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For people that like to grow big plants, or that want to finish their outdoor plants indoors at the end of the season, there is even the possibility to upgrade the system with another 8U. This will put out a whopping 1700 µmol/(m˛s) at close distance, providing a high quality level up to 35 cm (25 cm at short days) and a good quality level up to 50 cm (35 cm at short days).
Measuring light energy using the proper unit and in relation to temperature
The unit that is most commonly used by our industry to measure light energy is lumen or luminous flux. This unit however, is used to measure the light that is visible to the human eye and does not exactly correspond to the spectrum of light energy used by plants. For agricultural purpose it’s best to measure instantaneous light level as the number of micromoles of photons in the “PAR” spectrum* that reach one square meter each second µmol/(m˛s), because this unit quantifies light energy used in photosynthesis. We can also quantify how much PAR light reaches a square meter during a full 24-hour period in units of moles of PAR light that reach one square meter over the course of a day mol/(m˛d) or moles/day. If we think of instantaneous light level µmol/(m˛s) as the number of drips of water (light) falling on one square meter each second, then daily light integral moles/day would be a bucket holding the water (light) that has accumulated over the entire day.
Aside light, all kinds of artificial light sources radiate heat as well, so its important to know the light energy in relation to temperature in order to give a good impression of how much of the light is actually usable, fig 3 shows the light energy in relation to the temperature of the illuminated surface using the Garudatm light system equipped with different light sources.
* The range of 400-700 nm wavelengths, termed “photosynthetically active radiation” or “PAR”.
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Fig. 1 Fig. 2 Fig. 3
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