Automatically adjusting light spectrum for optimal short term photosynthetic rate
Conference contribution, 2018

The use of light emitting diods (LEDs) as greenhouse illumination is increasingly common. When each LED color is individually dimmable both light spectrum and light intensity can be tuned, which opens up for optimisation of photosynthesis through automatic control of light quality and quantity. However, this requires a non-destructive biological growth signal that can be measured fast, remotely and preferably without interacting with the plants. A potential candidate signal is steady-state chlorophyll a fluorescence gain at 740 nm, defined as dF740/dq, i.e. the difference in fluorescence at 740 nm divided by the difference in incident light quanta caused by a (small) change in intensity of each individual LED color in the lamp (Ahlman et al., 2017). By automatically adjusting the spectrum, to aim for equal fluorescence gains for all LED colors (Wik et al., 2014), the instant photosynthetic rate can be optimised given a preset electric power input to the lamp. When implementing such a controller though, constraints on the spectral distribution are needed to minimise a negative impact on plant morphology.

Light Emitting Diode

optimal light spectrum

greenhouse illumination

chlorophyll fluorescence


Linnéa Ahlman

Chalmers, Electrical Engineering, Systems and control, Automatic Control

Daniel Bånkestad


Torsten Wik

Chalmers, Electrical Engineering, Systems and control, Automatic Control

First European Congress on Photosynthesis Research, ePS-1
Uppsala, Sweden,

Intelligent Light

The Swedish Foundation for Strategic Environmental Research (Mistra), 2012-01-01 -- 2015-12-31.

Driving Forces

Sustainable development

Subject Categories


Control Engineering

Other Electrical Engineering, Electronic Engineering, Information Engineering

Areas of Advance


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