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  • From: dwoodard@becon.org
  • To: permaculture <permaculture@lists.ibiblio.org>
  • Subject: Re: [permaculture] Solar Electric Confusion
  • Date: Fri, 14 May 2004 13:37:51 -0400 (EDT)

Howard Odum's "emergy" concept said that the solar cost of oil is the
amount of solar energy that went into growing the organisms nned to
produce the oil that came down to us. He assumes that the energy needed to
produce say solar cells comes from oil.

Now, this emergy concept is interesting, but I'm not at all sure what it
is good for. It particular, I'm not sure that it is any use for evaluating
the viability of devices for capturing solar energy directly.

Also, Odum assumed that not only production energy costs were to be
atributed to solar cells etc., but also all the consumption energy costs
of the workers who produced them all along the production chain - i.e.
the gasoline consumed by the SUVs they drive to work and the energy needed
to buil the SUVs etc., etc.

Odum's calculations could lead to the conclusion that it would be sensible
to buy solar cells from Bangladesh to install in Florida, but it would
make no sense to install US-made cells in Florida. That is, the more you
need them the less sense it makes to use them.

While Odum's method might correctly suggest that a solar-based economy
cannot support the current U.S. urban industrial lifestyle, I don't think
it has any validity in concluding that no solar based economy is feasible.

I think myself that Odum was over attracted by sweeping generalizations.
he also claimed backing for him conclusions by some studies which are not
accessible in the scientific and technical literature, as you will
discover if you try to track down his references.

Doug Woodard
St. Catharines, Ontario, Canada



On Fri, 14 May 2004, 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.
>
[snip]

> 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.

[snip]




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