[ExI] Small scale solar payback time (was Re: Planetary defense)

[Damien Sullivan]

On Tue, May 17, 2011 at 06:50:52AM -0700, Keith Henson wrote:
> On Tue, May 17, 2011 at 12:01 AM, Eugen Leitl <eugen at leitl.org> wrote:
> > On Mon, May 16, 2011 at 11:19:37PM -0600, Kelly Anderson wrote:
> >
> >> Ok Keith, I see where I went off the tracks now. You're talking about
> >> ENERGY payback time, and at the time I was thinking about monetary
> >
> > EROEI is always preferable to EPBT. You can have short EPBT at
> > negligible EROEI, e.g. if you use polymer PV which burns out
> > in a couple years.
> 
> If you had a polymer PV that had an energy payback time of a couple of
> months and lasted 2 years, that would be possible to grow energy on

If you had that you'd have EROEI of 48 months / 2 months = 24, pretty
good.
OTOH, if you had payback time of 18 months and lifetime of 24 months,
you'd have EROEI ratio of 24/18 = 1.333.  Pretty poor.

Payback time might matter for speed but you can't ignore EROEI.

Hmm, if something had payback time of 20 years but EROEI of 20 then it
would have a lifetime of 400 years.  This doesn't seem something we have
the luxury of worrying about.

-xx- Damien X-)