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Solar Design Manual

Aluminum extrusion,a world of

opportunities

Solar_Design_Manual_8.qx_HydroTemp 7/3/12 6:33 PM

Aluminum — The material of the future

Aluminum has been described as the “materialof opportunity” and more and morecompanies in the solar industry are realizingthe obvious benefits of using aluminum.

A significant benefit of aluminum and thealuminum extrusion process is the almostunlimited opportunity to adapt the shape of theproduct to optimize performance, maximizestiffness and strength, and reduce the numberof parts to assemble and fabricate; all of whichcontribute to lowering cost. The low density ofaluminum can also ease handling andtransportation throughout the supply chain bycreating lighter weight components andassemblies. And, aluminum is highly durable,almost maintenance-free, and 100% recyclable.

As it relates to solar applications, aluminum’sunique properties include:

● High strength-to-weight ratio

● Very cost effective, with proper system design

● Excellent formability and ease of fabrication

● Excellent electrical and thermal conductivity

● Excellent resistance to corrosion

● Attractive surface finish

● Excellent reflector of light and heat

● Easy and economical recycling

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Table of Contents

Solar applications for aluminum extrusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4PV and solar thermal collector module frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Solar mounting systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Solar inverters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Solar thermal applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

PV solar frame & mounting system design considerations . . . . . . . . . . . . . . . . . . . . . 6

IBIS PV mounting structure analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Concentrating Solar Power (CSP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

IBIS CSP frame structure analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Solar thermal design considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Aluminum, the green metal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

The properties of aluminum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Aluminum alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Corrosion resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Types of extrusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Extrusion design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Joining options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Anodizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Hydro plant capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

North American resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30


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Solar applications for aluminum extrusions

Photovoltaic (PV) and solar thermal arraysdeliver efficient, environmentally-friendlyalternatives to fossil-fuel-based powergeneration. Technological advances have led tolower production and installation costs. Amongthese advances is the use of creative design withaluminum extrusion components in the framestructure and other areas of the solar array.

With the number of solar parks androoftop installations increasing, people arebecoming more concerned about the aestheticsand maintenance of the array structure. Ownersand operators are looking to solar as a source ofenergy while remaining as unobtrusive aspossible. Architects desire solar systems thatblend in with the rest of the building andsurrounding area.

Extruded aluminum frame structures meet orexceed the strength and flexibility requirementswhile delivering a lower lifetime cost comparedto steel frames, especially with a properlydesigned custom solution. Aluminum alsoprovides a high level of aesthetic appeal throughanodizing or powder coating to achieve thedesired surface finish. And, an aluminum framestructure will remain free of rust and resistantto corrosion for the life of the structure.

Long life, simple design, easy installation,and greater aesthetic appeal over the life of thestructure – combined with lower lifetime cost –makes aluminum the metal of choice for solar.

PV and solar thermal collector module frames

Solar mounting systems attach the solar panelarray to either the ground or rooftop forresidential and commercial applications. Forrooftop installations, a variety of frame designsare used depending on whether the system ismounted to a pitched or flat roof.

Aluminum ideal for rooftop weight limitationsExisting rooftops typically were not designed tosupport the weight of a solar installation. Butthe low density of aluminum helps to make asolar installation feasible, especially on thoserooftops that simply cannot handle the highweight of a steel frame structure.

Aluminum extrusions deliver superiordesign flexibility, high strength-to-weight ratio,excellent corrosion resistance and ease ofhandling and assembly – all of which areessential for a successful commercial rooftopinstallation. These characteristics makealuminum the metal choice for solar framestructures installed on carports, commercialbuildings and home rooftops.

Ground installationAluminum extrusions are ideal for PV and CSPconstruction because they provide:• Stiffness to maintain reflector geometry at all

times (CSP)• Strength to withstand the dead and live loads• Excellent durability and corrosion resistance• Ease of assembly• Lower Total Cost of Ownership

With aluminum, you gain a lightweightstructure that is easy to handle, transport, andinstall; a structure which is easy to maintainover a long life and resistant to the corrosiveeffects of weather. Aluminum is especiallydesirable for solar parks constructed overlandfills or other areas where escaping gases orother environmental impacts may corrode steelframe structures.

Solar mounting systems



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A solar inverter changes the direct current(DC) electricity produced by a photovoltaicarray into alternating current (AC). AC is thetype of current used in commercial andhousehold electrical applications.

Inverter cabinetsInverter electrical components are housed in acabinet that can be produced using aluminumextrusions for a cost-effective and highlyutilitarian result. Aluminum inverter cabinetsare lighter weight and offer greater designflexibility than steel cabinets. Aluminumextrusions deliver a faster prototyping capability.

With aluminum extrusions you gain theability to create complex enclosures using twoor more simpler extrusions. You can simplifyassembly and optimize product performancewith aluminum. Select your choice of a variety

of finish options, like anodizing. Certain finishattributes, like decorative grooves, can bedesigned into the extrusion. The end result is alower cost, corrosion resistant, lower weightcabinet that also offers the possibility of addingmore components without adding significantlyto the original weight.

Heat sinksHeat sinks are used in inverter cabinets todissipate heat. The efficiency of a heat sinkdepends on its ability to transfer heat quicklyaway from the components that requirecooling. Good heat transfer is achieved byusing materials of high thermal conductivitythat can be shaped to give high surface areas.Aluminum extrusions satisfy all of theserequirements, and can be integrated into thestructure.

Solar inverters

Aluminum extrusions offer a variety ofsolutions for solar thermal collectors andconnecting lines. For all absorbers, substitutingcopper tubes with aluminum gives immediatecost and weight advantages.

Plate and tube absorbersAluminum offers long life, ease of installation,high strength and low corrosion compared toother tube materials such as copper. Thealuminum alloys used to produce solarabsorber tubes meet or exceed all requirementsfor the solar absorber market with excellentflow rate and heat transfer properties.

High performance absorbers Using aluminum in solar absorbers provides theneeded flexibility to implement novel designsolutions (e.g. combining plate and tube).Micro-channel profiles may be assembled tomanifolds and coated to combine the functionsof heat absorption and fluid transport.

Connecting lines With interest in the use of aluminum inabsorbers increasing, it is natural to extend thisto connecting lines, where the cost advantagesare obvious.

Extruded aluminum tubing products havebeen proven for handling hot liquids in theautomotive, trucking, specialty vehicle anddefense industries, among others. Withaluminum tube connector lines, you will takefull advantage of the many proven propertiesof aluminum, including its ability to resistdamage in corrosive conditions, non-magneticand non-sparking, lightweight and highstrength. Aluminum delivers design flexibility,high performance, efficiency, reliability andlow cost.

Solar thermal applications

The extrusion process allows you toproduce components in many shapes and sizessuch as the closely spaced narrow fins requiredin heat sinks for heat dissipation. Incomparison to other materials the combinationof aluminum and shape results in lower costcomponents.



