How is water boiled? Inside the Kettle on flame or by Electricity. But at MIT, engineers have developed a device which is basically a sponge wrapped in a bubble. It operates by soaking up sunlight to heat the water up to its boiling temperature and then release the steam by its pores.
The specialists call it “solar vapor generator”, it requires no costly mirrors or focal points to focus the light rays, rather depends on a mix of low-tech materials to soak surrounding light rays and convert it as heat. The heat is released by the pores, which draws water up.
While performing tests, they just set the solar sponge on the top of MIT’s Building — the scientists found that the sponge warmed water to 100 degrees Celsius, even on generally cool, cloudy days. The sponge likewise changed over 20 percent of the light rays to steam.
It is based on the same solar radiation absorbent they made in 2014 (A same sponge-like device made from carbon and graphite foam). The 2014 made device is also capable of boiling water to 100 degree celsius and convert 85 % of sun rays to heat and steam.
While exposed to sunlight, it was found that not only black graphite absorbed most of the incident light but also radiated sunlight as heat to the surrounding. So to minimize this loss in the form of heat, the developers started looking for an alternate material that could trap sunlight more efficiently.
In the new model of solar vapour heater, developers used an spectrally-selective absorber (It has unique absorbing properties). This absorber absorbed light in the range of visible spectrum, but did not lose the energy in form of heat. It means both requirements were achieved 1) Absorbing Light rays 2) Minimize Energy lost by heat. A thin film of copper coated with spectrally-selective absorber was mounted on a heat insulated floating foam. Now, the model stopped radiating as much heat as before.
The structure (device) was then kept inside a bubble wrap. This bubble wrap worked as green house, it trapped the solar rays and kept on internally reflecting it. This way desirable heat was achieved and also the heat was not lost due to green house effect.
One of the developers at MIT says: “What fascinates us is the innovative idea behind this inexpensive device, where we have creatively designed this device based on the basic understanding of capillarity and solar thermal radiation. Meanwhile, we are excited to continue probing the complicated physics of the solar vapor generation and to discover new knowledge for the scientific community”.
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