Round trip conversion efficiency of electrolytic hydrogen production

Sure, they'd probably be right, too.

I'll phrase the question another way: if you wanted to store around 4000 megajoules of grid energy extremely short duration (say twelve hours maximum) in the most efficient method available given current or near future technology, how would you do it?

Assume that pumping water up a hill isn't a viable option. Or a hill-railroad. Or any kind of gravitational potential type deal.

I agree with just about everything he says, but there are apparently large-scale PEM electrolyzer prototypes in operation with efficiencies over 80%.

It looks like that article was written over 15 years ago, and materials science has advanced.

No, I'm not interested in building a "water powered" car.

Why? They are already up to their armpits in the arbitrage game. As renewables become more of thing, they will just have to raise prices. It'll keep their risk of capital expenditure down as well.

If I were them, I'd talk to private equity firms about aggregating promising renewables technology and get in front of the parade. They're not like oil companies that could be essentially replaced by a different business model.

I say "private equity" because being public means you have your attention span shortened.

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Les Cargill

Why not just say we all need magic genies? Bacteria can produce useful energy products, but you have to give them something with more energy to start with, or you have to give them raw energy like light. The law of conservation of energy says so.

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Rick C

I have posted before that the house I grew up in had two meters, one for the hot water heater and one for the rest of the house. The hot water was metered at a lower rate because it was shut off at peak time, something like 5 to 8 pm. I don't know why they took that meter out. Seems like many things could be put on such a meter as you say.

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Rick C

That idea was proposed quite a while ago. Several terajoules of energy in a form where it can be quickly released sounds like a pretty good approximation of a large bomb. Think coolant failure ?

No worse than a big tank of NG or hydrogen or gasoline, but spread out over several miles. If it quenched, it would boil off a lot of liquid helium.

I've been around high-field superconductive magnets when they quenched. No big deal; just make sure the helium doesn't push the oxygen out of the room.

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John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

Why store expensive electrical energy at a considerable loss? Store natural gas and run a turbine.

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John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

Fuel cells. Oh boy. Platinum is kind of expensive. Do you plan to compress the hydrogen too? That's an extra layer of energy expenditure right there.

Why not open a landscaping business, collect wood branches and lawn clippings, dry them out, and burn them for energy? You can even collect money from your customers!

Michael

Giant air compressor? Run in reverse when the compressed air tanks are full?

Metallic sodium refinery? electricity + NaCl -> Na (solid) Na (solid) + H2O -> NaOH + 1/2 H2 NaOH + HCl -> NaCl + H2O (but where would you get HCl at a reasonable cost...)

Michael

That's not especially efficient. Pumped water storage is better.

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John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

Are you referring to the LHC?

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Rick C

Which is more cost effective, stored hydro power or generation facilities? The idea is to *not* build more power plants to meet peak loads, but to have less expensive ways of storing and reusing power generated in off peak times.

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Rick C

Yeah, emphasis on "big". The windings of that inductor are mechanically stressed by the field; your magnet is unlikely to ever economically replace an acre-foot of water in a hydroelectric reservoir.

If you figure you can sustain one ton per meter of conductor, and 100A current, then the limit on B field is 98 Tesla

1 ton ~= 9800 N = I* L * B = 100A * 1m * 98 T

For a household daily energy use of 24 kWh

24 kWh= 8.64 * 10**7 joules = E_daily

and energy stored in B field comes to

E_daily = Volume * u_0 * B**2

u_0 is 4*pi* 10**-7

Volume =7 billion cubic meters

... or did I mess up the units somehow?

An acre-foot of water occupies 1233 m^3, one ton/m^3 and with a 100m drop delivers

9.8 * 1233 * 1000 * 100 = 1.2 x 10^9 joules

which is a couple of weeks of household use (14 * E_daily)

Anyway, magnetic storage of B-field energy isn't practical on this scale. Existing pumped hydroelectric wins big on cost.

Your first step generates free Cl, but only generates free Na from a molten salt bath. An aqueous solution gives Cl2 gas and H2 gas at the two electrodes.

Where are you going with this?

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Rick C

Not sure it would be very pretty if the bug got into the wild.

No way! Some greenie-PETA type will find a spotted minnow or Zika mosquito that needs to be protected.

Even better, if you have a river

A hydroelectric plant will have an efficiency of about 90 %.

Currently a hydroelectric plant is run during the peak load periods during the day. With a lot of solar power, the hydroelectric plant would run during the night. The dam will not need to be huge, since it would only store water for a day.