The PV industry witnessed advances across the supply chain in 2015, from the higher quality of Si wafers to the better ingredients and formulas for the conductive pastes. The conversion efficiency rates of cell products also rose considerably last year, resulting in modules of higher wattage output. Currently, the power outputs of mainstream multi-Si and mono-Si 60-cell modules have reached 260W and 275~280W, respectively.
Besides the increase in power output, many modules have moved from 3-busbar design to 4-busbar as well. The prominent trend in the industry, however, was the rising quality of dual-glass modules. This design feature was showcased by many major PV companies during the various international solar conventions held last year.
As the name implies, the dual-glass module is a module design that replaces the traditional aluminum frames and the backsheet substrate with another glass panel. The cells are therefore fully encapsulated in glass. Previously, the dual-glass solution was not favored by the industry compared with the traditional design because the prior generations of PV glass had limitations in many aspects, such as durability, weight, light transmittance and cost. However, PV glass manufacturers in the recent period have introduced thinner glass materials with higher light transmittance and at competitive prices. Adding that industry giants such as Trina Solar, Canadian Solar and BYD embarked on mass production of dual-glass modules in 2015, this module design has quickly caught on.
Generally speaking, the mainstream dual-glass modules that were on display at the different industry events held in 2015 used 2.5mm-thick glass panels for the front and back sides. Whereas conventional modules usually have a 25-year warranty, dual-glass modules have a warranty of up to 30 years. Another important benefit that the frameless and backless design offers is enhanced reliability for the module. Also let the module have further chance for cost reductions.
The backsheets of conventional modules face a range of challenges, from chalking and UV exposure to moisture permeability. Backsheets made of the best materials still allows a water permeance of 0.92~2.0 g/m2 each day. On the other hand, using glass as the substrate will eliminate this problem completely. Due to its superior strength, glass is also better at resisting physical erosion and chemical corrosion that could cause cracks on other substrate materials.
Moreover, dual-glass modules carry less risk of catching fire caused by the hotspot effect. Without the aluminum frames, issues such as potential induced degradation (PID) and the wearing out of EVA can be prevented. In sum, frames and other parts of traditional modules tend to collect dust and water. Their absence can actually lead to a more stable energy generation.
Even though the dual-glass design is not a fresh innovation, its market acceptance has rapidly expanded since last year. According to EnergyTrend, shipments of dual-glass modules from Chinese manufacturers grew to about 800~900MW. Trina Solar accounted for half of the China’s shipments, followed by Canadian Solar and BYD. Other major Chinese suppliers include Almaden, JA Solar, Phono Solar and Jinneng Clean Energy.
A considerable part of Chinese dual-glass shipments was to the domestic market, particularly the large-scale power plants in the country’s western region. China’s largest single PV plant using dual-glass modules is located at a tea plantation in Xishuangbanna, Yunnan. This plant has a 100MW capacity totally, phase 1 was 51MW using Trina solar’s dual glass modules. Some large utilities projects in Japan and Europe have also adopted dual-glass modules.
Furthermore, the dual-glass design is suitable for power plants located in coastal areas due to its ability to resist salt sprays. With higher light transmittance being its best advantage, this solution fits right into PV applications for agriculture and fishery. Indeed, this particular segment within the PV market is booming in China. Overall, EnergyTrend expects dual-glass module shipments to expand significantly in the Chinese market during 2016 on account of the rising demand from agricultural and fishery applications.
Looking ahead, dual-glass modules will still have to overcome some technological challenges in order to grow their market share. Though they are durable and less vulnerable to fire, they weigh a lot more than the conventional modules and are thus unsuited for rooftop systems. Moreover, dual-glass modules may be susceptible to damages from strong winds as they lack the aluminum frames that provide an extra layer of protection against physical pressures. There are also concerns raised about the clamps that fasten the modules together. Specifically, module manufacturers need to develop clamps that would not cause scratches or other damages to the edges of frameless glass panels over time.
More importantly, manufacturers will need to improve the cost-performance ratio of dual-glass modules. Rising demand across the industry has steadily pushed up the prices of PV glass since the fourth quarter of 2015. This in turn has raised the costs of dual-glass modules as well. As the number of module suppliers using this design continues to grow, however, the costs of PV glass are expected to drop and dual-glass modules will become more competitive in the market.
Currently, dual-glass modules are priced around RMB 4.2~4.3/W (US$ 0.545~0.56), just above the average price conventional modules by RMB 0.2/W (US$ 0.025~0.04). The price gap will likely shrink this year as more manufacturers start to mass produce dual-glass modules. According to EnergyTrend’s projection, dual-glass module will reach 5% of worldwide module demand. If the market share of dual-glass solution climbed to about 20~30%, the PV glass manufacturers could achieve the economies of scale that would help dual-glass modules reach cost parity with their conventional counterparts. Such a scenario could cause further shifts in the market shares of mainstream modules.
(This article is simultaneously published in PV Magazine vol. 03|2016 under an exclusive content corporation.)