MASTER IN ADVANCED ARCHITECTURE Digital Digital Matter - Intelligent Constructions
2014 /15 SELF-ADAPTIVE MEMBRANE KINETIC PASSIVE SYSTEM
BARCELONA BARCELONA
MASTER IN ADVANCED ARCHITECTURE
SELF-ADAPTIVE MEMBRANE
Research Studio: Digital Matter- Intelligent Constructions
Director: Areti Markopoulou Faculty Assistant: Alexandre Dubor Assistant: Carlos Bausá Martínez
Nohelia Gonzalez Shreyas More
INDEX Abstract
05
Introduction
07
01 State of the art The Air Flow(er) Adaptive Skins Smart Screen 02 Thesis project
08 10 12 14 16
03 Material research Nitinol SMA (Shape Memory Alloy) The loop movement
18 20 24
04 Nitinol Joints Design of joints Conclusions
27 30 39
05 Application on fabrics Elastic responses on fabrics SMA in metal rings Lever machine principle
40 42 44 50
06 Embedding lenses
62
07 Design system Activation of Nitinol Design application
76 78 80
08 Passive model Joint design in the system Distribution of forces Project costs
86 88 91 96
09 Conclusion
98
10 References
100
6
Abstract On the advanced approach of architecture some designers have been trying to fill the gap between the kinetic responsive and the totally passive systems. Performative models applied in architecture have been always designed for being electrically driven. The systems in the sustainable category, in spite of reducing the energy expended by automatically respond when the climate conditions are advantageous or disadvantageous for the quality of the controlled environments, still require electricity to work. Even though an improvement is achieved, it seems contradictory that electricity is still needed. Right now there are two well defined study lines that barely merge. These are the completely passive systems and the performatives. Although it is true that classical passive systems have shown amazing results of the level of comfort of controlled environments, nowadays there seems to exist the need for merging these classical systems with the available technology in order to change the direction of the sustainable design. Taking advantage of the technology embedded on the smart materials, there is constantly growing possibility to create a new path among the existing design lines, in order to evolve the concept of sustainability, not only for the highly developed areas but also for creating an impact on the underdeveloped communities. Architecture have been constantly, although not uniformly, evolving and, in an era where the change has been triggered and the sustainability is steering the path, the change is in our hands.
7 05
06
Introduction Avant-garde architecture has been hindered by the lack of cost-efficient manufacturing techniques and limited access to information [1]. In the contemporary time there are innumerable intelligent architectural systems widely used in construction as facades for shading, lighting, and humidity control which have many ways to monitor the mechanism that brings about change in the system to obtain responses. The advantage of these responsive technologies is that they are adaptive to time and changing situations, which can actively address to problems and resolve them. Such systems in architecture are very essential to maximize the efficiently of performance and not having to depend on man force for controlling the machinery. By the other hand, according to the International Energy Agency (IEA) 47% of the world‘s energy consumption corresponds to indoor environmental comfort control systems [2]. Classic passive systems, applied in the architectural scale, such as cross-ventilation and facade orientation have been one of the responses to the energy problem. However, these systems are not enough. Moreover, there are many products on the market that use sensors, processors, controls, and motors to automatically close/open blinds when a room becomes too warm/cool. One of the advantages of these automatic systems is that they can help conserve energy that is expended on cooling. However, motorized shades consume electricity in order to operate, and there is no zero-power system existing on the market [3]. The following research is based on how a particular smart material, such as Nitinol Shape Memory Alloys (SMAs), can regulate heat gain and help to conserve energy expended on heating ventilating and air conditioning (HVAC). Our main objective is to develop a system capable to automatically respond to the heat parameter, simply by changing its shape when the rays of sun hits it. 07
Smart materials such as Nitinol and other shape memory alloys have been started to be widely used in the architectural scale. Moreover, many designers that have experimented with this SMAs have used electrically driven systems. As a base for our research, three projects that use SMAs as actuators were chosen. The aim of all the three projects is to work passively under the heat parameter where in two of three cases, the final prototypes were not tested under real conditions, using an external source of heat as heatguns to simulate it. Since commercial SMA springs activation temperature goes from 20 to 80 degrees, reducing its strength with the reduction of temperature, it is a challenge o the use of it completely passively. In spite of the effort for developing sensible zero energy systems, the use of SMA is restricted in terms of strength and activation temperature. Projects that have used high temperature, thus strong SMA, stayed on the protorype stage; such is the case of the Air Flower [4] and Adapative Skins [5], where the testing stage was never performed under real conditions. By the other hand, completely passive projects like Smart Screen [3] that perform under environmental temperature are restricted by the stenght of the SMA and the small movement that this creates.
