National Renewable Energy Laboratory

Innovation for Our Energy Future 

A national laboratory of the U.S. Department of Energy

Office of Energy Efficiency & Renewable Energy

NREL is operated by Midwest Research Institute ● Battelle Contract No. DE-AC36-99-GO10337 

PowerLight Corporation Lean 

Manufacturing, PV Manufacturing 

R&D Phase I Report 

6 December 2001 — 31 March 2003 

L. Hargis and J. Botkin

PowerLight Corporation 

Berkeley, California 

Subcontract Report 

NREL/SR-520-35881 

June 2005 
Subcontract Report 

NREL/SR-520-35581 

June 2005 

PowerLight Corporation Lean 

Manufacturing, PV Manufacturing 

R&D Phase I Report 

6 December 2001 — 31 March 2003 

L. Hargis and J. Botkin

PowerLight Corporation 

Berkeley, California 

NREL Technical Monitor: David Mooney 

Prepared under Subcontract No. NDO-1-30628-04 

National Renewable Energy Laboratory

1617 Cole Boulevard, Golden, Colorado 80401-3393

303-275-3000 • www.nrel.gov

Operated for the U.S. Department of Energy

Office of Energy Efficiency and Renewable Energy

by Midwest Research Institute • Battelle 

Contract No. DE-AC36-99-GO10337
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Submitted by the subcontractor and received no editorial review at NREL

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Table of Contents 

Abstract .........................................................................................................................................................iv

Executive Summary......................................................................................................................................iv

1.0 Introduction..................................................................................................................................... 1

1.1 Background..................................................................................................................................... 1

2.0 Conclusions and Recommendations............................................................................................ 3

2.1 Task 3.1: Model for PowerGuard Optimized Turn-key Plant Design.......................................... 3

2.2 Task 3.2: Product Lead Time Improvements................................................................................ 6

2.3 Task 3.3: Yield Improvements ......................................................................................................10

2.4 Task 3.4: Plant Operations Improvements ..................................................................................13

2.5 Task 3.8 Improved Manufacturing Capabilities for PowerGuard Generation II........................15

2.6 Task 3.9 Enhanced Design for Manufacturability .......................................................................18

2.7 Task 3.10 Advanced Quality System Implementation ................................................................24

2.8 Summary of Accomplishments ....................................................................................................26

iii
Abstract 

PowerLight Corporation (PowerLight) has completed Phase I of its PV Manufacturing

R&D subcontract, “PowerGuard®1

 Lean Manufacturing,” Subcontract No. NDO-1-30628-

04. The overall technical goal of this project was to reduce the cost of PowerGuard 

manufacturing while simultaneously improving product quality. This will enable 

PowerLight to scale up production capacity as the market for PowerGuard continues to 

grow. 

Through the introduction of world-class lean manufacturing techniques, PowerLight was 

to cut out waste in the manufacturing process of PowerGuard. The manufacturing

process was to be overhauled with an objective of removing as much as possible those 

steps that do not add value to the product. Quality of finished goods was also to be 

improved through the use of statistical process control and error-proofing in the 

manufacturing process. Factory operations were also to be addressed in order to 

streamline those factory activities that support the manufacturing process. 

This report details the progress made toward the above listed goals during the first 

phase of this subcontract. 

Executive Summary

During the first phase of this PV Manufacturing R&D contract, PowerLight has 

implemented significant improvements that will yield a lower cost and more easily 

manufactured product. The process started with the creation of an analytical model in

Task 3.1, which showed the major bottlenecks in the current production process and 

also demonstrated the benefits of some of the proposed improvements. Major 

bottlenecks have been mitigated and the basic requirements for the design of a new 

factory have been identified. Short-term improvements were identified to improve the 

flow of materials through the current factory. Long-term improvements were identified in 

the form of product changes to make PowerGuard more easily manufactured. 

In Task 3.2, changes were implemented as identified in the model created in Task 3.1 

above. A new router was added to the production line to augment the capacity of the 

existing router. This removed a significant bottleneck in the production process. Other 

changes were investigated to reduce curing time as much as possible in the existing 

process. The most significant changes were accomplished by changing the design of

the PowerGuard product and drastically reducing the curing time requirement. A new 

replacement for the coating on the top of the polystyrene boards reduced the curing time 

from days to minutes. A new manufacturing line was set up for the new product and 

overall product lead time was reduced to 25% of its original value, far surpassing the

 

1 “PowerGuard” is a registered trademark of the PowerLight Corporation. Reference in the SOW 

or Subcontract Deliverable to any specific commercial product, process, or service by trade 

name, trademark, logo, manufacturer, or otherwise, does not constitute or imply its endorsement, 

recommendation, or favoring by the United States Government, the National Renewable Energy 

Laboratory or the Midwest Research Institute. The views and opinions of any author or authors 

expressed in any Deliverable report or referenced in any Deliverable do not necessarily state or 

reflect those of the United States Government, the National Renewable Energy Laboratory or the 

Midwest Research Institute. 

iv
goal of a 30% reduction. Furthermore, for PowerGuard tiles with sloped PV, the lead 

time is reduced to less than 10% of its original value. 

Task 3.3 was focused on improvements to the yield of the PowerGuard manufacturing 

process. Error-proofing was implemented in several areas, most notably in the mixing of 

the liquids for the coating process. Short-term efforts focused on the existing 

PowerGuard production line while long-term efforts were focused on the new 

PowerGuard line. For the existing line, the reject rate was brought down to 0.6%, just

short of the goal of 0.5%, but we anticipate significant improvements with the start of 

production of the new PowerGuard design. Statistical process control (SPC) was 

implemented for PowerGuard production and initial results have shown the process to 

be working well. SPC will be expanded to more of the production process over the 

course of the second phase of this project. Additionally, a new non-conformance 

reporting procedure was implemented which will lead to better tracking of yield problems 

and more expedient corrective action. 

In Task 3.4, a new Quality Assurance/Quality Control system was put in place. Progress 

was made toward a Kanban style pull manufacturing system that will become fully 

implemented with the new PowerGuard production line. Work was done to reduce the 

cost of operating the PowerLight factory by improving the dust collection system, 

reducing noise and cleanup time, and improving the organization of the factory space. 

These improvements have helped to reduce the inventory of work-in-process (WIP) by

17% and reduced the required floor space per unit produced by 24%. The new 

production process will reduce WIP inventory by 94% and floor space by 74%. 

In Task 3.8, improvements were designed for the new production line to reduce labor,

maintain quality, and improve tool ergonomics in preparation for scaling up of production 

capacity. With the start of production on the new line, daily output quickly ramped up to 

the anticipated level. Improvements were designed which will decrease labor by 9%. 

In Task 3.9, improvements were made to the design of the PowerGuard tile to enhance 

manufacturability and reduce cost. All improvements were tested to ensure that there 

was no impact on performance or longevity. The design improvements were 

incorporated into the product, and the first 2,000 units were produced from February 

through April, 2003. 

Task 3.10 was concerned with the further advancement of PowerLight’s quality 

assurance program. PowerLight developed a closed loop corrective and preventive

action system. This is being tied to a quality assurance tracking system, which will allow 

the tracking of performance metrics for this system. PowerLight also improved testing of 

incoming PV modules by developing a new test station using dark I-V measurements to 

check the expected open circuit voltage, series resistance, and the status of the bypass 

diodes. This has significantly improved PowerLight’s ability to detect module problems 

before they are installed in the field.

