60-Second Science

System Converts Solar Efficiently to Steam

A graphite disk resting on carbon foam collects sunlight to heat water directly to steam with 85 percent efficiency. Cynthia Graber reports 


Not all solar energy capture devices make electricity directly. For example, steam generated from solar energy can turn turbines, which then produce electricity. And, in what could be especially useful in remote regions, solar steam can desalinate water and be used in sanitation and equipment sterilization.  
Now a new technique looks to be the most efficient way yet created to use solar energy to generate steam.

To absorb sunlight, M.I.T. researchers created a porous disc of graphite flakes. Underneath the disk is a layer of insulating carbon foam that floats on water. The foam prevents heat from being lost to the water, and has a tangle of interconnected small pores.

As sun heats the graphite, it creates a pressure difference that pulls water up through the foam pores, like a sponge. When the water hits the graphite hot spot, it turns into steam.
The scientists report that this inexpensive system reaches 85 percent efficiency in converting the solar energy into steam. The study is in the journal Nature Communications. [Hadi Ghasemi et al, Solar steam generation by heat localization]

The researchers hope to up the efficiency further with different materials or an improved design. All of which could cause steampunk fans to update their wardrobes.

—Cynthia Graber

[The above text is a transcript of this podcast.]

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