2015 10 07 thin 07

PUSH PLANAR

07

RACHEL MEI-LAN TAN

PUSH PLANAR WEEK 07 10/14/2015

00 THINNESS 01 STRUCTURE 02 GARDEN 03 HYDROPONIC SYSTEMS 04 LEAF SECTIONS 05 VERTICAL GARDEN PROPOSALS

THINN

STRUCTURE INFRASTRUCTURE HARDWARE

GROWTH

WATER ELECTRICITY HEAT

BENDING MOMENT

FREE NETWORK TO SELF PARTITION SPACE

LEAF

CIRCULATORY SPINES

FAVELLA

HIERARCHICAL NETWORK

ORGANIC EXPIRATION

SLIME MOLD

GROWTH BASED ON NEED+INFILL

CIRCULATOR EFFICIENCY

SQUATTING

FLOW FAVELLA OF PEOPLE

SPAT LIM

PERCEIVED DIMENSION

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NESS

TURBULENCE TENSION

PERMEABILITY EROSION BEACH

FLEXIBLE APPLICATION + ADAPTABLE

THINNESS

FUNCTIONS WITHIN BANDING

LIGHT WIND WATER

CONNECTIVE MEMBRANE

TIAL MIT

HEIGHT

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MASTER FORMULA

SPONGE CORAL

LADDER

RY Y

CHANGING NEED

DENSITY

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Form Inspiration STUGGART

Form Inspiration The compliant mechanism of the Flectofin® is based on the Strelitzia reginae, a South African plant which is evolutionarily optimised for weight transfer of birds [Rowan 1974]. The flowFig. D.47 L􀑖􀑒􀑛􀑕􀑎􀑟􀑑, J. et al. (2010) Form-finding of Nature Inspired Kinematics for Pliable Structures.

L􀑖􀑒􀑛􀑕􀑎􀑟􀑑, J. et. al. (2011) Flectofin: a nature based hinge-less flapping mechanism.

91 er-bird-interaction comprises a reversible deformation which enables a so-called valvular pollination mechanism. The flower features a protruding perch of two adnate, blue petals which act as a landing platform (Figure D.51 (a)-(c)). When the bird lands on this structure to reach the nectar at the base of the flower, its weight causes the perch to bend downwards (Figure E.51 (b),(c)).

This bending triggers a sideways flapping of the petal laminae, and the previously enclosed anthers (male sexual flower parts) are exposed so the pollen can be attached to the birds feet and chest (Figure E.51 (c),(f)). When the bird flies away, the open perch resets to the protective closed state again due to its elastic properties. A section through the perch was prepared by biologist and research partner Simon Poppinga which reveals a monosymmetric 12

build-up (Figure E.51 (d),(f)). There are three reinforcing lateral ribs on each side, which are loosely connected by thin petal laminae. The lower ribs are joined on a cellular level, thus forming a composite rib. The uppermost ribs carry the thick wings which cover the sheath cavity when it is closed. The ribs consist mainly of fibrous tissue with vascular bundles, hence relative rigidity, and serve mainly to carry the bird’s weight [Endress 1994]. A constricted zone seen in a microscopic section between the upper ribs and wings shows no fibrous tissue, which indicates higher flexibility in comparison to the surrounding zones, enabling the elastic sideways bending of the wings (F in Figure E.51 (e)). This kinematical system was verified by rebuilding it as a physical model that demonstrates similar adaptive behaviour (Figure E.52.) of an unsymmetrical bending motion as an integrative part within a reversible deformable structure with multiple deflected equilibrium positions. The FlectofinŽ principle is thus an instrumentalisation of this failure mode. This highlights how nature and engineering differ in problem solving and shows that the structures and principles identified in biological concept generators can provide impulses and innovative means to achieve elastic kinetics in technical structures in a previously unknown manner.

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In the second level of abstraction, the Flectofin® principle is converted into several possible structural configurations, one of which are shown in Figure D.50. The beam element, for example, can be supported as a cantilever or single span beam as well as any other structural system in which continuous bending can be induced. In the wing of the Flectofin®, the stiffness near the backbone is increased. This is a major difference to the Strelitzia reginae which shows a distinct localised area of high flexibility near the rib. By stiffening the region near the backbone, the entire wing is forced into a more uniform bending deformation.

Therefore, the bending radius is largely increased which reduces bending stress and stabilises the wing in all positions against wind induced deflections.

From an engineering perspective, the flapping mechanism in Strelitzia reginae can be described as a hinge-less movement, in which an external mechanical force (the weight of the bird) initiates a complex deformation of multiple structural members (ribs, laminae and wings). They are linked in such a way that the kinetically stored elastic energy can reset the system so that this mechanism is not only reversible but also repetitive. The actual mechanism behind this movement is known to engineering as lateral torsional buckling, a failure mode that is attempted to avoid by sizing structural members to adequate stiffness or introducing eccentricities as shown in the physical models in. The models of a suspended bridge in Figure D.53. show lateral buckling for the upper system where all hinges are in a line. For the lower system eccentricity leads to stability and thereby avoidance of sideways tilting of the cable bracings when the main beam is starting to flex. What is known as a failure in engineering is thus instrumentalised by the plant for a highly effective compliant mechanism.

