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Fueling Your Car With Hydrogen Isn’t Green–It’s Gray

Manufacturers are investing in it, but the benefits compared to other forms of car power are mixed

5 min read

A green car with "F-Cell world drive" on the back.
Image credit: Teymur Madjderey // CC BY-NC-ND 2.0

Contrary to popular belief, there’s no such thing as a hydrogen car. When people talk about hydrogen cars, they’re usually talking about hybrids–hydrogen fuel cell electric vehicles, or HFCEVs. These are half electric car, half hydrogen fuel cell–with the fuel cell essentially buckled to the battery. And they could become a vital bridge to a carbon-free future.

Fuel cells make electricity in chemical reactions that don’t involve setting the fuel on fire. Instead, they directly convert the energy stored in chemical bonds to electricity. While a conventional electric vehicle requires you to recharge for about eight hours to go from empty to full, a hydrogen vehicle allows you to fill up the tank like a petrol car. The fuel then runs into the fuel cell, reacts to make electricity, and charges the battery as you go along.

Fuel cells can work with many fuels, but hydrogen is both the most abundant element in the universe and has the highest energy density–almost three times that of petrol. Hydrogen combustion engines actually predate petrol combustion engines by 50 years: The first one was built in 1807 by Isaac de Rivaz, a Franco-Swiss artillery officer turned inventor. The de Rivaz engine looked pretty homemade compared to today’s models. Originally designed as an engine-powered pump, it came complete with levers, pulleys, ropes, and a manually operated electric spark plug to ignite the fuel, supplied from a large balloon.

This was not the only early predecessor of the modern hydrogen hybrid car. Back in the days when steam was competing with electricity and combustion engines as a power source, New England builder Knight Neftal constructed a gasoline-electric hybrid car and raced it over 100 miles. Back then, that was an endurance race–cars just weren’t expected to stand up to this kind of distance. In fact, Neftal’s vehicle must have been exceptional for the time, because most hybrids simply lacked the driving range to appeal to the wealthy and privileged–really the only people who could afford them. People like the Sultan of the Ottoman Empire had one, though–he was probably the earliest famous person to travel in a hybrid carriage in 1888.

Although some manufacturers did attempt to popularize hybrid travel (George Fischer built and ran hybrid buses on the streets of England in 1901), it wasn’t until the advent of Henry Ford’s company in 1904 that cars became accessible to everybody. Overcoming the challenges of noise, vibration, and odor (to some extent), he eventually introduced mass production, making enough light, cheap, gasoline-powered cars to extinguish the electric market. Hybrids were put on the back burner–for a while.

Bubbles in water.

Mass-produced hydrogen is already cheap–around a dollar per gallon–and used in industries from margarine to circuit boards for electronics. Aman Dhir of the Centre for Hydrogen and Fuel Cell Research at the University of Birmingham in the United Kingdom believes the cost will drop further if hydrogen fuel cars flood the market, maybe to as little as one tenth of what it is now.

But hydrogen is made rather than found. It’s an element that is so reactive it’s almost always bound up in chemical compounds, and has to be released before it can be used. When compared to how we get gasoline and coal, this isn’t necessarily a problem–synthesizing chemicals in a lab is often cheaper and less environmentally damaging than mining or drilling. In reality, though, 96 percent of our hydrogen comes directly from fossil fuels–chiefly methane–and is extracted using steam. Because breaking materials down emits energy, natural gas supplied to homes can be converted to hydrogen on-site and used for space heating–as well as provide hydrogen for electrical fuel cells. But it’s certainly not carbon neutral; it’s been nicknamed a “gray” rather than “green” resource. Also, many of the materials used to manufacture parts such as fuel cells are toxic and impact the environment.

On the other hand, all energy resources leave a carbon footprint, even renewables. Hydrogen hybrids currently show the lowest carbon footprint for medium to large vehicles like 4x4s, as well as contribute to improved local air quality–the only thing that comes out of the exhaust pipe is water.

Carbon-free methods of producing hydrogen do exist. One common method, the electrolysis of water, is basically the reverse of what happens in a fuel cell–purified water and electricity go in, and hydrogen and oxygen come out. This method contributes four percent of global hydrogen production and the hydrogen produced is extremely pure (more than 99.9999 percent), but the price reflects this. It also means no new energy is made–it’s just like a battery: handy for storing energy that can’t be used immediately.

