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

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28

30[oC] LED-top

time

12 0 12 0 12

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14

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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

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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

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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

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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

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0.5

1

1.5

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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