Thread by @AukeHoekstra

A new study has done it again: 'prove' that fuel cell electric vehicles (FCEVs) emit less CO2 (8x less!) than battery electric vehicles (BEVs), even though they require roughly double the energy. ht @GEOosterom & @ArjandeKok1
Let me explain (again) why I think this is incorrect.

The study can be found here. juser.fz-juelich.de/record/842477/…

The trick they used is illustrated in figure 0-3: contrary to battery electric vehicles, hydrogen electric vehicles can use carbon free electricity because it would have been thrown away otherwise.

And this is the reasoning in words. Basically: with hydrogen you can use otherwise unusable electricity.

In the scenario imagined here we will build wind and solar that produces largely unusable energy. Fortunately we don't throw the energy away but store it as hydrogen. And that's why the hydrogen is totally carbon free.

That's nonsense.

Let's start with the sobering fact that currently, over 90% of hydrogen is made from natural gas and the CO2 emissions are similar to burning natural gas.

In the future that will probably change but I think it's good to keep in mind where we are right now.

Then, even in this scenario, the hydrogen storage would be part of the business case. The wind and solar would not have been build otherwise. Giving hydrogen a free pass is cheating.

But it goes further than that.

If you make models of such energy systems (like I do. see e.g. zenmo.com/en/virtual-lab…) you know that car charging is very flexible because they are parked 95% of the time. This allows them to absorb 'unusable' wind and solar more flexibly than any other application.

So in this respect BEVs and FCEVs are similarly flexible.

But of course the BEVs use half of the energy.
So 2x better, not 8x worse.

But it goes further than that.

It is true that in further away from the equator you encounter the situation of not only daily fluctuations (that you can absorb with battery electric vehicles) but also seasonal fluctuations and for that hydrogen is ideal. But pleas don't use it in cars!

Imagine Germany on 60% wind and 40% solar. There will be a need to store excess solar in summer and to have an energy reserve of about 2 months for periods with both little sun and wind. You could store that in hydrogen. Maybe you use 10% of energy supply for that.

Of course this energy is a bit more expensive because you have to pay for electrolysis equipment to create it, and you have to store it, and you have to turn it back into electricity, and you lose half of the energy in the process.
But it's worth it: you have 100% wind and solar.

Now the last thing you want to do is use this expensive seasonal buffer in vehicles that you can just as easily power using electricity, in which case you get the ability to dampen daily fluctuations and you only need half of the energy.

Replacing electric vehicles that absorb excess wind and solar with fuel cell vehicles that deplete your seasonal storage is really not the way to optimise your system and it is certainly not the least carbon intensive option.

If you want to read more about it you can also look at this take down I did of another study hyping hydrogen (also paid for by the hydrogen lobby). innovationorigins.com/fraunhofer-ise…

Now don't get me wrong: FCEVs are great compared to gasoline/diesel. And I do see futures in which hydrogen vehicles could be more energy efficient, even in Europe. E.g. we produce hydrogen in the Australian or African desert and transport it using pipelines or container ships.

A solar panel in the Sahara can deliver 5x more energy than in e.g. Germany so even if you lose 70% in the entire process, you could still 'beat' the battery electric vehicle charged with German solar.

But the difference would be small and it would only work if you are in a not so sunny country and your hydrogen comes from a very sunny country. In other situations the battery electric vehicle would emit less CO2. But they both beat diesel and gasoline by a mile.

In summary this study uses three faulty assumptions:

BEVs charge inflexibly

Hydrogen comes from 100% unusable and thus zero carbon energy

Vehicles are an appropriate use of precious hydrogen

All in all I'm a big fan of hydrogen and even if you waste it in vehicles it's still much cleaner than diesel or gasoline. I just don't like it that hydrogen proponents feel the need to use faulty logic to pretend it emits less CO2 than battery electric vehicles. They don't.

Correction: solar panels in the Sahara deliver ~2.2-2.5x the energy of solar panels in Germany. Not 5x.

https://twitter.com/aurelwuensch/status/1263525596824571905?s=20