permaculture

[jeff <jko@bsn1.net>]

On Wednesday 26 May 2004 10:35 pm, Kelly Finigan wrote:
> 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.

This looks like useful data but I'm still struggling with all
the assumptions present.  For example, the above data only
looks at one type of solar cell.  It doesn't factor in time and
the possibility of future improvements.  Yet another, problem
is that some cells are constructed from recycled silicon 
rejected by the semiconductor industry.   Another big problem
is climate and location.  Was the above data for
summer in a northern latitude?  Given all the variables we probably
need a few graphs to see cell performance and manufacturing
energy costs.  How we factor recycling into all this is another
puzzle. 

> 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.

In this area batteries can be recycled and are optional for many
applications.  We have the choice of utilizing DC directly or
using the grid as a battery.  Still, most applications do utilize
an inverter along with batteries.

I've been running a typical solar setup with batteries and inverter
for about 12 years, and may transition to a DC system.  The batteries
are definitely a weak point in solar cell energy systems.  When I
look at all this from the Permaculture perspective, there is a design
shift towards DC applications and a mix of energy sources.  This
may be the answer.  Look at each site and stay flexable. 

> 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.

True, we may conclude that PV should not be used for transit applications
and encourage local manufacturing.  This transport issue is much bigger
than just PV manufacture.  Anyone who travels by air is wasting energy at
a outrageous rate.  The energy from one plane trip probably could power a
PV factory for several years.   

> 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).

In the desert the local energy source will proably be solar.  No hydro,
biogas, wind, or wood.  There may be some wood or coal for a
small population, but both wood and coal can become serious
pollution problems if not restricted.  In this area we have lots of
wood but it does not produce electricity very well.  If we do utilize
coal or oil the question might be:  Is it less expensive to transport
solar cells or oil/coal? 

I'm now thinking that anyone who drives a gas eating vehicle
has diverged radically from the concept of sustainability and
probably from the Permaculture ideal.  Given that we have
already made this compromise, it is difficult to be a purist
about something like solar cells.  The occasional truck can
sometimes be seen in Permacutlure publications, which probably
says something about his issue.

jeff