An Automatic Control System of Photosynthetic Photon Flux

Density for LED- Low light Irradiation Storage

of Green Plants

SHRUTHI.K.MOHAN120916017 EMAL

CONTENTS• Introduction• Light & Plant growth• Benefits of LED• LED LLI storage system under

automatic PPFD control• Storage experiment• Results • Conclusion• Inference

LIGHT AND PLANT GROWTH• Natural sunlight is the cheapest source available, but for horticulture it is not always available in sufficient quantities. • Use of artificial light has become very common in order to increase production and quality•The only part of the global radiation spectrum which can be used by a plant for its photosynthesis is between 400-700 nm, this is called the PAR-light •Photosynthesis is a photochemical process. •Light energyis used to form sugars from carbon dioxide gas (CO2and water, which are taken up by leaves and roots).•Plants have a completely different sensitivity to light colors than the human eye

BENEFITS OF LED

LED LLI STORAGE SYSTEM UNDER AUTOMATIC PPFD CONTROL•Light irradiation during storage has been shown to prolong storability.

•A light intensity at which photosynthetic rate is maintained at zero is needed for suppressing changes in dry weight and preserving quality in seedlings

•Light compensation point determined by measuring the CO2 exchange rate of plants at the storage temperature under different PPFDS.

•Green plants acclimatize to low light conditions in a few days leading to gradual reduction in the light compensation point.

•LED LLI storage system capable of irradiating red light only /red and blue mixed light

•PPFD is controlled automatically by a PID controller

•PID controller maintains the CO2 exchange rate at zero.

• Green plants stored in>> acryl resin base+light diffusing film+ Aluminium foil

• Mixed gas composed of N2 and O2 was supplied• Flow rate controlled by flow controller

• Voltage controlled by a PID controller by controlling difference between Cin and Cout.

• Infrared CO2 analyser and a dehumidifier

• Light compensation point is a PPFD level where Cin – Cout = 0

LED array Automatic PPFD control and PID parameters

• Vout of PID determined by difference between Vset (desired Cout) and feed back signal Vfdb(current Cout).

• Vact was transmitted to a Dc power supply.

• Gain was determined (Vact*3.5) so that max PPFD from red light is achieved.

o PPFD fluctuations were :

*increased by increasing proportional constant

*increased by decreasing Td

o Time required for CO2 to reach stable level increased with decreasing Ti

STORAGE EXPERIMENT

• 9 seedlings for each lighting treatment in separate nine plug trays.• Sub irrigated for 1 hour before being placed• 4 different lighting treatments

* fixed red light irradiation

*PID controlled red light irradiation(RC)

*RC with fixed blue light irradiation(RCB0.2)

* RCB1.0• Dry weight of aerial, subterranean parts and leaf area per seedling were

measured

RESULTS

CONCLUSION

• In RC treatments the dry weightloss was seen

• PID control contributed to the suppression of dry weight change.

• Addition of a low percentage of blue light reduced the PPFD requires for suppressing the dry weight change.

• Positive effects on leaf morphological appearence

REFERENCES• Philips LED lighting in horticulture (2012) Available at:

http://www.usa.lighting.philips.com/pwc_li/main/shared/assets/downloads/pdf/horticulture/leaflets/general-booklet-philips-led-lighting-in-horticulture-USA.pdf (Accessed: 2 October 2012)

• J. S. Wu, J. Y. Hu, Q. Z. Zhou et al, “Influence of illumination supplement used a LED light on growth and photosynthesis of Radish,”J. Northern Horticulture, vol. 10, pp. 30-33, 2009.

• D. A. Steigerwald, J. C. Bhat, D. Collins, R. M. Fletcher, M. O. Holcomb, M. J. Ludowise, P. S. Martin and S. L. Rudaz, "Illumination with solid state lighting technology," IEEE Journal on Selected Topics in Quantum Electronics, vol. 8, pp. 310-320, March-April 2002. 2002.

• M. Dorais and A. Gosselin, "Physiological response of greenhouse vegetable crops to supplemental lighting," Acta Horticulturae, vol. 580, pp. 59-67, 2002.