LEDs from a Plant Scientist s Point of View

Transcription

1 LEDs from a Plant Scientist s Point of View Cary A. Mitchell Department of Horticulture & Landscape Architecture Purdue University cmitchel@purdue.edu 2012 International Meeting on Controlled Environment Agriculture Session 1: Light in Controlled Environments Cambridge University Downing College September 10, 2012

2 Why LEDs for Plants? (>20 years ago) Historical basis in the space program: Wisconsin and KSC Plants shown to grow under red LEDs only Plants grown under red + blue light usually do better Solid state = robust, long lived, low mass Waveband selectable Massive ballast and high voltage not required Promise to reduce ESM requirement for space life support Much interest in LED applications for CEA

3 LEDs popular for plant applications because photon-emitting surfaces are not hot waste heat is removed remote from photon emitters LEDs can be placed quite close to plant surfaces desired photon flux requires less electrical power inverse square law (Ι α d -2 ) is not a factor as for hot HID lamps luminous efficacy of LEDs is improving rapidly blue LEDS 49-50% efficient at nominal drive current 615-nm and 630-nm red LEDS 30% efficient at 350 ma 660-nm red LEDS 38% efficient at 350 ma potential for advances in light distribution system architecture, luminaires, shade avoidance, etc.

4 2007 ASHS Workshop on LEDs in Horticulture One One of the most highly read/cited Issues in ASHS literature John Sager

5 LEDs in Plant Photobiology Research Replace diffraction gratings Less need for broad-band sources, multiple filters Cutoff filters, heat filters, safelights challenge to get LEDs with desired peak emissions Bin selection, custom fabrication Will base of emission spectrum be as narrow as desired? May be an issue with long irradiance times or high irradiance responses Will cutoff filters have to be used with LEDs to determine contributions of different photoreceptors?

6 Normalized Photon Flux Image courtesy of A.J. Both, Rutgers University Blue LED Red LED Wavelength (nm)

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8 Phytochrome photoreversible forms overlapping absorption spectra

9 Image courtesy of Daedre Craig and Erik Runkle, Michigan State University

10 Folta & Childers, HortScience 43(7):

11 From work by Gioia Massa and Cary Mitchell, Purdue University Triton Pepper Overhead Lighted Intracanopy Lighted Plants look OK under red + blue LEDs

12 It is much easier to diagnose plant health under broadspectrum white light than under monochromatic light, such as for these Triton pepper plants suffering necrosis resulting from intumescence But under white light.

13 Image from work of Massa and Mitchell, Purdue University

14 Image from work of Celina Gomez and Cary Mitchell, Purdue University

15 Kim, H. et al Acta Hort. 711:

16 Examples of less efficient LEDs White LED = Blue LED + phosphor <50% as efficient as the blue LED) Screw-in LED lamp (probably 85% as efficient as hard-wired)

17 Contemporary Lighting Technologies for Plants Light-emitting diodes - waveband selectable Sulphur lamps - broader band than LEDs Plasma lamps - broader band than LEDs Induction lamps - broader band than LEDs

18 The importance of actively heat sinking high-output LEDs Critical for performance and lifespan Forced air for dense clusters of LEDs I watt Recirculating water for very high output/densities Makes light-emitting surfaces touchable Permits intracanopy distribution of light Overcomes mutual shading within foliar canopies Prevents premature senescence, abscission Enables higher photosynthetic productivity

19 Lightsicle design by ORBITEC Massa & Mitchell Purdue University

20 Printed-Circuit LED Light Engines 2.5 cm ORBITEC Light Engine 1 row of sixteen 440 nm blue 4 rows of sixteen 640 nm red 2 rows of ten 520 nm green 2 photodiodes

21 Intracanopy LEDs Overhead LEDs

22 Close-canopy lighting saves electrical energy because of close LED placement to plants Array design by ORBITEC From work by Lucie Poulet and Cary Mitchell, Purdue University

23 Smart LED Lighting for Major Reductions in Power and Energy Use for Plant Lighting in Space and for Terrestrial CEA Smart LED lighting systems could avoid lighting empty spaces prior to canopy closure Automation of plant detection and LED switching would save labor Smart lighting could be adapted for intracanopy (vertical) as well as overhead (horizontal) LED lighting systems Smart lighting could conserve considerable energy beyond just taking advantge of the unique properties of LEDs

24 Detection: How it works

25 Targeted lighting of widely spaced lettuce seedlings using close-canopy LED lighting Empty spaces between plants are not lighted

26 LED Applications for the Greenhouse Industry Technologies, protocols, best practices, guidelines For LED photoperiod lighting of ornamental crops To replace INC and CF lamps for night-interruption treatments To determine R/FR ratios for efficient flower induction/crop development For propagation and finishing of transplants Vegetable Ornamental End-of-day lighting Daylength-extension (DLI) lighting For supplemental lighting of vegetable crops Daily light integral (DLI) Off-season local production Energy savings Designing arrays, fixtures, luminaires Minimize blockage of sunlight Apply supplemental LED light efficiently and effectively

27 Image courtesy of Erik Runkle and Daedre Craig, Michigan State University

28 Images courtesy of Christopher Currey, Michael Ortiz, Wesley Randall, and Roberto Lopez, Purdue University Pelargonium Bullseye Scarlet HPS 100% R 85% R 70% R 15% B 30% B

29 Images courtesy of Ricardo Hernandez and Chieri Kubota, University of Arizona Solar PPF = 345 mmol m -2 s -1 LED PPF = 55 mmol m -2 s -1 Hernández & Kubota

30 Technology developed by ORBITEC Image from the work of C. Gomez and C. Mitchell, Purdue University

31 Intracanopy LED Lighting Towers Technology developed by ORBITEC Image from the work of C. Gomez and C. Mitchell, Purdue University

32 Point-of-View Summary LEDs will contribute to basic plant photobiology Narrow spectrum light Less cumbersome than classic photobiology equipment LEDs will be useful for whole-plant research Scalable, selectable waveband, high-output, long duration Translation to commercial application Systematic proof-of-concept testing required Multi-disciplinary teams required LEDS may not be best choice for all plant applications

33 Orbital Technologies Corporation Acknowledgements SCRILED Project Dr. A.J. Both, RU Mike Bourget, ORBITEC Daedre Craig, MSU Chris Currey, PU Celina Gomez, PU Ricardo Hernandez, UA Dr. Chieri Kubota, UA Dr. Roberto Lopez, PU Dr. Gioia Massa, PU Dr. Bob Morrow, ORBITEC Michael Ortiz, PU Lucie Poulet, PU Wesley Randall, PU Dr. Erik Runkle, MSU UA = MSU = PU = RU =