08
01
STATE OF THE ART
09
The Air Flow(er) Lift Architects The Air Flow(er) is an energy independent thermally active ventilation device which behaves like a flower, whose “petals� open wide when exposed to warmer temperatures. It aims to regulate airflow and interior temperatures without electricity. The active component is a Shape Memory Alloy (SMA) wire. When an SMA is in its lower temperature form, it can be easily deformed into a new shape. However, when the alloy is heated through its transformation temperature, it recovers its original shape with great force. The four leaf prototype could be used as the operable blind or shade on either the exterior or interior face of a naturally ventilated double-skin facade system.
10
In the summer, the cavity between the inner and outer skin is vented out of the building through the automatic response to temperature. In the winter, a double-skin facade acts as a passive solar heater by using the device to seal the cavity and minimize the faรงade heat loss [4].
Air Flow (er) Lift Architects 11
Adaptive Skins Sushant Verma & Pradeep Devadass, AA School of Architecture
The project investigates responsive building skin systems that adapt to the dynamic environmental conditions. Heat is the primary parameter for regulation, leading to energy efficiency and dynamic spatial effects. A passive skin was developed using SMA springs actuators and regular springs on a tensegrity structure. Fabric pieces were attached to the model so when its active, different shadow patterns are created by the attraction of the structure elements into the heat. Heat gun was used for the performative prototype. [5]
12
Adaptive skins Verma & Devadass 13
Smart Screen Decker Yeadon LLC SmartScreen is a solar shading system that opens and closes in response to changes in ambient room temperature. The system is both a sensor and a motor so it does not require additional sensors, processors, motors, or electricity to operate. At the low ambient room temperature (21ยบC), the screen would be fully open to absorb solar heat gain; at the high ambient room temperature (26ยบC), the screen would be fully closed to deny solar heat gain. A customized alloy was used to work under low temperature (compared to regular SMA with activation temperatures from 60ยบC to 90ยบC). Unlike conventional SMAs that allow for a restorable deformation strain of about 7%, the customized SMAs
14
only allow about 1% strain or less. This means the system uses very little movement which has far less movement than a standard, electrically driven SMA. The R-Phase SMA actuator includes a bias spring and center piston that turns the top rod. When warmed, the SMA pushes the piston down; when cooled, the bias spring overcomes the SMA to push the piston back up and open the screen [3].
Smart Screen - Decker & Yeadon 15
The dissertation aims towards
explored in series of experiments
understanding the materiality
to understand the potentials of
of Shape Memory Alloys which
this material for use in architectu-
transforms from one form to the
ral scale.
other on the change of tem-
16
perature and the application of
The aim is to study the materia-
resultant change in form into
lity and behavior of Nitinol SMA
architectural use.
actuator under the parameter of
The main objective of the re-
heat, and design an architectural
search is the develop of a novel
application using the properties
kinetic and passive system able
of expansion, contraction and
to perform only when solar heat
weight bearing strength from
is advantageous or disadvanta-
series of investigations to control
geous. Our aim is to explore the
a responsive architectural system,
gap between the passiveness and
dependent completely on passive
the responsiveness in architecture
heating techniques.
through the development of a
Quoting Decker and Yeadon,
responsive zero energy system.
“Many designers have experimen-
Since Nitinol SMA is a thermo
ted with SMA electrically driven,
responsive smart material, the
however is not a challenge to rai-
main parameter for its activation is
se the temperature to 90 degrees
heat. This particular smart material
by using electricity� [3]. Based on
possesses a great load carrying
this challenge, we directed our
capacity when it is transforming
research in a zero energy system
back to its programmed shape
that could work as both sensor
on deformation. This capacity of
and motor responding mainly to
pulling weights on activation was
the heat of sun.
02 THESIS PROJECT
17
Shape Memory Alloy (SMA) Nickel ti-
recover, when the deformation occurs
tanium, also known as Nitinol, is a me-
at certain temperature, the recovery
tal alloy of nickel and titanium, where
comes right after it at a slightly higher
the two elements are present in roug-
temperature and the material exhibits
hly equal atomic percentages e.g. Niti-
enormous elasticity, some 10-30 times
nol 55, Nitinol 60. Nitinol alloys exhibit
that of ordinary metal. [4]. Commercial
two closely related and unique pro-
SMA springs activation temperature
perties: shape memory and supere-
goes from 20 to 80 degrees, reducing
lasticity (also called pseudoelasticity).
its restorable deformation strain of 7%
Shape memory is the ability of Nitinol
with the reduction of temperature [6].
to undergo deformation at one tem-
On this research, commercial high
perature, on a stage called martensi-
temperature (80°C) SMA springs have
te, and then recover its original, unde-
been used in order to obtain the maxi-
formed shape upon heating above its
mum strenght from them.
