5 ms·

A lot of the electric (mostly fuel cell) aviation startup industry is funded/supported by currently profitable aviation companies. The 1000hp motors for them ar

by kurthr 4y ago

A lot of the electric (mostly fuel cell) aviation startup industry is funded/supported by currently profitable aviation companies. The 1000hp motors for them are, like the airframes, one of the mostly off-the-shelf elements of their development. I agree that even modern batteries are pretty absurd for any human scale flight, though scaling laws make smaller aircraft more reasonable.

amelius 4y ago
Isn't synthetic fuel much more promising?
- jeffbee 4y ago
  Yeah they are, and this fact is just overlooked by people who aren't thinking through the implications of abundant renewable energy. With a surplus of renewable energy it makes much more sense to manufacture synthetic liquid fuels and burn them, than it does to power airplanes with batteries. The energy cycle is grossly inefficient but nobody is going to care because the energy inputs will be nearly cost-free.
  - frosted-flakes 4y ago
    I had that thought recently. Renewable energy sources like wind need a lot of energy storage. That is, unless you over-provision them so much that they can always meet demand even at peak times. This leaves you with over-production at other times, which could be used for other purposes that don't need to run continuously: synthetic jet fuel production, water desalination, etc. Basically, overprovision and then set electricity rates based on demand, and the renewable energy "storage problem" might just sort itself out. Of course, all those windmills and solar panels will cost an awful lot, so it might not be as simple as "overprovisioning".
    - Sebb767 4y ago
      > That is, unless you over-provision them so much that they can always meet demand even at peak times. Overprovisioning solar to power the grid on ice cold, windless new moon night is going to be hard. Having somewhere to put excess energy and some overprovisioning is always good, but it won't solve all storage problems.
      - aftbit 4y ago
        If we can build a superconducting grid, we can transport power from the parts of the planet where it is sunny or windy to the parts where it isn't. Assuming that everyone remains friendly and operational, that is.
  - zbrozek 4y ago
    CAISO hits about 100gCO2e/KWh during the day. And I run a solar surplus that I don't put back on the grid. I'd be really happy if there were a good way for me to turn excess electricity into something I could use later. Maybe that's hydrogen. Maybe that's capturing carbon and putting it into liquid fuels. Maybe that's creating graphite that I can use for fun personal projects. But regardless, I don't expect grid electricity prices to fall. Probably not in the US. Definitely not in CA.
- robonerd 4y ago
  From a CO2 perspective, synthetic fuels don't have an intrinsic advantage, unless you use biomass as your source of carbon. Traditionally, synthetic fuel has been made using coal or natural gas as the source of carbon. There is still some advantage to this, the nitrogen and sulfur content of the fuel can be dramatically reduced, which is great. But with regard to C02 specifically, you're basically burning coal. With biofuels, I think care needs to be taken to ensure we don't ruin the price of food for people by incentivizing farmers to grow fuel feedstock instead. Biofuels made from algae might be the best, since this wouldn't require the use of arable farmland. Another approach is to pull the CO2 straight out of sea water. Apparently the US Navy thinks this might be a viable approach, since their nuclear aircraft carriers have power to spare.
  - sky-kedge0749 4y ago
    I recently commented about synthetic jet fuel in another thread https://news.ycombinator.com/item?id=31704829 https://news.ycombinator.com/item?id=31704829: > A problem with biofuel is scaling it up, see: https://ieeexplore.ieee.org/document/7498153 https://ieeexplore.ieee.org/document/7498153. According to that article the U.S. would need to devote "an area bigger than Texas and California and Pennsylvania combined" to crops specifically for its own jet biofuel needs. That's just for flying, not for food or fuel for ground transportation or anything else. Also that article says that from 2009-2013 a $100 million effort was made to figure out how to get sufficient synthetic fuel from algae but they eventually gave up and went back to the drawing board.
