The changes we’re seeing happening all around us have many of us thinking about what alternatives exist to the ubiquitously used hydrocarbon fuels, such as fuel oil, gasoline and diesel. Hydrogen certainly looks like a viable alternative, though there’s more than meets the eye, and its success as an alternative fuel depends in large part on how it is created, as it can be a resource-intensive process.
Hydrogen is the most abundant atom in the universe, however, discovering it and developing applications for it, took some time. Chemist Robert Boyle first observed and described a reaction between iron filings and dilute acids, which resulted in the production of hydrogen gas, in 1671. It wouldn’t be till 1766, that scientist Henry Cavendish first recognized hydrogen gas as a discrete substance.
Hydrogen was first used in large scale applications as fuel in hydrogen-filled balloons and airships. In fact, hydrogen fueled the first transatlantic crossing made by the British airship R34 in 1919, but much has changed since then in the creation and uses of hydrogen. We are also able to make it safer now.
In simplest terms, hydrogen is made when you split water into hydrogen and oxygen.
At this time, the biggest hurdle to hydrogen becoming more widely used is the cost of producing it. It might be relatively simple to make, but if it takes many additional resources or causes extra waste, when other hydrocarbons are readily available, it becomes less attractive as an alternative fuel source.
The following is a brief rundown of all the ways hydrogen can be produced:
- Natural gas reformation/gasification; a mixture of hydrogen, carbon monoxide and a small amount of carbon dioxide is created by reacting natural gas with high-temperature steam. Synthesis gas can also be created by reacting coal or biomass with high-temperature steam and oxygen.
- Electrolysis; an electric current splits water into hydrogen and oxygen. If using renewable power sources, the resulting hydrogen will be considered renewable – green – as well.
- Renewable liquid reforming; using renewable liquid fuels, such as ethanol, and reacting them with high temperature steam to produce hydrogen.
- Fermentation; converting biomass into sugar-rich feedstock which when fermented produces hydrogen.
And a few production methods that are in development and not yet available for mass production:
- High-temperature water splitting; high temperatures generated by either nuclear reactors or solar concentrators drive chemical reactions that can split water to produce hydrogen.
- Photobiological water splitting; using microbes, such as green algae to consume water while in sunlight, produce hydrogen as a byproduct.
- Photochemical water splitting; producing hydrogen from water using semiconductors and energy from sunlight.
As you can see, there are many ways to make hydrogen, but not all are considered green. And some of the green production methods require upfront capital to get started. The important thing to remember though, is that hydrogen is a growth industry that is attracting innovation, many bright minds and investment capital. We’re seeing those innovations applied in different industries, such as aviation and large truck transport, indicating that hydrogen is gaining traction as an alternative fuel.
Storing and dispensing at high pressure
Hydrogen is a very light gas, low on the molecular scale, and very compressible. When compressed it can contain more energy, this is why it is stored under high pressure to keep the gas compressed. Compressed hydrogen in hydrogen tanks is stored at 350 bar (5,076 psi) and 700 bar (10,153 psi), which is used for hydrogen tank systems in vehicles. If you didn’t compress the hydrogen, it would take a full commercial storage tank to get enough energy to power one car, which is not cost-effective at all, nor would it fit in the car. Until we’d learned to compress hydrogen, it was not considered beyond filling a balloon for transit purposes.
Compression also means it can be transported more easily, either in tanker trucks, or added to a natural gas pipeline and stripped back out at the destination point. In most cases it should be stored close to the dispensing point to limit transit expenses, similar to the way gas stations store fuel in underground tanks, hydrogen is stored in above ground tanks.
Dispensing a high-pressure material is ideally done with flow meters and dispensers that meet the B31.3 high pressure code standard for safety. The latest flow meters to come on the market offer an added safety feature in the form of a rupture disk which is a first line of defense in case of failure to safely dispense. The system, with built-in diagnostics, will stop all flow the instant the rupture in the rupture disk is detected. This is a valuable safeguard to help protect assets and personnel.
Applications for hydrogen
Today, we’re seeing hydrogen used with limited application in the U.S., and then only primarily in California which is a front runner in exploring alternatives to gasoline or diesel combustion engine fuels for transportation. It should be noted that in recent news articles, semi-truck companies such as General Motors and Hyundai, among others, are investing in the infrastructure needed to develop a hydrogen powered transportation network in the near future. Europe has a bigger market for hydrogen where it is used as a fuel source for trucks, buses and even some cars. Though the percentage of adoption is still relatively low when compared with traditional combustion engines or the exponential growth seen in electric vehicle adoption, but it is growing as the call for green fuels is increasing.
To clarify, there are hydrogen combustion engines that work on a similar principal to gasoline or diesel combustion engines, and there are hydrogen fuel cell engines that uses an electrochemical reaction of hydrogen instead of combustion.
One innovation that is particularly exciting is the development of airplanes that can fly on hydrogen fuel. Several companies, including Boeing and Airbus, are working on this, for both large and small craft, and recently test flights have begun to see how well hydrogen fuel performs in flight. And of course, NASA has used hydrogen gas for decades to fuel the rockets for space travel, but that is a different application.
Back to the future
As we look to the future of hydrogen it’s worth noting those early pioneers who were convinced hydrogen filled balloons, also known as gasbags, were the future of aviation and goods transport by lighter than air means, were on to something, they just didn’t have the full picture yet of what hydrogen could do. A little over a hundred years ago, simple sewn, and special glue and aluminum powder coated massive balloons, filled with hydrogen, floated across landmasses and oceans; guided by a rudder and small propeller. Today, the technology that produces hydrogen and is able to compress it to gain more usable energy from it, has advanced significantly to the point where we can again take to the skies with hydrogen as a fuel source, safer and with more power.
Right now, hydrogen is poised to take on a larger role in our search for alternative fuels and more efficient machines that move people and goods around the globe, without adding more carbon dioxide to the atmosphere. The innovations in production and application will bear watching in the coming decade.
Tim Drost is a senior global product manager at Emerson and focuses on Coriolis sensors in the alternative fuels, life sciences, and food and beverage industries. He has been at Emerson for over 15 years and has held responsibilities in inside sales, outside sales and product marketing. He holds a BS in mechanical engineering and an MBA from the University of Colorado.