In which country are mostly solar panels used?

How much water is used to clean/maintain all of the panels in a solar power plant?

• Considering solar farms are generally placed in deserts, is getting the necessary water a problem?  How often are the panels cleaned?  Are there other ways to clean the panels in cheap ways?

• Answer:

  With some nanotechnology-based inventions applied on solar panels for mission-critical applications, you don't need to clean your panels with these old-fashioned mop/brooms. Here is an example, nano-hydrofobic coating for solar panels: The principle behind a hydrophobic coating is that the layer forms a barrier so that water accumulates on the surface in an almost spherical shape, but is blocked from adhering to the surface by the barrier. This means that when a treated surface is tilted at an angle, the water rolls off the surface like "a sphere rolling down a slide," says Curran. "What is unique in this case is that the nanocoating is so thin (8 nanometers) compared to normal hydrophobic coatings that can be microns thick." (1) Also, you clean your panel through electrical charge differences: The system takes advantage of the fact that most dust particles, particularly in dry environments, have an electric charge. A transparent electrode material such as indium tin oxide delivers an alternating current to the top surface of the panel. As it swings between being positively and negatively charged, it creates an electric field that repels positively and negatively charged particles. The electric field also helps to impart a charge to uncharged dust particles, allowing them to be quickly repelled as they come in contact with the panel. The researchers have designed the system so that the electric field works its way from one side of the solar panel to the other, gradually moving the dust along until it falls off. (2) NASA was tried before some strange methods like 'vibrating panel for getting rid of dust', but it doesn't sound so effective. Mazumder’s technology is one of two approaches NASA has funded for cleaning off solar panels. The other vibrates the entire panel to shake dust loose. It’s still not clear which will prove more practical for space missions, says Surampudi, who oversaw the research into both dust-clearing techniques. Using vibrations is simpler and requires fewer modifications to the solar panel, he says. But it does not remove fine particles as well as the electrical field approach. (1) http://www.asme.org/kb/news---articles/articles/energy/self-cleaning-solar-panels-maximize-efficiency (2) http://www.technologyreview.com/news/420524/self-cleaning-solar-panels/page/ (3) http://www.technologyreview.com/news/420524/self-cleaning-solar-panels/page/2/ Page 2