Hydrogen Fuel; Green Fuel of the future, types and production processes.

Hydrogen Fuel, types of hydrogen classified by production method, uses and what makes hydrogen the best fuel of the future; hydrogen manufacturing industries, hydrogen storage, drawbacks and the future of green hydrogen.

hydrogen fuel molecule

Hydrogen the most abundant element in the universe finds extensive applications including energy generation as fuel in conventional combustion with oxygen as well as in a fuel cell technology for electrical energy generation. When clean energy advocates think what can be found which would be as easy to use as fossil fuels that when burn will produce only water without carbon emission, they think about hydrogen.

Hydrogen fuel is a zero-carbon fuel burned with oxygen; provided that it is created in a process that does not involve carbon. It can be used in fuel cells or internal combustion engines. Regarding hydrogen vehicles, hydrogen has begun to be used in commercial fuel cell vehicles such as passenger cars, and has been used in fuel cell buses for many years. It is also used as a fuel for spacecraft propulsion.

As Beautiful as hydrogen appears, turning the most common element in the universe into the new fuel of choice is harder than it might seem. First thing to know about hydrogen is that not all hydrogen is created equal; bringing forth the hydrogen rainbow which describes the types of hydrogen with methods through which the hydrogen fuel is generated which is covered in the production process below.

Production of Hydrogen fuel

Hydrogen energy production station

Hydrogen fuel is most commonly produced from methane or by electrolysis of water. As of 2020, the majority of hydrogen (≈95%) is produced from fossil fuels by steam reforming or partial oxidation of methane and coal gasification with only a small quantity by other routes such as biomass gasification or electrolysis of water.

Steam-methane reforming the current leading technology for producing hydrogen in large quantities, extracts hydrogen from methane. However, this reaction releases fossil carbon dioxide and carbon monoxide into the atmosphere, which are greenhouse gases exogenous to the natural carbon cycle, and thus contribute to climate change.

In electrolysis, electricity is run through water to separate the hydrogen and oxygen. This method can use wind, solar, geothermal, hydro, fossil fuels, biomass, nuclear, and many other energy sources. Obtaining hydrogen from this process is being studied as a viable way to produce domestically at a low cost.

Because pure hydrogen does not occur naturally on Earth in large quantities, it usually requires a primary energy input to be produced on an industrial scale. Hydrogen is unique because it can be generated in many different ways. The different ways in which it is created actually is defined and classed by colors termed the hydrogen rainbow; Green, Brown/Black, Pink, turquoise, Blue and Grey Hydrogen which scales from the most environmentally friendly to the least.

Hydrogen is produced through a number of processes that each yield different types of energy, which come with their own sets of benefits, byproducts and uses. The production method is what gives each kind of hydrogen its colorful moniker, though there is no universal naming convention, so definitions can change over time and vary between countries.

Let’s break down the current hydrogen color code and take a look at how one hue of hydrogen, in particular is leading scientists and manufacturers to the pot of gold “a zero-emission future” at the end of the hydrogen rainbow.

Grey hydrogen

Grey hydrogen is created from natural gas, most commonly methane, through a process called steam methane reformation. While it is currently the most common form of hydrogen production, the greenhouse gases made in the process aren’t captured.

Blue hydrogen

Blue hydrogen relies on the conventional process of steam methane reforming, but the carbon dioxide produced as a byproduct is captured and sequestered underground.  It is a source of clean hydrogen with low carbon content.

Turquoise hydrogen

One of the newer colors to join the hydrogen spectrum, turquoise hydrogen is produced via a process called methane pyrolysis. Its primary outputs are hydrogen and solid carbon. While turquoise hydrogen has no proven impact at scale yet, it has potential as a low-emission solution if scientists can find ways to power the thermal process with renewable energy and properly use or store the carbon byproduct.

Pink hydrogen

Pink hydrogen taps into nuclear energy to fuel the electrolysis required to produce it. The high temperatures of the nuclear reactors provide an additional benefit — the extreme heat produces steam that can be used for electrolysis or fossil gas-based steam methane reforming in other forms of hydrogen production.

Brown/black hydrogen

If green and blue hydrogen hold the key to cleaner hydrogen production, brown or black hydrogen are the exact opposite and the most environmentally damaging. Relying on gasification of coal to produce hydrogen, this process releases harmful carbon emissions that can have a long-lasting impact on our climate.

Green hydrogen

Amidst the hydrogen rainbow, green hydrogen is the only variety produced with zero harmful greenhouse gas emissions. It is created using renewable energy sources like solar, wind and hydropower to electrolyze water. The resulting reaction produces only hydrogen and oxygen, meaning zero carbon dioxide is emitted in the process.

While the benefits of green hydrogen are significant, its production is more expensive today. Consequently, green hydrogen makes up just a small percentage of current hydrogen production. But as new advances and innovations in green hydrogen are made, the price will come down, and it will hopefully become common across the globe.

