ORL NO. 154 DOE/JPL 955893DRO NO. MA-7 DISTRIBUTION CATEGORY UC-63
Irrtegrated ResidentialPhotovoltaic ArrayDevelopment
QUARTERLY REPORT NO. 1
PREPARED UNDER JPL CONTRACT 955893REPORT DATE: APRIL 10, 1981PREPARED BY: G.C. ROYAL, III
The JPL Low-Cost Solar Array Project is sponsored by the U.S.Department of Energy and forms part of the Solar PhotovoltaicConversion Program to initiate a major effort toward the develop.meet of low-cost solar arrays. This work was performed for theJet Propulsion Laboratory, California institute of Technology byagreement between NASA and DOE.
AIA Research Corporation
1735 New York Avenue, N.W.
Washington D.C. 20006
This report was prepared as an account of work sponsored by the United StatesGovernment Neither the United States nor the United Steles Department ofEnergy, nor any of their employees, nor any of their contractors, subcontrac-tors, or their employees, makes any warranty, express or implied, or assumesany legal liability or responsibility for the accuracy, completeness or usefulnessof any information, apparatus, proeuct or process disclosed, or represents thatits use would not infringe privately owned-rights.
ii
ABSTRACT
This first quarterly report on a contract to develop an optimal inte-
grated residential photovoltaic array describes sixteen conceptual
designs produced by eight teams. Each design concept was evaluated by an
industry advisory panel using a comprehensive set of technical, economic
and institutional critaria. Key electrical and mechanical concerns that
affect further array sub-system development are also discussed.
Three integrated array design concepts were selected by the advisury
panel for further optimization and development. From these concepts a
single one will be selected for detailed analysis and prototype fabrication.
The three conccpts selected are the following:
1) An array of frameless panels/modules sealed in a "T" shaped
zipperlocking neoprene gasket grid pressure fitted into an
extruded aluminum channel grid fastened across the rafters.
2) An array of frameless modules pressure fitted in a series of
zipperlocking EPDM rubber extrusions adhesively bonded to
the roof. Series string voltage is developed using a set of
integral tongue connectors and positioning blocks.
3) An array of frameless modules sealed by a silicone adhesive
in a prefabricated grid of rigid tape and sheet metal attached
to the roof.
i i i
TABLE OF CONTENTS
SECTION PAGE
1 Summary . . . . . . . . . . . . . . . . . . . . . . . . 1-1
2 Introduction . . . . . . . . . . . . . . . . . . . . . 2-1
3 Technical Discussion . . . . . . . . . . . . . . . . . 3-1
3.1 Evaluation Criteria
3.2 Description of Concepts Considered
3.3 Concept Evaluation
3.4 Concept Selection
4 Concl,isi ons and Rt :!3nenda* i cns . . . . . . . . . . . . 4.1
LIST OF TABLES
TABLE NUMBER PAGE
Table 1. Tabular Summary of Integrated ResidentialPV Array Design Concepts . . . . . . . . . . . . 3-10
LIST OF FIGURES
FIGURE NUMBER PAGE
2-1 Design Team, Workshop Lectures, AdvisoryPanel . . . . . . . . . . . . . . . . . . . . . 2-3
2-2 Project Activity Diagram . . . . . . . . . . 2-43-1 Design Concept 1 Electrical Characteristics . . . 3-123-2 Design Concept 1 Mechanical Characteristics . . . 3-133-3 Design Concept 2 Electric<l Characteristics 3-1"3-4 Design Concept 2 Mechanical Characteristics 3-15
3-5 Design Concept 3 Electrical Characteristics . . . 3-16
3-6 Design Concept 3 Mechanical Characteristics . . . 3-17
3-7 Design Concept 4 Electrical Characteristics . . . 3-18
3-8 Design Concept 4 Mechanical Characteristics . . . 3-19
3-9 Design Concept 5 Electrical Characteristics . . . 3-20
.)-10 Design Concept 5 Mechanical Characteristics . . . 3-21
3-11 Design Concept 6 Electrical Char cteristics . . . 3-22
3-12 Design Concept 6 Mechanical Characteristics . . . 3-23
3-13 Design Concept 7 Electrical Characteristics . . . 3-24
3-14 Design Concept 7 Mechanical Characteristics . . . 3-25
3-15 Design Cuncept 8 Electrical Characteristics . . . 3-263-16 Design Concept 8 Electrical Characteristics . . . 3-27
iv
LIST OF FIGURES (CONT'D)
FIGURE NUMBER PAGE