PowerLight is proud of the progress that has been achieved during the first phase of this 

contract. These improvements are helping to reduce the cost of installed PV systems, 

opening new markets for clean energy power plants. We look forward to continuing this 

work in the second phase of the contract. 

v
1.0 Introduction 

1.1

Objective 

During Phase I, PowerLight was to conduct parallel efforts addressing the following 

advancements: 

• Produce an analytical model of factory operations to perform a quantitative analysis 

of factory layout to minimize product lead time and manufacturing waste;

• Implement World Class Lean Manufacturing techniques to reduce product lead time 

by at least 30% and reduce manufacturing waste by at least 20%; 

• Improve quality control techniques to achieve a maximum of 0.5% reject rate; 

• Implement Statistical Process Control; 

• Initiate ISO 9000 policies and procedures; 

• Implement Error-Proofing to the PowerGuard manufacturing process; 

• Improve factory operations to reduce inventory levels by at least 30% and required 

floor space by at least 25%; 

• Improved manufacturing capabilities for PowerGuard Generation II design; 

• Improved design-for-manufacturability of PowerGuard; 

• Implementation of Advanced Quality Systems. 

Achieving these objectives required the design of new equipment and procedures, 

installation and testing of new equipment, and the comparison of changes in the 

manufacturing process to the baseline created at the beginning of this contract. 

Background

PowerGuard building-integrated photovoltaic roofing tiles generate electricity from solar 

energy. With the assistance of PV Manufacturing R&D, PowerLight has improved the 

PowerGuard manufacturing process to lower costs, improve product quality, and 

increase production capacity. 

Figure 1 

1
A PowerGuard tile consists of a flat plate PV laminate mounted onto a flat, rigid, 

extruded polystyrene (XPS) board. Historically, the XPS boards have all been covered 

with a cementitious coating. In the new version of PowerGuard developed as part of this 

contract, the XPS board is covered instead by a layer of sheet metal. Two edges of the 

XPS board are routed into a tongue profile and the other two edges are given a groove 

profile, allowing PowerGuard tiles to be assembled adjacent to each other in an 

interlocking fashion as shown in Figure 1 above. Adjacent tiles are tied together 

electrically through connectors supplied on each PV module, thus creating an electrical 

string of PV modules. One or more strings are then electrically connected in parallel at a 

remote location creating a solar electric array (PowerGuard system). The resulting DC

current from the array is passed through a DC/AC inverter and isolation transformer 

before being tied into the building’s electric distribution panel.

PowerGuard tiles provide benefits in addition to the electricity produced in the form of 

added insulation and protection of the roof membrane from ultraviolet light. Figure 2 

shows how a PowerGuard system can reduce the heat transfer into a building and 

reduce operating costs.

Figure 2 

2
2.0 

2.1 

Conclusions and Recommendations 

Task 3.1: Model for PowerGuard Optimized Turn-key Plant Design 

Objectives 

Under this task, PowerLight and its contractor were to perform a quantitative analysis of 

two or more scenarios for a turnkey factory layout, and to measure reductions in product 

lead time and manufacturing waste for each scenario. These are both key elements to 

minimize production costs. 

PowerLight and its subcontractor were to develop an analytical model of the PowerLight 

factory and use it as a predictive tool to quantitatively evaluate performance 

improvements to the PowerGuard manufacturing process. The model would allow 

comparisons of different scenarios of factory design and would quantitatively indicate the 

effects of various changes. PowerLight was to use this model to help prioritize various 

potential upgrades to the existing production line. 

The result of this task was to be the quantitative analysis of turnkey factory layouts, a 

turnkey factory layout model of an optimized production line, and specifications for 

improvements to meet cost reduction and increased capacity goals. 

Results 

PowerLight, in conjunction with Professor Hyun-soo Ahn of the University of California,

Berkeley department of Industrial Engineering and Operations Research (IEOR), has 

developed an analytical model of factory operations. Initially, this model was used to 

identify the main imbalances and inefficiencies in the operation of the current factory. 

During the second phase of this project, the results of the model will be used in the 

process of designing the next generation PowerGuard factory. 

The model was used to generate data based on the current production process as well 

as the new production process that has been set up to produce the new PowerGuard tile 

design. The new PowerGuard design allows most of the curing time to be eliminated as 

described in Task 3.2 below. The model shows the advantages that will be realized 

when we implement the new optimized production line. The most dramatic improvement 

shown is the drastic reduction of the amount of work-in-process (WIP), which is reduced 

to less than 10% of the current levels. 

Some improvements were also identified for the existing production line that will help

reduce cost until the optimized production line replaces the existing one. By making 

changes to the existing line so that the backerboard coating portion of the line runs at a 

45-second takt time for one shift while the tile assembly portion runs at a 30-second takt 

time for two shifts, we will optimize the use of factory curing space. 

Discussion 

The model was designed to give the user a visual representation of the pre-existing 

layout of the factory as shown in Figure 3. Each operation is identified with a picture of 

the equipment used to process the material. The position of each operation and the 

distance between operations can be changed to experiment with different scenarios. 

The operating parameters of each production step can be adjusted to produce 

specifications for an optimized process. Figure 3 shows a forklift that is used to move

raw material to the first operation and a truck that is used to move finished goods out of

3
Figure 3: Pro Model Visual Representation of Pre-Existing Factory Operat

4
the facility. Product moves from one operation to the next after programmed batch sizes 

have been processed. The user can view all operations working simultaneously. 

The model details the material movement between operations and collects data used to 

calculate WIP levels, cycle time and numerous other indices. 

The current production process can be divided into two sections: the coating of 

backerboards and the assembly of the complete PowerGuard tiles. Each of these two 

processes has a cure time associated with it. The scenarios evaluated first used the 

current cure times for coating of the backerboards and for assembly of the tiles. The 

model was loaded with takt times of 15, 30, 45 and 60 seconds. The number of 

backerboards existing as WIP at the different production rates is shown in Table 1 for 

single-shift, two-shift, and three-shift operation. As can be seen, the amount of WIP 

increases as throughput increases and as the number of shifts increases.

15 seconds 30 seconds 45 seconds 60 seconds

1 shift 1168 910 742 679

2 shifts 2387 1890 1561 1339

3 shifts 4002 3165 2624 2248

Production rate (seconds per unit)

Table 1: Work-In-Process (Backerboards) (old PowerGuard process) 

Table 2 shows the maximum and average number of units stored for curing. Product is 

stacked 12 pieces to a pallet. This can be compared to actual space in the PowerLight 

factory. The total space allotted in the current PowerLight factory for curing 

backerboards and tiles is 42 pallets (504 units) per day. Thus it would not be possible to 

run continuously in the current factory at the rates simulated.

