This is a tiny fuel cell.
It runs on nothing but hydrogen and oxygen
and its exhaust is just water vapor.
You can use a bigger version of it to power a car.
Sounds great, right?
Hydrogen and oxygen in, water out, perfectly clean.
But, the hydrogen that fuels them,
that has to come from somewhere
and that somewhere might be a lot less green
than you think it is.
(upbeat music)
Oh.
So, how do hydrogen fuel cell cars actually work?
It's pretty different from a combustion engine
where gasoline and air are mixed in a cylinder
and compressed by a piston.
A spark plug ignites the gas and air causing
a tiny explosion.
These contained explosions push the piston.
Those pistons are connected to a crank shaft
which converts the linear motion of the piston
to a circular motion that drives your car.
Fuel cells work differently.
A hydrogen fuel cell is a lot like a sandwich.
You have an anode, or negative electrode
on one side, then there's an electrolyte
in the middle.
The electrolyte has protons that can move
between the two sides.
It could be a liquid electrolyte,
like sulfuric acid or a solid electrolyte
known as a proton exchange membrane.
And then, there's a cathode, or positive electrode
on the other.
Bread, meat, bread.
Hydrogen gas flows over the anode
where a catalyst, usually something
like platinum, splits it apart
into protons and electrons.
The protons flow right through
the proton exchange membrane electrolyte
to the cathode.
The electrons are also drawn toward the cathode
where they'll re-combine with the protons.
But, they can't get through the PEM.
Instead, the electrons leave the fuel cell
and take a different path through a circuit
powering an electric motor.
The motor turns the wheels,
your car moves, and the electrons
finally travel on to the cathode.
Air, which is about 21% oxygen,
flows over the cathode.
So when the proton and electron
from the hydrogen reach the other side
of the sandwich they can combine
with oxygen to form water.
Hydrogen and oxygen in, power and water out.
It seems pretty clean.
And honestly, this all kind of sounds
like magic to me in the way that some
of the best science just seems
too good to be true.
So, we're gonna try it out.
This is a hydrogen fuel cell.
I'm gonna use it to power this fan.
But first, I need to make some hydrogen.
Fuel cells can be run in reverse
a bit like a battery.
This means that if I push electricity
into the fuel cell I can use it to split
water inside into hydrogen and oxygen.
This is a process called electrolysis.
My dog's mad about here.
So, I'm gonna use this solar panel
and the relentless California sun
to create that electricity
and I could just use a battery,
but this is way more fun and renewable.
I'm gonna plug the solar panel
into the fuel cell.
Oh, hydrogen gas is coming out one side
of the fuel cell and filling up this container
and oxygen gas is coming out of this side
of the fuel cell and filling up this container.
Okay, so now that I've run my fuel cell
for a while and I have all the hydrogen I should need,
let's go back to the fan setup.
And the instructions are down there,
but I'm pretty sure when I plug in the fan
the fuel cell's gonna draw hydrogen
from here over the anode and oxygen
from here over the cathode and then ideally,
it's gonna split that hydrogen
into protons and electrons
and power the fan.
And it does.
Oh, this is so cool.
There's no battery here.
This isn't plugged in anywhere.
I used up all my hydrogen.
Now, in that little demo I used the sun
to make my hydrogen.
That makes this a really sustainable, clean
and green system.
And if that's where the hydrogen for cars
came from you would really have a near zero
emission vehicle, but unfortunately,
the most common method of making hydrogen fuel today
is natural gas reforming.
This means that hydrogen is coming from methane.
In reforming natural gas is reacted
with high pressure steam.
This creates something called synthesis gas,
a mix of hydrogen, carbon monoxide,
and carbon dioxide.
The carbon monoxide can be further reacted
with water to make even more hydrogen
and carbon dioxide.
And that Co2 and other impurities can then be removed
from the process to leave behind just the hydrogen.
The electrolysis process that breaks
the methane down is endothermic,
meaning you need to put heat into the system
to make it happen.
So, not only are you using methane
as your starting material, you need to put energy
into the process to get the hydrogen out,
and that energy is possibly coming
from even more fossil fuels.
But, this is still the cheapest
and most efficient method of making hydrogen fuel today.
It's also the most common.
And you can do pretty much this same process
with ethanol, gasoline, propane, coal,
not the cleanest fuels around.
If your goal is to get your Co2 emissions
as low as possible, this really isn't
doing it for you.
Now, you can make hydrogen by splitting water
like I did with my solar panel
in a process known as electrolysis,
and if you use solar or wind or other renewable sources
to do this it could be sustainable.
But, the huge demand for hydrogen from agriculture
and the semi conductor industries has made
it impossible to produce enough hydrogen
just from electrolysis and if you're using fossil fuels
to produce the hydrogen for cars
you're just shifting the carbon emission
further away from the vehicle, not eliminating it.
Currently, 96% of hydrogen is made from fossil fuels.
The production of hydrogen for all kinds
of industries, not just fuel cells,
is responsible for 830,000,000 tons
of carbon dioxide each year,
equivalent to the emissions of the UK
and Indonesia combined.
It's a real hydrogen downer.
So, is all hope for fuel cell cars lost?
Are they just gas guzzlers in disguise?
No.
Whether you're creating hydrogen
for a fuel cell or charging a battery
for an electric vehicle in the US at least,
most of your power is coming
from non-renewable sources.
But, energy production can be much more efficient
at large scale power plants than at the small scale
in the engine of your car.
The very best combustion engine car
is about 25% efficient at turning fuel into energy.
But, even coal power plants
beat that at over 40% efficiency.
And natural gas plants can get it up to about 60%.
So, even if it's a non-renewable source
it's often better to turn the energy into power
at a plant rather than inside your car.
But, you're not just storing that energy
in a battery for a fuel cell car.
Instead you're turning fossil fuels
into hydrogen, cooling and condensing it for storage
and transporting it releasing greenhouse gases
along the way.
Then you can finally use that hydrogen
to make power.
So while it's better than a combustion engine,
those extra steps mean it's still not
quite as efficient as a battery powered electric vehicle.
Hydrogen fuel cell vehicles do have
some advantages over traditional EVs though.
They fuel up just as fast as a gasoline powered engine
rather than the slow recharge times
of battery EVs, and they can have much longer ranges
because once you condense and compress
that hydrogen its energy density goes way up.
Look, I'm not ready to give up on hydrogen powered cars.
As we move towards more renewable energy sources
across our entire power grid, the prospect
of electrolysis based sustainable hydrogen
becomes way more realistic.
And there are some cool, new hydrogen production methods
under development, including direct solar water splitting.
This uses semi conductor materials like the ones found
in solar cells immersed in water to use solar energy
directly to turn H2O into hydrogen and oxygen.
There are some biochemical methods that use algae
to produce hydrogen from sunlight, too.
These methods aren't widespread yet
and they've got a long way to go
before they're ready to create
the hydrogen that powers a car or a semi truck.
But, this is about playing the long game,
not just looking at the problems of right now
and fuel cells could be a part
of more sustainable transportation.