New dehumidifying system for greenhouses

A new concept for a dehumidifier has been developed which reduces the need for ventilation and saves energy and CO2. The objective of the system is a low energy demand. This is achieved by natural convection driven air circulation and integration of sensible heat recovery. Moreover a heat pump is applied for the transformation of latent heat into sensible heat. The system is positioned below the crop not causing any light reduction and distributed throughout the greenhouse. With a computational fluid dynamics (CFD) program the optimal geometry and dimensions of the components in the system are determined. A separate model for condensation has been created because this is not included in the CFD-program. A prototype based on the best design is built and tested. The calculations and experiments are in good agreement. The system has a capacity to remove 50 to 70 ml of condensate per hour per metre length of system during humid greenhouse conditions (>80 percent relative humidity). Predictions show that 4 to 7 percent energy can be saved in a conventional greenhouse. For modern well-insulated greenhouses these savings are much higher