Zuobin Wang of Changchun University of Science and Technology (China), Jin Zhang of Xi’an Technological University (China) and colleagues at Cardiff University (UK), who are partners of the EU FP7 LaserNaMi project, have devised an approach to lithography, the process used to “print” microelectronic circuits, that allows them to add a pattern to the surface of a solar cell.
There are two obvious problems with photovoltaic solar panels. First, they are very shiny and so a lot of the incident sunlight is simply reflected back into the sky rather than being converted into electricity. Secondly, they get dirty with dust and debris caught from the wind and residues left behind by dust, smoke, soot, rain and birds.
Most owners of solar panels must wash them frequently, a chore many hadn’t considered at purchase.
The new process suggests that high-power, self-cleaning solar panels might be coming to market soon.
The features of the lithographed pattern are so small that individual parts are shorter than the wavelength of light. That means the incident sunlight becomes trapped rather than reflected thus passing on more of its energy to electricity-generation process that takes place within the panel.
The same pattern also makes the surface of the solar cell behave like the surface of a lotus leaf, a natural material that is known to be very water repellant, or hydrophobic, so that particles and liquids that land on it do not become stuck as there is no surface to which the droplets can grip. When it rains any deposits are sloughed away and the rainwater runs off efficiently leaving the panel clean and dry after the downpour.
The team’s work indicates that a patterned layer on top of the active part of the panel can avoid the energy losses due to reflection from the surface. It directly boosts absorption of sunlight in the visible spectrum and into the near-infrared part of the spectrum, all of which contributes to a boost to the overall electrical efficiency of the panel.
The team suggests that printing the surface of the photovoltaic cell so that it is covered with nanoscopic cones would provide the optimal combination of making the panel non-reflective and hydrophobic and so self-cleaning.
It all sounds quite good. The effort in some locations to keep the panels clean and working up to rated efficiency is a considerable effort. There remains the need for the occasional downpour, but a rinse would be much easier and less costly than a full detergent clean and rinse procedure.
One assumes that most folks and policy makers and bureaucrats and have little if any or simply no experience in solar panel operations. Its commonly assumed that the systems are mount and forget, which could be the case in an ever-reducing efficiency kind of way.
The facts are quite different making the news of the improved surfaces a very welcome innovation indeed. Lets hope the scale up to industrial production goes smoothly and quickly.
The work might be quite interesting to manufactures as there are no graphics to be found showing the details of the concept – or – these schools haven’t caught on to the public relations effect that good news and information work can aid in gathering the best students, faculty and funding as well as commercial interest.
For now wizened buyers might want to add the efforts and costs of cleaning and the added efficiency in the calculations for having a solar panel set installed. We might never hear of any progress until a manufacturer touts the improvement on a new product introduction.