Liquid hydrogen on planes is a cool proof of concept but not much more. The volumetric energy density of liquid hydrogen is about 1/5 that of jet fuel and the thermal efficiency of the engine will remain essentially constant whether burning jet fuel or hydrogen. This means that we would need fuel tanks that have 4.4x the capacity to maintain the same range.
The energy density is what it is and cannot change. The thermal efficiency of the engine is subject to incremental improvement but don't expect anything major, this is mature tech operating close to theoretical limits. Hydrogen has all kinds of great applications but aviation likely isn't one. But hey, s-curves on top of s-curves, maybe we discover something we never thought possible.
This was kind of my feeling on it, which is why I expected synfuels/biofuels, but part of me wonders if in a few decades new planes may not be pretty different -- flying wings or whatever -- and have more volume for fuel while being more efficient. I don't know the answer, but it's one question I have.
That's a great point, the shape of future planes may be very different than what we're used to today.
We could take up some of the cargo volume with hydrogen tanks, this would likely push up the cost of flying but maybe customers are willing to accept this tradeoff for a carbon neutral flight.
And things could be quite different by then.. If we have fusion breakthroughs or just tons of really low cost solar/wind/nuclear in a few decades, generating vast quantities hydrogen at really low cost may be possible, so you'd cary more fuel, but at a lower cost per unit of energy than fossil fuels, especially if by then there are heavier carbon taxes.. (maybe ¯\_(ツ)_/¯ ).
Liquid hydrogen on planes is a cool proof of concept but not much more. The volumetric energy density of liquid hydrogen is about 1/5 that of jet fuel and the thermal efficiency of the engine will remain essentially constant whether burning jet fuel or hydrogen. This means that we would need fuel tanks that have 4.4x the capacity to maintain the same range.
The energy density is what it is and cannot change. The thermal efficiency of the engine is subject to incremental improvement but don't expect anything major, this is mature tech operating close to theoretical limits. Hydrogen has all kinds of great applications but aviation likely isn't one. But hey, s-curves on top of s-curves, maybe we discover something we never thought possible.
This was kind of my feeling on it, which is why I expected synfuels/biofuels, but part of me wonders if in a few decades new planes may not be pretty different -- flying wings or whatever -- and have more volume for fuel while being more efficient. I don't know the answer, but it's one question I have.
Thanks for the great comments! 💚 🥃
That's a great point, the shape of future planes may be very different than what we're used to today.
We could take up some of the cargo volume with hydrogen tanks, this would likely push up the cost of flying but maybe customers are willing to accept this tradeoff for a carbon neutral flight.
And things could be quite different by then.. If we have fusion breakthroughs or just tons of really low cost solar/wind/nuclear in a few decades, generating vast quantities hydrogen at really low cost may be possible, so you'd cary more fuel, but at a lower cost per unit of energy than fossil fuels, especially if by then there are heavier carbon taxes.. (maybe ¯\_(ツ)_/¯ ).
I think/hope you're right. The future is exciting.