“transformation temperature“, on the
A series of weight experiments were
austenite stage. Superelasticity occurs
performed
at a narrow temperature range just
springs and SMA spring to come upon
above its transformation temperature;
the strength of each and finding a ba-
in this case, no heating is necessary
lancer for couple them afterwards.
to cause the undeformed shape to
18
on
conventional
zinc
03
MATERIAL RESEARCH
19
Nitinol SMA (Shape memory alloy) Technical specifications Density
6.45 g/cm3 (0.233 lb/cu in)
Electrical Resistivity (Austenite)
82 X 10-6 Ω.cm
Electrical Resistivity (Martensite)
76 X 10-6 Ω.cm
Thermal Conductivity (Austenite)
0.18 W/cm·K
Thermal Conductivity (Martensite)
0.086 W/cm·K
Coefficient of Thermal Expansion (Austenite)
11 X 10-6 /⁰C
Coefficient of Thermal Expansion (Martensite) 6.6 X 10-6 /⁰C Magnetic Permeability
< 1.002
Magnetic Susceptibility (Austenite)
3.7 X 10-6 emu/g
Magnetic Susceptibility (Martensite)
2.4 X 10-6 emu/g
Elastic Modulus 75-83 GPa Yield Strength 195-690 MPa Poisson‘s Ratio 0.33
20
Austenite
Martensite
At high temperatures, nitinol assumes an interpenetrating face-centered cubic structure referred to as austenite (also known as the parent phase). At low temperatures, nitinol spontaneously transforms to a more complicated body-centered tetragonal crystal structure known as martensite (daughter phase). The temperature at which austenite transforms to martensite is generally referred to as the transformation temperature. More specifically, there are four transition temperatures. When the alloy is fully austenite, martensite begins to form as the alloy cools at the so-called martensite start, or Ms temperature, and the temperature at which the transformation is complete is called the martensite finish, or Mf temperature. When the alloy is fully martensite and is subjected to heating, austenite starts to form at the As temperature, and finishes at the Af temperature.[7]
21
Weight
00 gm
Zinc spring length 20 mm
Weight
110 gm
Zinc spring length 20 mm
Weight Zinc spring length
Expansion
00 mm
Expansion
03 mm
Expansion
Weight
00 gm
Weight
110 gm
Weight
Zinc spring length 40 mm
Zinc spring length 40 mm
Zinc spring length
Expansion
00 mm
Expansion
10 mm
Expansion
Weight
00 gm
Weight
110 gm
Weight
Zinc spring length 60 mm Expansion 22
00 mm
Zinc spring length 60 mm Expansion
19 mm
Zinc spring length Expansion
Zinc spring test series
330 gm
440 gm
220 gm
Weight
20 mm
Zinc spring length 20 mm
13 mm
Expansion
19 mm
Expansion
39 mm
220 gm
Weight
330 gm
Weight
440 gm
40 mm
Zinc spring length 40 mm
36 mm
Expansion
53 mm
Expansion
82 mm
220 gm
Weight
330 gm
Weight
440 gm
60 mm
Zinc spring length 60 mm
55 mm
Expansion
86 mm
Weight
Zinc spring length 20 mm
Zinc spring length 40 mm
Zinc spring length 60 mm Expansion
121 mm 23
The loop movement Zinc springs as counter - weight
From the series of tests on zinc and Nitinol SMA the capacities of individual springs are identified. This is further coupled together to obtain results when zinc and nitinol is connected in series. Zinc springs form 20 mm to 60 mm springs were tested in conjunction with SMA springs, resulting the 20 mm test failed since the tension on the hot stage was greater than the system strength. The optimum result with the greatest loop displacement couples a 20 cm SMA spring with a 30 cm zinc spring (a proportion of 40-60%). The displacement ends being 34% of the length of the system.
When the SMA is cold, the zinc spring pulls the nitinol in martensite state. At this phase the zinc spring is active. In application of heat, the Nitinol SMA contracts to reach austenite state and stretches the zinc spring untill the spring is cold again. This results in a loop movement of the central point of the spring. Depending on passive heating, the idea is to use this loop movemet to creat a change in the system in hot environmental conditions and undo the change when the environmental conditions are cold again.
24
Nitinol SMA spring test series
SMA length 20 mm
SMA length 20 mm
SMA length 20 mm
Weight
110 gm
Weight
220 gm
Weight
Expansion
00 mm
Expansion
10 mm
Expansion
330 gm
SMA length 20 mm Weight
440 gm
22 mm
Expansion
60 mm
Nitinol SMA - zinc spring test series
SMA length Zinc Length
20 mm 30 mm
Displacement 68 mm
SMA length
20 mm
SMA length
20 mm
SMA length
20 mm
Zinc Length
40 mm
Zinc Length
50 mm
Zinc Length
60 mm
Displacement 62 mm
Displacement 56 mm
Displacement 44 mm 25
26
04
NITINOL JOINTS
27
Open assembly of joints with heat actuator Length of zing spring
40 mm
Length of nitinol spring
20 mm
Total extension 54 mm Time to austenite state (contraction)
23 s (21.29 %)
Time of Martensite (expansion)
1 min 25s (78.71%)
Total time 1 min 48 s
Open assembly of joints with electricy as actuator Length of zing spring
40mm
Length of nitinol spring
20mm
Total extension 54mm Time to austenite state (contraction)
09 secs (7.43 %)
Time of Martensite (expansion)
2 mins 1 s (91.67%)
Total time 2 mins 10 s
Closed assembly of joint in aluminum tube Fails due to excessive heating of metal
28
1. Joint at cold temperature
Zinc- contracted (active spring)
Nitinol expanded
Puling joint when the nitinol contracts away from the system mobile point Pushing joint when the nitinol contracts towards the system mobile point 2
Joint at hot temperature
Nitinol- contracted (active spring)
Zinc- expanded
Illustration showing movements of
the spring in two states 29
Design of joints Basic linear actuator After different lengths of springs were studied to obtain maximum displacement, the best result was concentrated on a joint. The joint is designed with 20mm Nitinol spring and 30mm zinc spring connected in series, following the principles of the optimum movement from the loop movement test. The central point of connection of springs is mobile which slides in either direction while the ends are constricted by an acrylic tube. The Nitinol in martensite is stretched by the zinc spring maintaining equilibrium of forces. On actuation by heat or electricity, on the austenite stage, the Nitinol contracts, displacing the central piece which lengthens the joint by 34mm in a 100 mm joint. On completion of one loop, the displaced point returns to original position.
