2023-10-18 18:45:26
There is a lot of talk about hydrogen as the fuel of the future, but that will only become a reality when hydrogen can be obtained cheaply and on a large scale. The situation may begin to change from now on, as scientists have devised a system to produce hydrogen in a clean and profitable way. The processes used so far only meet one of these two conditions.
Currently, hydrogen is largely produced through processes that involve the use of natural gas and other fossil fuels, making this “green” fuel a “gray” energy source from the beginning of its production until its completion. end use.
Instead, solar thermochemical hydrogen, or STCH, offers a completely emissions-free alternative, relying entirely on renewable solar energy to power hydrogen production. Unfortunately, the designs devised so far for solar thermochemical hydrogen production have limited efficiency: only about 7% of incoming sunlight is used to produce hydrogen; In other words, the performance is low and the cost is high.
In a big step toward making cheap, clean fuels from solar energy, an international team led by Aniket S. Patankar of the Massachusetts Institute of Technology (MIT) in the United States has invented a new fuel-free system. fossils but only solar energy that takes advantage of up to 40% of the Sun’s heat to generate much more hydrogen. Increasing efficiency could reduce the total system cost, making solar thermochemical hydrogen a viable large-scale and affordable option to help decarbonize the transportation industry. The goal is to bring the cost down to $1 per kilogram of hydrogen.
Like other proposed designs, MIT’s system would be combined with an existing solar heat source, such as a concentrated solar plant, a circular array of hundreds of mirrors that collect and reflect sunlight onto a central receiving tower. Working in combination with such a solar plant, the solar thermochemical hydrogen production system would absorb some of the heat generated and direct it to break down water and produce hydrogen. This process is very different from electrolysis, which uses electricity instead of heat to split water into hydrogen and oxygen.
The key to a solar thermochemical hydrogen production system is a two-step thermochemical reaction. In the first step, water in vapor form is exposed to a metal. This causes the metal to take up oxygen from the steam, leaving only hydrogen, which is then collected. This “oxidation” of the metal is similar to the oxidation of iron in the presence of water, but occurs much more quickly. Once the hydrogen is separated, the oxidized (or oxidized) metal is reheated in a vacuum, which reverses the oxidation process and regenerates the metal. Once the oxygen is removed, the metal can be cooled and exposed to water vapor again to produce more hydrogen. This process can be repeated hundreds of times without any problem.
The MIT system is designed to optimize this process, making it much cheaper than other similar systems.
Basic diagram of the new system, based on modules connected sequentially, like train cars. The left end is the hottest, while the right end is the coldest and where hydrogen is extracted and water is added. (Image: Ahmed Ghoniem, Aniket Patankar, et. al. CC BY-NC-ND 3.0)
Patankar and his colleagues present the technical details of their new system in the academic journal Solar Energy, under the title “A comparative analysis of integrating thermochemical oxygen pumping in water-splitting redox cycles for hydrogen production.” (Source: NCYT from Amazings)
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