Methanol reformers convert easy-to-transport methanol into hydrogen. However, conventional reformers have a number of drawbacks such as catalyst attrition. Researchers from the Fraunhofer Institute for Microengineering and Microsystems IMM are working on an innovative methanol reformer for mobile applications to overcome these challenges.
Transporting hydrogen can be a complex process. Converting hydrogen into methanol can provide a solution, as not only is methanol much easier to transport than hydrogen, it can also be stored almost unlimited at ambient pressure. This paves the way for the production of green hydrogen in sunny regions and its conversion into methanol and its simplified transport.
Utilizing methanol as a hydrogen carrier and converting the methanol back into hydrogen. © Fraunhofer IMM
The carbon dioxide required to produce methanol could either be extracted from the atmosphere or obtained from industrial processes, such as cement production. Methanol has a very high energy density—producing around 4.8 kilowatt-hours of energy per liter—a figure that is considerably higher than that of compressed hydrogen. In addition, the International Energy Agency forecasts highly attractive costs of around six cents per kilowatt-hour for methanol.
To utilize the energy stored in the methanol, a methanol reformer and steam are used to convert it back into hydrogen and carbon dioxide at the place where the hydrogen is needed, such as the car. The overall carbon footprint is therefore neutral. However, there are still a number of drawbacks with conventional reformers.
The catalysts needed for the reactions are composed of a copper-zinc-oxide powder that is added to the reactor in the form of extruded pellets. However, the inevitable movements in mobile applications lead to catalyst attrition that contaminates the fuel cell. The catalyst material is also not fully utilized and the reaction rate is low owing to relatively low reaction temperatures.
Heat management is also a challenge: the reactor requires heat supply to drive the steam reforming reaction—but this is where efficiency is lost. Heat from the fuel cell off-gas also cannot be utilized efficiently.
In the scope of a multitude of publicly funded and industry projects, researchers at Fraunhofer IMM are developing methanol reformers that can overcome these challenges.
For example, the reformers they are developing for mobile applications offer various advantages. Among them is a much lower space demand—one-sixth, around 17%, of the space that a conventional reformer of comparable performance class would require—which is extremely important for mobile applications. The researchers have also optimized the catalyst technology.
Automated prototype of a 5 kW methanol reformer from Fraunhofer IMM.
We are opting for catalyst coatings containing precious metals similar to those used in automotive catalytic converters, because there is no attrition with these coatings. Less catalyst material is required as a result. Because our catalyst materials also have a higher activity, the amount of catalyst required is reduced even further, and consequently the costs.—,Dr. Gunther Kolb, Deputy Institute Director and Division Director at Fraunhofer IMM
While conventional catalysts increasingly produce by-products such as carbon monoxide when operated at partial load, this is not the case with the catalyst from Fraunhofer IMM.
The research team has also optimized the heat management, and in doing so has optimized the reformer’s energy efficiency as well. The team coats plate heat exchangers with the catalyst material and combines them into stacks of up to 200 plates. When the gas flows over the plates, it comes into contact with the catalyst and is also heated highly efficiently in the small channels.
By utilizing the waste heat, we achieve excellent heat integration and high system efficiency.—Dr. Kolb
The reformers are suitable for mass production; they can be produced by similar processes established for high-pressure resistant automotive heat exchangers.
At present, the researchers are working on a prototype with 35 kW of power which is foreseen to be completed by the middle of 2022.
This is a long-term project; various prototypes are being integrated into land vehicles so that we can test them.—Dr. Kolb
For maritime applications, the researchers are developing a reformer providing 100 kilowatts of power. In the long term, it is even conceivable that the reformers that are currently being produced from steel will be made from lightweight materials such as titanium—a crucial consideration when introducing the technology into automotive applications as a strategy for the reduction of weight and energy consumption.
Fraunhofer is running a webinar on “Methanol as a sustainable hydrogen carrier” using methanol reformers on 30 March.