In brief, the joint behaves as a linear actuator that can be applied in many different designs considering its proportions. In this sense, the joint can be scaled up for a greater displacement considering that this last will be submitted to a 34% of movement regarding the jointâ&#x20AC;&#x2DC;s length. By the other hand, the diameter of the actuator remains the same as it is scaled.
30
6
5
4 3
2
Assembly of joints
1- Joint cap 2- 10 mm nitinol spring 3- Intermediate movable part A
1
4 - Intermediate movable part B 5- 15 mm zinc spring 6- 100 mm x 12 mm acrylic tube 7- Wire to positive battery source
7
8
8 - Wire to negative battery source 31
Nitinol Zinc Joint inside acrylic casing
32
After finalizing a basic casing for the joint, different treatments were tested in order to increase the inside temperature of the joint for reaching the activation temperature (75 -80 째C) of the SMA that is been used. 33
White Joints Test for reflection of light using cylindrical lens
0 min
20 min
Time taken for austenite initiation
20 min 0 sec
Maximum movement of joint
0 mm
Joint Section
Active Joint
34
Black Joints Test for absorption of heat using cylindrical lens
0 min
20 min
Time taken for austenite initiation
14 min 43sec
Maximum movement of joint
08 mm
Joint Section
Active Joint
35
Airtight black Joints Test for rise in temperature in air-tight apparatus using cylindrical lens
0 min
20 min
Time taken for austenite initiation
07 min 02 sec
Maximum movement of joint
08 mm
Joint Section
Active Joint
36
Brass powder filled Joints Test for effect of foreign material introduction using cylindrical lens
0 min
20 min
Time taken for austenite initiation
04 min 04 sec
Maximum movement of joint
08 mm
Joint Section
Active Joint
37
38
1
2
contracted spring
expanded spring
contracted spring
expanded spring
Conclusions It is a challenge to heat over 75째C degrees by using just the power of sun even in hot climates. For this reason, different methods were tested to increase the temperature inside the joint. Among these methods the casing treatment plays a main roll. Light and heat are both different types of energy, however, light energy can be transformed into heat energy. While dark colors absorb all wavelength of light and transform them into heat, light colors reflect them.
Using this theory as a base, a white coating was used in order to reflect light into the spring. Nevertheless, in 20 minutes under the sun no activation was visible. On this account, black coating was used to absorb light and increase the overall temperature inside the acrylic casing. Since the results showed an activation and contraction of 8 mm in 14 minutes and 43 seconds, a black and airtight joint was tested for avoiding the escape of hot air, showing a reduction of 55 % of the time. Also, a foreigner material with lower heat capacity than air, such as brass, was tested showing an 8 mm contraction in 4 minutes and 4 seconds.
As result, we concluded that the brass introduction in the joint could accelerate the responsiveness on the joint. However, none of the previous experiments showed enough contraction to achieve the optimum movement of 34% of the joint. For this reason, additional methods were tested.
1
Air Specific heat Capacity 1.005 KJ/Kg K
2
Percentage Contraction in sun 21.31%
Brass Specific heat Capacity 0.380 KJ/Kg K
Percentage Contraction in sun 48.99% 39
05
APPLICATION ON FABRICS
41
Elastic responses on fabrics SMA joint in tensile structures
42
0%
activation of nitinol joints
30%
100%
in-between openings
70.69% in-between openings
60%
activation of nitinol joints
46.66% in-between openings
100%
activation of nitinol joints
activation of nitinol joints
40.63% in-between openings
Objective To control different degrees of apertures between the fabric by activation of linear nitinol joints on passive heating. The aim is to be able to control a facade system which controls solar gain in the interior spaces using a complete passive system.
Conclusion The technique of direct application of nitinol joints on fabric is inefficient as the openings are controlled from 100% to 40% due to the limited displacement of each points on the surface of fabric.
