Changes

35 chapters revised so far, 113 individual updates. Each excerpt below shows a change in context — ~~struck-through~~ is MacKay's 2008 original, highlighted is ours, dated and sourced. Click a chapter heading to read it in full, including the citation for every change in that chapter's own "Updates" section.

New here? Start with the synthesis — what's really changed since 2008 and what it means for the book's conclusions. This page is the detail underneath it.

This page is generated from the chapter markdown by scripts/changes-digest.mjs — nothing here is hand-maintained, so it stays accurate as more chapters are revised.

The author — 4 changes
1 Motivations — 1 change
2 The balance sheet — 1 change
3 Cars — 2 changes
4 Wind — 2 changes
6 Solar — 11 changes
9 Light — 2 changes
10 Offshore wind — 4 changes
11 Gadgets — 1 change
12 Wave — 1 change
13 Food and farming — 2 changes
14 Tide — 1 change
16 Geothermal — 1 change
17 Public services — 2 changes
18 Can we live on renewables? — 2 changes
19 Every BIG helps — 1 change
20 Better transport — 2 changes
21 Smarter heating — 1 change
23 Sustainable fossil fuels? — 10 changes
24 Nuclear? — 5 changes
25 Living on other countries’ renewables? — 3 changes
26 Fluctuations and storage — 2 changes
27 Five energy plans for Britain — 31 changes
28 Putting costs in perspective — 1 change
29 What to do now — 2 changes
30 Energy plans for Europe, America, and the World — 4 changes
31 The last thing we should talk about — 2 changes
32 Saying yes — 1 change
A Cars II — 2 changes
B Wind II — 2 changes
D Solar II — 1 change
E Heating II — 2 changes
F Waves II — 2 changes
I Quick reference — 1 change
Preface — 1 change

The author

…— title: "The author" — # The author Sustainable Energy – without the hot air David JC MacKay ![](/assets/author.jpg) The author, July 2008. Photo by David Stern. ## About the author David MacKay ~~is a Professor~~ was a Professor [^u1] in the Department of Physics at the University of Cambridge. He studied Natural Sciences at Cambridge and then obtained his PhD in Computation and Neural Systems at the California Institute of Technology. He retur…

…known for his research in machine learning, information theory, and communication systems, including the invention of Dasher, a software interface that enables efficient communication in any language with any muscle. He ~~has taught~~ taught Physics in Cambridge since 1995. Since 2005, he has devoted devoted much of his time to public teaching abo…

…ation in any language with any muscle. He has taught taught Physics in Cambridge since 1995. Since 2005, he ~~has devoted~~ devoted much of his time to public teaching about energy. He is a member of , including a term (2009–2014, after this boo…

…in Cambridge since 1995. Since 2005, he has devoted devoted much of his time to public teaching about energy ~~. He is a member of~~ , including a term (2009–2014, after this book's original publication) as Chief Scientific Advisor to the UK Department of Energy and Climate Change. He was a member of the World Economic Forum Global Agenda Council on Climate Change. ## Updates, 2026 [^u1]: David MacKay's death.…

1 Motivations

…ome countries, including Britain, have committed to at least a 60% reduction in greenhouse-gas emissions by 2050*. Indeed, as I write, Britain’s commitment is being increased to an 80% reduction relative to 1990 levels. Updated, 2026: it went further still — in 2019 the UK amended the Climate Change Act to a 100% ("net zero") reduction target by 2050, the world's first major economy to set one in law. [^u1] [^19]: Figure 1.8. In the lower scenario, the chance that the temperature rise will exceed 2°C is estimated to be 9–26%; the cumulative carbon emissions from 2007 onwards are 309 GtC; CO2 concentrati…

2 The balance sheet

…nal units that everyone can relate to. The unit of energy I have chosen is the kilowatt-hour (kWh). This quantity is called "one unit" on electricity bills, and it costs a domestic user about 10p in the UK in 2008. Updated, 2026: UK domestic electricity now costs roughly 26p per unit, about two and a half times the 2008 price, mainly from the 2021–22 energy crisis — see [^u1]. As we’ll see, most individual daily choices involve amounts of energy equal to small numbers of kilowatt-hours. When we discuss powers (rates at which we use or produce energy), the main unit will be the kilowatt-h…

3 Cars

…n. I’ve displayed this estimate in the left-hand stack in figure 3.3. The red box’s height represents 40 kWh per day per person. This is the estimate for a typical car-driver driving a typical car today — meaning 2008. By the mid-2020s "today" looks different: new-car fuel economy has improved and, more consequentially, over a fifth of new cars sold worldwide in 2024 were electric — not a speculative future technology any more, but a mainstream one. The 40 kWh/d figure above is the 2008 petrol-car baseline this chapter is built on; it is deliberately left as MacKay wrote it, since chapter A's cartoon theory of a car's energy use, not this headline number, is the thing worth re-deriving for an EV — see chapter A's updates. [^u1] Later chapters will discuss the average consumption of all the people in Britain, taking into account the fact that not everyone drives. We’ll also discuss in Part II what the consumption could be, with the he…

…fficient auto company in America," records that its fleet of new cars sold in 2005 has an average top-level fuel economy of 35 miles per UK gallon [[28abpm](http://tinyurl.com/28abpm)\]. Updated, 2026: average new-car fuel economy has since risen further, and by 2024 over 20% of new cars sold worldwide were electric (0 mpg-equivalent fuel burn) — see [^u1]. ![](/assets/figure24.gif) [^3]: Let’s guess a density of 0.8 kg per litre. Petrol’s density is 0.737. Diesel’s is 0.820–0.950 [[nmn4l](http://tinyurl.com/nmn4l)\]. [^4]: *… the ac…

4 Wind

…e as our huge consumption. We’ll come to offshore wind later. I should emphasize how generous an assumption I’m making. Let’s compare this estimate of British wind potential with current installed wind power worldwide. The windmills that would be required to provide the UK with 20 kWh/d per person amount to 50 times the entire wind hardware of Denmark; 7 times all the wind farms of Germany; and double the entire fleet of all wind turbines in the world. World wind capacity has grown roughly 15-fold since this was written: the 150 GW this scenario needs is now well under, not double, the world's installed wind fleet, and is comparable to a single year or two of current global build. [^2] [^u1] Please don’t misunderstand me. Am I saying that we shouldn’t bother building wind farms? Not at all. I’m simply trying to convey a helpful fact, namely that if we want wind power to truly make a difference,…

…ge power to the peak power is called the "load factor" or "capacity factor," and it varies from site to site, and with the choice of hardware plopped on the site; a typical factor for a good site with modern turbines is ~~30%~~ 35-45% . [^u2] If we assume Whitelee has a load factor of 33% then the average power production per unit land area is 2 W/m2 – exactly the same as the power density we assumed above. ![](/…

6 Solar

…f thermal panels can deliver (on average) about 13 kWh per day of thermal energy. ## Solar photovoltaic Photovoltaic (PV) panels convert sunlight into electricity. [^5] Typical solar panels have an efficiency of about ~~10%~~ 20% ; expensive ones perform at 20% 24%. [^6] [^u1] (Fundamental physical laws limit the efficiency of photovolt…

…into electricity. [^5] Typical solar panels have an efficiency of about 10% 20%; expensive ones perform at ~~20%~~ 24% . [^6] [^u1] (Fundamental physical laws limit the efficiency of photovoltaic systems to at best 60% with perfect concentrating mirrors or lenses, and 45% without concentration. A mass-produced device with efficiency grea…

…best 60% with perfect concentrating mirrors or lenses, and 45% without concentration. A mass-produced device with efficiency greater than 30% would be quite remarkable. [^7] ) The average power delivered by south-facing ~~20%-efficient~~ 24%-efficient photovoltaic panels in Britain would be 20%× 110 W/m2 = 22 W/m2. <ins style="color:#a3540f;background:#fbeee0;padding:0 3px;border-radius:2px;font-weight:600;…

…verage power delivered by south-facing 20%-efficient 24%-efficient photovoltaic panels in Britain would be ~~20%× 110 W/m2 = 22 W/m2.~~ 24% × 110 W/m2 ≈ 26 W/m2. Figure 6.5 shows data to back up this number. Let’s give every person 10 m2 of expensive (20%-efficient) <ins style="color:#a3540f;background:#fbeee0;padding:0 3px;border-radius:2px;font-weight:60…

…3540f;background:#fbeee0;padding:0 3px;border-radius:2px;font-weight:600;">24% × 110 W/m2 ≈ 26 W/m2. Figure 6.5 shows data to back up this number. Let’s give every person 10 m2 of ~~expensive (20%-efficient)~~ today's mainstream (24%-efficient) solar panels and cover all south-facing roofs. These will deliver 5 kWh per day per person. 6.3 kWh per day per…

…efficient) today's mainstream (24%-efficient) solar panels and cover all south-facing roofs. These will deliver ~~5 kWh per day per person.~~ 6.3 kWh per day per person. ![](/assets/figure38.gif) Figure 6.5. Solar photovoltaics: data from a 25-m2 array in Cambridgeshire in 2006. The peak power delivered by this array is about 4 kW. The aver…

