| Landen99 2005-08-31, 3:21 pm |
| Combustion is the thermodynamic means of a reaction. The energy is
primarily released as heat, a relatively unuseful form of energy.
Chemical reactions can also release their energy electrically; this
form of energy is much more useful for motors/engines. When the goal
is to heat a building, combustion is most efficient. When the goal is
to power a motor, electrical energy is most efficient. Isn't it ironic
that we tend to power our automobile engines with the heat of
combustion and to heat our buildings with electricity (some exceptions
are noted).
There is no theoretical limit to fuel cell efficiency and I stand by
that. The limit on combustion efficiency is derived from the perfect
engine cycle, the Carnot cycle. A lesson on thermodynamics reveals
that the optimization of pressure and temperature swings in an IC
yields the Carnot engine. All other cycles are less efficient
including the Otto cycle (used by cars) and the Diesel cycle (the very
high compression cycle used by diesel engines, of course). Even the
Carnot efficiency can theoretically approach 100% efficiency given
sufficiently high combustion temperatures. Please understand that it
is a little frustrating to hear "what are you talking about" concerning
elementary thermodynamics principles when a simple google search
reveals Carnot efficiency (try those words in the search) in extremely
simplicity: see
http://hyperphysics.phy-astr.gsu.ed...rmo/carnot.html for a fun
and simple Carnot "demo." When speaking with a physicist, challenges
to the most fundamental laws of thermodynamics should be triple
checked.
Oh, and please stop mixing the topics of H2 production and H2
consumption. Please read my "driving my car to work" analogy for
justification that they are essentially unrelated. Just because we
harness dirty, free energy from coal doesn't imply anything about H2.
Draw the discussion line at the boundary between power plants and H2
production because the two are independent of each other. In other
words, power generation does not affect H2 production. The anti-H2
anger is aimed at H2 when in fact it deserves to be focused
constructively on our power plants, a separate and different discussion
forum.
Andy Landen
Physicist and engineer
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