43
SMA in metal rings Integration of counter force
44
In order to integrate the responsive SMA joint into the design module, a metallic ring with plastic recovery force was used to substitute the counterforce of the zinc spring. The recovery thereof was tested by measuring the deformation during the active and inactive state of the SMA spring. Different diameters on the same metallic strip thickness were tested to find the right counterbalance for the maximum loop movement.
a a
b
b
length a
length b
Static state
150 80
Dynamic State
165 48
Difference
15 40
Static state
105 72
Dynamic State
116 45
Difference
11 27 45
Static Fabric 0% activation of nitinol 31.89% opening
Heating Bottom right 100% activation of nitinol 34.51% opening
Heating Top right 100% activation of nitinol 34.51% opening
Heating Top left 100% activation of nitinol 34.51% opening
Heating Bottom left 100% activation of nitinol 46
34.51% opening
Objective Replacing linear nitinol joints with metal rings performing as the countering forces to retract nitinol to original position on cooling to control apertures on passive heating of nitinol spring.
Conclusion The technique of direct application of nitinol joints on fabric is inefficient as the openings are controlled from 31.80% to 52.07% due to the limited displacement of each points on the surface of fabric.
47
48
49
Lever machine principle SMA positioned in a pantograph system
50
The lever machine is one of the six simple machines identified by Renaissance scientists and it consists of a beam or rigid bar pivoted on a fulcrum. It is used to move an object at a second point by a force applied at a third. In an ideal system, the power into the lever equals the power out, and the proportion of output to input force is given by the proportion of the distances from the fulcrum to the points of application of these forces. This is known as the law of the lever [8].
T1= M1 a = M2b = T2
a
b
Since material testing on SMA springs showed great pulling force but relatively short movement, the lever principle was applied in a simple pantograph system where the movement was generated in a central piece which is smaller than the surrounding pieces. In this case, greater force, yet smaller distance, is needed for opening and closing the system.
51
Displacing one point on arc
Displacing two points on
Displacing two points
(open state)
arc (intermediate state)
linear (closed state)
Each single unit has 4 control points at the 4 corners of the frame. Together in a pair, 8 control points can be moved to deform the overall geometry which responds to the needs of the interior space. By pulling the strings of the fabric using nitinol joints, the angle of the facade at unit level can be controlled to redirect light in the desired direction.
52
Facade iterations
100% Open
75% Open
25% Open
100% Closed
When outside temperature above 35
Actuation temeprature reached
Initiating the system of joints to control the apertures
The facade system is an assembly of units interconnected with Nitinol springs which activate when the temperature of the environment reaches a temperature to heat up the nitinol. Each two units in the facade have the apparatus based on the lever principle that moves thanks to the Nitinol and zinc springs. For this particular purpose the joint was deconstructed, being placed the SMA springs in the central area, for closing when heated and the zinc springs on the edges for pulling the system to open.
53
System depth changing with seasons The depth in the facade system changes with the needs of controlling the interior spaces. The smart mechanism in the desgin can be connected with learning computers to facilitate different changes in system when the system needs to be override or in cold seasons. In summer solstice the facade is at its maximum depth and the fabric can be directed towards the light ray to harness diiffused sunlight. and control the amount of heat and light directly coming in. In winter solstice, the facade is shallow to harness most light and heat while the opening can be controlled to regulate the amount of wind entering in. A catalog with all the possible movement combinations for each season was developed in order to understand what the system could offer as response to the environmental conditions. In spite of the many combination, in the catalog it can be observed the repetition of shadow and light patterns, which means that the effect of them for the interior climate control was restricted.
The main limitations on this design was that the complexity of it did not respond to the benefits achieved by it. Also, forces as friction and the torque produced by the tensile fabric prevented the membrane from the optimum performance.
54
Galapagos results Exterior
Interior
Increased shading Environmental heat and light Environmental air temperature
Summer solistic - 21st June Increased shading Reduced heat and light Cooler air temperature
Light harness factor 1.97%
Winter solistic - 22nd December Reduced shading Environmental heat and light Environmental air temperature Light harness factor 28.43%
Reduced shading Reduced heat and light Cooler air temperature
Exterior
Exterior on sun
Exterior on shadow
Interior
Interior on sun
Interior on shadow 55
56
Percentage changes with orientation and seasons
57
58
The mechanism of facade includes nitinol and zinc spring ap-
paratus connected to deployable frame which slides over the tracks and closes. The fabric stretched over the two frames behaves as a solar shading in summer and reflects the light from its surface in winters. 59
60
61
The primary actuator for the designed responsive system is the environmental condition of heat. The actuating temperature of Nitinol springs ranges from 45-80 degrees Celsius. In order to make the Nitinol responsive at temperatures over 35 degrees Celsius, lenses are embedded in the system to amplify the heat inside the tubes.
