Hydrogen fuel cells have a wide range of potential applications. Cars and other vehicles can run on them. They can power whole buildings and provide backup power in emergencies. Or they can run portable electronic devices.
On the largest scale, they can operate with or apart from the grid. Grid independence makes them suitable for powering data centers, hospitals, telecommunications towers, and some military applications, as well as emergency response.
It’s easy to store and transport hydrogen, although that requires low temperature or high pressure.
NASA has fueled the space program with liquid hydrogen since the 1970s. Hydrogen fuel cells power the space shuttle, for example, and produce water as a byproduct. The shuttle crew drinks the water.
Earthbound uses of hydrogen have bumped up against both technological and economic barriers.
Fuel cell development still faces challenges in cost, performance, and durability. For example, the catalyst at the anode relies on expensive platinum. Research and development seek both to make the platinum work more efficiently and to find alternative materials.
Relatively inexpensive ways to extract hydrogen are not environmentally friendly. More sustainable ways of getting it have so far proved prohibitively expensive.
Fuel cell electric vehicles require conveniently located filling stations. In principle, any existing gas station can sell hydrogen. So far, however, not many do. California has most of them.
Have we come to the verge of solving these problems?
Comprising only one proton and one electron, hydrogen is the simplest of elements. It is also the most abundant element on earth.
Unfortunately, it doesn’t exist naturally as a pure gas. We find it only in molecules with other elements.
Hydrogen can come from fossil fuels, alcohols, biomass, and water. It takes energy to extract hydrogen from any of these compounds. So hydrogen is not so much an energy source as a storage medium.
Two processes can currently break the hydrogen free from some of these compounds.
One, called reforming, subjects hydrocarbons to enough heat to break the hydrogen loose. Most of the commercial hydrogen available today comes from reforming natural gas.
The other, called electrolysis, subjects water to an electric current and divides it into its constituent hydrogen and oxygen.
Electrolysis uses more energy than steam reforming, but it can take advantage of excess renewable energy. That is, when the grid must curtail power from a wind or solar farm, the farm can use its electricity for electrolysis and make hydrogen to sell.
A new way to get hydrogen?
When I saw “extract hydrogen from oil” and “renewable energy breakthrough” in the same headline, it seemed like an oxymoron. What’s renewable about oil? As it turns out, researchers at the University of Calgary have found a way to extract hydrogen from oil without removing the oil from the ground.
That is, oil fields, currently functioning or not, can produce hydrogen instead of oil. The method applies equally to oil sands and abandoned oil fields.
The technique involves pumping oxygen into the oil field. The oxygen heats the oil, releasing hydrogen and other gases. Special filters extract the hydrogen. The process leaves everything else—notably the carbon—in the ground.
A Canadian company, Proton Technologies, is commercializing the process. Grant Strem, the CEO, estimates that the company will be able to use existing infrastructure and distribution networks to produce hydrogen for 10¢-50¢ a kilogram.
Compare that with standard production costs of about $2 per kilogram. What’s more, about 5% of the hydrogen will power the oxygen production plant.
Hydrogen fuel cells
Like a battery, a fuel cell has two electrodes, one negative (the anode) and the other positive (the cathode) surrounding an electrolyte.
A tank feeds hydrogen to the anode, where a catalyst separates the protons from the electrons.
The electrons go the cathode through an external circuit and create electricity. The protons go to the cathode through the electrolyte.
In the presence of air at the cathode, the protons unite with the electrons and oxygen to produce water and heat.
Like batteries, fuel cells produce electricity without burning anything. They emit no greenhouse gases.
Unlike batteries, they do not run down. They will operate as long as they have a constant source of fuel and air.
As a fuel for cars, hydrogen from natural gas reduces carbon dioxide by half compared to gasoline vehicles. Hydrogen from electrolysis using renewable energy reduces emissions by 90%. And nothing comes from the tailpipe except water.
In some ways, fuel cell cars resemble gasoline cars more nearly than battery cars. They can go more than 300 miles on a single tank of hydrogen.
A gallon of gasoline weighs 6.2 pounds and produces about the same amount of energy as 2.2 pounds of hydrogen. Where a car stores gasoline as a liquid, it stores hydrogen as a compressed gas at 10,000 pounds per square inch. Retail hydrogen stations can fill a tank in about five minutes. Batteries take hours to recharge.
On the other hand, a fuel cell has no moving parts, and therefore no need for motor oil. And it is more than twice as efficient as the gasoline engine. That means a fuel cell car can travel farther on a tank with better fuel economy.
Getting hydrogen from natural gas has all the same problems associated with fossil fuels in general. Electrolysis, if it uses ordinary electricity from the grid, also uses fossil fuels.
When generation of electricity relies on fossil fuels, the selling price of the electricity rises and falls with the sometimes-volatile price of the fuels. Twenty years ago it looked like fuel prices would rise forever, taking electricity prices along for the ride.
As wind and solar power have taken a larger share of available electricity generation, demand for fossil fuels has dropped. Sunlight and wind cost nothing. Costs to build, operate, and own wind and solar assets are largely fixed and predictable.
The amount of electricity renewable sources can produce fluctuates as much as commodity prices, though. Using renewable energy relies on the ability to store electricity when supply exceeds demand.
But remember, hydrogen is a storage medium.
After sunset and in windless conditions, stored hydrogen can produce electricity. All production of electricity creates waste, but the only waste from hydrogen fuel cells is water.
When solar and wind farms produce more electricity than the grid can handle, they can use some of it to turn that water back into hydrogen. The Second Law of Thermodynamics still applies, but in principle, the loop I have described should be much less expensive than electrolysis has ever been before.
Emerging hydrogen economics
A team of German and American researchers created a theoretical system of a wind farm operating an electrolyzer. They created two pricing models for it, assuming an installation in Germany and another in Texas. The model allows an investor to sell the electricity from the wind farm to the grid but use some of it to run the electrolyzer and sell the hydrogen.
As things stand now, such a system can’t compete with large-scale production of hydrogen from natural gas. But the researchers also analyzed recent trends in the price of wind energy and renewable hydrogen.
They are falling.
In another ten years, renewable hydrogen will be competitive with hydrogen synthesized from natural gas.
Don’t look for hydrogen to become the be all and end all of our energy system, but it will have a part to play in taking carbon out of it.
5 fast facts about hydrogen and fuel cells / Office of Energy Efficiency & Renewable Energy. October 4, 2017
The advent of cheap, renewable hydrogen is nigh / Megan Geuss, Ars Technica.
Fuel cells / Office of Energy Efficiency & Renewable Energy. [no date]
Hydrogen basics / Alternative Fuels Data Center. [2018?]
Hydrogen energy / Renewable Energy World
Renewable electricity to change hydrogen-supply landscape / David Wolff, Fabtech. August 20, 2019
Renewable energy breakthrough: scientists economically extract hydrogen from oil / Tom Fish, Express. August 23, 2019.
What’s the “hydrogen economy”? / Nigel Brandon, The Guardian. October 11, 2012
Hydrogen fuel uses. Public domain from Wikimedia Commons
Toyota fuel cell. Some rights reserved by Joseph Brent
Hydrogen bus. Some rights reserved by Bill Harrison
Hydrogen fuel cell diagram. Public domain from Wikimedia Commons
Electrolyzer. Public domain from Wikimedia Commons
Wind farm. © Copyright Stephen Craven and licensed for reuse under this Creative Commons Licence