Supplementary lighting

Principle

Supplementary lighting is used to increase the total daily light.  Light intensity, spectrum and duration affect several plant growth and processes. There are several reasons for providing supplementary lighting:

• When natural light is scarce, it helps to increase yield and production quality such as tomato …
• Supplementary lighting is also applied for day length control in ornamental crops.

With Hortinergy, you have two types of lighting systems : the first one is called “High Pressure Sodium” (HPS) and the second one “Light Emitting Diode” (LED).

LED light :

Pros :

-long life expectancy

-almost no excess heat, which allows it to be placed very close to plants

-low operating/maintenance cost

-high yield per Watt

Cons :

-high initial cost

HPS light :

Pros :

-low initial cost

Cons :

-the high intensity of light from this lighting system generates a lot of heat

-additional cooling system is needed

-high operating cost

Input parameters with Hortinergy

Input parameters are:

• LED and HPS specification: lighting intensity, efficiency…
• Regulation setpoints:
  • Day Light Integral (DLI) and minimum hours of ‘’night’’ per day,
  • or fixed monthly schedule above which solar radiation intensity lighting is switched off.

You first define you lighting system:

Then you define the regulation settings:

Results

Hortinergy simulates your project during one year like a virtual greenhouse. Outputs are :

• Solar radiation transmitted by the transparent cover and reaching canopy,
• Assimilation lighting required according to regulation setpoints (mol/m²/day):
• Electricity consumption,
• Impact on the inner climate and energy consumption: heating, cooling, dehumidification.

The reports are:

• a pdf document with typical days and monthly summary tables
• an Excel file with hourly data for deeper analysis.

Solar radiation reaching canopy and additional assimilation lighting required

Hortinergy simulates on hourly basis the solar radiation reaching canopy and the additional assimilation lighting required to reach the DLI.

The example below shows a monthly summary.

Impact on the inner climate and energy consumption (heating, cooling, dehumidification)

Hortinergy models the impact of assimilation lighting on the inner climate and energy consumption (heating, cooling, dehumidification).

The example below shows the crop transpiration and a higher inner temperature when HPS assimilation lighting is switched on from to 9 to 11 AM and 4 to 9 PM to reach DLI.

Electricity consumption and expenditures

Hortinergy shows also the electricity consumption and expenditures.