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Artificial Photosynthesis Panels for Maximizing Daylight Exposure

January 10, 2013 4 comments

Introduction

In the application of this technology, there is a chamber where the reaction occurs to provide the nourishments. The limiting supplies are the carbon dioxide, water, surface areas of reaction on the catalyst for reaction and the intensity of sunlight received. The first three are easily solved by:

Firstly, providing a scrub, which consistently extracts carbon dioxide from the surrounding air and resupplies it to the chamber.
Secondly, providing a constant flow of purified water pumped up from Irvin’s water collection intervention.
Thirdly, breaking the catalyst down into powdered form to maximize the amount of surface exposure.

This leaves the last factor, which studies of the natural photosynthesis has shown that rate of photosynthesis is directly proportionate to the intensity of sunlight received. The intensity of sunlight received is only partially controllable, where the supply is natural and the receiving surface depends on the geometry of the exposed surface.

In this exercise, I am attempting to prototype the clear surface to test out which characteristics of the geometry enables us to maximize the potential to receive sunlight.

The Process

I am to design digitally based on research on other technologies which require maximum sunlight intensity, namely the PV cells development, and then to send the models for computer numeric controlled milling to create a mould using MDF in preparation for vacuum forming using PVC. During some initial attempts, I have discovered that the vacuum forming is quite accurate in capturing even the texture of the mould, hence there was some manual preparation before we can actually send the mould for vacuum forming. The PVC geometry is then tested with a Lux Meter on top and below to get a relative difference in Sunlight absorbed by the surface. Comparing the amount of light diffracted and converted to heat within the material might not give us an accurate numerical result but it provides us with a base value that can be compared with other PVC geometries’ potentials.

The Design

The very initial design was a quick decision to develop a pod-like chamber to run water, carbon dioxide and metal catalyst through to maximize the other supplies besides sun intensity. Inspiration was taken from the natural process of photosynthesis where there are pod-like cells called the chlorophylls aligned side by side, housing the functions required to convert the supplies into glucose and oxygen. The design was generic and did not respond to it’s surroundings.

With this, I started off by looking more into the natural geometries of plants, since they grow in the manner to maximise the receiving of what they need. I chose 2 characteristics of geometries that I was to test on: Fractal Geometry and the Fibonacci Sequence (Golden Curves)

Fractal Geometry:

Taking into account that to maximise sunlight intensity received, one important factor is that maximum sunlight is obtained when surface is perpendicular to the sun rays, hence the exposure to the sun path, East to West is important.
Also the Sunlight intensity near mid-day is highest and hence this should be maximized as well. Hence the base geometry is a wave-like surface, with larger amounts of surfaces facing up to maximise mid-day sunlight.


2 more iterations were created to test the effects of fractal growth. In this case, the base geometry is re-panelled onto itself into a more complex geometry. This is repeated again for a 3rd time.

Fibonacci Sequence (Golden Curves):
These geometries are found in broccoli, sunflowers and other plants. The lines subdivides the surfaces into smaller parts to increase the overall surface exposure. The Golden Curve is generated using the Fibonacci sequence of numbers to dictate the size of squares aligned next to each other in a circular manner. A quarter circle is drawn using the points with the longest distance within two adjacent squares. In nature, this repeats itself fractally as well where the fibonacci sequence is used to decide the number of curves repeated radially in one direction and the next number for the curves in the opposite direction to provide the subdivisions for example the sunflower.

Readings

Conclusion:
Fractal Geometry has a great impact on surface exposure, leading to higher sunlight received. From the experiment, layer 1 absorbed 50 Lux
Layer 2 absorbed 60 Lux
Layer 3 absorbed 80 Lux
This aligns with the tests that MIT did with accordion shaped PV Cells where they managed to increase the amount of energy generated by increasing surface exposure by mimicking the folds on an accordion instrument.

The golden curve is a natural occurring method for subdivision, based on how cells regenerate itself. It is a supporting element to fractal growth but is not entirely affected by the need to maximize sunlight.
From the experiment, the reading is 100 Lux

Techniques

After the CNC milling is done, the mould needs to be processed such that the surface is smooth in order to replicate the transparent nature of the reaction chamber when placed for vacuum forming. I have picked up the industrial design method of using putty and primer to coat the top surface layer of the mould to create an extremely smooth surface.