…lar thermal panels of the last section. So we have to choose whether to have the photovoltaic contribution or the solar hot water contribution. But I’ll just plop both these on the production stack anyway. Incidentally, the present cost of installing such photovoltaic panels is about four times the cost of installing solar thermal panels, but they deliver only half as much energy, albeit high-grade energy (electricity). So I’d advise a family thinking of going solar to investigate the solar thermal option first. PV module costs fell roughly 90% between 2008 and the mid-2020s, and installing photovoltaics is now typically no more expensive than solar thermal for the electricity delivered — the cost gap this advice was based on has closed, so the choice between the two now turns more on what you need, heat or electricity, than on price. [^u2] The smartest solution, at least in sunny countries, is to make combined systems that deliver both electricity and hot water from a single installation. This is the approach pioneered by Heliodynamics, [^9] who red…

…of solar panels co-exist with the army of windmills we imagined in Chapter 4? Yes, no problem: windmills cast little shadow, and ground-level solar panels have negligible effect on the wind. How audacious is this plan? ~~The solar power capacity required to deliver this 50 kWh per day per person in the UK is more than 100 times all the photovoltaics in the whole world.~~ This is 1250 GW of capacity — comparable to less than a year of the world's current solar build rate. Global installed solar passed 1873 GW by the end of 2024, not the 10 GW it stood at when this book was written. [^11] [^u4] So should I include the PV farm in my sustainable production stack? I’m in two minds. At the start of this book I said I wanted to explore what the laws of physics say about the limits of sustainable energy,…

…. On those grounds, I should certainly go ahead, industrialize the countryside, and push the PV farm onto the stack. At the same time, I want to help people figure out what we should be doing between now and 2050. And ~~today, electricity from solar farms would be four times as expensive as the market rate.~~ by the mid-2020s, unsubsidised utility-scale solar had become some of the cheapest new electricity in the world — cheaper than new gas, and often cheaper than continuing to run existing fossil plants. [^u3] So I feel a bit irresponsible as I include this estimate in the sustainable production stack in figure 6.9 – paving 5% of the UK with solar panels seems beyond the bounds of plausibility in so many ways. [^12] If…

…er so little power, I think they are scarcely worth talking about. ## Updates, 2026 The chapter above carries five inline updates (marked struck-through / highlighted ) to figures that have moved since 2008. MacKay's original text is untouched elsewhere; these are additions, not silent corrections. Sourced from docs/audit.yaml. [^u1]: *P…

…asted 20 years without further expenditure, the wholesale cost of the electricity would be €0.25 per kWh. Further reading: David Carlson, BP solar [[2ahecp](http://tinyurl.com/2ahecp)\]. Updated, 2026: utility-scale solar's wholesale cost is now roughly €0.05 per kWh, not €0.25 — see [^u3]. [^13]: People in Britain throw away about 300 g of food per day. Source: Ventour (2008). [^14]: Figure 6.10. In the USA, Miscanthus grown without nitrogen fertilizer yields about 24 t/ha/y of dry matter. In Brit…

9 Light

…ing a 12-year period, you have this choice (figure 9.3): buy 15 incandescent bulbs and 1500 kWh of electricity (which costs roughly £150); or buy one low-energy bulb and 300 kWh of electricity (which costs roughly £30). Updated, 2026: this choice no longer exists in the UK/EU — incandescent bulbs were phased out by regulation, and LEDs have since superseded CFLs too — see [^u1]. #### Should I wait until the old bulb dies before replacing it? It feels like a waste, doesn’t it? Someone put resources into making the old incandescent lightbulb; shouldn’t we cash in that original investment by usi…

…itle">ynjzej](http://tinyurl.com/ynjzej)\]. I expect that within another couple of years, the best advice, from the point of view of both energy efficiency and avoiding mercury pollution, will be to use LED bulbs. Updated, 2026: this prediction came true — see [^u1]. ### Mythconceptions #### "There is no point in my switching to energy-saving lights. The "wasted" energy they put out heats my home, so it’s not wasted." This myth is addressed in Chapter 11. | Bulb type | effic…

10 Offshore wind

…ow* offshore wind (depth less than 25– 30 m), while roughly twice as costly as land-based wind, is economically feasible, given modest subsidy; [^2] and deep offshore wind is at present not economically feasible. [^3] ~~As of 2008, there’s just one deep offshore windfarm in UK waters, an experimental prototype sending all its electricity to a nearby oilrig called Beatrice.~~ Deep and floating offshore wind became a substantial industry over the following decade: global offshore wind capacity reached roughly 83 GW by the end of 2024, much of it in UK waters. [^u1] ## Shallow offshore Within British territorial waters, the shallow area is about 40 000 km2, most of it off the coast of England and Wales. This area is about two Waleses. The average power available…

…] that it would permit the creation of 33 GW of offshore wind capacity (which would deliver on average 10 GW to the UK, or 4.4 kWh per day per person), a plan branded "pie in the sky" [^10] by some in the wind industry. That 33 GW ambition turned out to be an underestimate, not pie in the sky: UK operational offshore wind capacity reached roughly 15 GW by the end of 2024, with a government target of 50 GW (including floating wind) by 2030. [^u2] Let’s run with a round figure of 4 kWh per day per person. This is one quarter of my shallow 16 kWh per day per person. To obtain this average power requires roughly 10 000 "3 MW" wind turbines like those in figur…

…92 per MWh. In the same document, estimates for other renewables (medium levelized costs in 2010) are as follows. Onshore wind: £65–89/MWh; co-firing of biomass: £53/MWh; large-scale hydro: £63/MWh; sewage gas: £38/MWh; ~~solar PV: £571/MWh;~~ solar PV had collapsed to roughly £48/MWh by 2024, cheaper than any of these; [^u3] wave: £196/MWh; tide: £177/MWh. Offshore wind itself fell to roughly £73–91/MWh by the 2024 UK CfD auction. [^u3…

…l> solar PV had collapsed to roughly £48/MWh by 2024, cheaper than any of these; [^u3] wave: £196/MWh; tide: £177/MWh. Offshore wind itself fell to roughly £73–91/MWh by the 2024 UK CfD auction. [^u3] "Dale Vince, chief executive of green energy provider Ecotricity, which is engaged in building onshore wind farms, said that he supported the Government’s [offshore wind] plans, but only if they are not to the det…

11 Gadgets

…ering the hidden tendrils of the information age According to Jonathan Koomey (2007), the computer-servers in US datacentres and their associated plumbing (air conditioners, backup power systems, and so forth) consumed ~~0.4 kWh per day per person – just over 1% of US electricity consumption.~~ 0.4 kWh per day per person in 2005 – just over 1% of US electricity consumption. By 2024, that had grown to roughly 1.5 kWh per day per person – just over 4% of US electricity – with AI workloads now a major and fast-growing share of the increase. [^u1] That’s the consumption figure for 2005, which, by the way, is twice as big as the consumption in 2000, because the number of servers grew from 5.6 million to 10 million. Gadget Power consumption (W) on and acti…

12 Wave

…of the Pelamis ("designed with survival as the key objective before power capture efficiency") predict that a two-kilometre long wave-farm consisting of 40 of their sea-snakes would deliver 6 kW per metre of wave-farm. Updated, 2026: Pelamis Wave Power went into administration in 2014 and its devices were decommissioned — see [^u1]. Using this number in the previous calculation, the power delivered by 500 kilometres of wave-farm is reduced to 1.2 kWh per day per person. While wave power may be useful for small communities…

13 Food and farming

…queue of animals lining up to be eaten by the human. ### The energy cost of eating meat Let’s say an enthusiastic meat-eater eats about half a pound a day (227 g). (This is the average meat consumption of Americans.) Updated, 2026: American meat consumption has since risen further, to roughly 279 g/day (224.6 lb/year) — see [^u1]. To work out the power required to maintain the meat-eater’s animals as they mature and wait for the chop, we need to know for how long the animals are around, consuming energy. Chicken, pork, or beef? Chicken, sir? Eve…

…of meat, made up of equal quantities of chicken, pork, and beef*. This is close to the average meat consumption in America, which is 251 g per day – made up of 108 g chicken, 81 g beef, and 62 g pork (MacDonald, 2008). Updated, 2026: risen further since — see [^u1]. [^4]: Chicken. A full-grown (20-week old) layer weighs 1.5 or 1.6 kg. Its feed has an energy content of 2850 kcal per kg, which is 3.3 kWh per kg, and its feed consumption rises to 340 g per week when 6 weeks old, an…

