The Process

If we take the circle surface of an imaginary droplet, then the light that exits from the imaginary circle, without a droplet from the glass surface to air, has a surface area of r2 The Ri of glass is 1.5 and the air is 1. As a result, reflection of the exiting light takes place for the part of the surface of the circle. As the sum of the light (the flux) some of the circular area in the drop is distributed over a larger area of a hanging drop. The amount of light reflected back is then greater. The surface of a hemispherical sphere is 4 .r2. The area of a hemisphere is then 2 r2. Simply put, the reflective surface is twice as large. There is a lower Ri for the water drop to air, which means that the reflection is slightly lower, but there is also a reflection loss for the light from the glass surface to the water drop. Calculations of the reflection Ri glass to Ri water and from water to air show a loss of light. The angle of incidence of the light on the glass also plays a role here. A TiO2 coating on the inside of the glass will prevent condensation due to the hydrophilic surface. There is still glass-water air reflection loss, but the water surface is then flat, so equal to the circle surface.

Tests of light differences will therefore also have to be measured with condensation drops on the glass. The condensation droplets can be simulated by spraying the glass with water with a very fine nebulizer without the mist merging on the glass. * Condensation against the greenhouse roof, C. Stanghellini, V. Mohammadkhani, M.A. Bruins, S. Hemming, P. Sonneveld, G.J. Swinkels – 2010 (WUR).
* Condensation on diffuse glass: Influence on light transmission? T Dueck, 2012 WUR 2. The second element of light measurements by refraction differences is the measurement of (dry) coated glass with light incidence at different angles.
Depending on the Refraction (Ri) of the material, light is reflected at a transition from low to high refraction. At 90° incidence of light, the reflection is the least. At a smaller angle, the reflection increases until there is even total reflection (just think of a stone that you sail over the water surface). The angle of incidence is equal to the angle of exit of the light. There is also a difference in Ri in the transition from glass to a coating. When the light exits from high to low Ri, there is again reverse refraction. Light that emerges perpendicularly will reflect the least. A second advantage of the coating is that there is no condensation on the inside of coated glass. Water behaves on the coating like oil on a water surface (hydrophilic).

When light falls on a reflective surface, it is bent. Example: a stick half in the water no longer looks like a straight stick. We call this bending refraction. Because the angle of incidence is the angle of incidence, most bends are made when the incidence of light is low (position of the sun). Because we apply an extremely thin coating with Titanium, the light is redirected once more when it exits the glass. So a double refraction (picture 1). As a result, light at a low angle of incidence is radiated almost perpendicularly downwards. So maximum light output, especially in autumn, winter and early spring. 3 to 5% more light. This is when the crop needs a lot of light.

Added to this is the fact that at a low sun position, the light is more effectively present in the greenhouse. This means that you have effective light in the greenhouse in the morning and in the evening for up to half an hour longer.

Added to this is the fact that at a low sun position, the light is more effectively present in the greenhouse. This means that you have effective light in the greenhouse in the morning and in the evening for up to half an hour longer. Other Effects In addition, the Tio-2 has other positive effects that will give advantages in terms of light output during the growing season. The Tio-2 acts as a catalyst in the photocatalysis which occurs under the influence of UVA light. This operation is explained in another document.

This creates the following effects;