Greenhouse, or say glasshouse, is a facility used for plant cultivation. With photo-permeability and capability of heat preservation (or warming), a greenhouse can provide a warm place to breed and increase yield in periods which are not suitable for plant growth. Greenhouses are often used to grow warm season vegetables, flowers and woods in low-temperature seasons. It’s a relatively enclosed environment in which plants continuously conduct photosynthesis， thus CO2 concentration inside the greenhouse is apparently different from outside. CO2 content in the greenhouse directly affects growth of plants, for that sufficient CO2 increases chlorophyll content in plants leaves, making them glossy and green. Plants bred with sufficient CO2 bloom earlier and drop fewer flowers and fruits. Their leaf branches grow healthily and fruits are of good quality, so that they can come into market ahead of time in larger production.
Influence of inadequate or excessive CO2 to plant growth
Inadequate content of CO2: CO2 is the “food” of plants. The low concentration of CO2 will make the plants ”starving”, and significantly lower plant biomass. For example, lacking of CO2, vegetable leaves would lost their gloss and grow slower. It would bloom later with fewer female flower, and its flowers and fruits fall off more. Its leaves are lower, rough and uneven in surface. The leaves may be vertical to the main branch or hang down. It will bear more heteromorphic fruits and fewer high-quality fruits, while the total yield is low.
Excessive content of CO2: Excessive CO2 content often curves vegetable leaves and influence normal photosynthesis, which will impede plants from absorbing oxygen and proceeding well-balanced respiratory metabolism.
Therefore, in order to enhance vegetable yield, farmer households often add air fertilizer in greenhouse planting (At present air fertilizer are mainly CO2, which is an essential element for plant photosynthesis. Within limits, the higher the concentration of CO2 is, the stronger the photosynthesis will be, thus CO2 is the best air fertilizer.) to increase CO2 content. So how to decide when to add CO2 in the greenhouse?
During daytime, in greenhouse the photosynthesis of plants are prosperous, so CO2 concentration decreases sharply. At night, photosynthesis stops, and plants release CO2 during respiration, so CO2 concentration increases. Greenhouse cultivation keeps plants grow in a relatively airtight place, where CO2 concentration reaches changes greatly in a day. Before sunrise the concentration reaches 1000～1200ppm at max, 2.5~3 hours after that the concentration drops to around 100ppm, which is only 30% of atmospheric concentration, and does not recover to atmospheric level until 4 PM. Commonly, CO2 concentration that vegetable requires is 1000～1500ppm, which means that inside the greenhouse CO2 deficiency is so severe that it has become an important factor that influences vegetable production. Installation of CO2 sensors in greenhouses can ensure that alarms can be made when CO2 concentration is under requirement, so that air fertilizer can be used. In this way, edible mushrooms, flowers, herbal medicines bred in green house can be of high quality and come into market earlier. CO2 sensors decide the growth and development, mature period, stress resistance, quality and quantity of crops.
Therefore, it appears to be very important to control CO2 concentration in a greenhouse. At present, IR CO2 sensors, which are popular in the market, are designed mainly based on principle of double IR beam. The performance of these sensors are similar, and power consumption of the mainstream products are all about 100mW.
However, given the requirements of agricultural IoT, wireless module and battery powered products, NDIR CO2 sensor of low power consumption is an ideal choice. Currently the CO2 sensor of lowest power consumption worldwide is GSS COZIR-A from the UK. It samples twice per second with power consumption of only 3.5mW.
Advantages of CO2 Sensor COZIR-A
1. The equipment is of reliable performance and compact size, making it portable and easy to install;
2. Multiple wireless sensors are integrated, so that multi-parameter concurrent monitoring between joints can be implemented. the sensors are capable of calculation and storage, so they can perform relatively complex monitor according to environment change.
3. Wireless sensors with high accuracy. Transmission between joints, host and sensors are accomplished by wireless transmission. Systematic monitor and protective measures are added into the low power consumption design.
4. Except for the system, data can also be conveniently checked on the spot.
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