Demand for glass/glass PV module construction is growing due to the inherent benefits that allow both the back and front panel of the module to produce electricity. This is especially true in highly reflective environments like deserts, near water, rooftops, and above parking lots.
The dual layers of glass also reduce the need for bulky structures that often cause hot spots that degrade or even burn modules produced with traditional aluminium frames. According to the International Technology Roadmap for Photovoltaics (ITRPV), glass used as the back-side cover material will increase in the next decade, with roughly 25 percent of all c-Si modules produced with glass/glass construction by 2024.
Further, EnergyTrend reported that ‘even though the dual-glass design is not a fresh innovation, its market acceptance has rapidly expanded. Shipments of dual-glass modules from Chinese manufacturers grew to about 800~900MW in 2016.’ While more expensive than modules produced with plastic backsheet construction, glass/glass costs can be offset due to increased power output and predicted longer service life – including warranties of up to 30 years versus the usual warranty of 25 years for conventional modules.
These improvements, plus factors like reliability and durability, become important considerations when looking at overall lower levelized cost of electricity over the lifetime of the module.
The Case for POE-based Encapsulants
Virtually Zero PID
With all this in mind, choices for encapsulant film layers have become increasingly important in supporting glass/glass module growth. EVA-based encapsulant films have long been used in several types of PV modules. In constructions that contain glass fronts and plastic backsheets, some of the corrosive acetic acid produced from EVA can pass through the plastic backsheet. However, in glass/glass constructions, all acetic acid that is generated is trapped between layers of glass and can cause corrosion that negatively impacts module performance.
Polyolefin elastomer-based encapsulant films, like those made with ENGAGE™ PV POE from Dow, do not produce corrosive elements like acetic acid. In fact, POE-based encapsulant films exhibit virtually zero Potential Induced Degradation (PID). Encapsulant material resistance to PID takes on more importance in the field as solar cells under high-voltage stress can degrade significantly within a short amount of time. Higher levels of PID resistance result in sustained levels of module efficiency.
