[Marxism] privatizing the grid--a local perspective

Rod Holt rholt at planeteria.net
Tue Feb 7 10:32:18 MST 2012


(re. DW's comment)
My hot water heater is not a metaphor. It is a counterexample.
cmd. Ehbar used the example of the hot water heater. I understood that a hot water heater could run with natural gas as an energy source or with electricity as its energy source. He stated that such a device running on gas wasted 95% of the energy. But Ehbar used the term "exergy", with the parenthetical proviso that exergy was "available energy". It was this statement that I took exception to. The (domestic) hot water heater is not a metaphor; for my purpose, it is an appliance. 

As an appliance for heating water, some may do a better job of it than others. For a given amount of hot water, some may use more gas than others. To make this notion concrete, we can talk of "efficiency" with a definition yet to come.

"Exergy" is not to be found in Webster's International Dictionary (Third Edition) as of 1993, the date of my copy. It is not to be found in Richard Feynman's *Lectures on Physics*. "Exergy" can be found in Wikipedia, however. What does Wiki say about exergy? Oddly enough, the discussion is confusing. I guess the motivation for using the term exergy is to avoid using the term entropy. But avoiding entropy leads to thinking errors with mathematicians and physicists in that exergy is not energy. Said directly, "The exergy of a system in equilibrium with the environment is zero. Exergy is neither a thermodynamic property of matter nor a thermodynamic potential of a system. Exergy and energy both have units of joules." (from the Wiki article on exergy). Whereas energy cannot be destroyed in the world of physics, exergy can easily be destroyed. In the world of academic ecology, joules can disappear!

For example:
In the Wiki article on "exergy efficiency", we find in equation 1) B is joules.
B(in) = B(out) + B(lost) + B(destroyed)  Some quantity of exergy is allowed to be destroyed. What do we learn here?

Now, you and I might think cmd. Ehrbar is talking the same language as everyone else, but he is not. Still and all, if I want or need hot water, I know how to get it with squeezing every last BTU out of the next fart.
 


On Feb 7, 2012, at 7:07 AM, DW wrote:

> Of course Rod' use of the shower metaphor was just that, a metaphor.





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