PV solar frame & mounting system design considerations

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Ease and speed of assemblyA good solar design optimizes the number ofparts that need to be fastened together on site,as well as assembly and training required for theinstallation team, lowering the total cost. Lowerlabor costs and fast installation are competitiveadvantages resulting from a proper designincorporating aluminum extruded components.You also will experience lower heavy equipmentcosts because lighter weight loads can behandled manually or by smaller machines,saving costs on cranes, front end loaders andother construction machinery. And lightweightaluminum extruded components ship for less.

Coatings and cosmetic appearanceUnder normal circumstances, aluminumextruded frame components left unfinished(mill finish) will outlast the 20- to 30-year lifeexpectancy of a commercial or residential roofand current solar panel technology. This isdue to aluminum’s natural resistance tooxidation and other environmental effects.Where aesthetics is a design concern, the useof a finish will add to the look of the solarinstallation. Common finishing techniquesinclude powder coat painting and anodizing inthe designer’s choice of colors, with powdercoating being the significantly more affordableoption.

Tight tolerance for mitering and corner jointsDesign your frame structure so that it snapstogether without gaps that would allowmoisture penetration. Aluminum extrudedcomponents can be designed for quick, easysnap-together construction with tight fittingjoints.

Adjustable PV frame designBecause the industry has not developed astandard size for solar panels, design yourframe structure to be adaptable for differentsize panels. An adjustable frame design givesyour solar panel vendor selection flexibility aswell as design adaptability. One of thestrengths of aluminum extrusion framecomponents is the ease with which they can beadapted to different size requirements. Forexample, the same extrusion profile can befabricated to different lengths and assemblyrequirements (holes, notches, etc.) at the plantfor ready-to-assemble delivery.

Racking and mountingDesign your racking and mounting structuresthat work with your frame to form a complete,unified structure. With a proper design, yoursolar system will work great and cost less.

Roof- and ground-mounted solar systems eachhave their own design issues.

Roof-Mounted Systems: Decide whether to use apenetration or ballast mount. A penetrationsystem places less weight on the roof structureand is suitable where weight is an issue. Yourdesign needs to be consistent with therequirements of the roof warranty to assure thatthe design doesn’t void the warranty. For thesereasons, penetration designs should be avoidedunless a ballast mount design is not possible.Ballast mount does not require penetration of



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the existing roof structure, but the ballasts doadd significant weight. Design considerationsinclude:

• Roof pitch• Frame structure angle• Ease of access to the roof for installation• Ease of access to the frame system for

maintenance and repair after installation• Existing roof hazards such as cables and

other obstacles

For most applications, the preferred roofdesign for solar is a ballast mount system witha low angle to minimize wind exposure.

Ground-Mounted Systems: Design your groundmount solar system to be adjustable fordifferences in land contours. In many cases, youmay want your system to be be self-leveling,especially for uneven areas like landfills wherethe ground will shift significantly over time.

Modularity & scalability Design your solar system to fit the spaceavailable and to expand as additional spacebecomes available. A modular system is easierto install and allows you to expand over time.

Clips, connectors, and fastenersIn your design, include a method for fasteningmodules to the frame and rack system. Alsoconsider how you will attach your system to aground post. Include a way to connect yourframe components together appropriate to theoverall design of your solar frame system. Sincespeed and ease of assembly are major costconsiderations, choose a joining method thatsupports quick installation with a minimum oflabor. Clips and connectors that facilitatequick, easy assembly can be included in yourcustom design with aluminum extrudedprofiles fabricated to your requirements.


EnvironmentAluminum is “the green metal” and offers anumber of advantages over steel for solarstructures. An aluminum frame will outlast thelife of the solar panel modules yet is costcompetitive with steel structures that will rustout before the solar panels wear out. This freesyou to design your solar installation for the lifeof the panels rather than the frame structure,giving you a significant competitive advantage.

When it’s time to replace your solarstructure, aluminum is 100 percent recyclable.But, environmental considerations start at thebeginning of the process with the raw materialused to extrude your components. Usingrecycled aluminum billet from Hydro reducesthe environmental impact of your project byreducing the impact of sourcing and processingraw metal out of the ground.


IBIS PV mounting structure analysis

Using information available in the publicdomain, IBIS Associates, an independent 3rdparty consultant, determined what it costs tofabricate, assemble, ship, and install PVmounting structures for two separate materialsystems; aluminum extrusions and galvanizedsteel. IBIS focuses on competitive positionassessments of traditional and advanced materialsand manufacturing technologies. Specificinstallation scenarios considered in the analysisinclude:

• Residential sloped roof-top system • Commercial flat roof-top system• Small utility-scale ground-mount systems• Large utility-scale ground-mount systems

ree specific cost factors were considered;system selection and components (rails,footings, clamps, etc.), fully burdenedinstallation labor, and shipping costs. Cost ofland and site preparation was not considered inground-mounted scenarios.

ConclusionsWhen taking into account the total cost ofmaterials, other components, shipping, andinstallation, aluminum is a more economicalalternative to steel in PV mounting structures,across all market segments. In addition to thisdemonstrated “initial” cost advantage, you canexpect structures built with aluminum extrusionsto have a lower Total Cost of Ownership,primarily as the result of lower on-goingmaintenance costs and substantially higherresidual value.

Other advantages of using aluminum extrusionsfor PV structures include:

• Low density & high strength-to-weight ratio• Low tooling costs and unlimited design

flexibility to optimize performance and reduce fabrication steps

• High corrosion resistance for superior durability, even in extreme environments

• Ease of recycling and high scrap value

* USGS Minerals Yearbook 2009 - Recycling Statistics

Recycling value comparisone aluminum system is nearly one-third themass of the steel design, but it has three timesthe residual scrap value upon decommissioning(see table).

A mere 5% of the original energy used inprimary aluminum production is needed toremelt aluminum products. Recyclingaluminum saves nearly 95% of the greenhousegas emissions associated with primaryaluminum production. And, aluminum can berecycled time and time again. Hydro usesprimary-quality billet from their owncasthouses with 70+% post-industrial recycledcontent. In contrast to steel, aluminum'sproperties never change.

50 Mega Watt System Aluminum Steel

Total Mass of Structure (lbs) 2,473,348 6,835,683

Scrap Price ($/lb)* $0.79 $0.09

Total Recycled Value $1,961,365 $635,719

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PV Mounting Structure Cost ($/W)

Aluminum

Commercial Flat Roof-Top

Steel Aluminum

Small Ground-Mount Utility

Steel Aluminum

Medium Ground-Mount Utility

Steel Aluminum

Shipping

Large Ground-Mount Utility

Steel

Labor

Contractor/Distributor/System Provider

Other Materials/Assemblies

Primary Material/Milling

For all systems compared, aluminum is the lower cost option



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Concentrating Solar Power (CSP)

CSP systemA CSP system is generally comprised of areflector, a receiver for collecting/absorbing thereflected and refocused solar radiation, alongwith support structures for the reflectors andcollector, and a suitable mechanism for trackingthe sun. In utility-scale CSP generation, thesolar field accounts for at least 50 percent of thepower plant’s total cost.