3-17 Design Concept 9 Electrical Characteristics . . . 3-283-18 Design Concept 9 Mechanical Characteristics . . . 3-293-19 Design Conce p t 10 Electrica l, Characteristics . . . 3-303-20 Design Concept 10 Mechanical Characteristics . . . 3-313-21 Design Concept 11 Electrical Characteristics . . . 3-323-22 Design Concept 11 Mechanical Characteristics . . . 3-333-23 Design Concept 12 Electrical Characteristics . . . 3-343-24 Design Concept 12 Mechanical Characteristics . . . 3-353-25 Design Concept 13 Electrical Characteristics . . . 3-363-26 Design Concept 13 Mechanical Characteristics . . . 3-373-27 Design Concept 14 Electrical Characteristics . . . 3-383-28 Design Concept 14 Mechanical Characteristics . . . 3-393-29 Design Concept 15 Electrical Characteristics . . . 3-403-30 Design Concept 15 Mechanical Characteristics . . . 3-413-31 Design Concept 16 Electrical Characteristics . . . 3-423-32 Design Concept 16 Mechanical Characteristics . . . 3-43
g
v
iSECTION 1
SUMMARY
This report discusses the first of three tasks to dofine an integrated
residential photovoltaic array. An optimum array configuration will satisfy
the needs of the earliest and largest market and provide electricity for the
least life cycle cost. This study emphasizes a systems approach to design
optimization that considers detailed electrical, mechanical, economic and
institutional factors. Further emphasis is the minimization of cost drivers
for these factors at several levels of annual production.
The study began with the competitive selection of 8 teams to produce a
set of design concepts. A workshop was conducted to review the current
technology base for residential photovoltaic systems. Workshop materials
referenced the following module/array topics: circuit design and perfor-
mance; wiring; mounting; installation, reliability and maintenance; codes
and standards; roof construction; and life cycle cost. These materials
were drawn from previous system definition and array requirements and 12
prototype designs for which detailed array and system analyses have been
performed.
The teams develop'd a total of 16 design concepts over a nine-week
period. Each concept was evaluated by an industry advisory panel convened
by the AIA/RC on the basis of the following criteria categories: market
penetration; fabrication requirements; design and specification requirements;
installation requirements; operation requirements; and maintenance require-
ments. Three design concepts selected for further development by the
advisory panel follow:
1) an array of frameless modules sealed in a zipperlocking neoprene
gasket grid in a grid of aluminum channels fastened across the
rafters;
2) an array of frameless modules sealed in a zipperlocking EPDM
extrusion adhesively bonded to the roof; and,
3) an array of frameless modules sealed by a silicune adhesive in
a prefabricated grid of rigid tape and sheet metal attached to
the roof.
1-1
This report summarizes the assumptions, rationale and methodology used
in the selection of the design concepts. Further concerns to be addressed in
subsequent study activities are also discussed.
1-2
SECTION 2
INTRODUCTION
The objective of this study is to develop optimal roof mounted arrays
for residences that provide energy for the least life cycle cost. Develop-
ment of an optimal array will follow an integrated systems approach that
considers detailea electrical, mechanical and environmental requirements,
as well as such regional variations as codes, construction practices and
local costs. The resulting array design will be fabricated in a prototype
partial roof/array model to identify additional roof array interface
concerns in prcduction, manufacturing, instailation or maintenance. Pro-
gram activity is organized into the three tasks listed below.
Task 1 - Alternative Design Concept Development
Task 2 - Preferred Design Concept Optimization
Task 3 - Prototype Roof/Array Section Fabrication
In Task 1 three (3) generic integrated photovoltaic ar:ay design
concepts are selected from a number of alternative concepts for residential
applications. This effort began with a solicitation to over 200 architects,
engineers, homebuilders and designers that asked for a statement of their
caoability to develop design concepts tc satisfy technical, economic and
institutional concerns. An industry advisory panel was convened by the
AIA/RC to select the most capable ,seams to develop a set of design
alternatives.
A workshop held at the AIA/RC for the design teams was used to esta-
blish a uniform starting point for the nine week concept design period.