This is done by applying an initial layer of putty on a loose particle free MDF surface to fill up the gaps in the material. The model is sanded down using a 400 grade sandpaper after the putty dries to remove any unevenness. A second layer of putty is applied across to coat the entire model. It is re-sanded down to create a base for priming. after sanding it down till relatively smooth surface, spray coat a layer of primer and leave to dry for about 30 minutes. Sand it down using the 400 grade sandpaper until surface is even and that there is a slight gloss. This step can be repeated 2 to 3 times to achieve a better consistency. Sand it further with a grade 1500 sandpaper until surface is glossy. The mould is ready for vacuum forming.

Problems

While attempting to vacuum form, there was an issue with a loose table template, which causes the air to leak and creates an issue that the PVC does not wrap around the surface of the mould properly. Check for leaks and in this cause, the table top template is not fitted properly. The PVC should cling onto the form nicely.

When heating the PVC, in my case a 1mm PVC, heat it for about 150 seconds and because of the ability for pvc to stretch for quite a lot, try not to use the air blast to prestretch the pvc. try to raise the mould about 10 cm below the PVC before starting the vacuum and raising the table. There was an attempt when i pre stretched the PVC and the mould was too far from it that when I started the vacuum, the pvc overstretched and by the time the table is raised to the top, the PVC folded and some of it went under the table top template. causing the PVC and the mould to be stuck on the machine.

Before setting the mould for vacuum forming, note that PVC then to cling tightly to the mould and when air cooled, it contracts further and have an even firmer grip onto the mould. MDF being of a compressed powder form, does not provide firm adhesion between itself and the putty/primer. In my attempts, the putty and primer became stuck onto the PVC.
I have done all my prototypes the same way but after the exercise, I realised that I should have coated the top of the primer with some lubricating oil, like WD40, so that the mould can be easily extracted from the PVC.

In the experiment to test the Sunlight, be sure to take readings on top and below the PVC quickly because the change in cloud cover might influence the readings. It would be better if there were 2 Lux Meter and that the readings are taken simultaneously.

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Rapid prototyping a quick-response shelter

January 8, 2013 Leave a comment

Introduction

The basis for my design was a deployable structure with the express purpose of aid relief. Therefore, the development of my design was focused specifically towards three key issues: it had to be compact and easily transportable when in storage, quickly deployed with minimum of action, and stable when fully open. These three drivers would direct the formation of material, joints and assembly concerns.

The inspiration for the structure was a portable folding stool, with a swivelling mechanism that resulted in a stable tripod base when deployed, but a compact bundle when closed. The spaces created beneath the legs, as well as the span created by the seat, was the suggestions of a possibly useful space that interested me in further exploration.

The final purpose of such a tripod was to provide an elevated rail on which food cargo can be suspended, for ease of movement and to facilitate distribution.  Thus, the carrying capacity of the structure was a big issue that had to be addressed.

First prototype


The aim of the first prototype was to explore if it was possible to have four legs, because my initial hypothesis was that the four point, square footprint would be more helpful in organising space, when multiple structures are used together. From there, I hoped to examine the space created underneath the legs, to develop the use of the structure further.

From the swivel motion of the stool, I designed a joint that I hoped would allow the same freedom of movement while being stronger when scaled up to the size of a full tent. The idea was that the collar would restrict movement to only the basic motion needed, to prevent wobbling and destabilization. Furthermore, it was supposed to take the reciprocal arrangement of the legs and direct them through the collar in a controlled manner, to ensure loads are properly distributed.

Second prototype

 

The first prototype showed that the motion and deployment was possible and functioned as intended. However the tubular legs of the first prototype were inefficient and bulky at full scale. Thus, I redesigned them with more depth and less width, with a rectangular profile which would hopefully be more efficient in carrying loads. Next, to further reduce weight I also cut out circular sections from the legs, which gave the structure some added functionality bonuses, since I believed I could develop those areas as attachment points for additional structures.


 

   

However, the next problem was that fitting a collar around the new legs would re-introduce the bulkiness problem, as the diameter required to fit around the angular centre portion would be proportionally much larger than the slim legs, especially when closed, which is disadvantageous for my intended usage.

Therefore, I decided to do away with the collar, and create the reciprocal mechanism directly into the form of the legs.

I introduced notches into the legs, which, when fully opened, would provide a wider surface for each leg to rest on the next.

This model was laser cut from 5mm acrylic. The test was to ensure that the notches functioned as intended, and that there were no collisions in the movement. At a 5mm thickness and a 1:20 scale, the model accurate represented the actual dimensions of the full scale structure.