Maximum Average Maximum Average Maximum Average Maximum Average

Backerboard 840 768 660 600 540 492 456 408

Tile 420 312 324 240 276 192 228 168

Backerboard 1896 1656 1488 1296 1224 1068 1044 900

Tile 960 660 744 516 612 420 528 360

Backerboard 3204 2796 2520 2208 2076 1452 1776 1548

Tile 1608 1116 1260 876 1044 720 888 612

1 shift

2 shifts

3 shifts

15 seconds 30 seconds 45 seconds 60 seconds

Production rate (seconds per unit)

Table 2: Number of Units of Curing Material (old PowerGuard process) 

Tables 1 and 2 indicate that running the backerboard coating portion of the line at a 45

second takt time for less than 1 shift produces the maximum amount of material that can 

be stored in the factory. As described in Task 3.2 below, a second router has been 

added to the PowerGuard production line to support this production rate. Since each 

router has a capacity of one backerboard every 90 seconds, two routers can produce a 

backerboard every 45 seconds. 

The tile assembly portion of the line yields the maximum number of pallets at 2 shifts

with a 30-second takt time. However, if the tile assembly is run at the same rate as the 

coating line, then the entire production line will be balanced, and the daily schedule will

be consistent. 

5
As detailed in Task 3.2 below, PowerLight has worked on improvements to the 

PowerGuard design that will help reduce cost by improving the manufacturability of the 

product. One of the improvements will be a drastic reduction in the required curing time. 

To simulate this, the model was loaded with expected new cure times. Additionally, a 

new optimized layout was designed for the new manufacturing process. The model was 

adjusted to accurately represent the new layout. Table 3 shows the WIP generated with 

the new layout and the new design’s reduced cure time for the backerboard coating and 

tile assembly. 

15 seconds 30 seconds 45 seconds 60 seconds

1 shift 130 114 88 140

2 shifts 120 138 123 134

3 shifts 144 139 136 133

Production rate (seconds per unit)

Table 3: Work-In-Process (Backerboards) with New Layout and Reduced Cure Times 

The result shows there is no significant accumulation of WIP regardless of the takt time 

or number of shifts operated. The takt time is set based on the short initial cure time and 

the amount of space allotted for the new production line in the current factory. When the 

new factory is designed, sufficient space will be allotted to allow a significant increase in 

throughput. 

During the process of designing the new factory in Phase 2 of this project, the model 

output will be iterated with different scenarios to identify the optimum throughput and 

layout for the space available. The model will also be used to identify areas for 

improvement as part of PowerLight’s commitment to continuous improvement and the 

continued effort to drive down cost. 

2.2 Task 3.2: Product Lead Time Improvements 

Objectives 

Under this task, PowerLight was to identify and upgrade stations of the existing 

manufacturing line as needed to reduce product lead times by at least 30% and reduce 

manufacturing waste by at least 20%, while at the same time maintaining product quality 

and worker safety. 

PowerLight was to undertake steps to implement world-class lean manufacturing 

techniques and redesign equipment based upon the results identified from the model

developed in Task 1. The primary focus of this task was to reduce waste in the 

manufacturing process, which would lead to a reduction in the product lead time. This 

would provide a direct path to cutting cost in the manufacturing of PowerGuard. 

We have defined product lead time as the amount of time between the arrival of raw 

materials and the completion of finished goods. The activities which are performed in 

the process of going from raw materials to installed product can be divided into two 

categories: value-added and non value-added. Value-added activities are those that

add something for which the customer is willing to pay. In the ideal case, all non valueadded activities are eliminated, thus optimizing the use of resources and the 

responsiveness of the company to customers’ needs. In reality, there will probably 

6
always be some non value-added activity required. The objective is to reduce the non 

value-added portion of product lead time to a practical minimum. 

In order to minimize non value-added activity, PowerLight was to make an assessment 

of the true product lead time for PowerGuard at the beginning of this task. Efforts would 

then be focused on modifying the various steps in the manufacturing process to 

eliminate non value-added activity wherever possible. 

The result of this task was to be a modified PowerGuard production line that reduces 

product lead times by 30% and minimizes waste by 20% while maintaining product 

quality and worker safety. 

Results 

The initial lead time assessment showed that the current PowerGuard manufacturing

process has a minimum lead time of 98 hours and 28 minutes. At the time of the 

assessment, much of the product was stored for significant amounts of time as raw 

material or as finished goods. As a result, approximately 80% of the PowerGuard 

product had an actual lead time of over 1270 hours. 

Some new equipment was installed to help balance the production process and 

minimize the batch processes. With the development of a replacement for the 

cementitious coating on PowerGuard tiles and the implementation of a new production 

line, PowerLight was able to reduce the product lead time significantly. When 

manufacturing tiles with sloped PV modules, the product lead time is less than 10% of 

the original lead time. With a horizontal PV module as in the current PowerGuard 

design, the product lead time on the new production line will be reduced to 25% of the 

original lead time. 

Discussion 

As stated above, the existing PowerGuard production process had a minimum lead time 

of 98 hours and 28 minutes. PowerLight worked to reduce product lead time in two 

ways. First, steps in the production process that were creating bottlenecks were 

identified and assessed for possible improvements. Second, changes in the product 

design were investigated which would reduce cure time requirements. Near term 

improvements were made by removing bottlenecks, and drastic improvements were 

made for the long term by finding an alternative to the cementitious coating of the 

PowerGuard backerboards. 

The primary bottleneck in production was the process of routing the tongue and groove 

profile on the backerboards. PowerLight has used a single CNC router for the previous 

three years. Because the process of routing backerboards is much slower than the 

coating process, routed backerboards were fabricated in large batches. When enough 

boards were finished, a coating run was started and continued until all the backerboards 

were coated. To increase the throughput of the routing process, the old router was 

augmented by a second router with the same specifications. The new router was 

installed and the old router was moved into a new position next to the new one as shown 

in Figure 4. The two routers are now positioned to feed the coating process directly. 

With the new router commissioned, coating runs are performed with routed boards 

coming off the routers and going straight into the coating process. This reduces some of 

the non-value added time in the product lead time. It also drastically reduces the 

amount of preparation time and floor space required for each coating run.

7
Figure 4: Old and New Router 

A second large bottleneck has been floor space due to the curing requirements at the 

different stages of manufacturing. At the beginning of this contract, it was the standard 

practice to coat as many backerboards as possible during a coating run. This filled the 

factory with curing material. A large number of backerboards had to be routed to get 

ready for the next coating run, but since the floor space was filled with curing material, 

there was not much space for the stacks of routed backerboards. During this contract, 

PowerLight has worked towards using smaller coating batches and doing them more 

often. This way the capacity of the factory can be maximized, and the daily operation 

can be consistent. Also the storage of material can be consistent. These improvements 

help reduce wasted labor involved with moving materials more than necessary. 

Other smaller bottlenecks have been addressed as well. Painting of XPS boards to 

make into spacers for the PV modules has been a time consuming process, and the 

paint must cure before the cutting operation can be done. PowerLight investigated 

several alternate methods of painting the spacers. It was especially desirable to paint

the spacers either during the attachment of the spacers to the backerboard or during the 

PV attachment process. This would allow the paint to cure at the same time as the 

coating or the PV adhesive. Painting during the PV attachment process appeared to 

have the most promise of success. PowerLight purchased a pressurized paint roller 

system to try out, which was evaluated, but found to be inadequate for complete 

coverage. Other alternatives will be investigated. 