Solar Collector Assemblies (SCA), consistingof a rigid truss assembly, or space framestructure, to support the reflectors, receivers,and system for tracking the sun, constituteapproximately 25 percent of those costs.

While concentrating the sun’s rays relies onreflectors, it is the supporting metal architecture— trusses, frames, arches, etc. — that assuresreflector alignments and provides the strengthneeded to withstand common forces, stresses,movements, and wind loads, both for parabolashaped reflectors in troughs, and flat reflectorsfor solar towers.

Steel was used in the 1980’s for SCAsupport structures. However, new designs andfabrication techniques for aluminum haveprovided viable alternatives. State-of-the-artaluminum space frames in commercialoperations have achieved the multiple goals ofmuch higher optical efficiency, lower life-cyclecost, and minimal ecosystem disruption.

Although steel generally has a lower initialmaterial cost, aluminum outperforms steel interms of total cost; it is less expensive totransport and assemble and has advantages inoperations and salvaging. Advantages include:

• Ability to design extrusion to final shape• Lower cost and more precise machining• High strength-to-weight ratio • Ability to provide suitable support using

fewer parts • Reduced transportation and assembly costs • Faster assembly with accurate alignment and

movement in the field• High recycled content• Full recyclability at end of life

Structural needs A sturdy frame is essential to maintainingproper reflector alignment while supporting thesolar array structure against environmental andoperational stresses such as corrosion, movementand wind loads. In designing the solar framestructure keep in mind the necessity ofmaintaining optical accuracy with designefficiency. This requires a frame design thatincorporates the best practices includingminimal raw material consumption, leanmanufacturing practices, easy transportationand assembly, long life-cycle and minimized life-cycle costs. Your design should also consider thestructure’s impact on local environment.



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The frame structure needs to incorporatethe following characteristics: Stiffness – rigid frame structure for high optical efficiency Motion – high angular tolerance consistent with tracking requirementsStrength – to withstand dead weight and loads required for tracking the sun’s movement Modularity –with an optimized number of components consistent with size, transportation,assembly, and site conditions Ease of fabrication –lightweight design that considers transportation and assembly on site O&M – high mean time between repairs or replacement of components

All forces acting on a collector must betransmitted through the support framework orauxiliary structures and be dissipated into theground. In early support designs, it was deemedimperative to use heavy steel structural membersto maintain the stiffness and geometry of thecollector at all times. Recent advancements inaluminum space frame design have, however,debunked that notion.

Life-cycle cost While support-structure designs, strategies andtechnology advancements have pursued the goalof lowering the cost of the solar collectorassembly, many solar developers have beenreluctant to move away from using steel in thesupport structures.

This reluctance can be attributed to theassumption that steel is cheaper than aluminum,or other materials, and that heavy weights areneeded to combat the various loads that canimpact collectors. Though material costs toproduce solar mounting systems in steel aregenerally lower than those of aluminum, theinitial cost advantage is mitigated by severalfactors. Aluminum made with recycled contentuses significantly less energy to produce, yet theproduct shows no loss in performancecharacteristics. The lighter, rigid aluminumalternatives provide significant savings in termsof design flexibility, labor, transportation, timeto install, accuracy, and related gains inelectricity generation.

Frame design historyIt wasn’t until 1981 and 1982 that IEAdemonstrated a larger solar-electric parabolictrough. Luz pioneered two steel-basedarchitectures for supporting trough collectors, atorque tube and a V-truss structure.

A torque tube-based structure consists of along tubular substructure to provide torsion andtension stiffness, connected to a cantileversubstructure mounted to and supporting thereflectors. The torque tube design providedadequate optical performance and torsionresistance, but the raw materials, transportationand assembly (including welding and specialtyjigs) resulted in higher cost.

The V-truss structure provided the rigidityand strength to withstand loads, compressionand twisting forces, but it did not significantlyimprove optical performance. It also displayedinadequate torsion resistance and did not lowermanufacturing costs as much as expected.

Sener and a EuroTrough consortiumindependently evolved second-generationsystems in an attempt to improve opticalefficiency, manufacturability and costs. TheSener design used stamped cantilever arms toconnect to the torque tube instead of weldedtube profiles. Stamping helped Sener lowermanufacturing and mounting costs, butassembly still required costly welding ofauxiliary components to the tube, therebydiminishing the gains.

The EuroTrough torque box designutilized a rectangular central frame with asquare cross-section and cantilever arms toresist bending, twisting and various loadstresses while maintaining reasonable opticalperformance. This design provided torsionalrigidity that allowed longer troughs to bedeveloped and allowed longer collectorsoperated by a single drive.



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Concentrating Solar Power (CSP) continued

These two second-generation designs haveachieved reasonable optical performance and lesscollector deformation, but manufacturing,transportation, and erection costs have notdropped significantly. Steel frame constructionstill requires huge cranes, welding, special jigs,and many man-hours.

State-of-the-art aluminum frame designThe newest generation trough supportstructures with dramatic improvements in allaspects of the design and operationrequirements is the Solargenix (later Acciona)-Gossamer-Hydro all-aluminum space framewith hub connectors that was first put inoperation on Nevada Solar One.

The first generation all-aluminum spaceframe was envisioned by Solargenix under theU.S. Department of Energy’s USA TroughInitiative and through a cost-shared R&D

contract with NREL. The resulting collectorand supporting structure provided valuableinsights and led to the second-generationdesign, which was commercialized.

Located 30 miles outside Las Vegas, NS1has a nominal production capacity of 64 MWwith a maximum capacity of 75 MW. Its annualproduction is 130,000 MW. It was built in just16 months at a cost of $266 million. It cameonline in June 2007.

It’s 300 acres of solar fields comprise 9,120space frames supporting 760 parabolicconcentrators with more than 180,000 mirrorsthat concentrate the sun’s rays onto 18,240 solarreceiver tubes located on their focal line. The frames were manufactured from more than7 million pounds of extruded aluminum with70-80 percent recycled content.

The performance facts as reported byNREL for the extruded aluminum trough

versus the most advanced competitive designincludes: • 50% fewer parts • 30% less weight• 1/3 assembly time required compared to

conventional frame systems• No post-construction frame or mirror

alignment required

Performance assessments showed acombined “slope error” (mirror error plus framealignment error) standard deviation of less than2.0 milliradian, enabling improvement infocusing of up to 38 percent over NREL’srecommended 3.0. This means the collectortroughs are operating near theoretically perfectperformance. The net effect is an annual outputincrease of 4 percent, or approximately 2.5 MW.



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IBIS CSP frame structure analysis

Using information available in the publicdomain, IBIS Associates performed anindependent detailed analysis of various existingparabolic trough CSP (Concentrated SolarPower) frame designs from steel and aluminumused for utility scale solar power applications.

Material, fabrication, transportation andfield assembly costs were estimated and vettedfor use in this study. e included excerpts fromthe IBIS analysis are useful in understandingwhy aluminum extrusions represent acompetitive advantages in both total installedcost and performance.

