Controlled Environment Agriculture

Cycloptics HID Chamber Lighting

A High Intensity Discharge (HID) luminaire has many parts including: a ballast, a lamp (aka bulb), a reflector, and a housing (to hold it all together).  Light energy that is useful for growing plants is lost on its’ journey from the power lines to the plant in the first three luminaire components mentioned.  An older-style magnetic ballast may use 10-15% of the nominal wattage of the lamp.  Newer electronic ballasts use an average of 5% of the nominal wattage of the lamp.  The lamp’s quantum output will decay over time.  Ballast losses and lamp losses are fairly standard and predictable.  The most variable and thus most important part of the luminaire is the reflector.  Research done by the CEA program at Cornell has demonstrated the variability of useful light output that is caused by the design of the reflector (Link to luminaire comparison page).   In that study, actual light output of commercially available 400W luminaires was used to calculate how many luminaires would be required for an approximately 1 acre greenhouse with a target supplemental light intensity of 50 umol m-2 s-1.  A dramatic difference in the number of luminaires required (676 compared to 840) demonstrated the importance of reflector design.

Cycloptics is a company based in Ohio that has applied a unique concept to greenhouse lighting reflectors.  They have developed reflectors such that photosynthetically active radiation (PAR) light that exits the lamp strikes the reflector and is directed out of the luminaire and down onto the plants.  This is called beam shaping.  Other reflectors on the market are not as efficient in directing light out of the luminaire and much PAR light is lost because it bounces multiple times before exiting the reflector.  Equally bad, other reflectors cause the light to be redirected back through the lamp before exiting the luminaire, shortening the life of the lamp.

The lamp used in the Cycloptics system is a 315 Watt Metal Halide lamp by the Philips company.  The mixture of salts inside the lamp have been custom designed such that there is more blue light and more red light than a typical metal halide lamp.  The efficacy of this 315 W lamp is similar to that of the most efficient 400 W HPS lamps sold by other companies.

Growth Chamber Lighting

CEA program researcher Dr. David de Villiers has performed light output measurements from plant growth chamber lighting.  Three different light delivery systems were compared: T12 fluorescent (traditional 1.5” bulbs 8ft. long), T5 fluorescent and the Cycloptics luminare.  He also measured actual energy going into each light delivery system to determine the received light efficacy at the plant level.  In addition, he grew several different types of plants (monocots and eudicots) under each light delivery system to ensure that there is nothing about the luminaire that causes any abnormal growth or development.  As expected, the Cycloptics luminare was about 1.5 times as efficacious on a umol s-1 W-1 as the T5 fluorescents (the more efficient of the two fluorescent light delivery systems).  The T5 system provided 4 times more per watt compared to the T12 system and the Cycloptics system provided 5.5-6.5 times more PAR per watt compared to the T12 system.

This work was presented at the ISHS Conference in Greece in 2011. The Conference Preecedings were published in Acta Horticulturae in 2012.

de Villiers, D.S., Albright, L.D., and Tuck, R. 2012. Next-generation energy-efficient, uniform supplemental lighting for closed-system plant production. Acta Horticulturae (ISHS) 952:463-470.

Download: Energy efficient lighting for growth chambers

Greenhouse Lighting - Light Stalk

The Light Stalk HID lighting system has been designed to produce uniform, rectangular shaped beam output patterns to avoid wasting energy lighting walkways or allowing light to spill into other areas where plants are not in production (ex. Outside the edges of the crop.). The initial application is expected to be in research and teaching greenhouses where crop canopies are seldom uniform and benches may be partly empty for periods between experiments.  The rectangular shaped uniform (coefficient of variation 0.05), illumination plane is 3 feet x 6 feet, with luminaires mounted 3.5 feet above plant canopy (0.91m x 1.83m 1.07m above canopy) and will achieve a uniform 280 umol per square meter per second .  Moving the light stalk up or down will provide a larger (with less quantum flux) or smaller (with greater quantum flux) rectangle.  Currently the light stalk reflectors are being produced and their performance will be tested at Cornell in the same fashion as the growth chamber lighting was evaluated.

This work was presented at the ISHS LightSym Conference in the Netherlands in October 2012.

Albright, L.D., D.S. de Villiers, and R. Tuck. 2012. Energy-efficient, uniform, supplemental plant lighting for research greenhouses. Acta Horticulturae 956:99-106.

Download: Energy efficient lighting for research greenhouses