Form Optimisation An important question in the development of the Flectofin® was the reduction of stress peaks at the transition of a semi-elastic shell element to a beam element. ‘Biological solutions’ to this particular problem are found in many plants species. Being exposed 14

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to wind or other forces, plant leaves have developed several strategies to avoid notch stresses in the transition areas from leaf lamina to petiole. The most common solutions are based on gradual transitions achieved through changes in fibre orientation, variable thicknesses and optimised contour lines. In the FlectofinŽ, the change of thickness and fibre orientation within the shell element enables a stress harmonisation throughout the entire surface (Figure D.54 a and c ). This was made possible by increasing the stiffness in the shell element at the transition to the beam element. Hereby, the bending is forced further into the surface, leading to larger bending radii and, consequentially, smaller stresses. Remaining notch stresses on either ends of the shell element were reduced by optimising the contour line. Figure D.54 b shows how the contour geometry of Eucalyptus spec. leaves were applied to the shell geometry. The stress peaks were considerably reduced by this application of tension triangles [Mattheck and Burkhardt, 1990)]. These geometrical optimisations reduce the maximum notch stress to approximately 60 % of the permissible stresses for standard GFRP. A further development to stabilise the inactive position is shown in Figure D.55 A-E, with a configuration of two wings that theoretically interpenetrate in pos. A. Therefore, they rest in pos. B where they push against each other and share a large contact area which highly increases their stability. Due to their concave curvature in the inactive state, the wings will bend outwards when the backbone is actuated as shown in pos. B-E. As a positive side effect of the symmetrical deformation, the eccentric forces in the backbone are induced by the bending of the wings counteracting each other. This limits the torsion in the backbone and results in a more filigree profile. This double FlectofinŽ is a further development of the initially proposed façade component, which has an increased shading efficiency and higher wind stability.

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D 5.3 Structural Behavior The compliant mechanism of the Flectofin速 is described as systematised failure and deformation. More specifically, uniaxial bending of the beam causes an unsymmetrical bending motion of the shell element which is triggered by torsional buckling.

Such instability is observed in beams with slender profiles exposed to in-plane bending. When the bending reaches a critical point, the beam undergoes a combined deformation involving both outofplane bending and torsion [Simitses and Hodges 2006]. While lateral-torsional buckling is usually initiated on the compression side of a beam, in the case of the observed system, the compression side is reinforced by the backbone and held by the supports; consequentially, it is the tension side that is deviating into outof-plane bending due to its low lateral stiffness. This coupled deformation of torsion and flexion is also referred to as warping.

D 5.4 Gained Insights Structural behaviour While the FE simulation with perfectly symmetrical geometries and consistent mechanical properties suggests the existence of a robust mechanism for both the single as well as the double Flectofin速, the usual discontinuities from manufacturing caused some unpredicted behaviour in the elastic kinetics of the sys tem. A long period of optimising the manufacturing technique and adopting the geometry for a more robust mechanism was needed to guarantee a functioning of the compliant mechanism.

Specifically, the curved attachment of the thin-shell wings to the backbone stabilise the mechanism into a set unfolding direction.

In the case of the Flectofin速, this logic of curved line folding was discovered accidentally from manufacturing tolerances but is understood as a key to the function of the mechanism because of parallel investigations of other plant movements such as the Aldrovanda discussed by Schleicher et. al. (2011).

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RUNNING FENCE : CHRISTO & JEANNE-CLAUDE, SONOMA, 1972-1976

Material The system’s inherent material requirements for high strength and low bending stiffness are most adequately fulfilled by FRPs. After a comparison of different high modulus fibres, glass fibres were selected because they are much cheaper than carbon fibres, more translucent, and have a better weather resistance than aramide fibres, for example. Many different glass fibre woven fabrics and non crimp fabrics that differ in their fibre lay-up and area weight were tested for stiffness, resistance against wind induced vibration, and the 90° bending properties near the base of the backbone. So far, the desired high strength and low stiffness properties were achieved by arranging 4-8 very thin plain woven fabrics with an area weight of 80 g/m² in a set of layers (Figure d. 56 and B-D in Figure D.57). In order to further reduce tension forces at the edges of the fin, in particular at the meeting point of the wing and the backbone, glass rovings were spread out along the direction of forces (F in Figure 57). For the matrix, an ultra-flexible epoxy resin was chosen that was additionally treated with several dyestuffs to satisfy diverse optical demands.

In order to achieve the essential high quality in the laminate, the Flectofin® was fabricated by a manufacturing method called the vacuum bagging process (VAP). A special layer of air-permeable foil is used to eliminate trapped air in the laminate, thus, enhancing the material’s largely dynamic properties. This manufacturing technique was one of the keys to a successful production of immaculate and mechanically consistent elements.

