Advanced multilayer coatings for solar module cover glass
In real-world use, solar module efficiency is often significantly reduced through light attenuation resulting from excessive reflection or the accumulation of dust, dirt, and sometimes snow and ice on the panel. These effects can be dramatically reduced through the use of thin-film surface coatings for the cover glass.
Surface reflection losses and panel soiling are problems which affect every solar cell technology. Minimising these losses would result in considerable improvements in the energy output over the lifetime of the module as well as lowering the requirements for module cleaning and hence water use, something which is of particular concern in many of the sunnier regions of the world. Achieving this requires the design and application of coatings to the cover glass which are not only capable of reducing these problems but also of surviving in a wide range of harsh outdoor environments for the lifespan of the module with minimal degradation to their performance.
Research into module coatings is divided into two primary areas: anti-reflection coatings, which reduce surface reflection losses, and anti-soiling coatings. Anti-reflective coatings are designed using a bespoke optical simulation package to tailor the coating to the given module technology, before being synthesised and tested in the laboratory.
Anti-soiling coatings are designed using a range of design principles and both hydrophobic and super-hydrophobic types are being investigated. Both types of coating are extensively tested using a series of cutting-edge lab-based environmental degradation procedures, as well as undergoing long-term outdoor stability testing.
Research in this area is undertaken in collaboration with colleagues at TWI and Colorado State University.
The work undertaken on antireflective coatings at CREST has been highly successful, resulting in the development of new designs tailored to match the needs of the principal photovoltaic technologies, silicon, CIGS and cadmium telluride. The coatings are extremely robust.
A number of effective anti-soiling coatings are undergoing testing, several of which have shown outstanding promise including preventing the build-up of snow on panels in a snowstorm (see photo). Work is ongoing to improve the durability of anti-soiling coatings.