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Pieter de Visser& Gerhard Buck-Sorlin Wageningen UR Greenhouse Horticulture * P.O. Box 430, 6700 AK Wageningen, The Netherlands Simulation of light absorption.

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Presentation on theme: "Pieter de Visser& Gerhard Buck-Sorlin Wageningen UR Greenhouse Horticulture * P.O. Box 430, 6700 AK Wageningen, The Netherlands Simulation of light absorption."— Presentation transcript:

1 Pieter de Visser& Gerhard Buck-Sorlin Wageningen UR Greenhouse Horticulture * P.O. Box 430, 6700 AK Wageningen, The Netherlands Simulation of light absorption and photosynthesis in a greenhouse crop: effect of light node types & shaders

2 Evolution of lighting systems

3 Observed light distribution

4 Why studying this? improve light interception, being driver of production even only 1% yield increase is appreciated: fine-tuning check stakeholders ideas about light climate with model efficient lighting strategies reduce energy use

5 Modelling platform: GroIMP

6 Main model parts: Inversed path tracer model from GroIMP 3D mockup in XL of existing crop Photosynthesis (Kim & Lieth, 2004) Iight distribution Iight absorption/reflection/transmission ?

7 Design of the virtual greenhouse

8 Measuring light with virtual sensors Sensor types perceiving sphere with radius r hemispheric view (upper or upper/lower hemisphere) absorbing planar area amount of absorbed light any planar object (e.g. leaf) can measure its light absorption directly

9 LEN i LEN i+1 RU (divergence) RL LEN DIAM RH (tilting) L1 L2 L3 L4 L5 L6 L7 L1 L2 L3 L4 L5 L6 L7 T RL (hanging downof leaflets)

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12 SONT + LED at Improvement Centre, Bleiswijk, NL

13 Shader parameterization: a virtual set-up

14 Light types Point light Directional light Spotlight

15 SONT HPS-lamps Measured light distribution (two vertical planes, perpendicular): max. opening angle 140°

16 New class SONT: extension of PointLight class of GroIMP Directional distribution of emitted light incorporated into the rendering process by overwriting method getDensityAt() (computes for a given direction probability density of choosing this direction.): 1) Transformation of direction vector ω = (x,y,z), |ω| = 1 into a polar form, where polar angles are: Model of a SON-T lamp φ = atan2 where atan2 = variant of arcus tangens function ϕ = atan2(y,x) θ = acos(z) azimuth[-π < ϕ < π] elevation [-π < θ < π]

17 2) Angles ϕ and θ used as indices for the lookup table λ of luminosity values. λ is discretized as an array of 36 by 180 values, for ϕ, respectively θ. Mapping the values of ϕ and θ to λ and obtaining lower and higher indices for the two angles: float a = (phi+PI) * 18 / PI; float b = (theta+PI) * 90 / PI; int phi0 = (int) a % 36; int phi1 = (phi0+1) % 36; int theta0 = (int) b; int theta1 = min(179, theta0+1);

18 3) Bilinear interpolation to weight four drawn array values smoothing of spatial light distribution: float wa = 1 - (a-floor(a)); float wb = 1 - (b-floor(b)); Obtaining the array values from the lookup table: float d00 = li[phi0][theta0]; float d01 = li[phi0][theta1]; float d10 = li[phi1][theta0]; float d11 = li[phi1][theta1]; float w00 = wa*wb; float w01 = wa*(1-wb); float w10 = (1-wa)*wb; float w11 = (1-wa)*(1-wb);

19 Multiplication of weighting factors with read luminosity values to obtain probability density of the ray for the given direction: float density = w00*d00 + w01*d01 + w10*d10 + w11*d11;

20 Visualisation of light distribution of a SON-T assimilation lamp. Next step: implementation of such a lamp as a new light source in the modelling environment

21 Implementation of a Hortilux GreenPower SON-T lamp First version (improper interpolation between array values) Update: bilinear interpolation between array values; 3 different lamp angles to a reflecting sheet

22 Grid of 21 SON-T broad beam reflector lamps reflection screen at increasing distance below the lamps 0.5 m

23 Quantifying light distribution in row crop: light type

24 Effect light type on distribution light:SPOTDIRECTSPOTDIRECT wall height (m) South wall: fraction 40% unshaded 34%16%4% North wall:41%38%13%15% West wall:41%46%13%20% East wall:36%38%13%29% Plant shading is more stable at use of spot lights:

25 How many buffer rows?

26 Validation of light module of tomato model Check poster on comparison of two light models of tomato

27 Lighting strategies: 1.change SON-T position (horizontal & vertical) & angle 2.LED position above or between crop rows 3.path width between rows (at same plant density) 4.SON-T distribution wide vs. deep reflector 5.reflection via screen increases light use efficiency? 6.Effect lamp colour

28 Lamp light direction Angle from vertical Light absorbed (umol s -1 ) Light level floor (umol s -1 m -2 ) 22°

29 Lamp type, height; crop structure Scenario:Absorbed light % of input Light level on floor (umol m -2 s -1 ) Default Wide reflector Lamp height -1m Path width +0.4m Idem, plants+24%

30 Testing opening angle

31 Effect opening angle ( type reflector): Available light in scene and crop absorption at 27 Phyto: (umol in total) Opening angle:SONT (Phyto)very smallsmallwide deep Light in (3) Light in (27) CropAbs % of IN68% 67%68%65%

32 LED scenarios: Relation to LED position in the crop: in path, in row, height Wireframe in sideview Virtual crop White: rows of virtual sensors

33 Vertical light distribution depending on LED position N.B.: data averaged from 2 rows incl. path

34 Light absorption in crop: LED positioning in row Height2.5m3.5mtop (4.6m) Leaf86.1% Young fr Ripe fr Stems Total: Roof Floor no aging: RUE (rel.)

35 Light absorption in crop: LED positioning in path Height2.5m3.5mtop (4.6m) (row) Leaf86.0% Young fr Ripe fr Stems Total: Roof Floor RUE (rel.)

36 Conclusions: 1.Type of reflector hardly affects light utilization 2.Row structure (path width) has some impact on light use 3.LED positioning strongly affects light use 4.GroIMP platform suitable for this approach

37 Next steps and outlook: 1.Further optimize lighting strategy incl. screens 2.Include wavebands in light source and photosynthesis 3.Determine energy requirements for scenarios 4.Light on rose 5.Not a static, but a growing, adapting crop 6.Improve path tracer (Göttingen) 7...

38 Thank you for your attention! Funded by: Horticultural Production Board & Ministry of Agriculture


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