Design and construction One of the main advantages of the Flectofin® is the diversity of structurally stable positions which the structure can attain be tween fully opened and closed. The system is thus adaptable to different boundary conditions which could optimise efficiency in shading systems. A significant expansion of possible future applications is given by the fact that the system functions without a straight turning axis; it can therefore be adapted to facades with curved geometries. (These aspects of the Felctofin® and other biologically inspired compliant mechanisms are studied 20

elaborately in the Doctoral thesis of my colleague S. Schleicher “Bio-inspired Compliant Mechanisms for Architectural Design”) As a proof of this concept, it inspired the façade of the Thematic Pavilion at the EXPO 2012 trade-fair in Yeosu, Korea, by Soma Architects and Knippers Helbig Advanced Engineering (see Figure C.28. Knippers Helbig Advanced Engineering was then commissioned with the planning and constructional design of this kinetic facade. In a first investigation, it was determined whether the Flectofin® principle could be magnified to the large scale of 108 lamellas with varying heights between 3 m and 14 m. It was proven that up-scaling of the basic principle is possible, yet could not entirely fulfil the architectural intentions of the facade. Inspired by the Flectofin®, an alternative elastic mechanism was developed, based similarly on structural failure (buckling).

These further developments show the potential for such basic discoveries, in this case, the instrumentalisation of failure and deformation

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Bending Moment FORM FINDING MODEL SIMULATION

Form-finding is generally understood as the process of developing the geometric form of a structure based on mechanical behaviour.

In contrast to a common design process, form-finding is a deterministic process in which the setting of the physical boundary conditions leads to a single solution.

From a strictly mechanical point of view, form-finding can be defined as an optimisation process, in which a target stress field is given and the corresponding geometrical form is searched for.

Therefore in structural engineering, the term form-finding is mostly linked to tensile membrane structures, as well as catenary arches and shells, in which form-finding automatically includes form-optimisation based on structural behaviour. The geometry of bending-active structures

has to be form-found similarly based on mechanical behaviour; however, stresses belong to the solution and therefore ‘formfinding’ does not automatically include the aspect of structural optimisation. Beyond the definition of boundary constraints, the ‘form-finding’ of bending-active structures involves the adjusting of more variables which include setting the length and mechanical properties of the bending-active elements and introducing various couplings and inner constraints.

It may therefore be more precise to speak of a ‘formdeveloping’ process. However, despite having more variables of physical boundary conditions, it is still a deterministic process, objectively based on mechanical behaviour, and shall therefore generally be referred to as ‘form finding’ 22

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The fundamental differences in the form-finding of form- and bending-active structures lie in the definition of length and surface dimension, the simulation of material behaviour and the consideration of residual stress: 路 In form-active structures, the surface dimensions are the minimal result defined by the stress state and boundary conditions which are independent of their input dimensions. In terms of material behaviour we simply consider the fact that a membrane serves only to carry tension forces by simulating a surface under pure tension. The actual mechanical material properties of the membrane, however, are not considered since the form-finding is purely based on the equilibrium of tension forces and only geometrical stiffness is considered. Residual stress is a target input.

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Scaling & Scalability STRESS STIFFENING EFFECTS

Since residual stresses are dependent on the bending radius and cross-sectional height, we are restricted by material strength in the sizing of structural members. This limitation means that the size of a cross-section may not be defined freely according to the requirements for strength and stiffness under external loads.

Hence, scaling problems may occur when changing the scale of a bending-active structure.

In classical structural engineering we may consider three ranges of scale: the physical structural model, a reduced scale structure and a large scale structure, in which dimensional analysis and the derived scaling laws help to calibrate the proportions of test results between different scales [Harris and Sabnis 1999]. In today’s engineering practice, analysis is mostly

based on the Finite Element Method (FEM) in which dimensions are considered by the relation between geometrical and mechanical input variables.

Structural analysis is therefore always done on a virtual 1:1 model.

With these powerful computational means the necessity for structural physical models has been reduced to some dynamic problems e.g. wind tunnel testing.

Reduced scale mock-up structures have similarly become dispensable.

In the development of bending-active structures the physical structural model has regained importance as a form-finding tool in the early design stages. An emergent amount of medium scale bending-active research structures is raising the question of their relevance for large scale building structures. In some 28

cases like the gridshell, visionary projects such as the ‘Multihalle Mannheim’ with 64 m span have long proven their scalability.

In this particular project, which was predominantly developed through physical models, scale factors for self-weight were derived to correctly simulate dead load deformation of the scaled model [Happold and Liddell 1975]. Other expressions of active bending in building structures are yet to be analysed for their scaling behaviour. The research presented in this chapter is based on the experiences from various case study structures, all in the range of 2 to 10 m span. In all of these structures the scalar jump from a physical structural model to a medium scale structure was successfully undertaken. The question analysed now, concerns the scalar jump from a medium scale to a large scale structure and aims to fathom the scaling limits of various forms of bending-active structures.

Scaling in the most general sense is concerned with powerlaw relationships between two or more variables of a system.

Investigating the scaling of building structures the variables concerned are deformation and stability on the one side, load and mechanical properties on the other. If the relation of these variables is independent of the system’s dimensions we consider the system to be self-similar.