To achieve drastic reductions in product lead time, PowerLight focused on changing the 

PowerGuard product to improve its manufacturability. The primary focus of this change 

has been to reduce curing times as much as possible. Since most of the curing time 

required is for the coating, PowerLight began investigating alternatives to the current 

coating. An alternative to the coating was developed which cuts the curing time from 72 

hours to six minutes. Additionally, in the PowerGuard tiles with sloped PV modules, the 

adhesive for the PV module was replaced with mechanical fasteners, completely 

eliminating a curing step. Manufacturing of the new product design lends itself very 

readily to a continuous flow operation. When manufacturing the sloped PV tiles, the

product lead time is 13 minutes, which is less than 10% of the original lead time. With a 

horizontal PV module, the product lead time on the new production line will be reduced 

to just over 24 hours or 25% of the original lead time. 

A small assembly line was set up at the back of the PowerLight factory to produce the 

new PowerGuard design. Due to space limitations, it was set up for a fairly low 

8
throughput. This throughput can be increased when additional space becomes available 

by increasing the length of the conveyor line and by improving the assembly tools for the 

workers. The major pieces of equipment were sized for the higher throughput level 

anticipated in the future.

Manufacturing waste has been reduced in many ways. The older manufacturing 

process produces physical waste in a few different forms. The routing process produces 

foam dust. Foam stock is trimmed to the appropriate size to feed the router, and this 

leaves small blocks of wasted foam. Excess coating formula is trimmed from the edges 

of the backerboards. A small amount of coating formula is wasted during startup and 

shutdown of the coating line. There is also waste in the form of non-value added activity 

in the manufacturing process and wasted labor when material has to be moved or 

reworked. The bulk of the waste in the existing manufacturing process is in the nonvalue added activity. In going to the new PowerGuard manufacturing process many of 

the non-value added activities have been eliminated. 

Stacking of material represents a lot of wasted labor. At the beginning of this project, the 

existing manufacturing process involved three stacking operations. Routed foam boards 

were stacked to get ready for coating. Coated boards were stacked for curing. 

Complete tiles were stacked after final assembly. With the addition of a second router, 

the first of the three stacking operations can be eliminated, and with the transfer to the 

new production process, the tiles are only stacked once at the end of the entire process. 

The various curing steps in manufacturing the older PowerGuard design also require a

lot of labor to move the material around the factory. After the stacks of material are 

made at each step, the stacks must be moved for storage, and then moved to the 

beginning of the next step for processing. By creating a continuous flow process for the 

new PowerGuard manufacturing line, the parts move along a conveyor line until they are 

finished. All excess handling is eliminated. 

With the older PowerGuard design, the coating edges slump as they come out of the 

coating process. Once the coating has taken an initial set, the edges must then be 

trimmed to remove the slumped material. This results in wasted material and wasted

labor. The slumped material is dropped onto the floor, which must then be cleaned 

afterward. The trimming process requires two workers during the coating process and 

for two hours afterward for the cleaning. All of this is non value-added activity. By 

replacing the coating in the new PowerGuard design, this trimming process is entirely 

eliminated. 

To minimize wasted foam, PowerLight has worked with its foam supplier to make custom 

size foam boards. This results in foam stock that yields exactly two routed boards 

without any leftover blocks. This reduces wasted material and also reduces wasted 

labor that was required to pick up the leftover blocks and package them to send to the 

recycler. 

By eliminating the various steps described above, approximately 27% of the labor 

involved with assembling PowerGuard tiles is eliminated. Since all of this was wasted

labor, this change results in a drastic reduction in waste. While the routing process still 

generates waste foam dust in the new process, the amount of material is reduced due to 

a modified tongue and groove profile. Most other manufacturing waste is eliminated in 

the new process. 

9
Once the major components of the new assembly line were in place, PowerLight ran 

several small pilot runs to test out the process and the new parts. Factory workers were 

trained in the new assembly process, and production began in February 2003. 

2.3 Task 3.3: Yield Improvements 

Objectives 

Under this task, PowerLight and its contractor were to improve quality control to achieve 

a maximum of 0.5% for parts that are rejected or require rework (from current level of 

1% requiring rejection, 2-3% requiring rework). 

PowerLight was to study and evaluate system behavior to identify causes of variability of 

product quality and all causes of parts requiring rejection or reworking. PowerLight was 

to begin by evaluating variations in the coating mixture and coating edging methods and 

would also investigate other elements of the line that lead to product quality variability. 

Based on this evaluation, upgrades were to be made that would achieve a limit of 0.5% 

of parts to be rejected or which require rework. 

PowerLight was to incorporate error-proofing into the manufacturing process either by

mechanical or electronic means as required in each step. This would start with 

performing a Failure Modes and Effects Analysis (FMEA) to determine the 

consequences of possible failure at each step of the manufacturing process. PowerLight 

was also to look at product changes that could be done to error-proof the PowerGuard 

manufacturing process.

After performing the FMEA, PowerLight was to implement appropriate detection 

methods at each step of the process based on the severity and likelihood of failure at 

that step. After the error-proofing steps were implemented, PowerLight was to use 

statistical process control during manufacturing. Attribute data or variable data would be 

used to predict special cause variation within normal random variation. PowerLight was 

to measure key product characteristic (KPC) variables during manufacturing. KPC are 

defined as those characteristics that affect fit, form, or function related to product safety. 

The result of this task was to be achievement of a limit of 0.5% of manufactured parts

that are rejected or require rework. 

Results 

Some new tools were created to error-proof various parts of the production process. 

Long term yield optimization efforts focused on the new PowerGuard design. The 

incorporation of error-proofing and statistical techniques resulted in an improvement in 

product quality. The original rejection rate of 1% or 10,000 parts rejected per million 

produced was improved to 0.6% or 6,000 parts rejected per million produced (PPM). 

The original target of 0.5% or 5,000 PPM was closed in to within 0.1% or 1,000 PPM. It 

is anticipated that we will achieve or exceed our goal after we fully implement the new 

quality system for PowerLight Corporation. The completion of the FMEA set the tone for 

developing an error-proofing system for spacer placement and photovoltaic testing which 

is still progressing. Error-proofing of the liquid mixing process has also reduced 

variability of the coating process. In addition PowerLight has identified Key Process 

Characteristics and is implementing protocols to control them and reduce variability. 

10
Discussion 

At the beginning of this contract, PowerLight was focusing yield improvement efforts on 

the existing PowerGuard design. In an effort to error-proof the process of trimming the 

coating edges of PowerGuard backerboards, PowerLight designed and tested a new 

lightweight tool. The tool was designed to accomplish the work of trimming each tile 

edge, but with only half the stroke of the existing tools. It was found, however, that while 

the edges were trimmed consistently with the new tools, the tongue profile usually got 

coating residue smeared unevenly along its length. When compared to the work done 

by a skillful worker with a hand trowel, the result was judged inadequate for production. 

As a result, the focus shifted to choosing workers with attention to detail to trim the 

coating edges. 

PowerLight has implemented a new design for the spacer placement station on the 

coating line that error-proofs both the set-up and the placement of spacers on the coated 

backerboards. With the previous station, the set-up was time consuming and required 

adjusting the position of the placement guide each time the set-up was changed. With 

the new station, each PowerGuard tile has a guide that is mounted to a frame. The 

frame is positioned with dowel pins so that it is positioned consistently. Once the 

position is adjusted the first time it is used, it can then be taken off and re-installed 

without requiring further adjustment. 

