Greenhouse Environment Solution

In summer, when solar radiation is strong, it is difficult to maintain a temperature suitable for crop growth only with natural ventilation. In particular, in the equatorial tropics, which is close to the sun’s altitude, a large ventilation fan with a large amount of ventilation should be designed and installed in an appropriate amount to prevent heat from sunlight from accumulating in the air in the greenhouse.

In general, the southern and western part of the greenhouse has a lot of insolation, so the temperature is high, whereas the northeast part has less insolation and the temperature is relatively low. The central part has the highest temperature due to the large amount of sunlight inflow and little air flow due to the greenhouse structure. These aspects should be considered when designing the ventilation system of the greenhouse. Ventilation is a function of adjusting the relative humidity and temperature of the greenhouse to match the environment suitable for plant growth, and it also functions to supply carbon dioxide and discharge harmful gases.

In order to properly manage temperature, humidity, carbon dioxide, and harmful gases suitable for the growing environment of crops in the greenhouse, an active ventilation plan should be devised to cope with the frequently changing outdoor environment such as day and night seasonal weather conditions.

Precipitation sensor, wind volume sensor, snow sensor, wind direction sensor, temperature and humidity sensor, solar light sensor, etc. that can measure and monitor frequently changing weather conditions in real time are properly installed around the greenhouse to collect data while communicating with the complex environment controller in the integrated control room. responds to changes in the outdoor air environment by controlling actuators such as a large number of skylights, side windows, ventilation fans, etc. installed in the greenhouse according to the integrated greenhouse environment control program. This complex environmental controller determines the amount of ventilation according to the rate of increase of the indoor temperature according to the amount of sunlight and controls the on/off control of the ventilation fans for each group by controlling the number of rotations by changing the frequency to prevent energy loss due to excessive ventilation and to prevent energy loss due to excessive ventilation. can keep

In order to manage temperature and relative humidity suitable for crop growth, the ventilation amount and ventilation rate can be calculated and a ventilation plan can be established according to the outdoor environment. The amount of outside air inflow per unit time is called ventilation CMH, and it refers to how many times the volume of space in which plants grow, that is, the amount of air in the greenhouse is replaced with outside air. The ventilation rate refers to the amount of external air inflow per effective volume of the greenhouse and is closely related to the temperature and humidity of carbon dioxide.
For example, in the case of forced ventilation in a greenhouse with an effective volume of the greenhouse (width m×length m×height m) of 1000㎥, when 3 fans with effective air volume of 300cmm are installed, the ventilation rate per hour is 300cmm/ea×60min/h× 3ea=54,000cmh

In other words, it means that 54,000㎥ of outside air per hour passes through the greenhouse. At this time, the number of ventilations per hour is 54 times, which means that the indoor air is replaced 54 times per hour and outdoor air once per minute. With the amount of ventilation, the temperature inside the greenhouse can be maintained at the level of the outside temperature.

This forced ventilation device is composed of an air intake and exhaust control device. The intake is treated with an insect screen that can block the inflow of insect pests such as flying insects, so there is no concern about blocking sunlight. can Due to the nature of the structure of the greenhouse, if there is a slope inside the greenhouse, there may be a temperature difference due to the specific gravity difference of the air. should also be considered. The ventilation design also varies depending on the size of the structural design form of the greenhouse. In the case of a standard greenhouse with a width of 7m, the length should not exceed 50m. In the case of a greenhouse with a length of 50m or more, the air introduced from the intake port is heated while passing through the greenhouse, and the cooling effect of outside air near the exhaust port As the temperature is high, there is no cooling effect due to ventilation.

That is, when the ventilation device is arranged, the air volume is calculated considering whether the width, length and height of the greenhouse are linked, and the air volume of the ventilation fan is determined. The location of the exhaust fan is determined in consideration of the greenhouse’s layout type and the inclination of the ground, and the pressure difference inside the shadow greenhouse, taking into account the structure of the greenhouse.

In a mechanically ventilated forced ventilation system, in general greenhouse design, ventilation fan design reduces airflow due to static pressure loss over the length of the greenhouse. The design of the maximum air volume of the ventilation fan, the design air volume, the wind speed, the maximum static pressure, the design static pressure, the required power, the size of the blades, etc. are the domains of experienced technicians, so it is not a simple problem.