Protected Cropping in Warm Climates: A Review of Humidity Control and Cooling Methods

Abstract

The projected increase of the world’s population, coupled with the shrinking area of arable land required to meet future food demands, is building pressure on Earth’s finite agricultural resources. As an alternative to conventional farming methods, crops can be grown in protected environments, such as traditional greenhouses or the more modern plant factories. These are usually more productive and use resources more efficiently than conventional farming and are now receiving much attention—especially in urban and peri-urban areas. Traditionally, protected cropping has been predominantly practised in temperate climates, but interest is rapidly rising in hot, arid areas and humid, tropical regions. However, maintaining suitable climatic conditions inside protected cropping structures in warm climates—where warm is defined as equivalent to climatic conditions that require cooling—is challenging and requires different approaches from those used in temperate conditions. In this paper, we review the benefits of protected cropping in warm climates, as well as the technologies available for maintaining a controlled growing environment in these regions. In addition to providing a summary of active cooling methods, this study summarises photovoltaic (PV)-based shading methods used for passive cooling of greenhouses. Additionally, we also summarise the current humidity-control techniques used in the protected cropping industry and identify future research opportunities in this area. The review includes a list of optimum growing conditions for a range of crop species suited to protected cropping in warm climates.

Sustainable Protected Cropping: A Case Study of Seasonal Impacts on Greenhouse Energy Consumption during Capsicum Production

“…Energy efficiency is crucial to sustainable protected cropping food production. There are numerous studies on the technological advancements to improve energy use efficiency through new photovoltaic materials, LED lighting, novel greenhouse covering materials, novel cool technologies, and efficient heating systems [21]. Given the increasing demand for a year-round supply for high-quality vegetables, it is inevitable to utilise high-tech greenhouses with high yield potential but also associated high energy cost, especially in the cold and hot climate regions across the world.…”

Smart glass impacts stomatal sensitivity of greenhouse Capsicum through altered light

“…These include the even-span greenhouse designed for crop cultivation at high latitude (Sethi, 2009), optimal orientation allowing plants to receive more radiation (Xu et al, 2015), different greenhouse shapes to improve the ventilation (Katsoulas et al, 2006), and building materials utilising a special plastic film to block UV radiation and enhance light diffusion (Hemming et al, 2004). Other techniques such as vent, fog, fan cooling systems, dehumidification, and regeneration process of liquid desiccant also improve glasshouse climatic control (Lefers et al, 2016;Rabbi et al, 2019;Samaranayake et al, 2020;White, 2014). However, the high cost of these solutions indicates that an innovative alternative technique of using low emissivity 'smart glass' film, should significantly reduce the costs while maintaining adequate climate control in glasshouses (Lin et al, 2020).…”

Analysis of Inlet Configurations on the Microclimate Conditions of a Novel Standalone Agricultural Greenhouse for Egypt Using Computational Fluid Dynamics

“…They are being used to protect the plants from severe climate conditions such as high wind rates, intense sunshine, and high levels of temperature and humidity [2,3]. Such different parameters may be managed simply by opening/closing vents automatically or manually to control wind speeds, or even by choosing proper covering materials [4,5]. Using dyed glass can prevent high solar irradiance from impacting plant growth by shielding the greenhouse (GH)'s translucent walls and roof [3].…”