Automated Environmental Control Systems In Composting And Mushroom Growing

Articles

Air Handling Unit for Mushroom Growing

Air Handling Unit (AHU) is the most important part of environmental equipment used for growing mushrooms. Mushrooms are like humans, they consume O2 from air and produce CO2. We need to supply enough air to mushrooms to let them breathe as well as effectively remove CO2 away from them. Besides providing the mushrooms with air, we need to dry or wet, to chill or heat the air depends on outside climate conditions and growing subphase. All of these functions should be fully provided by AHU with set precision. When ordering a control system for the growing rooms, the grower should understand...

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The Costs Estimate For Climate Control System In Growing Rooms

To estimate the cost of expenses for environmental control in growing rooms the following must be considered: Inlet and exhaust fans Air ducts Air conditioning Water mixing valves Control and measuring instruments Humidity system Additionally it is necessary to take into account the costs for preparing a hot water (boiler), the coolant (chiller), steam (steam generator), etc. These costs depend on the volume of substrate loaded to the growing room, rate of automation and specifications of the production process. We will consider some recommendable air conditioning systems for...

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How to Choose Temperature Sensors

In order to choose sensors correctly, it is necessary to understand for what measurements they are applied and how reliable is the result of measurement. First of all, the air and compost (substrate) temperature is meant when speaking about environmental measuring parameters. The main requirements to the temperature sensors used for climate control are: measuring temperature range— from –30 to 150 °C; accuracy — to 0,1 °C; good interchangeability. Mostly, in the above mentioned range the following three types of sensors are used: thermistors, digital...

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Temperature Sensor Connection

When using resistance temperature detectors (RTDs) for temperature measurement, the additional error can be introduced by connection wires, as wires have their own resistance which depends on the ambient temperature. RTDs have two or three-wire configuration. RTDs are connected with copper wires as copper wires have a low resistivity. When two-wire configuration is used the temperature sensor resistance and the resistance of wires are added together, which introduces an error in the measurement result: Rmeas= Rt+r1+r2, where: Rmeas – measured resistance; Rt...

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Temperature Measurement

The main characteristic of measuring instruments is an error, i.e. a measurement result deviation from a true value. The maximum measuring error of glass thermometers corresponds to the value of scale division. Thermistors error depends on the type of thermistor. Semiconductor sensors error is 0.5 Celsius degrees, as a rule. RTDs error is determined by its accuracy class. When measuring temperature by means of RTDs, thermistors or semiconductor temperature sensors, the measuring error consists of sensor error and device error, i.e. the error converting the output signal into...

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Calibration of Temperature Sensors

Our clients often ask: "I have located a few thermometers and temperature meters in the same room but they show different temperatures. Which devices or thermometers should we believe? “ In any room there exist certain temperature gradients, even without ventilation. Within two meters horizontal temperature gradient may be 2°C, but a temperature difference between the floor and the ceiling may consist up to 10°C. Therefore, the difference in a few degrees of the readings within the room is not an indicator of equipment malfunction. But nevertheless if there are doubts one...

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How to Choose Humidity Sensors

For the measurement of relative humidity several types of sensors are widely available. They are Psychometers, Aspirat, Capacitive and Resistive Sensors. The basic requirements for Humidity Sensors used to maintain the climate in the mushroom growing production, are: measuring relative humidity range - from 10 to 100% accuracy - 1% RH stability to condensation Capacitive and Resistive Humidity Sensors have got the prevalence lately. These sensors are supplied with built-in converters into 0 to 10 V, 4 to 20 mA, RS485 standard signals. It allows integrating them easily...

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Calculation of Relative Humidity

The psychrometric method of humidity calculation is based on the fact that the temperature difference between wet and dry thermometers depends on the air humidity. The humidity error consists of two components: temperature measurement error and humidity error after measuring the temperature. If you have a look at any psychrometric table in which temperatures are indicated within 0.1 ° C, one can see that at about 70% humidity the error measurement of wet and dry temperature difference 0.2 °C leads to a calculation of 2% humidity error. At higher humidity the influence of thermometers...

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Calibration of Psychrometer

Humidity measurement by a psychrometer will be correct if the temperatures of dry and wet thermometers are measured properly and air flow rate around the wet thermometer is calculated properly, too. Dry and wet thermometers are calibrated in the same way as other temperature sensors - by comparing their readings with the results of standard thermometer. The difference between the readings of the dry and wet thermometers lowered into the water shall not exceed 0.1 degrees.  

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Calibration of CO2 Sensor

CO2 concentration in the air of growing rooms is measured by sensors with a range from 0 to 5000 ppm (0 to 5%). The measurement error should not exceed 100 ppm. These requirements correspond to the sensors which operation is based on the use of infrared rays. In a factory their calibration is made by specially prepared gas mixtures with a known CO2 concentration.  Balloon with calibration gas Mushroom growing farms do not have such equipment, so CO2 sensor is calibrated by outside air. Under the outside air means the air in a green area, far from the industrial sources of CO2...

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Automated Environmental Control

Automation can reduce the amount of manual labor and improve the accuracy of control parameters. Automated environmental control is considered complete when the technologist programs the growth in the controller and all actuators operate automatically without human participation, from the time when the growing room is loaded with a substrate till the mushrooms are picked and room is disinfected. During the whole growing cycle the operator only controls the proper functioning of the equipment and the technologist, if necessary, corrects climate parameters that are supported automatically by...

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