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Hydrogen fuel cells won't happen. There are too many downsides. Hydrogen must be stored as a compressed gas or as a deep cryogenic liquid. Either way such tank

by chroma 4y ago

Hydrogen fuel cells won't happen. There are too many downsides. Hydrogen must be stored as a compressed gas or as a deep cryogenic liquid. Either way such tanks are expensive, heavy, and create safety concerns. Hydrogen is a very pernicious molecule, and leaks cannot be detected by human senses. All hydrogen vehicles and fueling stations need special sensors to detect leaks. Hydrogen is much easier to ignite than gasoline. Any concentration from 4-74% will explode in air, and the flame is nearly invisible. Refueling a hydrogen tank involves going from high pressure to low pressure, which causes the fuel line and nozzle to get extremely cold. Even in southern California, refueling a few Toyota Mirais causes the nozzle to freeze to the valve. This limits refueling speeds and duty cycles. Lastly, hydrogen is far less efficient as an energy storage medium. With a battery, you put electricity in and get electricity out. It's 80-90% efficient. With hydrogen, you use electricity to split water, then compress and liquefy the hydrogen, then run it through a fuel cell. The fuel cell itself is 40-60% efficient. At the end of the whole process, around 30% of your initial electricity comes out of the fuel cell.

_hypx 4y ago
Long-distance battery airplanes are literally impossible. If you don't agree with hydrogen powered aircraft, you are advocating for conventional airplanes forever.
- jamiek88 4y ago
  That’s ridiculously short sighted to think out only options are hydrogen or the status quo. Off the top of my head I can think of biofuels plus carbon neutral recaptured co2 from excess renewable energy. Diesel electric motors for example with the ‘diesel’ being carbon neutral biofuel. This is actually being tested on large airbus jets currently. Hydrogen is one of the worst possible options for aircraft. Energy density is crap, tankage is heavy, failure modes catastrophic.
  - _hypx 4y ago
    Which would basically be conventional aircraft but running on biofuels or syn-fuels.
- chroma 4y ago
  I don't have a dog in this fight. I'm just explaining why hydrogen will never be popular. For a new technology to be adopted, it has to be better than the status quo. Compared to current aircraft, hydrogen costs more, has new safety concerns, and requires new infrastructure to transport and store the fuel. If that means aircraft will keep using fossil fuels, well then I guess we'll keep using fossil fuels.
- nradov 4y ago
  Forever is a long time, but our grandchildren will still be taking long-haul flights on conventional aircraft powered by turbine engines burning kerosene (possibly synthetic). The advantages of liquid hydrocarbons over hydrogen fuel are overwhelming in terms of safety, handling, and aerodynamics.
- ZeroGravitas 4y ago
  I think hydrogen (or something made from it) and fuel cells will win in the medium term. It's energy inefficient, but we're going to have a lot of cheap energy which will make lots of energy inefficient things reasonable, as long as you can store the output in some way. Having said that, with future automatiion, I do feel there's room for aircraft that combine and re-assemble themselves in mid air. For example, a VTOL tug that lifts off and starts a craft flying, but then detaches and returns to base. This can potentially be repeated on the landing side, and even mid-air "re-fueling" via battery drones. Possibly I just watched too many kids shows where vehicles did this and it's now my equivalent of the Jetson's flying cars. Feels like the next crazy project for Silicon Valley Billionaires to look into now that electric flight, jetpacks, rockets that land vertically etc. are all solved problems.
  - mschuster91 4y ago
    The more interesting question is if it would not be a better course of action to build out high-speed rail to replace domestic air transit, and keep synth-fuel reserved exclusively for trans-oceanic flight. Trains are a solved problem, Japan, China and France show how it's done. No need to wait for miracles or SV billionaires - ffs, Hyperloop was (likely) only created to disturb the planning of California's HSR [1]! [1] https://jalopnik.com/did-musk-propose-hyperloop-to-stop-california-high-spee-1849402460 https://jalopnik.com/did-musk-propose-hyperloop-to-stop-cali...
    - ZeroGravitas 4y ago
      If we're talking outside of flight, then I think jumbo jet sized hydrfoil electric cargo ships will be an interesting challenger to both cargo flights and to larger cargo vessels. Trains are cool though. One big EU project currently is to connect up the train lines better across borders which are often still country centric in their network layout, which defaulted the medium distance capital to capital journeys to air transport.
    - chroma 4y ago
      California high speed rail is still being built. Hyperloop didn't have any impact beyond getting some people to think, "Why is this so expensive?" The CA HSR project was started in 2008, when voters passed Proposition 1A to provide $10 billion to fund high speed rail between SF and LA with a maximum travel time of 2 hours and 40 minutes. Initial estimates were that trains would be running by 2022 with the project completed by 2029 at a cost of $33 billion.[1] Construction started in 2015. Now the official projection is to have trains running between SF & LA in 2033 at a cost around $100 billion, though in reality the two cities will likely never be connected.[2] High speed rail doesn't make much sense in most of the US. The country is so big that most routes would take significantly longer than aircraft, even counting the extra time spent in security and traveling to/from the airport. 1. https://en.wikipedia.org/wiki/History_of_California_High-Speed_Rail#Construction https://en.wikipedia.org/wiki/History_of_California_High-Spe... 2. https://www.theguardian.com/us-news/2022/may/29/california-high-speed-rail-bullet-train https://www.theguardian.com/us-news/2022/may/29/california-h...
- pfdietz 4y ago
  Or synfuels from atmospheric CO2 capture, or laser power beaming.
- deleted 4y ago
  [deleted]
narrator 4y ago
Sure, hydrogen is not good compared to batteries as an energy storage medium, but making synthetic fuels from solar power is also massively inefficient. Biofuels is a huge waste of farmland, fertilizer, etc. This downside compared to batteries is why hydrogen will not be used in cars or boats, but the weight of hydrogen is a big enough advantage that it will probably be used in medium haul planes. Long haul planes will probably rely on biofuel or synfuel, but zeroavia.com claims they'll get to 5000 nm range eventually.
- pfdietz 4y ago
  Very long term, I'd bet (if I could live that long) on long haul planes powered by lasers from space.