• IBIS focuses on competitive position assessments of traditional and advanced materials and manufacturing technologies

Design comparisons

• e Eurotrough, Skal-ET 150, HelioTrough, and SenerTrough steel-based systems were compared to a “standardized” aluminum-extrusion design using public data available for the Acciona/FP&L CSP structures

• IBIS created parts and material processingmodels for the aluminum extruded and galvanized steel frame designs, detailing components/materials/processes and modeling the costs associated with these elements

• e results were validated via external expert review

• e results are a strategic cost analysis (not a final “price” analysis, as it does not include SG&A costs nor profit)

Eurotrough/Skal-ET 150Developed by a consortium of industry partnersand supported by the European commission, theSkall-ET 150 is a scaled-up design whichreplaces square tube sections with angle sections.

Collector length: 12 mAperture width: 5.77 mTotal aperture area: 69.2 m2

HelioTrough A torque-tube design with the center of gravitybelow the mirror surface provides gapless SCA(no mirror gap across the pylons)

Collector length: 19.1 mAperture width: 6.77 mTotal aperture area: 129.3 m2

SenerTrough A torque tube design utilizing stampedcantilever arms made from electrogalvanizedsheet (reducing galavanting costs)


Standardized aluminum extrusion frame A scaled-up version of the Acciona/FP&L eightmeter design with a wider aperture


Number Mass Structure Steel of Pieces lbs (kg) Surface Area (sq ft)

Eurotrough 390 2667.5 (1209.8) 1240.7 ~ 18 kg/m2 of aperture

Skal-ET 150 390 2684.9 (1217.6) 1025.2 ~ 18 kg/m2 of aperture

HelioTrough 678 5918.3 (2684.1) 2292.6 ~ 21 kg/m2 of aperture

SenerTrough 87 3604.0 (1634.5) 551.6 ~ 21 kg/m2 of aperture

Aluminum Extrusion 179 1628.9 (738.6) 24.6 ~ 10.7 kg/m2 of aperture



Cost modeling methodologye following cost estimates are built from thebottom up and consider all variable and fixedelements of each of the operations required tofabricate, assemble, and install solar thermalparabolic collectors. ese are directmanufacturing costs that would be incurred by acompany that is completely integrated from rawmaterial acquisition to final field installation.ere are no SG&A costs nor profit added tothese estimates.

e aluminum extrusion-based design requiresfewer manufacturing/finishing steps and a morestraightforward, lower cost, assembly operation.

Comparative manufacturing and assembly process flows

Scenario comparison / breakdown by category / cost per unit area

Projected collector cost over market historySteel costs less than aluminum on a per poundbasis, but comparable frame solutions usingaluminum weigh approximately 1/3 that ofsteel. Using aluminum extrusions for the framestructure provides cost and performancebenefits which far outstrip the pure materialcost differences. Despite fluctuating materialcosts, at no time from 1991 through 2011would the comparative prices of steel, zinc andaluminum extrusions have resulted in a casewhere the cost of the extruded aluminumframe would have been greater than thegalvanized steel frames.

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IBIS Associates CSP frame structure analysis continued



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Absorber plate

Solar glass

GrommetGlazing seal

Insulation

Absorber tube

Aluminum backsheet

Aluminum frame

Manifold

Solar collectors use the heat from the sun toproduce hot water. Flat plate collectors are thedominating solar thermal technology. Typically,the sides and backs of these collectors are madeof aluminum. Over the past few years,aluminum has displaced copper as the preferredmaterial for absorber sheets. Recently,aluminum absorber tubes have entered themarket.

While the thermal conductivity is higherfor copper than aluminum, it is the heat transfercoefficient that is more relevant in thermalsystems. The heat transfer coefficient explainshow much heat that may be transferred per unitarea and is measured in W/(m2K).

Warping is a known phenomenon inwelded assemblies. Being consistent whenchoosing materials, such as aluminum sheetsand tubes, significantly improves the quality ofan absorber. When copper tubes are welded toan aluminum sheet, the absorber becomeswarped as the absorber's temperature increases.This is due to the difference in the twomaterials’ thermal expansion coefficients.Different materials expand at different rates asthe absorber’s temperature increases, therebywarping the absorber and subjecting the weldingpoints to material stress.

Designing aluminum systems againstcorrosion requires matching alloys appropriatelyas well as taking precautionary measures tomaximize the life expectancy of the system.Aluminum as a stand-alone material is resistanteven to aggressive environments, includingseawater conditions. When designing a solarthermal system, there are two main types ofcorrosion to consider.

Internal corrosionTo secure the system against internal corrosion,Hydro recommends an alloy which is corrosionresistant. Also, the system needs to be a closedsystem (hermetically sealed) that contains a heattransfer fluid containing an inhibitor. An opensystem, or a system with fresh water without aninhibitor, will corrode. Most commerciallyavailable heat transfer fluids contain inhibitors.We also only recommend the use of aluminumor stainless steel fittings in hot areas (i.e. at the

absorber). We do not recommend brass fittingsin these areas since brass contains zinc. This isbecause zinc introduces corrosion in a solarthermal system at high temperatures.

External corrosionThere are mainly two areas of risk for externalcorrosion, at joints to copper or brass fittings, orat joints between the absorber tubes and sheet.External galvanic corrosion may occur betweenaluminum and other metals if water is allowedto condense on the joint area.

To avoid corrosion where aluminum isdirectly joined to copper or brass fittings, it isgood practice to protect the joint area with asuitable coating against outside moisture.

To avoid corrosion between the absorbertubes and sheet, it is important to select theright alloy combination for the aluminumabsorber plate and tube. The tube has to beslightly more noble than the plate in order toguarantee that any potential material sacrifice isof the plate and not tube. The larger thedifference in material nobility, the higher therisk that the less noble material will sacrificeelectrons to the more noble material,introducing corrosion. Thanks to lowerdifferences in potentials in an all-aluminumabsorber, compared to an absorber with coppertubes and an aluminum sheet, the overallcorrosion risk is reduced and a longer collectorlifetime may be obtained.

Good welding is essential for the absorberto perform well under working conditions.

Laser weldingTests of laser welding aluminum tubes toaluminum sheets have confirmed that lessenergy is needed compared to welding coppertubes to aluminum sheets. Process times havebeen reported to be reduced by as much as 20-30%.

Ultrasonic weldingUltrasonically welding copper tubes toaluminum sheets is delicate and difficult, and sofar only the very best ultrasonic welders havemanaged to weld the two materials together.This has kept many absorber manufacturersfrom switching to aluminum sheets and theycontinue to produce expensive all-copperabsorbers. With the introduction of aluminumtubes, absorber manufacturers with ultrasonicwelding equipment may also switch toaluminum sheets without having to changewelding equipment.

Continuous Step Welding (CSW)CSW is a new welding technology that uses verylow amounts of energy and also deforms thetubes to introduce turbulence.

