4 ms·
Hydrogen looks good on paper but has a lot of practical issues. - Currently, the most economically efficient method to obtain hydrogen is by methane steam refo
by ggreer 4y ago
Hydrogen looks good on paper but has a lot of practical issues.
- Currently, the most economically efficient method to obtain hydrogen is by methane steam reforming. This releases a lot of CO2.
- If you want to get hydrogen without making CO2, you'll need to use electricity to split water. That's around 60-70% efficient. If you used the same electricity to charge a battery, it would be over 90% efficient.
- Hydrogen embrittlement is a problem for tanks and pipes. This means you can't easily repurpose natural gas infrastructure.
- Hydrogen has no odor, and adding an odorant can foul fuel cells. The most effective solution is to add hydrogen sensors everywhere, increasing costs.
- Hydrogen burns with an invisible flame. It's also much more easily ignited than gasoline and will burn in a wider range of concentrations. (Though unlike gasoline, it won't pool up.)
- Hydrogen is a small enough molecule that it will slowly permeate through a sealed tank. Newer tanks have coatings that reduce this, but research is ongoing.
- Remember the ideal gas law? The pressure change involved in refilling a hydrogen tank causes the nozzle to get very cold. Even in southern California this can freeze the nozzle to the tank, limiting refill speeds.
- Hydrogen is light, but tanks are heavy. The Toyota Mirai's tanks weigh 87.5kg but can only store 5kg of hydrogen.
Considering all of these disadvantages, I don't think hydrogen aircraft are going to happen.
- lucb1e 4y ago> Remember the ideal gas law? For anyone else who doesn't: https://en.wikipedia.org/wiki/Ideal_gas_law https://en.wikipedia.org/wiki/Ideal_gas_law "also called the general gas equation [...] is a good approximation of the behavior of many gases under many conditions". It seems to relate how pressure, volume and temperature interact (combined with some constant and how much gas there is). (Bit of a weird name; 'general gas equation' makes more sense to me.) But okay so this reference is about "know how gas behaves?" and actually seems to mean "gas gets cold when it expands", if I understand the comment correctly (since I didn't have this in school). Not sure why the tank you're filling can't just have the same pressure if this is a problem (plunger on both ends, push the gas over, don't let the available space expand or shrink).
- ggreer 4y agoTo transfer gas into a tank, it has to go from higher pressure to lower pressure. If the pressure is equal, you won't transfer any gas. Also an empty tank is pretty much at atmospheric pressure. Gas has to expand to pressurize it. The easiest solution is probably to add heating coils around the parts that get cold. I haven't heard of any the hydrogen filling stations having such devices, but that's probably because hydrogen stations are only in California.