Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Separating hydrogen from effluent HHO by gravity.

  1. Jul 11, 2018 #1
    I'm would like to learn of the practicality of separating HHO gas released from a photovoltaic charged lead-acid battery bank for hydrogen storage, perhaps by exploiting the substantial difference in density of the two elemental gases.
    It occurred to me that were the gas emitted from batteries collected by means of tubing leading to a manifold, and then to a column, the hydrogen will tend to collect at the top of the column and the oxygen will sink to the bottom. Electronic hydrogen detectors near the top of the column would control a servo controlled valve and positive displacement pump, with the concentrated hydrogen passing through a catalytic mesh to strip the remaining oxygen before high-pressure storage.
    I believe there must be a reason why this would not achieve the desired results but I'm unable to put my finger on it. Preventing the recombination of the HHO before separation is a must for safety, even though the quantities are small. Use of non-reactive material which does not accumulate static charges will make things unlikely to go bang in the night.
    Any thoughts on this would be appreciated, Jeff
     
  2. jcsd
  3. Jul 12, 2018 #2

    Drakkith

    User Avatar

    Staff: Mentor

    Why don't you just run an electrolysis device using a photovoltaic panel and directly capture the H2 and O2 gases at each electrode? That way it's already separated when you capture it.
     
  4. Jul 12, 2018 #3
    I've considered doing just that with excess energy from the photovoltaic array. However, my objective is to learn whether an energy stream which is usually wasted can be saved for later use, perhaps as one resource among others to bridge the "January Gap" when photovoltaic output is low and electrical demand (mostly from my geothermal heat pump) is high. Also, I recognize the limitations present in hydrogen storage and conversion of hydrogen to electrical power, so this scheme is likely to be of marginal value.
    Thanks for your thoughts on this, Jeff
     
  5. Jul 13, 2018 #4

    anorlunda

    Staff: Mentor

    Saving wasted energy is good. But I think you will be disappointed by how little hydrogen is produced by the lead-acid battery.

    If you are going to work with engineering ideas, then you must start doing it with numbers, not just principles and theories. Do a little research and find out how long it would take a lead-acid battery to produce 1 m3 of H.
     
  6. Jul 13, 2018 #5

    Drakkith

    User Avatar

    Staff: Mentor

    There shouldn't be enough gas produced to be useful. If there is, you need new batteries. :wink:
     
  7. Jul 13, 2018 #6
    Thank you both for your responses. As a matter of fact, before considering this scheme I searched online until I was able to find the formula to calculate the quantity of HHO gas emitted by lead-acid cells during a charging cycle. Not too easy to find, but I discovered it in a battery manufacturer's webpage on determining the ventilation capacity needed for rooms where lead-acid batteries are charged. It included the function of gas emission vs. increasing state of charge (low initially and for much of the cycle, becoming high as full charge is approached).
    Also, the only aspect of my original question where quantification would be appropriate would be the efficacy of separation, i.e. percentage of gases other than hydrogen in the product. The matter of whether the process volume is 10 mL or 1 cubic meter per day is extraneous.
    Thanks again for the advice, de AC4AQ
     
  8. Jul 14, 2018 #7

    anorlunda

    Staff: Mentor

    Them it is also extraneous whether your energy harvesting harvests one joule or one millijoule.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted