After the calibration period, both panels were carefully cleaned and one of the panels was sprayed with SSG to create a coating, while the other panel was left untreated. Both panels were exposed to the same ambient environment making sure that not only the solar irradiation but also the wind conditions are exactly the same.

The Baoergai grid-connected PV plant in China was built in 2012 with 30 MWp PV panels (HT60-156P-240) installed. It is located in west China where dry weather prevails and the area is frequently plagued by sandstorms, especially in winter and spring. Two stable 5 kWp PV arrays that had almost the same power generation in 2014 were chosen as experimental group (coated with the SSG) and control group (uncoated). The arrays were exposed to the same ambient environment with similar solar irradiation and wind conditions. Each array (more than 2000 panels) and had a capacity of 500 kW. Each panel comprised of 60 cells with dimensions 156 mm × 156 mm, maximum power Pm = 240 W, maximum voltage Vm = 30.5 V, maximum current Im = 7.87 A, open circuit voltage Voc = 37.5 V and short circuit current Isc = 8.49 A.

The experimental set up of the arrays with uncoated and coated glass surfaces is depicted in Fig. 2. The power generated from the arrays is transferred to the 110 kV grid through combiner boxes and PV inverters by Samlipower (Solar Ocean 500TL). Each array was connected to an inverter and the inverters were manufactured in the same batch to ensure the consistency. The data were collected by data-collector that was connected with PV inverters by PC and remote monitoring system and recorded daily every 15 min. The measured parameter was the output energy as a function of time.