permaculture

["Kelly Finigan" <kfinigan@spots.ca>]

I think there are a few issues here.

First, a quote from the paper that the NREL info refers to (Alsema 1999):

"Kato (appendix B-8) presented an overview of the work done in Japan on c-
Si, mc-Si and a-Si based rooftop systems. The analysis included the Balance 
of System (supporting structure & power conditioner). The results for 
(current state-of-the-art) monocrystalline-Si based systems depend on the 
choice made regarding allocation of energy to off-grade silicon from the 
semiconductor industry. If off-grade silicon is treated in the same way as 
silicon used in the semiconductor industry, the EPBT of the rooftop system 
would be 15.6 years. If no energy use is allocated to off-grade silicon, the 
EPBT would be 3.9 years (at 1430 kWh/m²/yr irradiation, Performance Ratio of 
0.81). "

What this means is: in the future, maybe at some point, if we do not count 
the energy to purify the silcon for the cells, the payback is 3.9 years. 
Currently though, it is 15.6 years. 

Oh, of course, we have to add some more for the batteries (which wear out 
and go to landfill or maybe can be regenerated using more energy), and a bit 
more for shipping, construction and finally ripping the system apart to 
remanufacture it.

Second issue: the panels generate electricity, but I suspect we need more 
than electricity to make more panels - we probably need process heat and 
organized energy in the form of infrastructure (to drive cars to modern, 
ultra-clean factories to make the panels). Maintaining all this takes 
energy. Also, every conversion of electricity into something else (e.g. a PV 
factory, road, transport system) is accompanied by an (in)efficiency factor. 
If the payback from the PV is even borderline, there is little left over 
(especially once the electric transit bus’s fuel is accounted for) to “run” 
the system to create more panels. 

Seems like PV may be a pretty brief evolutionary attempt. In the big race 
for “future-electricity” champion, I would bet on small hydro, biogas-
fuelled generators and rudimentary wind turbines to outlive the PV (oh, and 
our old friends wood and coal). Right now, I tend to think Holmgren is right 
(at least until the assumption about lower-energy-intensive silicon is borne 
out). 

Kelly


On Fri, 14 May 2004 08:01:43 -0700, jeff wrote
> Holgrem recently wrote about Solar electricity
> and claimed it isn't energy efficient.  This means
> it uses too much energy to build a solar electric
> system.  Over the life of the system it may produce
> less energy than was used in the manufacture.
> 
> In designing our site the two key measurements
> were energy input and material input.  There were
> also some attempts to measure how well we fit as
> humans and our feelings.  I assumed if we did not
> import anything and were happy, then this would
> represent the ultimate sustainable state of being.
> Of course, this is impossible because everything
> on earth is interracting and connected.  But, measuring
> inputs did give a clue about how well our site
> is working.
> 
> If we look at www.homepower.com they claim a solar
> system can produce enough energy to reproduce
> itself in about 2-3 years.
> 
> Who is correct?  Holgram's beliefs come from work
> by Odem which has been difficult for me to follow.
> The data by Homepower comes from government sources
> and others.  They also point out that things are
> changing very fast and efficiencies are improving.
> Another point they make is that the alternatives to
> Solar electricity are much less energy efficient.
> 
> The issue here may be "electricity".  Is any
> form of electricity inefficient or earth
> friendly?  If we want electricity, is solar generation
> acceptable in Permaculture designs or should we
> use wind and hydro?
> 
> I've concluded Holgrem may be on the wrong path here.
> Picking on one form of energy harvesting and saying it
> does not fit permaculture seems premature.  Am I
> missing something?  Is there a better way to view this
> issue?
> 
> jeff
> 
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--
Kelly Finigan, M.Sc. P.Eng. Permaculture Designer
~ Sustainability consultant & ecological designer ~ 

744 - 4 Street NW
Calgary, Alberta T2N 1P2
phone 1-403-283-7270