Solar thermal design considerations


For more information on specialized alloys, go to: www.hydro.com/en/Subsites/Hydro-Aluminium-Precision-Tubing/Solar-aluminium-products-solution/Competences-solar/solar-tests


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Aluminum, the green metal

Aluminum is often called the green metal because of its inherentcharacteristics and the ease with which it can be recycled, using only afraction of the energy required to make primary aluminum.

A mere 5% of the original energy used inprimary aluminum production is needed toremelt aluminum products. Recyclingaluminum saves nearly 95% of the greenhousegas emissions associated with primaryaluminum production. Today, aluminumrecycling now saves close to 170 million metrictons of greenhouse gas emissions per year.

And, aluminum can be recycled time andtime again. In contrast to many othermaterials, aluminum's properties never change.Of an estimated total of around one billionmetric tons of aluminum produced in theworld since commercial manufacture began inthe 1880s, about three quarters is still inproductive use. Recycling the metal currentlyin use would equal up to16 years’ primaryaluminum output. The global inventory ofaluminum in use has grown from 90 millionmetric tons in 1970 to about 600 millionmetric tons today and is forecast to reach morethan 1 billion metric tons in 2020. This iscreating a vast material and energy storagebank for future recycling use.

Aluminum’s light weight and overallexcellent in-use performance ensures that the

life-cycle of many products are enhanced. Thelow density of aluminum benefits thetransportation, aviation, and aerospaceindustries because lighter structural systemsresult in lower fuel consumption. For example,every kilogram of aluminum that is used insubstitute for heavier materials in a car or lighttruck, has the potential to avoid the release of20kg of CO2 over the lifetime of the vehicle.

As society’s demand for “green” productsincreases, recycled aluminum will become aneven more important material source. Today,aluminum is the most commonly recycledpost-consumer metal in the world. Recyclingaluminum makes environmental sense and italso makes good economic sense. Productsbuilt with aluminum extrusions can have alower life-cycle cost and provide full end-of-liferecyclability.

Using proprietary remelt technology,Hydro is the leading supplier of aluminum billetin North America and produces primary-grademetal which contains more than 70% recycledcontent. Our extrusions, produced using Hydroremelt billet, are ideal for “green” applications,like solar.

• Hydro recycled about 275 million pounds of aluminum in 2011 in North America

• Our 6000 series alloy has > 70% recycled content

• Recycling is the path to reduced carbon footprint

• Recycled aluminum is excellent for LEED related building products or for any product with a “green” aspect

Sources of aluminum — Recycling is the path to reduced carbon footprint

Primary

Content of Hydro 6000-Series Extrusion Billet

Post-consumer

Internal scrap

Other external

28%

30%

22%

20%



17

Carbon footprint - Emissions per metric ton (MT) of product

Using aluminum with high recycled content hasa smaller impact on the carbon footprint ofproducing the material.

Hydro's Extrusion North America unit sources billets for our extrusion facilities andexternal customers from our own network of three remelt casthouses. Thesecasthouses, located in St. Augustine, FL, Monett, MO, and Phoenix, AZ, utilize state-of-the-art and proprietary technology to produce primary-quality extrusion billet with highrecycled content.

In 2011, these facilities used in their production close to 275 million pounds ofrecycled aluminum — 20 percent more than in 2010 and 32 percent more than in 2009.Nearly 20 percent of last year’s amount was post-consumer material, with theremainder coming from pre-consumer scrap from our casthouses and extrusion plants,our customers, and other extruders. The scrap content of 6000-series alloy billet weproduced in 2011 was around 70 percent.

Through technology and practical improvements, Hydro’s Extrusion North Americaunit is committed to increasing its share of the goal that Hydro has set for its globaloperation: To recycle 1 million metric tons of contaminated and post-consumer scrapannually by the year 2020.

2012 Recycled Content Declaration

Aluminumglobal average

Steel Aluminumglobal average

Steel

CO2/MT aluminum product equivalent

Recycling based

CO2/MT aluminum product equivalent

Primary based(no recycling, no hydro power)



18

The properties of aluminum

Weight - Aluminum is light with a density onethird that of steel (0.097 lbs/in3).

Strength - Aluminum is strong with a tensilestrength of 10 to 100 KSI, depending on thealloy and manufacturing process. Extrusions ofthe right alloy and design are as strong asstructural steel.

Elasticity - The Young's modulus for aluminumis a third that of steel (10,008 KSI). This meansthat the moment of inertia has to be three timesas great for an aluminum extrusion to achievethe same deflection as a steel profile.

Formability - Aluminum has good formability,a characteristic that is used to the fullest extentin extruding, facilitating shaping and bending ofextruded parts. Aluminum can also be cast,drawn, and milled.

Machining - Aluminum is very easy tomachine. Ordinary machining equipment suchas saws and drills can be used along with moresophisticated CNC equipment.

Joining - Aluminum can be joined usingnormal methods such as welding, soldering,adhesive bonding, and riveting. Additionally,Friction Stir Welding (FSW) is an alternative incertain applications.

Corrosion resistance - A thin layer of oxide isformed in contact with air, which provides verygood protection against corrosion even inextremely corrosive environments. This layercan be further strengthened by surfacetreatments such as anodizing or powder coating.And corrosion resistance can be enhancedthrough alloy selection.

Reflectivity - Aluminum is a good reflector oflight and heat.

Thermal conductivity - Thermal conductivityis very good even when compared with copper.Furthermore, an aluminum conductor has onlyhalf the weight of an equivalent copperconductor.

Electrical conductivity - When compared tocopper, aluminum has good electricalconductivity.

Linear expansion - Aluminum has a relativelyhigh coefficient of linear expansion compared toother metals. Differences in expansion can beaccommodated at the design stage, or inmanufacturing.

Aluminum has a unique and unbeatable combination of properties thatmake it versatile, effective, and attractive for a vast array of applications



19

Deflection f=P*L3/(48*E*I)

Steel Aluminum Wood

Modulus of Elasticity 30500 ksi 10,000 ksi 1,600 ksi

Moment of Inertia 2.4 in 4 7.9 in 4 5.3 in 4

Weight 4.5 lb/ft 2.0 lb/ft 2.35 lb/ft

Properties of materials

*6000 series

Aluminum* Copper Steel 371 Plastic

Strength (ksi) 36 36 58 7

Density (lbs/in ) 0.097 0.32 0.28 0.05

Melting point °F 1110-1210 1980 2730 180

Electrical conductivity (% IACS)

3

50 95 12 -

Heat conductivity (Btu-in/ft hr°F) 1390 2780 527 1.04

Non-magnetic Yes Yes No Yes

Weldable Yes Yes Yes Yes

2



20

Aluminum alloys

Pure aluminum is only used in a limited waycommercially. The majority of extrusions aremade from aluminum alloyed with otherelements. The most common elements used aremagnesium (Mg), silicon (Si), manganese (Mn),zinc (Zn) and copper (Cu). Most aluminumextrusions are made from the alloy series listedbelow:

1000 series Al 3000 series Al + Mn 5000 series Al + Mg 6000 series Al + Mg + Si7000 series Al + Zn + Mg

The 1000 series is non-heat-treatable.These alloys are often selected for productswhere high thermal and electrical conductivityare desired. They have low strength.