More zero-carbon methods of making hydrogen are being developed, too. These include photolysis–the conversion of solar energy into hydrogen within plants, and photocatalysis, a chemical equivalent. There are also other technologies, including solar energy and biofuels. Each comes with a different balance of cost, performance, and infrastructure requirements.

Clouds over the sea.

Let’s talk about the vehicles themselves. In terms of cost, hydrogen cars perform badly: Around $73,000, they are almost twice the diesel equivalent–despite massive subsidies. However, the technology is lightweight with no moving parts, so seldom malfunctions. While the weight of the battery and charging method limit many pure electric vehicles to short urban trips between 25 to 37 miles a day [40″”60 kilometers], hybrid hydrogen cars have about the same range as their diesel and petrol counterparts. The main challenge for hydrogen is durability: Typical petrol and diesel cars have a lifespan of 5,000 hours. At this stage, researchers just don’t know if the hydrogen equivalents can last this long; more test driving under different climatic conditions is required.

It’s also quite hard to fuel your hydrogen car right now. While you can charge an electric vehicle in your garage, there are still only 55 hydrogen refueling stations in Europe and about 58 in the United States. Dhir thinks it’s policy that is the real barrier, not infrastructure. “It’s more about land permission because you have a change of use,” he told me, “and then you’ve got your safety measures because it’s an emerging technology.” New hydrogen refueling stations are already in the works, which includes plans for getting the hydrogen to them in the first place, but the infrastructure requirements put the technology at a disadvantage over its competitors.

This, of course, is another issue altogether. Although hydrogen packs a lot of energy for its weight, it’s a gas–so it takes up a lot of space. While seven kilograms of hydrogen produces as much fuel energy as 21 kilograms of gasoline (enough to almost fill a normal 16-gallon gas tank), the tank you’d need to hold that hydrogen would occupy 2,966 cubic feet [84 cubic meters]. A tank that size would look like a hot air balloon suspended above the car, more than twice as long as the vehicle itself.

There are two options for getting the gas to take up less space–chilling it down to -420° F [-252° C], where it turns into a liquid, or storing it under high pressures of 350 or 700 bar. High pressures usually win–it’s more dangerous but uses less energy than cryogenic storage, and can also be delivered straight into the fuel tank of your car. As a safety precaution, high-pressure hydrogen tanks are designed with deliberate leaks, so excess hydrogen boils off rather than builds up pressure. However, this means about four percent of the hydrogen disappears every day.

But do you really want to be hurtling around with high-pressure hydrogen between you and your bumper? Dhir reassured me: “It’s a gas tank made of Kevlar and whatnot–it’s bulletproof,” he said. “It’s hideously safe when you compare it to your petrol plastic tank in your car. Your plastic tank in your car would rupture after four minutes if you’re in an accident, and this you could put a bomb in it and it wouldn’t go up. So it’s been over-designed.”

Some researchers, including Dhir, are also looking into storing hydrogen in solids, where the atoms can pack more closely together than liquids without presenting a pressure risk. However, even the lightest solid oxide fuel cells tend to be relatively heavy (which makes a car less efficient) and operate at high temperatures. Dhir’s research unit is looking at high-temperature solid oxide fuel cells for use in aircraft rather than road vehicles.

Despite these ups and downs, car manufacturers are investing heavily in hydrogen technology in an effort to support targets for reduced emissions. In 2015, Toyota decided to share 6,000 of its hydrogen fuel cell patents to boost competition, and the German consortium H2 Mobility is aiming to build 400 hydrogen refueling stations by 2023.

Market investment is essential for continued development, but with looming climate change the question is not why, but why not? Hydrogen is the ultimate compromise industry–combining cutting-edge fuel and battery technologies to get even more power out of the fossil fuels we have long relied on. It requires minimal lifestyle changes for drivers and, unlike fossil fuels, is flexibly produced and compatible with sustainable technologies.

There might still be a handful of issues left to resolve, but from where I’m sitting, it looks like the hydrogen car industry is about to explode.


How We Get To Next was a magazine that explored the future of science, technology, and culture from 2014 to 2019. This article is part of our Power Up section, which looks at the future of electricity and energy. Click the logo to read more.