04/13/2021 | Spotlight
The ongoing discussions seems to suggest that hydrogen, especially “green” hydrogen, is the solution to all the challenges we currently face with respect to our future energy supply.
Hydrogen, as an energy carrier, can be nearly universally applied to supply energy to all sectors. Furthermore, it can be used as a raw material and reduction agent in the energy-intensive process industries, thereby substituting emission-intensive fossil alternatives.
Germany’s national hydrogen strategy paints hydrogen in bright colors depending on how it is produced. “Grey” hydrogen is produced by steam reforming of natural gas, by far the most common process to date. “Grey” changes to “blue” if the resulting emissions are captured and stored (CCS), an option currently not exploited in Germany. “Green” hydrogen is produced by water electrolysis using only electricity generated by renewable sources. “Turquoise” hydrogen is produced by pyrolysis of natural gas into hydrogen and carbon.
For stakeholders from the power sector, hydrogen holds the promise of storing electricity from fluctuating and intermittent renewable sources via water electrolysis and regenerating the electricity from hydrogen in times of low renewable supply.
Within the transport sector, fuel cell technology can make light and heavy road vehicles, even boats, essentially emission-free. Chemical transformation of hydrogen also allows for the production of alternative fuels that may act as substitutes for current fossil fuels. This might be a future path for the refinery sector.
Hydrogen can be, within some limitations, introduced into current natural gas transport structures and thereby supply a fuel for district heating to households and commercial applications.
The process industries on the other hand face a multitude of challenges on their path to reach greenhouse gas neutrality in the future; some of them might be addressed by hydrogen.
Iron, for instance, is currently produced by blast furnaces with coke as a reducing agent; up to now, there are no alternatives to hydrogen for achieving greenhouse-gas-neutral production via direct reduction.
High-temperature processes, as are used in ceramics and glass production, require fuels that supply heat but also generate desired process conditions, i.e. a certain atmosphere. These characteristics cannot be supplied by electricity alone because they require molecular (synthetic) fuels.
The chemical industry has a long history of using hydrogen in its processes, such as the production of ammonia and methanol, but also generates it as a by-product, e.g. in the chlorine alkaline process.
One option is the production of synthetic naphtha from CO2 and hydrogen. If this admittedly very energy-intensive option is chosen, the German chemical industry, with a current demand of around one million tons a year, is looking at a potential future demand for hydrogen in the order of up to 7 million tons, depending on which scenario is considered.
Electrolytic processes are at the heart of this development. The latest headlines indicate that the industry is rising to the challenge: In January, Linde announced the construction of the world’s largest PEM-based electrolyser plant in Leuna, Germany, (PEM stands for “proton exchange mem brane”) with a capacity of 24 MW. A week later, Air Liquide started operating a 20 MW PEM electrolyser in Canada, using hydro power. At about the same time, a project consortium of 15 partners presented its plans to build a 100 MW alkaline electrolyser plant at an industrial site run by Repsol.
A major challenge still lies in the scale-up of electrolysis technologies. As complex multiphase transportation processes are involved, simply doubling or quadrupling the surface area of an electrode doesn’t do the trick. The most popular approach urrently is stacking the electrolyser cells. Siemens Energy is optimistic. With 100 MW plants currently under development, the company is investigating 1 GW tech nologies in cooperation with he chemical industry. This could be one contribution to decreasing the cost of elec trolysis. Although the cost has already top pled due to falling prices of renewable energy, the International Renewable Energy Agency (IRENA) identified in a report pub lished in December 2020 several areas that need to be addressed to make “green” hydrogen competitive. Economies of scale play a major role, both regarding the size of electrolyser plants and the automated serial stack production in “gigawatt scale manufacturing facilities”. This should go hand in hand with electrolysis systems that are optimised for specific applications in different industries. Based on learning rates in the solar photovoltaics industry, IRENA expects cost declines of 16–21%.
So far, the different electrolysis technologies are still running a fierce race for volume and competitive prices. According to a review published in fall, energy demands for alkaline electrolysis (AEL), proton exchance membrane (PEM) electrolysis and solid oxide electrodes (SOEC) electrolysis are similar. Decisive for the selection of the right process were external site de pendent factors such as required flexibility depending on energy sources, which can be met better by AEL and PEM. Under steady state conditions, however, SOEC could be a feasible alternative. These re sults indicate that a specification of the electrolysis process to applications might indeed be a feasible pathway. Electrode materials are also closely under investiga tion. To avoid the cost of precious metals, companies like NEL Hydrogen employ nickel as the basis for their electrodes.
Security of (continuous) supply is a major issue to be resolved in order to use hydrogen in the process industries and requires infrastructure investment. In the case of a defossilised chemical industry, what requirements must future energy infra structures meet by 2050? The highly indus trialised Antwerp-Rotterdam-Rhine-Ruhr Area (ARRRA) in the triangle between Germany, Belgium and the Netherlands is today very well developed and includes three major chemical sites. But what are the future demands on the existing and especially the cross-border energy infra structures? This question is at the heart of a study that was jointly undertaken with institutions from Belgium, the Netherlands and Germany.The conclusion in a nutshell: The transformation to the hydrogen econo my has to take into account systemic parameters; many industrial sites are closely interlinked and rely on a common infra structure. A systemic approach is highly recommended.
With the generation of large volumes of hydrogen, the next question that arises is how to transport and convert it into fuels or chemicals. As are other countries, Germany is currently investigating concepts of processing hydrogen at the site of its generation. This goes so far as to include autonomous plants located in offshore windparks. In the initiative “Wasserstoff Republik Deutschland”, driven by the Federal Ministry of Education and Research, three main projects have been commissioned:
H₂Giga joins all major technology owners of electrolytic technologies in order to promote production technology of electrolysers towards mass production on GW scale. H2Mare will develop PtX-technologies in offshore conditions to open up a new field for renewable energy use and the production of fuels and chemicals. The TransHyDe project investigates the inter action of energy carrier demand and infrastructures on a European level for all relevant process industries.
Florian Ausfelder is head of energy and climate at DECHEMA e.V. With his team, he collaborates with industry and academia partners to promote sustainable use of energy and mitigation of greenhouse gases within the energy-intensive industry in Germany and Europe.
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