[Marxism] privatizing the grid--a local perspective

Robrecht W. Uyttenhove ruyttenhove at gmail.com
Wed Feb 8 09:47:35 MST 2012


Hans,


I don't want to speak in Rod's name but I think Rod's argument is as follows.
1.In the case you burn gas in loco to heat water, the internal energy
(dU) is completely released as heat (dq) (assuming no e.g. PV-work  is
performed dw=0): => dU=dq
If we have a process where the pressure (P) is constant and no PV-work
is done then dU=dH (H=U + PV)
(H stands for the enthalpy and is a very useful thing if you calculate
the heat of combustion)

2.In the case you use gas to generate electricity you will use part of
the internal energy (dU) to do electrical work (dw).
And because you don't work at T=0. Kelvin, part of the internal energy
will be 'wasted' as heat to the environment (Carnot efficiency < 1.)
In a second step you will do the same thing as Rod in step 1. but
instead of using chemical energy (combustion) you will be using
electrical energy but you still have an extra step in which you have
to convert chemical into electrical energy.

However, I think that the confusion comes from a different 'length scale'.
Hans thinks on a wider societal approach i.e. how energy is created on
a wider scale. Rod focussed on the efficiency of burning natural gas
in loco.
The conclusion: in thermodynamics we always have to delineate the
system and its environment. Both comrades have been talking about
different systems.

Concerning exergy. I never seen the concept in physics books which
discuss thermodynamics
e.g. Landau & Lifshitz (Course of Theoretical Physics Vol. 6)
      W. Greiner (Classical Theoretical physics - Volume
Thermodynamics and Statical Mechanics)


Best regards,

Robrecht



On Tue, Feb 7, 2012 at 7:40 AM,  <ehrbar at greenhouse.economics.utah.edu> wrote:
> ======================================================================
> Rule #1: YOU MUST clip all extraneous text when replying to a message.
> ======================================================================
>
>
>
> Rod, maybe the following metaphor will help.  Using natural
> gas to heat water has been compared to using antique
> furniture as firewood in your fireplace.  Of course antique
> furniture burns well, it is very dry etc., and your detailed
> example shows how well it burns.  But if you need firewood
> there are so many other possibilities that it is unwise to
> sacrifice your antique furniture for it.  That was my point.
>
> You quoted the following passage from me and said it contained
> "a host of errors":
>
>> "if you use natural gas to heat water for a shower, you
>> are wasting 95% of the exergy, i.e., available energy.
>> You should use the gas to generate electricity and the
>> waste heat from this electricity generation for your
>> shower."
>
> I stand by this quote, I see no errors in it.  I would be
> grateful if you explained what is wrong with this paragraph.
>
>
> Hans
>
> ________________________________________________
> Send list submissions to: Marxism at greenhouse.economics.utah.edu
> Set your options at: http://greenhouse.economics.utah.edu/mailman/options/marxism/ruyttenhove%40gmail.com




More information about the Marxism mailing list