The workshop was organized into three sessions. First an overview of
program activities and research results was presented. Next, project
activities and concept documentation requirements were reviewed. Then a
series of technical presentations were given for the following topics:
system design; module design; wiring and connector design; safety stan-
dards; and residential roof construction.
At the end of the concept design period, a presentation was given by
each of the eight design teams tc the advisory panel. The following
characteristics were reviewed in the presentation for each of the 16 con-
cepts developed: appropriateness for earliest and largest market
2-1
penetration; fabrication requirements; designed array output, modularity
and specification; array circuit design, wiring and module connection;
panel/module attachment; installation requirements; operation and
maintenance requirements; and, costs. Three concepts were selected b the
advisory panel for further development, prior to selection of a preferred
design for Task 2.
Design teams, workshop participants, and advisory panel members are
identified in Figure (2-1).
Based on the results of Task 1, one design concept will be selected
for further analysis and development under Task 2. Detailed production
design development and engineerinq trade-off studies will be performed
to further optimize the design for minimum life-cycle cost for the
installed array. Based on this detailed information, refined life-cycle
cost estimates will be generated for annual module production levels of
10000, 50000, and 500000 m2 . A se' or drawings and specifications will be
prepared to permit fabrication, installation and operation of the array
design by a third party. In addition, a full-scale prototype section/array
roof will be defined and a fabrication cost estimate prepared.
The Task 3 activity will include the fabrication on a full-scare
representative prototype section of the selected residential photovo'ta'c
array complete with electrical and mechanical interconnertors and array/
roof interface hardware. While this prototype section r;eed not be
electrically operational, it will serve as a useful model to identify
additional fabrication, installation, maintenance and other concerns.
A block diagram of program activities is shown in F i g ure (2-2). As of
this reporting date, all effort has been completed under Task 1 with the
exception of further development of the three selected conceots. This
report describes the results of the activities completed.
2-2
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SECTION 3
TECHNICAL DISCUSSION
This discussion summarizes key elements of the criteria, methodology
and rationale for selection of three design concepts from those considered.
The first section is a discussion of the assumptions and evaluation
criteria used in concept selection. The next section is a description of
each design considered. Subsequently, evaluation methodology is described
and major concerns for each concept are identified. Then, the rationale
and justification for selection of three concepts is pr,:sented.
she classification of mounting types in this study is based on a
performance approach. This approach distinguishes between mounting types
based on the method used to satisfy two roof functions: weather protection
and structural stability. This classification does not consider height
differences between array surface and roof, or material replacement.
Integral-mounted arrays provide ooth permanent and tempo rary weather
protection. Replacement support for lateral roof loads is required.
Modular array-edge support is required.
Direct-mounted arrays provide only permanent weather protection.
Replacement s upport for lateral roof loads is not required. Modular array-
edge support may not be required.
Standoff/Rack-mounted arrays do not provide weather protection.
Replacement support for lateral roof l oads is not required. Modular array-
edge support is required.
3-1
3.1 EVALUATION CRITERIA
The spectrum of technical, economic and institutiona' issues that affect
the fabrication, installation and operation of a residential photovoltaic
array have been grouped into six categories of evaluation criteria. Evalua-
tion objectives are the minimization of cost drivers associated with each
category. A partial listing of criteria follows the list of categories
below.
• Market Penetration
• Fabrication
' • Design and Specification
• Installation
9 Operation
• Maintenance
MARKET PENETRATION
The focus of this category is minimization of cost drivers for earliest
and largest market penetration. The characteristics of the maturing market as
well as the mature market are expected to establish a basis for the inter-
relationsh = p of fabrication, installation, residential construction,
operations and maintenance.
• The concept must satisfy the largest middle-income mass market.
• The concept must serve a variety of housing sizes, types, and
roof shapes.
• The concept must allow flexibility of selection by both large
and small volume builders.
9 The concept must allow flexibility in installation timing.• The concept must fit within the typical product delivery and
service chain of the homebuilding industry.
Fabrication
The focus of this category is an optimization of pe.sonnel, material
and equipment requirements from component delivery through shipment of the
assembly. That optimization should consider both number and type of person-
nel, material and equipment throughout the assembly sequence.
• The concept must optimize the mixture of factory and field labor
for array assembly.
