By Thijs de Groot, Technology Developer at HyCC and Associate Professor at TU/e
1. We’ve only just begun
The first water electrolyzers were developed in the first half of the 20th century but were never really improved further because it soon became cheaper to make hydrogen from natural gas. In the 1970s and ‘80s there was a brief period of increased R&D on the promise of free nuclear power, but this stopped as soon as that promise faded. As a result, some of the electrolyzers made today are models which date back to the time of the Ford Model T. It is only in the last decade that we are seeing R&D in electrolysis again getting serious traction.
The same applies to electrochemistry education at universities. Five years ago, students of the Chemical Engineering faculty of the Eindhoven University of Technology (TU/e) did not even have the opportunity to take electrochemistry as a course during their bachelor’s or master’s studies. Fortunately, now Electrochemical Engineering is available as an elective course, and it is good to see that this year over 30 master’s students followed this course. At the same time, it is still possible to graduate as a chemical engineer without any electrochemical education, which shows we still have quite some work to do when it comes to educating the chemical engineers that we need to make the transition of the chemical industry successful.
2. Bigger means better
While the technology dates back to the time of the Ford Model T, the production methods of electrolyzers are possibly even more outdated: electrolyzers are still largely made by hand. Every cell is manually put on top of the previous one to form a stack. This is a typical problem of a small industry, which will be solved with growth. Electrolyzer suppliers are now rapidly constructing automated production lines, which will be a major drive for cost reduction.
And then there are the potential benefits of ‘economies of scale’. Until 1991, the largest electrolyzer in Europe was found in Glomfjord, Norway, with a capacity of 167 MW. Currently, however, the largest installation is only 10 MW. The Djewels project of HyCC and Gasunie in the Netherlands will be among the first in Europe to go beyond this, with 20 MW. Compare that with chlorine production, for which electrolysis is also used: the largest factory in Europe (that of Nobian in Rotterdam), has a production capacity of 200 MW.
In the coming years, the Djewels project will be followed by water electrolysis projects that are comparable in size to a large chlor-alkali plant. With such a tenfold increase in factory sizes, there will be significant cost reductions. However, this is not so much related to the electrolyzers, which will just be ‘numbered up’, as they account for less than 20% of the total plant costs. ‘Larger is cheaper’ applies to the other 80% of the costs. This for example includes the cooling water installation, compressors, buildings, control systems, engineering, commissioning, etc. For these items the rules of ‘economies of scale’ of the chemical industry do apply: a factory that is ten times bigger is typically only five times more expensive. This means that the hydrogen production costs of these larger plants will be significantly lower than for small plants.
But green hydrogen plants will become even bigger than that – think of several gigawatts (1 GW = 1,000 MW). So, this means that more cost reductions are feasible. This is nicely shown by the Hydrohub Gigawatt Scale Electrolyser project. Development of large-scale projects will also lead to standardization of equipment, which is another key driver for cost reduction.
3. Fundamental improvements
We can still gain a lot from scaling up, but we are not finished with the technology itself either: there is still a lot of improvement potential not only at the electrochemical cell level, but also at stack and plant levels. We are already seeing this in modern electrolyzers that can make five to ten times more hydrogen than the old electrolyzers with the same amount of surface area, and it will not stop there.
At the cell level, improved electrodes, membranes, and cell designs can help to increase performance and reduce costs. Intense research is currently taking place across the globe. For electrodes the ambition is to increase activity and long-term durability, without having to use scarce noble metals. For membranes a high conductivity is attractive to reduce ohmic resistance and, as a result, there is a tendency in research to move towards thinner membranes. However, this comes at a price of reduced mechanical strength and increased gas crossover of hydrogen and oxygen through the membrane, which limits the flexibility of the electrolyzer. In cell design, improved membrane electrode assemblies can be used to minimize ohmic resistances and enhance mass transport and bubble release. In making these improvements we need to make several trade-offs, which requires a good fundamental understanding of the processes taking place in the electrolyzer.
The performance improvements at the cell level can be used to increase the operating current density, thereby increasing the hydrogen output of the electrolyzer and consequently reducing the capital costs. Alternatively, the innovations can be used to increase the efficiency, lowering the energy consumption per kg of hydrogen produced. What strategy is most attractive will depend on the electricity price and the number of operating hours of the plant.
