Nano Solar Utility Panel Whitepaper

8/3/2019 Nano Solar Utility Panel Whitepaper

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The Nanosolar Utility PanelTM

An Overview of the Technology and its Advantages

September 2009


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2White Paper - September 9, 2009 | 2009 Nanosolar, Inc. All rights reserved.





The Nanosolar Utility Panel is the industrys first solar electricity panel specifically designed anddeveloped for utility-scale system deployment. A thin-film panel that stretches conventional expectationson power, current, system voltage, and mounting span, it enables solar power plant deployments with anindustry-lowest total-system cost.

Through its mechanical and electrical design, the panel achieves substantially lower balance-of-system

cost than conventional thin-film panels and effectively eliminates the balance-of-system cost penalty thatmedium efficiency thin panels have traditionally had over the highest-efficiency silicon panels.

1 Designed for Utility-Scale Performance

The Nanosolar Utility Panel is specifically designed and developed for utility-scale systems where thedeployment rages from 1-50MW in size. The scale and the behind-the-fence nature of these types ofdeployments both afford and require a level of industrial streamlining and optimization that is differentfrom smaller-scale systems.

Designed to reduce total-system cost, the Nanosolar Utility Panel is electrically and mechanicallyoptimized for utility-scale solar power systems:

Electrically, the product is the industrys highest-current thin-film panel, by as much as a factor of six(at over 6A). It is also the industrys first photovoltaic panel certified by TV for a system voltage of

1,500V, or 50% higher than the previously highest certified 1,000V. Combined, this enables longerpanel arrays, resulting in a host of cost savings during installation. In addition, the panel is theindustrys first solar panel with an edge connector, the Nanosolar Edge Connector, simplifyingcabling, minimizing resistive losses, and enabling higher system voltage in solar power plants.

Mechanically, the dual-tempered glass/glass package used for the panel is distinctly stronger thanconventional thin-film-on-glass panels, delivering almost twice the mounting span andcorrespondingly lower mounting materials requirements, while not adding additional weight.

Extensive reliability testing has been performed on the panel, meeting and exceeding with substantialsafety margin all tests required by all applicable IEC and UL standards, including separate certificationof the Nanosolar Edge Connector. State-of-the-art robotic automation is used to assemble theNanosolar Utility Panel in a factory near Berlin, Germany, delivering the highest degree of quality on anongoing basis.


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2 Product Features and Benefits

Based on an industry-standard glass/glass laminate package engineered for more than 25 years ofreliability, the panels unique features and benefits include the following:

High-Power Panel for Faster Deployment

At power ratings ranging from 160W to 220W, the Nanosolar Utility Panel has approximately threetimes more power per panel than conventional thin-film panels. More power per panel simplifiesindustrial-scale deployment of power in large quantities.

Tests performed by an independent third party have shown that more power per panel results in a 30%installation labor saving relative to conventional thin panels (see below).

Rugged, Hermetically Sealed Package for Maximum Reliability

A rugged glass/glass package with proven encapsulation based on a hermetic edge seal is used toensure maximum durability and to eliminate moisture due to humidity.

Specifically, our edge seal technology is engineered to exceed the sealing performance of conventional

thin-panel products by a factor of ten, providing an additional safety buffer for long-term reliability.Mechanically Strong Package for Wide-Span Mounting

Whereas thin-film-on-glass panel manufacturers deposit the solar-cell stack of thin films directly onto aglass pane, which also functions as the encapsulant towards the outside environment, Nanosolarproduces individual foil cells, sorts them into electrically matched circuits, and assembles that circuit intoa panel. By utilizing sorted-cell assembly, Nanosolar gains a panel assembly yield advantage and broadflexibility in terms of panel size, form factor and package style.

The Nanosolar Utility Panel uses tempered glass on both front and back of its glass/glass package.Note that the use of two tempered glass panes is not possible for producers of thin-film-on-glass panels,because high-temperature cell production process steps lead to de-tempering.

The use of dually tempered glass panes, with our foil cells in between, creates a package of distinctly

superior mechanical strength. Tempered glass has a strength of 120MPa, or three times stronger thanregular glass. The resulting system benefit is that it enables wide-span mounting. Wide-span mountingreduces the cost of mounting materials substantially by 40% relative to conventional thin-film panels(see below).

High-Current, High-System-Voltage Design for Utility-Scale Panel Arrays

With capacity to generate currents of 6-7 Amps (and up to 25 Amps with larger cells of the samearchitecture), the Nanosolar Utility Panel is also the industrys highest-current thin-film panel. Thecurrent-generating capacity of the Nanosolar Utility Panel surpasses other thin-film panels by as muchas a factor of six. (First Solars product supports a current of 1 Amp).