It was decided early in the design process that the only spacer which needs true errorproofing is the one that will be next to the junction box of the PV module. The new 

spacer placement station incorporates a bar that prevents that spacer from being placed 

too close to the edge of the tile. This prevents fit problems when the PV module is 

attached later. The new spacer placement station was installed near the end of 2002.

PowerLight designed and implemented a new fluid mixing system for the liquid 

ingredients of the coating as shown in Figure 5. The previous system had no capacity to 

detect errors in the fluid mixing process. Errors would only be detected if the operator of 

the coating hopper remembered to look at the fluid flow meters while the system was 

pumping fluid to the mixing barrel. The new system incorporated a programmable logic 

controller (PLC) and flow meters on all three fluid lines. The PLC monitors the flow of

one line and then drives pumps on the other two lines at speeds that create the correct

proportions in the mixture. The PLC monitors the flow rate on all three lines, and if it

detects any flow outside of the acceptable tolerance range, it shuts down the system and 

activates an audible and visible alarm. The system also stores a variety of error codes 

to allow the operator to quickly determine the cause of the problem. The PLC stores 

historic flow data for a period of time so that it is possible to monitor the accuracy of the 

mixing system. 

11
Figure 5: Error-proof Liquid Mixing System 

A nonconformance reporting process has been developed to establish metrics on 

supplier, in-process, and field performance. This data is being compiled into a closedloop corrective action system that will provide a basis for reducing process variability and 

rejections. This system is designed to document nonconformances and provide a 

closed-loop corrective/preventive action process to eliminate those nonconformances. 

The procedure requires that any employee of PowerLight has the authority to initiate a 

nonconformance report whenever product or processes are not to specified 

requirements. The quality function operates as a facilitator to obtain effective corrective 

action and to identify trends in the data for management review. All of these efforts are 

being loaded into cost of quality models that identify waste, loss, and other inefficiencies. 

The long-term goal is to achieve a six-sigma quality operation. 

As part of the efforts in Task 3.2 to improve the product lead time, PowerLight started

investigating a variety of product changes that would improve the manufacturability of 

PowerGuard. Efforts continued to improve the yield of the existing PowerGuard product, 

but the long-term focus shifted to the yield of the new PowerGuard design. 

SPC has been applied to the new PowerGuard manufacturing process. PowerLight is 

measuring the capability of the process by using SPC on the critical design features. A 

process is considered capable when the variation in critical design features is below the 

required threshold. Once a process is shown to be capable, it will reliably produce parts 

within the required tolerance. The information is fed back into the manufacturing 

process to reduce variability and material rejections. The initial efforts were focused on 

spacer placement and photovoltaic electrical integrity. In addition, valuable process 

control and capability studies have been performed on all of the metal parts. This has 

resulted in adjustments to the process, specification, or design to improve yield. 

PowerLight will continue to develop this process to reduce variability. 

 

12
2.4 Task 3.4: Plant Operations Improvements 

Objectives 

Under this task, PowerLight and its contractor were to minimize wasted labor and 

optimize the flow of materials through the factory. This would lead to a reduction in 

inventory levels by at least 30% and a reduction in required floor space by at least 25%. 

PowerLight was to approach optimizing labor by incorporating ISO9000 policies and

procedures to adapt efficient manufacturing techniques. This would entail applying 

industry quality standards to factory operating procedures to achieve generally accepted 

quality practices. 

PowerLight was to begin the implementation of an MRP or Kanban system. The 

benefits of these systems include streamlining product flow, reducing excess inventory, 

minimizing required supervision, reducing required floor space, meeting tight customer 

deadlines, and dealing with product proliferation, all of which contribute to the reduction 

of the cost of PowerGuard manufacturing. 

The expected result of this task was the implementation of an MRP or Kanban system 

and implementation of a QA/QC program resulting in the targeted improvements listed 

above. 

Results 

PowerLight achieved a 17% reduction in work-in-process inventory levels by moving

toward a continuous flow system that reduced the batch sizes of material produced. 

This resulted in a 17% reduction in the floor space required and a 24% reduction in 

labor. The new production line for the new PowerGuard design has been installed, and 

this will reduce inventory of work-in-process by 94% and floor space required by 

approximately 74%. 

A quality system was created using ISO standards. This has resulted in the creation of 

an ISO9001 series quality manual, quality procedures, quality instructions and forms to 

standardize the entire company’s operations and reduce process variability. 

Discussion 

PowerLight worked to reduce the cost of factory operations in several different ways. A 

new quality assurance system was created. The production process was changed to 

become more of a pull system to minimize inventory levels. Changes were made to help 

with factory organization and cleanliness to minimize the amount of labor spent 

maintaining the factory workspace. Additionally, improvements were put in place to 

increase the safety of the workers. 

During the first year of this contract, PowerLight has worked to change the factory 

operation from a series of batch operations to a continuous flow. The ultimate goal is to 

have a system where each operation has a staging position that is used to signal the

process immediately upstream when a new part is needed for processing. This creates 

what is known as a pull system. Each station produces a new part only when the station 

immediately downstream needs one. With the production launch of the new 

PowerGuard design on the new assembly line, PowerGuard production became a true 

pull system. Meanwhile, steps have been made in that direction with the older 

PowerGuard production line. The amount of improvement that can be made with the 

13
existing production line is limited, however, due to the amount of curing time required. 

Some batch processing is necessary. 

By decreasing the batch size and running each part of the manufacturing process more 

frequently, PowerLight has been able to reduce work-in-process (WIP) inventory, labor 

required per unit produced, and floor space required. At the beginning of this contract, 

the existing operating mode was to produce a week’s worth of material at the beginning 

operation and store it in preparation for the next step. This batch of material was then

processed through the next operation and so on until the process was complete. 

Currently, the system builds a one-day supply of material that can be consumed by the 

subsequent process in equal time. This has led to a 17% reduction in inventory levels. 

Additionally, this reduced the amount of material that had to be physically moved and 

repositioned for storage, then to be moved again for further processing. This represents 

a 24% reduction in labor required per tile produced. The storage space needed for 

curing accounts for the majority of the space in the factory. By limiting the amount of 

curing product on a daily basis, rather than building large batch sizes a few times a 

week, the total amount of square footage required has been reduced by 17%. 

With the production launch of the new PowerGuard sloped PV tiles, most of the WIP is 

eliminated in that process due to the drastic reduction in cure time. The level of WIP 

inventory is reduced by 94%. Similarly floor space required is reduced by approximately 

78%. The older PowerGuard production line will continue to produce tiles for some time 

in parallel with the new one. During this time, there will still be a large amount of WIP in 

the factory from the old process. This WIP will be eliminated when production is 

transferred completely to the new production line. 

As part of the effort to create a continuous flow for the current production line, a second 

router was added as discussed in Task 3.2, and both routers were positioned side by

side so that the movement required to bring material to and from the routers would be

minimized. After the new router was commissioned, the coating line was operated 

simultaneously with the routing operation, with backerboards coming off the routers and 

going directly into the coating process. 

The layout of the PV attachment process was also changed to facilitate easy movement 

of materials and to minimize wasted motion on the part of the workers. This has allowed 

the PV attachment process to run simultaneously with the coating process. In 

November 2002, the processes of routing backerboards, coating backerboards, and 

adhering PV modules were all being done simultaneously. The ability to perform all 

these functions simultaneously aids in the efficient use of floor space. Additionally, this 

allows the factory to produce the same volume with two shifts per day rather than three, 

offering additional cost savings. 

