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.
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: <a href="https://www.withouthotair.com/c21/page_150.shtml" rel="nofollow">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.
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.
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.
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.
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
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).
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).
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.
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.
Planes are unlike other sorts of transportation in that their energy consumption is pretty closely proportional to their weight, because they are constantly spending energy throwing air downward to support their weight, so the low energy densities of rechargeable batteries are very unappealing for long-distance flight. Plausible alternatives include airships, ultra-low-stall-speed planes like gliders and Burt Rutan's Voyager, aluminum-air batteries, and synfuel. Of course, short-distance planes are already going electric with Joby.
Ships, we'll see. Most shipping ships are container ships (as opposed to, say, tankers, cruse ships, or ship shipping ships shipping shipping ships), and those are already slow enough that a substantial part of world trade is by airplane now, because inventory on a container ship is inventory you can't sell yet, or at least can't deliver yet. You could imagine a future where container ships are partly powered by onboard sails and partly powered by giant lightweight solar farms towed behind them on hydrofoils, but I don't think we're going to see container ships powered by lithium-ion batteries. Aluminum-air, maybe.
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.
_aavaa_ · · focus · HN ↗
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 · · focus · HN ↗
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_ · · focus · HN ↗
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 · · focus · HN ↗
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_ · · focus · HN ↗
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 · · focus · HN ↗
1. Sad that he died from cancer
2. Noticed he compared primary energy and felt stupid for missing that
kragen · · focus · HN ↗
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 · · focus · HN ↗
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).
mbgerring · · focus · HN ↗
Thankfully, energy storage is being deployed worldwide, so this is a moot point, and renewables can and will replace fossil fuel electricity generation.
kragen · · focus · HN ↗
DangitBobby · · focus · HN ↗
kragen · · focus · HN ↗
Ships, we'll see. Most shipping ships are container ships (as opposed to, say, tankers, cruse ships, or ship shipping ships shipping shipping ships), and those are already slow enough that a substantial part of world trade is by airplane now, because inventory on a container ship is inventory you can't sell yet, or at least can't deliver yet. You could imagine a future where container ships are partly powered by onboard sails and partly powered by giant lightweight solar farms towed behind them on hydrofoils, but I don't think we're going to see container ships powered by lithium-ion batteries. Aluminum-air, maybe.
kragen · · focus · HN ↗
(Yes, I know that makes me sound like an LLM.)