On Thu, Sep 07, 2006 at 01:42:34AM +1200, Russell McMahon wrote:
> >> I've long thought that a home "gasometer" system should be viable -
> >> miniature version of those used here for coal gas in days of yore. 
> >> .
> >> Electrolyse water to Hydrogen and store enough for a few days 
> >> heating demand. 

Interesting idea. It's little more that a couple of electrodes in water.
Any ideas what kind of loss you get in doing the conversion back and forth?

> The following calculations (E&OE) suggest that a 2m tall x 2m diameter
> tank (6 m^3) will store about 20 kWh of Hydrogen at essentially zero
> pressure.
> That's $NZ2-$NZ3 worth at present.  If you halved power costs due to
> night store supply and cycled this daily thats an annual 'saving' of
> around $NZ500 per year.

Now you're talking! I'm on a peak time of use plan. Cheaper in the winter.
Cheaper in the summer during off peak. Expensive (20 cents USD/kWh) during
peak time. Close the 2.5x the off peak price. Considered time shifting with
batteries, but it's an expensive proposition.

> You'd have to have economies of scale to make
> that worthwhile - would probably support a $2500 - $4000 range price
> tag all up. Done on  a very large scale this would help delay power
> line upgrades and would thus have further economic benefits.

Let's talk about one offs. The objective is cooling. So I see the cycle as:

1. Convert off peak power to hydrogen and store.
2. In peak time, burn the hydrogen either to produce electricity for cooling
or use the heat to drive a ammonia or Einstein cooling system.

Obviously all of this can be supplemented with solar heat/electricity. The
hydrogen can act as a buffer on the vagaries of solar.

Now if one off is the objective, how would one accompish these tasks? Here's
a bunch of questions.

1) Can hydrogen be stored in a water heater tank?
2) Can water pressure be used to push hydrogen around for burning?
3) Can somewhat higher pressures be safely used to store more hydrogen in
a somewhat smaller space? I know that's vague, but I'm just learning.
4) What parameters drives the speed of electrolysis? I've only done science
fair types with a dry cell and a couple of test tubes. I just read the
high temp hydrogen production page in the wikipedia. Won't work for simple
home generation.

Snippage.

BAJ
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist