Re: Solar-hydrogen home power system?

From: Don Lancaster (don_at_tinaja.com)
Date: 10/20/04 

Date: Wed, 20 Oct 2004 08:19:42 -0700

Glenn Martin wrote:
>
> "Don Lancaster" <don@tinaja.com> wrote in message
> news:4175DF4C.6B1FB4D5@tinaja.com...
> >
> > Exergy is a measure of the thermodynamically reversibly recoverable
> > energy fraction.
>
> Don, what does this mean? What is an enrgy fraction? What does "reversibly
> recoverable" mean?
>
> Why do you apply "amortization"; a financial term, to physical measurements
> of energy conversion efficiency?
>
> Glenn Martin

This is all carefully explained in
http://www.tinaja.com/glib/energfun.pdf
Or http://www.tinaja.com/glib/hack64.pdf for a thermodynamics intro.

A reversible thermodynamic process kicks off zero unrecoverable low
grade heat.
If you go electricity ---> room heat ----> electricity, you get
virtually none of your electricity back because Carnot's Law prevents
even a theoretical low delta-T recovery of more than a percent or two.
Going electricity ---> hydrogen ---> electricity is considerably WORSE
than this today.

Exergy is the measure of this fraction and thus the energy value. If you
can convert the present energy form into another and back again with
most of it left, you have high exergy. If not, you have low exergy or
(in the case of hydrogen) negative exergy.

Exergy is also easily quantifiable. The Gibbs Free Energy is one
pre-amortization measure that applies to certain classes of fuels.

The amortization directly enters into the recoverable energy fraction
you can get back.
If you get back two cents worth of electricity and the interest on the
system is three cents, you have a net energy sink and are destroying
gasoline.

The equivalance between dollars and energy can be observed by the large
sign out front that says UNLEADED $1.97. Ultimately all of economics is
dictated by the underlying net energy sources.

Yes, if the price of gas goes up, the exergy of hydrogen goes down.
That is the beauty of exergy. It tracks the true costs of reversible
fraction recovery.

See http://www.fes.uwaterloo.ca/u/jjkay/pubs/exergy/ for an independent
tutorial.

There are also something like 17,000 Google hits on exergy.

Exergy is THE measure of the competitive viability of an energy delivery
system.

And positively, emphatically, and absolutely GUARANTEES us that
electrolysis from high value grid or pv sources for bulk hydrogen energy
flat out ain't gonna happen. 

-- 
Many thanks,
Don Lancaster
Synergetics   3860 West First Street  Box 809  Thatcher, AZ 85552
voice: (928)428-4073 email: don@tinaja.com   
Please visit my GURU's LAIR web site at http://www.tinaja.com

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