Comparative Energy Analysis of Dehumidification Technologies for Indoor Cannabis Operations.

Anyone who has had the opportunity to work in the Controlled Environment Agriculture (CEA) industry knows that managing the latent load of an operation is paramount to its success. For a plant to grow and thrive, it must pull water and nutrients from the growing medium, through its roots and up its stem to eventually transfer the nutrients into its growing tissue. To complete the process, this internal water must finally be exposed to the open air so it can evaporate away. A CEA facility is a farm operation that is fully contained indoors where light, temperature, relative humidity, and the atmosphere can be controlled. Most cannabis CEA facilities introduce supplemental carbon dioxide to encourage plant growth. Because of this, the grow rooms are sealed with minimal to no outside air to prevent exhausting valuable carbon dioxide. If latent removal capacity is insufficient, the relative humidity in the space quickly reaches saturation levels and the plant can no longer move water from roots to air. This can cause serious plant health issues that can eventually lead to death of the plant. Every pint of water placed in the growing medium that does not drain to waste outside the room must, eventually, be removed from the air. Sensible loads in a CEA operation are fairly easy to determine and handle due to the large lighting loads (20 – 50 watts/ft² ), but when the lights go off, it’s a different story. During the simulated nighttime, the plants reduce the amount of water they deliver to the air, but it does not disappear. Without the sensible load of the lighting system to drive the latent capacity of air conditioning, dedicated dehumidification must be used to control relative humidity. A high efficiency dehumidification system is vital to minimize the total electric consumption of the operation. This paper explores a comparative energy analysis of various dehumidification technologies used in CEA operations. The primary systems to be examined will be integrated HVAC systems with on-site heat recovery to achieve dehumidification reheat, chilled water systems with on-site heat recovery to achieve dehumidification reheat, solid or liquid desiccant dehumidification systems, and high efficiency stand-alone dehumidifiers as defined by California’s Title 24 proposed regulations for dehumidification efficiency in CEA facilities. Title 24 is a code for CEA facilities that governs dehumidification efficiency, lighting efficiency, and requirements for greenhouses. When possible, minimum allowed efficiencies and actual equipment efficiencies will be used. This analysis will focus on CEA cannabis operations, but the results could be applied to other crops, as well. [ABSTRACT FROM AUTHOR]