and I even quoted some prices. Prices are up 20–30% since the beginning of this year, and since November (€0.065/Wp low-cost, €0.100/Wp mainstream, €0.130/Wp high efficiency) they're up by 30–40%.
There had never been a better time to buy solar panels than last November. That's the usual situation with technological progress, actually: there has never been a better time to buy a thing than right now, and if you wait another month, it will get even cheaper. Last year, prices were mostly flat; November was the low for low-cost modules and high-efficiency modules, while mainstream panels were actually 5% higher than their low, which they had first hit in November 02024. But, still, high-efficiency panels hit record lows last year in January, August, September, and November, while low-cost panels hit record lows in July and November. The year before was one of vertiginous price declines: high-efficiency panels hit record lows in January, February, March, May, July, August, September, October, and November; mainstream panels hit record lows in January, March, June, September, and November; and low-cost panels hit record lows in January, April, August, October, and November.
This followed a three-year gradual rise in prices starting in late 02020, but we also saw record-low monthly prices in most months of 02020, most months of 02019, and all months of 02018.
In any of those months, you could have correctly said, "it's really never been a better time to buy panels than now," even though an even better time was coming up, in most cases, a month or two later. Prices have shot up this year, just like they did in 02020–02022, but within three or four years at most, they'll be lower again. Swanson's Law https://en.wikipedia.org/wiki/Swanson%27s_law remains in operation, and on the Wikipedia page you can find a nice graph from 01975 to 02024.
You said, "combine this with the global backing-off of the Paris Agreement (and subsequent subsidy defunding) and power utilities in the US abandoning clean energy goals in order to immediately increase output for proposed hyperscale facilities and you've got something of an enduring demand shortage", but this is nonsense reasoning, because you've buried a false premise: you think that solar panels are a more expensive way to generate energy than fossil fuels, which is wrong.
In fact, as should have been immediately obvious from the prices I already quoted in the comment you were responding to, solar panels are now enormously cheaper than thermal power plants, even before you add in the cost of the fuel. The proposed hyperscale datacenter facilities are precisely where the demand for today's ultra-cheap solar energy is going to come from — people in the US are spinning up portable gas turbine generators to power their data centers for regulatory reasons, but that's a desperate stopgap, not a long-term solution.
Energy is one of the largest cost items for any datacenter, so ultimately nobody can run a competitive datacenter on fossil fuels, not when they're competing against solar.
$10/W to 0.30/W is closer to 2 orders of magnitude than 1.
https://en.wikipedia.org/wiki/David_J._C._MacKay
So even with updated technology pricing numbers, the conclusions from it should not be lifted to other geographies without adjusting for that. We're talking worse resources than Germany (worse than an US state), and into Finland territory:
https://globalsolaratlas.info/
The COP of a heat pump is not fixed at 6, it’s dependent on the delta T between the evaporator and condenser. As delta T grows, efficiency drops.
An air source heat pump will have a COP of 2 with a delta T of 70F/39C and a COP of ~4-5 with a 10F/5.5C delta T.
I’ve only ever seen a COP higher than 6 in a system that had a chilled water loop with chillers and cooling towers.
The underlying fundamentals did not change since 2008. If Solar was good/viable back then, it can only get better if it got cheaper over time.
Same goes for the nuclear debate. Nuclear was losing back then, and now it has finally lost absolutely.
Risking the HN hug of death here, but my own prototype of a car miles model inspired by the David's approach can be found at https://trafred.cardiff.ac.uk/
https://itila.blogspot.com/2015/09/what-do-you-tell-children...
Sustainable Energy – without the hot air (2008) - https://news.ycombinator.com/item?id=33957424 - Dec 2022 (2 comments)
Sustainable Energy without the Hot Air (Revised, Community Edition) - https://news.ycombinator.com/item?id=29056343 - Oct 2021 (133 comments)
Keeping David MacKay's 'Sustainable Energy – without the hot air' up-to-date - https://news.ycombinator.com/item?id=14009057 - March 2017 (39 comments)
"Sustainable Energy - Without the Hot Air" by David JC MacKay - https://news.ycombinator.com/item?id=845446 - Sept 2009 (31 comments)
See also:
Can solar and wind power Britain? An update of David MacKay's numbers - https://news.ycombinator.com/item?id=38151453 - Nov 2023 (299 comments)
Sir David MacKay obituary (2016) - https://news.ycombinator.com/item?id=35670145 - April 2023 (1 comment)
David MacKay, FRS died today, his diary is remarkable - https://news.ycombinator.com/item?id=11500614 - April 2016 (1 comment)
Note the .com->.org: its a version of the book whose numbers are maintained here <https://github.com/life-itself/without-hot-air/commits/main/>.
https://news.ycombinator.com/item?id=34618613 ("Information Theory, Inference, and Learning Algorithms (2003) (inference.org.uk)")
That book significantly decreased my appreciation of our statistics professor @uni, because it presented the same topics in a much more interesting and digestible way. Can recommend.
That book and Gershgorin circles (to work around all the stupid, constructed 3x3 matrix eigenvalue problems that they love to sprinkle into literally every early stem exam) helped more in university than anything else.
He had a direct personal impact on my life since my introduction to ML came from video recordings of his lectures on ML and information theory. I am grateful to have learned from such an excellent teacher. Like a Feynman of our times.
There was some rough discussion in 2025 about where Mackay's models ended up being off: https://bsky.app/profile/ketanjoshi.co/post/3lmdeoxe2pk2i
And of course some credit that he was right on some technologies not making much sense like electric planes: https://bsky.app/profile/thierryaaron.bsky.social/post/3mwjx... referencing ch 5 pg 35 of 'sustainability without the hot air'
I'd be interested to know if that's just a coincidence or whether there's an underlying reason.
For comparison: at 50 MPG, traveling one mile by car uses 0.02 gallons of gasoline. This is about 675 Wh of energy or 580 kcal. Travel by bicycle for a ~180lb person is about 60 kcal per mile.
The colors are gross, it took me ten minutes just to figure out what I was looking at (a book), and heaven help me if I actually wanted to read that book in that format!
I remember him giving this talk to my physics class when I was in University. It was so inspirational to me that the UK just might be able to go 100% renewable.
From what I remember, the calculation worked out how we could do it all with Solar. I don't think he quite saw how close we are to achieving the goal, not with Solar, but with Wind within the next decade.
Lots of us working in clean energy read this book, and everything that’s happened since it was published makes the projections here useless
Two quick points:
1. Gasoline powered energy metrics do not translate to electric vehicles, due to the much higher efficiency of electric motors.
2. There are about twice as many people as cars in the UK so the comparison between 40 kwh/d per car and 20 kwh/d per person for the wind energy is at minimum misleading.