Volvo Pure Tension Pavilion

FROM COMPETITION WIN TO GROUND-BREAKING STRUCTURE IN 4 MONTHS

Pure Tension, the high-tech, portable solar-powered tensile membrane structuredesigned by Los Angeles-based Synthesis Design + Architecture, is the culmination ofmonths of design refinement, research, and engineering after the firm won Volvo’s“Switch to Pure Volvo” competition, organized by international architecture magazine THEPLAN this past summer.

The pavilion, commissioned by Volvo Car Italia for the new Volvo V60 plug-in hybridelectric car, not only charges the car but also flat-packs to fit in the trunk and assemblesin less than one hour. It is an experimental structure that, similar to a concept car, is aworking prototype that speculates on the future of personal mobility and alternativeenergy sources while also exploring digital design methodologies and innovative structuralsolutions.

For Pure Tension, digital design technologies were harnessed not only to create an iconicpiece of original design but also a vision for the future of transportation.

SDA won the international competition by fulfilling Volvo’s wishes for a portable, yet iconicstructure to showcase the V60 on a press trip through Italy. However, SDA strategicallyadded two key elements to the design that made it stand out: one was the lightweightfabric and aluminum structure that could be collapsed into the trunk of the vehicle anddeployed by two people with ease, the second element was a photovoltaic skin thatcharges the vehicle, essentially the first-of-its-kind portable charging station for a hybridcar.

LOCAL DESIGN/GLOBAL PROCESS

“We wanted to challenge the notion of solar power as something that is an additive pieceof engineering infrastructure,” says Synthesis founder and principal, Alvin Huang. “Thesolar panels became a design feature and design driver, rather than something appliedafter the fact. The goal was to balance utility with beauty,” he adds.

The pavilion is the result of a global effort with design and engineering being carried out inLos Angeles by SDA with Buro Happold engineers, fabrication being done by ChicagobasedFabric Images, solar panels being sourced from Ascent Solar of Texas. Thecompleted pavilion was then shipped to Italy to embark on a 9 month, multi-citypromotional tour starting with the launch event hosted by Volvo in Milan. The next stopfor the pavilion is the EcoMondo Trade Fair of Sustainable Material & Energy inNovember. Additional stops will be announced as they are confirmed. The tour will end atThe Plan Magazine's annual Perspective event in Venice next summer, coinciding withthe Venice Biennalle.

DESIGN, FABRICATION, AND DEPLOYMENTSDA

derived the original design geometry through a conceptual form-finding processknown as dynamic mesh relaxation. The mesh topology produced by SDA was thenfurther developed by Buro Happold, who provided an engineered form-finding processthat takes into account material properties to rationalize the contours. Engineeringrevealed that the SDA form-finding process was within 90-95% accurate with a maximumdeviation of about 2 inches. The continuous tensioned skin of pavilion is articulated bythree hierarchies of geometric pattern that collectively define the geometry and produce avisually engaging moiré effect.

The pavilion is an expression of the tensioned equilibrium between its elastic membraneskin and rigid perimeter frame. The perimeter frame of the structure is defined by 24 CNCbent aluminum pipes with swaged slip fit connections, while the skin is materialized as apair of vinyl encapsulated polyester mesh membranes with a zippered seam and spandexsleeves that wrap the frame. The entire pavilion collapses neatly into two 65”x15”x15” ‘B-cases’ and weighs 150lbs in total and can be assembled and taken down in justunder an hour by a team of two to three people.

252 lightweight flexible photovoltaic panels are embedded within an applied graphic incidence analysis on the structure that found the average annual solar incidence of theskin for 360 degrees of orientation and mapped PV locations to the areas of greatestaverage annual solar incidence. Additionally a MPPT (Maximum Power Point Tracking)controller is utilized to sample the output of the cells, and selectively disable those thatare not collecting enough energy, thereby ensuring that the pavilion is receiving as muchcharge as possible. The pavilion can recharge a fully depleted car in about 12 hours inoptimum sun conditions.

The target goal to achieve the minimum power required to charge the car was 300 wattsof power. The current skin is testing at about 450 watts of power on optimum sunconditions. The wiring of the PV panels is integrated into the seams of the fabric and feeda portable battery system which in turn charges the Volvo V60. Current estimates havethe pavilion recharging a fully depleted car battery in about 12 hours. Technicalrequirements for the charging of the V60 were developed in collaboration with the VolvoDesign Center in Camarillo, CA and solar consultant FTL Solar in New Jersey.

The collaboration between SDA and Fabric Images proved to be a match made in heaven. While SDA and BuroHappold focused on digital methodologies for determining the pavilions shape and engineered form, Fabric Images focused on a hands-on approach to form-finding through the development of scale mock-ups and prototyping the integration of materials and technology. The process relied heavily on the personality for the material and fabrication techniques that FI has developed through their years of experience in fabric architectural solutions. A very hands-on approach was applied to a highly empirical process of physical form-finding through these prototypes that allowed Fabric Images to use the digital models supplied by SDA and BH as the foundation for a series of fabricated form-finding tests where FI recreated the digital geometries in physical form to test them for various methods for identifying seam locations, connection details, and integration of the photovoltaic panels onto the shape of the overall form.

