Specific energy analysis of using fertilizer-based liquid desiccants to dehumidify indoor plant environments

Abstract

Controlling humidity in indoor plant environments is crucial to plant growth, but traditional dehumidification methods can be energy intensive. In this study, we evaluate the energy efficiency of a novel dehumidification concept that uses cold concentrated fertilizer solution as a liquid desiccant agent. This closes the water cycle by recovering water vapor for plant fertigation, and eliminates the need for energy-intensive desiccant regeneration. A theoretical transport model is used to conduct a parametric analysis of the specific energy performance of the system in response to desiccant temperature and other operating conditions. Specific energy of dehumidification is defined here as the ratio of the cooling load to the water vapor removal. Minimum specific energy results between 0.16 and 0.24 Wh/g are achieved at liquid desiccant temperatures between 7 and 14 °C. These results compare very favorably with other dehumidification technologies on the market, and satisfy new energy efficiency standards for indoor plant cultivation. The vapor flux associated with the minimum specific energy ranged from 1.2 to 1.6 g/m2/h. Controlling liquid desiccant temperature is shown to be critical to achieving high dehumidification rates at optimal specific energies. These encouraging results suggest that future research and development along this track can contribute to energy efficient greenhouse cultivation for sustainable food production.