    - ncmncm 4y ago
      Biofuel is an obvious dead end. The future has no place for biofuel in any substantial amount.
      - trashtester 4y ago
        Ethanol made from food (like corn) is a dead end. Firewood and derivatives have always had an important place in heating and cooking, and are likely to continue in that role for a while. Other types of biomass based hard fuels (from recycled garbage/waste, algae, etc) will most likely also play a role in electricity production and heating, but perhaps a small one (unless algae based biomass takes off). And for liquid fuels for transportation use, algae may also end up being a competitor to hydrogen when oil runs out. I remember there were a lot of companies working in that space 10 years ago, but then there was the oil price crash in 2015, and it seems many switched away. For instance algenol was positioning itself as a fuel company, but appear to have diversified: https://www.algenol.com/sustainable-products/?category=ndustrials https://www.algenol.com/sustainable-products/?category=ndust... If oil prices remain at current levels, though, algae may be only a few years away from scaling up to take a significant part of the market.
- hannob 4y ago
  There's been an EU funded research project that did some projections on the electricity needed for e-fuels. See the graphic on page 44: https://www.fch.europa.eu/sites/default/files/FCH%20Docs/20200507_Hydrogen%20Powered%20Aviation%20report_FINAL%20web%20%28ID%208706035%29.pdf https://www.fch.europa.eu/sites/default/files/FCH%20Docs/202... For pure e-fuels they project 32 PWh. That is, to put it in perspective, more than the total world electricity production today. You'll want to use every technology available to do this in a more efficient way - batteries for very short ranges, hydrogen for mid ranges, e-fuels only for long range where nothing else works. It'll still be very challenging and likely the current growth projections of the aviation industry will be seen as unrealistic fantasies at some point in the future.
  - lukeschlather 4y ago
    > For pure e-fuels they project 32 PWh. That is, to put it in perspective, more than the total world electricity production today. Total annual electricity production is 161 PWh. THe PDF you linked puts it in perspective by saying that if it were purely powered by renewable energy it would increase the size of the renewable energy sector by 3 to 5 times. In other words this doesn't sound hard at all from an electricity standpoint. If electrical generation were half the cost it would be economical right now.
    - moby_click 4y ago
      From https://pubs.rsc.org/en/content/articlelanding/2020/se/c9se00479c https://pubs.rsc.org/en/content/articlelanding/2020/se/c9se0... > We find that an electricity emissions factor of less than 139 g CO2e per kW h is required for this [Direct Air Capture system paired with Fischer–Tropsch synthesis] pathway to provide a climate benefit over conventional diesel fuel. The grid averages in most regions are higher than that. I don't think multiplying current renewable generation just for jet fuel is easy.
- bbojan 4y ago
  Burning any fuel in our atmosphere produces nitrous oxides. Synthetic/carbon neutral fuels won't help with that.
  - SoftTalker 4y ago
    These can possibly be addressed by catalytic converters in the exhaust (not sure how feasible that is in a turbine engine though). In any event, it's a small fraction of total greenhouse emissions, dwarfed by CO2. Let's not let perfect be the enemy of good.
    - bbojan 4y ago
      Oh I wasn't concerned about their greenhouse effect contribution. NOx can cause asthma and bronchitis and can aggravate pre-existing heart conditions. They also form smog. Did I mention that they are bad for the ozone layer?