PowerLight installed a new dust collection system that will help to reduce cost. By more 

efficiently collecting XPS waste, the new system will minimize labor spent to clean up the 

equipment and the work area. Through better containment of the XPS dust, the 

maintenance requirements of the equipment will be reduced, and the equipment will be 

less prone to failure. 

PowerLight commissioned an investigation into the noise and dust exposure of the 

factory workers. It was determined that particles of the size generated in the factory do 

not pose any health risks, though they can affect the comfort level of the workers. As a 

result, all workers who work in the vicinity of the XPS processing equipment were 

14
provided with dust masks. It was also determined that the noise level due to the routers 

was too high for long-term exposure. The workers were provided with suitable hearing 

protection based on their proximity to the routers as a temporary measure. For a 

permanent solution, a noise attenuation enclosure was purchased and installed around 

the two routers. Once the enclosure was installed, the noise exposure was measured 

again. The noise exposure test showed that with the new enclosure, none of the 

workers in the factory need to wear hearing protection. 

A new Quality Assurance program has been created to provide quality assurance in 

receiving, in-process and final inspection activities. The following ISO9001 elements 

have been detailed in quality procedures: 

1. Management Responsibility 

2. Quality System 

3. Contract Review 

4. Design Control 

5. Document and Data Control 

6. Purchasing 

7. Control of Customer Supplied Product 

8. Product Identification and Traceability 

9. Process Control 

10. Inspection and Testing 

11. Control of Inspection, Measuring and Test Equipment 

12. Inspection and Test Status 

13. Control of Nonconforming Product 

14. Corrective and Preventive Action 

15. Handling, Storage, Packaging, Preservation and Delivery 

16. Control of Quality Records 

17. Internal Quality Audits 

18. Training 

19. Servicing 

20. Statistical Techniques 

The collection of quality data has begun as described in Task 3.3. A non-conformance 

procedure has been implemented to formalize the reporting and tracking of quality 

issues. 

2.5 Task 3.8 Improved Manufacturing Capabilities for PowerGuard Generation II 

Objectives 

Under this task, PowerLight was to improve the tools and processes used for 

manufacturing the new PowerGuard design. As discussed above, PowerLight made 

modifications to the design of PowerGuard tiles in Task 3.2 of this contract in order to

reduce the product lead time. Additionally, PowerLight began the implementation of a 

new production line in PowerLight’s Berkeley, California facility. In order to increase the 

15
production rate to ramp up capacity, it was necessary to improve the tools and methods 

used to manufacture the tiles. 

The initial production setup was to be used for pilot production and the first full 

production run at a rate of two minutes per tile. Based on the experience gained in using 

this setup, PowerLight was to identify changes necessary to reduce labor, increase 

production rate, and reduce waste in the production process. Improved tooling would

aid in accurate alignment of parts and in error-proofing the assembly process. 

The result of this task was to be the design of improvements to the PowerGuard 

Generation II production line that reduce the labor requirement per tile by 10%. 

Results 

Production started in February 2003. During the first day of production, throughput was 

approximately 6 minutes per tile since the workers were unfamiliar with the new process. 

During the course of the next few days of production, the rate quickly went to 4 minutes 

per tile, then 3 minutes, and then to 2.3 minutes. By the third week of production, the 

workers were meeting their daily goal of 180 tiles. 

The production line was initially designed for a two-minute throughput. There were 

eleven workers required for this rate. The stations for each worker are described below: 

1. Router operation 

2. Roll coater operation 

3. Sheet metal handling 

4. Sheet metal handling 

5. Sealant application 

6. Front spacer install 

7. Deflector assembly 

8. PV module test and prep

9. PV/deflector assembly 

10. PV attach 

11. Material handling 

During the first production runs several improvements were implemented. The 

screwdrivers used to install the spacers were found to be inadequate, and several 

different versions were tried. Most of the production was done with pneumatic torquelimiting screwdrivers. An improved system has been specified and quoted, but has not 

yet been installed. The new system consists of a pneumatic, push-to-start, in-line 

screwdriver attached to a support mechanism that keeps the screwdriver aligned 

vertically and also absorbs the torque applied to the screw so that the worker does not 

get tired. Figure 6 shows an example of this type of support mechanism. 

16
Figure 6: Proposed Pneumatic Screwdriver and Support 

The attachment of the sheet metal cover is the trickiest part of the assembly process. 

With the current setup, two workers support the sheet metal. The roll coater operator

positions the foam backerboard, and the sheet metal is then lowered into position. The 

alignment must be done precisely and quickly. To improve this station, an alignment 

fixture has been designed, and a support mechanism for the sheet metal covers has 

been specified. This will allow one worker to handle the sheet metal covers instead of

two. Figure 7 shows the alignment fixture with a foam backerboard in position. Figure 8 

shows the proposed support mechanism for the sheet metal. 

Figure 7: Sheet Metal Cover Alignment Fixture 

17
Figure 8: Proposed Sheet Metal Support Mechanism 

Other improvements were made during the first production runs. An improved drill 

fixture was fabricated to catch the chips created when mounting holes are drilled in the 

frame of the PV module. An indicator light was added to the stacking fixture to signal the 

material handler that the pallet is full and must be replaced with an empty pallet. 

Most of the improvements that have been made to date have been related to quality or 

ergonomics. The sheet metal alignment fixture and support will reduce the labor 

requirement by one person. This will yield a reduction of 9% instead of the expected 

10%. As production continues during the second phase of this project, further 

improvements will be made to reduce the labor requirement per tile. 

2.6 Task 3.9 Enhanced Design for Manufacturability

Objectives 

Under this task, PowerLight was to expand upon the work started in Task 3.2. The focus 

was the continued improvement of PowerGuard design-for-manufacturability (DFM). 

These improvements were targeted toward reductions in cost, part count, and lead time. 

Design modifications were to be validated through testing. 

18
Design improvements under this task were to incorporate new features in the advanced 

tile coating as well as an enhanced tile-to-tile connection in order to reduce 

manufacturing costs. Tile securement details were to be developed for high volume

production in order to lower the overall cost of an installed system. An initial production 

design incorporating the replacement for the cementitious coating and enhanced tile-totile connection was to be developed and implemented on a production line as well as 

through shipping and installation on a roof. 

Design modifications developed under this task were to be evaluated through testing 

and/or analysis. A preliminary evaluation of the long-term effects of moisture and freeze 

thaw cycling on the tile components was to be completed. In addition, the ability of the 

new design to adequately drain heavy rainfall was to be evaluated. 

The result of this task was to be a completed production design of the PG tile that 

incorporates manufacturability improvements. 

Results 

Under this task, PowerLight has successfully created an improved PowerGuard tile 

product, Gen II, shown in Figure 9. Production of Gen II PowerGuard started in 

February 2003. The new Gen II product features sheet metal as an advanced tile 

coating that replaces the cementitious coating in the Gen I product. This design 

enhancement allows for significant improvements in the manufacturing of the 

PowerGuard tile. 

Figure 9: Gen II Production Tile Design 

As part of the development of the Gen II PowerGuard tile, all design changes were 

tested to ensure that the integrity of the PowerGuard design was not compromised. 

