Dehumidification of greenhouses is important to optimize results. ITB therefore has developed the Green Vent air handling units. With this system, that has been developed according to the principles of The New Cultivation, air is dehumidified around the crops. Subsequently, the intake air is heated by the air coming out of the greenhouse. This can be done both by heat recovery through tubes, without the air being mixed, or by recirculating part of the air.
Advantages Green Vent
Dehumidification around the plant reduces the risk of mold-forming. Lower humidity in the greenhouse also reduces condensation around the plant. Better growth results are achieved and the quality of the crops increases.
Energy is saved by using the warm exhaust air to warm up the intake air. Savings in energy costs can go upto 25%.
Green Vent Unit
The Green Vent Air Handling Unit is manufactured completely from plastic and stainless steel. The housing is produced from Uv-resistant polypropylene material according to the ‘hollow chamber principal’. The housing is assembled completely airtight by extrusion welding. The packages of tubes inside the system are produced completely from ABS and PVC. Because the system is produced completely from plastic, a long lifespan is guaranteed. The maximum capacity of these air handling units is 10.000 m3/h.
Operation
For greenhouses four types of air handling units have been developed, according to the different needs in a greenhouse. The recirculation unit has been developed in such a way that the air inside the greenhouse is extracted and (partially) recirculated. Subsequently the air is heated by a coated heating block and distributed evenly across the greenhouse by foiltubes.
The basic unit sucks fresh outside air en heats this through a heating block. There is no recirculation or air exhaust. By distributing warm fresh air inside the greenhouse, the humidity in the greenhouse is reduced.
The basic plus unit sucks in both fresh outside air and warm air from inside the building and mixes these flows of air. The air is then heated further by a heating block and blown into the greenhouse. The temperature of the incoming air is warmer than the temperature of the air in the greenhouse. Again reducing humidity inside the greenhouse.
The basic plus Heat Regaining unit sucks in both fresh outside as warm inside air. Part of the air is mixed and recirculated. Part of the air from inside the building is led through the tube packages. Fresh air is sucked past these tubes, during which heat is exchanged onto the incoming air. During this process the air is not mixed. With this basic plus HR unit energy can be saved while dehumidifying the greenhouse.
Air distribution
Suction of exhaust air takes place in the ridge of the greenhouse through a plastic channel. This channel is transparant so there is no extra shade in the building. High pressure fans are used for both intake and exhaust. The intake air is distributed evenly across the greenhouse through several perforated foil tubes. These tubes hang underneath the plants so the air is brought in as near to the plants as possible. The location of the perforations have been calculated in such a way that the air has an even temperature and is divided uniformly across the building.
Cleaning and maintenance
The exhaust air and fresh intake air both are clean, so cleaning of the system is reduced to a minimum. The intake air is filtered by a G4-fine filter before entering the system. This filter will need to be replaced periodically. Entry hatches make the system easily accesible in case of maintenance.
Installation
The airhandling unit is installed according to the plug and play principle. The system is placed at a solidified foundation and the channels and tubes are connected. Electricity and the computer are connected and the system is ready for use.
Control
The Green Vent air handling units can be controlled with equipment of almost all suppliers.