3-2
• The concept must minimize the requirements for component inven-
tory.
• The concept must minimize the cost for shipping and handling yE
retain acceptable durability.
Design and Specification
The focus of this category is minimization of project-specific design
engineering. Elements considered include the ability to use equivalent
products, as well as the standardization of code approval, labor coordina-
tion, and engineering documentation.
• The concept must use the design engineering ca pability normally
employed by the builder or contractor.
• The concept must minimize field inspection and approval require-
ments of local building and zoning codes, the National Electrical
Code (NEC), fire codes and insurance warrants.
• The concept must allow use of equivalent materials and products
in standard construction practice.
• The concept must allow flexibility in labor and schedule
coordination that meets standard practice conditions.
• The concept's documentation must follow standard practice for
reliability, performance and cost estimates.
Installation
The focus of this category is minimization of installation time and cost.
Key concerns include array durability during site delivery and storage,
sequence of installation, required tools, equipment, labor and supervision.
An additional concern is minimization of field requirements for field
qualification and acceptance of the installed array.
• The concept must have little impact on the normal structural
and environmental exposure of the building.
• The concept must be compatible with standard construction
practices, tools and equipment.
• The concept must minimize field approval of electrical
connections, field cabling and grounding.
• The concept must minimize safety risk during installation.
• The concept must optimize handling and installation durability.
3-3
3-a
• The concept must optimize mechanical attachment and electricalconnection requirements.
Operation
The focus of this category is the optimization of reliable output
performance to match the requirements for system interface consistent with
standard safety conditions.
• The concept array must generate electricity within an acceptable
output range for size and temperature conditions.
• The concept array output must satisfy balance of system inter-
face requirements such as input voltage.
• The concept must minimize grounding concerns and requirements.
• The concept must address appropriate power and dimensional
modularity concerns.
• The concept must satisfy lifetime reliability and durability
conditions at an acceptable cost.
Maintenance
The focus of this category is the optimization of field maintenance,
repair and replacement consistent with least initial costs.
The concept must minimize the requirements for identification,
removal and replacement of failed parts consistent with reliability
and durability conditions.
• The concept must not interfere with normal building maintenance
and repair.
• The concept must minimize added life safety and building risks.
3.2 DESCRIPTION OF CONCEPTS CONSIDERED
Design concepts were developed by eight design teams for each of four mounting
strategies. In certain cases, the concepts were appropriate for more than one
mov,iting type. The following discussion summarizes key elements of concepts
developed for each of the mounting strategies. A tabular summary of system
descriptions is listed in Table ( 11. Condensed drawings of each concept
follow and appear as Figures 3-21 through 3-33.
Integral Mounting Concepts
Sample 1. Eighteen (18) unframed panels/modules are pressure fitted in a "T"
shaped neoprene gasket grid and sealed by a ziplocking strip. The
gasket grid is pressure fitted into an aluminum channel extrusion
grid fastened across the rafters. Array voltage is developed
along the roof height using a series string of two (2) panels/
modules. Array current is developed along the roof length using
nine (9) panel/module pairs attached to busbars at the top and
bottom of the array. Array termination is near the gutter along
the roof rake.
Sample 2. Ten (10) panel frames each made from two extruded aluminum carriage
pieces joined by lateral angles are bolted along the rafters. Each
of the nine (9) modules pressure fitted in a panel overlaps the
lower one and is held in place by a lap bar. The modules are
wired in series by commercially available 'quick connectors' with
return branch conductors attached to the rafters. Array voltage
is developed along the roof height from two (2) adjacent panels
wired in series through a junction box for each panel pair. Array
current is developed along the roof length from the five (5) panel-
pair junction boxes wired in parallel within the attic near the
ridge using redundant armored bus cable conductors.
Sample 3. Eighty (80) frameless modules are sealed using a silicone adhesive
to a prefabricated grid of rigid tape and metal channels bolted
across rafters. Array voltage is developed along the roof length
using a series string of 20 modules. Array current is developed
along the roof height using 4 parallel-wired module rows.
i
3-5
Integral Mounting Concepts (Cont'd)
Sample 4. Forty (40) gasketed modules are sealed in a set of prewired mounting
channels nailed along the length of the rafters. Array voltage is
developed along the length of the roof using a series string of 20
modules. Array current is developed along the height of the roof
using two (2) parallel-wired module rows.