Some of the more common effects to consider for the scaling of building structures are: · Dimension effect: cubic increase of mass with scale · Load effect: quadratic increase of surface area leads to quadratic increase of surface load · Size effect of material: probability of material defects increases with size, whereas the influence of material defects increases for small size specimens. · Height effect: exponential growth of wind-speed with height combined with quadratic growth of wind-load with speed. · Dynamic effects: Wind induced vibration etc.

Since the investigations in this paper are aimed to be of general nature we only consider the change in mass and load. The effects of change in material properties, wind load and dynamic behaviour with scale are very individual to each project and are therefore not taken into account in the further investigations.

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Their influence on scaling, however, will play a role on the construction of some large scale bending-active structures.

F 2.2 Dimensional Analysis of Elastica In order to gain a principal understanding of the scalability of a simple bending-active system some initial studies are made on the elastica arc. From section B2.4.3 we can recall that residual stress in such an elastically deformed beam can be determined with the Euler-Bernoulli law, in which the bending moment Mő is proportional to the change in curvature as shown in equation (4ѓ) [Fertis 2006]. With the section modulus Wy and the consideration that the width b of a cross-section has no influence on the maximum bending stress we can write the residual bending stress as an expression of the cross-sectional height h, the Modulus of Elasticity E and the Curvature 1/r (5ѓ).

In (5ѓ) we can see that both curvature (1/r) and cross-sectional height h have a linear influence on the residual stress caused by active bending. The moment of inertia Iy is therefore limited by a given minimal curvature in the system and the permissible bending stress of the chosen material. The radius of curvature can be expressed as a function of the span Li and the rise fi. In (6ѓ) this relation is given with a scale factor s. Simplification of the equation shows that s can be excluded as a linear factor; thus, linear up-scaling of a structure allows for a linear up-scaling of the cross-sectional height while keeping the residual stress constant.

Assuming constant material properties this leads to the overriding question, whether the influence of the span L on the deflection U z can be compensated by the moment of inertia Iy, if the scaling of the cross-sectional height is limited to be linear for keeping the residual stress ΗM constant.

Deriving the dimensions using the Buckingham Pi Theorem: Dimensional analysis enables a convenient investigation of physical behaviour by combining the variables of a system into dimensionless groups (Pi-terms). The Buckingham Pi-Theorem states that the relations in any physical system can be described by a group of n-rd Pi-terms, in which n is the number of variables and rd the number of basic dimensions therein (rank of the dimensional matrix) [Buckingham 1914]. In mechanics, the basic dimensions are mass, length and time. In the following 30

considFђџѡіѠ, erations on static structural behaviour, force is chosen as a basic dimension without further reduction into its constituent components for better comparison to known engineering equations.

Based on the Pi-terms, a functional equation can be derived which shows a reduced form of the relevant variables; however,it does not give information about the nature of the solution. The exact form of the functional relationship has to be empirically obtained by a set of experiments in which the Pi-terms are systematically varied. Analytical analysis of the individual Pi-terms often is sufficient enough to describe the change of system behaviour with scale, without knowing the complete solution of the functional equation.

Investigating the deflection for a given elastica curve of span L stiffness EI and the line load qz and excluding the influence of mass and residual axial force we may derive the following functional equation: ( , , , ) Z y qz U f L E I 5 Variables: Uz, L, E, Iy, qz 5Ȭ2= 3 PiȬTerms 2 Dimensions: [mm], [N] The dimensional Matrix is: []11241 []00101 mm N Uz L E I y qz The dimensionless Pi-terms may be derived using various procedures, some of which are explained and discussed in detail by [Barr 1983]. Independent of the procedure it must be noticed that there is no unique set of Pi-terms that can be derived for a given problem. Pi-terms may differ in type depending on the choice of a repeating variable that eliminates dimension, additionally transformations of Pi-terms are possible. Here the results of the system deflection under a linear load were derived with the step wise procedure using L as the repeating variable.

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F

Structural Behaviour of Bending-active Structures

force. Their linearity prove the similitude derived a variations of the elastica curve, in which the rise to sp constant in correspondence with the incline of the gr

s¡qz Uz

Ĺ—

In Figure F.1 and F.3 an elastica curve with f/L=0.15 is i by plotting the load deformation with correspondin sion stress for a step wise increasing scaled line loa to exclude findings that are limited to symmetric s line load is applied asymmetrically. In Figure F.50 inv were compared at two different scales with s=1 and s the nonlinear behaviour at higher loads and final sn buckling.

s¡L s¡f 2

Ĺ™

4

Ĺ›

6 Â–ÂŠÂĄÂ’Â–ÂžÂ–ČąÂœÂ?Â’Ä›Â—ÂŽÂœÂœČąČąÂ?ČŚ ȹƽȹŗśƖȹȏřśƖ

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Finally, the dotted line shows the elastica in a calcu out dead load and residual stress. Here, the two load curves almost perfectly match and snap-through buck at the same load factor, ̇Î?= 0. This clearly supports esis made in section 2 that the bending-active elastic similar if dead load and axial force are omitted. In graph shows how the curves are very close in the l and the influence of dead load grows with size (̇Î?= and ̇Î?= 1 for s= 8).

