Wind farm wakes

Via David Mackay; mostly I just love the photo:


(Oh yeah, and being downwind can easily reduce the power generation of a turbine by 20-30%, or even more. One more thing to keep in mind when calculating the magnitude of renewable energy potential.)

Energy games

David Mackay points to the Energy Game, an interesting-looking simulation designed to educate people about the trade-offs inherent in energy policy decisions. As I note in his comments, Chevron created a (VERY simplistic) online simulation, Energyville, along seemingly similar lines.

I would be curious to understand the Energy Game's level of realism and complexity. But most importantly, as Mackay says, these educational efforts are to be applauded.

Update: Commenter Damon has a neat app which shows graphically how energy demand compares to renewable energy supply. It's easy to think of ways the display could be expanded beyond the current binary renewable/non-renewable distinction (e.g. cost, GHG emissions reduction, etc.), but it looks like the guts are there in the model...

Pat on the back: Mackay in NYTimes/IHT

David Mackay is in the NYTimes/IHT with an article on the future of energy, featuring his charts and arguments on the land footprint of renewable energy; you saw it here almost a month ago (pats self on back).

Land footprint of renewable energy

I can't award this "killer chart" status because I don't find it very visually appealing, but David Mackay's synthesis brings up a great point (italics are mine):

Conclusion: All countries whose power consumption per unit area is bigger than 0.1 W/m2 are countries who should expect renewable facilities to occupy a significant intrusive fraction of their country, if they ever want to live on their own renewables. Countries with a power consumption per unit area bigger than 1 W/m2 (eg UK, Germany, Japan, Netherlands, Belgium) would have to industrialize most of their countryside, if they want to live on their own renewables. Alternatively, their options are to radically reduce consumption, use nuclear power, and/or to buy renewable power in from other countries.

The land footprint of renewable energy isn't much on the radar of the public dialogue around alternative energy - Sustainable Energy Without The Hot Air is the only place I see it brought up regularly - and yet it is a serious constraint to any renewables-heavy future, and one not very well understood by most of that future's proponents.

Here is the chart:

NIMBY, or anywhere else

Britain and its manufacturing workers are dismayed that energy giants like BP and Vestas are giving up on wind power in the U.K. and moving on to bigger and better places like the U.S. and China. David Mackay shines light on why with two strikingly similar maps. One shows areas within 2k of human habitation, which are of course too close for wind farm development. The other shows areas with high wildlife sensitivity, which are or course also not suitable for wind farm development. As he says, "Wind farm development is to be encouraged in all other areas on the map."

And what about offshore?

For Tony Hayward, CEO of BP PLC, the company’s preference for onshore wind is just a question of logistics. An onshore wind farmer can drive up in his 4×4 to fix his turbine if it conks out; if it’s in the middle of the North Sea he’ll need a big boat and crew. And he’ll struggle to find one suitable. “There’s no supply chain to service offshore wind farms,” he told reporters Tuesday.

He also doubts the technology exists to build a wind turbine that would survive for 20 years in the extreme conditions north of the Shetland Isles, Britain’s remotest point. That coming from a company that operates drilling platforms in some of the world’s deepest waters and stormiest seas is a pretty bleak assessment.

Downwind Faster Than The Wind

The speed of wind seems like a plausible upper bound on the speed of a vehicle powered by that wind, and David Mackay thought so even though he knew of wind-powered vessels which can sail directly upwind. But he is delighted to discover that he is wrong (here is proof and explanation).

His reaction and reflection on his mental processes is interesting:

What intrigues me philosophically about the wind-powered-travel expositions is that it reveals how fragile and weak "understanding" can be: I thought I understood wind-powered travel, and I already knew about wind-powered vessels that can sail directly upwind (eg, Revelation II, pictured). But I got the answer to the question "is DWFTTW possible?" wrong! - even though the principle by which upwind travel works is just the same as the principle of DWFTTW travel. So it seems that when I "understood" upwind travel, what I really did was append to my stack of physics heuristics another heuristic, permitting upwind travel; I didn't add a piece of knowledge that was capable of working in new situations.

I find this encouraging not because the specific discovery is cool (although it is), but rather because seeing “obvious” truths overturned bodes well for the prospect of technological energy advances that we have not imagined today. A lot of economic analyses of renewable energy potential work from back-of-the-envelope uppers bounds on the resources available given “reasonable” tech advancement; while they conclude, I think rightly given that starting point, that renewables won’t make up a major part of energy production for decades, this gives reason to believe that “unreasonable” tech advances could help us get closer.

Now, I wonder if we could solve the intermittency problem with wind power by engineering the equivalent of a wind turbine atop a giant treadmill?

Debunking wind energy twaddle

No one does it better than David Mackay:

The Torygraph has actually published this "startling" (and false) meme a second time, this time in an "Analysis" piece authored by "Dave Andrews, head of the Claverton Group", published on 16th July 2009. He writes of onshore wind that "it needs an area of only 70 square miles to generate Britain's total power requirements". Crikey. Did the copy-editor do this to make the Claverton Group look like a bunch of fools? Apparently so - The Claverton site says the article as submitted said "a 70-mile by 70-mile square". Yes, that would be 70 times more accurate! For the record, (see my survey of UK wind farms if you want, where I show that UK wind farms, whether onshore or offshore, generate roughly 2.5 watts per square metre, on average), 4900 square miles of windfarms would generate about 32 GW on average, which is close to Britain's average electricity consumption (it's about 42 GW). If you want to produce "all Britain's energy consumption today" (ie transport and heating too) then you need about nine times the area, since Britain's primary energy consumption is about 300 GW.

The bottom line - the Daily Mail article is off by a factor of 825, and the Telegraph's rendition of Clavertonism is off by a factor of 70 or 630, depending on whether you allow energy to be confused with electricity.

His Sustainable Energy Without the Hot Air is required reading for anyone interested in alternative energy. I only wish that 1), he would do this more often (perhaps he is too busy teaching Britain's "best and brightest"), and 2), we had someone like this in the U.S. to lay down some factual outer bounds - to renew-o-philes and enviro-skeptics alike - on how much of American electricity demand alternative energy could potentially satisfy. The public debate would benefit from understanding and agreeing that the answer is somewhere in the range of "some, but not most."