Lightweight, flexible solar applications on demand
The booming market demand and the expansion of bifacial module applications has caused a shortage of solar glass and it is one of the problems that PV manufacturers are facing. This results in an increase of solar glass prices by up to 40%. As the module producers are not able to supply, they have to lock in supply contracts.
Bifacial modules produce solar power from both sides of the panel. It exposes both the front and backside of the solar cells. Bifacial modules come in many designs – framed, frameless, dual-glass, clear back sheets, monocrystalline cells, polycrystalline designs. The one thing that is constant is that power is produced from both sides.
Dual-glass bifacial modules dominate the market. As its more in demand, glass makers couldn’t keep pace with the supply, hence this shortage and increase in price.
Bloomberg NEF confirms that PV glass prices have increased by 75% between July and November 2020, due to this shortage. It notes that the shortage is particularly pronounced for 2mm glass used in dual-glass modules.
Due to various policy measures taken by Chinese administrators and suppliers glass production is expected to be over 35% in 2021 and the glass price to be back as before by the first half of the year.
With the prevailing shortage of glass modules, Shi Zhengrong now heads up the module startup Sunman who produce lightweight modules by encapsulating crystalline silicon (c-Si) solar cells in a polymer composite material. It weighs 5.8kg with a 5.6mm frame and 8.1kg with a 35mm frame – both in a 60-cell configuration.
The lightweight Sunman modules have ample opportunities for rooftops in sunbelt regions, such as Southeast Asia or southern China, where roofs are not constructed for weight bearing. Light weight modules have an advantage over traditional glass modules as it aptly fits lightly structured commercial rooftops which cannot handle much weight.
Sunman has shipped approximately 50 MW of modules over three years and is anticipating that its annual shipments will grow to 40 MW in 2021.
Non-crystalline PV technologies such as thin films, like amorphous silicon, dye-sensitised solar cells, copper indium gallium selenide (CIGS) PV, and organic PV (OPV) are supplied for rooftops not available to glass modules.
To produce such modules, the semiconductor material, either stainless steel or polymer is deposited onto a flexible substrate through slot-printing or ink-jet processes. Evaporative deposition has also been used for higher-efficiency thin films.
Roll-to-roll (R2R) production is a very mature technology and is more attractive due to high throughputs. In R2R production the substrate can be unwound, passed through the processing steps and rewound. R2R is the predominant process for flexible thin film production. It accounts for more than 90% of output at present
Global Solar and MiaSolé, the CIGS manufacturers have deployed huge volume of R2R flexible thin film production. Though they could make a good track record of efficiency improvements, they couldn’t scale cost effectivity.
Apart from CIGS, amorphous silicon and OPV developers have also applied R2R techniques in production. Throughput offered by R2R is promising, but its production processes cannot be optimised in small batches of wafers while c-Si can be done like that.
Sweden’s Midsummer is a flexible CIGS producer and their modules are of high quality with short cycle time and high yield and output. Their CIGS cells are cut from the stainless-steel substrate before processing, and then assembled into modules. It applied its founders’ experience in optical disk production to CIGS through its DUO production system. They applied batch PV cell production techniques on a flexible substrate, rather than R2R.
Midsummer produces its flexible CIGS Wave modules in Sweden and is planning a 50 MW production facility in Italy. Its lightweight applications and low CO2 emissions are its highlights.
The company is focusing on southern European markets where commercial and residential roofs are not weight bearing. They have signed agreements with distributors in Spain and Portugal.
In 2020 Midsummer introduced its “PowerMesh” cell interconnection technology in production and its modules now include a bypass diode between each cell, delivering enhanced shade tolerance.
Unlike c-Si producers, it is not easy for flexible thin film producers to achieve conversion efficiency. With its huge production capacity and relatively aligned technological pathways, Crystalline silicon is a formidable rival.