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Ĺ—Ĺ–

For each scale, the system is calculated in three di narios. First, (indicated by the continuous lines) incl load and axial force, showing a difference in load f between scale s=1 and s=8 at the point of snap-throug In a second scenario, (dashed line) the residual stress by axial force N is disabled. This leads to a shift of b by load factors ̇Î?= 1.0 for s=1 and ̇Î?= 1.2 for s=8 h point of failure. The difference between scales is red ̇Î?= 1 to ̇Î?= 0.9.

Fig. F.48

F 2.4 Scaling of Case Study Structures With the scaling investigations on three successfull study structures, the above drawn conclusions are jump in scale from a prototypical structure, in the si hibition pavilion, to a large building structure is in The choice of material for these bending-active struct ited by availability of materials offering high streng

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F2

250

for all tio is a

straight f/L: 0.05 f/L: 0.15 f/L: 0.20

Uz [mm] (with qz = s x qz)

200

igated mpresorder ms, the ations owing rough

nt sceg dead ̇Ώ= 1 ckling. theregraphs at the d from

f/L: 0.30 f/L: 0.50 f/L: 0.60 f/L: 0.75

150

100

50

0 0

2

4

Scale s [-]

6

8

10

Fig. F.49

5

NJΏƽŖ 4 NJΏƽŖǯş

Loadfactor ΏȱǽȬǾ

withection occurs ypothis selfal, the range or s= 1

Scaling and Stability

3 NJΏƽŗ Ȭ 2

Fig. F.48 Study of Elastica curves with constant span and varying rise at different Nonlinear

lt case ied. A an exgated. is limth low

S=1 / dl: yes Ȧȱ ǯ ǯ S=1 / dl: yes Ȧȱ ǯȱ ǯ S=1 / dl: no Ȧȱ ǯȱ ǯ

1 s·L Ώȉ ȉqz Linear 0

0

ŖǯŞȉΏȉ ȉqz Uz

20

40

60

Displacement UzȱȦȱ ȱǽ Ǿ

S=8 / dl: yes Ȧȱ ǯ ǯ S=8 / dl: yes Ȧȱ ǯȱ ǯ S=8 / dl: no Ȧȱ ǯȱ ǯ 80

100

Fig. F.50

scales.

Fig. F.49 Deflection curve for different scales of the elastica arcs in F.48.

Fig. F.50 Load deflection curve of the elastica curve with 15 % f/L ratio at two scales; showing linear, nonlinear and snap-through failure range.

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Garden FROM SCAFFOLD LIVING WALL TO VERTICAL GARDEN AND THIN FARMSCAPE

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SCAFFOLD

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CRYSTAL CASTLE

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FRAME

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LIGHT SURFACE

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DENSE SURFACE

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VERTICAL PARK

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ENCLOSED GREEN

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VERTICAL HERB GARDEN

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HYDROPONIC SYSTEMS

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Hydroponics WATER WEUGHT ENCLOSED SYSTEM PUMP

The main principles behind the hydroponic drip system are relative simple which makes them incredibly easy to use, hence their popularity.

Vital nutrients are added to a tank of water to create a nutrient reservoir which is kept separate from the plants. The water is then pumped up a network of tubes, and is released to the plants individually.

The pump can be controlled by a timer, taking any manual watering out of the equation, and allowing you to decide how frequently you want a watering cycle to occur. You can also place an emitter at the end of each tube in the network to allow more, or less, water to reach a specific plant during each watering cycle. This means that you can put a range of different plants into the same system and tailor make watering cycle to cater to the different plants’

individual needs. There are two types of drip systems: the recovery drip system and the non-recovery drip system.

The recovery part of the name is pretty self-explanatory, and refers to whether the water recycles itself or not. In a hydroponic recovery drip system, any excess nutrient solution will drain back into the nutrient reservoir, where it can be re-used. This makes the system much more efficient; consequently, a relatively low amount of maintenance is needed.

You will have to check the solution reservoir periodically: as the plants absorb the nutrients this will start to distort the makeup of the nutrients remaining in the water.

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Aquaponics BIO FILTRATION OTHER WILDLFIE PUMP

Aquaponics is the combined culture of fish and plants in recirculating systems. Nutrients, which are excreted directly by the fish or generated by the microbial breakdown of organic wastes, are absorbed by plants cultured hydroponically (without soil). Fish feed provides most of the nutrients required for plant growth. As the aquaculture effluent flows through the hydroponic component of the recirculating system, fish waste metabolites are removed by nitrification and direct uptake by the plants, thereby treating the water, which flows back to the fish-rearing component for reuse. In my system tilapia will be produced along with a variety of herbs, leafy plants, vegetables, and perhaps fruits.

The aquaponic system I will be utilizing is a scaled down version of the University of the Virgin Islands commercial scale system. It is roughly

1/4th the size of the UVI system, but may be multiplied in accordance with resources and demand.

The UVI system has been producing tilapia for more than a decade. It is a proven system.

