- Energy Saving
Stop unnecessary venting
Common sense tells us that eliminating unnecessary venting will save energy. However, putting this theory into practice is not as simple as it sounds, especially when humidity control is a key requirement.
Heating and ventilation set-points
Well-developed plants and milder spring weather conditions mean that like most tomato growers, our Focus Nurseries now have an almost constant demand for humidity control.
Reliable humidity control can be achieved by bringing the heating and ventilation set-points very close together and it is quite common for growers to use a ventilation set-point which is only 0.5 degrees C above the heating value. Whilst this strategy works well from the humidity control perspective, there are times when it can result in the need for high pipe temperatures just because the vents have opened.
The graph below shows an example of when this happened at one of our Focus Nursery sites.
Fixing the problem
Avoiding this situation is straightforward. Use an influence on the ventilation temperature so that it increases the set-point at which the RH levels in the greenhouse fall.
In terms of settings, the suggested approach to increase the ventilation set-point by at least 0.5 degrees C as the Relative Humidity (RH) falls from 85% to 80%.
If you control humidity based on a Humdity Detector (HD), the suggestion is that you should increase the ventilation set point by 0.5 degrees C as the HD rises from 2.5g/m3 to 3.0g/m3.
Be careful though, as big changes in the settings might lead to unstable control. For example, increasing the ventilation set point by 1 degree C might give better energy savings, but the end result could be poor control of the greenhouse environment.