The 3000 and 5000 series are non-heat-treatable. 3000 series is often used in drawntubing for highly ductile applications andprinter components. The 5000 series is mostlyused in extremely corrosive environments suchas marine.

The 6000 and 7000 series are heat-treatable. They are the most commonly usedextrusion alloys and have a wide range ofapplications.

6000 seriesThe 6000 series is the primary alloy used forsolar applications. It has good extrudability andcan be solution heat-treated during hotworking at the extrusion temperature. Solutionheat treatment enables some of the alloyingelements, such as Mg and Si, to go into solidsolution and be maintained in a supersaturatedstate on quenching. This homogenous materialis subsequently age hardened to obtain therequired mechanical properties.

The 6000 series alloys are termed “softalloys”. They are easy to weld and offer goodresistance to corrosion. The bulk of extrudedmaterials are for load bearing applications.

Among the 6000 series, the 6060 alloyoffers low to medium strength and is easy toextrude even for complicated cross-sections. Ithas good formability during bending in the T4condition. This material is highly suitable for

The choice of material is a critical decision in all product development.

Aluminum can give a product suitable physical and mechanical properties

and, at the same time, help achieve an aesthetically attractive appearance.

AIZn Zinc

Cu Copper

MgMagnesium

MnManganese

SiSilicon

Increased strengthand hardness.

Possibility for stresscorrosion. Gives heattreatable alloys when

combined with Mg.

Gives heat treatablealloys. Gives increasedstrength and hardness. Reduced resistance to

corrosion.

Increased strengthand hardness. Good corrosion resistance, increased weldability.

Gives heat treatablealloys when combined

with Mg. Good corrosion resistance.

Increased yieldand tensile strength.Good resistance to

corrosion.

+

Properties that can be achieved when alloying with other metals



21

anodizing, both for decorative and protectivereasons.

The 6005A alloy has higher strength than6063 but is slightly harder to extrude. 6005Ais relatively less ductile than 6060/6063 alloysin the heat-treated condition. It is suitable foranodizing for protective purposes but thequality of the surface makes decorativefinishing more difficult. 6105 is an alloy ofsimilar chemical composition to 6005A but isconsidered less robust for demanding medium-strength applications.

6061 and 6082 alloys provide high strengthand are suitable for extrusion of cross-sectionsthat are not too complicated. With its superiormaterial performance characteristics, 6082 canoften replace 6061. The material is suitable foranodizing for protective purposes.

Temperature – mechanical propertiesCare should be taken when using aluminum athigh temperatures. Mechanical properties canbe significantly reduced at temperatures above250°F, especially if the material has been ther-mally hardened or cold worked. Fortunately,

extended exposure above 250°F is rare in gen-eral extrusion applications. When such expo-sure is anticipated, ensure that the componentis not structural or load bearing. For suchapplications, specialty alloys in the 3000 or7000 series should be considered.

In general, the 6060, 6063, 6005, 6061and 6082 alloys should not be used instructural applications which experiencetemperatures above 250°F. The tensile strengthdecreases as the temperature increases whileelongation before fracture usually increases.

Low temperature properties In contrast to steel, aluminum alloys do notbecome brittle at low temperatures. In fact alu-minum alloys increase in strength and ductilitywhile impact strength remains unchanged. Asthe temperature decreases below 32°F, the yieldstrength and tensile strength of aluminumalloys increase.

6005A

6105

6061

As seen above, some alloy groups overlap. Although different in name, chemical composition and properties canbe the same or similar. 6060 and 6063 are lower strength alloys of comparable performance. 6105 and 6005are similar, medium-strength alloys. 6061 and 6082 are high-strength structural alloys.



Although aluminum is a chemically-activemetal, its behavior is stabilized by theformation of a protective oxide film on thesurface. Generally, this film is stable inaqueous solutions with pH 4.5-8.5. Furtherconsiderations need to be made if the pHexceeds these limits or if the environmentcontains chloride. Although generally verystable, aluminum alloys can experience certaintypes of corrosion as summarized below:

Uniform attack Corrosion proceeds homogeneously over thewhole surface of the metal. With aluminumalloys this type of corrosion is mainly seen invery alkaline or acid environments where thesolubility of the natural oxide film is high.

Pitting corrosionPitting corrosion is the most common type ofcorrosive phenomena with aluminum alloysand is characterized by local discontinuities inthe oxide film (i.e. locally reduced filmthickness, rupture, localized concentrations ofimpurities/alloying elements, etc.) Aluminumis sensitive to pitting when chloride ions arepresent (e.g. sea water). Pits develop at weakspots in the surface films and at places wherethe oxide film is mechanically damaged.

Pitting can penetrate several millimetersduring a short period of time if the conditionsare extremely poor. The pits can be of differentshapes, wide or narrow. Narrow pits areundesirable since the pits could be deep anddifficult to detect.

Choosing the right alloy and proper surfacetreatment (e.g. anodizing, powder coating orelectrostatic painting) are two ways to limit orprevent pitting corrosion. Frequent cleaning,as well as ventilation of tight assemblies and aprofile design which reduces the accumulationof stagnant water, are also recommended.

InterGranular Corrosion (IGC)

IGC is selective corrosion around the grainsand in the adjacent zones without anyappreciable attack on the grain itself. Thereason for IGC is a difference in corrosionpotential between grain boundaries and thebulk of the immediately adjacent grains. Thedifference in potential may be caused by thedifference in chemical composition betweenthe two zones. This situation may, for example,develop as a result of slow cooling afterextrusion. In this case, the grains will be largerand the inter-metallic particles will precipitateon the grain boundaries, thus increasing thedifference in corrosion potential between thegrain boundaries and the interior of the grain.

Due to low metal consumption, inter-crystalline corrosion is difficult to detectvisually and even more difficult by measuringweight loss. However, if the corrosion ispermitted to propagate into the metal, themechanical properties of the material willseverely deteriorate.

Alloys in the 6000-series are normallyresistant against IGC, although this isdependent on the chemical composition.Recrystallized structures which already have ahigh content of Si or Cu, may allow corrosionof this type. Addition of Mn or Cr will preventor minimize recrystallization.

One way to prevent IGC is to choose theright alloy. Other preventative actions arementioned under "Pitting corrosion."

Crevice corrosion Crevice corrosion may occur in narrow crevicesfilled with liquids like water. Use of a sealantprior to joining may prevent moisturepenetration. A good extrusion profile designwill minimize the risk of crevice corrosion.

Corrosion resistance

One of the principal reasons for choosing aluminum for structural

applications is its high corrosion resistance.

22



Water staining is a type of crevice corrosion andis caused by water or moisture trapped between,for example, dense stacked profiles. Waterstaining is a very common corrosion type.Appearance varies from iridescent in mild cases,to white, grey or black in more severe instances.Water staining is normally removed by grindingor painting.

