From: ashraf@maccs.dcss.mcmaster.ca (Ashraf Mahmoud)
Subject: Re: Green Coal (:-)
Organization: Department of Computer Science, McMaster University
Date: Tue, 7 Apr 1992 15:55:46 GMT

In article <0dsEs=S00iUxI8ANRx@andrew.cmu.edu> Henry Christopher Frey <hf09+@andrew.cmu.edu> writes:
>In article <1992Mar26.180639.22869@maccs.dcss.mcmaster.ca> 
>ashraf@maccs.dcss.mcmaster.ca (Ashraf Mahmoud) writes:
>
>>...and if you burn it [natural gas] in a furnace you convert considerably 
>>more than 50% of your chemical energy into end-use energy.  QED.
>
>This is apples and oranges.  Paul Dietz explained it in his usual
>elegant way.  Just because the "furnace efficiency" is, say 80 percent"
>does not mean that 80 percent of the chemical energy is converted to
>*useful* end-use energy.  Furthermore, the thermal heat is of very low
>quality.  This is particularly true for space heating systems.  And
>especially so if you spend a lot of energy to heat ducts, the insides of
>walls, and rooms without occupants.     
>
>Cogeneration systems can also be designed to get very high thermal
>efficiencies.  However, even this is somewhat meaningless, because the
>quality of electrical energy is much higher than that of the thermal
>energy associated with steam.
>
>Conversion of over 50 percent of chemical energy in a fuel to
>electricity is a big deal.  There are a lot more ways to efficiently use
>electricity than there are to efficiently use low quality thermal energy.

Why is this apples and oranges?  On the input end you have a given quantity of
natural gas.  On the output end you have a house to be heated.  Using the SAME
house with the SAME ducts and using the same size fan, etc., is it or isn't it
better to burn the gas in the furnace than in a gas turbine, convert the heat
and pressure to mechanical energy and then to electricity, and resistively heat
an element?

I don't want to hear about fancy heat pump arrangements, since the plans for
natural gas-generated electricity in Ontario do not include retrofitting the
province with heat pumps.

>>It's a greenhouse gas nonetheless.  Personally I don't buy the Global Warming
>>Pseudo-Theory, but if you do, you shouldn't put natural gas above nuclear 
>>(which was my original point). 
>
>This again is apples and oranges, and you apparently missed, or
>completely ignored, my previous point.  Look, one *can* buy into the
>global warming theory and also buy into the notion that waste products
>and risks associated with nuclear are also a major problem.  These are
>two different problems, both of which could be simultaneously important.
> They are also measured by different attributes.  Thus, it is not
>necessarily the case that nuclear wins out over natural gas -- you have
>to consider the risks from both global warming and those associated with
>nuclear power to make such a conclusion -- you have to convert the
>vector of risks associated with both, which are different, into some
>common scalar measure of risk, before making a comparative judgment. 
>And the fact is that natural gas is less harmful than some other fossil
>fuels, which makes it relatively attractive.  That is my point.  Too bad
>that globally so much natural gas is wasted at oil fields, rather than
>put to productive use.
>
>Chris Frey

Point taken.  In my original posting I was naming things off the cuff that 
I didn't like about the increased plans for natural gas in this province, 
and being a greenhouse gas was one of them.  My main point was that it is a
very limited resource, for which the generation of electricity appears to
be a relatively inefficient end use.  That, of course, takes us back to the
first argument above.

Jeremy Whitlock              "My thoughts are mine, not Mac's"
Dept. Engineering Physics
McMaster University, Hamilton,Ont.
WHITLOCK@MCMASTER.CA
Newsgroups: sci.energy