
Advancing electrolysis: Splitting water to store energy as hydrogen - elorant
https://inl.gov/article/advancing-high-temperature-electrolysis-splitting-water-to-store-energy-as-hydrogen/
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tln
"the cell was firstly operated at an electrolysis mode with a constant current
density of 0.6 A cm−2 for three minutes to generate hydrogen, which was
instantly consumed by switching to a fuel cell mode at 0.2 A cm−2 for two
minutes"

So, 22% round trip efficiency

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rrmm
Shouldn't you take into account the voltage. From the graphs they don't look
like they were symmetrical.

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tln
Doh!

Fig 6c[0] shows ~1.6 in and 0.4v out so... 5% round trip efficiency?

[0]
[https://www.nature.com/articles/s41467-020-15677-z/figures/6](https://www.nature.com/articles/s41467-020-15677-z/figures/6)

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rrmm
Interesting:

I had no idea there was an Idaho National Lab.

The new electrode is a perovskite which is a crystal structure tangentially
related to superconductors among other things.

The electrode allows for reversible operation in the 400-600 degC range.

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aYsY4dDQ2NrcNzA
Home of a deadly reactor explosion.

[https://en.wikipedia.org/wiki/SL-1](https://en.wikipedia.org/wiki/SL-1)

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rrmm
I did know about the SL-1 which makes it an even more glaring oversight. Maybe
I associated it more with Argonne? I dunno.

But that SL-1...dang.

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triceratops
Does anyone know if coal or nat gas power plants can burn hydrogen too? Or be
retrofitted to burn it? Then you could store excess solar or wind energy
generated during the day as hydrogen and burn it at night.

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ChuckMcM
Sure, since the lab is running their perovskite at 600 C anyway, just add CO2
in a chamber with some nickel and get methane out via the Sabatier reaction.
Send the methane to where ever its needed.

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eloff
So many problems are solved so easily by "just" doing simple thing X. Maybe
this really is a simple fix. It doesn't sound that way to me though.

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ChuckMcM
It's not. The response is 'accurate' not 'easy' :-) The biggest challenge is
getting a source of CO2 using less energy than you are going to get back by
burning the methane.

Thermodynamics doesn't let you cheat sadly.

When evaluating these sorts of things you follow the energy consumption of
each step and remove it from the initial pool of energy. Energy out over
energy in will give you a way to compare methods for "goodness" regardless of
complexity. Processes that have net negative energy are clearly in the "bad"
category. Any positive is something.

Localized schemes like hydro pumping do quite well in this equation. It is
distance schemes that suffer.

Distance schemes are hard because pushing electrons through a wire spends
power just getting through the wire. Eventually its all gone. This is why you
can't just cover 1/3 of Nevada with PV solar cells and power the grid from
that one state.

So distance means transforming electricity into some other energy (chemical,
potential, kinetic, thermal), moving it physically somewhere else (ideally
without much loss) and then converting it back into electricity at the
destination.

One of the more fanciful ideas I heard was train cars full of Tesla powerwall
packs. If you've ever seen an operating coal fired power plant you may have
seen the long line of coal cars in a train that pulls in each day. Once at the
plant the cars are slowly pulled through the plant, dumping coal when they
need to into the feed mechanism. Eventually a string of empty cars is on the
other side to take back to be refilled. Imagine doing that with powerwalls.
Cars pull up, connect electrically to the plant and start discharging. Once
they are down to their "empty" level the car disconnects and moves on. I think
it would be fascinating to watch.

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effie
> spends power just getting through the wire. Eventually its all gone.

No, transmission losses for such concentrated power generation could be kept
acceptable single digit percent by building a proper power transmission
system. Just use higher voltage, thicker wires. It would be expensive, but if
Nevada was a great energy source, it could be worth it long term.

> This is why you can't just cover 1/3 of Nevada with PV solar cells and power
> the grid from that one state.

I can think of more substantial problems with that - fragile panels exposed to
harmful environment, manufacturing and maintaining panels generates too much
waste per kWh, unreliable operation dependent on weather. If Nevada was to be
used as a primary center for energy generation, I suggest uranium/thorium
reactors. They are better in every possible way.

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ncmncm
Better, except that they take too long to build, cost too much to operate, and
have proven incompatible with sound public policy.

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effie
The median time to build a nuclear reactor is 7.5 years [1]. That is not too
bad.

[1] [http://euanmearns.com/how-long-does-it-take-to-build-a-
nucle...](http://euanmearns.com/how-long-does-it-take-to-build-a-nuclear-
power-plant/)

