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Thread: Hydrogen engines

  1. #61
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    Quote Originally Posted by philippeb8 View Post
    Are you serious? Then we should definitely open a research center on the subject!
    This is getting a bit painful to watch. Have you looked to see if anyone is doing this already. You may be surprised.

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    Quote Originally Posted by philippeb8 View Post
    It’s market analysis now... but let’s keep in mind hydrogen is lighter than petroleum so it could feed an engine for a longer period of time for the same volume of fuel.

    Also since it’s profitable and risk-free (after a proper market analysis) then I’m sure venture capitalists will jump on the occasion to invest.


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    Hydrogen has a low density; its energy (LHV) per cubic meter is considerably lower than that of liquid hydrocarbons; I remember that a liter of liquid hydrogen has about one-fiftieth the mass of the same volume of Jet-A. Hydrogen's LHV per unit mass is about 50% greater than Jet-A. In other words, if my engine needs x megajoules/second, it would need y kg/s of hydrogen or about 1.5y kg/s of Jet-A. The volume would fall out from the density of the fuel.

    For one application, gas turbines, hydrogen would be better than Jet-A, as it wouldn't produce fine carbon particles during combustion, the radiation from which is the source of significant thermal loads in the hot end (coatings are used to ameliorate this). NOx emissions are dealt with by combustion chamber design in current engines; similar techniques would work with hydrogen as with hydrocarbons.
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    Quote Originally Posted by swampyankee View Post
    Hydrogen has a low density; its energy (LHV) per cubic meter is considerably lower than that of liquid hydrocarbons; I remember that a liter of liquid hydrogen has about one-fiftieth the mass of the same volume of Jet-A. Hydrogen's LHV per unit mass is about 50% greater than Jet-A. In other words, if my engine needs x megajoules/second, it would need y kg/s of hydrogen or about 1.5y kg/s of Jet-A. The volume would fall out from the density of the fuel.

    For one application, gas turbines, hydrogen would be better than Jet-A, as it wouldn't produce fine carbon particles during combustion, the radiation from which is the source of significant thermal loads in the hot end (coatings are used to ameliorate this). NOx emissions are dealt with by combustion chamber design in current engines; similar techniques would work with hydrogen as with hydrocarbons.
    Hang on, the energy density per unit mass is over three times better for liquid hydrogen compared to hydrocarbons ?

    Per unit volume LH2 is about one-third that of hydrocarbons.

    So you need a fuel tank 3X as big but the weight of the contained fuel will be one-third that of equivalent hydrocarbon fuel. As long as you can make the fuel tank light enough I'd have thought LH2 would be particularly advantageous for aircraft, because of this weight advantage?

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    Quote Originally Posted by kzb View Post
    Hang on, the energy density per unit mass is over three times better for liquid hydrogen compared to hydrocarbons ?

    Per unit volume LH2 is about one-third that of hydrocarbons.

    So you need a fuel tank 3X as big but the weight of the contained fuel will be one-third that of equivalent hydrocarbon fuel. As long as you can make the fuel tank light enough I'd have thought LH2 would be particularly advantageous for aircraft, because of this weight advantage?
    Is making the tank light for a cryo fuel really trivial?
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    Quote Originally Posted by Noclevername View Post
    Is making the tank light for a cryo fuel really trivial?
    Right, they’re cold (so needing insulation) and very big. Don’t expect to put them in the wings. And you have to safely deal with boiloff and the limits of insulation. Years ago I read about a concept design for a hydrogen airliner. It was a monster, looking like one of those specialty cargo planes with a fat fuselage, with the tank taking up a significant part of that.

    Technically possible, but I expect that sequestration offset will long be the preferred option over hydrogen for jets because of practicality.

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    Quote Originally Posted by Swift View Post
    I saw one blog that said hydrogen through electrolysis was 80 percent. Perhaps it was wrong.
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    Quote Originally Posted by Copernicus View Post
    I saw one blog that said hydrogen through electrolysis was 80 percent. Perhaps it was wrong.
    I donít recall the numbers, but I saw a comparison of fuel cell electric vs. battery car efficiency losses somewhere. With hydrogen, it started with electrolysis, transport losses (if not produced on site), compression or refrigeration losses, storage losses (hydrogen is an escape artist) and then fuel cell losses (which tend to be less efficient than batteries). Batteries win on total efficiency, hydrogen has an advantage for range, if you can find somebody selling it, and refuel time is much less than recharge time.