14 Tide

…windmill, or "tidal-stream" generator, to be connected to the grid was a "300 kW" turbine, installed in 2003 near the northerly city of Hammerfest, Norway. Detailed power production results have not been published, and ~~no-one has yet built a tide farm with more than one turbine,~~ that changed within a decade: MeyGen, in Scotland's Pentland Firth, is now the world's largest tidal stream array, with 6 MW operating since 2024 and up to 398 MW consented for future phases — it had delivered over 68 GWh to the grid by September 2024, nearly two-thirds of all tidal-stream power generated globally to date. [^u1] so we’re going to have to rely on physics and guesswork to predict how much power tide farms could produce. Assuming that the rules for laying out a sensible tide farm are similar to those for wind farms, and that…

16 Geothermal

…Geothermal power in Iceland. Average geothermal electricity generation in Iceland (population, 300 000) in 2006 was 300 MW (24 kWh/d per person). More than half of Iceland’s electricity is used for aluminium production. Updated, 2026: Iceland's population has since grown to about 390,000 and its geothermal generating capacity to roughly 786 MW — see [^u1]. Photo by Gretar Ívarsson. ## Geothermal power that would be sustainable forever First imagine using geothermal energy sustainably by sticking down straws to an appropriate depth, and sucking gently. Sucking at such…

17 Public services

…went to defence was £33 billion/£587 billion = 6%. [^1] If we include the UK’s spending on counter-terrorism and intelligence (£2.5 billion per year and rising), the total for defensive activities comes to £36 billion. Updated, 2026: both figures have roughly doubled in nominal terms since — defence spending was about £63.6bn against total government spending of about £1.22 trillion in 2024/25 — leaving the ratio close to where it was, about 5%, see [^u1]. As a crude estimate we might guess that 6% of this £36 billion is spent on energy at a cost of 2.7p per kWh. (6% is the fraction of GDP that is spent on energy, and 2.7p is the average price of energy.) That works out…

…million, a megaton bomb makes an energy donation of 1200 kWh per person, equivalent to 120 litres of petrol per person. The total energy of the USA’s nuclear arsenal today is 2400 megatons, contained in 10 000 warheads. Updated, 2026: the US stockpile has since fallen to roughly 3,700 warheads, under New START and earlier post-Cold War arms reductions — see [^u1]. In the good old days when folks really took defence seriously, the arsenal’s energy was 20 000 megatons. These bombs, if used, would have delivered an energy of about 100 000 kWh per American. That’s equivalent to 7 kWh…

18 Can we live on renewables?

…ich means the energy contained in raw fuels, plus wind and hydroelectricity) is about 125 kWh per day per person. The UK average is also 125 kWh per day per person. [^1] Both figures have fallen a great deal since 2008: the UK's per-capita energy consumption was about 68 kWh/d in 2023, and a recent EU-wide estimate puts the European figure at roughly 90 kWh/d — driven by efficiency gains and deindustrialisation, not by people living smaller lives in any single visible way. [^u1] These official averages do not include two energy flows. First, the "embedded energy" in imported stuff (the energy expended in making the stuff) is not included at all. We estimated in Chapter 15 that the embe…

…that we want to get off fossil fuels, for one or more of the reasons listed in Chapter 1 – climate change, security of supply, and so forth. Figure 18.9 shows how much power we currently get from renewables and nuclear. ~~They amount to just 4% of our total power consumption.~~ That 4% is now well out of date, at least for electricity specifically: renewables alone generated just over half of UK electricity for the first time in 2024 (50.8%), with nuclear adding a further 14%, so low-carbon sources together supplied nearly two-thirds of UK electricity. This chapter's "4%" was always a total-energy figure, not an electricity-only one, and total-energy decarbonisation (heating and transport still lean heavily on fossil fuels) remains far behind electricity's progress — the book's broader pessimism about the pace of change outside the power sector still holds even as this specific number has moved a long way. [^u2] The two conclusions we can draw from Part I are: 1. To make a difference, renewable facilities have to be country-sized. For any renewable facility to make a contribution comparable to our current consumpt…

19 Every BIG helps

…nsumption is also 40 kWh per day per person (currently all supplied by fossil fuels); and the electricity consumption is 18 kWh(e) per day per person; the electricity is currently almost all generated from fossil fuels; Updated, 2026: no longer true — see [^u1]. the conversion of fossil-fuel energy to electricity is 40% efficient, so supplying 18 kWh(e) of electricity in today’s cartoon-Britain requires a fossil-fuel input of 45 kWh per day per person. This simplification ignor…

20 Better transport

…s – they’re listed in this chapter’s end-notes [^16] – and they seem to be consistent with this summary: electric vehicles can deliver transport at an energy cost of roughly 15 kWh per 100 km. Updated, 2026: this held up well — production EVs today typically use 15–20 kWh per 100 km, in the same range MacKay estimated from early prototypes — see [^u1]. That’s five times better than our baseline fossil-car, and significantly better than any hybrid cars. Hurray! To achieve economical transport, we don’t have to huddle together in public transport – we can still hurtle…

…battery is 3% lithium. [^21] If we assume each vehicle has a 200 kg battery, then we need 6 kg of lithium per vehicle. So the estimated reserves in ore deposits are enough to make the batteries for 1.6 billion vehicles. Updated, 2026: identified world lithium reserves have since roughly tripled, to about 28 million tons (with broader identified resources around 105 million tons) — see [^u1]. That’s more than the number of cars in the world today (roughly 1 billion) – but not much more, so the amount of lithium may be a concern, especially when we take into account the competing ambitions of the nuclear fusi…

21 Smarter heating

…has greatly improved the performance of air-conditioners; thanks to this drive, there are now air-source heat pumps with a coefficient of performance of 4.9; these heat pumps can make hot water as well as hot air. [^5] Updated, 2026: a CoP of 4.9 is no longer exceptional — see [^u1]. Another objection to heat pumps is "oh, we can’t approve of people fitting efficient air-source heaters, because they might use them for air-conditioning in the summer." Come on – I hate gratuitous air-conditioning as…

23 Sustainable fossil fuels?

…own renewables looks very challenging ([figure 18.7](../Text/chap18.xhtml#fig7)). It’s time to discuss non-renewable options for power production. Take the known reserves of fossil fuels, which are overwhelmingly coal: ~~1600 Gt of coal.~~ roughly 1074 Gt of coal, down about a third from the 1600 Gt this chapter used — reserve estimates were revised down substantially in the years after 2008 (partly reclassification, e.g. Germany's ~99% cut in 2011). [^u1] Share them equally between six billion people, and burn them "sustainably." What do we mean if we talk about using up a finite resource "sustainably"? Here’s the arbitrary definition I’ll use: the burn-rate is "su…

…e "sustainably"? Here’s the arbitrary definition I’ll use: the burn-rate is "sustainable" if the resources would last 1000 years. [^1] A ton of coal delivers 8000 kWh of chemical energy, [^2] so ~~1600~~ 1074 Gt of coal shared between 6 billion people over 1000 years works out to a power of 6 kWh per day per person. <ins style="color:#a3540f;background:#fbeee0;padding:0 3px;border-radius…

…nergy, [^2] so 1600 1074 Gt of coal shared between 6 billion people over 1000 years works out to a power of ~~6 kWh per day per person.~~ 4.0 kWh per day per person, updating the working through with the reserve figure above. A standard coal power station would turn this chemical power into electricity with an efficiency of about 37% – that means about 2.2 kWh(e) per day per person. <ins style="color:#a3…

…kWh per day per person, updating the working through with the reserve figure above. A standard coal power station would turn this chemical power into electricity with an efficiency of about 37% – that means about ~~2.2 kWh(e) per day per person.~~ 1.5 kWh(e) per day per person. If we care about the climate, however, then presumably we would not use a standard power station. Rather, we would go for "clean coal," also known as "coal with carbon capture and storage" [^3] – an as-yet scarcely…

…er person. If we care about the climate, however, then presumably we would not use a standard power station. Rather, we would go for "clean coal," also known as "coal with carbon capture and storage" [^3] – ~~an as-yet scarcely-implemented technology~~ now a substantially more mature technology, with 65 commercial CCS facilities operating worldwide in 2024 [^u2] that sucks most of the carbon dioxide out of the chimney-flue gases and then shoves it down a hole in the ground. Cleaning up power station emissions in this way has a significant energy cost – it would reduce the…

…the ground. Cleaning up power station emissions in this way has a significant energy cost – it would reduce the delivered electricity by about 25%. So a "sustainable" use of known coal reserves would deliver only about ~~1.6 kWh(e) per day per person.~~ 1.1 kWh(e) per day per person, on today's reserve estimate. We can compare this "sustainable" coal-burning rate – 1.6 Gt per year 1.1 Gt per year, on the updated reserve fi…

…0f;background:#fbeee0;padding:0 3px;border-radius:2px;font-weight:600;">1.1 kWh(e) per day per person, on today's reserve estimate. We can compare this "sustainable" coal-burning rate – ~~1.6 Gt per year~~ 1.1 Gt per year, on the updated reserve figure – with the current global rate of coal consumption: 6.3 Gt per year, and rising. global coal consumption, which k…