Aquaponics has several advantages over other recirculating aquaculture systems and hydroponic systems that use inorganic nutrients solutions. The hydroponic component serves as a biofilter, and therefore a separate bio-filter is not needed as in other recirculating systems. Aquaponic systems have the only bio-filter that generates income, which is obtained from the sale of hydroponic produce such as vegetables, herbs, and flowers. In the UVI system, which I copy, and which employs raft hydroponics, only calcium, potassium and iron are supplemented. The nutrients provided by the fish would 54

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Green Sky Growers is a true technical marvel, a state of the art farm which is one part laboratory and one part organic garden. It raises thousands of pounds of fish and vegetables every year using a mutually-beneficial farming technique called aquaponics. Green Sky Growers raises everything from tilapia to perch, herbs to tomatoes, delivering them fresh to the public and a hungry group of local restaurateurs. If you enjoy a dish

of striped bass and leafy greens at the restaurant below, you may have no idea that the ingredients were sourced from 50 feet above.

Green Sky Growers have turned to aquaponics to increase their yields and lower their resource needs. Aquaponics is the combined raising of fish and vegetables in a mutually-beneficial, closed-loop system. It is a combination of “aquacul60

ture”, the farming of fish, and “hydroponics”, the raising of vegetables in a soilfree, nutrient-rich water solution. On its own, aquaculture can create toxic waste water which cannot be reused and must be discarded. In hydroponics, spent nutrient solution can also be toxic. With aquaponics, the fish waste is naturally transformed from ammonia into nitrates which becomes plant food. In this process, the plants filter the water and strip the toxic ammonia to provide clean water for the fish. It’s a best of both worlds system, a genuine ecosystem where the plants and fish form a symbiotic relationship as managed by the farm’s team. What makes Green Sky Growers different from your average farm is their focus on state-of-the-art technology. Their two combined greenhouses are managed by custom software that measures environmental conditions and adjusts the conditions inside. On breezy, warm mornings, the greenhouse software will open the wall shutters to allow breezes through and to keep the inside temperature in a healthy range. Once the mid-day sun heats the greenhouse toward suboptimal temperatures, the software opens a shade system which covers the glass roof above.

If temperatures rise above manageable levels, chillers will lower the water temperature to keep the fish healthy.

Everything is automated– the software system has a temperature goal and will automatically adjust a range of variables to maintain that temperature indoors. The fish are everywhere at Green Sky Growers. There are five main tanks 61

which house hundreds of fish per tank.

During our visit, there were three tanks of tilapia, one tank of striped bass and a fifth tank in preparation for the arrival of perch fingerlings. The tanks are massive, and the fish within them are happy. An automated feeder drops feed into each tank at regular intervals. While the fish do congregate near the windows during feedings, they have space to roam and they are free from predators throughout their growth cycle. The hydroponic growing systems at Green Sky Growers range across a few different disciplines. Rows and rows of Nutrient Film Technique systems raise big, leafy and blemish-free basil and lettuces in nearly half the growing time of traditional soil farming. The spinning aeroponic towers, shown above, spray the plant roots with nitrate-rich water that gives the plants what they need to grow green and bear fruit. They rotate, slowly, allowing for even sun for all plants throughout the day. After the water passes through the “NFT” systems and the aeroponic towers, that water is now plant-purified and ready to be pumped back into the fish tanks. -

Nutrient Film CONSTANT FLOW OF WATER SLOPED ROWS

NFTs are often used in commercial hydroponics, particularly for short harvest crops.

An NFT system does not require a timer.

Instead, the nutrient solution is pumped from the reservoir up into the growtray in a continuous cycle. The growing chamber is built with the slightest downhill decline, allowing the solution to trickle from the top end of the tray to the bottom, where it is recycled back into the nutrient reservoir.

Instead of a regulated watering schedule, the plants in an NFT hydroponic system are provided with a constant flow of nutrient solution.

The slope is set at a shallow angle to ensure the solution only trickles along the growing tray. However the slope is sufficient for ensuring that the solution does reach the bottom, where it is drained back into the reservoir. This

ensures the growtray is never flooded, which prevents your plants from being overfed. In fact, only a small film of nutrient solution is accessible to the plants — which are suspended above with their roots hanging down — at any given point.

Because there is no timer involved there is less scope for anything to go wrong.

This means maintenance is kept to the bare minimum: You simply prepare the nutrient solution and then turn the pump on.

Because the system can run for so long without being manually checked, they usually include an air stone in the nutrient reservoir which is vital for keeping the water within the system oxygenated.

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Aeroponics MIST ROOTS DIRECTLY FASTER GROWTH

The aeroponic system is the most technologically advanced of all the hydroponic systems. Many top scientists have claimed that this very system could be the solution to food shortages in the future.

The plants are suspended in the air, as in the NFT system, with their roots hanging down below. The nutrient solution is then pumped up a tube, where a second higher pressure pump sprays the solution as a mist over the dangling roots.

Because each misting provides the plants with less food than a standard cycle in, say, a drip system, the misting takes place considerably more frequently, which does mean a more advanced timer is required. This, as well as the high pressured pump, can mean that the component costs are higher for this type of system.