From this model, I observed that:

  • The reciprocal structure worked as intended. The legs properly leaned on one another, creating a complete load bearing structure.
  • The central axis does not take any load, once the legs fully lock into place. This is assuming no loads are applied at the center, which is my intention. The roof structure was intended to continue from the upper portion of the legs.  However, the axis would have to be very exact in limiting the legs to prevent wobbling while they are in the process of opening.
  • The legs were not thick enough. The actual structure was intended to be aluminium, so in digital form, the slender legs seemed strong enough. But the physical model showed, especially next to scale human figures, that the legs would need to be thicker.
  • The length of the legs could be shortened without compromising functionality.
  • Most importantly, the notches would have to be wider. The model had a tendency to slip, and once the reciprocal pattern was broken, the structure would collapse. Thus, a larger contact area between each leg was necessary.

Lastly, the choice of material for the model was, in my opinion, not satisfactory in conveying the structural strength and stability of the intended usage. Thus, I decided to construct the third prototype out of aluminium.

Third prototype

One more major benefit of using aluminium would be that I could also accurately show the I-beam profile that I intend for the legs, to show the structural strength of such a form.

The aluminium was purchased from http://www.teckcheong.com/

Rectangular flat bar profile, 76.2mm width by 9.53mm height. The minimum length sold was 6100mm, which they cut into 1 meter portions for me.

The plan was to use the CNC router to hollow out the I-beam portion, and then cut out the outer shape, to save time. Also, I decided not to fully cut the circular portions out either, to save time as well.

All these time saving measure had to be taken because cutting aluminium is a slow process. The stepover for the 6mm drill bit was limited to a maximum of 50% of the width, 3mm, and the pass depth for each run was a tiny 0.5mm. For a 3mm cut, this was 6 passes, multiplied by two sides. To Cut entirely through the 9.5mm would be a significant increase

The machine used was the Versatil 2500.

Because my material was so small, it had to be attached to a wooden surface for the vacuum suction to properly hold in place.

There were two major concerns while cutting:

  • That the material stay firmly still
  • That the drill bit stay clean to cut properly

For both these concerns, overheating was the main culprit. Despite being air cooled, the friction from the drilling still creates a lot of heat, resulting in several negative outcomes.

Firstly, the metal expands when heated. Very slightly, but enough to shift it from its fastenings. Coupled with the movements of the drill bit, the material began to move when the drill bit cut along the narrow side of the metal. Furthermore, the vibrations loosened the screws, and the metal began to move significantly. This was addressed by adding more screws around the edge of the metal, wedging it in place.

The expansion also created a slight bulge in the middle, as the metal bar curved outward, varying the height of the cut. This was a minor issue, which did not drastically alter the final outcome.

A more major concern was that the heat also softens the aluminium, creating a build-up of melted aluminium along the cutting edge of the drill bit.

This is problematic because it reduces the cutting power, and also creates even more friction, heating up the metal further. If the cutting edge gets too clogged that it cannot cut, but the machine still tries to move the drill bit, DISASTER STRIKES.

The combination of all the abovementioned factors meant that the drill bit was cutting significantly deeper than 0.5mm each pass, and bit broke. In the above picture you can see the jagged, uneven cut resulting from excessive movement.

Thankfully, the bit broke high up, above the cutting edge, with enough space that it could still be reattached and used. Learning from the mistakes of the first run, the metal was more securely fastened, the cut speed was reduced, WD40 was used to lubricate the drill, and frequent pauses were made to ensure the drill bit was clean. Subsequent cuts were much cleaner, and without incident. Time taken: 4 hours per run, four runs total, for a combined time of about 16 hours cutting time.

Cutting out the edges took another hour per leg, as the metal saw cuts at an agonizingly slow pace. The edges were sanded down, and the entire leg was sandblasted to remove blemishes and smooth down the surface. The central axis was 3D printed, designed to be assembled with the metal legs in place.

The final model:


Roof prototyping

The full structure consists of a roof as well. The deployable motion of the roof was created in Grasshopper, but translating that movement into physical joints was a manual process.

The overall roof consists of four portions, which are basically a series of interlocking C-channels, on which each row of segments can slide along. The intention was to create greater coverage when fully extended, but a compact form when closed. Thus, the C-channels allow for a collapsible arrangement to maximise the difference between opened/closed positions.

