On Sun, 25 Jul 2010 16:38:02 -0500, cavelamb
wrote:

wrote:
On Sun, 25 Jul 2010 11:16:30 -0700, Steve Ackman
wrote:


It takes a LOT of energy to produce PV panels. From
what I've read,

Let's see the cite. 'Cause I've read that Elvis is alive, working at
7-eleven by day, and posting to usenet at night. :-)

a PV panel will never make up the
carbon it cost in its expected 25 year life span.

This study says 3 years for energy payback.
http://www.nrel.gov/docs/fy04osti/35489.pdf

That didn't look like MANUFACTURING payback, just purchase cost payback

I don't know what the heck you're talking about. The chart on the
first page is clearly titled "*energy* payback of rooftop pv systems".
The first paragraph explains that it takes energy to build the
product, and the summary of data says that the product makes more
energy in a small percentage of its lifetime than was required to
create it. NREL says up to 3 years, while some others rate it in
months, depending on the variables. People who pretend that PV
consumes more energy than it produces are promulgating a long-debunked
myth.

This one says 6 years for
carbon payback. http://eprints.ucl.ac.uk/2642/1/2642.pdf Both numbers
expected to improve substantially.

Wayne!
You might want to read that one again...
It said "
The carbon payback for solar thermal system is 2 years,
the BIPV system has a payback period of 6 years.

??? There seems to be an echo in here. :-)

Simple economic payback for both systems is over 50 years(!)

That wasn't at issue here. But simple economic payback for most of US
is much shorter, some people report only a few years in good-sun, high
utility-rate areas. In low-sun, low-rate areas, there is no simple
payback, especially since we're fine with putting off the cost of so
many things onto future generations, and hence frequently exclude
obvious outside costs. For example, if you believe that PV is
expensive, then think about how much of our healthcare costs are the
result of pollution from power production. Too much work? Then see
here http://www.usdebtclock.org/ for a partial tally of how well that
"easier for someone else to pay later" strategy is working out.

At no time did they say anything about MANUFACTURING payback!

Page 4, table 1. Note "embodied energy and carbon". How do you
imagine that those get into the product? See here for more details and
references. www.ongrid.net/papers/PVvsInputEnergySWCph.pdf

Wayne