Diffused glass with AR-coating - take advantage of the best of both worlds

Growing under diffused glass has many advantages; it gives better light distribution, more even growth and more photosynthesis. The more diffused the light, the lower the light transmission. The unique anti-reflection coating from Cultilene solves this problem: with this special hydrophilic coating, the hemispherical light transmission is increased by up to eight percent.

Most growers know about the advantages of diffused glass: more light dispersion and a more uniform horizontal light distribution. This reduces the shadow effect in the greenhouse and ensures a more even climate. And because less direct light hits the plant, the crop is less stressed with a lower plant temperature. The result is more even growth. Because there is no direct light on the plant, more light can also be used. This stimulates growth. Also, diffused glass gives a more generative crop and speeds up fruit development. “And last but not least: diffused light penetrates deeper into the crop to give more photosynthesis”, says Ralf Derksen, Business Development at Saint-Gobain Cultilene. According to WUR, ten percent more haze (light dispersion) usually increases yield by one percent. At the same time, however, a rule of thumb is that one percent more light will increase yield by one percent. This means that, in the greenhouse, both the quality and quantity of light play a role.

Diffusion versus light transmission

For the best possible light conditions, a grower should opt for the highest percentage of diffusion combined with the highest possible light transmission. The problem is, however, that these two factors cancel each other out: the higher the haze factor (diffusion) of glass, the higher the reflection and the lower the light transmission. Particularly during winter months, when the sun is low in the sky, the light transmission of diffused glass is inferior to that of clear glass. In other periods, enough light is normally available and diffusion has a more positive effect on growth. This is due to the deeper penetration into the crop and the more uniform horizontal light distribution.”

Unique AR coating

To increase the light transmission of diffused glass, it is possible to cover this glass with an anti-reflective coating on one or both sides. This coating reduces the light reflection and increases the hemispherical light transmission. Cultilene has developed a special hydrophilic anti-reflection coating for its diffused Albarino glass, which can be applied as an option. By applying this coating on both sides, the direct light transmission is increased by up to 5.5 percent. The hemispherical light transmission is also increased by eight percent. “In this way, a grower gets the best of both worlds”, says Derksen.

Tough and future-proof choice

Saint-Gobain is a world leader in glass coatings, which help to improving glass performance. With the SOL-Gel technique, a coating of silicon dioxide (SiO2) is applied to the glass surface. “By heating, the coating and the glass are fused together”, Derksen explains. “In this way a homogeneous structure is created, which is resistant to external influences for at least ten years. There are no dirt particles sticking to the glass and the light transmission is guaranteed for many years. Even after ten years, the light loss is a maximum of one percent, and normally even less. This knowledge is based on our own experiences: Saint-Gobain has been applying SOL-Gel technology for many years to diffused glass in solar panels. High light transmission at the time of purchase is nice, but it must still be up to standard after ten years. The choice for Saint-Gobain glass is therefore a sustainable and future-proof choice.”

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