Solar energy is the most abundant source of renewable energy. But one of the main challenges of harnessing solar energy is that its harnessing technologies, photovoltaic modules (PV modules), need more terrestrial space. However capturing solar energy technologies demands more land to install, while rapid progress in its technologies bring more solutions for alternative utilization techniques to overcome these challenges. As a matter of fact, one of the promising spaces that have huge potential to produce electricity is building surfaces such as facades, windows, skylights, balconies, and canopies.
This segment of the solar industry is called the building integrated photovoltaic (BIPV). Although using dark-blue or sometimes black color of conventional PV modules is an aesthetical concern for the rapid expansion of using PV modules in buildings, researchers have come up with transparent solar panels which significantly rectified this problem. Solving this problem divides this type of solar panel into two parts, semi-transparent and fully transparent solar panels. Two important parameters play key roles in categorizing these transparent solar panels: transparency and efficiency.
Different Type of Transparent Solar panels
Semi-transparent solar panels generally include glass, encapsulant layers, solar cells, and glass. Glass is used to laminate the solar cells, usually bifacial solar cells, so that solar cells are sandwiched between them. In this type of transparent solar panel, solar cells can clearly be seen by human eyes. This is to harvest a wider spectrum of sunlight. While in fully transparent solar panels solar cells are not identified, this type of transparent solar panel looks like a frame of glass. Because they are designed to capture non-visible parts of the sunlight spectrum. Recently a group of scientists from South Korea’s Incheon National University have come up with a low-cost transparent solar cell that harness more than 57% of visible light is transmitted through it and has efficiency close to 2.1%.
It is a general rule that the transparency percentage is inversely proportional to the efficiency of transparent solar cells. It means by increasing the transparency in these solar cells the efficiency drops down rapidly. It is important to note that the fully transparent solar cell is not yet commercially available in the solar market.
The market trend shows that semi-transparent solar panels have become a more appealing option for the BIPV market, while fully transparent solar cells can be utilized in the small electronic devices such as smartphones to supply part of their electricity demands from reflected solar irradiance in the environment as a demonstration. Then, as the technology progresses to improve its efficiency it can be used as the solar windows for skyscrapers and buildings or construction material for BIPV.
One of the possible ways to increase the public acceptance of transparent solar panels is reducing their cost by substituting glass with other types of materials such as polymeric material. Thermoplastic polyolefin (TPO) with a transparent backsheet could be one option to replace the rear glass layer with it. This option has recently gained traction among bifacial PV module manufacturers for its higher reliability, gaining more power output especially from the rear side, lighter weight, and finally similar cost.
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