Hydrogen fuel production industries

The world’s largest facility for producing hydrogen fuel is claimed to be the Fukushima Hydrogen Energy Research Field (FH2R), a 10 MW-class hydrogen production unit, inaugurated on 7 March 2020, in Namie, Fukushima Prefecture. The site occupies 180,000 m2 of land, much of which is occupied by a solar array; power from the grid is also used for electrolysis of water to produce hydrogen fuel.

Other Hydrogen fuel production companies include; H2Pro a renewable energy company that is working on an efficient green hydrogen production method called E-TAC, a water-splitting technology that uses electricity to split water into hydrogen and oxygen separately in different phases.

C-Zero is a hard-tech startup located in Santa Barbara, CA, that is developing a technology for decarbonizing natural gas. The company’s technology uses high temperatures to break down methane, (the primary molecule in natural gas) into hydrogen and solid carbon. C-Zero’s hydrogen can be used to decarbonize a wide range of industries including ammonia production, electric generation, process heat, and fuel cell vehicles, and has the potential to address 75% of global CO2 emissions.

Hydrogen Energy overview

Liquid Hydrogen

Hydrogen is found in the first group and the first period in the periodic table, i.e., it is the lightest element. Hydrogen is rarely found in its pure form in the atmosphere, H2 in flame of pure hydrogen burns in air, the hydrogen (H2) reacts with oxygen (O2) to form water (H2O) with the release of energy.

2H2 (g) + O2 (g) → 2H2O (g) + energy

In atmospheric air rather than pure oxygen, hydrogen combustion may yield a small amount of nitrogen oxides with the water vapor. The energy released allows hydrogen to be used as a fuel.

In an electrochemical cell, that energy can be used with relatively high efficiency. If the energy is used to produce heat, thermodynamics places limits on the thermal efficiency of the process.

Hydrogen is usually considered to be an energy carrier, like electricity, as it must be produced from a primary energy source such as solar energy, biomass, electrical energy, or hydrocarbons such as natural gas or coal. Conventional hydrogen production using natural gas induces significant environmental impacts; as with the use of any hydrocarbon, carbon dioxide is emitted. At the same time, the addition of 20% hydrogen (an optimal share that does not affect gas pipes and appliances) to natural gas can reduce CO2 emissions from heating and cooking. Hydrogen is locked up in enormous quantities in water, hydrocarbons, and other organic matter.

One of the challenges of using hydrogen as a fuel comes from being able to extract hydrogen efficiently from these compounds. Currently, steam reforming, which combines high-temperature steam with natural gas, accounts for the majority of the hydrogen produced. This method of hydrogen production occurs at 700–1100 °C, and has an efficiency of 60–75%.

Hydrogen can also be produced from water through electrolysis, which is less carbon-intensive if the electricity used to drive the reaction does not come from fossil-fuel power plants but rather from renewable or nuclear energy sources. The efficiency of water electrolysis is about 70–80%, with a goal of 82–86% efficiency by 2030 using proton exchange membrane (PEM) electrolyzers.

Once produced, hydrogen can be used in much the same way as natural gas – it can be delivered to fuel cells to generate electricity and heat, used in a combined cycle gas turbine to produce larger quantities of centrally produced electricity or burned to run a combustion engine; all methods producing no carbon or methane emissions. In each case hydrogen is combined with oxygen to form water. This is also one of its most important advantages as hydrogen fuel is environmentally friendly.

The heat in a hydrogen flame is a radiant emission from the newly formed water molecules. The water molecules are in an excited state on the initial formation and then transition to a ground state; the transition releasing thermal radiation. When burning in air, the temperature is roughly 2000 °C (the same as natural gas).

Historically, carbon compounds have been the most practical carriers of energy, as hydrogen and carbon combined are more volumetrically dense, although hydrogen itself has three times the specific energy (energy per unit mass) as methane or gasoline. Although hydrogen is the lightest element and thus has a slightly higher propensity to leak from older natural gas pipes such as those made from iron, leakage from plastic (polyethylene PE100) pipes is expected to be very low at about 0.001%.

The reason that steam–methane reforming has traditionally been favored over electrolysis is that whereas methane reforming directly uses natural gas as a source of energy, electrolysis requires electrical energy for this. When the cost of producing electrical energy (via wind turbines and solar PV) falls below the cost of natural gas, electrolysis will become cheaper than SMR.

Uses of Hydrogen Fuel

Hydrogen fuel can provide motive power for liquid-propellant rockets, cars, trucks, trains, boats and airplanes, portable fuel cell applications or stationary fuel cell applications, which can power an electric motor. Hydrogen is considered as the primary sustainable source of renewable energy and is “highly required for advanced energy conversion systems.”

Hydrogen fuel can also be used to power stationary power generation plants, or to provide an alternative to natural gas for heating.

Hydrogen use in Fuel cells

Fuel cells present the most attractive choice for energy conversion from hydrogen to electrical power, due to their high efficiency, low noise, and a limited number of moving parts. Fuel cells are of interest for both stationary and mobile power generation from hydrogen. Fuel cells are often considered as part of a vehicle propulsion system.

