Author: Fanny Pohontsch

Global spotlight on PtX technologies from Dresden

November 07, 2023

Fraunhofer IKTS transfers innovative high-temperature systems for climate protection to industry worldwide

In the Paris Agreement on climate protection, the global community for the first time made a binding commitment under international law to ambitious climate protection targets. The countries involved want to work together to drive forward the global energy transition. This requires breakthrough technologies such as those that have been the focus of developments at Fraunhofer IKTS since the institute was founded in 1992. In particular, high-temperature electrolysis-based system chains, which, for example, produce hydrogen, synthetic fuels and fertilizers particularly efficiently from green electricity, air and water, are now about to make an evolutionary leap from the laboratory to international practical use.

PtX explained

All technologies that store electrical energy as a material are referred to as Power-to-X, abbreviated as PtX. Here, X stands for the variety of products.

In a narrower sense, PtX primarily refers to those technologies that use solar or wind power, for example,

to generate the energy carrier hydrogen without fossil feedstocks and without harmful exhaust gases and use it to synthesize other products. This hydrogen can then be used, for example, for the synthesis of fuels, for fertilizer production or for reverse power generation, i.e. as an energy buffer, so to speak.

A sub-variant of PtX is power-to-liquid (PtL). In this process, synthetic diesel or another liquid energy carrier or basic chemicals are produced using electricity, for examplen.

“These technologies and systems are now so mature that, together with our industrial partners, we can take the step from pilot projects toward large-scale plants and large-scale production,” says Dr. Matthias Jahn, who heads the Department of Energy and Process Engineering at Fraunhofer IKTS. “We link our high-temperature electrolysis with other process steps to form complex chains that can provide synthetic aviation fuels and other urgently needed substances from water vapor and carbon dioxide without any fossil feedstock at all. Using water and atmospheric nitrogen, ammonia can also be produced as a further energy source,” adds Dr. Mihails Kusnezoff, head of the Materials and Components Department.

This is possible by combining efficient hydrogen production with established synthesis methods such as Fischer-Tropsch and Haber-Bosch synthesis. Fraunhofer IKTS can contribute many years of experience with ceramic high-temperature electrolysis cells, which are particularly suitable for efficient hydrogen and synthesis gas production. The resulting new value chains have not only an ecological but also an economic dimension: “We can see quite clearly that markets for high-temperature electrolysis and PtX plants are now emerging worldwide,” report the department heads.

Japan: Eco-ammonia for shipping – GreatSOC

One example is the Saxon-Japanese project GreatSOC, which aims to synthesize “green” ammonia as an energy carrier for ship propulsion and sea transport. To this end, Fraunhofer IKTS has joined forces with the National Institute of Advanced Industrial Science and Technology (AIST), Kyoto University, and industrial partners EDL Anlagenbau GmbH from Leipzig and Japan's Morimura SOFC Technology. Instead of providing the hydrogen for ammonia production from natural gas as in conventional processes, GreatSOC relies on high-temperature electrolyzers with increased efficiency. This eliminates the carbon dioxide emissions that would otherwise be produced. The new process chain also eliminates the need for an expensive liquefier to extract the second component – nitrogen – directly from ambient air.

In this project, IKTS is contributing the expertise it has built up over decades in linking highly efficient high-temperature systems to complex processes. “We have suitable high-temperature electrolyzers in the laboratory, which generate the synthesis gas (H₂ and N₂) required for ammonia synthesis in a multi-stage concept without the use of air separation,” reports Dr. Mihails Kusnezoff. The researchers simulate further process steps on the computer. In this way, the GreatSOC partners can adjust material flows and process engineering concepts until an optimum is found between high efficiencies, costs and environmental balance. In addition to the target product ammonia, the only waste product in this new German-Japanese plant chain is water. This can then be fed right back into the process cycle. In this case, the ammonia itself is not used as a raw material for fertilizer, but as fuel on the high seas.

At a glance – ammonia in shipping

Ammonia has a high hydrogen density. It can be used to store about 1.5 times the amount of energy by volume compared with liquid hydrogen. This is important for storing sufficient energy on board a ship, especially for long distances.
Compared to pure hydrogen, the temperatures and pressures required for liquefaction and thus storage are more moderate for ammonia, so the requirements for containers and the energy required for compression are lower. This facilitates handling of the hydrogen carrier both on land and at sea.