Because of the risk of condensation,profiles without any surface treatment shouldnever be stored outdoors, even though plasticwrapping is used. Store extrusions in places witha relative humidity of 45% maximum, and amaximum temperature variation of +/-40°F.During transportation from a cold to a warmarea, the temperature should be increasedgradually to avoid condensation.

Galvanic corrosion Galvanic corrosion occurs when two metallicmaterials are in contact in the presence of an

electrolyte forming a galvanic cell. The leastnoble material (the anode) preferentiallycorrodes while the more noble material(cathode) is protected. Since aluminum is moreanodic than most commonly used constructionmaterials, with the exception of zinc,magnesium and cadmium, this can be a seriousform of corrosion with aluminum.

Coupling aluminum with a more noblematerial can seriously deteriorate the protectiveeffect from the oxide layer. This is especiallydangerous in atmospheres or water with highconcentrations of chlorides or other aggressivecorrosives.

Most types of aluminum corrosion are theresult of some kind of galvanic coupling with adissimilar material.

Galvanic corrosion can be avoided orminimized by taking the following actions:Avoid using materials with large galvanicpotential differences in a particular environment(stainless steel not included). If that is not

practical, different materials have to be properlyelectrically insulated. It is very important to useinsulation material of proper electrical resistanceand to avoid metallic contact in the entireconstruction. This can be checked withresistance measurement instruments such as amultimeter.

Aluminum may also be protected by meansof sacrificial anodes.

The most cathodic material can be surfacetreated with a metallic coating (Al/Zn), organiccoating (lacquer, paint, plastic, rubber) or aspecial coating for screws and bolts. Surfacetreatment has to be carried out correctly andnot done only on the anodic material. As aconsequence, a defect in the surface coatingmay generate a very unfavorable cathode/anoderatio (a big cathode area in relation to a smallanode area gives considerable corrosion).

Galvanic corrosion in combination withcrevice corrosion may be especially damaging.Avoid entrapment of liquids in crevices betweenmaterials of various galvanic potentials.

Also avoid the transfer of ions of galvanicmaterials on aluminum surfaces. For instance,droplets from a copper tube on an aluminumsurface will generate precipitation of coppermetal. The result is corrosion of aluminum(deposition corrosion). The next step will bemicrogalvanic corrosion between aluminum andthe copper particles in the aluminum surface.Severe pitting may occur within a few weeks.

The atmosphere Corrosion is insignificant in fresh, unpollutedair. Aluminum does not corrode where there arehigh levels of sulphur dioxide but can becomedark or matte in appearance.

Water Pitting can occur in stagnant water. Thecomposition of the water is the important factoras the presence of copper, calcium, chloride andbicarbonate ions increase the risk significantly.

Seawater Alloys containing silicon, magnesium andmanganese show good resistance to corrosion inseawater. Copper alloys, on the other hand,should be avoided.

Soil The resistance to corrosion is, to a great degree,dependent on the moisture in the soil and itspH level. Aluminum surfaces which may comeinto contact with soil are best treated with athick layer of bitumen or a powder coating.

AcidsThe majority of inorganic acids have a verycorrosive effect on aluminum, except nitric acid.High temperature, high acid concentrations andhigh levels of impurities in the aluminumincrease the rate of corrosion significantly.

AlkalisStrong alkalis are very corrosive. Sodiumhydroxide reacts violently with aluminum. Therate of corrosion can be reduced in

environments where the pH is between 9 and11 by using silicates. Wet cement has a high pHand therefore corrodes aluminum alloys.

Organic compounds Aluminum is highly resistant to the majority oforganic compounds. Corrosion can occur,however, with certain anhydrous liquids.

Other materials In practice, the corrosion problem caused bycontact with other materials is, for the mostpart, small. The natural oxide layer usuallyprovides sufficient protection.

Water staining

Corrosion resistance in different environments

23



Solid extrusions

The shape is described as a solid if it does nothave voids and is neither a hollow nor semi-hollow.

Semi-hollow extrusions

A shape is described as a semi-hollow if apartially enclosed void exists anywhere in itscross-section.

Hollow extrusions

A shape is described as a hollow if a completelyenclosed void exists anywhere in its cross-section.

Types of extrusions

Extrusion design

To achieve a successful product design, an understanding of some basic

extrusion design concepts could be very useful.

Uniform wall thicknessUniform wall thickness within a sectionreduces the load on the die and minimizes therisk of damage to the die. Major differences inwall thicknesses within a section should also beavoided in order to minimize differences insurface appearance after anodizing.

SymmetryWith symmetrical extrusion designs, abalanced flow of material through the die isachieved. At the same time, the load on the dieis evenly distributed. The extrusion shape is,therefore, more accurate while the risk ofdamaged dies is significantly reduced.

Rounded shapesAs a rule, all corners should be rounded.Normal radii are .016" to .040". If the designrequires sharper edges and corners, a radius of.008" is the smallest that can be effectivelyproduced.

24



Simplify and facilitateHere are some design changes that have noimpact on extrusion function, but which simplify and facilitate production, loweringproduction costs and improving cost efficiencies.

Fewer cavities cut costs For certain applications, converting to ahollow extrusion can increase strength andprovide better dimensional control

Increased size can cut weight and increaserigidity

HeatsinksIncorporating flanges in the design increasesthe surface area of the extrusion and improvesthermal conductivity.

Decorative lines Decorative lines in an extrusion can concealirregularities as well as protect against damageduring handling and fabrication.

25



Snap joints The elasticity of aluminum makes it ideal forsnapped joints. Snap joints are highly effectiveat joining two or more extrusions, allowing foreasy separation to give access to internalcomponents.

Designed properly, this joining technique isideal for many applications. For example,many extrusions can be snapped together tocreate a whole panel. Large extrusions thatcannot be produced as a single unit can bemade as two parts and then snapped together.

When designing snap connections, be sureto consider the risk of permanent shape changewhen the material loses its elasticity. Thisapplies especially to connections that arefrequently joined, separated and rejoined. Insuch cases, plastic clips, steel springs or similarconnections should be used.

Creating enclosures

When joining one extrusion to another, theycan either be slid together longitudinally inspecially designed tracks or snapped together.Locking options include specially designeddeformations, screws, or cylindrical plugs.

Cabinets and other enclosures are oftenbuilt by sawing an extrusion and then joiningthe two halves together. They are lockedtogether by fitting a cover. This techniquemakes for easier assembly of electroniccomponents. It also reduces die costs sincesolid aluminum extrusions can be used, whichare easier to produce than hollow extrusions.

Joining options

26



Hinges Aluminum extrusions provide manyopportunities for designing integrated jointsand hinges. Correct design can give amovement of 90° without any need formachining. Screw grooves can also be designedinto the extrusion for later assembly andconnection of other parts.

One very practical solution is a gearedhinge assembly where two curved gearlikeextrusions interweave within a protective thirdextruded housing to form a unique hinge.

