A multi-stage membrane system for cooling and water recovery in horticultural greenhouses

Pasqualin, Paris ORCID: 0000-0001-9546-5705 (2023). A multi-stage membrane system for cooling and water recovery in horticultural greenhouses. University of Birmingham. Ph.D.

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Abstract

The increasing issues of water scarcity and food insecurity highlight the necessity to utilise water and produce food more efficiently. Agriculture, which accounts for 70% of global water usage, is related to both these issues. Controlled-environmental greenhouses have been investigated as a potential solution, with liquid desiccant air-conditioning showing promising results. However, controlled-environmental greenhouses face challenges in hot climates. This is because conventional liquid desiccant air-conditioning utilises thermal energy-intensive liquid desiccant regenerators, highlighting the need for an alternative regenerator with lower energy requirements. Thus, a comparison of six membrane-based desalination technologies was conducted, and multi-stage nanofiltration was identified as the most promising for use as a liquid desiccant regenerator (Chapters 1 and 2). After conducting a steady-state investigation on multi-stage nanofiltration regeneration combined with liquid desiccant air-conditioning for greenhouse applications, it was found that the proposed system could achieve better indoor conditions for crops compared to thermal regenerators and conventional cooling technologies (Chapter 3). Consequently, the practical feasibility of nanofiltration regeneration was demonstrated through dead-end filtration experiments using a 1-stage regenerator (Chapter 4) and cross-flow filtration experiments using a 2-stage regenerator (Chapter 5). Additionally, a 2-stage regenerator model was developed and verified with errors below 11% compared to the experimental data (Chapter 5). The verified model was then applied to a dynamic simulation of a greenhouse using the proposed system (Chapter 6). The proposed system enables year-round cultivation and saves 50% of water in desert and semi-arid climates where crop production is challenging, and 30% in tropical climates where agriculture typically overuses water. By reducing water demand and enabling year-round cultivation, the proposed system addresses the issues of water scarcity and food insecurity in hot climates.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):