The opening time and duration of skylights in glass greenhouses need to be determined comprehensively based on environmental conditions, crop needs, and greenhouse structure. The following are specific suggestions and analyses:
I. Basis for Determining Opening Time
Temperature Threshold
Summer High-Temperature Periods: When the internal temperature of the greenhouse exceeds the upper limit for crop growth (e.g., 30℃-35℃), skylights should be opened promptly to cool the greenhouse and prevent heat damage.
Winter Nights and Early Mornings: If the outside temperature is below 5℃ or the temperature difference is too large (e.g., indoor-outdoor temperature difference > 15℃), opening should be delayed to prevent cold air from directly blowing onto the crops.
Daytime Dynamic Adjustment:
Morning: When the greenhouse temperature rises to 25℃-28℃, gradually open the skylights 10%-30%, using shading nets to reduce radiant heat.
Afternoon: During the peak temperature period (12:00-15:00), skylights can be fully opened, but humidity control is necessary.
Evening: One hour before closing, gradually reduce the opening to avoid a sudden drop in temperature.
Humidity Thresholds
High Humidity Environment: When relative humidity > 85% and lasts for more than 2 hours, open the skylights in conjunction with the circulating fan to accelerate dehumidification and prevent diseases.
Low Humidity Environment: When humidity < 60%, reduce the frequency of skylight opening to avoid excessive moisture loss.
Light Intensity
Strong Light Periods (Light Intensity > 50,000 Lux): Open the skylights in conjunction with the shade net to prevent direct sunlight from scorching crops.
Weak Light Periods (Light Intensity < 30,000 Lux): Prioritize closing the skylights and utilizing the light transmittance of the greenhouse glass to store heat.
II. Operating Duration Control Strategy
Short-Term High-Frequency Mode
Applicable Scenarios: High temperature and high humidity weather or periods of high incidence of pests and diseases.
Operation Method: Open for 15-30 minutes each time, with a 1-2 hour interval for circulation, in conjunction with the fan to accelerate air exchange.
Long-Term Steady-State Mode
Applicable Scenarios: Continuous high temperature weather or nighttime ventilation needs.
Operating Procedure: Open the skylight to a fixed opening (e.g., 30%-50%) and maintain it for 8-12 hours. This requires the use of an internal or external shading system.
Intelligent Linkage Control
Temperature and Humidity Linkage: Set dual trigger conditions for both an upper temperature limit (e.g., 32℃) and a lower humidity limit (e.g., 70%) to automatically adjust the skylight opening.
Wind Speed Compensation: When the outside wind speed is >3m/s, reduce the skylight opening area to prevent cold air from entering.
III. Special Scenario Adjustments
Continuous Rainy Weather
Daytime: Open the skylight 10%-20% only during brief periods of clear weather to quickly remove moisture, then close it.
Nighttime: Completely close the skylight to prevent rainwater backflow.
Extreme High Temperature Weather
Daytime: Open the skylight to its maximum angle (e.g., 60°-90°) all day, using the evaporative cooling pad and fan system for cooling.
Nighttime: If the outside temperature is still >25℃, maintain a 30% opening for ventilation.
Crop Sensitive Periods
Seedling Stage: Open skylights only 5%-10% during the midday heat to avoid direct cold drafts.
Flowering and Fruiting Stage: Maintain skylights slightly open (5%-15%), using a CO₂ supplemental ventilation system to optimize photosynthetic efficiency.
IV. Supporting Management Recommendations
Equipment Maintenance
Monthly check skylight track lubrication and drive motor performance to ensure smooth opening and closing.
Clean skylight drainage channels before the rainy season to prevent water accumulation and leakage.
Data Monitoring
Install temperature, humidity, light, and wind speed sensors, recording data every 5 minutes to optimize ventilation strategies.
Establish historical data models to predict environmental changes over the next 24 hours and adjust skylight schedules in advance.
Emergency Plan
Develop an operation manual for extreme weather, clearly defining skylight closure thresholds (e.g., wind speed > 8 m/s, heavy rain warnings).
Equip with backup power supplies to ensure skylights can be manually closed in case of power failure.
The diffuse glass and AR-coated diffuse glass produced by Yuhua have cooperated with many large commercial greenhouses in agriculture, horticulture, nurseries and experiments. We have cooperated with large greenhouse project companies such as Havecon, Van Der Hoeven, Kubo, etc. for many years. Yuhua greenhouse glass has a light transmittance of up to 99%, and haze 5/10/20/30/50/70/75 greenhouse diffuse glass is available!
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