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Scientists at the Massachusetts Institute of Technology (MIT) have developed a train-like concentrated solar power (CSP) system for hydrogen production, with plans to build a prototype next year. They claim that this innovative system can capture up to 40% of the suns heat to produce environmentally friendly hydrogen fuel.
MIT researchers have developed a new concentrating solar thermal energy system to produce green hydrogen. The system, which is currently in the conceptual phase, aims to use up to 40% of solar heat for the generation of ecological fuel, which represents a significant improvement over previous systems, which only achieved a utilization rate of 7%.
“Increased efficiency could reduce the total system cost, making solar thermochemical hydrogen (STCH) a potentially scalable and affordable option to help decarbonize the transportation industry,” the scientists say. “It is a great step towards the manufacture of solar fuels.”
Like other STCH designs, the conceptual system can be built around an existing ESTC plant, absorbing heat from the receiver and directing it to split water and produce hydrogen. However, at the heart of the new system is a novel two-step thermochemical reaction.
“In the first step, water in vapor form is exposed to a metal. This causes the metal to capture the oxygen from the steam, leaving the hydrogen behind,” the scientists explain. “Once the hydrogen is separated, the oxidized (or oxidized) metal is reheated in a vacuum, which acts to reverse the oxidation process and regenerate the metal. Once the oxygen is removed, the metal can be cooled and exposed to steam again to produce more hydrogen. This process can be repeated hundreds of times.”
The effectiveness of this process is related to its train-shaped design, with box-shaped reactors that circulate on a circular track. Each reactor on the train would house the metal, repeatedly passing through different thermochemical stations.
“Each reactor would first go through a hot station, where it would be exposed to the heat of the sun at temperatures of up to 1,500ºC. This extreme heat would effectively strip oxygen from the reactor metal,” the group explains. “That metal would then be in a reduced state, ready to capture oxygen from the steam. To do this, the reactor would be moved to a colder station at temperatures around 1,000ºC, where it would be exposed to steam to produce hydrogen.”
Another improvement to the system is its ability to recover most of the heat used in the process. To do this, it allows reactors located on opposite sides of the circular train-shaped track to exchange heat through thermal radiation. In addition, a second group of reactors circulates around the first train, moving in the opposite direction and operating at lower temperatures. This allows oxygen to be evacuated from the hotter interior train, without the need for mechanical pumps that consume a lot of energy.
“When fully implemented, this system would be housed in a small building in the middle of a solar field,” explains researcher Aniket Patankar. “Inside the building there could be one or several trains with about 50 reactors each. “And we think it could be a modular system, in which reactors could be added to a conveyor belt, to expand hydrogen production.”
The research team said it will build a prototype of the system next year.
“We think of hydrogen as the fuel of the future, and it needs to be generated cheaply and on a large scale,” says Ahmed Ghoniem, lead author of the study. |
