Whether you’re a commercial producer of flowers, fruits or vegetables, or an amateur gardener, you want high yields – that’s where a greenhouse comes in handy. In a season that is not suitable for plant growth, it can provide greenhouse growth period and increase yield, and is mostly used for plant cultivation or seedling raising of vegetables, flowers, trees and other plants in low-temperature seasons. The main thing is to understand that “optimal temperature” refers to the temperature at which the greenhouse is heated or cooled as needed.
When thinking about all-year-round gardening in a greenhouse, most people worry about keeping the indoor temperature in the winter. However, if the temperature in summer is too high, it is not conducive to production, so cooling the polycarbonate panel greenhouse in summer cannot be ignored.
What’s a good temperature inside a greenhouse?
In general, 80 to 85°F (26 to 29°C) is the ideal temperature for plants. But then again, it all depends on the type of plants you grow. Some plants are cold tolerant (plants like rhododendrons, daisies, marigolds, and sweet peas all need slightly cooler nighttime temperatures to grow best), while others are warm-hearted. So, keep that in mind when planning your greenhouse gardening. It is recommended that you do everything possible to keep the greenhouse temperature below 90°F (32°C).
How to cool down your polycarbonate panel greenhouse？
There are several ways to keep your polycarbonate panel greenhouse cool in the summer, especially in hot regions. The technology you will use depends on your available budget. Here, you’ll find 8 ways to keep your greenhouse cool in the summer.
Air conditioners cooling
As far as the effect of dehumidification and cooling is concerned, it is of course the best to use equipment such as air conditioners, but this method is relatively expensive and is not suitable for promotion in ordinary farmers.
Natural ventilation cooling
Natural ventilation refers to a method that uses the heat pressure caused by the density difference of the air inside and outside the building or the wind pressure caused by the outdoor atmospheric movement to introduce outdoor fresh air to achieve ventilation. It does not consume mechanical power, and at the same time, it can obtain a huge amount of ventilation under suitable conditions, which is an economical ventilation method.
Pad fan cooling
Pad fan cooling refers to the process in which high-temperature air passes through immersion pads, humidification and cooling from the outside to form cold air, and absorbs waste heat through the control room and then discharges it outdoors. It mainly uses the evaporation of water to lower the temperature, because the evaporation of water needs to absorb heat so that some heat can be taken away from the shed. At the same time, the fan is turned on to draw hot air from the glasshouse to lower the temperature.
On hot sunny days, the moisture content in the atmosphere is almost constant, which means that when the temperature reaches a high value at noon, the relative humidity is low, and the lower the relative humidity, the more obvious the cooling effect of the wet curtain. Considering the insulation of the polycarbonate panel greenhouse in winter, a layer of protective film or rack valgus protection window should be installed on the outside of the wet curtain.
The main purpose of mist cooling is to spray water into the shed in the form of mist particles. The rapid evaporation of mist particles can quickly remove heat from the air, and then exhaust the moist air from the shed for rapid cooling. At the same time, the induced draft fan is installed on one side of the polycarbonate panel greenhouse, which can be used for forced ventilation and cooling to achieve the effect of cooling the temperature, and the temperature is relatively uniform.
The system has low cooling cost, and the comprehensive use of the sunshade system has obvious cooling effect, and the cooling capacity is about 3-10 °C.
It adopts adjustable atomization time setting and has the characteristics of automatic water off, power off, small size and convenient operation. It is especially suitable for areas with low relative humidity and polycarbonate panel greenhouses with good natural ventilation. And its humidification effect is unmatched by any other system, it can promote the rapid rooting of cuttings, improve the germination rate of seeds and the survival rate of tissue culture seedlings, and create a suitable growth environment for plants. In Europe and America, it has been widely used in nurseries, tissue culture, propagation and planting greenhouses.
Roof spraying cooling
The roof spray cooling system is to spray water evenly on the roof of the polycarbonate panel greenhouse to reduce the temperature of the greenhouse. When the water flows on the greenhouse roof, the heat exchange between the water and the polycarbonate panel of the greenhouse will remove the heat inside the greenhouse. In addition, when the thickness of the water film is greater than 0.2mm, the energy of solar radiation is absorbed and taken away by the water film, which is equivalent to shading.
White reflection cooling
White reflections work well. A white coating is formed on the surface of the greenhouse, which can reflect the sunlight well, prevent a lot of heat from entering the greenhouse, and also convert the sunlight entering the greenhouse into astigmatism which is beneficial to the growth of crops. This is good for crop growth.
Utilize the groundwater cycle
Through the circulation of ground coolers and the addition of induced draft fans, underground cold water can reduce nighttime temperatures without increasing the humidity of the greenhouse air. It can also use groundwater resources and increase the lifting device, which can not only cool the temperature, but protect the environment and save energy. However, the current cost is too high.
It can be said that the most used in actual production is shading cooling. Shading can block excess sunlight from the polycarbonate panel, protect crops from strong light burns, and create suitable growth conditions for crops. The sunshade methods are even more varied, some cover the shade net to cool down, and some pour mud and ink on the shed film to cool down. The shading effects of these different shading methods are definitely different, and the most common is the use of shading nets.
The main function of using shading nets is to block strong light and reduce the temperature of the shed, and there are usually two types of black and silver-gray on the market. The black shade net has high shading rate and rapid cooling, and is suitable for short-term coverage of fields that require careful management in hot summer; the silver-gray shade net has a low shading rate and is suitable for light-loving vegetables and long-term coverage. In addition to distinguishing by color, it is also necessary to distinguish the material of the sunshade net. There are mostly two types on the market, one is high-density polyethylene, and the other is reprocessed from recycled old sunshade nets or plastic products. Sunshade nets produced with recycled materials not only have a low finish, feel hard, and often have a pungent odor, but also have a short service life, most of which can only be used for one year. The high-density polyethylene sunshade net is more durable against aging, and its service life can reach several years.
The above are the common methods to cool your polycarbonate panel greenhouse.
Also, if you are planning to a greenhouse, please feel free to contact us.