Toughened glass for solar cell modules is a link in the photovoltaic industry chain and belongs to the category of raw materials for solar cell modules. It is mainly developed based on the development of solar cells. Judging from the current development trend of photovoltaic technology, crystalline silicon solar cell modules, amorphous silicon thin-film solar cell modules, and photovoltaic building integration projects are increasingly demanding the use of tempered glass, which also shows the potential of the tempered glass market.
The main component of photovoltaic glass is silica, which mainly acts as a network forming body, so its amount accounts for more than half of the glass components; the second largest component is soda ash, which mainly provides sodium oxide, which can reduce the melting of glass Temperature: Limestone, namely calcium carbonate and magnesium oxide, their main function is to adjust the viscosity of the glass at a suitable value, so that the glass molding time can be shortened or extended to meet the molding requirements; it also introduces alumina raw materials, In order to improve the physical and chemical properties of the glass, such as strength, chemical stability, etc.; the last is carbon and Glauber’s salt, the two are used in combination, the main function is as a clarifying agent to eliminate bubbles in the glass, so that there are as few bubbles in the glass as possible. Improve the transmittance of glass.
The tempered glass used as the encapsulation material of photovoltaic modules has higher requirements for the following performances:
(1) Resistance to mechanical impact strength.
(2) Surface light transmittance.
(3) In the wavelength range of the solar cell’s spectral response (320~1100nm), the light transmittance is more than 91%, and it has a higher reflectivity for infrared light greater than 1200nm. This glass is also resistant to solar ultraviolet radiation, and the light transmittance does not decrease.
(4) Curvature.
(5) Appearance.
(6) The glass should be clean and free of moisture, and no bare hands should touch the two surfaces of the glass.
1). Key points for storage and use of panel glass
(1) Avoid light and moisture, stack them flat, and cover with dust-proof cloth.
(2) The best storage conditions: a constant temperature and dry warehouse, the temperature is 25 ℃ ~ 30 ℃, the relative humidity is 45%.
(3) The surface of the panel glass should be clean and free of moisture. Do not touch the glass surface with bare hands.
(4) The panel glass can be packed in wooden boxes, cartons or containers, and each box should be packed with glass of the same thickness and size.
(5) Protective measures should be taken between the glass and the glass and between the glass and the box to prevent glass damage and scratches on the glass surface.
(6) The panel glass should be handled with care and attention to safety during transportation and cleaning.
(7) The surface of the panel glass should not touch objects with higher hardness to prevent scratches.
(8) Do not wipe the glass with newspaper.
(9) When wiping the glass, it is best to use a dry cloth with good moisture absorption and no debris dipped in absolute ethanol for wiping.
2). Problems encountered in the use of panel glass
(1) Self-detonation of tempered glass.
(2) Fracture of the amorphous silicon glass layer and the trailing edge wire.
(3) As a ceiling glass, performance degradation and strength attenuation caused by environmental loads such as sunlight and snow.
(4) As a building component, the risk of aging and falling.
(5) The anti-reflection film (AR film) falls off.
3). The performance of panel glass
For panel glass, the main focus is on its optical properties, including transmittance, reflectivity, shielding coefficient, etc., in addition to safety properties, including impact resistance, debris state, etc. The main performance parameters and application ranges of different types of panel glass are shown in Table 1. The optical performance of the panel glass is shown in Figure 1, and the schematic diagram of the tempered granularity is shown in Figure 2.
