[ExI] Wash post comment

[Keith Henson]

On Sat, May 19, 2012 at 2:59 AM,  Jeff Davis <jrd1415 at gmail.com> wrote:

snip

> And on my own, I find this EROEI business a bit suspicious. I wonder
> if it's just an artfully authoritative-sounding but irrelevant
> "metric".

No, it is a real problem.  Sets the lower limit on what is useful.
It's not hard to explain in a real world model

For simplicity, imagine a village that can't be moved due to a
resource like water and a food supply that is some distance away.
Long as the walk to the food source takes a small fraction of the time
the villagers have available, all is ok.  But as you move the food
source (call it manna) further and further away, it takes more and
more of the caloric value in the food to go get it.  Eventually it
takes more to get the food than it contains and the village starves.

That's the situation with oil, there is still a lot of oil out there,
but it's getting harder to find and harder to extract.  Eventually it
will take more energy to get it out than it is worth, in which case we
quit using oil.  Because oil is mostly used for transport, that has
big effects as does the use of oil in farming.  I.e., run out of oil
and people die, lots and lots of them, at least if we are using
current technology.

> On Wed, May 16, 2012 at 11:08 PM, BillK <pharos at gmail.com> wrote:

snip

>> Wind and other renewable energy sources offer returns in the 17:1
>> range ? still a nice income flow, but nothing like the flood we once
>> got from oil.

For extraction over a relatively short term, EROEI is a good metric.
A more useful one for renewable energy is energy repayment time.  For
solar or wind this is in the 1-2 year range.  That sets a slow
doubling time for these technologies to get us out of the use of
fossil fuels.   For power satellites the energy repayment is under two
months.

But what's the chance of that happening?

Keith