Using the same underlying chemistry that propels spacecraft, hydrogen cars could still become the car of the future.
Right now, you could get behind the wheel of a car that burns zero fossil fuels and produces zero pollution or greenhouse gases, runs on the same chemical reaction that powers rockets, and gets twice as much mileage as a Tesla. It’s called a hydrogen fuel-cell vehicle, but unless you live in California, you may have never seen one on the road.
These days, electric cars driven by batteries seem destined to rule our roads, while hydrogen cars—once toasted as the vehicle of the future—are rare and relatively unheralded. Fuel cells actually have lots of advantages over the competition, including better mpg or faster refueling times. So what happened to hydrogen cars?
How It Works
The first thing you should know is, hydrogen cars are electric cars. We tend to think of EVs only in terms of battery-powered vehicles like Teslas and the Nissan Leaf, but despite the fact that they run on a liquid fuel, hydrogen fuel cells actually power their vehicles with electricity. “When we talk about electric cars, that includes plug-in hybrids, hybrids, battery electrics, fuel cells, and anything else that may come along later that still uses an electric motor,” says Keith Wipke, laboratory program manager for fuel cell and hydrogen technologies at the National Renewable Energy Laboratory.
But a fuel cell is much different than a battery. The hulking lithium-ion battery in the belly of a Tesla Model S stores electrical energy as a voltage across an anode and cathode. A fuel cell produces electricity by means of electrochemical reactions between a fuel, typically hydrogen, and the oxygen in the air. During the reaction, hydrogen and oxygen combine to produce electrical energy and harmless water vapor as a byproduct. If that initial chemical reaction is large enough, it can move an entire vehicle.
This dance of mechanics and chemistry is similar to the hydrogen-oxygen reaction that powers rocket engines (you may remember it from The Martian). In this case the energy produced by the reaction is run through an electrolyzer and produces electricity instead of an explosion. In both cases, an extreme amount of energy is released with no toxic byproducts, which is what makes hydrogen fuel cells such a great power source for electric vehicles.
The hydrogen itself can be produced by running this process in reverse, which is called electrolysis. Running an electrical current through water separates the H2O into hydrogen and oxygen. More commonly, however, hydrogen is produced at scale from natural gas in a process called steam-methane reforming, in which high-temperature and high-pressure steam is combined with natural gas to create hydrogen.
This process does produce some carbon dioxide, so the hydrogen fuel itself isn’t 100 percent clean. But it compares favorably with CO2 emissions related to battery electrics and hybrids, and it’s obviously better than any fossil fuel vehicle in terms of environmental impact.
Currently, the state of California mandates that at least 33 percent of the hydrogen that goes into vehicles has to come from renewable sources, with the hope of eventually marching toward 100 percent renewable energy. That brings fuel-cell vehicles in line with battery electrics running off grid power, as California’s grid is mandated to be 33 percent renewable by 2020.