…his "sustainable" coal-burning rate – 1.6 Gt per year 1.1 Gt per year, on the updated reserve figure – with ~~the current global rate of coal consumption: 6.3 Gt per year, and rising.~~ global coal consumption, which kept rising to a record 8.5 billion tonnes in 2023 — though the IEA subsequently projected demand to plateau and start declining from 2024. [^u3] What about the UK alone? Britain is estimated to have 7 Gt of coal left. [^4] OK, if we share 7 Gt between 60 million people, we get 100 tons per person. If we want a 1000-year solution, this corresponds to <span…

…ution, this corresponds to 2.5 kWh per day per person. In a power station performing carbon capture and storage, this sustainable approach to UK coal would yield 0.7 kWh(e) per day per person. This whole calculation is now moot in a different way: UK coal power ended entirely in 2024. The last deep coal mine closed in 2015, and the UK closed its last coal-fired power station, Ratcliffe-on-Soar, that September — the first G7 country to eliminate coal from its electricity supply. [^u4] ![](/assets/figure425.gif) Figure 23.3. A caterpillar grazing on old leaves. Photo by Peter Gunn. Our conclusion is clear: > Clean coal is only a stop-gap. If we do develop…

…ore combustion. See Metz et al. (2005). The first prototype coal plant with CCS was opened on 9th September 2008 by the Swedish company Vattenfall [[5kpjk8](http://tinyurl.com/5kpjk8)\]. Updated, 2026: see [^u2] for how far past the prototype stage CCS has moved. [^4]: UK coal. In December 2005, the reserves and resources at existing mines were estimated to be 350 million tons. In November 2005, potential opencast reserves were estimated to be 620 million tons; and the underg…

24 Nuclear?

…s of 1 Jan 2005. These are the estimated resources in areas where exploration has taken place. There’s also 1.3 million tons of depleted uranium sitting around in stockpiles, a by-product of previous uranium activities. Updated, 2026: the world-total conventional-reserves figure of 4.7 million tons has since been reassessed upward substantially, to about 7.9 million tons as of 1 Jan 2023, through further exploration. [^u1] ![](/assets/figure194.gif) Figure 24.3. Workers push uranium slugs into the X-10 Graphite Reactor. Could nuclear power be "sustainable"? Leaving aside for a moment the usual qu…

…e-through reactors, this would deliver power at a rate of 2.8 million GW-years / 1600 years = 1750 GW, which, shared between 6 billion people, is 7 kWh per day per person. (There’s currently ~~369 GW of nuclear reactors~~ roughly 365 GW of nuclear reactors as of 2023, generating an all-time-record 2,667 TWh in 2024 [^u2], so this figure corresponds to a 4-fold increase in nuclear power over today’s levels.) I conclude that ocean extraction of uranium would turn today’s once-through reactors into a "sustainable" option – assuming t…

…h death rates below 0.2 per GWy. [^15] Hydroelectricity is the best of all according to the EU study, but comes out worst in the Paul Scherrer Institute’s study, because the latter surveyed a different set of countries. This chapter was written before the March 2011 Fukushima Daiichi accident, the second-worst in nuclear power's history. It doesn't overturn the comparison: no deaths have been directly attributed to radiation exposure, and modern estimates still put nuclear's death rate at around 0.03 deaths per TWh, among the lowest of any source — but it belongs in this discussion, not omitted from it. [^u4] ### Inherently safe nuclear power Spurred on by worries about nuclear accidents, engineers have devised many new reactors with improved safety features. The GT-MHR power plant, for example, is claimed to be…

…it belongs in this discussion, not omitted from it. [^u4] ### Inherently safe nuclear power Spurred on by worries about nuclear accidents, engineers have devised many new reactors with improved safety features. ~~The GT-MHR power plant, for example, is claimed to be inherently safe; and, moreover it has a higher efficiency of conversion of heat to electricity than conventional nuclear plants~~ The GT-MHR project cited here as the leading example was effectively shelved; a different generation of small modular and Gen-IV reactor designs (NuScale, Rolls-Royce SMR, various molten-salt and high-temperature gas-cooled projects) leads the field today [[gt-mhr.ga.com](http://gt-mhr.ga.com/)\]. [^u5] ![](/assets/figure200.gif) Figure 24.12. Chernobyl power plant (top), and the abandoned town of Prypi…

…up budget seems to rise and rise. The latest figure for the total cost of decommissioning is £73 billion. [news.bbc.co.uk/1/hi/uk/7215688.stm](http://news.bbc.co.uk/1/hi/uk/7215688.stm) Updated, 2026: it kept rising — the NDA's discounted best estimate was £124.4 billion in 2023–24 (down from a 2022 peak of ~£149 billion). [^u3] [^11]: The nuclear industry sold everyone in the UK 4 kWh/d for about 25 years. The total generated to 2006 was about 2200 TWh. Source: Stephen Salter’s Energy Review for the Scottish National Party. [^12]: *T…

25 Living on other countries’ renewables?

…ergy Systems. [www.stirlingenergy.com\](http://www.stirlingenergy.com) ![](/assets/figure208.gif) Figure 25.4. Andasol – a "100MW" solar power station ~~under construction~~ (completed and operating since 2011) in Spain. Excess thermal energy produced during the day will be stored in liquid salt tanks for up to seven hours, allowing a continuous and stable supply of electric power to the grid. The power station is predicted to…

…’s, and its area is 7 times bigger. Other large, area-rich, countries are Kazakhstan, Saudi Arabia, Algeria, and Sudan. In all these countries, I think the most promising renewable is solar power ~~, concentrating solar power in particular, which uses mirrors or lenses to focus sunlight.~~ — but by 2026 it's flat photovoltaic panels, not the concentrating solar power (mirrors or lenses focusing sunlight) discussed through the rest of this chapter, that turned out to dominate. See the note after this chapter's "mirrors will still be cheaper" prediction, below. [^u2] Concentrating solar power stations come in several flavours, arranging their moving mirrors in various geometries, and putting various power conversion technologies at the focus – Stirling engines, pressurized wat…

…have bigger power density, why don’t you describe covering the Sahara desert with them? Because I am trying to discuss practical options for large-scale sustainable power production for Europe and North Africa by 2050. ~~My guess is that by 2050, mirrors will still be cheaper than photovoltaic panels, so concentrating solar power is the technology on which we should focus.~~ That guess has already been falsified, decades early: flat photovoltaic panel costs fell roughly 80–90% between 2008 and the mid-2020s (see chapter 6's and chapter 30's updates), while concentrating solar power's costs fell much less, and PV rather than CSP now dominates solar deployment worldwide, including in desert regions. The geometry in this chapter — how much desert area a given power output needs — works the same way for PV as for CSP; it's the technology choice, not the arithmetic, that's changed. [^u2] #### What about solar chimneys? ![](/assets/figure210.gif) Figure 25.10. The Manzanares prototype solar chimney. Photos from [solarmillennium.de</spa…

26 Fluctuations and storage

…voir of the Ffestiniog pumped storage scheme in north Wales. Energy stored: 1.3 GWh. Photo by Adrian Pingstone. Britain has four pumped storage facilities, which can store 30 GWh between them (table 26.4, figure 26.6). Updated, 2026: pumped storage is no longer the only serious grid-storage option — see [^u1] for how far grid-scale batteries have come since this chapter was written. They are typically used to store excess electricity at night, then return it during the day, especially at moments of peak demand – a profitable business, as figure 26.5 shows. The Dinorwig power station – an astonishin…

…stops and starts. You can buy supercapacitors with an energy density of 6 Wh/kg. A US company, EEStor, claims to be able to make much better supercapacitors, using barium titanate, with an energy density of 280 Wh/kg. Updated, 2026: EEStor never delivered — see [^u1]. ##### Vanadium flow batteries VRB power systems [^15] have provided a 12 MWh energy storage system for the Sorne Hill wind farm in Ireland, whose current capacity is "32 MW," increasing to "39 MW." (VRB stands for van…

27 Five energy plans for Britain

…"domestic diversity") uses a lot of every possible domestic source of electricity, and depends relatively little on energy supply from other countries. Here’s where plan D gets its 50 kWh/d/p of electricity from. Wind: ~~8 kWh/d/p (20 GW average; 66 GW peak) (plus about 400 GWh of associated pumped storage facilities).~~ 18 kWh/d/p (45 GW average; about 125 GW peak), plus roughly 900 GWh of associated pumped storage, scaled up in proportion to the extra average power. [^u5] Solar PV: 3 kWh/d/p. 9 kWh/d/p. [^u5] Waste incineration: 1.1 kWh/d/p. Hydroelectricity: 0.2 kWh/d/p.…

…dding:0 3px;border-radius:2px;font-weight:600;">18 kWh/d/p (45 GW average; about 125 GW peak), plus roughly 900 GWh of associated pumped storage, scaled up in proportion to the extra average power. [^u5] Solar PV: ~~3 kWh/d/p.~~ 9 kWh/d/p. [^u5] Waste incineration: 1.1 kWh/d/p. Hydroelectricity: 0.2 kWh/d/p. Wave: 2 kWh/d/p. Tide: 3.7 kWh/d/p. Nuclear: 16 kWh/d/p (40 GW). "Clean coal": 16 kWh/d/p (40 GW). <ins style="color:#a3540f;background:#f…