by kurthr 4y ago

amelius 4y ago

Isn't synthetic fuel much more promising?

jeffbee 4y ago
Yeah they are, and this fact is just overlooked by people who aren't thinking through the implications of abundant renewable energy. With a surplus of renewable energy it makes much more sense to manufacture synthetic liquid fuels and burn them, than it does to power airplanes with batteries. The energy cycle is grossly inefficient but nobody is going to care because the energy inputs will be nearly cost-free.
- frosted-flakes 4y ago
  I had that thought recently. Renewable energy sources like wind need a lot of energy storage. That is, unless you over-provision them so much that they can always meet demand even at peak times. This leaves you with over-production at other times, which could be used for other purposes that don't need to run continuously: synthetic jet fuel production, water desalination, etc. Basically, overprovision and then set electricity rates based on demand, and the renewable energy "storage problem" might just sort itself out. Of course, all those windmills and solar panels will cost an awful lot, so it might not be as simple as "overprovisioning".
  - Sebb767 4y ago
    > That is, unless you over-provision them so much that they can always meet demand even at peak times. Overprovisioning solar to power the grid on ice cold, windless new moon night is going to be hard. Having somewhere to put excess energy and some overprovisioning is always good, but it won't solve all storage problems.
    - aftbit 4y ago
      If we can build a superconducting grid, we can transport power from the parts of the planet where it is sunny or windy to the parts where it isn't. Assuming that everyone remains friendly and operational, that is.
- zbrozek 4y ago
  CAISO hits about 100gCO2e/KWh during the day. And I run a solar surplus that I don't put back on the grid. I'd be really happy if there were a good way for me to turn excess electricity into something I could use later. Maybe that's hydrogen. Maybe that's capturing carbon and putting it into liquid fuels. Maybe that's creating graphite that I can use for fun personal projects. But regardless, I don't expect grid electricity prices to fall. Probably not in the US. Definitely not in CA.
robonerd 4y ago
From a CO2 perspective, synthetic fuels don't have an intrinsic advantage, unless you use biomass as your source of carbon. Traditionally, synthetic fuel has been made using coal or natural gas as the source of carbon. There is still some advantage to this, the nitrogen and sulfur content of the fuel can be dramatically reduced, which is great. But with regard to C02 specifically, you're basically burning coal. With biofuels, I think care needs to be taken to ensure we don't ruin the price of food for people by incentivizing farmers to grow fuel feedstock instead. Biofuels made from algae might be the best, since this wouldn't require the use of arable farmland. Another approach is to pull the CO2 straight out of sea water. Apparently the US Navy thinks this might be a viable approach, since their nuclear aircraft carriers have power to spare.
- sky-kedge0749 4y ago
  I recently commented about synthetic jet fuel in another thread https://news.ycombinator.com/item?id=31704829 https://news.ycombinator.com/item?id=31704829: > A problem with biofuel is scaling it up, see: https://ieeexplore.ieee.org/document/7498153 https://ieeexplore.ieee.org/document/7498153. According to that article the U.S. would need to devote "an area bigger than Texas and California and Pennsylvania combined" to crops specifically for its own jet biofuel needs. That's just for flying, not for food or fuel for ground transportation or anything else. Also that article says that from 2009-2013 a $100 million effort was made to figure out how to get sufficient synthetic fuel from algae but they eventually gave up and went back to the drawing board.
  - ncmncm 4y ago
    Biofuel is an obvious dead end. The future has no place for biofuel in any substantial amount.
    - trashtester 4y ago
      Ethanol made from food (like corn) is a dead end. Firewood and derivatives have always had an important place in heating and cooking, and are likely to continue in that role for a while. Other types of biomass based hard fuels (from recycled garbage/waste, algae, etc) will most likely also play a role in electricity production and heating, but perhaps a small one (unless algae based biomass takes off). And for liquid fuels for transportation use, algae may also end up being a competitor to hydrogen when oil runs out. I remember there were a lot of companies working in that space 10 years ago, but then there was the oil price crash in 2015, and it seems many switched away. For instance algenol was positioning itself as a fuel company, but appear to have diversified: https://www.algenol.com/sustainable-products/?category=ndustrials https://www.algenol.com/sustainable-products/?category=ndust... If oil prices remain at current levels, though, algae may be only a few years away from scaling up to take a significant part of the market.
hannob 4y ago
There's been an EU funded research project that did some projections on the electricity needed for e-fuels. See the graphic on page 44: https://www.fch.europa.eu/sites/default/files/FCH%20Docs/20200507_Hydrogen%20Powered%20Aviation%20report_FINAL%20web%20%28ID%208706035%29.pdf https://www.fch.europa.eu/sites/default/files/FCH%20Docs/202... For pure e-fuels they project 32 PWh. That is, to put it in perspective, more than the total world electricity production today. You'll want to use every technology available to do this in a more efficient way - batteries for very short ranges, hydrogen for mid ranges, e-fuels only for long range where nothing else works. It'll still be very challenging and likely the current growth projections of the aviation industry will be seen as unrealistic fantasies at some point in the future.
- lukeschlather 4y ago
  > For pure e-fuels they project 32 PWh. That is, to put it in perspective, more than the total world electricity production today. Total annual electricity production is 161 PWh. THe PDF you linked puts it in perspective by saying that if it were purely powered by renewable energy it would increase the size of the renewable energy sector by 3 to 5 times. In other words this doesn't sound hard at all from an electricity standpoint. If electrical generation were half the cost it would be economical right now.
  - moby_click 4y ago
    From https://pubs.rsc.org/en/content/articlelanding/2020/se/c9se00479c https://pubs.rsc.org/en/content/articlelanding/2020/se/c9se0... > We find that an electricity emissions factor of less than 139 g CO2e per kW h is required for this [Direct Air Capture system paired with Fischer–Tropsch synthesis] pathway to provide a climate benefit over conventional diesel fuel. The grid averages in most regions are higher than that. I don't think multiplying current renewable generation just for jet fuel is easy.
bbojan 4y ago
Burning any fuel in our atmosphere produces nitrous oxides. Synthetic/carbon neutral fuels won't help with that.
- SoftTalker 4y ago
  These can possibly be addressed by catalytic converters in the exhaust (not sure how feasible that is in a turbine engine though). In any event, it's a small fraction of total greenhouse emissions, dwarfed by CO2. Let's not let perfect be the enemy of good.
  - bbojan 4y ago
    Oh I wasn't concerned about their greenhouse effect contribution. NOx can cause asthma and bronchitis and can aggravate pre-existing heart conditions. They also form smog. Did I mention that they are bad for the ozone layer?