Researchers at MIT’s Department of Mechanical Engineering have developed a simple, graphite and carbon-based sponge that soaks up water and heats it using the sun’s rays. The sponge converts the water into steam that can then be used for water purification or as a power source. With low-cost materials and an 85 percent efficiency rate, the invention has the potential to become an extremely cost-effective source of solar-derived clean water and steam power for remote or developing areas.
The spongelike structure consists of a layer of graphite flakes over a bed of carbon foam. The insulating carbon foam keeps the structure afloat on water, and when sunlight hits the structure’s surface, it creates a hotspot in the graphite. Through capillary action water is drawn up through the material’s pores and evaporates as steam. The more intense the sunlight, the more steam is produced.
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Until now, solar-powered steam generation has required large-scale systems of mirrors or lenses to concentrate sunlight. Newer methods using nanoparticles have required intensifying solar energy to about 1,000 times a normal sunny day. However, the graphite sponge system only requires about 10 times the intensity of a regular sunny day, drastically reducing the costs and infrastructure required. The graphite component of the sponge is also created in a cost-effective manner: graphite is simply placed in a microwave and “exfoliated,” bubbling up to form a nest of highly porous flakes.
Lead project developer Hadi Ghasemi says, “Steam is important for desalination, hygiene systems, and sterilization. Especially in remote areas where the sun is the only source of energy, if you can generate steam with solar energy, it would be very useful.” Ghasemi also notes that the product is still in the early stages of development and has the potential to be made even more efficient than its remarkable 85 percent conversion rate by tweaking the materials used.
Via Think Progress
Photos by MIT, Courtesy of the researchers