Re: Engineering Economics 101, example II...

"Don Lancaster" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
>...
> Only when you get down around a dime per peak watt (starting with $10
> per day and ending up with $100) does pv solar become a truly renewable
> and sustainable source.

This assumes rather boldly that the price of the hardware is intimately
connected to the value of the electricity produced. There are several strong
disconnects that make this assumption quite questionable. All that is
necessary to make solar PV a sustainable source is that a typical unit of PV
(including all the support hardware, transportation, assembly, etc.) at some
ideal location produce as much energy over it's life as was consumed to
build it. This gets sticky because much of the energy consumed is not
normally electric and this makes a lot of difference for chemical processes
like the production of steel (which usually uses a lot of carbon), and
transportation fuels. But one could design, at least in concept, an energy
system based on any system with a return of just a bit more than 1.00. By
comparison, we might want to consider the use of plant oils, where as little
as 2-3% of the solar energy is captured, although the system does produce
and maintain itself with little direct human support. Seems to me I recall
some estimates for some biological systems like this had a return of 1.2 or
so, which is really pretty bad. The solar return, per year, seems to be
closer to 0.5, which is really pretty poor, although the lifetime suggests a
total return of more like 10-20, it does tie up a lot of real-estate and a
lot of hardware to get this. The low return per year strongly limits the
growth rate for any solar only system to something like a doubling every 4-6
years, depending on how much power has to be provided to the community out
of that produced.