David MacKay: Sustainable energy without the hot air

[For accessibility, I've bumped the time-stamp on this post from 2010 to 2011. Ed.]

Please don’t get me wrong: I’m not trying to be pro-nuclear. I’m just pro-arithmetic. — David MacKay

This is the book I wish I had written. MacKay is a Cambridge physicist who approaches the climate change/energy policy issues with the same critical-thinking, level-headed approach that we have applauded in the work of University of Adelaide prof. Barry Brook. A very positive sign for UK energy policy is that MacKay was recently appointed Chief Scientific Advisor to the UK Department of Energy and Climate Change responsible for the Low Carbon Transition Plan [DECC]

Regular readers know that to evaluate energy policy options we need full life-cycle-assessment (LCA) projections of each option with respect to:

1. Energy intensity

2. Carbon intensity

3. Cost per ton of CO2 avoided

4. Full life-cycle cost per unit of electric power generated including capital, operating & maintenance and decommissioning costs. (pick your units, I prefer GWhe {billion watt hours-electric})

A recent objective study of values {1, 2} for energy/GHG intensity is the 2006 study by the Integrated Sustainability Analysis (ISA) unit at the University of Sydney. The ISA unit is a valuable resource as they specialize in input-output-based life-cycle assessment (IO-LCA). For {4} please see The Economics of Nuclear Power. Another recent source is the 2011 UK report “The Renewable Energy Review” [PDF] by the Committee on Climate Change which is the primary body guiding UK GHG targets.

We also require reliable projections of energy demand and supply. In particular, for supply we need a grasp of how much supply from each nominated energy source is feasible, ignoring costs, political, and environmental considerations. This is the area where Dr. MacKay’s new book shines. It is easy to get lost in the weeds of engineering, technology and economics in any serious attempt to assess how the planet might meet future energy demand. MacKay’s book makes the first step approachable by readers who haven’t an engineering background nor years of experience in the energy industry.

D. Bull (Wellington, New Zealand), contributed this very to-the-point review for the book page at Amazon.com:

I work for an environmental watchdog in New Zealand. I flicked through the first few pages of “Sustainable Energy – without the hot air” as it sat on a colleague’s desk, took it back to my own desk and read it for two hours straight, got online and bought my own copy. It’s that good.

For a start, this is how environmental science should be communicated; crystal clear text and honest graphs, with simplified theory and ballpark calculations that anyone can follow, backed up by empirical data as a check on results, real examples, frequent references, and explanations of limitations.

But the thinking behind it is every bit as good. MacKay is entirely pragmatic about energy supply and demand, never preachy, and he is game enough to admit when his results surprise even himself. If he is cautiously optimistic in his conclusions, it is because he has laid out a number of justifiable options. Buy it. Better still, buy it and read it.

The book is about the physical limits of power production. MacKay achieves clarity by focusing upon the physics while ignoring the economics and politics.

Let me close this chapter with a few more warnings to the reader. Not only will we make a habit of approximating the numbers we calculate; we’ll also neglect all sorts of details that investors, managers, and economists have to attend to, poor folks. If you’re trying to launch a renewable technology, just a 5% increase in costs may make all the difference between success and failure, so in business every detail must be tracked. But 5% is too small for this book’s radar. This is a book about factors of 2 and factors of 10. It’s about physical limits to sustainable energy, not current economic feasibility. While economics is always changing, the fundamental limits won’t ever go away. We need to understand these limits.

(…) Whether the sustainable energy sources that we put in the right-hand stack are economically feasible is an important question, but let’s leave that question to one side, and just add up the two stacks first. Sometimes people focus too much on economic feasibility and they miss the big picture. For example, people discuss “is wind cheaper than nuclear?” and forget to ask “how much wind is available?” or “how much uranium is left?”.

Like Barry Brook, MacKay insists throughout that the numbers must add up. That means that policy proposals must demonstrate how they will provide the carbon-free energy that the developing world will be consuming. We know for certain that they will be consuming coal unless we show them a practical carbon-free “cheaper than coal” strategy.

