Hydrogen vs battery storage

Discussion in 'General Science & Technology' started by billvon, Apr 17, 2023.

  1. billvon Valued Senior Member

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    This has come up a few times lately so I figured I'd start a thread on it.

    Hydrogen has been around forever. It's been used as a fuel for spacecraft (the Space Shuttle's main engines used hydrogen and oxygen) as a feedstock for refinery cracking, and as an intermediate step in a great many industrial processes. It is even planned for manufacture on Mars via a fairly clever fuel cycle, like so:

    • A lander with a few hundred pounds of hydrogen lands; the rest of its tanks are empty. The lander then takes CO2 from the air, and via the Sabatier process, turns the two ingredients into methane and water. The water is broken down into oxygen and hydrogen. The hydrogen is reused; the oxygen and methane are stored in the lander's tanks. After a few months the lander has enough fuel to return to Earth. This is called ISRP (in situ resource production) and is about the only way to get back from Mars in a reasonable time.
    But that's a side note. The 'battle' that is shaping up, if you will, is between battery and hydrogen storage of energy. Batteries have been assumed both for grid scale storage (for peak loads and to store solar/wind) and for EV's. This is mainly because batteries are very, very efficient and storing and releasing energy; you can see 75-99% efficiencies depending on charge/discharge rate.

    They are expensive though, although that cost has been dropping rapidly. They are now sufficiently energy dense and sufficiently cheap to make cheap long range cars available. The one remaining problem is that the raw materials are scarce, but as lithium ion gives way to lithum phosphate and eventually sodium, that problem will decline - making batteries more and more attractive.

    Hydrogen hasn't been standing still, though. And there are now more and more companies making compact electrolyzers that are both efficient and cheap. Off-the-shelf systems now hit 80% and smaller experimental electrolyzers are hitting 98%. And they offer an interesting niche - as solar and wind get built out, there are times when the grid cannot accept all the power that they produce. During one day last spring, for example, solar/wind/hydro produced 103% of California's power needs. (The 3% was exported.) This means that pretty soon we will see periods where way more power than the local grid needs will be produced by renewables.

    At that point you can curtail (shut down generation) or find other loads. Batteries are a good load, but their cost goes up by how much energy you store. Hydrogen is the opposite - you pay for power, but energy (storage) is very, very cheap.

    More and more companies are making small (two shipping containers) electrolyzers that will take 10 megawatts of power and convert water to hydrogen with the power. And these go for a few million. If energy is free, that sort of system will recoup its cost in 3-4 years. And more and more often, energy will be free for part of the day, especially near solar and wind farms.

    And this is starting to happen. Several natural gas plants in the LA area now run on a 70/30 methane/hydrogen mix, and fuel cell peakers are in the planning stages.

    I used to think that hydrogen was going to be a non-starter for both storage and vehicles until we had high temperature nuclear reactors that could do thermal dissociation of water. But the advent of efficient and cheap electrolyzers - along with the unexpected problem of having too much free energy - has been making me rethink that. It also enables some solutions (like aviation) that are decades away from being doable with batteries.

    So in the future you may see hydrogen start to creep into wider use as a storage medium and as a motor fuel. Rapid reductions in battery cost will slow that down, but hydrogen will continue to be a more and more viable option as time goes on.
     
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  3. Seattle Valued Senior Member

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    This fits in with a more deflationary economy with less debt and lower costs of most everything. Everything tends to have an energy/transportation cost including farming and food.

    I had thought it was further into the future as I thought in terms of energy as being much cheaper if fusion, including distribution costs should become a reality and do all that it is supposed to do.

    Maybe that day is closer using hydrogen as you suggest...
     
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  5. exchemist Valued Senior Member

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    It seems to me that hydrogen may well become an essential part of the energy mix for home heating, certainly. In the UK, most people have gas central heating and the housing stock is old - much of it 100 years old or so. These houses are very hard to retrofit with heat pumps (I explored it and gave up) and the cost of such pumps is high, especially in a country where AC is not required in summer so you get no advantage from running them backwards in summer. You can blend 25% of hydrogen into the existing natural gas distribution system, however, without even changing the burners.

    Hydrogen for transport suffers from the usual Carnot cycle efficiency drawback, but if its production is close to free, from surplus solar and wind generation, that may not matter. And from what I read there are real problems with getting batteries big enough for heavy duty lorries. Even the trolley bus system, with overhead wires on motorways, is being considered, to get over this difficulty. Hydrogen might be a better bet for this.

    I certainly think governments should fund the kickstarting of hydrogen technology and avoid putting all their eggs in the electricity basket. I see it as like VHS vs. Betamax. We can't know at this stage which will win out commercially, so attempting to pick a winner, to "save" upfront development cost could be a strategic blunder.
     
    Last edited: Apr 17, 2023
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  7. billvon Valued Senior Member

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    True only if it is used in such an engine. Fuel cells are getting cheaper as well.
    Agreed, although hydrogen at its most basic is just another way of distributing electricity.
    Also agreed.
     

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