Hydrogen is a gas used in the chemical and food industries, but there are also prospects for using it as a fuel in vehicles and generators (image: Freepik**)
Published on 02/19/2025
Agência FAPESP* – In Brazil, researchers from the Center for Carbon Research in Tropical Agriculture (CCARBON) and the Research Center for Greenhouse Gas Innovation (RCGI) have developed a new method for monitoring hydrogen production in electrolyzers – reactors that produce hydrogen and oxygen gas from liquid water by applying an electric current.
Hydrogen is a gas used in the chemical and food industries, but there are also prospects for using it as a fuel in vehicles and generators. If the energy used to produce it is exclusively renewable, such as solar or wind, it is possible to obtain so-called green hydrogen.
“In order for the electrolyzer to produce pure hydrogen, we have to make sure that after the water electrolysis process, the oxygen and hydrogen don’t mix again inside the reactor. We found that it was possible to do this by monitoring the flow of liquid between the hydrogen and oxygen using image analysis,” explains Rodrigo de Lima Amaral, a researcher associated with the RCGI – an Engineering Research Center (ERC) created by FAPESP and Shell at the Engineering School of the University of São Paulo (POLI-USP) and supported by several companies.
The new approach, which has already been patented at the National Institute of Industrial Property (INPI), makes it possible to obtain pure hydrogen using more economical techniques, such as the use of reactors that electrolyze water without a separation membrane.
Economic benefits
The elimination of membranes or diaphragms from the architecture of the cells reduces manufacturing costs and increases their durability. The separation of oxygen from the hydrogen produced is mainly achieved by the flow of liquid inside the reactor, which traps the bubbles formed during the electrolysis of water in the wall. Prior to this new form of monitoring, it was difficult to verify the purity of the hydrogen produced.
The method developed by scientists from the RCGI and CCARBON – a FAPESP Research, Innovation and Dissemination Center (RIDC) based at the Luiz de Queiroz College of Agriculture (ESALQ-USP) – makes it possible to extract quantitative information about the components of the multiphase flow inside the reactor by analyzing images of the fluid.
“The difficulty was that we had to monitor each bubble individually in this process because they tend to overlap in the image. Using an already known technique called “optical flow,” it was possible to analyze the flow images pixel by pixel and thus identify the regions of the reactor where there’s no crossing of hydrogen and oxygen bubbles,” explains the researcher.
Compensating for limitations
Amaral says that although optical flow is a widely used technique, it had never been targeted at hydrogen production. “It’s used to monitor any movement that causes the pixel in the image to move, such as identifying cars on highways or tracking people on security cameras. At the RCGI, we’ve used it in a variety of research, such as tracking the flow in oil tanks, evaluating heart pumps, and analyzing the formation of whirlpools on Mars,” he says.
But for the specific case of electrolyzers, the researchers had to correct for the limitations of optical flow. “We combined image and noise in the same analysis. We realized that when we applied the technique in this context, several sources of noise appeared that could signal the formation of bubbles that don’t actually exist. As a result, we developed new filters to eliminate the noise, making monitoring much more accurate and viable,” he notes.
The new method not only helps monitor the production of pure hydrogen in membrane-free reactors but also makes it possible to produce more stable and cheaper reactors. “This is a project that will make it possible to develop new reactors for hydrogen production. And it can be used to monitor and analyze any multiphase flow. For example, in the drinks industry to analyze the quality and effervescence of carbonated drinks,” adds Julio Meneghini, scientific director of the RCGI and professor at POLI-USP.
* With information from the RCGI.
Source: https://agencia.fapesp.br/54005
