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You cannot magically put electricity directly into the battery. There is a significant loss between production and powering the wheels. This is the biggest sour

by _hypx 3y ago

You cannot magically put electricity directly into the battery. There is a significant loss between production and powering the wheels. This is the biggest source of misunderstanding about the subject.

squaredot 3y ago
When the subject arise I usually point at the following interesting article https://ethz.ch/en/news-and-events/eth-news/news/2021/11/hydrogen-for-ground-transportation-and-heating-is-a-bad-idea.html https://ethz.ch/en/news-and-events/eth-news/news/2021/11/hyd...
- _hypx 3y ago
  That has nothing to do with the subject at hand. You cannot charge a battery at 100% efficiency, especially from the source electricity. People are simply creating an apples-to-oranges comparison here. You're just distracting from this fact.
  - djaychela 3y ago
    There are of course losses when charging a battery, but they are orders of magnitude larger when talking about the creation of hydrogen versus the charging of a battery. Hydrogen simply isn't a good idea for a number of reasons, and the energy needed to separate it from water is just one of them. Quoting "apples to oranges" here ignores the massive inefficiency in other stages of the process of storing and distribution of hydrogen, which is difficult and expensive to do. The distribution of electricity is much more efficient and cheaper.
    - _hypx 3y ago
      Factually no. There is no straightforward method of taking energy from renewable sources and getting it to a charging station. In reality, this is one of the hardest parts of green energy. You simply have to ask the question, "what happens when the wind is not blowing or the sun is not shining?" In fact, this is a total inversion of reality, bordering on science denial. The process of making and storing hydrogen is a straightforward process. It is trying to this with only electricity that is very hard.
      - _aavaa_ 3y ago
        > "what happens when the wind is not blowing or the sun is not shining?" You ramp up your hydro output and spread out and postpone the load. People have adapted to doing dishes and laundry when electricity is cheap, this is not different.
        _hypx 3y ago
        Hydro is energy storage. It incurs losses. It also requires you to have hydropower.
        _aavaa_ 3y ago
        > Which energy storage losses am I ignoring? Pumped hydro is energy storage that you have to put energy into to push water uphill. And yes it has losses, 25% losses round trip. If you have a hydroelectric damn however, you increase the flow when the sun doesn't shine or the wind doesn't blow and curtail it otherwise. > It also requires you to have hydropower. It's true. Just as wind turbines needs good wind, solar needs ample sunlight, and hydrogen proposals need large underground caverns.
        _hypx 3y ago
        If you are relying on wind and solar, then you will need energy storage. You will have to take the losses into account. You’ve already admitted this partially by acknowledging 25% losses with pumped hydro. But not everywhere has pumped hydro, nor hydropower at the scale needed. The point is that hydrogen gives you nearly lossless energy storage. This is why simplistic accounts of efficiency are simply wrong. People are ignoring energy storage losses on the BEV side, but always bring up the full cycle losses on the hydrogen side. This is an apples-to-oranges comparison, and gives you an invalid conclusion.
jillesvangurp 3y ago
Most batteries are around 90-95% efficient. Electrical motors are around 85-90% as well. So that isn't that bad. Of course most hydrogen vehicles are actually battery electrical vehicle where the battery is charged by the fuel cell. Reason for this is that fuel cells are not that easy to throttle up and down and typically have a lower output than the maximum input of the motor. So, you put enough battery in between the fuel cell and the motor so that you don't run out of energy when e.g. driving up a mountain. Also this enables benefiting from things like regenerative braking. Technically, you could take any hydrogen vehicle and convert it to pure battery electric by simply replacing the hydrogen bits and bops with a bigger battery. No need to change the drive train or anything else. It already is a battery electric vehicle. So a hydrogen car or truck inherits all those supposed (in)efficiencies of battery electric and then adds the additional (in)efficiencies of the hydrogen production, storage, transport, and fuel cell conversion. The whole process starts with the same renewable energy that you would otherwise put straight into the battery. So these are additional inefficiencies that go on top of the whole end to end chain. The further away you are from where the hydrogen is produced, the worse it gets. Anyway, when you multiply all of these efficiencies, you end up with a good reason why hydrogen cars are not a great idea from a cost point of view. Just a lot of losses in this long chain of energy conversions that you necessarily have to do that multiply to lots of energy loss. What this article proposes is super interesting of course but it doesn't change the math for transport. Battery electric is inherently more efficient. It works today and it's going to only get better. Cheaper more dense batteries, cheaper renewable energy production, etc. There are plenty of more sensible/economical uses for hydrogen outside transport.
- qwytw 3y ago
  >Most batteries are around 90-95% efficient. Electrical motors are around 85-90% as well. So that isn't that bad. I guess you'd also have take into account loss during transmission (which seesm to vary wildly between 2-10% depending on location) and charger efficiency. IIRC if we add it all up it's about 70%.
  - _hypx 3y ago
    With renewable energy, you will have to deal with intermittency too. That requires energy storage and more transmission losses.

by _hypx 3y ago

squaredot 3y ago

When the subject arise I usually point at the following interesting article https://ethz.ch/en/news-and-events/eth-news/news/2021/11/hydrogen-for-ground-transportation-and-heating-is-a-bad-idea.html https://ethz.ch/en/news-and-events/eth-news/news/2021/11/hyd...

