Greenhouse Environment Solution

Looking at the mechanical cooling method mentioned above as a forced cooling method, it is a passive method using the natural state, that is, a change in air condition, and can be divided into the fan-n-pad method using latent heat of evaporation of water and the forced ventilation method using fog mist. A more active method is required for a stable cooling effect due to limitations and fluctuating climate, and there is a method using a refrigeration system.

First, the Fan and Pad cooling system is a facility specialized for high-temperature and low-humidity environments mainly near the equator.
Install a pad on one wall surface of the greenhouse and install it so that it flows down along the pad from the upper pad water supply pipe.
A certain amount of water is drained from the water collecting tank, and insufficient water can be replenished through an automatic float valve and supplied to the water sprinkling pipe at the top of the pad through a pump, at which time it is supplied through a filter. Pads are 100mm 150mm thick, 600mm wide and 1000mm high, and are generally supplied by flame-retardant treatment, hardening treatment, and wet treatment, and their specifications vary. The pad has a honeycomb-like structure such as a paper box and corrugated cardboard for evaporation efficiency by widening the contact area between water and air.

This method uses the latent heat of evaporation of water, and the lower the humidity of the outside air, the greater the difference between the wet-bulb temperature and the dry-bulb temperature is more effective. In general, the cooling effect is good even if the dry bulb temperature is somewhat high at this level of humidity effectively under 50% relative humidity. The temperature of the air immediately after passing through the pad is low and humid, and the temperature gradually rises as it passes through the greenhouse. For this reason, the shorter the length of the greenhouse, the better.

Next, as a cooling method using fog mist, this is also vaporization cooling using the latent heat of evaporation of water. When water comes into contact with air with relatively low humidity and air with a lower temperature than this, heat is given to water to evaporate and the temperature of the air goes down at the same time to be. It is a facility that installs a nozzle capable of uniformly spraying high-pressure spray water inside the greenhouse, splits the water finely, and sprays it into the air to induce evaporation. It is effective in a high-temperature and dry environment. The humidity in the greenhouse, which has increased during the evaporative cooling process, must be maintained at a low humidity continuously. There are a method using a ventilation fan and a method of replacing the indoor and outdoor air by opening the greenhouse. This method should be applied after fully understanding the characteristics of the crops, since the humidity in the greenhouse rises above the appropriate humidity, causing damage such as the occurrence of diseases and pests and deterioration of the growth of cultivated crops due to various humidity.

High-pressure mist Cooling using high-pressure mist can be used with both natural ventilation and mechanical ventilation. The optimal system should be designed by carefully examining the ventilation rate, characteristics of the cultivated crops, and the climate around the greenhouse. It uses less water than the pad system and the facility cost is lower. Fine water droplets of 10 to 20 microns easily absorb heat from the air and evaporate when sprayed in the air.
This evaporative cooling method can control the greenhouse environment by contacting water and air, and the greater the difference between the dry-bulb temperature and the wet-bulb temperature, that is, the lower the humidity in the air, the greater the effect. The cooling effect is limited.

Lastly, in the case where sufficient cooling is not possible with evaporative cooling, continuous cooling is required, and in the case of cultivation of crops that are concerned about damage due to high humidity, there is a method using a refrigeration facility. There are various methods for cooling using such a refrigerator, and they are classified according to the type of heat source as a cooling/heating heat pump method using geothermal solar heat, hydrothermal heat, and air heat. Due to the high electricity consumption and high installation cost and occupying a large amount of space, there are many difficulties in installing the equipment.

On a bright and sunny summer day, the amount of sunlight penetrating through the greenhouse is 8,000,000 kcal, which is a huge amount of 9,300 kw in a 14*25 m plastic greenhouse, that is, a 7 m 2 inter-dong 100 pyeong scale 1-2w standard greenhouse.
However, about 80% of such solar heat is blocked by a plastic shading film of structures such as steel, and 70% of the heat introduced into the greenhouse is used for transpiration and evaporation of plants. If the greenhouse is empty, that is, the internal temperature will rise by more than 65℃ and the cooling load will also increase that much. should install
At this time, in order to uniformly remove the cooling load of the greenhouse, the internal evaporation unit, that is, the structure, capacity, quantity, installation location, etc. of the indoor unit, is a part that requires the consultation of an expert with experience and technology because there are many various variables.

Characteristics by Country Seasonal Characteristics Since the amount of sunlight entering the greenhouse varies according to the characteristics of each elevation above sea level, it is necessary to design the cooling system in consideration of these characteristics. In addition, it is necessary to carefully examine the surrounding environment where the greenhouse is installed to design what the heat transfer medium will be used for. The water temperature is lower than the air temperature and the heat capacity is large, so it is a very good medium to remove the condensed heat of the refrigerant during the operation of the refrigerator. In addition, there is an effect of saving more than 30% compared to the air-cooled type.

In addition, the geothermal heat pump heating and cooling method using geothermal heat also has good heating and cooling output relative to electricity consumption, that is, the COP, and can guarantee constant efficiency regardless of the weather or season. The initial investment is expensive. A heat pump, that is, a refrigeration facility capable of cooling and heating, has to dispose of the cold and warm heat taken in the greenhouse to the outside. The cooperation of experts in various fields such as equipment is necessary.

The underground heat-using heating and cooling system is a process in which sealed circulating water circulates through the refrigeration system and underground pipelines to transfer heat. The heat absorbed by the refrigeration system is dumped underground during the summer cooling season, and the heat absorbed from the underground during the winter heating season is converted into heating heat. It consists of a water pipe, a pump, a heat exchanger, etc.
Periodic cleaning, that is, customs, is required to maintain a certain performance of these facilities, and continuous facility management is required in relation to freezing prevention in winter.

There is a chiller refrigeration system as such a cooling method using water, and it is divided into air cooling type and water cooling type again according to the condensation heat removal method. As a method of heat exchange, it is a facility that circulates the water cooled in the FCU installed inside the house, that is, the heat exchanger, using piping facilities and cools the house air. However, the use of this is also limited due to the high management and initial investment costs.

For this reason, air-heat refrigeration equipment is generally used as a cooling system for greenhouses. Air heat is an air-to-air heat exchange method in which heat absorbed from the air in the greenhouse is exchanged with the outside air. The cooling performance depends on the condition of the outside air. As a result, there are many days when the maximum temperature in summer rises by 40℃ or more during the week, so research on high-efficiency refrigeration systems using new refrigerants is continuing. Nevertheless, the facility is relatively simple, easy to maintain, and the initial investment cost is low, so it is widely used for greenhouse cooling.

In this way, the cooling system of the greenhouse should be applied to the environment in consideration of the characteristics of each country and region. The problem of designing and arranging the type, size, quantity, etc. of outdoor unit capacity of the outdoor unit, refrigerator, condenser structure design, etc. Smart farm complex environment control technology that combines ICT ioT technology with integrated control such as alternate temperature management in consideration of photosynthetic characteristics of plants is a sensor and It is important to select a professional engineering company that can determine and design all of these contents in the field of expertise required for the program.