You’ll want to read and reflect on the hardcopy of the book — and keep a copy handy for reference. While you are awaiting delivery you can read the book online, including a PDF download.

Lastly, I will excerpt three paragraphs that exemplify MacKay’s treatment of the numbers:

I heard that nuclear power can’t be built at a sufficient rate to make a useful contribution.

The difficulty of building nuclear power fast has been exaggerated with the help of a misleading presentation technique I call “the magic playing field.” In this technique, two things appear to be compared, but the basis of the comparison is switched halfway through. The Guardian’s environment editor, summarizing a report from the Oxford Research Group, wrote “For nuclear power to make any significant contribution to a reduction in global carbon emissions in the next two generations, the industry would have to construct nearly 3000 new reactors – or about one a week for 60 years. A civil nuclear construction and supply programme on this scale is a pipe dream, and completely unfeasible. The highest historic rate is 3.4 new reactors a year.” 3000 sounds much bigger than 3.4, doesn’t it! In this application of the “magic playing field” technique, there is a switch not only of timescale but also of region. While the first figure (3000 new reactors over 60 years) is the number required for the whole planet, the second figure (3.4 new reactors per year) is the maximum rate of building by a single country (France)!

A more honest presentation would have kept the comparison on a per- planet basis. France has 59 of the world’s 429 operating nuclear reactors, so it’s plausible that the highest rate of reactor building for the whole planet was something like ten times France’s, that is, 34 new reactors per year. And the required rate (3000 new reactors over 60 years) is 50 new reactors per year. So the assertion that “civil nuclear construction on this scale is a pipe dream, and completely unfeasible” is poppycock. Yes, it’s a big construction rate, but it’s in the same ballpark as historical construction rates.

How reasonable is my assertion that the world’s maximum historical construction rate must have been about 34 new nuclear reactors per year? Let’s look at the data. Figure 24.14 [see figure at upper left of this post] shows the power of the world’s nuclear fleet as a function of time, showing only the power stations still operational in 2007. The rate of new build was biggest in 1984, and had a value of (drum-roll please…) about 30 GW per year – about 30 1-GW reactors. So there!

– Updated 1/6/10 1:00 PM: I just wanted to add this glowing review by Cory Doctorow:

David JC MacKay’s “Sustainable Energy — Without the Hot Air” may be the best technical book about the environment that I’ve ever read. In fact, if I have any complaint about this book, it’s in how it’s presented, with its austere cover and spartan title, I assumed it would be a somewhat dry look at energy, climate, conservation and so on.

It’s not. This is to energy and climate what Freakonomics is to economics: an accessible, meaty, by-the-numbers look at the physics and practicalities of energy. MacKay, a Cambridge Physics prof, approaches the subject of carbon and sustainability with a scientific, numeric eye. First, in a section called “Numbers, not adjectives,” he looks at all the energy and carbon inputs and outputs in Britain and the rest of the world: this is how many kWh of energy are needed to power all of Britain’s vehicles. This is how many kWh you would get if you covered the entire British shore with windmills, or wave-farms. This is Britain’s geothermal potential. Here’s how much carbon vegetarianism offsets. Here’s how much carbon unplugging your idle appliances saves (0.25%, making the campaign to switch off energy vampires into a largely pointless exercise — as MacKay says, “If everyone does a little bit, we’ll get a little bit done”). This is the carbon-footprint of all of Britain’s imports, gadgets, office towers, and so on.

Using a charming, educational style that teaches how to think about this kind of number, how to estimate with it, and what it means, MacKay explains these concepts beautifully, with accompanying charts that make them vivid and clear, and with exhaustive endnotes that are as interesting as the text they refer to (probably the best use of end-notes I’ve encountered in technical writing — they act like hyperlinks, giving good background on the subjects that the reader wants to find out more about while allowing the main text to move forward without getting bogged down by details).


This reminded me of nothing so much as Saul Griffith’s wonderful talk on climate change as an engineering problem. Add up all the energy we can make if we harness every erg, every photon. Subtract all the energy we want to use. Examine this difference and come up with strategies for bringing the two into balance. Once you get this approach, it becomes a lot simpler to figure out what is and isn’t worth doing.

