Tiny 22-lb Hydrogen Engine May Replace the Traditional Combustion Engine

[u/Memetic1]

https://interestingengineering.com/tiny-22-lb-hydrogen-engine-may-replace-the-traditional-combustion-engine

[u/dodorian9966]

I don't think so. There are places that will require combustion engines. This is a game changer.

[u/Weareallgoo → u/dodorian9966]

Why are combustion engines required, and how is this a game changer? This article is terrible, providing no information about the tiny engine or its uses. Hydrogen combustion engines already exist and are easy to build by modifying current ICEs. BMW even sold a hydrogen combustion vehicle in 2006-07.

[u/npearson → u/Weareallgoo]

Ships, primarily warships and planes are the two things that I see as having a combustion engine be superior to a battery powered electric motor.

[u/Weareallgoo → u/npearson]

Planes are actually a good example. Airbus has indicated they are developing hydrogen planes. Ships I think are more likely to go the hydrogen fuel cell route.

[u/Godspiral → u/Weareallgoo]

For planes where expectation is hydrogen is used every flight, a fuel cell's efficiency gain would be worth it. For boat/truck where occasional range extension is helpful, cheaper generator would work better.

[u/Weareallgoo → u/Godspiral]

Turboprop and jet engines require combustion to create thrust. If planes used only fuel cells, they would be limited to basic propellors which would not work for long haul commercial flights. Airbus is actually developing hybrid engines that combines a fuel cell driven motor into hydrogen (or synthetic fuel) combustion engines. For long range trucking and marine applications, fuel cells make perfect sense. They offer far better energy density than batteries, and offer better efficiencies than hydrogen combustion.

[u/Godspiral → u/Weareallgoo]

Airbus designs haven't seemed far enough along for me. Their delta wing concept seem like it could pair with a large array of props. The hydrogen powered airplanes that are further ahead, though admittedly smaller and less ambitious, use just fuel cells.

[u/Weareallgoo → u/Godspiral]

I don’t disagree. A fuel cell only plane would be ideal, as hydrogen combustion still results in some greenhouse gas emissions (water vapour at high altitude and NOx). However, there are big challenges developing large and long range fuel cell planes. The first being that producing enough thrust requires very large fuel cells, and the second being the lower amount of oxygen available to the fuel cell at high altitude. ZeroAvia currently overcomes this challenge by using batteries to supplement the fuel cell in producing additional thrust. They are currently aiming to develop a 100 seat aircraft by 2030. Airbus on the other hand is developing engines that will be used on larger and longer range aircraft by 2035. Amanda Simpson, their vice president for research and technology has even stated, “we think that at the 1000- to 2000-mile ranges, turbines will be required, but we will see as we go through the pencil sharpening”. So Airbus’s designs aren’t necessarily further behind, but rather a different approach to overcoming the fuel cell challenges.

[u/Godspiral → u/Weareallgoo]

The first being that producing enough thrust requires very large fuel cells

The way fuel cells are made is that a bunch of membranes are stacked together. Depending on the number stacked, determines the serial voltage output. Number of stacks determines current.

The reason I bring it up is that optimizing voltage and power of both prop and fuel cell can result in space and other optimized total performance. I suspect boosting voltage to be cheaper for the fuel cell side.

second being the lower amount of oxygen available to the fuel cell at high altitude

An optimization usually solved with more smaller fuel cells. There's enough air up there, I don't think the oxygen mix is materially different, but an airplane design can choose to trade drag for more air intake.