LED Research WUR Horticulture:
Results & Bottlenecks
Tom Dueck, Wageningen UR Glastuinbouw
6 februari 2014
9960 ha horticulture in the Netherlands 3100 ha with artificial lighting
Why LEDs in horticulture?
Insufficient development in HPS
HPS – more light?
●More light hours: 1% more light -> 1% more production
● Higher light intensities: 1% more light -> 1.7% more production
Result: more light ~ more (surplus)heat
Are LEDs the answer? ...no radiative heat, higher efficiency, longer life, can be dimmed, specific wave lengths...
First tomatoes under LEDs
Toplighting in rose, tomato, pepper:
which problems encountered?
Intensity too low – had to be supplemented
Efficiency too low - (sometimes) lower than HPS
Expectations for production increases not realized
Insufficient radiative heat
Insufficient radiative heat (necessary for truss
and leaf initiation)
12 0 12 0 12
12
14
16
18
20
22
24
26
28
30[oC] LED-top
time
12 0 12 0 12
12
14
16
18
20
22
24
26
28
30[oC] HPS
time
air temp.
plant temp.
Leaf T < Air T at night Leaf T ~ Air T night and day
But why (LED)lighting?
Produce year-round crops
GROW LIGHT: increase production
STEERING LIGHT: increase quality
steer/influence crop (form, morphology, flowering)
Zonlight (spectrum)
Stralin
g Golflengte Opmerking
UV-C << 280 nm Komt niet aan op de aarde
UV-B 280 - 315 nm > 300 nm komt aan op aarde
UV-A 315 - 400 nm Gevaarlijke straling in de zon
VIS 380 - 780 nm
(400 – 700)
Licht ! Zichtbaar voor menselijk oog
paars, blauw, groen, geel, oranje,
rood
IR-A 780 - 1.400 nm Nabij infrarood ( N I R )
IR-B 1.400 - 3.000 nm
IR-C 3.000 - 100.000 Ver infrarood ( V I R )
Which wave lengths doe a plant see?
Average plant sensitivity(McCree, 1972)
PAR
red Far red blue
400 500 600 700 Wave length (nm)
Grow light – progression, development in
tomato cultivation
2007 – toplight, air-cooled, water-cooled
2009-2012 – interlight, in hybrid systems
2013 - hybrid systems with LED interlight and/or LED toplight
Consensus: hybrid system
HPS + interlight (LED)
Advantages:
Interlight ~ 10% more efficient than HPS
Light distribution over larger leaf area
Less (HPS) light in top of crop -> less excess heat, with sufficient radiative heat for truss and leaf
More hours (LED) lighting possible in warm weather (spring)
Intermittent lighting possible (on/off)
Optimal use of light and hybrid lighting
Application of hybrid lighting
Tune assimilation light to crop requirement
Calculate light requirement according to crop (fruit) load in time
Light requirement = sun light + lamp light
● Sunlight is known (last 5 next 3 days)
● Lamp light – number of extra hours necessary is then known as well
HPS lighting out at 200 W radiation
LED lighting out at 400 W radiation (longer use in spring is possible)
Light strategy
0
5
10
15
20
25
0
200
400
600
800
1000
1200
1400
1600
1800
2000
16/10 30/10 13/11 27/11 11/12 25/12 8/1 22/1 5/2 19/2 4/3 18/3 1/4 15/4 29/4
Mo
l/(m
².d
ag
)
Jo
ule
/(cm
².d
ag
)
Globale straling in J/cm².dag Gewenste lichtsom mol/(m².dag)
Lichtsom mol/(m².dag) (voortschrijdend gemiddelde van 7 dagen)
PARsom + SON-T geinstalleerd+ LED geinstalleerd per dag
Belichting
Next Generation Lighting with Diffuse Light
Crop duration 1 whole year HPS 83.6 kg / 100% Hybr LED 87.2 kg / +4.3% Hybr Dir 84.9 kg / +1.6% Hybr Diff 89.1 kg / +6.6%
Light efficiency
PAR sum (mol m-2)
Prod. (kg m-2)
Efficiency (kg kmol-1)
HPS 6671 83.6 12.5
Dir hybr 6727 84.9 12.6
Dir LED 7107 87.2 12.3
Diff hybr 6958 89.1 12.8
Efficiency: Diff hybr > Dir hybr > Dir HPS > Dir LED
0
10
20
30
40
50
60
70
80
90
100
0 1 2 3 4 5 6 7 8
Cu
mu
lati
eve
pro
du
ctie
(kg
m-2
)
Cumulatieve PARsom (kmol m-2)
Diff hybr
Dir hybr
Dir LED
Dir SONT
Situation: Interlighting LEDs for production
Good energy savings realised (ca. 30%)
Production more or less equal to practice
Light distribution sub-optimal
Management strategy promising for crops like tomato, but application requires practice
Current research: combination of hybrid lighting and diffuse glass (increased utilization of light – sun light and assimilation light)