At the stack level, the key question is how big the stacks will become. Increasing the cell area and the number of cells in a stack is advantageous regarding stack material costs. However, large stacks can lead to challenges in flow distribution, heat management and undesired shunt currents. Here we will need to find an optimum.
Since the electrolyzer is only a relatively small part of the total plant costs, we should also look at the improvement potential in surrounding equipment. A good example is the power supply to the electrolyzer. Traditionally, thyristor-based rectifiers are used to supply direct current (DC) power large-scale electrolyzers. Recently, more advanced types of rectifiers based on insulated-gate bipolar transistors (IGBT) are being developed for multi-MW scale. These advanced rectifiers are much more suitable for flexible operation, which is a key requirement for future electrolyzers. Another interesting area of improvement lies in the gas-liquid separation of the generated gases from the electrolyte. A more efficient separation can lead to smaller and hence cheaper gas-liquid separators.
4. Technology race ongoing
We are not betting on one horse when it comes to water electrolysis technology. There is a race going on between different technologies to become the best in terms of costs, performance, and durability. Given the rapid developments in the field, it is too early to say which technology will win.
Alkaline and PEM are now the most developed, with both technologies being operational at 10+ MW scale. Yet, they have their weaknesses. For alkaline technology there are challenges in terms of compactness and flexibility, whereas PEM struggles with its dependence on iridium and perfluorinated membranes. These aspects are now being heavily researched, and solutions will be found. Yet, it is possible that new technologies such as AEM and solid oxide will outcompete alkaline and PEM within the next decade. Currently, AEM and solid oxide are only operated in small pilot and demonstration systems below 1 MW, and they still have to prove their long-term performance and ability to be scaled up in a cost-effective way.
It is also very well possible that we will not have one winner in the end, but that technologies will co-exist depending on what is most suitable for a particular location/project. For example, it could very well be that alkaline systems will be the workhorse for large-scale hydrogen plants based on solar power in desert areas, that PEM/AEM will be used for offshore systems where footprint is critical, and that solid oxide will be used for baseload operation in the chemical industry, benefitting from optimal heat integration.
5. Drive to collaborate intensifies
Windmills and solar panels have become so much more economical over the years that they can now compete with fossil electricity generation. This is not because of major fundamental breakthroughs, but because of thousands of small improvements that have added up over time. This is not always sexy and can take a long time as it involves a long supply chain of manufacturers, producers, and market parties, which all need to work together. Fortunately, there is an enormous drive among all parties to work together when it comes to hydrogen, thanks to the growing awareness of the urgent need to become more sustainable.
The time of years of isolated research in large corporate laboratories is over. At HyCC and the Eindhoven University of Technology, we are currently working together with dozens of parties, including knowledge institutes, suppliers of components such as membranes and electrodes, suppliers of electrolyzers, customers and even competitors, to make the production of green hydrogen cheaper and more reliable. One of these projects is HyScaling, in which we are collaborating with 27 other parties to create a Dutch manufacturing industry for green hydrogen.
To give an example of how we work along the value chain: we work with suppliers of nickel materials who have never supplied to the electrolysis industry to help them develop improved electrode materials. They can then supply these electrode materials to the producers of electrolyzers, which can use them to improve the output and efficiency of their electrolyzers. Specialized engineering, procurement and construction (EPC) parties will then construct plants based on these electrolyzers that will be owned and operated by HyCC. HyCC then sells the green hydrogen to its industrial customers, who make valuable products such as green methanol, green steel, and green fuels.
Thanks to these kinds of collaboration, we can improve all components of a factory, increase the scale and make production processes more efficient so that green hydrogen becomes increasingly cheaper. Most importantly, by working together, we can move fast because we have no time to waste!
About the author
Dr. Thijs de Groot is a technology developer at the Hydrogen Chemistry Company (HyCC), where he leads the innovation activities in the field of water electrolysis. He is also a part-time associate professor in the field of electrochemical engineering at the Eindhoven University of Technology. He currently focuses on improving the understanding of the ‘zero-gap’ in alkaline, AEM and chlor-alkali electrolysis. HyCC is a leading industrial partner for safe and reliable green hydrogen supplies to enable the transition to zero-carbon industry. HyCC is a joint venture of Macquarie’s Green Investment Group and the European electrochemical company Nobian which has over 100 years of experience with electrolysis.