Series-interconnected Nanosolar cells have the unique capability of generating and carrying much highercurrents without any significant resistive losses. High current cells are desirable for utility-scale systemimplementations because they simplify DC cabling and save balance-of-system cost. They allow a larger

number of panels to be interconnected in series without the expense of additional cabling home runs tothe inverter. If the panels current is low (as is the case with many thin-film-on-glass products), then, forthe same amount of installed power, the system voltage is reached more quickly through a relativelysmall number of interconnected panels, and a much higher effort in cable splicing or home runs isrequired.

The Nanosolar Utility Panel is the first photovoltaic panel designed and certified by TV for asystem voltage of 1500V, or 50% higher than the Industry-standard 1000V. Careful engineering forinsulation as well as the design of the Nanosolar Edge Connector (see below) enables this.


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The electrical characteristics of a panel combine with its mechanical length to determine the panel arraylength, that is, the maximum length of a row of panels in a large-scale system installation that is possibleas an electrical panel string without running additional cables back to the inverter. The panel array lengthis calculated by dividing the panels system voltage by its open-circuit voltage (at low temperature) andthen multiplying by the panel length in mounting orientation.

The Nanosolar Utility Panel supports a panel array length of 64m, which is more than five times longerthan leading thin-film panels presently installed in large-scale fields. The difference is staggering in utility-scale systems where distances are vast; large amounts of expensive DC cabling can be required, andlonger panel array length reduces cabling requirements by as much as 73%. (For further detail, pleasesee below.)

Nanosolar Edge Connector for Fast, Minimal-Resistive-Loss Interconnection

Nanosolar has developed a new form of cabling connection for the Nanosolar Utility Panel. Acomponent separately tested and certified by TV according to the applicable connector standards, theNanosolar Edge Connector, is designed to reduce cabling labor, save material cost, and minimizeresistive losses for the kinds of installations used in utility-scale system deployments.

Figure 1: The Nanosolar Utility Panel mounted in landscape mode. There are two Nanosolar Edge Connectorsper panel. A short cable connects each panel from left to right.

The Nanosolar Edge Connector is designed to enable high system voltage and to simplify electricalconnection. Field tests performed by an independent third party have shown as much as 85% reducedlabor cost relative to conventional thin panels for panel interconnection. In addition, the Nanosolar EdgeConnector eliminates any installer connection error possible.

High Pallet Density for Minimal Shipping Cost

Engineered for multi-MW deployment logistics, the Nanosolar Utility Panel is designed for shipping viaISO-standard 20-foot freight containers as well as common truck load sizes.

It affords unusually tight pallet packing and shipment density, allowing for 132kW of panels to be shippedper 20-foot container.


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3 Reducing Balance-of-System Cost

Compared to First Solar thin-film panels, the Nanosolar Utility Panel has the following characteristicsand advantages:

Nanosolar First Solar Nanosolar Advantage

Power (W) 160-220 75 3x Power per Layup Step

Mounting Span (m) 2 1.2 41% Less Mounting Material

Current (A) 6 1 Longer Panel Arrays

System Voltage (V) 1500 1000 Longer Panel Arrays

Panel Array Length (m) 64 12 73% Less Cabling, Labor

Connectors Edge Standard 85% Faster Connection

Ship per 20 ft Container (kW) 132 40 3x Lower Shipping Cost

Table 1: The Nanosolar Utility Panel stretches performance characteristics along several key dimensions relativeto conventional thin panels such as First Solars. (*See definition above.)

These technology attributes drive balance-of-system and deployment cost efficiency in several key ways.The design of the Nanosolar Utility Panel enables balance-of-system (BoS) cost savings on mountingmaterials (A), mounting labor (B), cabling materials length and cabling labor (C), and shipping cost (D), asfurther described below.

We believe the net effect of these advantages (as of Summer 2009) is to reduce the BoS penalty

associated with the use of medium-efficient solar panels versus the highest-efficiency silicon panels from15-20 Eurocents/Watt (in the case of First Solar) to parity.


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3A. Reduced BoS Cost: Mounting Materials

The wide-span mounting capability of the Nanosolar Utility Panel drives balance-of-system cost savingson mounting materials usage as illustrated in the following figure.

Figure 2: Wide-span mounting drives balance-of-system cost savings on mounting materials. The arrow aboveindicates the free-span distance that a panel must sustain mechanically (with snow loads up to 5400Pa) wheninstalled in a typical rail-mount configuration. The larger this length, the fewer rails are necessary.

By virtue of having a 1.7 times larger spanning distance, 41% fewer Aluminum (or steel) rails are needed.