| Performance parameter | Suede glass | Glossy glass | Anti-reflection coated glass |
| Visible light transmittance/% | 91.68 | 91.86 | 96.07 |
| Visible light reflectance/% | 7.93 | 7.51 | 1.03 |
| Direct sunlight transmittance/% | 91.81 | 91.88 | 96.07 |
| Direct sunlight reflectance/% | 7.63 | 7.64 | – |
| Direct sunlight absorption rate/% | 0.94 | 0.94 | – |
| UV transmittance/% | 86.01 | 85.03 | – |
| Total solar transmittance/% | 91.93 | 92.01 | 96.09 |
| Shading factor | 1.03 | 1.03 | – |
| Tempered grain size | Not less than 40 capsules in the range of 5cm x 5cm | Not less than 40 capsules in the range of 5cm x 5cm | Not less than 40 capsules in the range of 5cm x 5cm |
| Flatness of tempered glass | Within 0.1% | Within 0.1% | Within 0.1% |
| Scope of application | Photovoltaic modules, solar water heaters, solar collectors, greenhouses, etc. | Solar thin film battery modules, solar photovoltaic curtain walls, concentrated solar battery modules, solar laminated glass modules and hollow glass modules, solar flat panel collectors, LED lamps, etc. | Solar thin film battery modules, solar photovoltaic curtain walls, concentrated solar battery modules, solar laminated glass modules and hollow glass modules, solar flat panel collectors, LED lamps, etc. |
4). Inspection of panel glass
Currently, there is no corresponding international standard for photovoltaic panel glass. Related companies in various countries generally formulate their own corporate standards for production control and inspection. For example, Yingli Company’s inspection of photovoltaic panel glass refers to GB/T 9963-1998 “Toughened Glass National Inspection Standard, French Saint-Gobain Glass Inspection Standard”, QB-0041001 “Tianjin Yaohua Glass Inspection Standard” and GB 2828-1987 “Inspection Standard” “. The inspection content of photovoltaic panel glass usually includes three aspects, as shown in Table 1.
| General performance | Appearance Quality |
| General performance | Dimensions (length, width, thickness, diagonal) and allowable deviation |
| General performance | Curvature |
| Optical performance | Visible light transmittance |
| Optical performance | Direct sunlight transmittance |
| Optical performance | Iron content |
| Safety performance | Impact resistance |
| Safety performance | Fragmented state |
| Safety performance | Thermal shock resistance |
(1) Appearance quality inspection.
Inspection method: visual inspection, feel. When necessary, steel tape, micrometer, feeler, platform, and ruler can be used to measure the length of the defect.
(2) Dimensional inspection.
Inspection tools: use steel tape measure and micrometer to measure.
Inspection method: use a steel tape to measure the length, width, and diagonal of the tempered glass; use a micrometer to measure the thickness, and compare it with the drawing or “technical agreement” or national standard to see if it meets the requirements.
(3) Mechanical strength inspection.
Inspection tool: use a small steel ball weighing 1040g and a smooth surface and a steel tape measure.
Inspection method: Use an article (such as the corresponding aluminum profile) to prop up the tempered glass sample, and then place a small steel ball weighing 1040g at a height of 1000mm from the surface of the sample, and let it fall freely for impact test. The impact point is at the distance from the test. Within 25mm of the sample center. The impact on each sample at the same position is limited to one time to observe whether it is damaged.
(4) Tempering grain size.
Test tool: Use impact pen and tape to test.
Testing method:
①Put the glass flat in the box, fix the edges around it, and use an impact pen to impact on the center line of the longest side of the glass about 20mm from the periphery.
② Count the sample fragments within 10s to 3min after the impact glass is broken. When calculating the fragments, the part within 80mm from the impact point and 20mm from the edge should be removed, and the part with the largest fragments in the sample should be taken. In this part, a 50mm×50mm box is used to calculate the number of fragments in the box, across the edge of the box The fragments are counted as 1/2 fragments.
(5) Curvature.
Inspection tool: use steel ruler and feeler gauge to test.
Testing method:
① Put the sample at room temperature for more than 4 hours, and place the sample vertically during measurement, and place 2 blocks on the 1/4 below the long side.
② Use a straight ruler or metal wire to close the two sides or diagonal direction of the product horizontally, use a feeler gauge (see Figure 3) to measure the gap between the straight edge and the glass, and use the percentage of the ratio of the arc height to the chord length To indicate the degree of curvature in the bow shape.
③When measuring local waveforms, use a straight ruler or a metal wire to measure along the 25mm direction parallel to the edge of the glass, and the measurement length is 300mm. Measure the height of the wave trough or peak with a feeler gauge, and divide by the percentage of 300mm to indicate the curvature of the wave.
(6) Other performance inspections.
The testing standards and testing methods for other properties of panel glass are shown in Table 2.
| Test items | standard requirement | Test Methods |
| Light transmittance (350~1800nm) | ≥91% | ISO 9050-2003 |
| Thermal shock resistance | The temperature difference is not destroyed | |
| Damp heat test | After 1000h, no phenomena such as efflorescence, discoloration, white spots, etc. that affect light transmission are allowed | IEC 61215-2005, IDT 10.13 |
| Wind pressure resistance | 5 400Pa | IEC 61215-2005, IDT 10.13 |