

Highly Efficient Steam Power From a Solar Sponge

To paraphrase an old joke (if you don’t get it, ask a third grader) – what is full of holes yet still holds water and uses solar power to create steam with extreme efficiency? A new sponge-like material developed at MIT that could eventually provide low cost power generation in poor countries and a clean power alternative to coal and oil.

Traditional solar-powered steam generators use reflectors and lenses to aim and magnify sunlight at a container of water until it boils. It works but wastes a lot of power and time. A more recent high-tech method uses nanofluids – water mixed with nanoparticles that heat quickly when exposed to intense sunlight and vaporize the liquid into steam. The large amount of sunlight needed makes this alternative too costly at this time.

Nature Communications reports on the new material developed by researchers under the direction of Hadi Ghasemi in MIT’s Department of Mechanical Engineering. The material consists of a layer of graphite flakes on top of carbon foam. Sunlight on the graphite creates a hotspot which heats the underlying water, causing it to be absorbed by the sponge and drawn up through the pores in the graphite where it rises and emerges as steam.

A depiction of how the process works and the solar sponge in action.


In terms of efficiency, this material can convert 85 percent of the solar energy it receives into steam, loses very little heat in the process and can operate effectively in low sunlight. In addition, the sponge is cheap to make. Ghasemi explains what this means:

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.

Let’s hope this simple yet efficient solar energy sponge gets to the people who need it before big energy companies figure out a way to make it soak up money and power their profit machines


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