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Why batteries instead of hydrogen?

Post in 'The Green Room' started by rhetoric, Mar 7, 2008.

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  1. rhetoric

    rhetoric Member

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    It seems (intuitively, which is dicey, I know) that much of the problem w/ PV and windturbines is the storage of the excess energy. Batteries are convenient because they can easily power into the existing grid, but they also are costly, lose power over time, etc. Why not produce hydrogen and use that stored energy instead of batteries? Just a matter of infrastructure? I know hydrogen isn't any more dangerous than gasoline. Just curious!

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  2. SteveJ

    SteveJ Member

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    I am intrigued.

    I am totally off grid and batteries play nicely with inverters.

    Do you know of any production fuel cells that can be used to store hydrogen?

    Also, from the PV panels, the voltage and current can be directly pumped into batteries. What is the equivalent mechanism for hydrogen?

    Finally, ho to extract the hydrogen into AC voltage and current to power everything in the house? What about surge loads - refrig motors, etc.?
  3. jebatty

    jebatty Minister of Fire

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    Have no knowledge on "literal" danger of hydrogen vs gasoline, but I don't know what this means. Hydrogen is very unstable and extremely combustible. As the smallest atom, it also is very difficult to store and occupies a very large space except under high pressure. Compression and storage may be very expensive. When it burns, it is invisible to the eye, except to the extent the combustion includes other materials. One could actually walk into a hydrogen fireball and not even know it (except perhaps from feeling the heat). And then, of course, what's the physics and chemistry of conversion to hydrogen and reconversion into something useful which would be economical? Appears to me that if this were truly "simple," hydrogen availability and applications would be everyday occurrences.

    Good luck on your hydrogen route.
  4. Telco

    Telco New Member

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    It's not only possible, it's been in operation since 1994. I don't think they've got it ready for commercial production to the little guy yet though. It would probably take more than double the needed PV arrays to make both daytime power and hydrogen for nighttime use. No idea if the fuel cell here would make enough power to run the house all night, either. They are just using it to run a single compressor, no idea what that compressor's power requirement is. Since the compressor is aerating an entire aquarium, it might be able to provide enough for a modest house though. Would be nice to be able to set something like this up and not ever need to replace batteries.

    Edit - Read this article and tell me it isn't exiting. If you could make one of these setups to produce hydrogen, you could fuel your car too. I knew it was possible to run a car of hydrogen, but it just clicked in my mind just how powerful this could be. You could set your car up as a dual fuel vehicle, run it off hydrogen when in your home area, and still run it off gasoline if you ever went on a long trip or got caught short somewhere.

    Second edit - Or maybe not. According to this guy it takes 4 times the energy to convert electricity to hydrogen as it does to go hydrogen to electricity. You'd have to be set on doing this and willing to put the money in regardless of payback, if this is the case. Eventually though, it might become cheaper to go ahead and do it this way.

    Final edit - Looks like the plug-in hybrid is the way to go for the forseeable future, along with the current battery powered solar/wind setup. Fuel cells are going to have to have an exponential leap in technology and be paired with an exponential leap in renewable sources before they will be useful for more than experimental uses. Bummer.
  5. Corey

    Corey Minister of Fire

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    One main reason is that battery charging efficiency is typically quoted at around 70%. So for batteries you may have something like:

    solar cell > power controller @ 95% eff > charge battery @ 70% eff, then you use the power in what ever device you want, but the overall storage was .95 x .70 = ~67% efficient.

    For hydrogen: (best case)

    solar cell > power controller @95% > electrolytic cell @ 70% > fuel cell @ 50% eff = .95 x .70 x .50 = ~33% efficient

    For hydrogen: (probable case)

    solar cell > power controller @95% > electrolytic cell @ 50% > internal combustion engine @ 30% eff > electric generator @ 85% = .95 x .50 x .30 x .85 = ~12% efficient
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