    The efficiency issues will likely make hydrogen more expensive in the long run. It is more expensive currently, despite much of it being produced from natural gas, but limited supply is part of the problem.

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    Quote Originally Posted by Noclevername View Post
    Is making the tank light for a cryo fuel really trivial?
    I've no idea ! I just wanted to put the record straight about energy density of the fuels.

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    Quote Originally Posted by kzb View Post
    I've no idea ! I just wanted to put the record straight about energy density of the fuels.
    OK, but if it's impractical to use it won't matter how good it is.
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    Quote Originally Posted by Copernicus View Post
    I saw one blog that said hydrogen through electrolysis was 80 percent. Perhaps it was wrong.
    Electrolysis itself is a fairly efficient process if you look at how much of the energy you put in is converted to usable product (hydrogen). I don't recall the numbers, but I can believe 80%. But that's not the problem.

    The problem is that the hydrogen-oxygen bond is very strong and takes a lot of energy to split it. So the question is, where do you get that energy.

    Obviously, it is pointless to use hydrocarbon fuels (oil, coal) to make the energy if your goal is CO2 reduction.

    Renewables like wind and solar are not particularly energy intensive processes. And they have limits (you need wind and sunlight) and solar is not high efficiency (don't quote me on exact numbers, but state of the art solar is in the low 30s% efficiency or so and I suspect commonly available are in the low 20s).

    So, if one was going to somehow replace a large proportion of the Earth's transportation fuel needs with hydrogen, and generate that hydrogen from renewables, one would require some pretty vast investments.

    phys.org

    Solar thermal systems covering 10 percent of the world’s deserts — about 1.5 percent of the planet’s total land area — could generate about 15 terawatts of energy, given a total efficiency of 2 percent. This amount is roughly equal to the projected growth in worldwide energy demand over the next half-century.

    Such grand-scale installations have been seriously proposed. For example, there are suggestions for solar installations in the Sahara, connected to Europe via cables under the Mediterranean, that could meet all of that continent’s electricity needs.
    Before you get too excited, article about the biggest solar plants in the world.

    The Pavagada solar park spreads over 13,000 acres in the Tumkur district, Karnataka, which includes the five villages of Balasamudra, Tirumani, Kyataganacharlu, Vallur and Rayacharlu. The area was chosen due to its high solar radiation and the availability of land, as well as the fact that the region receives very little rainfall.

    By the end of 2018, the park is planned to have a total capacity of 2,000MW, with 600MW commissioned by the end of January 2018, and a further 1,400MW planned for this year.

    The total investment required to build the site was estimated at $2.2bn.
    A terawatt is a million megawatts. So, we are talking 500x this plant, or 500x two billion dollars as a very rough approximation (and I suspect there are some serious problems with scaling estimates like that).
    Last edited by Swift; 2019-Oct-15 at 01:46 PM.
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    Quote Originally Posted by Swift View Post
    Electrolysis itself is a fairly efficient process if you look at how much of the energy you put in is converted to usable product (hydrogen). I don't recall the numbers, but I can believe 80%. But that's not the problem.

    The problem is that the hydrogen-oxygen bond is very strong and takes a lot of energy to split it. So the question is, where do you get that energy.

    Obviously, it is pointless to use hydrocarbon fuels (oil, coal) to make the energy if your goal is CO2 reduction.

    Renewables like wind and solar are not particularly energy intensive processes. And they have limits (you need wind and sunlight) and solar is not high efficiency (don't quote me on exact numbers, but state of the art solar is in the low 30s% efficiency or so and I suspect commonly available are in the low 20s).

    So, if one was going to somehow replace a large proportion of the Earth's transportation fuel needs with hydrogen, and generate that hydrogen from renewables, one would require some pretty vast investments.

    phys.org



    Before you get too excited, article about the biggest solar plants in the world.



    A terawatt is a million megawatts. So, we are talking 500x this plant, or 500x two billion dollars as a very rough approximation (and I suspect there are some serious problems with scaling estimates like that).
    That would only be one trillion dollars. If it only took 20 trillion dollars to convert off of hydrocarbons that would be a deal.
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  12. #72
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    A small point is that for airplanes hydrogen is not making co2 but it is making water vapour which is a potent greenhouse contributor. So it may be that battery development should continue. Hydrogen is good for boats and ships as a fuel cell because the weight of the containers can be tolerated. I think we will see more large ships using Hydrogen, but as new builds, conversion might be expensive.
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    Quote Originally Posted by Swift View Post
    So the question is, where do you get that energy.

