eugen at leitl.org
Fri Apr 29 11:29:52 UTC 2011
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:
> > EROEI of 40:1, and still climbing. Grid parity coming
> > soon.
> 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.
> 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.
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.
> 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. I don't think we'll
see much SPS presence any sooner than 2050-2060. 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
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
Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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