Formed jointA formed joint can be a good solution if apermanent joint between two extrusions or anextrusion and another material is required.Long sections that are too wide to be extrudedcan be produced by rolling two extrusionstogether to the required dimension. Aluminumis excellent for this application as it can beeasily manipulated without detriment to formor function.

Butt joint Butt joints can be made by using guide pins orscrews along the length of the extrusions.

Sleeve joint A sleeve joint gives a more durable andpermanent joint.

Corner joints

Extruded corner cleat

Extruded 3-D corner cleat

Simple joining of two extrusions that are screwed,riveted or bonded

27



Anodizing is an electrochemical process thatcreates a significantly thicker layer of oxidethan occurs naturally. This provides protectionagainst mechanical wear and corrosion at thesame time as electrically insulating the surface.

The process involves placing the extrusionin an electrolyte bath with a DC current wherethe extrusion acts as the anode (hence thename). When the current is applied, a thickoxide layer is formed, which becomes anintegral part of the material. The thickness ofthe layer is determined by a combination of thetemperature and composition of the bath,applied current, and anodizing time.

The oxide layer created consists of anumber of open pores that enable dying orcoloring. The anodic oxide layer can be coloredin a wide range of shades. The process iscompleted by sealing with boiling water whichcloses the pores.

Properties The anodic oxide layer formed by anodizingprovides very good resistance to corrosion. Thesurface is not normally affected by contact withsolutions and substances with 4 to 8.5 pH. Thesurface can be stained and damaged by stronglyalkaline substances. This is something toremember for aluminum building components,which should be protected during constructionfrom concrete, cement, etc.

Aluminum's natural oxide layer has athickness of about 0.02µm. By anodizing, thethickness of the oxide layer can be increased to25µm.

The hardness of the anodized layer exceedsthat of steel, nickel and chromium and is thesame as corundum. At the same time, themelting point of the surface increases to around3600°F.

The oxide layer formed by anodizing hasgood insulation properties and a breakdownvoltage of 500V - 600V at a thickness of 12µm- 15µm. The wear and corrosion resistance ofthe surface can be improved by increasing thethickness of the anodized layer. The table belowgives recommended thicknesses for variousapplications.

Anodized extrusions are suitable for a rangeof architectural and decorative applications thatrequire a beautiful and durable surface.Anodized aluminum extrusions minimize theneed for maintenance. They should, however,for aesthetic reasons, be cleaned regularly withwater and a neutral or mild soap and putthrough a clean water rinse. Strong acids andalkalis should not be used.

Coating thickness

(µm) Application

18.0 Strong or normal exposure outdoors (e.g. building materials, vehicles and boats)

18.0 Strong exposure indoors to chemicals, in damp air (e.g. the food industry)

10.3 Relatively hard wear indoors (e.g. handrails or decorative features outdoors)

7.7 Normal exposure indoors or outdoors in dry, clean air. For refl ectors, fi ttings, decorative strips on vehicles, sports equipment

5.1 Normal indoor exposure

Industry STOdesignation

215 R1 Class I Arch.

215 R1 Class I Arch.

204 R1 Class II Arch.

204 R1

201 R1

Recommended layer thickness after anodizing

The Aluminum Anodizers Council (AAC) website provides layer thickness specifications for various applications and other useful information.www.anodizing.org/Reference/reference_guide.html

Anodizing

28



29


* ISO 9001:2000 Partnered** ISO 9001:2008

*** ISO 9001:2008, ISO 14001:2004

www.hydro.com/en/Subsites/NorthAmerica/Facilities

Hydro plant capabilities

Drawn ProgramPlant Extrusion Fabrication Finishing Tubing Management Casthouse

Belton, SC*

Kalamazoo, MI***

Monett, MO

North Liberty, IN

Phoenix, AZ**

St. Augustine, FL***

Sidney, OH***


30

When you choose Hydro, you partner withthe nation’s premier extrusion componentssupplier backed by the resources of a globalaluminum authority. We are committed tofinding new and better ways to improve ourprocesses through research, knowledgeexchange, innovation and investment to helpcustomers transform designs and ideas intoelegant, cost-effective products.

Our Extruded Products network consistsof 7 extrusion/fabrication facilities with nearly2,000 employees and roots that go back morethan 50 years. Three plants have adjacentcasthouses with capacity to, annually, producemore than 150,000 metric tons of primary-grade metal with high recycled content.

All facilities are supported by Hydro’sglobal network of Competency Centers,including the Zeeland, MI TechnologyCenter, a critical resource for research,analysis, development of new technology, andknowledge sharing.

We are firmly committed to sustainabilityand mutual benefit and believe that our workshould contribute to our communities andprotect our environment as it benefits ouremployees and customers.

We are a unit of Hydro Aluminum, aglobal extrusion technology leader and one ofthe world’s largest aluminum companies with23,000 employees in more than 40 countries.

Phoenix, AZ

Kalamazoo, MI

Sidney, OH

Belton, SC

Monett, MO

North Liberty, IN

St. Augustine, FL

Zeeland, MI Technology Center

Baltimore, MD NA Headquarters

North American resources

Belton, SCToll-Free Phone: (888) 935-5754

Monett, MOToll-Free Phone: (888) 935-5755

Kalamazoo, MIToll-Free Phone: (888) 935-5758

North Liberty, INToll-Free Phone: (888) 935-5757

Phoenix, AZToll-Free Phone: (800) 459-3030

St. Augustine, FLToll-Free Phone: (800) 835-6502

Sidney, OH Toll-Free Phone: (888) 935-5759

Hydro Solar SolutionsPhone: (602) 427-1434

A complete listing of Hydro global extrusion facilities can be found at:www.hydro.com/en/About-Hydro/Hydro-worldwide

To learn more about Hydro in North America, visit us at:www.hydro.com/en/Subsites/NorthAmerica/Facilities


Accreditation and memberships

Aluminum Associationwww.aluminum.org

Aluminum Extruders Council (AEC)www.aec.org

Solar Electric Power Association (SEPA)www.solarelectricpower.org

American Architectural Manufacturer’sAssociation (AAMA)www.aamanet.org

Aluminum Anodizers Council (AAC)www.anodizing.org

On top of the Dow Jones Sustainability IndexesHydro is one of only two aluminum companies included in the Dow JonesSustainability World Indexes (DJSI World), which includes the 10 percent bestperformers in each industry. Hydro has been included in the DJSI every yearsince the indexes were launched in 1999.

Hydro is listed on the following social responsibility indices:


Hydro is a global supplier of aluminum with activities throughout thevalue chain, from bauxite extraction to the production of rolled andextruded aluminum products and building systems. Based in Norway, thecompany employs 23,000 people in more than 40 countries. Rooted in acentury of experience in renewable energy production, technologydevelopment and progressive partnerships, Hydro is committed tostrengthening the viability of the customers and communities we serve.

Hydro Solar Solutions249 S. 51st Avenue Phoenix, AZ 85043 Tel: (602) 427-1434Fax: (602) 427-1334www.hydro.com/northamerica/solar

Copyright © 2012 Hydro Aluminum


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