Researchers from the University of Technology Sydney (UTS) and Queensland University of Technology (QUT) have developed a new method to improve the charging times of solid hydrogen fuel cells. Hydrogen is gaining significant attention as an efficient way to store “green energy” from renewable sources such as wind and solar. Compressed gas is the most common form of hydrogen storage, but it can also be stored in liquid or solid form. Dr Saidul Islam from the University of Technology Sydney said solid hydrogen storage, and metal hydride in particular, was attracting interest because it was safer, more compact and cheaper than a compressed gas or liquid and could reversibly absorb and release hydrogen.
“Metal hydride hydrogen storage technology is ideal for on-site production of hydrogen from renewable electrolysis. It can store hydrogen for longer periods of time and when needed, it can be converted into gas or a form of thermal or electrical energy when converted through a fuel cell,” said Dr Islam .”Applications include hydrogen compressors, rechargeable batteries, heat pumps and heat storage, isotope separation and hydrogen purification. It can also be used for hydrogen storage in space, for use in satellites and other ‘green’ space technologies,” he said.However, the problem with metal hydride for hydrogen energy storage was its low thermal conductivity, which leads to slow charging and discharging.
To solve this problem, researchers have developed a new method to improve the charging and discharging time of solid hydrogen. A study was recently published in the journal Scientific Reports: Optimizing the Design of a Magnesium-Based Hydrogen Hydride Energy Storage System.First author Puchanee Larpruenrudee, a PhD candidate in the UTS School of Mechanical and Mechatron Engineering, said faster heat removal from the solid fuel cell results in faster charging. “Several internal heat exchangers have been designed for use with metal hydride storage hydrogen. These include straight tubes, spiral coils or spiral tubes, U-shaped tubes, and fins. The use of a spiral coil greatly improves heat and mass transfer within the storage.
“This is due to secondary circulation and a larger surface area for heat removal from the metal hydride powder to the coolant. Our study further developed a spiral coil to increase heat transfer performance.” The researchers developed a semi-cylindrical spiral as an internal heat exchanger, which greatly improved the heat transfer performance. Hydrogen charging time has been reduced by 59% using the new half-cylindrical coil compared to a traditional coil heat exchanger. They are now working on a numerical simulation of the hydrogen desorption process and continue to improve the absorption times. For this purpose, a semi-cylindrical spiral heat exchanger will be further developed. Ultimately, the researchers aim to develop a new design for hydrogen energy storage that will combine other types of heat exchangers. They also hope to work with industry partners to investigate real-world tank performance based on the new heat exchanger.
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