_hypx 3y ago
That has nothing to do with the subject at hand. You cannot charge a battery at 100% efficiency, especially from the source electricity. People are simply creating an apples-to-oranges comparison here. You're just distracting from this fact.
- djaychela 3y ago
  There are of course losses when charging a battery, but they are orders of magnitude larger when talking about the creation of hydrogen versus the charging of a battery. Hydrogen simply isn't a good idea for a number of reasons, and the energy needed to separate it from water is just one of them. Quoting "apples to oranges" here ignores the massive inefficiency in other stages of the process of storing and distribution of hydrogen, which is difficult and expensive to do. The distribution of electricity is much more efficient and cheaper.
  - _hypx 3y ago
    Factually no. There is no straightforward method of taking energy from renewable sources and getting it to a charging station. In reality, this is one of the hardest parts of green energy. You simply have to ask the question, "what happens when the wind is not blowing or the sun is not shining?" In fact, this is a total inversion of reality, bordering on science denial. The process of making and storing hydrogen is a straightforward process. It is trying to this with only electricity that is very hard.
    - _aavaa_ 3y ago
      > "what happens when the wind is not blowing or the sun is not shining?" You ramp up your hydro output and spread out and postpone the load. People have adapted to doing dishes and laundry when electricity is cheap, this is not different.
      - _hypx 3y ago
        Hydro is energy storage. It incurs losses. It also requires you to have hydropower.
        _aavaa_ 3y ago
        > Which energy storage losses am I ignoring? Pumped hydro is energy storage that you have to put energy into to push water uphill. And yes it has losses, 25% losses round trip. If you have a hydroelectric damn however, you increase the flow when the sun doesn't shine or the wind doesn't blow and curtail it otherwise. > It also requires you to have hydropower. It's true. Just as wind turbines needs good wind, solar needs ample sunlight, and hydrogen proposals need large underground caverns.
        _hypx 3y ago
        If you are relying on wind and solar, then you will need energy storage. You will have to take the losses into account. You’ve already admitted this partially by acknowledging 25% losses with pumped hydro. But not everywhere has pumped hydro, nor hydropower at the scale needed. The point is that hydrogen gives you nearly lossless energy storage. This is why simplistic accounts of efficiency are simply wrong. People are ignoring energy storage losses on the BEV side, but always bring up the full cycle losses on the hydrogen side. This is an apples-to-oranges comparison, and gives you an invalid conclusion.

jillesvangurp 3y ago

Most batteries are around 90-95% efficient. Electrical motors are around 85-90% as well. So that isn't that bad. Of course most hydrogen vehicles are actually battery electrical vehicle where the battery is charged by the fuel cell. Reason for this is that fuel cells are not that easy to throttle up and down and typically have a lower output than the maximum input of the motor. So, you put enough battery in between the fuel cell and the motor so that you don't run out of energy when e.g. driving up a mountain. Also this enables benefiting from things like regenerative braking. Technically, you could take any hydrogen vehicle and convert it to pure battery electric by simply replacing the hydrogen bits and bops with a bigger battery. No need to change the drive train or anything else. It already is a battery electric vehicle. So a hydrogen car or truck inherits all those supposed (in)efficiencies of battery electric and then adds the additional (in)efficiencies of the hydrogen production, storage, transport, and fuel cell conversion. The whole process starts with the same renewable energy that you would otherwise put straight into the battery. So these are additional inefficiencies that go on top of the whole end to end chain. The further away you are from where the hydrogen is produced, the worse it gets. Anyway, when you multiply all of these efficiencies, you end up with a good reason why hydrogen cars are not a great idea from a cost point of view. Just a lot of losses in this long chain of energy conversions that you necessarily have to do that multiply to lots of energy loss. What this article proposes is super interesting of course but it doesn't change the math for transport. Battery electric is inherently more efficient. It works today and it's going to only get better. Cheaper more dense batteries, cheaper renewable energy production, etc. There are plenty of more sensible/economical uses for hydrogen outside transport.

qwytw 3y ago
>Most batteries are around 90-95% efficient. Electrical motors are around 85-90% as well. So that isn't that bad. I guess you'd also have take into account loss during transmission (which seesm to vary wildly between 2-10% depending on location) and charger efficiency. IIRC if we add it all up it's about 70%.
- _hypx 3y ago
  With renewable energy, you will have to deal with intermittency too. That requires energy storage and more transmission losses.