In reality, the joint would likely have to consist of a rolling wheel mounted on a ball-and-socket joint, to allow for the freedom of movement required. In the model, this was achieved using simpler T-shaped joints that slotted into the C-channel. The 0.5mm gap required for 3D printing moving parts is responsible for this allowance. To save costs, the final, longest segments of the roof were not printed. Instead, sockets were prepared where I could attach on plastic styrene rods.

Full deployment sequence:


Categories: AY 2012/2013 SEM 1

Tower Crown Structure of the Queenstown Communal Permaculture Centre

December 6, 2012 Leave a comment

Prototyping as a Design Development Tool:

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Tower Crown Structure of the

Queenstown Communal Permaculture Centre

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For this project I am using rapid prototyping technologies is to develop detailed design for the crown structure with the aim to gradually increase materiality and detail while reducing material use.

Introduction

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The design project was conceived as a communal lifeline in Queenstown, Singapore in the event of a ruinous anthropogenic global warming and climate change episode in the not-so-far future.

Based on published studies by International Panel on Climate Change (IPCC), climate data made available by NASA and global energy and material consumption trends, a +2˚C scenario by the end of the next 50 years is very likely to happen, along with greater demand (due to increased global population numbers and the rapidly expanding middle-class worldwide) on essential resources which currently defines our civilization.

The most important of all resources – energy, which is taken for granted now with abundant fossil fuels controls the functioning of our entire world, from the most gigantic of multinational organizations to the individual resident of a rural village. A shortage of fuels will put pressure on the production of other essential resources for civilized living such as food and clean water – and nations had and will go to war to secure more of these resources for themselves.

In light of such daunting futures, what can a small island nation/city state with high population densities do for itself? Singapore will need to forge herself into a resource-resilient nation, starting at the communal level.


 

The Tower

tower

The towers which populate the project site in Queenstown is deemed the most important element of the project. The towers will attempt to solve problems concerning the creation and the functioning of the proposed facility – as the main structural solution for the facility, the primary collector of solar energy and water for use on site, and also as a supplementary planting surface for smaller sized food crops such as beans and vegetables.


 

The Tower Crown Structure

solar  The tower crown structure is the main apparatus with which solar photovoltaic energy and rainwater will be collected. Photovoltaic panels are deployed on the top side of the tower crown, collecting solar radiation and generating electricity for the facility’s use. The panels also functions as sunshades for spaces directly below it.

The tower crowns are shaped like a funnel which maximizes their rainwater catchment area, and then channel the wate­­­r to treatment and storage tanks beneath the facility.

The shape, proportions and dimensions of the tower crown have been previously determined via parametric studies in a software called Houdini by a different member of the project team. The effects of self-shading among the tower crowns, theoretical solar collection potential and theoretical limit of steel structure span in between 2 towers were used to analyze and then select the form with the best compromise in between the three performance indicators.

solar2


 

Rapid Prototyping to aid in Tower Crowns’ Design development

My area of investigation for this project using rapid prototyping technologies is to develop detailed design for the crown structure with the aim to gradually increase materiality and detail while reducing/optimizing material use.

1st Prototype

The first prototype was a model made based on the funnel structure generated in Houdini. The dimensions of the tower and crown structure were replicated in Rhinoceros,  and then mapped out as a series of panels on a 3d surface using Panelling Tools in Rhino. The structure was at this stage conceived as a precast-concrete shell structure.

IMG_0411-k

Being a design comprised of a series of shells/panels fused or joined together, the one option I chose for producing the first prototype was to unroll the panelled surface and to use the laser Eengravers to rapidly AND accurately cut out the templates which I will then assemble together. The model was put together using UHU glue and some discarded pieces of paper as backing sheets upon which I glue together the pieces.

The first prototype was a very solid construction, despite being made out of just grey straw boards. In retrospect, the first model was rough and very much heavier than the subsequent incarnations of the design/prototypes. This however proved to be a heavy structure and there were concerns that such designs may increase logistical loads of transporting the pre-fabricated concrete panels to site.

2nd Prototype

The second prototype model was that of a steel truss-tubes structure designed around the original dimensions of the tower and crown structure. The initial panel sizes of the previous prototype had to be revised. Subdivision/mapping of the crown/funnel surface using Rhino’s Panelling Tools was deliberately controlled to standardize the sizes of each truss tube members, which met with limited success. Member sizes on the crown structure inevitably became larger as we approach the larger, top-end of the funnel-shaped structure.

At this stage the prototype was still meant as a study/mock model hence I decided to produce the second prototype using the same method as the first.

