Re: Solar-hydrogen home power system?

From: Ray Drouillard (cosmicpam2_at_comcast.net)
Date: 10/21/04 

Date: Wed, 20 Oct 2004 20:51:57 -0400

"Dan Bloomquist" <EXTRApublic21@lakeweb.com> wrote in message
news:4176DEE2.2040003@lakeweb.com...
>
>
> Ray Drouillard wrote:
> >
> >
> > 40% Is a whole lot better than the "less than none" that Don
Lancaster
> > keeps quoting. As a matter of fact, I'm beginning to believe that
he
> > has the whole spiel stuck in a text file for quick addition to his
> > prose.
>
> Capital cost needs to be considered. On the other hand, Mr. Lancaster
> has wave his hands around about wind and PV being energy sinks. Past
> research has shown otherwise.

Capital cost is economics, not engineering.

Effeciency is engineering, not economics.

They can be related, but the person expressing that relationship needs
to be explicit.

>
> I went and fetched Grahams post for you:
> > > This is it:
> > > 41 percent (of delta 'G' of hydrogen oxidation to water vapour)
> > > for the fuel cell spec'd at
> > > http://www.ballard.com/resources/powergen/NexaSpec***.pdf .
> > >
> > > Raising specific power -- only 1.2 kW over 13 kg --
> > > to levels adequate for a car prime mover drops the efficiency,
> > > I guess, by a third. Then there are inverter and motor losses,
> > > and we're down to 20 percent.
>
> However, I don't agree to his 50% hit in the implementation. The EV
side
> of the power train can easily do 85-90% net. There are source to wheel
> traction systems that run 90% to 97% over most of thier power/speed
range.

Agreed.

With 65%+ efficient fuel cells, and 90%+ motors, a vehicle can turn
hydrogen into motion very efficiently. The main bugaboo is storing the
stuff (an issue that has been debated hotly in this thread).

There are now 60%+ efficient methane-fuelled fuel cells. I know of none
that are commercially available, unfortunately. If they do become
available, they would be ideal for running an ev because the methane
storage technology already exists. It still isn't as energy dense as
gasoline, but it's a lot more dense than hydrogen. It also has the safe
ty advantage of dissapating and floating away in the unlikely event of a
pressure tank rupture.

Thirdly, it's a real fuel -- not something that is derived from a fuel.
It can be mined, or very easily created from biomass.

>
> >
> > I still want more details about that 40%. I'm hearing figures
anywhere
> > between 60% and 90% for both electrolysis and fuel cells. Where is
the
> > hard data?
>
> Crunch the numbers for your self, on that PDF above for that mighty
> pricey PEM unit, if you don't believe Graham.
>
> > Yes, I can google until I'm blue in the face and crippled
> > from carpel tunnels, but some of those quoting the efficiencies
ought to
> > have real data somewhere.
> >
> > If we have electrolysis going at 80% efficiency, and a 70% efficient
> > fuel cell (just to throw in some reasonable numbers). you have a
total
> > efficiency of better than 50% (allowing for some modest storage
losses).
>
> Electricity to wheels. Electrolysis 80%, storage 90%, PEM 40%, vehicle
> 85%. So you net 25% of your electrical input. There are EVs in
> production that net better than 50% now. Also, compare the capital
cost.
> Hydrogen, rough guess, will run some 5 to 8 times an EV commuter.

It pretty well goes without saying that making hydrogen from grid
electricity is a no-win situation.

As far as comparing a hydrogen system to a battery system -- well, I
expect the battery system to win when you consider efficiency. The
biggest obstacle for EV transportation is the lousy range of even the
best vehicle. It would be worth it to some people to give up some
efficiency just to get more range.

Getting back to the original post, though -- he was talking about a
totally fixed application. The electricity --> hydrogen --> electricity
idea had occurred to me, too. I was pondering what to do with cheap
solar cells of those much-promised organic semiconductor cells become
available at a reasonable price. At the time, I lived in the city, and
was limited to the area of my (small) roof. Therefore, storage to pick
up the slack in the winter would be a necessity. Since we also had
natural gas piped in, I planned on generating any additional electricity
needed using a natural gas fuel cell. The waste heat would be used to
heat the house.

Now that we live on a nice ten acre parcel, I'm not nearly so limited
when it comes to the area that I can cover with solar cells. That makes
it more feasible to get enough area covered to produce a day's worth of
electricity on even the shortest day. That cuts the storage
requirements considerably -- both in quantity and time. Hydrogen
wouldn't be necessary at all.