Sample 5. Twenty-four (24) unframed modules are pressure fitted between a
series of extruded aluminum batten strips and plywood support strips
mounted along the rafters. Waterproof seal is provided by butyl
glazing tape at the top and sides of the modules. Array voltage
is developed along the roof length using three (3) modules wired in
series. Array current is developed along the roof height from
eight (8) branch circuits installed in three (3) rows. The bottom
row contains two (2) branch circuits while each of the two upper
rows contain three (3) branch circuits. Array termination occurs
in the power conditioning eyiupment room beneath the array.
Direct Mounting Concepts
Sample 6. Fifty-six (56) unframed modules are pressure fitted in a grid of
thermoplastic "T" and "I" shaped glazing gaskets fastened to the
roof. The "I" shaped sections have been coextruded with embedded
busbars for parallel module wiring. Each module rests on a ribbed
plastic backing sheet. Array voltage is developed along the roof
length from a seven (7) module series string wired through junction
boxes located in the attic. Array current is develo ped along the
roof height from eight (8) modules wired in parallel through the
integral busbars within the thermoplastic grid. Array termination
occurs through the ridge vent in the attic.
Sample 7. Eighty (80) frameless modules are sealed by a silicone adhesive
in a prefabricated grid of rigid tape and sheet metal attached to
the roof. Array voltage is developed along the roof length using
a series string of twenty (20) modules. Array current is developed
along the roof height using four (4) parallel-wired rows.
3-6
Direct Mounting Concepts (Cont'd)
Sample 9. Forty (40) gasketed modules are sealed in a set of prewired mounting
channels mechanically fastened to the roof. Array voltage is
developed along the length of the roof using a series string of 20
modules. Array current is developed along the height of the roof
using two (2) parallel-wired module rows.
Standoff Mounting Concepts
SaTple 9. Forty (40) unframed modules are pressure fitted in a series of
zipperlocking EPDM rubber extrusions adhesively bonded to the roof.
Array voltage is developed along the roof height using six (6)
series-wired modules interconnected by integral tongue connectors
and positioning blocks. Array current is developed along the roof
length using five (5) branch circuits. Array termination occurs
near the gutter.
Sample 10. Eighteen (18) framed and sealed panel/modules are fastened to 30
unequal leg "T" shaped brackets bolted to the rafters. The
longest leg of each bracket is overlapped by an existing shingle.
Array voltage is developed along the roof height using a series
string of two (2) panels/modules. Array current is developed
along the roof length using nine (9) panel/module pairs attached
to busbars at the top and bottom of the array. Array termination
is near the gutter along the roof rake.
Sample 11. Twelve (12) aluminum framed panels with laterally supporting "T"
struts are clamped to a standing seam insulated metal roof deck
mounted on the rafters. Each of the ten (10) gasketed modules
pressure fitted in a panel frame are wired in series by commer-
cially available "quick-connectors" beneath the modules. The
return branch conductor is placed along the standing seam within
the conduit formed by the panel frame and a continuous finish cap.
Branch wiring is routed beneath the ridge flashing into the attic
space below. Array volta ge is developed along the roof height
from two (2) panels wired in series through a junction box for
each panel pair. Array current is developed along the roof length
3-7
Standoff Mounting Concepts (Cont'd)
Sample 11. from the six (6) panel-pair junction boxes parallel-wired withinont
the attic near the ridge using redundant armored bus cable conduc-
tors.
Sample. 12. Forty-two (42) unframed modules are pressure fitted in a series of
Zipperlockine EPOM rubber extrusions adhesively bonded to the
roof of a manufactured house. Array voltage is developed along
the roof height using six (6) series-wired modules interconnected
by integral tongue connectors and positioning blocks. Array
current is developed along the roof length using seven (7) branch
circuits. Array termination occurs near the gutter.
Sample 13. Twenty-four (24) framed panels/modules are pressure fitted in five
(5) "T" shaped tracks along the length of the roof. Each track is
lag-bolted to the rafters through a neoprene gasket strip. Array
voltage is developed along the roof length using a series string
of six (6) pin connected panels/modules. An integral wiring
harness within each track terminates at a junction box on the
high voltage side of the series string. Array current is developed
along the roof height from four \'4) track junction boxes connected
by flexible conduit. Array termination near the gutter is made at
a seal fitted roof penetration.