With these rails constituting around 70% of the entire mounting materials cost, a substantial fraction ofmaterials cost is saved.


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3B. Reduced BoS Cost: Mounting Labor

An independent third party performed time-clocked tests in a field in Germany, where trained teams ofinstallers mounted a full table of First Solar and a full table of Nanosolar panels. The Nanosolar Utility

Panel required 30%less mounting labor time and up to 85% less cabling time.

Figure 3: Panel size drives balance-of-system cost savings on mounting labor and panel-to-panel cabling.

The detailed results of this comparative test by a third party are the following: Mounting was 30% fasterwith the Nanosolar Utility Panel than with First Solar panels, and panel-to-panel cabling took six times

longer with First Solars panels than with the Nanosolar Utility Panel.


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3C. Reduced BoS Cost: Cabling Length and Labor

The Nanosolar Utility Panel is designed to simplify cabling and save system integrators money on laborand cabling material.

The following figure illustrates how the five times larger panel array length of the Nanosolar Utility Panelsaves system integrators a significant amount of expense in the form of DC cabling length alone. Thefigure shows the best-practice layout of a 2.66MW reference plant and the associated DC cablingnecessary for this.

Figure 4: DC Cabling required in a 2.66MW Reference System. By employing the Nanosolar Utility Panel, system

integrators save up to 73% on cabling length and labor. DC Cabling is represented in both diagrams by the orangelines with field dimensions at 300m by 230m.

3D. Reduced BoS Cost: Shipping

Due to its design for higher pallet and container packing density, the cost of shipping the Nanosolar UtilityPanel on international routes is three times less expensive.

Furthermore, by virtue of Nanosolars strategy and commitment to assemble panels regionally and localto where they are being deployed, shipping costs for Nanosolar panels should be lower with less of thecompanys working capital tied up while the product is in transit.


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4 Performance

A solar panels nominal power rating is typically measured under laboratory conditions, such as atStandard Test Condition (STC) with an artificial light source referred to as a flasher. STC represents an

approximation of the natural conditions typically encountered by solar panels. Consequently, thislaboratory-based approach requires a host of correction calculations to be applied on the rawmeasurement datacorrecting for spectral effects, temperature differences, temporal length of the flashedlight pulse, and others.

Nanosolar takes great care to continuously verify its flasher setup, calibration and methodology, andcollaborates with leading third parties in doing so. The Fraunhofer Institut fr Solare Energiesystemesuccessfully validated Nanosolars factory flasher ratings through a series of flash tests on the NanosolarUtility Panel at Fraunhofers Freiburg-based facility; the separate flash measurements were within a1.5% deviation of Nanosolars flash results.

While flasher ratings depict the capacity of a panel to produce electricity, most meaningful panelperformance data is collected through outdoor measurements of actual pre-inverter / DC and post-inverter / AC electricity generated by installations of panels.

Outdoor test installations with the Nanosolar Utility Panel have been maintained since 2007 in a varietyof geographic and climatic locations, including Nanosolar-operated and customer-operated installations inCalifornia, France, Germany, Arizona and the Antarctic.

Figure 5: Nanosolar maintains a series of outdoor test installations in a geographically diverse range of locations andclimates, including California, France, Germany, Arizona, and the Antarctic.

kWh energy delivery performance and normalized kWh/Wp energy harvests have been tracked on an

ongoing basis under identical conditions for a First Solar array and a Nanosolar Utility Panel array. Thegathered data shows that the performance of the Nanosolar Utility Panel is competitive with theperformance of the First Solar panels.

Based on flash test results and outdoor field performance measurements, Nanosolar Technical Notes onPerformance Estimating are available to Nanosolar customers and summarize all necessary inputparameters for solar energy simulation programs such as PVSYST and PV*SOL.


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5 Reliability

The Nanosolar Utility Panel architecture safeguards the embedded solar cells from any negativeenvironmental impact. Extensive internal and third-party reliability testing proves the Nanosolar UtilityPanel to be highly reliable and extremely robust. The Nanosolar Utility Panel received successfulcertification upon its first submission to TV.

Nanosolar Utility Panel Meets All Requirements According to IEC

The Nanosolar Utility Panel is certified by TV Rheinland PTL, LLC Photovoltaic Testing Servicesaccording to IEC 61646 & 61730 and UL 1703 for Electrical Safety and Class A Fire Resistance. Thepanel also received a separate TV certification for its Nanosolar Edge Connector.

Figure 7: A rigorous sequence of tests is applied to solar panels according to IEC. The Nanosolar Utility Panelwas certified by TUV Rheinland PTL, LLC Photovoltaic Testing Services according to IEC 61646 & 61730 and UL1703.