62
06
EMBEDDING LENSES
63
Casting and production process
Since the produced lenses are customized, the focal length was adapted to the current needs. In that sense, the lenses are made with a focal length of 100 mm and 50 mm to focus light at different distances. Two different techniques were used to cast and produce various types of lenses for finding the highest increase on the temperature by the use of them. The first technique, in the case of linear lenses, a methacrylate tube of an specific diameter (consistent with the focal length) was use to directly pouring liquid plastic and obtaining the lens.
PLA printing, covered with plastic film
Methacrylate tube used as mold for linear lenses
Acetone was used on an ABS printing for removing the layers 64
By the other hand, for more complex geometries, the pieces with the final required shape were 3D printed using Makerbot Replicator for the subsequent casting. In the case of the plano convex lenses with focal point a PLA piece was printed and the layering texture of the 3D printer was removed by using plastic film. The Film was tighten in order to interpolate the layers and create a smoother surface. After casting, some texture still was observed however the focal point of the lens remain clear. Furthermore, the Fresnel lenses were printed with ABS filament. Since acetone is a solvent for ABS, after the printing, the piece was placed on a metallic cap of a container whose walls were cover with paper tissue and subsequently soaked in acetone. The container was closed and after 40 minutes the fumes solved the top layer of the piece turning it smoother and shiny. However, since the pieces were printed with a 5% infill, after the process the internal structure comes out creating a curvature on the surface. The concave molds are made using rubber silicon in a container by pouring the liquid in container and immersing a convex surface at the top of the liquid surface or attaching it in the bottom. Once the rubber is solid (14 hours later), the convex surface is removed to obtain a depression in the mold. After the mold is ready, liquid plastic is poured into it to form a singly convex lens.
65
Hand-made plano convex lenses
Temperature range without lens Date 13-03-2015, 12:40 hrs
Base temperature in Sun
25.10 0 C
Base temperature in shadow
24.40 0 C
Minimum reach in Sun (Tube)
33.30 0 C
Minimum temperature in shadow (Tube) 27.00 0 C Difference (Outside to Inside)
07.30 0 C
Temperature range without lens Date 13-03-2015, 12:40 hrs
Base temperature in Sun
44.50 0 C
Base temperature in shadow
25.40 0 C
Minimum reach in Sun (Tube)
55.50 0 C
Minimum temperature in shadow (Tube) 53.00 0 C Difference (Outside to Inside) 66
08.50 0 C
Arduino connected with thermistor for temperature readings inside the tube joint
Singly convex lens converging light to single focal point to accentuate the temperature inside the nitinol tube joints 67
68
Plano convex lenses Controlling specific points of the SMA to compress
69
Hand-made plastic lenses Plano convex lens
Rise in temperature at focus 6.3째 C
Plano convex lens
Rise in temperature at focus 4.8째 C
Spherical Fresnel lens
Rise in temperature at focus 7.6째 C
The use of lenses showed a significant increase of the temperature inside the joint. Being identified the Fresnel lenses as the most optimal solution. However, casting problems reduced their capacity. Commercial Fresnel lenses, nevertheless, demonstrate being more responsive and effective, besides the power can be controlled by reducing the surface area. 70
Commercial Fresnel lenses
Complete Fresnel lens Surface area of lens
468 cm2
Duration of test
10 sec
Initial temperature
42.60 oC
Final temperature
69.33 oC
Difference temperature
27.73 oC
Partial Fresnel lens 1 Surface area of lens
12 cm2
Duration of test
10 sec
Initial temperature
36.86 oC
Final temperature
45.66 oC
Difference temperature
08.80 oC
Partial Fresnel lens 2 Surface area of lens
4.55 cm2
Duration of test
10 sec
Initial temperature
33.66 oC
Final temperature
39.90 oC
Difference temperature
06.24 oC
71
Customized depth of lenses according to their location
Openings
Nitinol Spring
Openings
Deep Facade for increased shading Facade system- Open
72
Openings
Nitinol Spring
Openings
Shallow Facade for increased day light Facade system- Open
73
Lenses orientation and sun path Direction of solar rays
09:00 hrs
12:00 hrs
15:00 hrs
Day light hrs
74
Lenses work receiving perpendicular rays of light and directing them to a single point, increasing their intensity. Since rays need to be perpendicular, rigid lenses must be either placed in different positions for the activation at different hours in the day or follow the sun path. This last method would mean electricity is needed for the system to perform. However, by using flexible Fresnel lenses, a curved surface can be created in order to respond perpendicularly to the rays without the need of extra movements. The curvature, focal length and area of the lens can be adapted in order to respond to the design needs. Fresnel lenses have proved to be the most appropriate solution to increase the temperature since a small surface is powerful enough to activate the 80 째 C Nitinol SMA and its flexible complexion allows to create curved sections of lenses that are able to capture different sun rays angles besides perpendicular. Inasmuch as every part of one lens surface direct the light to one specific point, a large lens can be cut in sections and reorganized to cast focal points of light in a single line. This method was used for the prototype.. However the most optimal solution is using linear lenses capable to concentrate light in an uniform line, heating the SMA spring evenly and taking its performance to the maximum. This lenses are also available in the market only less frequently..