Of course, all of the above depends greatly upon the much-promised cheap
solar cells, as well as the availability of relatively inexpensive fuel
cells.

Then, of course, there are things like inverters and/or DC appliances.
The ceiling fans would have to be ripped out and sold. I would also
have to find something to replace the compact fluorescent lamps that we
have used to replace almost every incandescent light in the house. I
would probably use regular red, yellow, green, and blue LEDs in fixtures
that allow the light to mix because that is more efficient than using
white LEDs (for very good quantum physics reasons).

Incidentally, the cheapest way to save energy right now is to replace
all your incandescent lights with fluorescent lighting. Soon, LED
lighting will be more available.

So, my next realistic step is to make a digester to turn organic garbage
into methane. I don't expect to find an affordable methane fuel cell
any time soon, so if I get more methane than I can burn in my appliances
and vehicles, I'll use it to fuel a standard CNG generater, and use the
waste heat to heat the house. Lots of research has to be done before
getting anywhere near that far, though.

>
> >
> > If you want to compress the hydrogen to store it, and if the energy
cost
> > of that is significant, you can recover some of the energy by using
an
> > 'air engine' to decompress the hydrogen before it is fed into the
fuel
> > cell.
>
> Capital cost and energy density.
>
> >
> > Also, in a solar energy system, you are going to be getting more
energy
> > in the summer than in the winter. That means that you will be using
the
> > fuel cell in the winter if your solar array is sized such that you
need
> > to store power in the summer for use in the winter. In that case,
the
> > heat that is generated by the fuel cell can be used to heat the
house.
> > In that way, you can use 100% of the energy that you have stored in
your
> > hydrogen tanks. Any inefficiencies end up heating the house, or
maybe
> > even cooking the meals (depending on how 'retentive' you want to be
when
> > designing the system)
>
> It will never ever make sense to use hydrogen in a terrestrial
> application. Just run some numbers and compare them to the
alternatives
> that are presently applied.

I won't argue that point. Before I buy the equipment needed to
generate, store, and use hydrogen, I will build a big water tower and
use my excess energy to pump the water uphill, and use a turbine or
water wheel to get the energy back. As a bonus, I'll also have either a
swimming pool or a fishing pond.

I might argue with the people who are scared to death of hydrogen, or
those who say "less than zero", but I have already throught through the
hydrogen-as-a-fuel situation to have a good handle on what it would take
to make that practical. On a large scale, off-shore nuclear energy
would make it a good option. On a small scale, it would take a very
specific set of conditions to make it worthwhile.

>
> >
> > Certainly, the cost of photovoltaics makes the system uneconomical
now.
> > But, this is rec.arts.sf.science, so speculation of future advances
in
> > the art are definitely on topic.
>
> Sure, we could see thin film at a buck a watt. Still not cheap. I've
> been reading about it for years and I still don't see it happening.

I'm talking about organic semiconductors, which may very well be made
very cheaply. Still, I'll believe it when I see it. I'm hopeful, but
far from convinced.

> > If I could go out and buy a bunch of plastic sheeting that converts
> > light into electricity with an efficiency of about 8% for a few
cents a
> > watt, what would I do with it? Putting it on the roof would be a
good
> > start. Storing power in batteries short-term for use at night would
> > also be a good idea. In fact, I can save on the cost of an inverter
if
> > I use a bunch of batteries in series and store it at 180V, then just
use
> > some MOSFETs to generate a pseudo sine wave output -- no
up-converting
> > switching regulator, no muss, no fuss.
>
> As a past poster would say, 'If we only had some ham, we could have
ham
> and eggs, if we only had some eggs...'
>
> Inverters are $.50/watt, off the shelf. No muss, no fuss.

They will probably be cheaper once electric cars come more into
production. Right now, high-power switching transistors and fast
high-power diodes keep the prices up.

>
> Qusetion, why hydrogen?

Because it's cool?

Remember, I'm not advocating the hydrogen solution. I have thought it
through, and share the conclusion of some or the people I am arguing
with. I don't share their reasoning, however.

Ray Drouillard

>
> >
> > Ray Drouillard
>
> Best, Dan.
>
> --
> http://lakeweb.net
> http://ReserveAnalyst.com
> No EXTRA stuff for email.
>

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