Scientists get creative with solar steam generation

In order to be of use, solar energy must be converted into mechanical power, electricity, or heat. The latter, called solar thermal conversion, is one of the most popular methods for solar energy harvesting. 

It includes collecting energy through special absorbers. As the collectors heat up, heat is transferred to the underlying water, and steam is produced when the water reaches a temperature of 100 °C and above. To reach this temperature, lenses or mirrors are used to concentrate the solar energy. 

In this study, however, researchers, led by Gang Chen, professor of power engineering at Massachusetts Institute of Technology (MIT), USA, were able to omit optical concentrators altogether and replacing them with low-cost absorbers that efficiently collect sunlight.  

The absorbers, along with low-cost bubble wrap and thermally-insulating foam, can dramatically minimize radiation and heat loss. 

"Our device cannot compete against optical concentrating systems purely on efficiency per area,” explains George Ni of the department of mechanical engineering, and lead author of this study¹. But since optical concentrators are usually the most costly component of a solar steam generation system, replacing them in some uses may increase accessibility to solar thermal systems. 

The team expects the scalable technology will be most suitable for applications like desalination and wastewater treatment. “In these applications, relatively lower temperatures are needed,” says Ni. 

“We are currently exploring strategies to make the device more suitable for saline and high pollutant environments.”

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