Sustainable Energy Without the Hot Air by David MacKay

What does a world without fossil fuels look like?  There are lots of different options, but none of them look much like the rich developed nations of the world today.  David MacKay’s approach in Sustainable Energy Without the Hot Air is to hold our rate of energy consumption constant, and explore the kinds of carbon-free energy systems that could satisfy that demand.  The uncomfortable conclusion he comes to is that if we want to run our world on renewables, the energy farms have to be comparable in scale to nations.  Comparable in scale to our agricultural systems.  This is because all renewable energy is very diffuse, and we use a whole lot of energy.

SunPower's Bavarian PV Installation

Just as an example, of all the renewable power sources solar is the most concentrated, and PV farms like the ones cropping up in Bavaria because of Germany’s generous feed-in tariff average about 5W/m2.  With better siting (the Sahara, Arizona) you can do a bit better, and there’s a little more efficiency to be eked out of the panels, but for large scale deployments, you’re not going to get above 10W/m2.  If you’re an average citizen of the EU or Japan, your 5kW of power thus demands 500m2 of land.  Multiply that by 700 million people in the EU, and you get the total area of Germany.  An average North American’s 10kW requires 1000m2.  Multiply that by 300 million people, and you get an the entire area of Arizona.

In India over the last few days extreme heat and drought have driven demand for electricity to run air conditioning and groundwater pumps for irrigation.  The result has been that the country has suffered unimaginably vast blackouts, leaving more than 600 million people without electricity, which today they mainly generate with coal.  Say they wanted to go solar, and at the same time the entire population of India managed to bootstrap its way out of energy poverty, seeking the same (supposedly modest) 5kW lifestyle that the EU and Japan currently enjoy.  How much area would they have to dedicate to collecting that solar power at 10W/m2?  About 600,000 km2, which is 75% the area of Pakistan, or 3 times the area of India’s Thar Desert.  And this is something of a best case scenario.

Solar farming is the least space intensive form of scalable renewable power.  Everything else is even more space intensive.  In our relatively sunny, windy, sparsely populated Colorado, we could conceivably get away with this strategy, dedicating only a few percent of the state’s overall area to energy harvesting — the entire area of Weld County would just about do it.  This is a very challenging strategy to scale up to billions of people, at typical population densities, with developed-world consumption patterns.  Doing so would necessarily mean lots of international trade in energy because the deserts of the world are not evenly distributed.  The new energy superpowers?  Namibia, Libya, Algeria, Egypt, Iraq, Pakistan, Iran, Australia, Xinjiang, Mongolia, Texas, Arizona, Nevada, Chihuahua, and of course our good ol’ buddies in the House of Saud.

This dubious energy strategy is what Alex Steffen has dubbed “The Swap“: we keep on living the way we’ve been living, and exchange various components of the system, one at a time, without re-designing the system very much overall.  Solar farms instead of coal fired power plants.  Electric cars instead of oil cars.  But we keep the cars, the cul-de-sacs, and the cheap plastic crap from WalMart.  Steffen thinks this type of plan is ludicrously unambitious, and I tend to agree.  It’s one end-member in the solution space, along the “lifestyle” axis.

MacKay knows this, and has consciously chosen to avoid direct advocacy of lifestyle changes, in the interest of first and foremost getting the magnitude of the fossil fuel problem across.  He repeatedly points out that he’s not trying to be anti-wind or pro-nuclear or advocating for much of anything in an ethical sense, except that whatever plan we come up with for getting off fossil fuels needs to add up.  In his words, he is simply “pro-arithmetic”.  Energy produced must equal energy consumed.  It would be nice to think that advocating for something so basic as an energy policy that actually adds up would be laughable, but unfortunately it’s not.  There’s little acknowledgement amongst policymakers (at least in public) of how big a change we’re talking about.

I think he’s probably wise to leave the question of lifestyle in the background for the moment.  In the end, if you really absorb the scale of the problem, and honestly try to come up with your own plan that adds up, it quickly becomes clear that not considering lifestyle a potential variable makes solving the problem unnecessarily difficult.  The jokes MacKay makes throughout the book and in talks I’ve watched him give, and the character of his own daily existence (cycling around Cambridge, wearing a sweater indoors during the winter, and eating less meat) suggest that his personal preference is to include lifestyle alterations in the overall plan.

France's Nuclear Energy

The elephant in the supply room is nuclear power.  Sustainable nuclear power (billions of people, hundreds to thousands of years) is doable, if we build fast breeder reactors globally at the same rate we were building traditional once-through nuclear plants in the 1970s and early 1980s in the US and France, and use traditional uranium and thorium reserves and/or ocean sourced uranium.  Or if we figure out fusion.  As I’ve said elsewhere, I wouldn’t axiomatically rule the nuclear option out, but I’d certainly put it below modest lifestyle alterations in the list of things to consider.  For reasons of cost as much as anything.

