In Controlled Environment Agriculture (CEA), the primary source of moisture is transpiration. This is the process where moisture supplied to a plant is carried from the roots to the leaves, where it is released as vapor. In plants that are actively growing, water is continuously evaporating from the surface of the leaves. Transpiration rates are dependent on a number of factors, including temperature, humidity, sunlight, soil type and airflow. In general, 97% – 99.5% of the water taken up by the roots is put back into the atmosphere.
In CEA Applications, moisture is removed from the space through infiltration, air conditioning, and mechanical dehumidification. Infiltration generally provides an insignificant impact on the total moisture load. Air conditioning will provide some dehumidification, but the primary design objective is to control the sensible load and as a result; high efficiency air conditioning systems are not designed to control the latent load. Mechanical dehumidification with a Model 1870 dehumidifier is designed to control the moisture load in a space.
The relative humidity requirement during cultivation is dependent on plant stage. In an open space, relative humidity varies with temperature and the temperature in the space varies with elevation (vertically) as well as proximity to outside walls. The Model 1870 dehumidifier, with a built in control and humidity sensor, will turn on its blower every hour to accurately measure and control the humidity in the space. Optionally, with an external humidity control placed at canopy height, the dehumidifier will react to and control the humidity level in close proximity with the plants in real time.