…ackground:#fbeee0;padding:0 3px;border-radius:2px;font-weight:600;">9 kWh/d/p. [^u5] Waste incineration: 1.1 kWh/d/p. Hydroelectricity: 0.2 kWh/d/p. Wave: 2 kWh/d/p. Tide: 3.7 kWh/d/p. Nuclear: 16 kWh/d/p (40 GW). ~~"Clean coal": 16 kWh/d/p (40 GW).~~ "Clean coal" is removed from this plan; its 16 kWh/d/p is folded into wind and solar above (10 to wind, 6 to solar) — see the recomputed paragraphs below. [^u6] ![](/assets/figure229.gif) Figure 27.4. Plan D To get 8 kWh/d/p of wind requires a 30-fold increase in wind power over the installed power in 200…

…into wind and solar above (10 to wind, 6 to solar) — see the recomputed paragraphs below. [^u6] ![](/assets/figure229.gif) Figure 27.4. Plan D To get ~~8 kWh/d/p of wind requires a 30-fold increase in wind power over the installed power in 2008. Britain would have nearly 3 times as much wind hardware as Germany has now.~~ 18 kWh/d/p of wind requires about 125 GW of installed capacity: 45 GW of average power (18 kWh/d/p × 2.5 GW per kWh/d/p, this chapter's population-scaling factor) divided by a modern blended onshore/offshore capacity factor of about 36% — UK offshore averaged 43.6% in 2023, UK onshore averages nearer 28% [^u7] — rather than the 30% this chapter originally assumed. That's about 4.4 times the 28.5 GW actually installed in the UK by 2024, not a 30-fold increase over 2008 [^u1]; and about 1.7 times Germany's current 73 GW wind fleet [^u8], not "nearly 3 times as much… as Germany has now," because Germany's fleet has grown enormously too. [^u1] Installing this much windpower offshore over a period of 10 years would require considerably more than 50 jack-up barges. Getting 3 kWh/d/p from solar photovoltaics requires 6 m2 of 20%efficient p…

…es as much… as Germany has now," because Germany's fleet has grown enormously too. [^u1] Installing this much windpower offshore over a period of 10 years would require considerably more than 50 jack-up barges. ~~Getting 3 kWh/d/p from solar photovoltaics requires 6 m2 of 20%efficient panels per person.~~ Getting 9 kWh/d/p from solar photovoltaics requires about 14 m2 of 24%-efficient panels per person — up from 6 m2 at 20% efficiency, because the higher efficiency (chapter 6's update) doesn't come close to offsetting tripling the target output. [^u9] Most south-facing roofs would have to be completely covered with panels; — and, at 14 m2 per per…

…/sup> at 20% efficiency, because the higher efficiency (chapter 6's update) doesn't come close to offsetting tripling the target output. [^u9] Most south-facing roofs would have to be completely covered with panels ; — and, at 14 m2 per person, roof space alone (about 10 m2 per person, per chapter 6) is no longer enough, so some of this now has to go on the ground; alternatively, it might be more economical, and cause less distress to the League for the Preservation of Old Buildings, to plant many of these panels in the countryside in the traditional Bavarian manner ([figure 6.7](…

…wer comes from 5 GW of tidal stream installations, a 2 GW Severn barrage, and 2.5 GW of tidal lagoons, which can serve as pumped storage systems too. To get 16 kWh/d/p of nuclear power requires 40 GW of nukes, which is ~~a roughly four-fold increase of the 2007 nuclear fleet.~~ now a much bigger jump than that: UK nuclear capacity has fallen since 2008, not grown, as most of the AGR fleet has retired — about 6.5 GW is operational in 2024, down from ~11 GW then, with only the 3.2 GW Hinkley Point C under construction. Reaching 40 GW is roughly a 6-fold increase over today's fleet, and it exceeds even the UK government's own 2050 nuclear ambition of 24 GWe [^u10] — this plan asks for more nuclear than official policy currently contemplates. [^u2] If we produced 16 kWh/d/p of nuclear power, we’d lie between Belgium, Finland, France and Sweden, in terms of per-capita production: Belgium and Finland each produce roughly 12 kWh/d/p; France and Sweden produce 1…

…ear power, we’d lie between Belgium, Finland, France and Sweden, in terms of per-capita production: Belgium and Finland each produce roughly 12 kWh/d/p; France and Sweden produce 19 kWh/d/p and 20 kWh/d/p respectively. To get 16 kWh/d/p of "clean coal" (40 GW), we would have to take the current fleet of coal stations, which deliver about 30 GW, retrofit carbon-capture systems to them, which would reduce their output to 22 GW, then build another 18 GW of new clean-coal stations. "Clean coal" is gone from this plan. The UK closed its last coal-fired power station in September 2024, and large-scale coal CCS never materialised anywhere [^u3]. Its 16 kWh/d/p is reallocated to the two sources whose costs have fallen furthest since 2008 — 10 kWh/d/p to wind, 6 kWh/d/p to solar PV (see the recomputed wind and solar paragraphs above) — a real substitute, not just a footnote saying "find something else." Plans N and L, which also leaned on "clean coal," are recomputed the same way below. [^u6] This level of coal power requires an energy input of about 53 kWh/d/p of coal, which is a little bigger than the total rate at which we currently burn all fossil fuels at power stations, and well above the…

…see the recomputed wind and solar paragraphs above) — a real substitute, not just a footnote saying "find something else." Plans N and L, which also leaned on "clean coal," are recomputed the same way below. [^u6] This level of coal power requires an energy input of about 53 kWh/d/p of coal, which is a little bigger than the total rate at which we currently burn all fossil fuels at power stations, and well above the level we estimated as being "sustainable" in Chapter 23. This rate of consumption of coal is roughly three times the current rate of coal imports (18 kWh/d/p). If we didn’t reopen UK coal mines, this plan would have 32% of UK electricity depending on imported coal. Reopened UK coal mines could deliver an energy input of about 8 kWh/d/p, so either way, the UK would not be self-sufficient for coal. Do any features of this plan strike you as unreasonable or objectionable? If so, perhaps one of the next four plans is more to your liking. ## Producing lots of electricity – plan N Plan N is the "NIMBY" plan, for people who don’t like industrializing the British countryside with renewable energy facilities, and who don’t want new nuclear power stations either. Let’s reveal the plan in stages. ![](/assets/figure230.gif) Figure 27.5. Plan N First, we turn down all the renewable knobs from their very high settings in plan D to: wind: 2 kWh/d/p (5 GW average); solar PV: 0; wave: 0; tide: 1 kWh/d/p. We’ve just lost ourselves 14 kWh/d/p (35 GW nationally) by turning down the renewables. (Don’t misunderstand! Wind is still eight-fold increased over its 2008 levels.) Plan D's renewables are now much higher (18 wind + 9 solar + 2 wave + 3.7 tide = 32.7 kWh/d/p), so turning them down to plan N's minimum (2 + 0 + 0 + 1 = 3 kWh/d/p) loses 29.7 kWh/d/p, or about 74 GW nationally. Wind's 5 GW average here needs only about 14 GW of peak capacity at a modern 36% capacity factor [^u7] — which the UK's actual 2024 fleet, 28.5 GW, already exceeds twice over. Plan N's "minimal" wind ask has, in effect, already been met. [^u1] In the NIMBY plan, we reduce the contribution of nuclear power to 10 kWh/d/p (25 GW) – a reduction by 15 GW compared to plan D, but still a substantial increase over today’s levels. <ins style="color:#…

…as, in effect, already been met. [^u1] In the NIMBY plan, we reduce the contribution of nuclear power to 10 kWh/d/p (25 GW) – a reduction by 15 GW compared to plan D, but still a substantial increase over today’s ~~levels.~~ 6.5 GW — roughly a 4-fold increase, and, unlike plan D's 40 GW, close to the UK government's own 24 GWe 2050 nuclear ambition [^u10] rather than well beyond it. 25 GW of nuclear power could, I think, be squeezed onto the existing nuclear sites, so as to avoid imposing on any new back yards. I left the clean-coal contribution unchanged at 16 kWh/d/p (40 GW). <ins styl…

…K government's own 24 GWe 2050 nuclear ambition [^u10] rather than well beyond it. 25 GW of nuclear power could, I think, be squeezed onto the existing nuclear sites, so as to avoid imposing on any new back yards. ~~I left the clean-coal contribution unchanged at 16 kWh/d/p (40 GW).~~ "Clean coal" is gone here too [^u3]; true to plan N's "not in my back yard" logic, its 16 kWh/d/p goes to more desert import rather than more domestic wind or solar — see below. [^u6] The electricity contributions of hydroelectricity and waste incineration remain the same as in plan D. Where are we going to get an extra 50 GW from? <ins style="color:#a3540f;background:#fbeee0;paddin…