    Obviously, it is pointless to use hydrocarbon fuels (oil, coal) to make the energy if your goal is CO2 reduction.

    Renewables like wind and solar are not particularly energy intensive processes. And they have limits (you need wind and sunlight) and solar is not high efficiency (don't quote me on exact numbers, but state of the art solar is in the low 30s% efficiency or so and I suspect commonly available are in the low 20s).

    So, if one was going to somehow replace a large proportion of the Earth's transportation fuel needs with hydrogen, and generate that hydrogen from renewables, one would require some pretty vast investments.
    We'll have no choice but to pay vast investments no matter what, to account for and mitigate the damage done by climate change and the crumbling condition of our energy infrastructure. "Pay me now, or pay me later". Or TANSTAAFL as the kids say these days.

    We've barely begun to toddle when it comes to renewables and electrics, but the fossil industry is propped up by subsidies too. In the long run solar will continue to get cheaper and more efficient, oil will not; and waiting that long may take us past an irrevocable tipping point, so I say let's get a head start now, while we still have the resources at hand. But IMO what we really need is to build multiple ways to store and distribute that collected energy, both local and large scale. Decentralize. And those storage methods need to be cheaper and more efficient than a hydrogen economy can accommodate.
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    Quote Originally Posted by Noclevername View Post
    We'll have no choice but to pay vast investments no matter what, to account for and mitigate the damage done by climate change and the crumbling condition of our energy infrastructure. "Pay me now, or pay me later". Or TANSTAAFL as the kids say these days.

    We've barely begun to toddle when it comes to renewables and electrics, but the fossil industry is propped up by subsidies too. In the long run solar will continue to get cheaper and more efficient, oil will not; and waiting that long may take us past an irrevocable tipping point, so I say let's get a head start now, while we still have the resources at hand. But IMO what we really need is to build multiple ways to store and distribute that collected energy, both local and large scale. Decentralize. And those storage methods need to be cheaper and more efficient than a hydrogen economy can accommodate.
    This is what I thought the thinking was. We will probably need twice as much electricity if we went to electric vehicles. Obviously solar is getting more efficient and cheaper. I don't think efficiency is nearly as important as the price, but they likely will correlate to some degree. Obviously transmission will be a big deal, but I really think everyone will also have their own rooftop devices that will double as shingles. Extra electricity will be produced and it is likely some of that will go into home storage batteries, besides the vehicles, but in big installations some type of conversion over to hydrogen gas or liquid fuels or even pumping water to a giant reservoir that can produce hydroelectric power when the sun and the wind aren't working. Coal, gas, and oil will get more scarce and probably will only be used for manufacturing of polymers or other such type of components. My preferable conversion to a liquid fuel would be glycerin or propylene glycol and use it as a diesel type engine, but I don't even know if that makes sense or if those chemical reactions can be done efficiently. I think hydrogen, by itself, may always be too hard to store for moving sources, as the mechanisms for storage may always be too heavy.
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    Quote Originally Posted by Copernicus View Post
    This is what I thought the thinking was. We will probably need twice as much electricity if we went to electric vehicles. Obviously solar is getting more efficient and cheaper. I don't think efficiency is nearly as important as the price, but they likely will correlate to some degree. Obviously transmission will be a big deal, but I really think everyone will also have their own rooftop devices that will double as shingles. Extra electricity will be produced and it is likely some of that will go into home storage batteries, besides the vehicles, but in big installations some type of conversion over to hydrogen gas or liquid fuels or even pumping water to a giant reservoir that can produce hydroelectric power when the sun and the wind aren't working. Coal, gas, and oil will get more scarce and probably will only be used for manufacturing of polymers or other such type of components. My preferable conversion to a liquid fuel would be glycerin or propylene glycol and use it as a diesel type engine, but I don't even know if that makes sense or if those chemical reactions can be done efficiently. I think hydrogen, by itself, may always be too hard to store for moving sources, as the mechanisms for storage may always be too heavy.
    Except as an airship!
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    Quote Originally Posted by Noclevername View Post
    We'll have no choice but to pay vast investments no matter what, to account for and mitigate the damage done by climate change and the crumbling condition of our energy infrastructure. "Pay me now, or pay me later". Or TANSTAAFL as the kids say these days.