Focal point Fresnel lenses
Focal line Fresnel lenses
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The advantages of using fabric in the system relies in the application of a flexible material onto which rigid structural elements can be seamlessly planted to achieve complex organic movements. It also eliminates additional joinery allowing complex geometries without increasing the intricacy and weight of the system. Tension elements are also added in order the allow the deformation of the system and its recovery.
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07
DESIGN OF SYSTEM
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Actuation of Nitinol Deploying surface folds using nitinol springs
Linear displacement was applied to simple geometries to study its behaviour in the fabric-rigid elements system. This particular case is a flexible geometry which can be deformed into many possibilities by simply changing the position of the actuators or activating specific points. In this case, SMA was used on 3 points and the deployment was performed by passage of current.
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However, since passive systems can be hard to control, a more restricted geometry was needed in order to have a prediction of the different possible scenarios of actuation. In this sense, various tessellations were explored. A particular tessellation that deploys and expands to create volumetric space was chosen for further development. On the closed stage, a flat surface built out of square elements is created, whereas the open stage creates a dome - like deformation, revealing the triangular portions of the structure, increasing its height and creating volume. Actuators were located in the center of each set of component to allow/ restrict the movement. and tension elements were set on the edges to enable the recovery of the geometry into its original shape. 79
Design application Structural application in three scales
The characteristics of the system, passively kinetic and the movement achieved by using fabric as joinery reduces the possible scale of the structure. For this reason three reasonable small scale applications, at the same time catalogued as small, medium and large, were chosen as design system.
Since the geometry is the same for all of them, the main purpose is to achieve non-uniform deformation which responds to the solar path. In this sense, when solar heat is greater in some areas than the others, the geometry tends to expand towards that direction. This action could be defined as heliotropism. The reaction can be applied for different needs depending on the scale however, all of them related with the heat parameter. While in a garment scale it performs to cast shadow over the body, on an architectural scale it creates either small and temporary spaces, suitable for one person or applied in panels on a facade it creates a second skin with variable surface area and volume. 80
Smart garments Small scale
In a small scale application, garments were seen as a suitable option. The device, made of light structural inside panels embedded into two fabrics, create an uniform surface that opens up when solar rays reach it, creating a self-adaptive hat that provides shadow only when is needed.
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Stand - alone single person unit Medium scale
The volumetric properties of the geometry can be exploited with structural proposes. Since the actuation in mainly passive, it can always be open to unpredicted behaviours, for this reason, as a structural piece the geometry is capable of deforming in a small scale. A stand alone single person unit fits the expansion capacities, offering a space created only when sun touches the surface of the flat geometry. It is as a shelter that only appears when is needed. When the geometry is flat, the sun rays hits it evenly, however, when it starts deforming the rays will only reach specific areas, creating different volumetric shapes that correspond directly with the sun path. The entire geometry becomes a motor and a sensor that reacts under the light / heat parameter. The geometry layering is composed first by a fabric sheet that works as joinery and protection for the inside area. The panels that define the geometry gather energy from the same activation parameter, heat, and this one is stored and transmitted to the inhabitant for simple task like charging devices such as a computer or a mobile.
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01 Nitinol joints -
04
SMA springs with zinc springs 03 02 Binding folds integrated component with nitinol joints
03 Collapsing folds-
02
01
Porous energy absorptive cells for ventilation and storing heat
04 Deploying geometry composite of materials
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Ventilation building skin or roofing system Large scale
In a building scale the structure becomes a skin or additional roof system for passive ventilation and cooling. Set into panels, the skin performs locally adapting its shape according to the position of the sun. By using the passive SMA joint and the loop movement, no sensors, motors or electricity are necessary in order to respond to the climate conditions. On this scale, the system can ventilate areas, gather / release heat energy or both. In this sense, only as a skin, the energy exchange happens because of the amount of surface exposed to the sun and the difference on the materials that are temporarily revealed and those which are revealed all the time. By the other hand, as a roof system, the volumetric property of the structure also allows the management of hot/cold masses of air by altering the proportions of the space.
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1 01 Close surface A flat and standard height roof accumulates masses of hot air and prevent them from escaping.
2 02 Open Surface A volumetric roof increases the height of the space and the porous revealed surface allows the hot air to escape.
On a warm climate, hot air accumulates and since it expands, it becomes lighter and moves to the highest points of the room. While this happens, the sun heats the geometry and this starts opening. When opening, not only volume is created to take the hot air higher, leaving room for colder air in the habitable height, but also, a porous area on the geometry is revealed in the process. At this point, the hot air escapes until sun leaves and the geometry closes again. On cold climates, the exposed flat surface material gathers heat warming the air and avoiding it to escape from the room.