…" logic, its 16 kWh/d/p goes to more desert import rather than more domestic wind or solar — see below. [^u6] The electricity contributions of hydroelectricity and waste incineration remain the same as in plan D. ~~Where are we going to get an extra 50 GW from?~~ Where are we going to get an extra 90 GW from? The NIMBY says, "not in my back yard, but in someone else’s." Thus the NIMBY plan pays other countries for imports of solar power from their deserts to the tune of 20 kWh/d/p (50 GW). <ins style="color:#a3540…

…;">Where are we going to get an extra 90 GW from? The NIMBY says, "not in my back yard, but in someone else’s." Thus the NIMBY plan pays other countries for imports of solar power from their deserts to the tune of ~~20 kWh/d/p (50 GW).~~ 36 kWh/d/p (90 GW) — the original 20 kWh/d/p plus "clean coal"'s reallocated 16. [^u6] This plan requires the creation of five nine blobs each the size of London (44 km in diameter) in th…

…style="color:#a3540f;background:#fbeee0;padding:0 3px;border-radius:2px;font-weight:600;">36 kWh/d/p (90 GW) — the original 20 kWh/d/p plus "clean coal"'s reallocated 16. [^u6] This plan requires the creation of ~~five~~ nine blobs each the size of London (44 km in diameter) in the transmediterranean desert, filled with solar power stations. It also requires power transmission systems to get 50 GW <ins style="color:#a3540f;backgro…

…3px;border-radius:2px;font-weight:600;">nine blobs each the size of London (44 km in diameter) in the transmediterranean desert, filled with solar power stations. It also requires power transmission systems to get ~~50 GW~~ 90 GW of power up to the UK. Today’s high voltage electricity connection from France can deliver only 2 GW of power. So this plan requires a 25-fold increase in the capacity of the electricity connection from the contine…

…solar power stations. It also requires power transmission systems to get 50 GW 90 GW of power up to the UK. ~~Today’s high voltage electricity connection from France can deliver only 2 GW of power. So this plan requires a 25-fold increase in the capacity of the electricity connection from the continent.~~ The UK's total interconnection capacity today, across all its links to France, Norway, Belgium, the Netherlands and Ireland, is about 10.3 GW [^u13] — up substantially from the France-only 2 GW this chapter compares against, and itself evidence the "25-fold increase" framing was already possible. So this plan now requires roughly a 9-fold increase in total UK interconnection capacity, not 25-fold. [^u13] (Or an equivalent power-transport solution – perhaps ships filled with methanol or boron plying their way from desert shores.) Having less wind power, plan N doesn’t need to build in Britain the extra pumped-sto…

…pumped storage systems in the Alps might also be possible. Converting the electricity to a storable fuel such as methanol is another option, though conversions entail losses and thus require more solar power stations. ~~This plan gets 32% + 40% = 72% of the UK’s electricity from other countries.~~ This plan still gets 72% of the UK's electricity from other countries — 36 kWh/d/p of desert import out of 50 — but now all of it is desert solar rather than split between imported coal (32%) and desert solar (40%). Removing "clean coal" moved the source of import dependency, not the total: this plan was never going to be self-sufficient. [^u6] ## Producing lots of electricity – plan L ![](/assets/figure231.gif) Figure 27.6. Plan L Some people say "we don’t want nuclear power!" How can we satisfy them? Perhaps it sh…

…ll those renewables in our back yard, and doing a straight swap of nuclear for desert power. As in plan N, the delivery of desert power requires a large increase in transmission systems between North Africa and Britain; ~~the Europe–UK interconnectors would need to be increased from 2 GW to at least 40 GW.~~ the Europe–UK interconnectors would still need to reach at least 40 GW, but from a starting point of about 10.3 GW of total UK interconnection today [^u13], not the France-only 2 GW this chapter compares against — call it a 4-fold increase, not 20-fold. [^u13] Here’s where plan L gets its 50 kWh/d/p of electricity from. Wind: 8 kWh/d/p (20 GW average) (plus about 400 GWh of associated pumped storage facilities). <ins style="color:#a3540f;background:#fbeee0;…

…of total UK interconnection today [^u13], not the France-only 2 GW this chapter compares against — call it a 4-fold increase, not 20-fold. [^u13] Here’s where plan L gets its 50 kWh/d/p of electricity from. Wind: ~~8 kWh/d/p (20 GW average) (plus about 400 GWh of associated pumped storage facilities).~~ 18 kWh/d/p (45 GW average; about 125 GW peak, plus roughly 900 GWh of storage) — the same recomputed figure as plan D, since plan L keeps all of plan D's renewables. [^u5] Solar PV: 3 kWh/d/p. 9 kWh/d/p, again as plan D. [^u5] Hydroelectricity and waste incineration: 1.3 k…

…er-radius:2px;font-weight:600;">18 kWh/d/p (45 GW average; about 125 GW peak, plus roughly 900 GWh of storage) — the same recomputed figure as plan D, since plan L keeps all of plan D's renewables. [^u5] Solar PV: ~~3 kWh/d/p.~~ 9 kWh/d/p, again as plan D. [^u5] Hydroelectricity and waste incineration: 1.3 kWh/d/p. Wave: 2 kWh/d/p. Tide: 3.7 kWh/d/p. "Clean coal": 16 kWh/d/p (40 GW). <ins style="color:#a3540f;background:#fbeee0;padding:0 3px;border-radius:2px;f…

…style="color:#a3540f;background:#fbeee0;padding:0 3px;border-radius:2px;font-weight:600;">9 kWh/d/p, again as plan D. [^u5] Hydroelectricity and waste incineration: 1.3 kWh/d/p. Wave: 2 kWh/d/p. Tide: 3.7 kWh/d/p. ~~"Clean coal": 16 kWh/d/p (40 GW).~~ "Clean coal" is gone — its 16 kWh/d/p was already folded into plan D's wind and solar figures above, so it doesn't need a separate substitute here. [^u6] Solar power in deserts: 16 kWh/d/p (40 GW average power). This plan imports 64% of UK electricity from other countries. <ins style="color:#a3540f;background:#fbeee0;padding:0 3px;border-radius:2px;font…

…>"Clean coal" is gone — its 16 kWh/d/p was already folded into plan D's wind and solar figures above, so it doesn't need a separate substitute here. [^u6] Solar power in deserts: 16 kWh/d/p (40 GW average power). ~~This plan imports 64% of UK electricity from other countries.~~ This plan now imports 32% of UK electricity from other countries (the 16 kWh/d/p of desert solar out of 50), down from 64% — because the other half of the original import share was "clean coal" run on imported coal, and that's gone rather than replaced by another import. [^u6] I call this "plan L" because it aligns fairly well with the policies of the Liberal – at least it did when I first wrote this chapter in mid-2007; [^3] recently, they’ve been talking about "real energy independen…

…er">Figure 27.7. Plan G I make plan G by starting again from plan D, nudging up the wave contribution by 1 kWh/d/p (by pumping money into wave research and increasing the efficiency of the Pelamis converter) and bumping up wind power fourfold (relative to plan D) to 32 kWh/d/p, so that wind delivers 64% of all the electricity. This is a 120-fold increase of British wind power over today’s levels. Under this plan, world wind power in 2008 is multiplied by 4, with all of the increase being placed on or around the British Isles. pushing wind to 32 kWh/d/p, so that wind still delivers 64% of all the electricity — plan G's own extreme-wind ceiling, no longer "fourfold relative to plan D" since plan D's wind figure has itself moved (18 kWh/d/p) for unrelated reasons (the "clean coal" reallocation). At a modern 36% capacity factor, 32 kWh/d/p (80 GW average) needs about 222 GW of peak wind capacity [^u7] — about 74-fold the roughly 3 GW UK had in 2008, and about 7.8-fold the 28.5 GW actually installed by 2024 [^u1], down from this chapter's original "120-fold increase over today's levels" (which was calculated against the smaller 2008 fleet, using the 30% capacity factor this chapter originally assumed). Britain's wind hardware alone would then total about a fifth of the world's entire installed wind fleet as of 2024 (1131 GW) [^u1] — a very different comparison from "world wind power in 2008 multiplied by 4," now that the world's own fleet has grown roughly 15-fold since 2008. [^u1] The immense dependence of plan G on renewables, especially wind, creates difficulties for our main method of balancing supply and demand, namely adjusting the charging rate of millions of rechargeable batteries f…

…completely replace wind for a national lull lasting 2 days. Roughly 100 of Britain’s major lakes and lochs would be required for the associated pumped-storage systems. Plan G’s electricity breaks down as follows. Wind: ~~32 kWh/d/p (80 GW average)~~ 32 kWh/d/p (80 GW average; about 222 GW peak at a modern 36% capacity factor) [^u7] (plus about 4000 GWh of associated pumped-storage facilities). Solar photovoltaics: 3 kWh/d/p. 3 kWh/d/p, n…

