Bill Hooper wrote "The electrical energy produced is invariably less than the chemical energy in the original coal (usually a max of about 33%). If that electricity is used to heat a home, one could argue that it would be more efficient (3 times as efficient) just to burn the coal in the home producing heat in the home directly from the burning process*"
Is this really true, then why do the automobiles run at 35 - 40 % efficiency. After all they convert heat energy directly into mechanical energy. I believe that lot of heat escapes in the form of hot gases which can never be trapped. As for Ethanol's efficiency, there is some argument that ethanol from genetically modified Corn will give more net energy. The plants get lot of energy from Sun (through photosynthesis). Let us wait and see. Meanwhile the big 3 (GM, Ford & DC) produce vehicles running on ethanol as well. Madan --- Barbara and/or Bill Hooper <[EMAIL PROTECTED]> wrote: > Date: Sun, 31 Mar 2002 20:06:59 -0500 > Subject: [USMA:19189] ethanol production > From: Barbara and/or Bill Hooper > <[EMAIL PROTECTED]> > To: "U.S. Metric Association" <[EMAIL PROTECTED]> > Reply-to: [EMAIL PROTECTED] > > on 3/28/2002 5:14 PM, Louis JOURDAN at > [EMAIL PROTECTED] wrote: > > ... a bad process (I mean ethanol production) > > in reply to this comment in a previous message: > >> ... the energy cost of producing ethanol > >> exceeds the energy in the ethanol. > > Of course the energy is less. That's a natural > consequence of the second law > of thermodynamics. That does not necessarily mean it > is a bad process. > > Surely we should be concerned about such a process > in a world running low on > energy, but there are other aspects of energy use > that are also important, > in addition to the amount of the energy alone. > > Take for example a pile of coal which may be burned > to produce electricity. > The electrical energy produced is invariably less > than the chemical energy > in the original coal (usually a max of about 33%). > If that electricity is > used to heat a home, one could argue that it would > be more efficient (3 > times as efficient) just to burn the coal in the > home producing heat in the > home directly from the burning process*. > > But what if that electricity is used to operate a > television set? There is > no way that the television set can be operated on > the chemical energy in the > coal or the heat generated simply by burning it. The > conversion to > electricity was necessary even though it resulted in > a smaller amount of > energy than the energy that was in the coal to begin > with. > > Of course, all such situations need to be analyzed > more thoroughly to decide > if the net value of the energy is worth the loss in > the conversion process. > I'm not suggesting that the example of ethanol > production is good. I am just > saying that the decision as to whether or not the > ethanol process (or any > other example) is good or bad cannot be determined > quite so simply as just > checking the energy out compared to the energy in. > > There are always two sides to an issue ... maybe > three ... or more. > > Regards, Bill Hooper > college physics teacher (retired), USA (Florida) > > * Even that example (burning coal to produce heat > which is used to produce > electricity which is then used to produce heat in > the home) can be justified > by such factors as the danger of burning coal in the > home (fire, carbon > monoxide, etc.), the dirty smoke from home type coal > burning, the energy > cost of transporting heavy coal to the home as > opposed to tranporting > weightless electrical energy to the home, etc. > > +-+-+-+-+-+-+-+-+-+-+-+ > Do It Easy, Do It Metric! > +-+-+-+-+-+-+-+-+-+-+-+ > __________________________________________________ Do You Yahoo!? Yahoo! Greetings - send holiday greetings for Easter, Passover http://greetings.yahoo.com/
