Lighting the future of horticulture:
Energy saving and spectral manipulation
Dr Phillip Davis
Horticulture Technologies Event. Dublin 4th May 2017
Energy efficiency of different lighting systems
HPS treatment
Philips LED top light
600W
Efficacy 1.92 µmol /J
190W
Efficacy 2.71 µmol /J
Assuming 200 µmol m-2 s-1 is
required to grow a crop over
a 10m2 area.
Assuming 200 µmol m-2 s-1 is
required to grow a crop over
a 10m2 area.
Number of light required
=200/(600*1.92)*10
= 1.73 lamps per 10m2
Number of light required
=200/(190*2.73)*10
= 3.86 lamps per 10m2
Total power of 1041W
Total power 733W
30% Electrical
energy saving
Efficacy data from AHDB CP139 project and Philips data sheets
Not all LEDs are equal
Lamp
HPS
LED 1
LED 2
LED 3
LED 4
LED 5
Plasma
Efficacy / µmol m-2 s-1
1.92
1.44
1.27
2.43
2.71
2.56
1.16
Efficacy data from AHDB CP139 project
1600
Tomato yields
1400
LED/LED + diffuse / Comp. 9
LED/LED / Comp. 10
HPS / Comp. 11
Hybrid / Comp. 12
Winter production
Summer production
1200
1000
Number of fruit
30
25
800
600
Cummulative yield / kgm-2
400
20
2.4
2.4
15
2.4
200
0
3
4.2
3
3.6
3
3.6
49 50 51 52 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Week of year
10
4.8
4.8
5
4.2
0
49 50 51 52 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Week of year
More light - more growth
Petunia 35 days after sowing
100 µmol m-2 s-1
200 µmol m-2 s-1
280 µmol m-2 s-1
But also more cost!
360 µmol m-2 s-1
…but not always a better result
100 µmol m-2 s-1
200 µmol m-2 s-1
280 µmol m-2 s-1
360 µmol m-2 s-1
Pepper plants grow shorter as the
light intensity increases
100 µmol m-2 s-1
200 µmol m-2 s-1
360 µmol m-2 s-1
Light controls more than just photosynthesis
Movie by Prof. R Hangarter
http://plantsinmotion.bio.indiana.edu/plantmotion/earlygrowth/photomorph/photomorph.html
How plants sense light quality
Blue
Solar
light
responses
Red
UVB
lightSpectrum
responses
response
Relativeresponse
orRelative
Absorptanceor
Absorptance
1.0
1.0
1.0
0.8
0.8
0.8
0.6
0.6
0.6
0.4
0.4
0.4
0.2
0.2
0.2
0.0
0.0
0.0
250
250 300
300 350
350 400
400 450
450 500
500 550
550 600
600 650
650 700
700 750
750 800
800
250
300
350
400
450
500
550
600
650
700
750
800
Wavelength
Wavelength /// nm
nm
Wavelength
nm
Secondary metabolism
350
[Chlorophyll] (μmol m-2)
300
250
200
150
100
50
0
0
20
40
60
% Blue in spectra
80
100
Leaf morphology
100% RED
60% BLUE
Red: blue effects on leaf morphology
100% red
11% blue
30% blue
60% blue
Increasing blue percentage
100% blue
Red: blue effects on plant height
Increasing blue percentage
Far-red effects on plant height
FR = 0
µmol m-2 s-1
FR = 15
µmol m-2 s-1
Increasing far-red intensity
FR = 30
µmol m-2 s-1
Far-red effects on plant height
FR = 30
µmol m-2 s-1
FR = 15
µmol m-2 s-1
FR = 0
µmol m-2 s-1
FR = 48
µmol m-2 s-1
Far-red effects on leaf morphology
How do we make use of this information?