Fuel cell technology diagram

Using a fuel cell to power an electrified powertrain including a battery and an electric motor is two to three times more efficient than using a combustion engine, although some of this benefit is related to the electrified powertrain (i.e., including regenerative braking). This means that significantly greater fuel economy is available using hydrogen in a fuel cell, compared to that of a hydrogen combustion engine.

Hydrogen Fuel Cell Electric Vehicle Layout diagram for Toyota Mirai

Internal combustion engine conversions to hydrogen

Alongside mono-fuel hydrogen combustion, combustion engines in commercial vehicles have the potential to be converted to run on a hydrogen–diesel mix. This has been demonstrated in prototypes in the UK, where their CO2 emissions have been reduced by up to 40% during normal driving conditions. This dual-fuel flexibility eliminates range anxiety as the vehicles can alternatively fill up only on diesel when no hydrogen refueling is available.

Relatively minor modifications are needed to the engines, as well as the addition of hydrogen tanks at a compression of 350 bars. Trials are also underway to test the efficiency of the 100% conversion of a Volvo FH16 heavy-duty truck to use only hydrogen. The range is expected to be 300 km/17 kg; which means efficiency better than a standard diesel engine (where the embodied energy of 1 gallon of gasoline is equal to 1 kilogram of hydrogen).

Hydrogen is a diatomic molecule, two hydrogen atoms sharing a valence shell. You can fill a balloon with hydrogen and oxygen gases and they will not instantly form water. To get water out of this you need to ‘excite’ the sets of hydrogen and oxygen atoms sufficiently to ‘unstick’ them. Of course, using hydrogen in a combustion chamber mixed with air is pretty straightforward (remember it’s a 2 to 1 mix of hydrogen and oxygen – and air contains roughly 21% oxygen).

However, there is a problem with hydrogen as a fuel source for an internal combustion engine. While it has incredible energy density per pound – about three times that of gasoline, it is, unfortunately, the lightest element in the universe, meaning that it has to be squeezed mightily to get any density at all. Even compressed hydrogen doesn’t come close to the energy density of gasoline by volume. So, given the low efficiency of an internal combustion engine compared to an electric motor, hydrogen isn’t an effective solution for ICE.

Liquid Hydrogen for Rocket Propulsion

Liquid Hydrogen is a fuel used in rockets and various spaceships it is light and extremely powerful rocket propellant, has lowest molecular weight and burns with an oxidizer such as liquid oxygen, liquid hydrogen yields the highest specific impulse. Liquid hydrogen has been used as a fuel in space technology for several years as seen on the retired NASA’s Space Launch System and the new Space Launch System SLS and others.

Hydrogen Storage

Hydrogen storage is technique used for any of several methods for storing hydrogen for later use. The problems of using hydrogen fuel in cars arise from hydrogen being difficult to store in either a high pressure tank or a cryogenic tank. These methods encompass mechanical approaches such as high pressures and low temperatures, or chemical compounds that release H₂ upon demand. While large amounts of hydrogen are produced, it is mostly consumed at the site of production, notably for the synthesis of ammonia.

hydrogen storage tank

For many years hydrogen has been stored as compressed gas or cryogenic liquid, and transported as such in cylinders, tubes, and cryogenic tanks for use in industry or as propellant in space programs. Interest in using hydrogen for on-board storage of energy in zero-emissions vehicles is motivating the development of new methods of storage, more adapted to this new application.

Hydrogen cryogenic storage tank technology

The overarching challenge is the very low boiling point of H₂: it boils around 20.268 K (−252.882 °C or −423.188 °F). Achieving such low temperatures requires significant energy.

Cross section of Hydrogen storage tank

Established technologies for Hydrogen storage over time include;

• Compressed hydrogen
• Liquefied hydrogen
• Chemical storage

Drawbacks of Hydrogen fuel

Hydrogen has a high energy content per unit mass. However, at room temperature and atmospheric pressure, it has a very low energy content per unit volume compared to liquid fuels or even to natural gas. For this reason, it is usually either compressed or liquefied by lowering its temperature to under 33 K. High-pressure tanks weigh much more than the hydrogen they can hold. For example in the 2014 Toyota Mirai, a full tank contains only 5.7% by weight of hydrogen, the rest of its mass being that of the tank.

Hydrogen fuel is hazardous because of the low ignition energy and high combustion energy of hydrogen, and because it tends to leak easily from tanks. Explosions at hydrogen filling stations have been reported. Hydrogen fuelling stations, like petrol, generally receive deliveries of hydrogen by truck from hydrogen suppliers. An interruption at a supply facility can shut down multiple fuelling stations.

The future of hydrogen is green

Hydrogen has been used as fuel for more than two centuries. Today, thousands of vehicles and machines around the world are powered by hydrogen fuel cells. The emphasis on reducing carbon emissions and working towards a greener, sustainable future has shifted the focus of many power leaders, including Cummins, to investment and innovation in green hydrogen production. It could prove to be the gold at the end of the hydrogen rainbow.