Performance Analysis of a Greenhouse Fan-Pad Cooling System: Gradients of Horizontal Temperature and Relative Humidity

Abstract

An experimental study is conducted to determine the performance parameters of system, as well as gradients of temperature and humidity along greenhouse when opening Fan-Pad cooling system. Measurements in the study were carried out by using seven sensors for different locations, as well as portable instruments. For this purpose, the five digital temperature and humidity sensors and two pyranometers were used during experiments. Among them, two were located outside greenhouse for external measurements. The rest one pyranometer above the crop canopy, four temperature and humidity sensors were mounted within the crop canopy along the greenhouse. Four sensors were placed according to positions defined between pad and fan. According to the experiment results, the non-uniform temperature changes, but approximately uniform humidity changes due to the crop transpiration were observed along greenhouse from pad panels to exhaust fans. When the cooling system closed, hourly mean temperature and relative humidity from Pad to Fan inside greenhouse changed between 30-33 °C and 30-47%, respectively, at outside climate conditions of 32 °C and 25%. After providing stabile cooling by opening Fan-Pad system, hourly mean temperature and relative humidity along greenhouse from pad to fan ranged between 20 -27 °C, and 50 -68%, respectively. The air temperature entering to greenhouse with air velocity of 0.8-0.9 ms -1 through pad was approximately 12-13 ºC lower than the outside air temperature. The air temperature from Pad to Fan increased approximately by 7 ºC. The method of psychrometric calculations was employed to determine the cooling efficiency of Fan-Pad system. According to the calculation result, the average of air temperatures inside greenhouse was 24.5 ºC after achieving stable cooling for outside air temperature of 31.4 ºC. The hourly mean cooling effect and cooling efficiency calculated for Fan-Pad system were determined to be 6.96 ºC and 76.8%, respectively.

Towards a Sustainable Greenhouse: Review of Trends and Emerging Practices in Analysing Greenhouse Ventilation Requirements to Sustain Maximum Agricultural Yield

“…In order to analyse the efficiency of the fan-pad systems, two distinct models were developed with fan and pad evaporative cooling systems [117], with the results showing the greenhouse efficacy could be increased through the use of such systems. When opening the fan-pad cooling systems, the relative humidity changes along with the greenhouses, from the pad panels to the exhaust fans, shows uniformity, but the temperature changes were usually non-uniform [118], which has to be considered while employing such mechanical systems within the greenhouses. The employed system in this study reduced the GH temperature from 30-33 • C to the range of 20-27 • C, and increased the humidity rate of 30-47% to 50-68%, where the outside climate conditions were 32 • C and 25% humidity.…”

Efficiency of Natural Ventilation in Central Greenhouse of Botanical Garden in Kosice

“…Extreme temperatures inside the greenhouse will limit the plant growth, as well as its quality (Dayioğlu, Silleli 2015). Greenhouse crops must not be kept for long time at temperatures higher than 30 °C in case of tropical and subtropical flora (Bailey 2006).…”

Advances in greenhouse automation and controlled environment agriculture: A transition to plant factories and urban agriculture

“…In fact, studies of different control strategies indicated that smart management of natural ventilation for manipulating the environment under specific exterior conditions is an effective approach to improve productivity and increase benefits [124] . A smart tropical greenhouse that operates on solar panels and benefits from an adaptive design and covering materials (i.e., mesh screens) will maximize the use of natural and mechanical ventilation [144,[159][160][161][162] and will be less dependent on higher-cost cooling methods such as evaporative [67,[163][164][165][166][167] and high pressure fogging systems [168] . Nevertheless, the use of anti-insect screens decreases the natural ventilation capacity and aggravates thermal conditions.…”