This article explains how a retractable roof works and how the Priva Compass can control it.
How is retractable roof control different than greenhouse control?
A traditional greenhouse is designed to control the climate of the crop area. Using combinations of heating, cooling, shading, lighting, misting, air circulation and CO2, we can create an ideal environment for the crop to flourish.
The concept of the retractable roof is completely different. When using the retractable roof system, the roof and walls are kept retracted as much as possible to allow the crop to grow in the natural outside environment. The roof and walls are only used to cover the crop to protect it when the outside conditions are less than ideal. Depending on outside conditions, one of four different control modes is selected. These modes are described here:
Greenhouse mode is used when the outside temperature is low. Typically the roof and walls cover the crop if the outside temperature is less than 17 degrees Celsius. In this mode, the retractable roof systems works like a traditional greenhouse, using the roof as a vent. The roof is allowed to modulate to maintain desired temperature and humidity. Regular greenhouse controls such as heating, misting and air circulation are also active in this mode.
Courtyard mode is typically used when the outside temperature is between 17 and 23 degrees Celsius. The roof is uncovered allowing the crop to receive the full amount of sunlight that is available. The walls are left up, providing a wind break for the crop.
Open field mode
Open field mode is typically used when the outside temperature is between 23 and 28 degrees Celsius. The roof and walls are uncovered allowing the crop to grow in it's natural unprotected environment.
Shade house mode
Shade house mode is typically used when the outside temperature is above 28 degrees Celsius. The roof partially covers the crop, protecting it from intense sunlight. This allows the plant temperature to remain cooler allowing transpiration to continue to occur. The roof may also be covered if the humidity levels are too low.
What can we control in a retractable roof system?
Many different motor controls can be involved with a retractable roof system. These include:
- Roof area - The motors for the roof area draw the plastic over the roof, creating a canopy over the roof area. The roof motors can have two different controls. One control is for the roof vent and one control is for the rain vent.
- Roof vent - The roof vent is the main control for the roof and typically covers the entire crop area unless a rain vent is also used.
- Rain vent - The rain vent is designed with a plastic overlap that allows the roof area to be uncovered slightly to allow air exchange while still maintaining protection from the rain.
- Shading / Energy curtains - The curtain control is not specific to the retractable roof system but uses the same curtain controls as a traditional greenhouse. Curtains can be forced open in specific control modes.
- Wall area - Individual controls are available for each of the four walls of the retractable roof system. Depending on the wind direction, they can operate as wind or lee vents.
- Insect curtain - A separate control is available for an insect curtain.
In addition, all the traditional greenhouse controls such as heating heating, cooling, lighting, air circulation, CO2, misting, irrigation, water systems and energy systems are available.
What else is available?
Within the retractable roof system there are many features available.
- Rain protection - For each motor control, you can set how the control can react when rain is detected.
- Wind speed protection - There are up to five levels of wind speed protection. At low wind speeds, you can set how the controls are to react to protect the crop from wind damage. If the wind speed is very high, you can set how the controls are to react to protect the structure from wind damage.
- Wind direction control - The side walls can be set to operate as wind or lee walls, depending on the current wind direction.
- Black plate temperature - The selection of control modes can be done based on the reading of different types of sensors. One of these types is the black plate temperature. A temperature sensor is placed within a black plate that is on the weather station. If there is no sunlight, this sensor would read the same as the outside temperature. As the sunlight intensity increases, it has a warming effect on the black plate, raising the temperature. Wind speed has a cooling effect on the black plate sensor, lowering the temperature. The black plate temperature measurement is a good indication of the heat stress on the crop