Comment on New fuel cell could enable electric aviation
Allero@lemmy.today 3 weeks ago
Is it really cheaper and more practical to produce sodium vs hydrogen?
The typical issue with fuel cells is not energy density, it is the fact that you need to waste a lot of energy to regenerate and transport the fuel. For example, if you take a classic hydrogen option, you can either get it from natural gas (which is not sustainable/eco-friendly) or from water (which is fully sustainable as you get a closed cycle, but comes with additional energy losses on electrolysis, transportation and usage).
So, overall, you’ll need to spend much more energy (= both recurring and upfront costs) compared to running battery-powered transportation if you want to make it a close cycle similar to batteries.
Rivalarrival@lemmy.today 3 weeks ago
I’ve never understood that thinking. Yes, it takes energy to produce fuel. So what? We started with a form of energy that couldn’t be stored and transported, and converted it to a form that could be. That’s the entire point.
That’s not actually true.
A 777 can carry up to 320,000 pounds of fuel, which gives it a 9000 mile range. It will land about 300,000 pounds lighter than it took off.
Build an electric version of the 777. Put enough batteries on board to make a 9000 mile flight, and it will weigh the same amount on landing as it did on takeoff.
Put that original 777 on the 2600 mile flight from LA to New York, and it doesn’t need a full fuel load. You can drop 200,000 pounds of fuel, and add 200,000 pounds of payload.
The e777 will still have the same weight of batteries needed for that 9000 mile flight.
Swap out the batteries with fuel cells, and you can take on an optimal, sub-maximal fuel load for your shorter flights, radically improving total efficiency over batteries.
Allero@lemmy.today 3 weeks ago
The point is, the efficiency of the entire process is much smaller compared to battery. Some estimates say that between electrolysis, transportation and fuel cell conversion it’s almost twice as bad in terms of energy efficiency, so you ultimately need double the energy for the same thing.
Sure, the math on planes is somewhat different as you need to account for battery weight. But really, it might still be more efficient to cram those batteries in. And as we know, it is still too bad to be usable.
Rivalarrival@lemmy.today 3 weeks ago
“The math is somewhat different” does not give adequate consideration to the importance.
That 777 I mentioned? The fuel weight on a maximum range flight is more than twice its remaining payload capacity. Fuel weight is the primary consideration you need to be looking at. The efficiency gains from charging batteries (relative to electrically-produced fuel) cannot justify the losses from their constant weight.
Allero@lemmy.today 3 weeks ago
Alright, that’s fair on your part.