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Hydrogen is increasingly recognized as an eco-friendly energy source, thanks to its minimal emission of greenhouse gases and pollutants such as CO2 when it reacts with oxygen. Despite this, the challenge of storing hydrogen on a large scale persists due to its low density compared to other materials. Methods such as the use of Ammonia, LOHC (Liquid Organic Hydrogen Carrier), and the introduction of liquefied hydrogen have been explored to attain a higher density. Although Ammonia and LOHC require significant energy for synthesis and even more for the release of pure hydrogen upon decomposition, the process of liquefying hydrogen, while more energy-intensive, requires less energy for reconversion. Moreover, liquid hydrogen has the added advantage of allowing the use of a cold source during reconversion. However, long-term storage in tanks is difficult without undergoing a re-liquefaction process.
Despite these storage challenges, hydrogen is extensively utilized in various engineering applications. NASA (National Aeronautics and Space Administration), for example, uses hydrogen as rocket fuel, particularly in the second and third stages of liquid rocket engines, due to its high specific impulse and heating value. To overcome the issue of low density, NASA has developed a mixture of liquid and solid hydrogen with a density 15% greater than that of liquid hydrogen, which is more suitable for large-scale storage in rocket fuel tanks. This liquid/solid hydrogen also has a heat capacity over 18% higher than that of liquid hydrogen. Based on these developments, South Korea is conducting research on large-capacity transportation and storage solutions for liquid/solid hydrogen, including the establishment of a liquefied hydrogen terminal.
This paper presents various methods for converting hydrogen into a mixture of liquid and solid states, known as slush hydrogen, with particular emphasis on the auger, freeze-thaw, and spray methods. We have chosen the freeze-thaw method for converting into slush hydrogen. Before initiating slush hydrogen production, we conducted experiments with nitrogen using the same method to verify the experimental mechanism and to evaluate the performance of the developed insulating container. Through the freeze-thaw method, we successfully produced slush hydrogen, achieving a maximum daily production of 1.95 kg and a goal performance for the insulation container of less than 3W/m². Additionally, a theoretical study predicted the ratio of liquid to solid in slush hydrogen, and experimental results confirmed a composition of 43% liquid and 57% solid.
| Submitters Country | South Korea |
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