Ben Laurie blathering

Sustainable Energy

I’ve become very interested in sustainable energy lately, not least because I now own a farm in Wales, which has all sorts of stuff like wind, water and trees on it. So, I was very pleased when my mother-in-law gave me a copy of Sustainable Energy – Without the Hot Air, by David MacKay, for Christmas. This book takes a straightforward and fact-based approach to the question, summing up all the sinks of energy and possible sustainable sources, and seeing what works. The sad fact is, it seems, that not much does. For example, there’s a bit of a fad right now for wood-burning boilers, and renewable energy websites (note that the book talks about sustainable energy, which is not the same thing) are likely to tell you that it’s the cheapest fuel around – as well as being carbon neutral, of course.

So, I did a quick calculation, using the figures from the book. Each person needs 36 kWh/day for heating. Wood at its best has an energy density of 5.5 kWh/kg, so that means I need about 6.5 kg of wood per day or about 2.4 tons a year. Around these parts, we can produce (sustainably) about 10 dry tons per hectare of wood, so I need about .25 of a hectare to produce all the wood I need forever. Well, until the sun goes out. Of course, it’s a 5-bedroom house, so we need maybe 1.5 hectares for the whole house – which is just under 4 acres, for the more traditional. I can do that, quite easily. But could everyone? If everyone in the UK were to use wood for heating, we’d need about 15,000,000 hectares of wood. The UK is about 24,500,000 hectares. Oops. And that, my friends, is the difference between sustainable and renewable.

The book is also available for free in PDF form from the author’s website. But don’t forget that if you buy the book, you are sequestering carbon!

By the way, a minor historical note, David MacKay is also responsible for Dasher, which is a very cool piece of software – and so I think I may have met him a few years back in a pub in Cambridge, when FreeBSD, Apache and Dasher folk drank beer together. If so, I am honoured to have had beer with such a clear thinker!

My transatlantic friends should note: this book is calibrated for the UK. I’m sure it’s possible to transliterate it to the US or elsewhere, but it’ll take some work.



    Comment by Ben Hyde — 17 Jan 2010 @ 0:41

  2. Googling suggests about 10% of UK land is currently forest – 2,500,000 Hectares, or so.

    David McKay is quite pessimistic about the prospects for improving energy efficiency. Certainly, 36Kwh(th)/day sounds like rather a lot. The difficulty is going to be improving the insulation of existing housing stock for any reasonable cost. (If only we had a large number of unemployed people without anything better to do, and absurdly low interest rates, making low-yield investments seem attractive…)

    Brand NEW housing, on the other hand, can be realistically insulated up the the eyeballs, at which point you find that it stays almost adequately warm on the heat of occupants and appliances, and all you need is a few kW(th) on cold winters’ evenings. (See Vale & Vale, “The New Autonomous House”, for more detail than you ever wanted, including airlocks for cats). The additional insulation is damn near paid for, or entirely paid for, by the lack of need for radiators, boiler, pipework etc. (Amory Lovins calls this sort of happening “tunnelling through the cost barrier” —

    Unfortunately, this concept is parked squarely in an ideological blind spot. Economists assume it can’t be there (rational expectations etc mean it’s not plausible that everyone’s been so daft), and most environmentalists would like something more *visible*, and perhaps some asceticism-lite, like wearing an extra jumper and turning your heating down (ideally not cashmere, because that’s too comfortable). Building energy services, like sewage systems and system administration, tend to be invisible when run competently, and so get ignored by everybody.

    On the subject of competence, certain entities known for egregious competence — such as google, and the German Government — favour investment in solar energy, because of the possibility of bringing costs down dramatically through economies of scale. That’s unlikely to work well on a Welsh farm, unfortunately. can probably advise on geographically appropriate options.

    Comment by ti — 18 Jan 2010 @ 21:48

  3. […] Filed under: books,reference — padraic2112 @ 4:41 pm Tip o’ the blogger hat to Ben Laurie. This book (Sustainable Energy – Without the Hot Air) takes a straightforward and fact-based […]

    Pingback by Something to Read « Pat’s Daily Grind — 4 May 2010 @ 1:43

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