Moisture diffusion into the foam and freeze-thaw cycling endurance were tested with 

favorable results. Drainage testing was done at various simulated roof pitches. Wind

tunnel testing was done with the new tile design. Results for these tests were favorable. 

Details are discussed below. 

19
Discussion 

Tile Design

By replacing the cementitious PowerGuard coating with sheet metal, the quality of the 

tiles is greatly improved due to the increase in product consistency, and the reduction of 

messy materials in the manufacturing process. Additionally, as discussed in section 2.2 

above, the processing time for each board is greatly reduced from 3 days to cure the 

cement to 6 minutes to cure the adhesive on the board. Figure 10 and Figure 11 show 

Gen II PowerGuard tiles being assembled. 

Figure 10: Continuous Backerboard Assembly Process 

An additional design improvement, which has resulted in reduced lead time, involves 

using screws and other mechanical fastening hardware instead of an adhesive with a 

long cure time to attach the spacers to the PV and the backerboard. 

Figure 11: Completed Tile Assembly on the PL Factory Line 

20
Other design improvements have increased the overall functionality of the PowerGuard 

product. A significant improvement in the design of the tile includes the use of sheet

metal spacers to replace the polystyrene foam spacers. The use of sheet metal 

increases the overall structural integrity of the tile. Additionally the sheet metal allows for 

a greater flexibility in the design features that can be incorporated into the spacer. The 

first Gen II product is a sloped tile that ships flat and is tilted and secured in place during 

installation. This feature reduces the cost to ship the tile to the installation site. The 

sloped tile configuration increases the amount of energy generated annually by the PV 

module. Future work will involve the development of flat tile spacers that integrate with 

the backerboard sheet metal. Also, this spacer design, which includes the use of 

brackets and fastener hardware, allows for the easy maintenance and replacement of a 

PV installed in the array. This design feature will reduce service and maintenance costs 

of PowerLight photovoltaic systems.

Moving from a cementitious coating to a sheet metal coating has also facilitated the 

creation of a more full-featured tile-to-tile interconnector. Interconnection in the Gen I 

product relies on the tongue and groove profiles which are cut into the foam of the 

backerboard. In the Gen II product, an interconnector was designed which serves as a 

mechanical fastening and electrical grounding interconnection. The Gen II interconnector 

(Figure 12) creates a positive mechanical connection between the tiles, which resists 

lateral and uplift loads from wind, seismic, and gravity forces that could potentially distort 

an array and compromise the integrity of the system. Additionally, this interconnector is 

designed to serve as the grounding bond between the tiles to satisfy national electrical 

codes and safety practices. This design has been integrated with the backerboard sheet 

metal design to promote ease of manufacturing and ease of installation on the roof.

Figure 12: Tile Interconnect 

In February 2003, over 1,100 Gen II tiles were fabricated at PowerLight’s factory. By the 

beginning of April over 2,000 Gen II tiles had been produced.

In February and March, PowerLight installed over 1,100 Gen II tiles on the GSA Building 

in Downtown Los Angeles. This represented the first commercial installation of the new 

Gen II tile. Engineers were on hand to assist with the installation and gain valuable 

insight into design and manufacturing improvements that could both lower costs and 

increase installation ease. Figure 13 and Figure 14 show the Gen II PowerGuard tiles 

being installed. 

21
Figure 13: First Commercial Gen II Tile Lift 

Figure 14: First Gen II Commercial Installation, February 2003 

By the end of April, PowerLight installed over 2,000 Gen II tiles on the GSA Building in 

Downtown Los Angeles. 

22
PowerLight will continue to develop the Gen II tile design by building on the successes 

discussed above. Future Gen II tile improvements will continue to target reductions in

cost, part count, and product lead time. Product redesign will focus on further cost 

improvements while reducing assembly operations. Additionally, PowerLight will 

continue to expand the family of new PowerGuard products as well as reduce overall 

cost sensitivity to component availability through continued development of our design 

for flexible manufacturing. A final production design incorporating lessons learned on

initial production runs and initial installations will be developed and implemented on the 

factory production line.

Testing

Diffusion Testing 

Although the foam used in PowerGuard is closed cell, and therefore does not absorb 

water, water can diffuse into the polymer. PowerLight wanted to ensure that subsequent 

freezing and thawing would not damage the foam’s insulating properties, and possibly its 

structural properties as well. Diffusion and freeze-thaw testing is intended to simulate 

the weathering experienced by insulating panels which sit on a warm, moist roof 

membrane while being exposed to cold air and repeated freezing and thawing in diurnal 

cycles. This testing is accelerated by making the temperatures more extreme and the 

cycling more frequent than would be encountered in reality.

Samples are subjected to European Normative Standard (EN) 12088. This procedure 

first saturates the foam with water. Samples are then conditioned following EN 12091 for 

freeze-thaw. All samples are then tensile tested to failure to determine foam yield 

strength. Tensile test results are also compared to results from samples retrieved from 

the field. 

Different types of foam and different tile constructions were tested. One type of foam 

that was tested clearly out-performed the other. All of the samples of the Gen II 

PowerGuard design passed the acceptance criteria. Further, several types of facings 

were tested as possible future designs. Of these, some performed better than others. 

The manner in which facings were attached to the foam was expected to have a 

significant impact on results, however in these standard tests, it did not. It is speculated 

that in “real-life” conditions, the attachment mechanism would play a larger role than in

these standard tests. 

All specimens, including those removed from the field, met the criteria of maintaining at 

least 20 psi tensile strength after the testing. The results of this test will be used by the 

PowerLight engineering group when considering future PowerGuard design changes.

Drainage Testing

Roofing systems are designed to drain rainfall from the roof as quickly as possible to 

avoid roof and/or structural damage. PowerGuard systems installed over an existing 

roof have been designed to allow rainfall to flow to roof drains. Testing has been done

to ensure that the design changes that resulted in the Gen II PowerGuard tile will not

impair the drainage of heavy rain. 

Over an averaging period of one hour, the maximum rainfall ever recorded is on the 

order of 5”/hour. However, over a shorter averaging period such as 1-5 minutes, rainfall 

rates of 30”/hour can be expected. For this reason, PowerLight has opted to investigate 

drainage performance of roof-mounted products at a rainfall rate of 30”/hour. 

23
A test set-up was constructed that simulates up to 30”/hour of rainfall over a 4’ x 20’ 

area. The test set up is shown in Figure 15 below. The reservoir on the left side of the 

photo stores water that is pumped through PVC piping to an area above the platform. 

The platform is used to model a roof, and can be sloped at any angle between 0o

 and 

18o

. Full-scale PowerGuard tiles can be installed on top of the platform to observe 

performance in heavy rain. 

Figure 15: Drainage Test Setup 

Several test iterations were conducted on PowerGuard tiles. Data collected included

water flow rate into and out of the system, and water level measurements within the 

array. From these data, PowerLight determined the rate of drainage through the array at 

maximum rainfall conditions. Tests are continuing at other rainfall rates to completely 

characterize the system. 

Tests were conducted with and without the perimeter curbing detail, and on slopes of

0:12 and 1:12 (0o

 and 5o). Test results indicated that simple modifications to the 

PowerGuard geometry might significantly improve drainage of the system. Fortunately, 

the design modifications are in-line with proposed modifications to improve 

manufacturability of the product. 

Further testing is planned on several other design alternatives and various roof slopes. 