…ing:0 3px;border-radius:2px;font-weight:600;">32 kWh/d/p (80 GW average; about 222 GW peak at a modern 36% capacity factor) [^u7] (plus about 4000 GWh of associated pumped-storage facilities). Solar photovoltaics: ~~3 kWh/d/p.~~ 3 kWh/d/p, needing about 4.7 m2 of 24%-efficient panels per person, down from 6 m2 at the original 20% efficiency. [^u9] Hydroelectricity and waste incineration: 1.3 kWh/d/p. Wave: 3 kWh/d/p. Tide: 3.7 kWh/d/p. Solar power in deserts: 7 kWh/d/p (17 GW). This plan gets 14% of its electricity from other countries. ## Producing lots…

…gnal preventing the emission of CO2, we don’t expect a diverse solution with a wide range of powercosts; rather, we expect an economically optimal solution that delivers the required power at the lowest cost. ~~And when "clean coal" and nuclear go head to head on price, it’s nuclear that wins.~~ "Clean coal" isn’t even in this race any more: it doesn’t exist at UK grid scale, on any price. The real contest by 2026 is between nuclear and wind — and, as the update below shows, wind wins it. [^u3] (Engineers at a UK electricity generator told me that the capital cost of regular dirty coal power stations is £1 billion per GW, about the same as nuclear; but the capital cost of "clean-coal" power, including ca…

…ng transmission lines (though van Voorthuysen (2008) reckons that with Nobel-prize-worthy developments in solar-powered production of chemical fuels, solar power in deserts would be the economic equal of nuclear power). ~~Offshore wind also loses to nuclear, but I’ve assumed that onshore wind costs about the same as nuclear.~~ This cost ranking has reversed: the UK's 2024 offshore wind CfD auction cleared at roughly £73–91/MWh against Hinkley Point C's nuclear price of about £92.50/MWh (escalating well above that in current prices) — both offshore and onshore wind now beat nuclear on price, the opposite of "E"'s founding assumption. [^u4] Here’s where plan E gets its 50 kWh/d/p of electricity from. Wind: 4 kWh/d/p (10 GW average). 24 kWh/d/p (…

…g well above that in current prices) — both offshore and onshore wind now beat nuclear on price, the opposite of "E"'s founding assumption. [^u4] Here’s where plan E gets its 50 kWh/d/p of electricity from. Wind: ~~4 kWh/d/p (10 GW average).~~ 24 kWh/d/p (60 GW average; about 167 GW peak at a modern 36% capacity factor) [^u7] — now the largest single component, because it's the cheapest. Solar PV: 0. 3 kWh/d/p, needing about 4.7 m2 of 24%-efficient panels per person [^u9] — no longer zero…

…fbeee0;padding:0 3px;border-radius:2px;font-weight:600;">24 kWh/d/p (60 GW average; about 167 GW peak at a modern 36% capacity factor) [^u7] — now the largest single component, because it's the cheapest. Solar PV: 0. 3 kWh/d/p, needing about 4.7 m2 of 24%-efficient panels per person [^u9] — no longer zero, since utility solar is now competitive too. Hydroelectricity and waste incineration: 1.3 kWh/d/p. Wave: 0. Tide: 0.7 kWh/d/p. And nuclear: 44 kWh/d/p (110 GW). <ins style="color:#a3540f;background:#fbeee0;padding:0 3px;border-radius:2px;font-weight:600…

…7 m2 of 24%-efficient panels per person [^u9] — no longer zero, since utility solar is now competitive too. Hydroelectricity and waste incineration: 1.3 kWh/d/p. Wave: 0. Tide: 0.7 kWh/d/p. And nuclear: ~~44 kWh/d/p (110 GW).~~ 21 kWh/d/p (52.5 GW) — cut by more than half, but not to zero: pushing wind much past 24 kWh/d/p starts to run into the storage and balancing costs plan G has to build extensively for, so some firm nuclear capacity remains part of a cost-optimal mix even though nuclear now loses on a simple £/MWh comparison. This is a judgement call about the economics of intermittency, not a sourced figure the way the wind/nuclear price comparison is [^u4] — treat it as illustrative, the same spirit as MacKay's own original "I've assumed." [^u4] This plan has a ten-fold increase in our nuclear power over 2007 levels. Britain would have 110 GW, which is roughly double France’s nuclear fleet. <ins style="color:#a3540f;background:#fbeee0;padding:…

…gement call about the economics of intermittency, not a sourced figure the way the wind/nuclear price comparison is [^u4] — treat it as illustrative, the same spirit as MacKay's own original "I've assumed." [^u4] ~~This plan has a ten-fold increase in our nuclear power over 2007 levels. Britain would have 110 GW, which is roughly double France’s nuclear fleet.~~ This plan now has roughly an 8-fold increase in UK nuclear power over 2024's 6.5 GW fleet (down from a ten-fold increase over the 2007 fleet), and Britain's 52.5 GW would be a little under France's own current nuclear capacity rather than double it. [^u2] I included a little tidal power because I believe a well-designed tidal lagoon facility can compete with nuclear power. In this plan, Britain has no energy imports (except for the uranium, which, as we said befor…

28 Putting costs in perspective

…on that this plan assumed; or that liquid fuels must be created in some other way. ## Cost of switching from fossil fuels to renewables Every wind farm costs a few million pounds to build and delivers a few megawatts. As a very rough ballpark figure in 2008, installing one watt of capacity costs one pound; one kilowatt costs 1000 pounds; a megawatt of wind costs a million; a gigawatt of nuclear costs a billion or perhaps two. Other renewables are more expensive. That "one pound per watt" ballpark has moved in opposite directions for renewables and nuclear since 2008. Solar and onshore wind capital costs have fallen to roughly 80p and 95p per watt respectively (£1,080/kW solar, £1,275/kW onshore wind — EIA 2024 data); offshore wind costs roughly £1.60–2.20 per watt. Nuclear has gone the other way: Hinkley Point C, the UK's only plant under construction, is now costing roughly £48bn for 3.26 GW — about £14.70 per watt, seven to fifteen times MacKay's "a billion or perhaps two" per GW. [^u1] We (the UK) currently consume a total power of roughly 300 GW, most of which is fossil fuel. So we can anticipate that a major switching from fossil fuel to renewables and/or nuclear is going to require roughly 30…

29 What to do now

…ke is that sucking carbon dioxide from thin air will very probably be necessary to avoid dangerous climate change. Carbon is not even being captured at any coal power stations (except for one tiny prototype in Germany). Updated, 2026: CCS has since scaled to dozens of commercial facilities worldwide — see [[chap23|chapter 23's update]] — but at a rate still small next to global emissions, and no UK coal plant ever got one, because the UK phased out coal power entirely instead. Why not? The principal problem is that carbon pollution is not priced correctly. And there is no confidence that it’s going to be priced correctly in the future. When I say "correctly," I mean that the price of emitti…

…going to be high enough for long enough that carbon-capturing facilities will pay for themselves. Experts say that a long-term guaranteed carbon price of something like $100 per ton of CO2 will do the trick. Updated, 2026: neither the EU nor the UK carbon price has reliably reached that level — see [^u1]. So politicians need to agree long-term reductions in CO2 emissions that are sufficiently strong that investors have confidence that the price of carbon will rise permanently to at least $100 per ton of CO<s…

30 Energy plans for Europe, America, and the World

…er 4. The area of these wind farms, 435 000 km2, is roughly the same as the area of California. The amount of wind hardware required (assuming a load factor of 20%) would be a capacity of about 2600 GW, which ~~would be a 200-fold increase in wind hardware in the USA.~~ is a much smaller multiple today: US wind capacity grew roughly 20–30-fold between 2008 and the mid-2020s on its own, from a few GW to well over 150 GW. [^u2] ### Offshore wind If we assume that shallow offshore waters with an area equal to the sum of Delaware and Connecticut (20 000 km2, a substantial chunk of all shallow waters on the east coast of the US…

…m/3doaeg)] ### Solar heaters, solar photovoltaics, and concentrating solar power Solar thermal water heaters are a no-brainer. They will work almost everywhere in the world. China are world leaders in this technology. ~~There’s over 100 GW of solar water heating capacity worldwide, and more than half of it is in China.~~ By 2023, global solar water heating capacity had grown to about 560 GWth, with China alone accounting for 72% of it. [^u6] Solar photovoltaics were technically feasible for Europe, but I judged them too expensive. I hope I’m wrong, obviously. It will be wonderful if the cost of photovoltaic power drops in the same way that the cost o…

…r Europe, but I judged them too expensive. I hope I’m wrong, obviously. It will be wonderful if the cost of photovoltaic power drops in the same way that the cost of computer power has dropped over the last forty years. It did, and then some: solar PV costs fell by roughly 80–90% between 2008 and the mid-2020s (see chapter 6's updates), and unsubsidised utility-scale solar became some of the cheapest electricity in the world. The "too expensive" judgement this plan is built on no longer holds — this is arguably the single most consequential fact in this chapter to revisit. [^u1] My guess is that in many regions, the best solar technology for electricity production will be the concentrating solar power that we discussed in [chapter 25](../Text/chap25.xhtml#solar) and earlier this cha…