The nutrient water is moved around far more frequently in this system due to the regularity of the feedings, as well as the actual process of turning the water into mist. This means the nutrient solution is far more oxygenated than in any other system, and this helps the plants achieve faster growth rates. The plants will also adjust to their feeding methods, and will grow more roots to enable them to absorb more nutrients from the mist.

The reason this technology is considered essential for future food production is that it offers the possibility of a group of plants to be grown vertically, meaning less land is required to farm. If a plant can be suspended on a vertical wall, with their roots protruding out the other side, then the roots can be misted using the techniques already described.

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Common Crops Produced On A Commercial Scale Leafy Greens: Lettuce, Basil, Spinach, Bok Choy, Swiss Chard, Kale.

Herbs: Basil, Chives, Dill, Parsley, Cilantro, Mint Fruiting Plants: Tomatoes, Cucumbers, Peppers, Eggplant, Okra, Strawberries Flowers: Zinnias, Marigolds, Cosmos, Nasturtium

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Growth Down RE-ORGANIZATION FOR WIND

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HOW THIN?

LEAF again SECTION LAYERS COATING THICKNESS PROGRAM air space - intercellular gaps within the spongy mesophyll. These gaps are filled with gas that the plant uses (carbon dioxide - CO2 ) and gases that the plant is expelling (oxygen - O2, and water vapor). cuticle - the waxy, water-repelling layer on the top and bottom surfaces of a leaf; it helps keep the leaf from dying out (and protects it from invading bacteria, insects, and fungi). The cuticle is secreted by the epidermis. Label the cuticle on the top and bottom of the leaf. guard cell - one of a pair of sausage-shaped cells that surround a stoma (a pore in a leaf). Guard cells change shape (as light and humidity change), causing the stoma to open and close.

spongy mesophyll - the layer below the palisade mesophyll; it has irregularly-shaped cells with many air spaces between the cells. These cells contain some chlorophyll. The spongy mesophyll cells communicate with the guard cells (stomata), causing them to open or close, depending on the concentration of gases. stoma - (plural stomata) a pore (or opening) in a leaf where water vapor and other gases leave and enter the plant. Stomata are formed by two guard cells that regulate the opening and closing of the pore. Generally, many more stomata are on the bottom of a leaf than on the top.

lower epidermis - the waxy skin (outermost cells) on the underside of a leaf, usually one cell thick; it keeps the leaf from drying out.

upper epidermis - the protective, outer layer of cells on the upper surface of a leaf, usually one cell thick. The epidermis secretes the waxy cuticle. The upper epidermis contains some guard cells (but fewer than the lower epidermis).

mesophyll - the chlorophyll-containing leaf tissue located between the upper and lower epidermis.

These cells convert sunlight into usable chemical energy for the plant.

vein (vascular bundle) - Veins provide support for the leaf and transport both water and minerals (via xylem) and food energy (via phloem) through the leaf and on to the rest of the plant.

palisade mesophyll - a layer of elongated cells located under the upper epidermis. These cells contain most of the leaf's chlorophyll, converting sunlight into usable chemical energy for the plant.

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SURFACE AREA DETERMINED BY ABSORPTION OF SUNLIGHT

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BEECH LEAVES

Beech leaves. Light micrograph of a transverse section through two beech leaves (Fagus sylvatica). The shapes of the two leaves are different because the bottom leaf is constantly exposed to bright sunlight, whereas the top leaf is in the shade in the lower parts of the tree. The sun leaf, in comparison to the shade leaf, has a thicker cuticle to reduce water loss through transpiration, more layers, bigger cells and more chloroplasts to capture more sunlight (photosynthesis), more starch grains (stored sugars made photosynthesis) and is thicker with more vascular tissue and supporting fibres (yellow) in the midrib.

Magnification: x100 when printed at 10 centimetres

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SUN VS.SHADE : MAPLE ACER

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FORM : SURFACE AREA IN RELATION TO WIND + SUNLIGHT + WEIGHT

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CIRCULATION : GATHERING POINTS + STRUCTURE

Water lily leaf. Light micrograph of a transverse section through the leaf of a water lily (Nympha sp.) plant. All aquatic plants (hydrophytes) have a similar structure.

The upper epidermis of the leaf has a thin cuticle (top) underneath which is a multi-layered palisade mesophyll. In-between the palisade cells are elongated sclereids (purple) for support. Underneath this is the spongy mesophyll and large intercellular air spaces (lacunae, white). The vascular bundles (dense patches) consist of xylem (red) and phloem (dark-blue ovals). The base of the midrib, under the epidermis, consists of collenchyma cells (dark blue). Magnification: x103 when printed 10 centimetres wide.

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PERIPHERAL DIVISION OF SPACES : CIRCULATION

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NETWORK OF LEAF : COVERING AREA

Tea leaf. Light micrograph of a crosssection through a tea (Camellia sinensis) leaf. The upper and lower epidermis on the surfaces of the leaf are blue. Under the upper epidermis are palisade cells (brown), which contain chloroplasts, the site of photosynthesis. Beneath this a spongy mesophyll layer with large spaces between the cells. At bottom left, a stoma (pore) is seen. Stomata allow gases and water to enter and leave the plant. Magnification: x230 when printed 10 centimetres wide.