Situation re: use of LEDs in general
Cost price still too high
Production (growth) increase still too low
Light interception higher than HPS (ca. 7% vs 3%)
Electrical connection often 230V vs 400V
Replacement of individual LEDs vs whole module
LED efficiencies (ca. 2007-2014)
Approximate Interlighting (µmol/W)
TopLEDs (µmol/W)
ca. 2007 2014 ca. 2007 2014
Red 1.6 –> 1.9 1.6 -> 2.4
Blue 1.4 -> 1.6 1.4 –> 2.0
System r/b 1.6 -> 1.9 1.6 –> 2.3
System r/b/ + w/g 2.0
HPS 1.8 1.8
Energy thrifty Chrysanthemum
Aim: Save 30% electrical energy
Use of efficient LEDs
Lighting ~ plant requirements
Switching on/off with LEDs
Lighting ~ crop stage
Spectral influences on Chrysanthemum
Stimulates elongation (in shade of a crop)
80red:20blue HPS Plasma
Van Ieperen et al. 2010
Setup in greenhouses
SON-T Hybride LED
Spectrum
0
0.5
1
1.5
2
2.5
3
3.5
400 500 600 700 800 900
Lich
tin
ten
site
it (
µm
ol/
m2
/nm
)
Golflengte (nm)
SONT
0
0.5
1
1.5
2
2.5
3
3.5
400 500 600 700 800 900
Lich
tin
ten
site
it (
µm
ol/
m2
/nm
)
Golflengte (nm)
hybride
0
0.5
1
1.5
2
2.5
3
3.5
400 500 600 700 800 900
Lich
tin
ten
site
it (
µm
ol/
m2
/nm
)
Golflengte (nm)
LED
HPS hybrid LED
Results long day (LD) period
Lighting ~ plant requirements (LD):
7 days: less light used for 3 to 6 h per day
12% less light used
Proportion lamp light ~ total light:
● HPS 79%
● Hybrid 76%
● LED 76%
Transition to short day (SD):
Same development/growth after 15 days in all 3 crops
Results: plant length end of LD
LED: 0.9 cm higher than hybrid and 0.7 cm higher than HPS
26
27
28
29
SONT hybride LED
Len
gte
(cm
)
Gemiddelde lengte 14 rassen (n=168)
27.6 27.4 28.3 *
Light quality & LEDs
Mostly red (95%) and blue (5%), combinations with far red are being explored
Is green light necessary in supplementary lighting?
Effects other colors ?? especially on vegetables
But, many possibilities in ornamentals
Quality, not intensity (1-20 µmol m-2 s-1)
Distribution in space and time important
Light quality influences
Effect UV – plants harden, production of secundary metabolites (eg herbs)
Light quality influences
Effect UV – plants harden, production of secundary metabolites (eg herbs)
Effect far red/red ratio
● Flowering
●Morphology
● Stem elongation (longer internodes)
● Leaf area, orientation
Light quality influences
Effect UV – plants harden, production of secundary metabolites (eg herbs)
Effect far red/red ratio
● Flowering
●Morphology
● Stem elongation (longer internodes)
● Leaf area, orientation
Production of secundary metabolites
Influence on plant resilience?
Inhibition of plant disease?
Assimilation lighting without sun light
HPS, flat,
Horizontal leaf,
good light-
interception
LED: curved leaf,
shiny, moderate
light-interception
Measuring photosynthetic efficiency
Snel & Driever 2010
Spectral efficiency in rose
Cv Akito
Cv Prestige
10-30% higher efficiency with red light in Prestige
Driever & Snel 2012
Driever & Verkerke 2010
LED light on trusses
increases vitamin C
Use of steer light: quality and tomato
Supplementary LED light Increases vitamin C content in tomato
Red light at night = less mildew spores
Suthaparan 2009
Local leaf reaction systemic resistence
• Biotrophic organisms: mildew, bacteria, virusses.
• Salicylic acid -> (SAR)
• Also effects of light or P-fertilizers, amino acids.
Hofland et al. 2012-2103
Future research focus on:
Crop specific responses
Optimal growth of other crops under LEDs
Dynamic lighting
● During day
● During crop
Feedback from plant
● Intensity
● Spectrum
Innovation Demonstration Centre LED
Future for LEDs (2020)?
Lighting systems will include:
● Lower cost price
● Replacable individual LEDs
● Location of light (LEDs) in the crop
● Optimized light distribution
● Larger array of colours
● Also UV, far red, etc
● Varying wave lengths and intensity throughout the day
Wageningen UR
Glastuinbouw
With thanks to my colleagues:
Arie de Gelder
Jan Janse
Wouter Verkerke
Jan Snel
Filip van Noort
Jantineke Hofland