…ar became some of the cheapest electricity in the world. The "too expensive" judgement this plan is built on no longer holds — this is arguably the single most consequential fact in this chapter to revisit. [^u1] My guess is that in many regions, the best solar technology for electricity production will be the concentrating solar power that we discussed in [chapter 25](../Text/chap25.xhtml#solar) and earlier this chapter. That guess didn't hold up: flat photovoltaic panels, not concentrating solar power, turned out to be the technology whose cost collapsed (see chapter 6's and this chapter's own updates), and PV rather than CSP now dominates deployment in sunny regions worldwide. The geometry below — how much desert area a given power output needs — still works the same way for PV as for CSP; it's the technology choice, not the arithmetic, that's changed. [^u7] There we already established that one billion people in Europe and North Africa could be sustained by country-sized solar power facilities in deserts near the Mediterranean; and that half a billion in North Americ…

31 The last thing we should talk about

…e rate of fossil fuel burning was roughly 1 Gt C/y in 1920, 2 Gt C/y in 1955, and 8.4 Gt C in 2006. (These figures include a small contribution from cement production, which releases CO2 from limestone.) [^3] Updated, 2026: global fossil fuel and cement emissions reached a record 37.4 billion tonnes of CO2 (about 10.2 Gt C) in 2024, still rising — see [^u1]. ![](/assets/figure247.gif) Figure 31.3. The arrows show two extra carbon flows produced by burning fossil fuels. There is an imbalance between the 8.4 Gt C/y emissions into the atmosp…

…[^9] In 2005, the best published methods for CO2 capture from thin air were quite inefficient: the energy cost was about 3.3 kWh per kg, with a financial cost of about $140 per ton of CO2. [^10] Updated, 2026: direct air capture is now commercially operating rather than just published research, but real-world costs remain higher than this 2005 estimate, typically $500–1,000 per tonne — see [^u1]. At this energy cost, capturing a European’s 30 kg per day would cost 100 kWh per day – almost the same as the European’s energy consumption of 125 kWh per day. Can better vacuum cleaners be desi…

32 Saying yes

…— title: "32 Saying yes" — # 32 Saying yes Because Britain ~~currently gets 90% of its energy from fossil fuels,~~ got roughly 90% of its energy from fossil fuels when this was written, and still gets roughly 75% of its total energy from them today — the progress is real but lopsided: fossil fuels' share of UK electricity has fallen much further, to about 32%, while heating and transport have barely started to move, [^u1] it’s no surprise that getting off fossil fuels requires big, big changes – a total change in the transport fleet; a complete change of most building heating systems; and a 10- or 20-fold increase in green power.…

A Cars II

…ical of lead-acid batteries), we’ll see that it’s hard to push the range beyond 200 or 300 km; but for an energy density of 120 Wh/kg (typical of various lithium-based batteries), a range of 500 km is easily achievable. Commercial EV battery packs now typically deliver 150–250 Wh/kg, roughly double MacKay's "lithium-based" assumption here. [^u1] ![](/assets/figure258.gif) Figure A.14. Theory of electric car range (horizontal axis) and transport cost (vertical axis) as a function of battery mass, for two battery technolo…

…an id="batteries">batteries. It would be nice to have even better batteries, but an energy density of 120 Wh per kg is already good enough, as long as we’re happy for the batteries in a car to weigh up to 500 kg. This judgement call, made in 2008 before a single mass-market long-range EV existed, held up: a 2024 Tesla Model 3 Long Range carries an 82 kWh pack (~500 kg) for an EPA-rated range of about 550 km — matching this chapter's "good enough" scenario on real hardware, not a projection. [^u2] In practice I imagine most people would be content to have a range of 300 km, which can be delivered by 250 kg of batteries. If these batteries were divided into ten 25 kg chunks, separately unpluggable, then a ca…

B Wind II

…qr5 from [quietrevolution.co.uk](http://www.quietrevolution.com). Not a typical windmill. ### Standard windmill properties The typical windmill of today has a rotor diameter of around ~~54 metres centred at a height of 80 metres; such a machine has a "capacity" of 1 MW.~~ 120–160 metres for onshore turbines (2–6 MW capacity); the largest offshore turbines now reach a 236-metre rotor diameter and 15 MW. [^u1] The "capacity" or "peak power" is the maximum power the windmill can generate in optimal conditions. Usually, wind turbines are designed to start running at wind speeds somewhere around 3 to 5 m/s and to stop if…

…" or "capacity factor," depends on the site; a typical load factor for a good site in the UK is 30%. [[3]](#chBn03) In the Netherlands, the typical load factor is 22%; in Germany, it is 19%. Capacity factors across Europe have since risen with taller towers and larger rotors; offshore wind averaged around 41% globally in 2023. [^u2] ### Other people’s estimates of wind farm power per unit area In the government’s study [[www.world-nuclear.org/policy/DTI-PIU.pdf\](http://www.world-nuclear.org/policy/DTI-PIU.p…

D Solar II

…uels. I’ll express the potential of each method in terms of its power per unit area (as in figure 6.11). ### Britain’s main biodiesel crop, rape Typically, rape is sown in September and harvested the following August. ~~Currently 450 000 hectares of oilseed rape are grown in the UK each year. (That’s 2% of the UK.)~~ UK oilseed rape area has since fallen to roughly 300 000–350 000 hectares (about 1.3% of the UK), down from a peak of over 600 000 ha around 2012 — flea-beetle damage and crop economics, not less demand for biodiesel. [^u1] Fields of rape produce 1200 litres of biodiesel per hectare per year; biodiesel has an energy of 9.8 kWh per litre; [[2]](#chDn02) so that’s a power per unit area of <span class="green…

E Heating II

…talled ground-source heat pumps and the best air-source heat pumps usually have a coefficient of performance of 3 or 4; however, government regulations in Japan have driven the coefficient of performance as high as 6.6. Updated, 2026: this 3–4 range is still typical, but is now achieved routinely rather than only by the best installations — see [[chap21|chapter 21's update]]. These theoretical limits could only be achieved by systems that pump heat infinitely slowly. Notice that the ideal efficiency is bigger, the closer the inside temperature T2…

…talled ground-source heat pumps and the best air-source heat pumps usually have a coefficient of performance of 3 or 4; however, government regulations in Japan have driven the coefficient of performance as high as 6.6. Updated, 2026: this 3–4 range is still typical, but is now achieved routinely rather than only by the best installations — see [[chap21|chapter 21's update]]. While in theory ground-source heat pumps might have better performance than air-source, because the ground temperature is usually closer than the air temperature to the indoor temperature, in practice an air-source hea…

F Waves II

…deliver 19 kW/m, including transmission to central Scotland (Mollison, 1986). The Pelamis device, created by Ocean Power Delivery, has taken over the Salter duck’s mantle as the leading floating deep-water wave device. Updated, 2026: Pelamis Wave Power went into administration in 2014 — see [^u1]. Each snake-like device is 130 m long and is made of a chain of four segments, each 3.5 m in diameter. It has a maximum power output of 750 kW. The Pelamises are designed to be moored in a depth of about 50 m. In a wavef…

…er than 15 kW/m. Its peak power is 600 kW. A single device would produce about 270 kW in wave heights greater than 3.5 m. It’s predicted that an Oyster would have a bigger power per unit mass of hardware than a Pelamis. Updated, 2026: Aquamarine Power ceased trading in November 2015 — see [^u1]. Oysters could also be used to directly drive reverse-osmosis desalination facilities. "The peak freshwater output of an Oyster desalinator is between 2000 and 6000 m3/day." That production has a value, going…

I Quick reference

…652 | | Italy | 667 | | Ireland | 784 | | Greece | 864 | | Denmark | 881 | Figure I.9. Carbon intensity of electricity production (g CO2 per kWh of electricity). This whole table is a ~2007 snapshot and every entry in it has moved; the UK's figure in particular has fallen by more than three-quarters. Rather than re-source all eleven countries individually, here are updated figures for the three this book leans on most: UK, roughly 124–125 gCO2/kWh in 2024 (down from 580); France, roughly 22 gCO2/kWh in 2024 (down from 83, already the table's cleanest entry and now cleaner still); EU average, roughly 213 gCO2/kWh in 2024 (down from the 353 figure below). [^u1] Fuel type emissions (g CO2 per kWh of chemical energy) natural gas 190…

Preface

…ome of my numbers were off by a factor of two. While I hope that the errors that remain are smaller than that, I expect to further update some of the numbers in this book as I continue to learn about sustainable energy. Updated, 2026: MacKay died in 2016 and could not do this himself — see [^u1]. How to cite this book: David J.C. MacKay. Sustainable Energy – without the hot air. UIT Cambridge, 2008. ISBN 978-0-9544529-3-3. Available free online from [www.withouthotair.com</spa…

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