UPDATE: more on MacKay’s appointment as chief scientific advisor to DECC.

UPDATE February 2012:  UK DECC chief scientist David MacKay supported estimates that all of England’s electrical needs can be supplied for 500 years by burning the existing UK “waste”. This is in the context of Duncan Clark’s article on deployment of fast reactors such as the GE Hitachi PRISM being proposed to burn the UK “waste plutonium”.

(…) According to figures calculated for the Guardian by the American writer and fast reactor advocate Tom Blees, this alternative approach could – given a large enough number of reactors – produce enough low-carbon electricity from Britain’s waste stockpile to supply the UK at current rates of demand for more than 500 years.

MacKay confirmed this figure. “As an upper bound on what you could get from those resources in fast reactors I think it’s a very reasonable estimate. In reality you’d get all kinds of issues so you wouldn’t achieve the upper bound but I still think it’s a reasonable starting point.”

5 thoughts on “David MacKay: Sustainable energy without the hot air

  1. Hi, I would like to recommend the book to some people in Austria, both ordinary citizen and also political. It would be a lot easier, if there would be a German version of it availble.
    Do you know if and when such a translation is planned ?
    Sincerely, Erich Schieber, 3244 Ruprechtshofen, Austria

  2. Thank you for your comments, and for the link to your review of David MacKay’s “Sustainable Energy – without the hot air”. I’ve read your review twice, and am working my way through your other posted reviews. I agree in general with your review of Mackay’s book, which is a remarkable contribution to the literature on energy policy.

    You make several good points on the economic realities of energy policy, such as

    MacKay barely touches upon the energy and non-energy resource cost of creating the infrastructure that will provide all this renewable energy. This is not a trivial matter.  

    I have just one quibble with the way you characterize the book as concluding that “yes, it is physically possible to fulfil a country’s energy needs with renewable energy”.

    Adding to MacKay’s physics analysis a view of political economy and economic efficiency, my conclusion was rather the inverse. Specifically, that “renewables” as popularly defined could make a useful but small contribution to a zero carbon 2060 future. There are a number of special cases, such as availability of buffering hydropower, that allow wind and solar to compete. But Kholsa’s “Chindi test” of “cheaper than coal” and nearly-zero-carbon is only satisfied by nuclear power.

    MacKay was very careful to avoid “picking winners” in his text. But I think you can see his mind in the quote I chose to head this post:

    Please don’t get me wrong: I’m not trying to be pro-nuclear. I’m just pro-arithmetic. — David MacKay

    Of course I cannot speak to what Dr. MacKay actually thinks. In his own words, his Q&A site includes the following:

    You say I am pro-nuclear; I don’t quite agree; the way I would put it is “I am in favour of any plan that adds up”; and I think we should push for a plan that adds up, not half measures and figleafs. I would be perfectly content with a renewable-only plan. I don’t think we should allow religious dogmatism about any one option to prevent us making a plan that adds up. All technologies have risks, and many human activities make toxic waste. I discuss nuclear waste in the book. It’s not infinitely dangerous. It is dangerous. Where to put it? Well, there’s lots of choice, but here’s one idea for the UK – we already have armed guards and security fences around Balmoral, and the public aren’t allowed in there. So we could kill two birds with one stone. The entire UK’s high-level nuclear waste for 50 years could easily be stored in a very small area (one square km is more than enough). The high level waste remains intensely nasty for roughly 1000 years. It’s definitely nasty, but as I say in the book, I think it’s a relatively small problem, compared with the much greater bulk of other wastes, and compared with the challenge of making an honest plan that adds up. In Britain today, there are anti-wind people, anti-tidal-barrage, anti-nuclear, and anti-coal campaigns. We can’t be anti-everything. We need a plan that adds up. Not wishful thinking. Honest numbers.

    In his comments he avoids any discussion of next-generation nuclear technology — which consumes as valuable feedstock what is today called “nuclear waste”. I think that exclusion is entirely appropriate to the purpose of his book. But IFR is a real technology. In 2060 it will not even be controversial.

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