Re: Solar-hydrogen home power system?

From: Ray Drouillard (cosmicpam2_at_comcast.net)
Date: 10/18/04 

Date: Sun, 17 Oct 2004 23:12:29 -0400

"Don Lancaster" <don@tinaja.com> wrote in message
news:41731A97.1595A9EC@tinaja.com...
> Glenn Martin wrote:
> >
> > "Don Lancaster" <don@tinaja.com> wrote in message
> > news:4172DB18.722DAB97@tinaja.com...
> > >
> > > Solar pv electricity is ridiculously too valuable to waste on
hydrogen
> > > generation.
> > > The system would be a net energy sink and a net destroyer of
gasoline.
> > >
> > > See http://www.tinaja.com/glib/energfun.pdf
> > >
> >
> > Don, I'm confused here. Surely a method of storing excess power
> > generation makes more sense than letting the daylight go to waste.
>
> Not when most of the value of the excess power is instantly destroyed,
> as irrevocably happens during electrolysis.
>
> Most PV
> > battery systems lose charge in relatively short order. A properly
sealed
> > hydrogen tank should hold its' contents for months if not years.
This would
> > allow you to 'store sunlight' as it were in the long days of the
summer to
> > fill out the short days of the winter.
> > ....and it could fuel leaf blowers!
>
> Such a tank would cost far more than the energy value of the hydrogen
it
> was holding.
> A net energy sink is guaranteed.
>
> Energy density of STP hydrogen is 2.7 watthours per liter.
> Energy density of gasoline is 9000 watthours per liter.
>
> >
> > Glenn Martin
>
> The value of a kilowatt hour of electicity is ridiculously higher than
> the value of a kilowatt hour of unstored hydrogen gas. Because of a
> fundamental thermodynamic property called "exergy", most of the value
of
> the electricity is instantly and irrevocably destroyed during
> electrolysis.
>
> Electrolysis is exactly the same as 1:1 exchanging US dollars for
> Mexican pesos. It is wildly and laughingly unsuitable for high value
> electrical sources such as grid or pv solar.
>
> Electricity NEVER gets cheap enough for electrolysis to make sense for
> bulk hydrogen energy aps.
> There ALWAYS will be more intelligent uses for the electricity.
>
> Synchronous grid storage is by far the most cost effective pv method
> today.

Or, you can pump a bunch of water uphill, and use an old-fashioned
waterwheel to get the energy back at night. That method, while it lacks
portability, can be reasonably efficient.

I briefly looked through energyforfun.pdf, and it looked interesting --
but I didn't find the actual efficiency of electrolysis. In any case,
multiply that by about 0.65 (the efficiency of a decent fuel cell), and
factor in the energy needed to store the hydrogen (sneaky stuff), and
any losses, and you end up with a system that will require several KWH
of work to yield one KWH of output. There has to be a better way than
that. In fact, off the top of my head, I can think of a few.
Compressed air tanks and hydraulic accumulators can be used. The
technology is mature and the efficiency of each step is in the 90%+
range.

Don't get me wrong -- I like hydrogen enough to have studied it a bit.
It has many advantages, but also many disadvantages. It has lousy
energy density (volume wise), is difficult to store, and likes to leak
right through the walls of pipes. As far as danger -- well, it's about
as dangerous as propane or methane. It has a lower energy density and
tends to float away. On the other hand, you can't see the flame, so
it's really easy to be in trouble before you know it.

If it can be produced cheaply (off-shore nuke plants splitting water,
for instance), and we develop some decent plumbing that'll contain the
stuff, it wouldn't be a bad replacement for home heating and the like.
Using it to power a car makes slightly more sense than putting batteries
in an electric car. I haven't run the numbers, but I suspect that you
can get more than the fifty or 100 miles per 'thankful that the best
electric cars enjoy -- and you can fill it up in minutes instead of
charging it for hours. Still, gasoline, propane, or methane work
better.

Want cheap fuel? Shovel a bunch of organic sludge into an air-tight
container, keep it warm, and let the bacteria make methane for you.
There are some engineering details to work out, but not as many as for
hydrogen storage and transport.

Ray Drouillard

Relevant Pages

  • Green Hydrogen Production: A Work in Progress
    ... Green Hydrogen Production: A Work in Progress ... Managed by the U.S. Dept. of Energy (Washington. ... cells as the enabling technology," says Chalk. ... electrolysis or by employing other water- splitting techniques. ...
    (misc.invest.stocks)
  • Re: Solar-hydrogen home power system?
    ... >> Not when most of the value of the excess power is instantly destroyed, ... >> as irrevocably happens during electrolysis. ... The definition I like is that exergy is energy you can use. ...
    (sci.energy.hydrogen)
  • Re: Solar-hydrogen home power system?
    ... >> Not when most of the value of the excess power is instantly destroyed, ... >> as irrevocably happens during electrolysis. ... The definition I like is that exergy is energy you can use. ...
    (sci.energy)
  • Re: water as fuel
    ... gasoline doesn't explode in an engine -- at ... says nothing about the energy content of gasoline. ... Except that electrolysis may not be the most effic- ...
    (alt.autos.toyota)
  • Re: HHO kits
    ... These kits are fitted to existing engines and electolyse water using ... There is serious research going on with this technology, with a view to developing new designs of engines that can fully exploit it, which would seem to me to be a much better idea than trying to retrofit stuff to existing engines not designed for it. ... the electrolysis of water, a process that must be powered electrically.. ... The hydrogen or oxyhydrogen is then burned, supposedly powering the car and also providing the energy to electrolyse more water. ...
    (uk.rec.cars.maintenance)