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« More on Sapience and Critical Thinking | Main | What Should We Fight to Save? »

March 25, 2010


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George, I think the key question you mention is why decision makers don't know to ask about the values of EROI that are possible. I think the answer is in a similar puzzle. Why is it that economists have known for a long time that profitable efficiencies tend to stimulate resource consumption, not restrain it, and have not mentioned it to either policy makers or the environmental movement?

Both seem to go back to your comments on critical thinking, and my "Wandering minds" model of the barriers between languages. I think the answer is that each social culture develops its own language. Without a way to link people can neither ask or understand answers in the language of another social cultures. It strongly looks to me that the intellectual languages of different social cultures are just not connected. So for "environmentalists" energy saving efficiencies save the earth's resources whether for the "systems ecologists" they physically cause ever faster resource use or not, and the "economists" don't seem to see a reason to mention what they know about it or respond to the questions of either.

People, especially the "..ists" variety, seem to seclude themselves in their own "preferred reality" rather than struggle with the more interesting problem of connecting different conceptions though the natural commonality of referring to the same physical things...

Did I mention my EROI paper, for May's ASME-ES meeting, a method of calibrating whole system EROI measures? fitting right in with what you sketch out above with not much giggering at all I think.

best phil

Larry Shultz

Hi George,
Another worthy posting!
I hope to see some non biased eroei studies on PV, wind, solar thermal and geothermal. Other than run of the river hydro,dams fill up with silt and the energy cost of removing it may be higher than the cost of a new dam. Apparently some dams have been built with faulty figures for lifespan, I believe Glen Canyon to be an example. Do the eroei studies for hydo use real world silt deposit rates?
With fat tail high precipitation events rising i would expect that in a grenhouse world siltation rates will also rise.
I forested environments much of the erosion occurs in about 1 day in 50 years as I recall from the studies done at Hubbard Brook NH. By the way the WMNF forest had the lowest erosion rates of any forest studied up to that point when Pattern and Process in Forested Ecosystems was published.
Climax forest of Sugar Maple, Beech, and Yellow Birch are "wicked" tenacious in their preservation of soil capital.
With a warmiming climate and higher water stress this type of climax forest will be moving north as they cannot stump sprout like oak, or hickory. They are not adapted to fire. The natural fire regime in northen NH is (was?) on the order of 800 years.

Robin Datta

Thanks for a synopsis of what is now burgeoning field of study, of which general public ignorance is slowly waning.

The impression that I had got from The Oil Drum, the Energy Bulletin, etc. has been that the EROEI needed to sustain anything close to BAU is in at a minimum in the high teens.

Yet it would seem that efforts to point the way have not (yet) persuaded us to turn away from the present course: passing SNAFU on the way to FUBAR.


Fascinating post, and I imagine a very difficult subject to get realistic numbers for.

The viability of any particular source of energy must fundamentally be limited by the total amount of energy actually available (amongst other things). David JC MacKay seems to have made a good attempt at realistic numbers in his book Sustainable Energy - Without the Hot Air. Here's an example:

Even if your source of energy has a fantastic EROEI, it may still not be viable if the *total* energy available from it is only a very small fraction of what you need. For example, why have a prodigious effort to cover an entire country in wind turbines if it still only supplies 10% of your energy needs?

Also there is an issue of raw materials. If you need (say) 1,000 wind turbines and maybe a huge pumped storage facility to (hopefully) replace 1 nuclear or fossil fuel power plant, is it even possible to generate all the necessary steel, concrete, electronics and whatever else is needed? At that rate we'd need 120,000 turbines and some huge storage mechanism to supply the UK with electricity from wind, not to mention thousands of square miles to site them all.

It would be nice to think that people in power were actually thinking about realistic numbers but I have my doubts.

George Mobus


Thanks for the link. I will try to get to it by the weekend. I've been unmercifully slammed of late and was lucky to get any posting time at all!

Yes - Jevons' Paradox is virtually unknown by those who should know it. One of the things I've been bogged down with is developing a proposal to improve energy efficiency in buildings (new and retrofit). Asked to participate on a team of proposers. When I mentioned Jevons paradox everyone looked at me as if I were from another planet. They simply (and the government agencies requesting the proposal) assume that if you improve buildings' efficiencies you will automatically take care of a big energy problem.


"Do the eroei studies for hydo use real world silt deposit rates?"

You know in all of the eroei stuff I have looked at I don't remember any studies on dams or transmission lines. But then I haven't actively looked. It's just surprising that such studies wouldn't have fallen into the same venues as all the other eroei studies.

"With a warmiming climate and higher water stress this type of climax forest will be moving north..."

So will I!


"the EROEI needed to sustain anything close to BAU is in at a minimum in the high teens."

I would bet BAU will require more than high teens because it assumes growth-oriented economy. I think we've established a lower bound for a steady-state economy with just development in developing countries spread out over many years in the lower teens. You need aggregate eroeis high enough to handle repair and replacement (maintenance metabolism!) and the larger a population you are trying to maintain in steady state at any given affluence level will dictate what sort of eroei you need. If everyone in the world lived the Northern European lifestyle (on average) it would probably require aggregated stable eroei of mid twenties. That is a reasoned WAG, but a WAG nevertheless. We just don't have good data!!!!


MacKay will be talking at the UW later this month. I plan to go.

I'm not clear on the scaling problem you refer to. If you could build out more source equipment (windmills) and each source had a large enough eroei, how would this not increase the percentage of power supplied unless the population is growing faster than the sources can be installed?

Nevertheless, it does point out that the answers are likely to be counter intuitive. People in the power industry are aware and thinking about this. But they also have to balance that off against the need for quarter-end profits. And if they smell a government subsidy in the wind (no pun intended) they will pursue it regardless of the long-term consequences.



Hi George, and thanks for your interesting comment. Here's another article that explains what I mean:

This argues that the *total* energy that could possibly be extracted from wave and tides is relatively small, regardless of how much technology you throw at it (and how good the EROEI is). In that case is it worth pursuing, even if the EROEI is very good? That's all I was thinking.

George Mobus

Thanks Icarus.

I get your point. It all depends on scale-up potential (only so many tidal basins) and objective (how much BAU do you want to preserve.) I agree.


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George Mobus

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