4 ms·

Isn't H2 energy density much better than Li-Ion batteries? I don't understand why it's not applicable to transport if so.

JumpCrisscross 4y ago
> Isn't H2 energy density much better than Li-Ion batteries? By weight, hydrogen and oxygen creates 20x more chemical energy per kilogram than lithium-ion batteries [1]. (It's comparable to gasoline and air.) By volume, uncompressed, it has far less. Once compressed, we have to take into account the weight of the containment tanks, the weight of the fuel cell and the energy lost in converting hydrogen to electricity, an output batteries directly provide, a combination which negates that specific energy advantage. [1] https://en.wikipedia.org/wiki/Energy_density_Extended_Reference_Table https://en.wikipedia.org/wiki/Energy_density_Extended_Refere...
rgmerk 4y ago
H2 energy density is better than Li-Ion batteries, particularly by weight, but: * Hydrogen is very light but takes up quite a lot of volume so it needs to be either liquified or compressed to very high pressures (and even then it's considerably bulkier than, say, natural gas). * The resulting storage tanks are heavy and add bulk. * The fuel cell to convert the hydrogen to electricity adds weight that a battery system doesn't have (the storage is the converter). * The energy density of lithium-ion batteries doesn't have to match hydrogen or gasoline, it just has to be good enough. For most light vehicle applications, we're getting pretty close to that point (though possibly not if you're planning to use a truck to tow things). For heavy transport, the balance changes because big tanks are more mass-efficient than smaller ones, and the sheer mass of batteries currently required for long-haul trucking seriously cuts into the cargo that can be legally carried with road mass limits. That's why there's interest in hydrogen-fuelled trucks. For hydrogen-fuelled planes, a similar argument applies with current and reasonably foreseeable battery technology you can't build an airliner with a useful carrying capacity and range. However, the bulk of hydrogen tanks required for a plane with intercontinental range is still a big problem. That's why you see all these unconventional body design concepts for hydrogen-fuelled planes - you need lots of room to store the hydrogen and still give a useful passenger load.

JumpCrisscross 4y ago

> Isn't H2 energy density much better than Li-Ion batteries? By weight, hydrogen and oxygen creates 20x more chemical energy per kilogram than lithium-ion batteries [1]. (It's comparable to gasoline and air.) By volume, uncompressed, it has far less. Once compressed, we have to take into account the weight of the containment tanks, the weight of the fuel cell and the energy lost in converting hydrogen to electricity, an output batteries directly provide, a combination which negates that specific energy advantage. [1] https://en.wikipedia.org/wiki/Energy_density_Extended_Reference_Table https://en.wikipedia.org/wiki/Energy_density_Extended_Refere...

rgmerk 4y ago

H2 energy density is better than Li-Ion batteries, particularly by weight, but: * Hydrogen is very light but takes up quite a lot of volume so it needs to be either liquified or compressed to very high pressures (and even then it's considerably bulkier than, say, natural gas). * The resulting storage tanks are heavy and add bulk. * The fuel cell to convert the hydrogen to electricity adds weight that a battery system doesn't have (the storage is the converter). * The energy density of lithium-ion batteries doesn't have to match hydrogen or gasoline, it just has to be good enough. For most light vehicle applications, we're getting pretty close to that point (though possibly not if you're planning to use a truck to tow things). For heavy transport, the balance changes because big tanks are more mass-efficient than smaller ones, and the sheer mass of batteries currently required for long-haul trucking seriously cuts into the cargo that can be legally carried with road mass limits. That's why there's interest in hydrogen-fuelled trucks. For hydrogen-fuelled planes, a similar argument applies with current and reasonably foreseeable battery technology you can't build an airliner with a useful carrying capacity and range. However, the bulk of hydrogen tanks required for a plane with intercontinental range is still a big problem. That's why you see all these unconventional body design concepts for hydrogen-fuelled planes - you need lots of room to store the hydrogen and still give a useful passenger load.