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. 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 crankshaft, 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, 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 recombine 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 onto 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. So 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 I'm out here. So I'm going to 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 going to 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 and gas is coming out of this side of the fuel cell and filling up this container. OK, 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 is going to draw hydrogen from here over the anode and oxygen from here over the cathode. And then ideally, it's going to split that hydrogen into protons and electrons and power the fan. And it does!
Oh, this is so cool. There is 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 the 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 semiconductor 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 million 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 or 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 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.
So 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 semiconductor 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 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.