ASGSB 2003 Annual Meeting Abstracts
OPTIMIZING LED LIGHTING STRATEGIES FOR ALS-RELATED CROPS.
G.D. Massa1, J.A. Montgomery1, J.M. Badger2,
G.T. Chiu2 and C.A. Mitchell1 1Dept. of
Horticulture & Landscape Architecture, and 2 Mechanical
Engineering, Purdue Univ., West Lafayette, IN.
Providing adequate illumination is one of the challenges facing crop growth in
a closed environment on a planetary surface or in a space station.
Intracanopy (IC) and close-canopy (CC) crop-lighting systems are being
developed using narrow-spectrum light-emitting diodes (LEDs). Operation at
low power permits LEDs to be arrayed close to and/or within foliar canopies
without overheating or scorching plant tissues. Vertical LED strips will
switch on in sectors from the bottom up, keeping pace with increases in stand
height of upright-growing crops without lighting empty headspace. Horizontal
LED panels will be designed to switch on in concentric circles above each
seedling of compact rosette crops such as lettuce. These panels will be
maintained at constant, close distance from leaf surfaces during crop
development. For vertical arrays, parallel rows of alternating red and blue
LEDs will be mounted closely along thin, printed-circuit plastic strips,
allowing a uniform blend of photon output from each array.
control will be achieved by establishing a given ratio of photon flux from red
and blue LEDs, and intensity will be controlled by varying the input voltage
applied to each LED type. For vertical IC LED strips, control signals for
on-off switching and hue and intensity control will be multiplexed to any
number of “lightcicles” hanging in a given growth compartment for
upright-growing crops such as soybean, basil, or tomato. For horizontal CC
LED panels, hue and intensity controls will be applied in expanding,
concentric circles as seedlings expand laterally. Both types of LED arrays
will be designed for ease of removal prior to crop harvest and replanting, a
procedure that could be readily automated. Measured crop responses to LED IC
and/or CC lighting include edible yield, cropping time, harvest index, edible
yield rate, crop quantum yield, electrical energy conversion efficiency, and
real-time photosynthetic gas-exchange rate for small crop stands expressed on
a growth area and/or growth-volume basis.
(Supported by NASA: NAG5-12686.)
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