NANO SOLAR
Engineers at UC San Diego have developed a nanoparticle-based material for concentrating solar power plants that converts 90% of captured sunlight to heat. With particle sizes ranging from 10 nanometres to 10 micrometers, the multiscale structure traps and absorbs light more efficiently and at temperatures greater than 700 degrees Celsius.Renkun Chen, mechanical engineering professor, UC San Diego Jacobs School of Engineering

Scientists have developed a nanoparticle-based material that absorbs and converts more than 90% of the sunlight to heat.

The material can vastly improve the efficiency of concentrating solar power plants (CSP) that generate power by turning turbines from the steam generated by boiling water with solar thermal power.

Where fossil fuel plants boil water by burning coal, CSPs do this by using solar heat collected by focusing sunlight from a large area into a receiver in a tower. This is done by using many sun-tracking mirrors that focus the light onto the tower painted dark to capture most of the light.

A variation of the above is where darkly painted pipes carrying a fluid runs through the area and is heated by sunlight concentrated by a vast collection of mirrors.

The team at the University of California, San Diego created a multiscale surface by using particles of many sizes in the nano range. Together they can trap and absorb more of the sunlight, increasing the efficiency of operation of the plant, says a university press release.

Traditional materials used for absorbing solar heat function only at lower temperatures, but the new material can withstand temperatures greater than 700 degrees Celsius.

They can also survive many years outdoors in spite of exposure to air and humidity unlike conventional material that needs to be overhauled every year.

The work, funded by the US Department of Energy's SunShot programme, was published recently in two separate articles in the journal Nano Energy.

Currently, CSPs produce approximately 3.5 gigawatts worth of power at power plants around the globe.

While they present a clean energy alternative, the disadvantage has been the large area of land required to erect parabolic mirrors or pipes to collect solar heat. The problem of storage has been addressed by using salt which absorbs the heat and melts, acting as a heat reservoir.