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08
PASSIVE MODEL
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Joint design in the system Embbeding process Basic final joint
06
Linear Fresnel lens
05
Mobile arm
04
03
02
01
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Nitinol SMA and Zinc srpings
Anchor points for the springs
Absorbing surface (optional)
Perforated Tube for ventillation
Joint embbeded with absorbing surface
Joint embbeded without additional surface
A basic and general joint was design with the aim of being adaptable to many different situations where a linear actuation movement is required. For the best performance and most compressed design, linear Fresnel lenses with an approximated focal point of 2 cm are required. Focal length may depend on the design where the joint is applied, while the need of an absorbing surface is subject to the size of the system, since the potential of the lenses depend on the surface area exposed to the sun. For the study case explored in the research no additional surface was needed since the Fresnel lens area is enough to increase the temperature to 80 째C. For this reason, the system was even more compressed and the loop movement was embedded in a square as thick as the SMA actuator spring.
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Joint embbeded in geometry
05
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Linear Fresnel lens
04
Mobile arm
03
Nitinol SMA and Zinc srpings
02
Anchor points for the springs
01
Case study geometry
Distribution of forces Expanding joint system SMA springs naturally contract when heated. However, the system requires to be open when the rays of sun reaches it. For this reason, the state 0 of the model, before adding the joints its open. By adding a tensile force on the edges of the structure the volume is created. In addition an expanding joint was used, so when the joint is inactive the cable inside it will tense and close the structure and when it is active it will lose the cable allowing the geometry to open.
Active joint - expanding mode
Inctive joint - contracting mode
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Activated passive model.
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Solar rays are magnified by the Fresnel lenses, heating the SMA springs to 80째 C. The contraction of the Nitinol releases the tension induced on the edges of the structure allowing it to open and expand, creating volume and increasing its height in the process 93
Inactive passive model.
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Project’s costs Retrieving with passive environmental control systems In spite of the common believe that smart materials such as Ntinol SMA applied in architecture trigger project’s costs turning it into an unachievable and expensive solution, by the punctual and strategic location of such materials, great results can be accomplished. When system of this kind implemented in architecture, it is important to find the right balance between the impact of the reduction of the expended energy and the energy expended on the system’s production. The price of commercial SMA spring varies depending on the thickness, length and temperature. The springs used in the project (0,75 mm thickness and 2 cm long springs) have an approximated cost of 10 $, while Fresnel lenses have a cost of 1,5 $. Therefore, the price for the kinetic passive core of the system is 11,5 $ for a 20 by 20 cm panel. Thus, the cost of the developed prototype (80 square centimetres) is around 184 $ and which means 287 $ per square meter, By the other hand, conventional solar panels, the closest approach to a “passive” system capable to respond performatively by using sensor, motors and processors though the electricity generated have an approximated cost of 900 $ per square meter [5]. However, the comparison may be complicated since the standard price for this systems is calculated from kWh and not surface area.
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The approach of working with SMA
the increase of weight and other
Nitinol is mainly to use its smart
complicated joinery. For the na-
properties on a passive system
med reasons the system has been
that works only with solar energy
used in relatively small scale.
and that behaves as a sensor and
By the other hand, the system is
a motor. By using this smart ma-
restricted to 34% of linear mo-
terials we were able to develop a
vement of the total length of
zero energy system, in this case
the joint. However, SMA springs
applied into a structural prototype,
connected in series can be used
but that can be adapted into dif-
to achieve greater displacement
ferent designs that requires linear
as springs connected in parallel
displacements.
can be used to achieve greater
The advantage of a passive - ki-
force of pulling.
netic structure is that it can reduce
As
the amount of energy expended
veloped a novel and sustainable
on climate control of interior areas,
method for kinetic systems which
adapting and responding to many
does not require electricity to per-
different conditions. By the other
form, exploiting the properties of
hand, this represents a system
a commercial smart material and
that can ,not only complement a
helping the climate control without
building design, but also added
the need of any motor, sensor,
to existing structures with lack of
processor or control.
sustainable characteristics.
We believe that the research can
Nonetheless, the system is being
be taken further in other to sur-
limited by the passive condition,
pass the limitations and that can
since is not fully controllable. Also,
be widely apply in real contexts,
the joinery system implanted, a
overcoming the prototype stage
fabric as the element that hold to-
and transforming in tangible ans
gether the system, is used to avoid
sensible architecture.
contribution
we
have
de-
09
CONCLUSION
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1
Responsive skin. Aalto University Digital Design Laboratory, ADD.
2
International Energy Agency.
3
SmartScreen: Controlling Solar Heat Gain with Shape-Memory System.
Martina Decker, Peter Yeadon, 2009.
4
Air flower. Lift Achitects.
5
Adaptive skins. Sushant Verma, Pradeep Devadass, 2011 - 2013.
6
International Organization on Shape Memory and Super Elastics technologies.
7
Nitinol Devices and Components.
8
A Simple Lever, Stephen Wolfram.
10
REFERENCES
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