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Figure 9: Edge-box safety test in excess of IEC requirements. A voltage between the module circuit and a watersolution is applied while the module is being soaked. The resistance between the module and the water is measuredwith different voltages applied. Even when applying three times the IEC defined voltage, the resistance is still a factorof 10 above the permissible level. In the graph, DH denotes damp heat tests, HF denotes humidity freeze, and TCdenotes temperature cycles.

Rigorous Component Testing

We continually perform a series of additional reliability tests, with a focus on component and materialendurance, including:

Exposure of the Nanosolar Utility Panel to intense amounts of salt fog;

Accelerated exposure of the panel edge seal, encapsulant, edge box and ribbon connectors to UV

light (UV-A and UV-B) in an amount directly equivalent to 25 years worth of UV light;

Accelerated testing of edge box seal performance directly equivalent to 25 years of moisture andthermal cycling;

Vibrational fatigue tests, bullet and sheer-force tests.

Additional Extreme Tests Defined by Nanosolar

Panel reliability tests as defined by IEC are typically homogeneous tests, meaning the panel is subjectedto an environmental regime where each part of the panel experiences similar external conditions.However, it is additionally insightful to subject solar panels to non-homogeneous environments, such asrapid thermal shocks with a temperature gradient throughout the panel.

As one example, Nanosolar devised additional protocols to test for a panels response to sunrise onextremely cold days. This environmental stress scenario is not covered by any IEC requirement, yet canplausibly occur in real-world installations. An icy panel is subjected to intense light, almostinstantaneously heating the active solar cell layers to the Normal Operating Cell Temperature (NOCT),while the panel package is still very cold. The panel can experience a temperature gradient of 40 60Kwithin seconds, creating up to 120 MPa of momentary mechanical stress within a solar panels multiplelayers and exerting extreme stress on the weakest links of the panel architecture.

The Nanosolar thermal freeze stress test exposes a panel to -40C, and then light soaks it at an intensityof 1.5 full suns while applying an electrically variable load in order to keep the panel at its MaximumPower Point. The panel is then continuously light-soaked until its homogeneous temperature is close toNOCT. Panels are subjected to repeat cycles of this extreme test.


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This test led Nanosolars design team to eliminate weak links by optimizing the coefficients of thermalexpansion across all layers of the panel through careful material selection.

Due to our internal and external panel design, panels subjected to up to 40 cycles of Nanosolars thermalfreeze stress test have led to no failures.

Figure 10: The graph illustrates the effect of two different panels subjected to 40 cycles each of Nanosolars freezestress test. Deviations are within normal tolerance.

6 Quality

The Nanosolar quality system controls our entire production process from supplied raw materials tocustomer service and support. To start, incoming materials are qualified through extensive testing forperformance and reliability before being released into production. All critical component attributes areclearly defined and regularly tested by our suppliers, and confirmed in Nanosolar labs or independentlabs. Process parameters on Nanosolar manufacturing equipment are the result of numerous tests andtrials, and are controlled with hundreds of sensors and lines of data, with the most critical aspects understatistical process control. Regular sampling and lab testing ensure that processes remain in control, andform the basis for continual improvements. Final testing of Nanosolar cells and panels confirm that thepanels meet our performance specifications, and also feeds data back to the processes where it is

analyzed for potential process improvements. FIFO is built into the production system.Nanosolar data systems can track a panel and its components all the way back to a cells raw materialsand processing parameters. Tied together with our ongoing reliability testing, Nanosolar can identifypotential product issues well before a customer experiences them in a field installation.

Cross functional teams solve manufacturing and quality issues using Toyotas 6 step problem solvingmethodology, entering them into our quality management system that provides a library of solutions andcountermeasures for quick problem resolution.

The Nanosolar quality system helps manage daily development and production, and is also building avast library of data, tools and best practices for continuous improvements in the future.

The manufacturing of the Nanosolar Utility Panel is based on fully-automated assembly in a roboticfactory with state-of-the-art in-line quality measurement controls. Automated for a throughput of one panel

every 10 seconds, the full capacity of Nanosolars Luckenwalde factory is approximately 640MW.Working with a leading provider of lamination equipment, Nanosolar pioneered the use of stacklamination in order to accelerate this rate-limiting process step.


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Figure 11: The assembly of the Nanosolar Utility Panel is completely automated in order to meet the highestquality standards.

7 Summary

The Nanosolar Utility Panel is designed and developed specifically for utility-scale performance. Byintroducing a series of improvements to an industry-proven package with established reliabilityperformance, the panel allows system integrators to significantly reduce balance-of-system cost,essentially achieving balance-of-system cost parity with high-efficiency silicon panels.

Nano Solar Utility Panel Whitepaper

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