https://thedriven.io/2020/06/04/hydrogen-cars-wont-overtake-electric-vehicles-because-theyre-hampered-by-laws-of-science/
Hydrogen cars won’t overtake electric vehicles because they’re hampered by
laws of science
June 4, 2020 Tom Baxter
[images
https://images.theconversation.com/files/339188/original/file-20200602-133910-1dlknyt.png
energy vector transition
https://images.theconversation.com/files/339187/original/file-20200602-133924-1qb51y5.png
Energy efficiency in electric vehicles
]
Hydrogen has long been touted as the future for passenger cars. The hydrogen
fuel cell electric vehicle (FCEV), which simply runs on pressurised hydrogen
from a fuelling station, produces zero carbon emissions from its exhaust.
It [fcv] can be filled as quickly as a fossil-fuel equivalent and offers a
similar driving distance to petrol [ice]. It has some heavyweight backing,
with Toyota for instance launching the second-generation Mirai [
http://electric-vehicle-discussion-list.413529.n4.nabble.com/OT-Recall-all-Mirai-fcvs-h2-fcv-tech-Comes-Under-Fire-tp4685832p4695208.html
] later in 2020.
The Canadian Hydrogen and Fuel Cell Association recently produced a report
extolling hydrogen vehicles. Among other points, it said that the carbon
footprint is an order of magnitude better than electric vehicles: 2.7g of
carbon dioxide per kilometre compared to 20.9g.
All the same, I think hydrogen fuel cells are a flawed concept. I do think
hydrogen will play a significant role in achieving net zero carbon emissions
by replacing natural gas [methane, CH4] in industrial and domestic heating.
But I struggle to see how hydrogen can compete with [battery] electric
vehicles, and this view has been reinforced by two recent pronouncements.
A report by BloombergNEF concluded [
https://data.bloomberglp.com/professional/sites/24/BNEF-Hydrogen-Economy-Outlook-Key-Messages-30-Mar-2020.pdf
]:
The bulk of the car, bus and light-truck market looks set to adopt
(battery electric technology), which are a cheaper solution than fuel cells.
Volkswagen [
https://www.volkswagen-newsroom.com/en/stories/battery-or-fuel-cell-that-is-the-question-5868
], meanwhile, made a statement comparing the energy efficiency of the
technologies. “The conclusion is clear” said the company. “In the case of
the passenger car, everything speaks in favour of the battery and
practically nothing speaks in favour of hydrogen.”
Hydrogen’s efficiency problem
The reason why hydrogen is inefficient is because the energy must move from
wire to gas to wire in order to power a car. This is sometimes called the
energy vector transition.
Let’s take 100 watts of electricity produced by a renewable source such as a
wind turbine. To power an FCEV, that energy has to be converted into
hydrogen, possibly by passing it through water (the electrolysis [
https://www.bbc.co.uk/bitesize/guides/zpxn82p/revision/1
] process). This is around 75% energy-efficient, so around one-quarter of
the electricity is automatically lost.
The hydrogen produced has to be [cleaned/filtered,] compressed, chilled and
transported to the hydrogen station, a process that is around 90% efficient.
Once inside the vehicle, the hydrogen needs converted into electricity,
which is 60% efficient. Finally the electricity used in the motor to move
the vehicle is is around 95% efficient. Put together [
https://www.eesi.org/papers/view/energy-storage-2019
], only 38% of the original electricity – 38 watts out of 100 – are used
[/available
https://www.californiahydrogen.org/wp-content/uploads/files/doe_fuelcell_factsheet.pdf
].
With electric vehicles, the energy runs on wires all the way from the source
to the car. The same 100 watts of power from the same turbine loses about 5%
of efficiency in this journey through the grid (in the case of hydrogen, I’m
assuming the conversion takes place onsite at the wind farm).
You lose a further 10% of energy from charging and discharging the
lithium-ion battery, plus another 5% from using the electricity to make the
vehicle move. So you are down to 80 watts – as shown in the figure opposite.
Energy efficiency in electric vehicles.
In other words, the hydrogen fuel cell requires double the amount of energy.
To quote BMW [
https://www.bmw.com/en/innovation/how-hydrogen-fuel-cell-cars-work.html
]: “The overall efficiency in the power-to-vehicle-drive energy chain is
therefore only half the level of (an electric vehicle).”
Swap shops ...
Finally a word on the claims on carbon emissions from that Canadian Hydrogen
and Fuel Cell Association report I mentioned earlier. I checked the source [
https://juser.fz-juelich.de/record/842477/files/Energie_Umwelt_408_NEU.pdf
] of the statistics, which revealed they were comparing hydrogen made from
purely renwewable electricity with electric vehicles powered by electricity
from fossil fuels.
If both were charged using renewable electricity, the carbon footprint would
be similar. The original report was funded by industry consortium H2
