(written April 13, 2012. Part of the Great Upload of 2013…)
As a guy whose birthday falls on the 13th, it always bugged me that my 13th birthday was a Saturday… those darned leap years!
One of my concerns in the past several years has been the fact that “energy-return-on-energy-invested” (EROEI) for fossil fuels has been decreasing. This is most evident in the petroleum sector: in the good old days, all you needed to do was stick a steel straw in the ground, and you’d get oil. (As an Algerian colleague once told me, “back home, we drill wells looking for water, but all we get is oil. It’s like, what the hell? Oil again??”)
In the days of yore (and lost Lenores) for each unit of energy you “invested” to get the oil, you might have gotten 50x or 100x units of energy back. Alas, this happens “nevermore”.
EROEI has been dropping because, while we’ve become more efficient at extracting oil, difficulty-of-extraction has gone up even faster. The oil sands are the most extreme case: for each unit of energy you invest to turn the bitumen into oil, you might get… 5x units of energy back. So if you want to extract 100 units of oil energy, your cost is no longer 1-2 units of energy… but 20 units of energy, plus a bunch up-front! (This is why it takes many months and mammoth money to increase oil sands production.)
And while recent developments such as North Dakota’s “tight oil” probably have a better EROEI, they won’t reverse the drainward trend. Coal is in much the same boat, though natural gas is a different story — we only started to tap the world’s largest natural gas field in the past few years, so its EROEI will probably stay high for awhile.* Since the hydrogen for most fuel cells comes from natural gas, that’s good news. (Plus, it’s easier to obtain natural gas equivalents from renewable resources, than liquid fuels…)
Declining EROEI is kind of depressing from a societal perspective, because it suggests that we’ll have to work harder and harder to acquire the energy we’ve accustomed ourselves to — as anyone who’s bought gasoline recently can attest. ;) (As if environmental damage, converging debt crises and aging populations weren’t enough!)
EROEI for renewables
Fortunately, EROEI is increasing rapidly in the renewables sector, helping it continue its exponential growth — and that is a cause for optimism. At the end of 2011, there was enough installed solar and wind capacity to provide 3% of the world’s electricity. (That number already factors in the fact that it’s sometimes nighttime, and windless.) And the growth rate is high enough that it could hit 20% by 2020. That’s a lot of coal plant closures! Much beyond that, though, and you start to run into realistic limits for wind power**, though solar would still have a lot of “blue sky potential”, in the business parlance. I hope to ramble about the physical laws governing whales and wind turbines sometime soon…
In terms of solar, the main energy input in making a solar panel comes from creating ingots of 99.999 999 9% pure silicon. These parts-per-billion impurity levels are so low, you have a better chance of winning the jackpot on a lottery ticket, than randomly picking a non-silicon atom out of an ingot! Companies slice thin wafers off using the industrial equivalent of a deli-meat slicer, and the wafers undergo post-treatment to become the solar panels US Republicans love to hate.***
About ten years ago, solar companies would use wafers about 0.33 mm thick (330 microns), and EROEI estimates for solar panels in reasonably-sunny areas were in oil-sands range, roughly 5:1. Today’s photovoltaics are a bit more efficient, and based on wafers about half as thick (180 microns), meaning that for roughly the same starting energy input you can get two solar panels, and thus, twice the electricity. So in the time since George Bush won election 5 votes to 4 in the Supreme Court, solar’s EROEI has doubled to about 10:1. The physical limit is apparently about 20 microns, which two Silicon Valley startups already claim to be able to achieve… if given enough investor money. :) While most startups shut down, solar panels are almost certainly going to get thinner, meaning their EROEI will get better.
On the financial side, the panels aren’t even the cost-prohibitive component of solar arrays anymore: installing rooftop solar in the US will cost you roughly $6/Watt up-front, of which the panel only represents $1. (The rest is associated electronics, and labour.) That’s about double the cost in Germany, whose feed-in tariffs allow for project financing of the rest. This means there’s a big incentive to figure out how to capture more solar energy from a given square metre of rooftop — people with a choice of $6 per Watt or $7 per 2 Watts, are inevitably going to choose the latter, eh?
Into… the third dimension!
Part of the solution will probably be to extend solar panels into the third dimension, in the manner these MIT guys did. It’s a bit like the moment 400 million years ago when the first Cooksonia pertoni told a friend, “I’m tired of competing with lichens and mosses for sunlight in the x-y plane; imma grow me in the z-direction!”
As such, it’s possible that instead of flat slabs, solar-panelled houses of the future will have bristly, antenna-esque solar panels protruding from their roofs — kind of like the branches of trees. The “treeing” of photovoltaic arrays makes sense, since trees have had a zillion generations to figure out how to maximize sunlight collection. Of course you’d figure with all that time, some of them would’ve realized the evolutionary advantage of, oh, being able to move by now… :)
And while such a future would be aesthetically great for those of us who enjoy the look of Gothic churches or Thai wats (Buddhist temples), for minimalists like Steve Jobs on the other hand… ;)
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* that is, unless something destabilizes Qatar or Iran, but c’mon, how likely is that? ;)
** alpha nerds can peruse this link; the rest of you can shake your heads in despair… :)
*** technically speaking, Solyndra was a thin-film solar company using glass substrates, not silicon. But such subtleties are not the stuff of Fox News…