Sample 14. Eighty (80) gasketed modules are pressure fitted between a series
of PVC hold down caps and extruded aluminum channels fastened to
the roof. Array voltage is developed along the roof height from
eight (8) series-wired modules mounted as two adjacent colunns,
each of four modules. Array current is developed along the roof
length from ten (10) series strings that each terminate in standard
junction boxes beneath the roof.
Sample 15. Eighty (80) gasketed modules are mounted over a series of contin-
uous metal pans and pressure fitted in steel battens fastened to
the roof. Array voltage is developed along the roof height from
eight (8) series wired modules mounted as two adjacent columns,
each of four modules. Array current is developed along the roof
length from ten (10) series strings that each terminate in stan-
dard junction boxes beneath the roof.
3-8
Rack Mounted Concepts
Sample 16. Eighty (80) gasketed modules are pressure fitted in a series of
PVC hold down caps and extruded aluminum channels bolted to a
slotted steel rack. Array voltage is developed along the rack
height from eight (8) series wired modules mounted as two
adjacent columns, each of four modules. Array current is
developed along the rack length from ten (10) series strings
that each terminate in standard junction boxes.
3-9
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RG A-1 -CENTERS TRUSION
a^-
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DESIGN CONCEPT 10 ELECTRICAL - FIGURES-14
VEKjILAI, i^T1AK1
^--- QUIGIC GOf.IUF.(^."^
wof_..__.. fv/ &L.s hh
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3-30
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DESIGN CONCEPT 10 MECHANICAL FIGURE 3-20
NoF-IZONTk^^EGTION
3-31
Aaf
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BR,AA./CN r0 B[./-r Q,A R W/R/NG.r, r. s.
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DESIGN CONCEPT 11 ELECTRICAL - FIGURE 3-21
-
w
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3-33
DESIGN CONCEPT 12 ELECTRICAL - FIGURE 3-23
NON-ELECTRICAL
MODULE TO MODULEELECTRICAL
MODULE TO MODULE nacre -w-VI VCT4I CA.
434 1, z Sly" COWL BELOW U.S.E. BUS TERMINAL TERMINALP.Y. MODULE (TYPICAL) MODULE CABLE BLOCKS ATYPICAL) BLOCKS
(TYPICAL)
NOTE: CABLERUNS UNDER MODULESAND IS CONNECTED
AT TERMINAL BLOCKS
I I Y. . rv101uc ""' I
I ^ y I /,
I 1
Tb4 UWU- TCW.LG
CAru
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FL,n4j VISA/ ! ENT7 VIA/.-
^ i
4
^ I
---,NwG A4 Cf-r• 1, BUS CABLE(1^4' TOTAL QD.)
- - - I^UL/STK^IJ I^ ^F"A:t1.nb.f[ IWIV!"
L WIRE FOPCEDINTO PLACEf OVER KNIvES 3Y CLOSING
-LANPING BAW
`JI(Z VIL'W
T`
3-34
RADIANT HEAT \ ^^REFLECTING FOILAPPLIED TO HOTTTIMOF TRUSS CHORD
BUS CABLE TO CONTROL ROOM ROOF
SELF-FLASHING COWL
ROLL ^^^333 r :" I.D.
ROOFING ^_•.' ^^kPDH GROMMET
DETAIL OF ENTRY COWL (N.T.S.)
Wn-" im A ►YJI; ^JC'ENTRY COWL
ROLL HOOFING
All
HOOF DECK
ILO ^/^ - CLalt^HOOF TAM
IN
/ GIDAIf1W. VH.J1L Y7PtIT WJT
)AT AS CLOSEDry
DESIGN CONCEPT 12 MECHANICAL - FIGURE 3-24
CLS1hJtYt1'^ viWL F4oGG VaJT —\—L^1^'"\'^ J I ...I
. _ioG 'MKMWAL eLMX -'—
tT'CM..MOIJ►.RMJ',^ CXTRIJ^IC7.^ --^
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FOOT
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Fl . A-1 -CENTER EXTRUSION
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3-35
DESIGN CONCEPT 13 EIECTF
1UNGTIOU IFR IGURs
ROOT $SALRICauRa
F 1 GURt 1ARRAY A-5eEMSLY
DOIL wIIl1YG=1 O AWGI.U1d WINCINGINGONDuIT
- I I- * I I- * i 1- + ,Jov I24Ov
:ovYom)
X12,
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I.zov
^TiM ^ G^NNi GTO IL .V^t^^ * ^
^^^ ^ ^ ^ FLlrlsl[o ^+Ou 17
^t MiT RAn 04^4"_ `. TMROUC•H ;OOP
sal p ' W Ili i.ITEM :- 4' . 4' MODULI, sown ^^ouNfJJ - D^i3D,(ALT[R MAT I . 2'. V" 0 ZAC:.ti wa -^MOOIJLLS)• A "AGi14T-L'AGJ^
• ^OLAtLOti' wITN LOG.KJKA9LVICL OM1TTtQ.
