1. Cooling and Ventilation
Unit: The Physical Greenhouse

2. I. Air Circulation
Definition - movement of air within greenhouse

3. Circulation Importance
Uniform air movement
Prevent temperature layering

4. 3. better air exchange around plant
CO2
H2O
3. better air exchange around plant
a. replace CO2 depleted air
b. remove high humidity
c. reduce temperature of leaf surfaces

6. Problems
Uniform air movement
Moving air through plants

7. Two Circulation Systems
Horizontal Air Flow (HAF)
Fans placed around the greenhouse
The better of the two systems

8. Circulation: HAF
HAF

9. HAF Placement

10. Polytube System Located near the peak of the greenhouse
Fan located at the end of the greenhouse
Long plastic tube with holes in it runs the length of the greenhouse

11. Polytube Circulation

12. Polytube and Heating

13. Polytube – Fresh Air

14. Reducing Temperature Shading – reduce absorbed energy
Accomplished with shade/energy curtains

15. Reducing Temperature Ventilation
Movement of outside air through the greenhouse

16. Types of Ventilation Natural Ventilation Uses convection currents
Ridge vent and side vents
Open area
Removable side wall
Removable roof

17. Natural Ventilation

18. Natural Ventilation

19. Natural Ventilation

20. Natural Ventilation

21. Types of Ventilation Motarized Ventilation Minimum – polytube system
Mixes warm greenhouse air with cool outside air
Maximum
Outside air replaces greenhouse air

22. Maximum Ventilation End Wall Ventilation Side Wall Ventilation
Fan located on one end of the greenhouse
Vent located on the other end
Side Wall Ventilation
Fans and vents located on sides

24. Reducing Temperature Cooling
Reducing temperature of the air entering the greenhouse

25. Cooling Systems Refrigeration Evaporative Cooling Pad and fan
High pressure mist/fog

26. Evaporative Cooling Why does it work?
H20(liquid) + Energy(warm air)  H20(gas) + cooler air

27. Evaporative Cooling Factors determining cooling
Temperature: outside air
Relative humidity: outside air
Temperature: inside air

28. Evaporative Cooling Factors Determining Cooling air movement shading
structure
Covering

29. Pad and Fan System
Works with the existing end wall or sidewall ventilation
Pad covers the vented area

30. Pad and Fan System
Water is poured through the pad when the system turns on
The fans for the circulation system turn on and pull outside air through the pad

31. Pad and Fan Systems Points to Consider Need to eliminate leaks
through pads
around pads
other areas

32. Need uniform wetting
holes clogged
Detergent
Algae growth
CuSO4
The closer to the pad, the cooler the temperature

33. High Pressure Mist - Fog
A pump, pumps out small droplets of water into the air
Creates a fog in the greenhouse
Problems
Salt deposits
Poor air movement

34. Fog evaporative cooling