FR = 0 µmol m-2 s-1
FR = 18 µmol m-2 s-1
FR = 24 µmol m-2 s-1
Increasing far-red intensity
FR = 40 µmol m-2 s-1
Modelling plant light responses
110
𝐿 = 𝐿𝐷 − (𝑅𝐵 − 𝑅𝐺 + 𝑅𝑅 − 𝑅𝐹𝑅 )
(2)
𝑟
𝑅𝑅 = 𝑏 ∗ 1 − 𝑒 (−𝛽 𝑏 )
(3)
120
𝑅𝐹𝑅 = 𝑐 ∗ 𝐹𝑅
𝑅𝐺 = 𝑑 ∗ 𝐺
100
100
Leaf length / mm
𝑅𝐵 = 𝑎 ∗ 1 − 𝑒
𝑏
𝑎
(−𝛼 )
Actual length / mm
where
(1)
90
80
70
60
(4)
50
y = 0.99x (5)
R² = 0.8897
40
30
0
80
20
40
% blue
60
40
20
0
0
20
100
90
y = 1.0715x
40
60
Predicted length / mm
80
100
60
80
100
Effect of blue light on Tomato fresh mass
18
16
Fresh mass / g
14
12
10
8
6
4
2
0
0
20
40
% Blue
60
80
100
Effect of blue light on Tomato leaf area
350
300
Leaf area / cm2
250
200
150
100
50
0
0
20
40
% Blue
60
80
100
Leaf area strongly influences growth rate
25
Fresh mass / g
We
can design light treatments to
20
y = 0.0693x - 4.3965
R² = 0.8473
control morphology
and influence their
15
growth rate.
10
LEDs5 can help optimise many aspects of crop
production
0
0
50
100
150
200
250
2
Leaf area / cm
300
350
DL extensi
pplemental
Unlit
Improving propagation
0% BLUE
(100% RED)
9% BLUE
11% BLUE
30% BLUE
Blue light stresses cuttings
60% BLUE
Blue light reduces cutting survival
100
90
80
% survival
70
60
50
40
30
20
10
0
0
20
40
60
% Blue
80
100
120
But survival does not mean cuttings will root.
100
90
Clematis
80
% rooting
70
60
Iberis
50
40
Santolina
30
20
10
0
0
20
40
% blue
60
Influence of far:red on rooting
Pre-treatments
Supplemental
Santolina
Unlit
Clematis data
80
Treatments
T4
15%B
Survival correced % rooted
70
y = -2.6822x + 59.969
R² = 0.992
60
50
40
30
20
10
0
R3
15%B
+FR
0
5
10
Far-red / µmol m-2 s-1
15
20
Chrysanthemums showed no negative responses
to far-red so again there are differences in
sensitivity between species.
Pre-treatments
Benefits of lighting
mother stock
Supplemental
lighting
Supplemental
No light
Unlit
Day length
extension lighting
DL extension
CuttingsT1lit
with0%
0% B
BLUE
(100% RED)
Low stress
T4
9%B
Survival and rooting poor if preexcision lighting inappropriate
Benefits of lighting mother stock
Supplemental
lighting
No light
Day length
extension lighting
Cutting lit
with
60% BLUE
High stress
Survival and rooting high if pre- excision lighting
appropriate even under stressed conditions
Flowering time
600
No. flowers per 6 pack
B –5th March 2015
FR = 18
FR = 24
FR = 40
PR11C
PR12B
400
PR12C
300
200
100
0
23/02/2015
05/03/2015
15/03/2015
Date
600
Number of flowers per sixpack
FR = 0
PR11B
500
500
400
300
200
100
0
0
10
20
30
Far-red intensity / µmol m-2 s-1
40
50
Pest monitoring under LED ligths
Standard Yellow sticky
Pest performance under LED lights
Further information
• CP125 reports available at the following link
https://horticulture.ahdb.org.uk/project/understandingcrop-and-pest-responses-led-lighting-maximisehorticultural-crop-quality-and
• CP139 report available at the following link
https://horticulture.ahdb.org.uk/project/knowledgetransfer-commercial-review-lighting-systems-ukhorticulture
• AHDB Technical Guides are available at the following link
https://horticulture.ahdb.org.uk/led-principles-andpractice
• LED4CROPS website - http://www.led4crops.co.uk/
Thanks to…
• Dr Rhydian Beynon-Davies
• Mr Adam Omerod
• Dr Martin McPherson