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Hydrogen generation from seawater

  • 1.  Hydrogen generation from seawater

    SENIOR MEMBER
    Posted 07-14-2019 02:46
    Instead of generating hydrogen from freshwater sources which are limited in number, we can greatly enhance the production capacity by utilizing seawater.
    There will be some precautions to take for e.g. dealing with the saline water which will pose corrosion threat to the electrodes.
    Hydrogen will be produced at the cathode and oxygen at the anode but chlorine tends to corrode the anode and hence the oxygen evolution reaction will be hindered. Hence we can use a NI3 anode which will protect the anode against the salinity of the water.
    This looks like a viable and renewable alternative to the generation of clean energy through hydrogen by using it in fuel cells.
    Any discussions will be appreciated.

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    Rohit Korde MSc,CEng
    Program Manager
    Worley
    Thane (W)
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  • 2.  RE: Hydrogen generation from seawater

    SENIOR MEMBER
    Posted 07-16-2019 07:13
    Sea water will needed several pre-treatment prior to utilize in the operation which will increase the price of H2 product.  Furthermore, when it comes to the price of Hydrogen and importance of Hydrogen for the greener economy, 1 g of Hydrogen from 18 g of water is not a big deal. So  See the amount of water being wasted in other industry just for primary operations like washing or cooling. Anyway good thoughts. Perhaps when we manufacture hydrogen in large quantities these cost of pre-treatment would matter less. Again, good thoughts. Perhaps good topic for a techno-economic feasibility analysis.

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    Dilantha Subasinghe
    Senior Lecturer GII
    University of Moratuwa, Sri Lanka
    Moratuwa
    thusharas@uom.lk
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  • 3.  RE: Hydrogen generation from seawater

    SENIOR MEMBER
    Posted 07-16-2019 09:48
    We need to look at the feasibility of hydrogen as a clean fuel across the entire supply chain.  It may not be so clean when all factors involved in generating hydrogen, delivering to supply centers, carrying it aboard a vehicle as fuel, etc. are accounted for.  As Dilantha Subasinghe points out, worrying about chlorine in seawater is only one of a number of concerns using seawater as the feedstock for a hydrogen generation facility.  What happens to the rest of seawater matter after hydrogen extracted? e.g. all the mineral salts, organics including plankton, etc.  How much energy is delivered in the form of hydrogen fuel relative to the amount of energy used to generate the hydrogen?  How much energy is used merely delivering the hydrogen to end users? e.g. compression.  What is the cost per unit of fuel to create the supply movement and storage systems? e.g. hydrogen embrittlement resistant metallurgy of all pipes and vessels, high pressure containment capability, etc.  Refiners are intimately familiar with the hazards of using high pressure hydrogen, can we create safe, secure public storage and delivery systems on a large scale?  I know niche operations are working on a local level, is it economic considering all costs across the supply chain to scale up?

    I haven't looked at any specific numbers but a gaseous transportation fuel system seems expensive and less safe, secure compared to a liquid one.  This past spring semester, some of my Process Design seniors compared the cost of using landfill gas (~50% methane, 50% carbon dioxide) to generate electricity vs using microchannel Fischer-Tropsch to generate diesel fuel vs generating compressed methane from the landfill gas.  The latter 2 for use in the trucks delivery trash to the landfill.  Generating electricity proved the most economic alternative to just flaring.


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    Suzanne Roat PE
    Crude and Refining Planning and Strategy
    SRC LLC
    Houston TX
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  • 4.  RE: Hydrogen generation from seawater

    SENIOR MEMBER
    Posted 12 days ago
    Suzanne's post is excellent.  She poses all key questions.   Hydrogen is made from natural gas today for economical reasons.   Saltwater has so many components and if any of those have lower reduction potentials they will be preferentially reduced over water.   We make electricity from chemical energy and only in very special cases such as chloride do we use expective electrical energy to make chemicals.

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    William Banholzer
    University of Wisconsin- Madison
    Madison WI
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  • 5.  RE: Hydrogen generation from seawater

    SENIOR MEMBER
    Posted 12 days ago
    There are already commercial pipelines in the US that transport hydrogen from producers to users -- 1600 miles of pipelines  (see https://www.energy.gov/eere/fuelcells/hydrogen-pipelines)   The cost of pipelines for carrying hydrogen is about 68% more than the cost of natural gas pipelines (see https://www.nist.gov/news-events/news/2015/07/nist-calculates-high-cost-hydrogen-pipelines-shows-how-reduce-it).

    Hydrogen (or ammonia as a carrier) might be a good option for storing energy from solar and wind sources, at least in some cases.  The storage issue for these renewable sources of energy must be overcome one way or another.  There are challenges to using hydrogen for energy storage (see https://www.energy.gov/sites/prod/files/2017/08/f36/hdtt_roadmap_July2017.pdf) , but challenges come with every change.

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    -Kirsten

    Kirsten Rosselot
    Process Profiles
    Calabasas, CA United States
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  • 6.  RE: Hydrogen generation from seawater

    Posted 7 days ago
    Hi,

    Since the end use of Hydrogen will see the release Steam/Water, we may see the formation microclouds and condensation around the point of use. Since this is likely to be on land, water/mist will replenish ground water. I could be wrong; just thinking out loud.

    Regards,
    Pavan

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    Pavan Kumar Naraharisetti
    Assistant Professor
    Newcastle University in Singapore
    Singapore
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