How to design a semi-closed greenhouse ?

1. What is a semi closed greenhouse ?

The corridor, located on the outer gable of the greenhouse, uses outside air for dehumidification and cooling. Thus, the corridor is used to mix inner air with external air. This phenomenon represents the air treatment of semi-closed greenhouses, mostly used for Venlo glass (Kubo, Van der Hoeven, Richel…) and plastic (CMF, Richel…) ones.

This system aims to :

-dehumidify the atmosphere of the greenhouse by renewing and drying out the air inside, due to outdoor air (during the night and in the morning)

-cool dry inner temperature with pad cooling system, on external side of the corridor

-reduce the amount of harmful insects, thanks to overpressure.

-control the climate of the greenhouse avoiding the gap of temperatures

-optimize the use of energy and CO2

Heating system is composed of :

-air ducts below crops’ gutters for the diffusion of warm/cold air.

-low temperature network (30-40°C) placed in in vegetation

-high temperature network (70-80°C) placed on the ground to ensure heating.

Cooling system could be composed of :

-pad and fan system using evaporative cooling

-fog system using evaporative cooling

2. Semi-closed greenhouse design in Hortinergy

The semi-closed greenhouse model includes :

  • Climate control
  • Equipments
  • Regulation
semi-closed greenhouse design semi-closed greenhouse design and model in Hortinergy

The model implements the following equipements :

  • Controlled  external ventilation for dehumidification,
  • Air recirculation in tubes,
  • Electricity energy consumption of fans,
  • Adiabatic cooling with fog or pad  system.
Hortinergy form for a semi closed greenhouse designHortinergy form for a semi closed greenhouse design

Crop evapotranspiration is modelled with climatic parameters as well as type and  development of the crop. The climatic parameters are temperature, relative humidity, solar radiation, inner air velocity…

3. Outputs of semi-closed greenhouse design

Hortinergy provides a comprehensive analysis of the :

  • Hourly inner climate,
  • Energy, electricity and water consumption.

We show the results of a semi closed greenhouse located in South France. The climate is hot and dry climate. A pad system performs cooling and dehumidification.

Heating temperature set

Cooling temperature set : 26°C

semi closed greenhouse design

Inner climate

Results are temperature, relative humidity, hydric deficit and solar radiation in the greenhouse.

In this example, we show the results during a typical day of July.

The inner temperature is never above 26°C. Hydric deficit is between 2 and 4.5 g/ kg da.

graphic hydric deficit

Results also provides the external air flow, water flow and evapotranspiration.

Output of a semi-closed greenhouse designOutput of a semi-closed greenhouse design

During night time and morning, fans can blow the external air in the  greenhouse to dehumidify.

Then, during day time, pad cools the greenhouse.

Hortinergy shows also heating, electricity and water consumption. You have access to an annual overview,  a monthly synthesis and hourly data.

Annual overview of the energy consumption.

heating electricity and water
consumption per unit

Monthly synthesis of the energy consumption.

graphic monthly energy consumption

Hourly data of the energy consumption

hourly heating demand january

4. Model validation

Model is being under validation with 2 semi-closed greenhouses in France. They are located in CTIFL in Carquefou (wet climate) and Balandran (dry climate).

With Hortinergy, you can also design cannabis greenhouse with low energy cost and an optimal climate. You can simulate screen, closed greenhouse  and assimilation light

Hortinergy is an online paid software. You can choose your offer, create an account and then start your project.