Bifacial module technology is being seen as one of the most promising innovations in the solar power segment. Bifacial solar modules produce solar power from both sides. These have transparent backsheets as opposed to the traditional opaque backsheets in monofacial modules, which are more commonly used. The transparent sheet allows sunlight to pass through the module, which gets reflected on to the surface underneath and falls on the other face of the bifacial module, thereby generating power from both sides. The performance of the rear-sheet is highly dependent on the albedo, that is, the proportion of the reflected irradiance. The albedo varies with the surface on which the solar power plant is installed, resulting in a wide-ranging performance output of 5-50 per cent. Some of the bifacial module manufacturing companies are LONGi Solar, Lumos Solar, LG, Prism Solar, Sunpreme, Silfab, Trina Solar and Yingli Solar. In India, bifacial modules are manufactured by Adani Solar and Waaree, RenewSys, Pixon Energy, Microsun and Contendre.
Recent developments in India
Recently, in May 2020, SunSource Energy placed an order for 105 MW of Vertex bifacial modules manufactured by Trina Solar to be used for projects across multiple states. Trina Solar will start the module shipment in the fourth quarter of 2020. Its new Vertex series of modules has a conversion efficiency rate of up to 21 per cent and can deliver more than 500 W of power from the front surface, significantly higher than previous modules. Vertex series modules come in two versions – monofacial back sheet modules and bifacial double-glass modules. In December 2019, Adani Green Energy entered into a strategic partnership agreement with LONGi Solar for the procurement of up to 1.2 GW of Hi MO4 bifacial modules by 2020. The Hi-MO4 bifacial modules were launched in May 2019 and have a cell efficiency of 22.5 per cent and module power peaking of 430 W. In June 2019, Waaree Energies launched its 400 Wp cut cell module series, Super 400. The Super 400 is a mono-PERC module with an output of 400 Wp, whereas the Super 400 Pro is a bifacial module with up to 30 per cent higher output. These modules are intended for the rooftop solar segment.
Challenges
Although bifacial module technology is slowly becoming mainstream, high costs continue to pose a challenge for Indian manufacturers. They need to bring down the cost of the technology for mass commercial acceptance since the Indian market is highly price-sensitive. Higher generation and low costs will help deliver an even lower levellised cost of energy for solar power, thereby decreasing offtaker risks and increasing investor interest in the solar sector.
Considering that bifacial solar module technology is at a nascent stage, the manufacturing equipment needs to be customised for the application. Therefore, the cost of manufacturing is high, whereas the financial return on the process and manufacturing asset investments is low. Until bifacial module manufacturing achieves mass production and economies of scale, the cost of production is likely to remain higher than that of monofacial solar modules. As a result, the adoption may remain low. Limited energy yield data for bifacial modules is also considered to be a challenge as their performance is highly site dependent. Also, there are only field tests and pilot projects available for bifacial modules with scattered on-ground performance record. Innovative designs to enhance the rear-side light capture may put the balance-of-plant equipment at a considerable risk due to the lack of standard designs and corresponding performance data.
Outlook
Technology experts anticipate the adoption of bifacial modules to increase up to 30 per cent by 2026, driven primarily by the need for more efficient solar power generation. Bifacial cell and module manufacturing requires unique and expensive manufacturing equipment. Considering the low adoption of the technology, few manufacturers are willing to make large-scale investments in the manufacturing of bifacial modules. Unique and innovative technologies such as bifacial solar modules are severely misaligned under the present solar manufacturing market conditions and business models. For greater technology adoption, the cost parameters of bifacial modules must be effectively controlled to make it more competitive. Meanwhile, information from pilot and field test projects needs to be analysed to validate the performance enhancement levels. Further, parameters such as nameplate rating, manufacturing cost, design and price need to be standardised to provide project developers with uniform information regarding the technology.
By Sarthak Takyar