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The resulting model is one that is significantly lighter compared to the first prototype, both visually and material-wise. At the time of this report’s writing, there is already considerable sagging and bending of some of the thinner members of the second prototype, causing the model’s shape to distort. I attribute this behaviour to moisture absorption of the grey strawboard. This presents a new set of realization to the tower’s design: thermal expansion of the steel tubes used to build the tower.

 3rd Prototype

The third prototype is the next step into the detail design of the crown structure. With this iteration of the design I intended to use the secondary structure on the crown (which supports the PV panels) as the tensioning members for the crown structure, reducing the use of the relatively heavier truss tubes structures. The joints between the truss tubes also become hardpoints for fixing on the secondary structure.

For this prototyping exercise I went ahead with using the Selective Laser Sintering 3D printing technique as offered in the EOS Formiga P100 3D Printer to produce the joints and then using 3mm thick bamboo skewers, cut to size as the truss tubes for this prototype model. They were secured together using hot glue.

DSC_2393

Cast acrylic sheets were made into the secondary structures using the laser engravers and then glued onto the 3D-printed parts. I did not make the acrylic panels for the entire prototype due to prohibitive costs of the acrylic sheets.

I then put the prototype to the test: placing loads (a 20mm thick plywood measuring 200mmx400mm) on top of the crown and measuring the deflection. As I did that, the thin acrylic members meant to take the tension loads broke. The structure did hold, however, due to the intrinsic flexibility and bending resistance of the bamboo skewers. The deflection was measured at about -12mm in the Z-Axis (the peripheral members of the crown was pressed down).

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 4th Prototype

The fourth and final prototype presents the final iteration of the design. Learning from the previous iteration, I realized there needs to be a stronger tension member for the crown, while keeping structural weight penalties down. I looked to the possibilities of employing high-tension cables such as those used in suspension bridges to take up this job.

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The prototype model for this iteration remained largely the same, using the same 3D-printed parts with just the addition of small holes to fit a thin nylon string through. I used 0.45mm thick nylon fishing strings to simulate the action of the tension cables.

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A similar test was done to this prototype, using the same load. The structure held and deflection was measured at approximately -8mm in the Z-Axis, indicating a slightly better performance.

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The revised, thickened acrylic panels and secondary structures were then added onto the structure. There were some discrepancies between the laser-cut panels and the space allocated for the panels, likely due to mistakes and inaccuracies when cutting the bamboo skewers to size.

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Conclusion

Rapid prototyping provided me with vital tactile and experiential feedback (as well as allowing me to experiment on the prototype models) where digital design is deficient in providing such information. The models aided me to gradually add-on details and systems and complexities to the model, helping me to advance faster in terms of detailed design for the crown and its components.

There is, however, still penalties when it comes to accuracy in spite of such high-tech machines – particularly due to human errors during assembly of the machine-produced parts. The machines are prone to inaccuracies of its own due to excessive use and some of its moving parts being heavily worn and becoming loose.

Despite all that, rapid prototyping techniques provided a way to quickly hold in my hands the object I designed and obtain from it valuable tactile feedback and even allowed me to conduct simple experiments on them, aiding along the design process.

Rapid prototyping: Deployable roof structure

December 3, 2012 Leave a comment

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This project aims to explore a structural system for a deployable roof structure based on the existing joint, QuaDror. This joint was chosen as an object of study as it allowed the structure to be compactly folded when not in use.

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The preliminary prototypes explored the system in terms of configuration, skin, and lastly to prepare for making the final prototype using the Versatil CNC machine.

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The plywood components were cut out using V Carve Pro on the Versatil CNC machine. The file is prepared as a 2D dxf file, with separate layers for the top and bottom toolpaths. The bottom toolpath is mirrored in order for it to align with the top after the material is turned over.

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The pieces are then positioned and glued, before the joints are reinforced by staples. The tops of the staples are trimmed off to reduce their visual impact.

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The next step is to fabricate the skin that acts as a restraint to prevent the structure from moving after it has been deployed. The material used is 0.2mm flexible PVC. The zip is sewn in, with an overlapping flap as a means of waterproofing. The skin is then stapled onto the plywood structure. Unzipping it allows the system to be folded again.

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In conclusion, rapid prototyping techniques were crucial to the exploration and development of this structural system, as the geometry as well as movement were difficult to model digitally. The use of 2D and 2.5D methods to fabricate components that were then assembled made it easier to visualize and understand the system.

Categories: AY 2012/2013 SEM 1