A review of common natural ventilation and evaporative cooling systems for Greenhouses and the Nigerian reality

Abstract

Greenhouses simulate the "desired" environment for successful growth and development of plants. They, by design, achieve this desired environment by supplying the necessary climatic inputs needed by the plants to strive and at the same time exclude factors impeding the growth of plants, hence it is called a controlled environment. One of the common and most desired attribute of the greenhouse is its ability to provide effective cooling to the plants. This paper reviewed, extensively, the concept of evaporative cooling as applied in greenhouses. Factors like Vapor Pressure deficit (VPD), Relative Humidity, Ambient Temperature were also discussed with regards to its effects on the efficiency of the evaporative cooling system. The efficiencies of the Fan and Pad System and the Fog systems were reviewed and compared with their consequent dependence on factors like nozzle spacing, nozzle length, saturation efficiency of pad material etc. The Natural Ventilation method was also reviewed as a "stand alone " greenhouse cooling method and as an augmentation to other cooling systems. Factors like rate of air exchange, total area of vents, wind speed, vent opening angles etc. were also discussed in line with their effects on the effectiveness of the Natural ventilation method. The Nigerian Perspective on Greenhouses and its Cooling methods was also discussed with reference to local development of evaporative coolers as well as its importation, its affordability, management, availability and appliance to the Nigerian farming culture.

Effects of Various LED Light Colours on Yield and Physical Characteristics of White Oyster Mushrooms

“…Conversely, the use of red LED light was found to be inappropriate as it negatively affected the physical properties of the mushrooms and resulted in low yields. Mondal et al [13] reported in their study that longer stipe lengths and smaller pileus diameters were associated with exposure to red light, which resulted in poor mushroom quality. Thus, it can be inferred that LED light colours are a critical factor in enhancing the overall performance and yield of white oyster mushroom cultivation.…”

“…The fan facilitated the movement of air, drawing it through the wet cooling pad and exhausting it out of the chamber. This created a continuous flow of air, promoting the evaporation process and maintaining a controlled temperature environment [13] for mushroom growth.…”

“…The cellulose pad was thoroughly soaked in water for 24 hours before the experiment was conducted to initiate the cooling process, ensuring its complete saturation. The purpose was to ensure that when the air passes through the wet pad, maximum evaporation and heat extraction occur, effectively lowering the temperature in the chamber [13].…”

Design of sintered zeolite evaporative cooling system

“…Increasing the relative humidity of the storage environment will slow down the rate of water loss. The best method to increase relative humidity is to lower the temperature (Ikechukwu-Edeh et al, 2021;Vakiloroaya et al, 2014). Therefore, the aim of this study was to design an evaporative cooling system for the temporary storage of harvested fruits and vegetables in order to increase shelf life before distribution (Ali, 2020;Shashua-Bar et al, 2009).…”