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AT THE SCALE OF A CITY BLOCK

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LEAF : AMSTERDAM CANAL

Heather leaf. Light micrograph of a transverse section through the leaf of a heather (Erica sp.) plant. Heather is a drought plant (xerophyte). Xerophytes have evolved an anatomy that cuts down water loss through transpiration. The epidermis consists of thick-walled cells covered in a thick cuticle (lightpink). Underneath this are the cells of the palisade mesophyll and spongy mesophyll containing chloroplasts where photosynthesis takes place.

Magnification: x234 when printed 10 centimetres wide.

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7 BIOMES

Cross-section of a Beach Grass leaf (Ammophila breviligulata) a monocot, showing recessed stomates. LM X40.

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AMYLPHERNIA

The grass that’s primarily responsible for trapping wind-blown sand and building the dune systems around our coast that are such important wildlife habitats. Marram grass survives in the arid environment of a sand dune by rolling up its leaves during long periods of drought, so that all the leaves’ breathing pores or stomata are inside the rolled leaf, minimising water loss. with the outside surface of the leaf at the bottom of the picture (smooth, curved surface) and the inner convoluted surface at the top. The outer surface of the leaf at the bottom is composed of a layer of thick walled cells, covered with a thick cuticle to resist wind-blown sand abrasion and this layer also acts like a spring, giving the leaf a natural tendency to roll up under drought conditions. The stomata are hidden on the inner surface of the leaf amongst those stubbly hairs near the bottom of those convolu-

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tions – which in the whole leaf are actually ridges and furrows that run along the whole length of the leaf.

The clusters of thin-walled blue cells at the base (i.e. in the ‘valleys’) of the furrows of the convolutions are responsible for unrolling the leaf – when it rains and the plant takes up water these thin walled cells inflate like balloons, forcing the leaf to unroll. Other features that you can see in this leaf cross section are the snaking rows of reddish cells which are actually the cells containing most of the chlorophyll, that carry out photosynthesis – The other distinctive features are the scattered structures that look like ‘smiley faces’ with a pair of large ‘eyes’ with a blue open ‘mouth’ – these are the leaf veins that conduct water and sugars along the leaf – they’re the plant’s internal plumbing system.

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HOLLYHOCK LEAF

Fungus - sack with spores coming out.

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PINNEAPLE

The cross-section of a mature ‘Smooth Cayenne’ leaf can be up to 4mm thick with approximately half the volume occupied by water-storage tissue. When moisture levels are good, up to half of the 4mm cross-sectional thickness of a mature leaf is made up of specialised water storage tissue. This tissue serves as a reservoir and is drawn upon to maintain plant growth, and even fruit development, during periods of inadequate moisture. After extended dry periods this tissue decreases to near nil – a sign of drought.

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PINE

The leaves of pine trees are called needles. Though their shape is different from the leaves of most angiosperms, they contain more or less the same tissue types. Pines often live in harsh conditions: hot, dry summers and freezing winters. They are good at withstanding environmental stress. Their needles, with a low surface area-to-volume ratio, help reduce damage due to drying out or heavy snows.

Pine needles also have some features not seen in Syringa leaves.

Transfusion tissue surrounds the vascular bundle, and apparently helps transport materials into and out of the vascular tissue. This tissue is abundant in pine needles, but not in most leaves of flowering plants.

Resin ducts carry resin, which is a hydrocarbon-containing substance that may help protect the leaves.

The cuticle is visible as a faint pink layer around the outside of this pine needle. The stomata are sunk into small pits in the epidermis; this reduces airflow and evaporative water loss.

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SUCCULENT

A cross section of Phemeranthus teretifolius, a succulent, leaved perennial herb. In addition to the single, large central bundle, a 3-D ring of smaller vascular bundles is visible at the junction of outer photosynthetic tissues and inner water storage tissues.

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Blister Formed by Phytoptus Pyris

by Leaf

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Clatonia

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PONDWEED

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DIACTYLEDON

Dicotyledon leaf cross section vascular bundle vascular tissue xylem phloem epidermis mesophyll leaf anatomy midrib. 200 X optical microscope photomicrography plant anatomy botany dicotyledon 113

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OLEANDER

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OLEANDER

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LILY

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TEA LEAF

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SYRINGIA

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LINGUNSTRUM

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MAPLE ACER

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Notice the dark green bodies within the various cells found in the images of cross sections of plants above and below; these are chloroplasts.

C4 plants like the corn examples below, have two types of photosythetic cells, which differ in form and function.

Bundle-sheath cells surround the viens found in leaves. In C4 plants they are photosythetic in C3 plants they are non-photosynthetic. Both C3 and C4 plants have photosynthetic Mesophyll cells.

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EPIDERMAL OUTGROWTH

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EPIDERMIS

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AMOPHILA

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CHLORPLASTS

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BIG BOX x

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BEACH

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BEACH : BREAKWATER

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END