|
|
"Fred McGalliard" <frederick.b.mcgalliard@xxxxxxxxxx> wrote in message
news:IJ5xL5.n1L@xxxxxxxxxxxxxxxxxx
>
> "Don Lancaster" <don@xxxxxxxxxx> wrote in message
> news:3imcvbFma7u2U1@xxxxxxxxxxxxxxxxx
> ...
>> Silicon pv is the wrong horse to bet on because of its horrible
> inefficieny.
>
> Nonsense Don. The problem is not inefficiency, it is installed cost per
> delivered KWH. You need cells that can be ganged together cheaper. Imagine
> something like a self assembling micromachine that you could spread out
> like
> cloth, with a DC/AC inverter built in, perhaps? I'll take 6 yards of that
> please, in light green, and 100 feet of 600V power cord.
>
>
> #! rnews 1669
> Xref: xyzzy sci.energy.hydrogen:81675
> Newsgroups: sci.energy.hydrogen
> Path: xyzzy!nntp
> From: "Fred McGalliard" <frederick.b.mcgalliard@xxxxxxxxxx>
> Subject: Re: Cost of Generating Hydrogen Through Electrolysis
> X-Nntp-Posting-Host: e056750.nw.nos.boeing.com
> Message-ID: <IJ5xvv.93@xxxxxxxxxxxxxxx>
> X-Mimeole: Produced By Microsoft MimeOLE V6.00.2800.1441
> X-Priority: 3
> X-Msmail-Priority: Normal
> Lines: 20
> Sender: nntp@xxxxxxxxxxxxxxx (Boeing NNTP News Access)
> Organization: The Boeing Company
> X-Newsreader: Microsoft Outlook Express 6.00.2800.1437
> References: <42c0ca69$0$62507$892e7fe2@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
> <3ic2ceFkv8igU1@xxxxxxxxxxxxxx> <11ce6ob67luvuf4@xxxxxxxxxxxxxxxxxx>
> Date: Tue, 5 Jul 2005 16:31:06 GMT
>
>
> "charliew2" <charliew@xxxxxxx> wrote in message
> news:11ce6ob67luvuf4@xxxxxxxxxxxxxxxxxxxxx
> ...
>> > The concept of electrolysis is thermodynamically ludicrous.
>>
>> Apparently, you're wasting your time typing the same stuff, Don. It
>> seems
>> that many in this NG do not understand thermodynamics and don't have the
>> desire to try to understand it.
>
> Charlie. Don't fall into the trap Don has fallen into. Thermodynamics
> plays
> a very interesting trick on electrolysis, one worth studying a bit. It
> does
> not condemn the process but does place a constraint on it. The killer, as
> Don has pointed out correctly, and which you should keep in mind, is that
> relatively inexpensive electrolysis is very energetically lossy. How about
> we build some good electrolyses with 90% efficiency first, then we can
> discuss the thermodynamics in more detail. Until we can do that, the
> thermo
> is not even worth discussing, and Don get's it fundamentally wrong anyway.
>
>
OK - I'll even try to avoid a new trap. From a thermodynamic viewpoint,
EVERY practical process is irreversible, meaning that all processes have
less than 100% efficiency of converting energy from one form to another.
Some processes have much lower conversion efficiency than others.
"Reasonable" conversion efficiencies are probably in the range of 20-40%
(e.g., most of the energy of gasoline gets wasted as heat rejection to the
environment). Even assuming an overall conversion efficiency of 50%, it is
obvious that you want to absolutely minimize the number of energy
conversions that you go through. This means that if you have "spare"
electricity, you want to use it directly. Using it for electrolysis, then
hydrogen compression or other storage, then running it through a fuel cell
to regenerate electricity, then using that electricity to power an auto,
involves way too many energy conversion steps.
Even if you can get to 90% electrolysis efficiency, you still need to
process the hydrogen in order to store it, and you have to run it through a
fuel cell to generate electricity, then use the electricity to power an
auto. All of the energy conversion steps besides electrolysis also need to
be very efficient if this scenario is going to be more efficient than
current internal combustion engines. Of course, I'll admit that this may be
achievable because of the very low automobile efficiency guessed at above,
but it is by no means guaranteed.
|
|