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Home » Technologies & Materials » Firing » Green Hydrogen – Thermal Process Solutions for the Fuel Cell Industry

Green Hydrogen – Thermal Process Solutions for the Fuel Cell Industry

The fuel cell is seen as the efficiency technology of the future, yet the idea behind it is more than 180 years old. Hydrogen and oxygen generate electricity and heat. The fuel cell converts the energy contained in the water molecules into electricity which can then be used as a drive fuel for transportation or other applications. With the advent of “green hydrogen”, the fuel cell appears to be one of the best environment- friendly propulsion technologies for trains and other means of heavy-duty transport. This article also focuses on the fact that climate goals can only be achieved through the coexistence of hydrogen and battery mobility. In addition to thermal processing and cell recycling plants for the global Lithium-Ion Battery (LIB) industry, Riedhammer also provides fuel cell manufacturing technology, specifically designed to match customer requirements.

At present, there are many indications that electrification will be the drive technology of the future. However, in numerous applications fuel cells are seen as a sound alternative for decarbonised mobility due to several promising features: they are renewable, environmentally friendly, highly efficient, provide long operating times, excellent reliability and have a long lifespan. Fuel cell operating principle The way a fuel cell works is relatively simple (Fig. 1). It has, in fact, many similarities with a battery (i.e. energy is generated by a chemical reaction). A fuel cell consists of two electrodes – an anode and a cathode – and an electrolyte (for example oxide ceramic/zirconium oxide) which is impermeable to gases and separates the electrodes from each other. Hydrogen is fed to the anode, which is split by a catalyst into posttive ions and negative electrons. The electrons migrate via an electrical conductor to the cathode, creating a current. At the same time, the positively charged hydrogen ions pass through the electrolyte to the cathode, where they ultimately react with oxygen to form water. This process, also called cold combustion, brings some advantages but also involves technical challenges. The fuel cell thus converts the chemical energy of a fuel into electrical energy. This conversion takes place in the so-called fuel cell stack (Fig. 2), which usually consists of a large number of individual cells. Advantages of fuel cells and prospects Current forecasts indicate that, from 2030 onwards, new technologies will increasingly be used alongside batteries. From 2040, approximately 57 million of 128 million vehicles worldwide will be equipped with batteries or fuel cells, especially high-temperature oxide fuel cells (SOFC), as other fuel gases, such as natural gas, can also be used in SOFCs [1]. The required upstream investment in factories, machines and manpower is massive. Fuel cell technology, a noiseless technology that has been known for 180 years, has now achieved a level of maturity that ensures it is here to stay. Compared to conventional technology, fuel cells produce no harmful emissions. When green hydrogen is used as a fuel, the only “emissions” are water and exhaust air, together with atmospheric oxygen. Material costs and raw material availability play a much smaller role in fuel cells than in batteries. Moreover, the green hydrogen produced with solar, wind (onshore/offshore), hydropower, or biomass can be fed into existing gas networks, making it a highly sustainable, environmentally friendly energy carrier. Producing 10 kg of hydrogen requires about 420 kWh of electrical energy. An averagely-sized wind turbine can produce this in about 8 min. To illustrate, with 10 kg of hydrogen, a fuel cell vehicle can make a return trip from Berlin to Munich. Hydrogen mobility offers clear advantages in terms of added value, infrastructure costs, elimination of residual waste and resource dependence. Thanks to low maintenance requirements and the fact that no taxes are levied (bear in mind the steadily increasing CO2 taxation), fuel cells offer much greater long-term energy efficiency from an economic viewpoint than high-maintenance combustion engines. Fuel cells make hydrogen available for mobility purposes, such as local public transport (buses and trains), heavy-duty road transport (trucks) (Fig. 3) , logistics (delivery traffic) and commercial vehicles (forestry and agriculture); refueling with hydrogen is estimated to take about 3 min for a passenger car and about 15 min for a truck. Note also that the first H2 commuter trains are already in operation (e.g. Deutsche Bahn H2goesRail project [2]). This is because the use of fuel cells on commuter trains and streetcars is practical from a purely technical perspective due to centralised depot refueling (Fig. 4). If green hydrogen produced from regenerative sources is used for refueling, CO2 emissions are eliminated. However, it should be noted that hydrogen technology has further advantages:

  • Hydrogen costs have dropped significantly in recent years.
  • The elimination of time-consuming battery replacement increases productivity.
  • The absence of hazardous acids makes fuel cells very safe for users.
  • Fuel cells have an average service life of 10 000 working hours, which improves the cost-benefit ratio enormously.
  • No additional battery charging stations are required, making infrastructure costs or intrusions into nature negligible.