Fabric Images’ team of material engineers and designers utilized a tried and true material called Miller Mesh for the formation of the initial shape and the project’s requirement of a photovoltaic grid to be incorporated or applied within the patterning of the Miller Mesh. Fabric Images was unable to use traditional tensile patterning techniques for the output of the mesh panels. Because of this dynamic, BuroHappold and SDA’s digital form was exploded into non-uniform quadrilaterals to allow for the digital mesh to become successfully unrolled into hundreds of “quilting” tiles that were then cut on FI’s CNC fabric cutter. The tolerances were critical to holding the shape properly so small variances were built into each tile so that sewing adjustments could be made on the 1:1 scale mock-up.

Once Fabric Images had the 3” round aluminium frame erected, the technologically infused textile tiles were sewn together and stretched onto the frame in two mirrored sections. Once the slack of the funnels was shored-in through sewing modifications, and the envelope around the V-60 was achieved, Fabric Images dismantled the mesh skin in order to make offset measurements that defined the proper parameters for the amorphous photovoltaic panels to be fabricated.

The photovoltaic panels were produced in tandem with the production of the re-engineered mesh skin. The photovoltaic panels were attached to the skin via a substrate of a scaled-down series of “quilting” tiles cut from black vinyl. The photovoltaic panels were then wired together in parallel and its appendages fished through and concealed by fabric “conduits” along the perimeters of the “quilting” tiles.

Material Selection Textiles selected for the project were chosen because of their balance of performance and aesthetic appearance. The base material is a white mesh knit textile with ¼” hole openings named Miller Mesh. The 100% polyester fiber makeup of Miller Mesh means that the material is naturally resistant to microorganisms and insects. This version of the material has a #3 stiffener finish applied to provide additional dimensional stability while still maintaining some flexibility for transport and handling. The hole size allows for easy viewing through the space, allowing plenty of light penetration while still allowing for the creation of a dramatic flowing form.

A secondary material that is sewn to the solar panels and affixed to the Miller Mesh is a 15 oz/ linear yard fabric designed for long term outdoor awning use. Made from a vinyl laminated on a weft insertion scrim base of high tenacity filament polyester, Coastline Plus offers a high level of strength and dimensional stability. Coastline Plus will not shrink, sag, stretch, or start to pocket, unlike other awning fabrics. It is mildew, stain, and dirt repellent, also critical for a traveling outdoor environment. Coastline Plus in black has a similar luster and pattern on the backside to the solar panels. Given that all the panels were the same square size while the design called for skewed rectangles of a variety of sizes, the precision cutting of Coastline Plus allowed for replication of the design without compromising the performance of the solar panels.

A final textile that plays an important, though not as noticeable role in the completion of this project, is 45” Super Stretch Spandex. This material is utilized around the entire perimeter of the shape. Because of the organic nature of the structure, this pocket material allows a slight amount of elastic stretch for ease of fabric application. Made from 90% nylon and 10% spandex, this 9.9 oz.sq yard fabric acts as a large rubber band, snapping the piece in place around the perimeter frame.

The frame used for this project was remarkable in its simplistic design. All typical cross bracing was eliminated in the design stages and the frame was used only to hold the perimeter shape while the tensioned fabric made up the rest. A 3” round aluminum tube was selected for the strength of the wall thickness, the inherently lightweight nature of aluminum, and the ability to dissemble into smaller pieces easily for transport.

Patterning and Planning Without careful, detailed patterning, this project would not have been possible. Using Rhino, the design rendering was broken down into 600 pieces to essentially create a grand scale three dimensional quilt shape. The direction of the fabric for each of the pieces cut was important to insure even and accurate stretch. The shape of the pieces was vital to creating an implied grid pattern as part of the overall design. Each piece was given letter and number combination within the program that carried over into the actual assembly to keep the pieces organized.

Team members tirelessly worked with our modern manufacturing equipment to meticulously cut the pieces and label for sewing. The precision cutter insured that the tiles were all cut to exacting specifications, allowing for future duplication. A paper copy of the layout helped operators locate and label pieces correctly.

Construction Details Given the outdoor nature of the project, certain details were put in place to increase the strength and durability. A bonded, twisted, continuous filament nylon thread was selected for the stitching. The Tex 70 thickness was carefully chosen because of the combination of physical strength while being engineered to withstand needle heat and abrasion. This nylon thread is unaffected by mildew and rot. Beyond the butt stitching to attach the pieces together, a second top stitch was applied to provide additional seam reinforcement.

One detail that could easily be overlooked was the wire management. Each solar panel had to be hard wired together into a grid which could power the Volvo automobile. Since so much care was taken in the construction of the fabric and frame piece, it was extremely important to maintain a specific appearance which did not include clusters of white, blue, black and red wires running over the surface. To address this, the team constructed decorative, functional wire housings using a clear vinyl with an outer layer of Miller Mesh. The Miller Mesh outside provided a chameleon effect while the vinyl allowed the wires to easily be run through.

Always mindful of the need to assemble and dismantle the tensioned architecture, a zipper was placed along the entire run, dividing the cover into two pieces. Not only did this allow for easier assembly with only half the fabric lifted at a time, but also for easier packaging to reduce the chance that folding would occur in the solar panels. Also taken into consideration was the need to replace or remove the solar panels. Because of this, a special hardware piece was attached at the four corners of each vinyl panel and was inserted through the ¼” holes of the mesh for a secure, yet still flexible attachment.