[ExI] EROEI

[Keith Henson]

On Fri, Apr 29, 2011 at 4:29 AM, Eugen Leitl <eugen at leitl.org> wrote:
> On Thu, Apr 28, 2011 at 06:33:17PM -0700, Keith Henson wrote:
>> On Wed, Apr 27, 2011 at 7:30 AM, Eugen Leitl <eugen at leitl.org> wrote:
>>
>> snip
>>
>> > EROEI of 40:1, and still climbing. Grid parity coming
>> > soon.

Over what period of time?  If it last forever, then the EROEI is infinite.

>> I don't think EROEI is a good metric in all cases.
>
> In case of energy production systems you will be looking at ROI,
> EROEI and ecosystem impact. The cutoff for practical EROEI
> is estimated to be at 5:1.
>
> http://www.theoildrum.com/node/3786

http://www.drmillslmu.com/peakoil.htm

Even more detailed discussion here.
>
>> For example, suppose you had a way to make energy that cost 80,000 kWh
>> to make a steady 1 kW but would do so for 100 years (some RTG might be
>> in this class).  At the end of 100 years, you have an EROEI of 10
>> times, but it takes ten years just to pay back the energy that was
>> invested in making it.
>>
>> Easy oil fields have a very high EROEI, typically 300 to one.  Most of
>
> My sources say 100:1 for 1930s domestic oil. It's now down to 10-15:1.
> http://www.theoildrum.com/story/2006/8/2/114144/2387
>
> Not only can supply rate (declining) match demand rate (increasing),
> to does that at precipitously declining EROEI. This is true for all
> nonrenewable sources. That is what makes peaking resources even
> worse than they look superficially.

Complete agreement.  We are headed for or already may be in a
collision between supply and demand.

>> the oil is pumped out in ten years, with the majority of it in the
>> early years, but even for linear production, they payback is 30 to one
>> in the first year or an energy payback time on the order of ten days.
>
> We no longer live in the land of milk on honey, if we ever did.
>
>> The energy payback for solar cells may have come down by now, but it
>> was in the years not long ago (of course that depends on where you put
>> them too).
>
> ...
>
>> Worse than oil, but about ten times as good as ground solar or wind.
>
> Terrestrial thin-film PV is on a track to cross over with dirty
> coal reasonably soon, which is the "cheapest" source of energy.

In the long run, that's almost certainly true.  But sunlight is a
really dilute energy source.  You need to cover an awful lot of land
that with manufactured stuff.  Now give nanotechnology, it's no
problem but before that, well, if the PV was *free* I don't electric
power would come down to much less then 5-10 cents per kWh, before you
move it to places that need it or convert it to liquid transportation
fuels.  10 cent power corresponds to $210/bbl synthetic oil.  (Ten
dollars of capital and $200 of energy input.)

> I don't think we'll
> see much SPS presence any sooner than 2050-2060.

If it takes that long, I doubt we will see it at all.  That's probably
post singularity.  I expect the singularity to be accompanied by a
precipitous fall in energy demand per capita.  The advanced countries
use on the order of 10kW per person.  It would take about 1% of that
to power them directly and 1/5 of a percent to run the brains alone.

> By that time,
> the reason we will have to use SPS is not because it's cheaper, but
> because we've ran out of easy terrestrial flux to tap (though
> http://www.altestore.com/howto/images/article/world_solar_insolation_data.gif
> shows you great areas of high-insolation surface with only
> thin (desert) ecosystem present, if one is willing to transport
> energy/synfuels over large distances, though vulnerable bottlenecks
> (pipelines/HVDC). This is not where the strength of decentral energy
> sources is -- it's absence of control monopolies and no transport
> losses/no extortability.

If anyone builds power satellites at all, they will be built by the
thousands and owned by every country on earth.

Keith