The use of fuel cell systems is particularly promising for commercial vehicles, with overall fuel cell efficiencies of up to 96 % likely to generate high demand in this sector in the short or medium term. In Europe, the existing filling station network is still expanding, yet fuel cell vehicle (passenger car) sales remain limited at this time on account of high purchase costs and the narrow range of models. Nevertheless, car manufacturers in Japan and Korea see investment in fuel cell technology as a worthwhile longterm strategy that is being implemented accordingly. In North America, for example, there is an increasing focus on the use of fuel cell forklifts. With its national hydrogen strategy, Germany is a key driver of overall capability and has pledged EUR 9 billion in public funding up to 2030. According to the EU Hydrogen Strategy 2020, 10 Mt of renewable hydrogen should be produced and 10 Mt imported by 2030 [3]. Furthermore, a coalition agreement sees Germany set to become a world leader in green hydrogen research and production. Challenges of fuel cell technology and Riedhammer’s technical solutions Producing and supplying green hydrogen is not the only challenge: it’s also necessary to optimise production processes to reduce fuel cell manufacturing costs. There is certainly still plenty of potential for savings, especially when it comes to producing stack components. Individual stack components play a crucial role in performance; depending on performance, a stack may consist of more than 100 separator plates. By 2050, it is estimated that some 100 million stacks will be required. Forecasts indicate that around 40 % of these will be used in vans and minibuses, around 30 % in buses and some 20 % in heavy commercial vehicles. Only about 10 % will be used in compact-class passenger cars [1]. Here at Riedhammer, the company’s market and area of application lies in the manufacture of these individual stack components, especially the various thermal processes. Riedhammer GmbH – as the world leader in the thermal treatment of products, regardless of the process, temperature or atmosphere – provides a wide range of technical solutions for almost every thermal process. Additionally, customers benefit from worldwide availability through association with SACMI Group/IT subsidiaries/facilities. The variety of plants (continuous and periodic kilns with different conveyor systems) and the achievable plant sizes (>100 m) allow significant cost reductions and energy savings. For continuous plant concepts, Riedhammer tunnel kilns, which use roller conveyance (Fig. 5) and belt conveyance, and Riedhammer´s other kiln types are generally equipped with airlock technology and process gas injection as well as with metrological recording of all media inflows/ outflows. The same process conditions (i.e. gastight design, process gas injection, electrical heating, etc. with convective debinding and radiative sintering) can be achieved by periodic Riedhammer plants, first and foremost the electrically heated top-hat kiln (EHB) (Fig. 6). Both Riedhammer kiln systems (continuous and periodic) ensure the company’s partners achieve consistently high product quality through outstanding process repeatability. This diversity of Riedhammer concepts and technologies ensures a very high gas tightness of up to 30 ppm, temperature accuracy of ±1,5 K and precise, accurate control of kiln temperatures, pressures and atmospheres. Air circulation technology is adapted to each kiln type, which greatly accelerates degassing processes on Riedhammer plants, also with inert gas atmospheres; the products are thus conveyed to heating and sintering processes free from organics or cracks. In addition to thermal debinding, one of the greatest challenges will be the SOFC sintering process under process gas atmosphere. Here, extremely uniform flow as well as high-temperature homogeneity of the product will be crucial. On request, Riedhammer and its intragroup partners also provide extensive automation for the lines. These range from simple circulation systems to highly complex sagger handling systems, pick and place machines, articulated arm robots and so on, all with very short cycle times and the required product handling positioning accuracy. Riedhammer’s comprehensive know-how ensures our plants, employees and processes are all exceptional: this is the result of almost 100 years of experience, with nearly 10 000 industrial plants delivered to countries worldwide. Summary Only with fuel cell technology will it be possible to stay within emissions limits and remain climate neutral (Green Deal). Following a coal phase-out in many European countries, the expansion of renewable energies will be further accelerated by the European Green Deal. Since EUR 55 billion are to be made available for expansion alone, the commercial use of hydrogen is, for the first time, being made a high priority. Good technological progress regarding electrolysis (i.e. separation of water into hydrogen and oxygen by means of an electric current) now puts a breakthrough in hydrogen technology within reach, and it is quite possible that green hydrogen will one day, for example, completely replace natural gas. The mobility revolution will not succeed without hydrogen and fuel cells. However, hydrogen and battery mobility should not be seen as competitors as only a mix will ultimately lead to the achievement of climate protection targets.

References

[1] 9. Elektromobilproduktionstage der RWTH Aachen University, 26.-27. Oktober 2021

[2] Wasserstoff bei der Deutschen Bahn (deutschebahn. com); Siemens Mireo Plus H Hydrogen- Powered Trains, Germany (railway-technology. com)

[3] Hydrogen (europa.eu): https://energy.ec.europa. eu/topics/energy-systems-integration/hydrogen_ en#:~:text=EU%20Hydrogen%20strategy% 20The%20EU%20strategy%20on%20 hydrogen,and%20infrastructure%3B%20 research%20and%20cooperation%20and%20 international%20cooperation

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