    We've barely begun to toddle when it comes to renewables and electrics, but the fossil industry is propped up by subsidies too. [...]
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    Verdict?
    https://m.phys.org/news/2019-05-arti...quefiable.html


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    Quote Originally Posted by philippeb8 View Post
    Verdict?
    https://m.phys.org/news/2019-05-arti...quefiable.html


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    Verdict about what? I do not wish to follow that link blindly.

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    https://phys.org/news/2019-06-sun-fr...synthesis.html
    There are more artificial photosynthesis projects. Chlorophyl may not be the best, or of course we can plant trees .
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

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    Quote Originally Posted by profloater View Post
    https://phys.org/news/2019-06-sun-fr...synthesis.html
    There are more artificial photosynthesis projects. Chlorophyl may not be the best, or of course we can plant trees .
    Youíre right:

    ď[...] the researchers acknowledge that Jain's artificial photosynthesis process is nowhere near as efficient as it is in plants.Ē

    I wish I had time to work on this myself as it canít be harder than astrophysics!


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    What about simply mixing hydroelectricity and electrolysis? Iím sure the turbines could generate enough power to do so and itís an eternal source of energy.

    Here in Canada we have hydroelectricity in excess!


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    One way or the other thank you all in advance for this great conversation!


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    Quote Originally Posted by philippeb8 View Post
    What about simply mixing hydroelectricity and electrolysis? Iím sure the turbines could generate enough power to do so and itís an eternal source of energy.

    Here in Canada we have hydroelectricity in excess!


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    Wow! They are already doing it in Switzerland!?!
    https://www.cnbc.com/2017/10/13/a-hy...-car-fuel.html

    Then what are we all waiting for?


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    Quote Originally Posted by philippeb8 View Post
    What about simply mixing hydroelectricity and electrolysis? I’m sure the turbines could generate enough power to do so and it’s an eternal source of energy.

    Here in Canada we have hydroelectricity in excess!


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    https://en.wikipedia.org/wiki/Hydroe...#Disadvantages

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    Dams are already in place over here...


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    Quote Originally Posted by philippeb8 View Post
    What about simply mixing hydroelectricity and electrolysis? I’m sure the turbines could generate enough power to do so and it’s an eternal source of energy.

    Here in Canada we have hydroelectricity in excess!


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    Hey! We need that hydroelectric power down here, so we can avoid burning that stupid cosl.
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    Quote Originally Posted by swampyankee View Post
    Hey! We need that hydroelectric power down here, so we can avoid burning that stupid cosl.
    I just sent an email to the government...!


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    Quote Originally Posted by philippeb8 View Post
    Youíre right:

    ď[...] the researchers acknowledge that Jain's artificial photosynthesis process is nowhere near as efficient as it is in plants.Ē
    A further caveat. I didnít have to go beyond the title of the paper to see that they are talking about oxygen evolution. That is a critical first step in the process of photosynthesis, and being able to do it efficiently would be great, but then thatís only the first step in the process, and produces electrons that create a proton gradient, so essentially an electrical current, and you still have to figure out what to do with that current.


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    As above, so below

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    And also just a note. PNAS is a very good journal, with an impact factor of 10 or 11, but if anyone really achieved oxygen evolution with an efficiency close to that of complex II, it would be published in one of the journals with impact factors of 40 and they would also soon get an invitation to dinner in Stockholm.


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    As above, so below

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    Quote Originally Posted by swampyankee View Post
    Hey! We need that hydroelectric power down here, so we can avoid burning that stupid cosl.
    Gravity has always been useful to store energy, eg falling weight clocks, but a big falling weight can bereplaced with a small battery. Liquid hydrocarbons store much more and sure, Hydrogen can have a place too, but powering the world needs a mixed technology solution. Switzerland has lots of mountains, other places have tides or loads of sunshine or wind. My favourite for storage is the flow battery. i think there is plenty of scope to invent and improve and the storage is in giant containers. But then using less is even easier if you allow compromises. Fossil fuels allowed many advances but now we need to think.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

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