by chroma 4y ago

_hypx 4y ago

Long-distance battery airplanes are literally impossible. If you don't agree with hydrogen powered aircraft, you are advocating for conventional airplanes forever.

jamiek88 4y ago
That’s ridiculously short sighted to think out only options are hydrogen or the status quo. Off the top of my head I can think of biofuels plus carbon neutral recaptured co2 from excess renewable energy. Diesel electric motors for example with the ‘diesel’ being carbon neutral biofuel. This is actually being tested on large airbus jets currently. Hydrogen is one of the worst possible options for aircraft. Energy density is crap, tankage is heavy, failure modes catastrophic.
- _hypx 4y ago
  Which would basically be conventional aircraft but running on biofuels or syn-fuels.
chroma 4y ago
I don't have a dog in this fight. I'm just explaining why hydrogen will never be popular. For a new technology to be adopted, it has to be better than the status quo. Compared to current aircraft, hydrogen costs more, has new safety concerns, and requires new infrastructure to transport and store the fuel. If that means aircraft will keep using fossil fuels, well then I guess we'll keep using fossil fuels.
nradov 4y ago
Forever is a long time, but our grandchildren will still be taking long-haul flights on conventional aircraft powered by turbine engines burning kerosene (possibly synthetic). The advantages of liquid hydrocarbons over hydrogen fuel are overwhelming in terms of safety, handling, and aerodynamics.
ZeroGravitas 4y ago
I think hydrogen (or something made from it) and fuel cells will win in the medium term. It's energy inefficient, but we're going to have a lot of cheap energy which will make lots of energy inefficient things reasonable, as long as you can store the output in some way. Having said that, with future automatiion, I do feel there's room for aircraft that combine and re-assemble themselves in mid air. For example, a VTOL tug that lifts off and starts a craft flying, but then detaches and returns to base. This can potentially be repeated on the landing side, and even mid-air "re-fueling" via battery drones. Possibly I just watched too many kids shows where vehicles did this and it's now my equivalent of the Jetson's flying cars. Feels like the next crazy project for Silicon Valley Billionaires to look into now that electric flight, jetpacks, rockets that land vertically etc. are all solved problems.
- mschuster91 4y ago
  The more interesting question is if it would not be a better course of action to build out high-speed rail to replace domestic air transit, and keep synth-fuel reserved exclusively for trans-oceanic flight. Trains are a solved problem, Japan, China and France show how it's done. No need to wait for miracles or SV billionaires - ffs, Hyperloop was (likely) only created to disturb the planning of California's HSR [1]! [1] https://jalopnik.com/did-musk-propose-hyperloop-to-stop-california-high-spee-1849402460 https://jalopnik.com/did-musk-propose-hyperloop-to-stop-cali...
  - ZeroGravitas 4y ago
    If we're talking outside of flight, then I think jumbo jet sized hydrfoil electric cargo ships will be an interesting challenger to both cargo flights and to larger cargo vessels. Trains are cool though. One big EU project currently is to connect up the train lines better across borders which are often still country centric in their network layout, which defaulted the medium distance capital to capital journeys to air transport.
  - chroma 4y ago
    California high speed rail is still being built. Hyperloop didn't have any impact beyond getting some people to think, "Why is this so expensive?" The CA HSR project was started in 2008, when voters passed Proposition 1A to provide $10 billion to fund high speed rail between SF and LA with a maximum travel time of 2 hours and 40 minutes. Initial estimates were that trains would be running by 2022 with the project completed by 2029 at a cost of $33 billion.[1] Construction started in 2015. Now the official projection is to have trains running between SF & LA in 2033 at a cost around $100 billion, though in reality the two cities will likely never be connected.[2] High speed rail doesn't make much sense in most of the US. The country is so big that most routes would take significantly longer than aircraft, even counting the extra time spent in security and traveling to/from the airport. 1. https://en.wikipedia.org/wiki/History_of_California_High-Speed_Rail#Construction https://en.wikipedia.org/wiki/History_of_California_High-Spe... 2. https://www.theguardian.com/us-news/2022/may/29/california-high-speed-rail-bullet-train https://www.theguardian.com/us-news/2022/may/29/california-h...
pfdietz 4y ago
Or synfuels from atmospheric CO2 capture, or laser power beaming.
deleted 4y ago
[deleted]

narrator 4y ago

Sure, hydrogen is not good compared to batteries as an energy storage medium, but making synthetic fuels from solar power is also massively inefficient. Biofuels is a huge waste of farmland, fertilizer, etc. This downside compared to batteries is why hydrogen will not be used in cars or boats, but the weight of hydrogen is a big enough advantage that it will probably be used in medium haul planes. Long haul planes will probably rely on biofuel or synfuel, but zeroavia.com claims they'll get to 5000 nm range eventually.

pfdietz 4y ago
Very long term, I'd bet (if I could live that long) on long haul planes powered by lasers from space.