SEMI-CLOSED GREENHOUSE

To boost profitability, growers need to increase production and reduce inputs and waste. Maximizing yields by preventing growth-limiting conditions is crucial, especially for high-value crops in glasshouses. Modern production facilities have improved climate control through enhanced heating, cooling, CO2 enrichment, and additional lighting. However, these advancements result in higher input use and production costs, leading to a demand for more eco-friendly methods.

The semi-closed greenhouse is a promising approach that could potentially outperform traditional glasshouse technologies by increasing production, enhancing input efficiency, and minimizing waste.

The fundamental difference between traditional and semi-closed greenhouses is in climate management. Traditional greenhouses depend on passive venting for air circulation and temperature control. In contrast, semi-closed greenhouses use active mechanisms like fans and mixing chambers for atmospheric regulation. Structural differences are also notable; semi-closed greenhouses have fewer vents, thus allowing more light and establishing a protective barrier between the crops and external elements. In these greenhouses, the climate is actively controlled by circulating air beneath the crops through tubes. This air, treated in mixing chambers, can be a blend of internal and external air. The system controls temperature, humidity, and CO2 levels using techniques such as hydronic heating, CO2 injection, and evaporative cooling in hot climates. The semi-closed structure's limited air release creates a positive pressure, aiding in maintaining the desired climate and deterring pests.

The primary advantages of a semi-closed greenhouse are:

o Increased light transmission, enhancing plant growth.

o Exceptional ability to sustain high CO2 concentrations, vital for effective crop fertilization.

o The creation of a positive internal pressure that serves as a barrier against pest entry.

o Improved climate control through more regulated external air exchange, resulting in reduced heat and water requirements.

The main disadvantages of a semi-closed greenhouse are:

o Considerably higher initial investment costs for setup.

o Regular maintenance requirements for the sophisticated equipment.

o The potential loss of these benefits if the greenhouse is not installed in a suitable climate.

Semi-closed greenhouse unique aspect is the corridor located along the outer gable end walls of the greenhouse, which utilizes external air for cooling and dehumidification. This corridor acts as a mixing chamber, blending the cool, dry air from outside with the warm, moist air from within the greenhouse. Consequently, the air that is circulated back into the greenhouse becomes cooler and drier.

Here's a comparison between Semi-Closed Greenhouses and Traditional Venlo Greenhouses across various parameters

Post Height
Semi-closed greenhouse 
Ranges from 6.5 to 7.5 meters, with 7.2 meters recommended for effective air and heat exchange.
Traditional Venlo greenhouse 
Varies from 5.5 to 7.5 meters.
Truss Widths
Semi-closed greenhouse 
Uses at least 9-meter wide trusses to suit specific row layouts and accommodate under-gutter ducts.
Traditional Venlo greenhouse 
Commonly features 8-meter wide trusses, which are less expensive and suitable for most crops.
Cladding Types
Semi-closed greenhouse 
Both types use standard glass with 89% Variable Light Transmission (VLT) and low iron glass with 91% VLT, as well as diffused glass.
Traditional Venlo greenhouse 
Both types use standard glass with 89% Variable Light Transmission (VLT) and low iron glass with 91% VLT, as well as diffused glass.
Ventilation
Semi-closed greenhouse 
Employs both natural and mechanical ventilation, allowing for precise internal environment control, independent of external conditions.
Traditional Venlo greenhouse 
Relies on natural ventilation through roof vents and side windows, with ventilation extent heavily influenced by external weather.
Irrigation 
Semi-closed greenhouse 
Both greenhouse types have identical irrigation systems.
Traditional Venlo greenhouse 
Both greenhouse types have identical irrigation systems.
Climate Control
Semi-closed greenhouse 
Both types feature advanced climate control systems, including options for heating, cooling, humidification, dehumidification, and CO2 enrichment.
Traditional Venlo greenhouse 
Both types feature advanced climate control systems, including options for heating, cooling, humidification, dehumidification, and CO2 enrichment.
Pest Control and Disease Management
Semi-closed greenhouse 
Offers enhanced pest and disease management by controlling airflow through air ducts, potentially reducing pesticide needs.
Traditional Venlo greenhouse 
Offers enhanced pest and disease management by controlling airflow through air ducts, potentially reducing pesticide needs.

While Venlo-type greenhouses are a specific design known for their structural efficiency and high light transmittance, semi-closed greenhouses focus more on advanced climate control and energy efficiency, offering a more controlled environment for plant growth. The choice between the two often depends on the specific requirements of the crops, local climate conditions, and energy considerations.Выбор между этими двумя типами часто зависит от конкретных требований к культурам, местных климатических условий и энергетических соображений.

Prior to deciding on constructing greenhouses in your areas, it's crucial to carefully examine local climate data, especially air humidity, to evaluate the effectiveness of cooling systems that use wet pads.

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