ORNL develops low-cost, self-cleaning coatings for solar reflectors

Superhydrophobic surface surrounded by a layer of water on an untreated surface.

A team led by Scott Hunter at the Oak Ridge National Laboratory (ORNL) Measurement Science and Systems Engineering Division has begun a two year project to develop durable, self-cleaning, optically transparent coatings for heliostats and collector mirrors at concentrat­ing solar power facilities.

The research, sponsored by the Concentrating Solar Power (CSP) Program of DOE’s Sunspot Initiative, is based on ORNL’s superhydrophobic tech­nology.

CSP plants, typically located in deserts, use hundreds of thousands of large mirrors to reflect solar ener­gy onto receivers for energy conver­sion. Routine cleaning via jet spray­ing and manual scrubbing, involving up to a million gallons of deionized water, is required to remove dirt and dust and maintain reflectivity. The cleaning poses challenges including high labor and water costs, com­petition with local communities for water, and environmental impacts of the runoff. In superhydrophobic coating, a nanostructure is applied to a hydro­phobic surface, making it essentially impervious to wetting by water. ORNL researchers have determined superhy­drophobic surfaces are also resistant to aqueous solutions and viscous liquids, such as mud, and many solid particles. ORNL’s unique coatings consist of particles suspended in polymeric binders and do not use conventional vacuum deposition or chemical etching techniques. This makes them potentially inexpensive and easily applicable on most surfaces using conventional spraying or paint­ing methods.

Superhydrophobic surface surrounded by a layer of water on an untreated surface.

ORNL has demonstrated that transparent, self-cleaning coatings can be applied to small laboratory samples. In the first year, the project aims to develop self-cleaning coatings that are durable while optimizing optical transparency. Field testing of coating performance will be per­formed in the second year.

Multifunctional superhydropho­bic coatings also impart resistance to corrosion, icing, and biofouling. They are promising for numerous energy-related applications, includ­ing overhead power cables, infra­structure, solar panels, airfoils, coast­al and offshore power and structural equipment, and ship hulls.


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