Greenhouse dehumidification with latent heat recovery

Added on 02 October 2023

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Greenhouse dehumidification with latent heat recovery

High humidity in the greenhouse reduces crop transpiration and nutrient uptake and increases the risk of fungal diseases. This is why growers often keep the vents of the greenhouse open at least a crack most of the time. This carries off the excess humidity, but you also valuable heat and CO2.

To address this problem, the Greenhouse Horticulture and Flower Bulbs Business Unit of Wageningen University & Research (WUR) is investigating various dehumidification systems that can keep the greenhouse better closed. Results in a cucumber crop with such a system show a more than 60% reduction of heat consumption.

There are several ways to dehumidify the air in a greenhouse. Opening the vents a little, or inserting outside air with ventilators, are the most common. But with these methods, dehumidification compromises the design objective of a greenhouse, which is to create a closed growing space. By using outside air for dehumidification, the greenhouse is deliberately made leaky.

In recent years, several systems for internal dehumidification have appeared on the market. With such machines, heat and CO2 remain inside the greenhouse, and excess air humidity is converted to liquid water ready to be reused for irrigation. This system is principally equal to the energy saving heat pump-based tumble dryers. However, the existing systems are mainly intended for plants growing in pots and cut flowers. Affordable internal dehumidification systems for high-wire crops (tomatoes, cucumbers, peppers) are still unexplored territory.