Energy conversion to produce hydrogen

Hydrogen is not a primary source of energy, but an energy vector, which produced from energy, can store it and produce energy again by using fuel cells.

With net-zero strategies launched by several countries, including the Emirates, the production and use of low-carbon hydrogen has become an essential pillar of the energy transition. However, the realization of a low-carbon H2-based economy is still far from being mature, pending the resolution of key technical and economic challenges associated to its production, and the large costs and risks for large-scale pure H2 storage and transportation infrastructures, as well as its implementation in emerging sectors. See next figure

Figure: the value chain of hydrogen, from production to utilization.

It is becoming standard to name hydrogen by colors, depending on (1) the source of energy and (2) the molecule used as the source of it. The most standard ones are:

Grey hydrogen

  • the most produced hydrogen today, it is produced from natural gas (methane) reacting with water vapor in a process called steam methane reforming, using power from the grid. This process produces huge amounts of CO2 (between 8-10 CO2 Mtn for 1 Mtn of hydroge), emitted into the atmosphere.

Blue hydrogen

  • hydrogen is produced as the grey one, but a unit of carbon capture is added to the plant, to capture the CO2 before it is emitted into the atmosphere. This is considered low-carbon hydrogen, the intensity of the carbon also depending on the source of energy used to produced it.

Turquoise hydrogen

  • also produced from methane, but by direct pyrolysis (burning it at high temperatures), The process produces hydrogen and black carbon, with no CO2 emissions, the carbon foot print depending on the source of power to produce it.

Brown hydrogen

  • (made from brown coal) and black hydrogen (made from black coal) are produced via gasification. The generate hydrogen and CO2, emitted into the atmosphere. It is the dirtiest way of producing hydrogen, for the high CO2 emissions.

Green hydrogen

  • produced from water (or H2S) and using renewable energy, in a process called water splitting (or H2S splitting). The products are hydrogen and oxygen (or hydrogen and Sulphur). The most standard process is electrolysis, although thermochemical and photochemical processes are under investigation, and research and innovation is performed at RICH in this direction.

Pink hydrogen

  • produced from water, as the green hydrogen, but with nuclear as the source of energy.

White hydrogen or gold hydrogen,

  • is geological, naturally occurring hydrogen that can be found in underground deposits. However, that’s as far as the story goes (for now at least) as researchers and scientists have yet to identify a viable strategy to use hydrogen from these deposits.

The value chain of hydrogen includes production, transportation, storage and utilization.

Or we can develop one similar to the one below:


Hydrogen transportation and distribution

Once the hydrogen is produced, the decision on its transportation and distribution depends on the distance from the production to the point of end use, and the amount of hydrogen to be transported.

  • Hydrogen is most commonly transported and delivered as a liquid when high-volume transport and relative small amounts are needed, in the absence of pipelines. To liquefy hydrogen it must be cooled to cryogenic temperatures through a liquefaction process. Trucks transporting liquid hydrogen are referred to as liquid tankers.
  • Compressed gaseous hydrogen can be transported through pipelines similarly to natural gas. Transporting gaseous hydrogen via existing pipelines is a low-cost option for delivering large volumes of hydrogen. These pipelines are located where large hydrogen users, such as petroleum refineries and chemical plants, near the production hydrogen plant.
  • For larger distances (and to avoid high pressures and low temperatures) hydrogen can be transported by pipelines blended with natural gas. Research and testing is needed to find the highest/optimal composition of hydrogen in the mixture without affecting the integrity of the existing pipelines or the requirements to modify them for allowing higher concentrations. This is an active area of research at the RICH Center at Khalifa University.
  • For very large distances, the most viable way used today is to convert it into ammonia (NH3) by reacting with nitrogen, and delivering it in ships. Ammonia is a liquid at ambient conditions, hence it can be easily transported to long distances, with the safety conditions in place. Research is in progress to find direct uses of ammonia as a carbon less fuel, instead of splitting the ammonia back to hydrogen and nitrogen. A team of experts at the RICH center at KU are working on different applications of ammonia as a fuel in the Clean Combustion Lab.
  • Liquid organic hydrogen carriers store hydrogen in some other chemical state rather than as free hydrogen molecules. Carriers are a unique way to deliver hydrogen by hydriding a chemical compound at the site of production and then dehydriding it either at the point of delivery. This method is still in early stages of research and development and work is in progress at the RICH center at KU to find the best materials for this purpose.
  • To optimize the production and uses of clean hydrogen, the Paris mission innovation on clean hydrogen is promoting the creation of hydrogen valleys, where the final users and producers share the same geographical location, avoiding long distance transportation. Faculty from KU are participating as technical experts in this Mission Innovation.