2.7 Task 3.10 Advanced Quality System Implementation 

Objectives 

Under this task, PowerLight was to improve the quality system as first step towards ISO9001 compliance. PowerLight was to define the corporate quality policy, vision, mission 

and core values and measure performance to those defined objectives. The quality 

management system was to be documented so that this performance could be 

measured. The implementation of a closed-loop corrective action program was to be 

implemented. This would include process measurements in manufacturing as well as

from the field. 

24
The result of this task was to be the complete documentation of the quality system. 

Performance indicators were to be established for the activities of design, 

manufacturing, installation and servicing. These enhancements in the quality 

management system would allow for performance metrics to be obtained and analyzed 

for positive corrective and preventive action. Once established, there would be specific 

performance indicators measured in the areas of scrap, rework, and first pass yield. 

Results 

PowerLight has developed a closed-loop corrective and preventive action system. An 

interdepartmental team developed a corporate policy for corrective and preventive action 

in January 2003, which became section 4.14 of the quality assurance manual. This 

policy established the requirement for the development of procedures and training in this 

critical area of quality assurance. PowerLight then developed document QP9190 Rev A, 

"Corrective and Preventive Action" as the quality procedure for conducting closed-loop

corrective and preventive action. Two forms were developed to document internal and 

external corrective action responses to issues affecting the quality of our products and 

services. Currently PowerLight is automating this system by implementing a Quality 

Assurance Tracking System, which will allow us to accomplish performance metrics on

those corrective and preventive action plans. Once fully implemented, we will have a 

fully optimized system for documenting, tracking and measuring the performance of 

corrective and preventive actions taken by Powerlight and its suppliers.

To improve the efficacy of incoming inspection, PowerLight designed a system to utilize 

Dark I-V testing of PV laminates. This testing measures PV parameters by forcing 

current (I) through the module in forward and reverse bias, and measures the voltage 

drop (V) created. The data are analyzed at 3 points, giving an estimate of open circuit 

voltage, series resistance, and the status of the bypass diodes. Test results are logged 

with the module serial number for quality tracking. 

This system improves on the previous test setup because it is more accurate and 

precise, uses less energy, and reduces transcription errors in the quality tracking 

process by employing a bar code scanner. In addition, the new tester is able to 

diagnose missing bypass diodes, whereas the old system could only diagnose a shorted 

diode. The new test station is shown in Figure 16. 

Figure 16: Dark I-V Module Test Station 

25
2.8 Summary of Accomplishments 

Over the course of this phase of the contract, many improvements have been made in 

the production of PowerGuard tiles. Most significantly, the development of a new design 

of PowerGuard tiles has greatly improved the manufacturability of PowerGuard creating 

the potential for drastic reductions in cost. The significant improvements made possible 

through this PV Manufacturing R&D contract are as follows: 

• The creation of an analytical model of the PowerGuard production process 

• Reduction of product lead time of over 90% for the sloped PV PowerGuard tiles 

and 75% for flat PV PowerGuard tiles 

• Error-proofing of various parts of the PowerGuard production process 

• Reduction of reject rate for current PowerGuard production to 0.6% 

• Implementation of a Quality Assurance/Quality Control program 

• Implementation of a non-conformance and corrective action program 

• Implementation of a new production line for the manufacture of the new 

PowerGuard tile design

• 17% reduction of WIP inventory 

• 17% reduction of floor space required per unit produced 

• Improvements to the design of PowerGuard tiles to improve manufacturability 

• Testing of design changes to ensure that the improvements to manufacturability 

did not compromise performance or endurance of the product

• Improvements to the working conditions in the factory through reduced noise 

level and improved dust collection 

• Implementation of a new Dark I-V test station for PV modules. 

PowerLight is committed to continuous improvement in manufacturing. We are proud of 

the progress we have been able to make due to the funding from the PV Manufacturing 

R&D program. With the help of this program we are making significant progress in 

reducing the cost of photovoltaic systems. 

26
F1146-E(05/2004) 

REPORT DOCUMENTATION PAGE Form Approved 

OMB No. 0704-0188

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, 

gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this 

collection of information, including suggestions for reducing the burden, to Department of Defense, Executive Services and Communications Directorate (0704-0188). Respondents 

should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a 

currently valid OMB control number. 

PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION.

1. REPORT DATE (DD-MM-YYYY)

June 2005 

2. REPORT TYPE

Subcontract Report 

3. DATES COVERED (From - To)

6 December 2001–31 March 2003 

5a. CONTRACT NUMBER

DE-AC36-99-GO10337 

5b. GRANT NUMBER

4. TITLE AND SUBTITLE\ 

 PowerLight Corporation Lean Manufacturing, PV Manufacturing 

R&D Phase I Report: 6 December 2001–31 March 2003 

5c. PROGRAM ELEMENT NUMBER

5d. PROJECT NUMBER

NREL/SR-520-35881 

5e. TASK NUMBER

PVB56101 

6. AUTHOR(S)

L. Hargis and J. Botkin 

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

 PowerLight Corporation 

2954 San Pablo Avenue 

Berkeley, California 94702 

8. PERFORMING ORGANIZATION 

REPORT NUMBER

NDO-1-30628-04 

10. SPONSOR/MONITOR'S ACRONYM(S)

NREL 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Renewable Energy Laboratory 

1617 Cole Blvd. 

Golden, CO 80401-3393 

11. SPONSORING/MONITORING 

AGENCY REPORT NUMBER

NREL/SR-520-35881 

12. DISTRIBUTION AVAILABILITY STATEMENT

National Technical Information Service 

U.S. Department of Commerce 

5285 Port Royal Road 

Springfield, VA 22161 

13. SUPPLEMENTARY NOTES

NREL Technical Monitor: D. Mooney 

14. ABSTRACT (Maximum 200 Words)

PowerLight Corporation (PowerLight) has completed Phase I of its PV Manufacturing R&D subcontract, “PowerGuard 

Lean Manufacturing,” Subcontract No. NDO-1-30628-04. The overall technical goal of this project was to reduce the 

cost of PowerGuard manufacturing while simultaneously improving product quality. This will enable PowerLight to 

scale up production capacity as the market for PowerGuard continues to grow. Through the introduction of worldclass lean manufacturing techniques, PowerLight was to cut out waste in the manufacturing process of PowerGuard. 

The manufacturing process was to be overhauled with an objective of removing as much as possible those steps that 

do not add value to the product. Quality of finished goods was also to be improved through the use of statistical 

process control and error-proofing in the manufacturing process. Factory operations were also to be addressed to 

streamline those factory activities that support the manufacturing process. This report details the progress made 

toward the above listed goals during the first phase of this subcontract. 

15. SUBJECT TERMS

PV; manufacturer; coating process; module; extruded polystyrene (XPS); lean manufacturing; cost; quality; statistical 

process control; 

16. SECURITY CLASSIFICATION OF: 19a. NAME OF RESPONSIBLE PERSON 

a. REPORT 

Unclassified 

b. ABSTRACT 

Unclassified

c. THIS PAGE 

Unclassified

17. LIMITATION 

OF ABSTRACT

UL 

18. NUMBER 

OF PAGES 

19b. TELEPONE NUMBER (Include area code)

Standard Form 298 (Rev. 8/98) 

Prescribed by ANSI Std. Z39.18