Ammonia can be used not only as a fuel for engines, but also for emission-free power generation in fuel cells. This allows flexibility in integration into different types of ships and applications.
Unlike fossil fuels, the combustion of ammonia does not produce carbon-based emissions such as carbon dioxide. Emissions are limited to nitrogen oxides (NOx) and water, and NOx emissions in particular can be reduced by using available DENOX technologies. Potential NH₃ slip has also already been prevented in other propulsion systems, so these challenges are considered solvable

Brazil: sustainable fuel for aviation

The Fraunhofer experts in Dresden have launched another project together with partners in South America: the Brazilians are looking for ways to break away from fossil dependencies and synthesize aviation fuels in an environmentally friendly way. At a workshop in Dresden, they came across IKTS and asked for a practicable solution. Again, the Fraunhofer researchers are initially building a lab-scale co-electrolysis chain designed for on-site experiments in Brazil. The goal is to build an entire chain in the region that at first generates synthesis gas from green electricity, water and CO₂ and ultimately refines it into e-kerosene for South American air traffic. “In this respect, our joint project is helping to build sustainable know-how in Brazil,” emphasizes Matthias Jahn.

EU, South Africa and Australia

And further projects are already underway. These include the EU joint project Advanced Materials and Reactors for ENergy storage tHrough Ammonia (ARENHA), which is advancing the use of synthetic ammonia as an energy carrier. Meanwhile, in the industry consortium Catalyst Research for Sustainable Kerosene (Care-o-Sene), IKTS is supporting the development of next-generation Fischer-Tropsch catalysts together with partners from Germany and South Africa. In the future, they will be used to synthesize the feedstock for sustainable aviation fuels on a large scale in order to gradually replace fossil kerosene. Similar projects are also underway with partners from Australia.

From the laboratory to industrial scale

“In addition to research institutes, more and more international industrial companies are working on such collaborative projects for high-temperature electrolyzers and are interested in coupling them with modern synthesis reactors,” Jahn and Kusnezoff emphasize. Both scientists see this as a clear indication that mass markets are developing worldwide in this field. This opens up completely new business areas and market opportunities, not least for German SMEs with their plant engineering expertise.

It is true that larger electrolyzers based on the older functional principles of alkaline and PEM electrolysis are already available on the world markets. But the far more efficient high-temperature electrolyzers have so far only been available for low output classes and in small quantities. However, high-temperature electrolyzers in the megawatt class will be needed in the next few years if Germany, the EU and other countries and associations of countries are to achieve their ambitious goals for environmental protection and the development of a potent hydrogen economy.

Toolbox instead of black box

It is anything but trivial to link the new systems into complex synthesis chains. One challenge is to predict the functionality and parameters of such chains already in the development stage in order to avoid expensive bad investments. Fraunhofer IKTS has accumulated special expertise for this purpose. This extends to the automation of the entire process as well as the electrolyzer production. The key factor is that the scientists in Dresden have a technological command of the entire value chain, from the material to the highly automated process. Therefore, they are able to develop highly efficient solutions for and with industry like hardly any other player. This is why Fraunhofer IKTS is repeatedly in demand as a partner in the development of modern and sustainable high-temperature processes.

Billion euro market expected

Not only the Fraunhofer experts are convinced that high-temperature hydrogen technology and synthesis chains linked to it will play a growing role in the coming decades. The British market research company IDTechEx, for example, expects the market for high-temperature fuel cells to grow to a volume of 6.8 billion dollars over the next ten years. They also forecast high growth rates for ceramic electrolyzers.

Advantages of high-temperature technology*

Higher efficiency: synthesis chains based on PEM electrolyzers need about 9.5 kilowatt hours (kWh) to synthesize one kilogram of ammonia. High-temperature chains require only 8 kWh per kilogram of ammonia – about 15 percent less energy input.
No carbon dioxide emissions
Residual products water and waste heat can be fed back into the process cycle
No precious metals required

Disadvantages of high-temperature technology*

Higher process complexity due to high operating temperatures in the 800 °C range.
The high-temperature systems currently cost more to manufacture than PEM and AEM solutions. However, these additional costs will be significantly reduced in the next few years when highly automated mass production is up and running.

(* compared to low-temperature plants or natural gas-based solutions)

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