Saul Griffith took a slightly different approach in his wonderful Long Now talk Climate Change Recalculated (with some inspiration from MacKay).  Instead of holding lifestyle constant and considering the scale of the supply required to meet it globally, he held world power consumption constant (~15-20 terawatts), assumed we would bring our own use down to the mean (2kW), and the developing world up to it, and looked at both what kinds of lifestyles are available at that level of consumption, and what scale the necessary carbon-free energy production infrastructure would have.  It’s still monumental.  It’s still the size of a small continent or very large nation, which he dubbed Renewistan, but it’s five times easier than supplying each of 9 billion people with 10 kW of zero carbon power, and much fairer than maintaining our own profligate use and telling others to suck it up and continue living on less than a fifth that much.

Radical efficiencies become available if you’re willing to consider fairly modest lifestyle alterations.  Bicycles use about 100W of power.  Cars use around 50,000W.  Assuming you spend the same amount of time in transit on either one, bikes use 500 times less energy overall.  It’s not just that they use less energy per mile, it’s also important that lives built around that kind of transportation involve many fewer miles.  It’s challenging to live under your own power in Los Angeles or Houston, but cities don’t have to be built like that.  Similarly the Passive House building energy efficiency standard reduces building energy use by roughly a factor of ten.  The standard can be met today at little to no additional construction cost in Germany, where there are many thousands of such buildings in operation, and robust competition in the energy efficient construction market.  It is especially cost effective in modest density urban environments where natural shading can be used to minimize solar heat gain in the summer, and buildings or dwelling units often share walls.  All this to say: better land use and transportation systems, coupled with cost-effective building efficiency can remove roughly half of our primary energy demand.  Half!  Just by living in a city that looks like Amsterdam or Copenhagen, with modern buildings.  This is not a downgrade.  These cities routinely rank as among the best in the world for quality of life.  This is not a technoutopian fantasy.  We can do these things today and they’re cheap.

The final big variable you can tweak to make the future work is of course the overall human population.  It’s entirely possible that the younger among us will live through peak population this century, even without any kind of totalitarian birth control policies.  If the globe had the 1.4 children per woman fertility rate of Japan, Germany, Russia, and Italy, we’d cut the world population by two thirds every century.  Unfortunately, on our current trajectory, that potential population reduction will come far too late to avoid permanent alterations to the Earth’s climate.

Today, those are basically the options*: xenoform the homeworld with greenhouse gases, build continent sized renewable installations, build nuclear power on a scale 100 times greater than we’ve got it today, dramatically lower the energy intensity of our lifestyle, dramatically reduce the overall human population, or enforce a grossly inegalitarian distribution of energy worldwide.  Or any combination of the above in the appropriate proportions.  Every one of these options will get you booed off the stage in front of a significant number of audiences, but there’s a false dichotomy in many people’s minds, that we can somehow do nothing, and nothing will change.  That’s not an option.  What many see as “doing nothing” is active change on an unprecedented scale.  It is the transformation of this planet into another, which is not home to the vast majority of extant species.  What we actually have to choose is which kind of change we want to embrace.  We have to start saying yes to something.

As much as anything, this book is a testament to the utility doing order of magnitude calculations.  This is something physicists do all the time, but policymakers often seem incapable of.  It only requires high-school level math, and getting the rough numbers is easier than ever with resources like Wikipedia at our fingertips.  Approximate numbers are often enough to tell you whether something is easy, difficult, or impossible.  They can tell you, conclusively, that cities cannot grow all their own food within their city limits.  They can tell you that the cost of goods you have to transport across oceans in container ships is not sensitive to the price of oil, but the price of a plane ticket is.  If everyone could do these calculations, or at least abide by their results, we’d have a much more interesting and nuanced policy discussion.  We’d also have to admit that the scale of what we’re talking about with energy is more like the entire WWII effort (on both sides) than an Apollo or Manhattan project.  But hey, at least it’s not impossible!

And if you’re still not convinced you should read this book, at least give yourself a more thorough preview by watching him talk about it at Harvard:

*(Are there other hypothetical options?  Sure: carbon capture and storage, which requires an industrial plant comparable in scale to the fossil fuel industry, and must come with an ironclad guarantee that leakage rates will be less than 0.1% per year for the next 1000 years.  Orbital solar farms with microwave rectenna arrays on the ground to receive the beamed power.  Fusion, as always.  We can’t build any of those things today, and we need to solve this problem now.)

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Zane Selvans

A former space explorer, now marooned on a beautiful, dying world.

4 thoughts on “Sustainable Energy Without the Hot Air by David MacKay”

  1. Excellent post Zane. I definitely appreciated MacKay’s perspective in the book: let’s look at the available energy sources and see what quantity and combinations are required to actually add up to a plausible model of our usage! Looking forward to watching his Harvard presentation.

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