3-36
I^J
DESIGN CONCEPT 13 MECHANICAL - FIGURE 3-26
TRACK- A LUMIMUTA[x? ptulbiom -
GONN[GTORGtGURSO TO110-k W 1-
fIGuRG 1
TKAGK (-KQ== IwNoclaaw roamo"-
r.GTORY 16uaGOMNSG-riam
— I
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WLAI-NTIGI4T MATING GOMMM4702L
CC o- IWAG'SaAL ) GIMILAR To AMrING•iOL-RLOGIL JJITNOu. IOGKING' TAlbtk.MODIPM0 TO FORM ASOVS RLUftKA5eG&M&L`f ).
FIGURE jFRA;vie CONNEGTog ASeEMBLY
3-37
DESIGN CONCEPT 14 ELECTRICAL — FIGURE 3-27
colrclw w w'Sam tt: - Y. • "Ate r olotl/l it" an+Me m
fet /lnlnie I1w•1 qq1 ca.eulwta (MINOR
tat0 - Nome• .1 to r. a& ItawM J.
i IOOM aFt Icw.! Wolf wr It19.I /
n atera ow e nc; • "FILM rR A tau = ta ' aPl.n1 a A oat (Iwo .ILAP (in. a sa— e -4 was tae w N►• 1 .q• qw .l a.wN.uls Yrall n terab (119.1rig earl o PLAN SAW" w wnlLM up, PY AIMA1 1100E RAN
aNO rmm swe t. Iwo we wmw o wMI Nelms SMfmck"s "Per Item. na/ w a.lw ru /letft'/.+.1101
-j It nuaw w It M rwrto-Ncla twno atoma a'^^ ^/ :OKA woven
Tli,
rwuaw (sells"tan wMM 1 le'Come ot1n 6006111
nn/.a/wells wall Iwo..
r no
*n OUR ITIV.I
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- a77 RNt: YI nNl
/' / uM.tal MII I{V lot^• Y Ira tlala
7.19 Ned mom INl
m fWot w. tWllae
Hr 1 L.• nN* Gams am not1.IONS "01 n aeeil
%fr t IN• rkIllaw f.Yl 111. r-dIIpInVYNOIa to %= lFYlw
1"Mal: 3411 • /Oea •mlotu. LmLM%L n -^
r i^
( !Hea t elan /on /eMt: ne "LAM Slot 0 I-=M •f ella ttfsurlaw
IIa.1ao .0-M
^^ L " Niue rwlal/ am.am w w.l. a-seta
-alt/ rtteu/ .1n Illtolur ala Ialw N Mai wYF10
W. La aotf .t ltttr.lwt MISIM "1 m .tan (Iw.1
1.0 Y
1" 10 a.. h SN•t1YMte }ar- Ua/. n1YA. 10 ter I. y.^.
NO vtlw.1 wn— -sal cmw t
caawtl
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(T Haletin It Iel
Air" .111 .1111or 'YNY or0'" Meet
1
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PV a p ll ► T FI ICTNtC ► l SCME4aT1iC
3-38
n -gnur( — nf nl^w
^' r n r.rrf ra Tltaw twu •pr,Iti s111tta
I NN•Itl waa^
DESIGN CONCEPT 14 MECHANICAL - FIGURE 3-28
! 101 --^ /1.W .. @tven M RAMIAi^ar wn(s —
slCT10i1 ^1tssra ow
All H<OIIA "limm a: •eir "W nWWII on IMCT PMJr nss
air w" •WNW w
mat, M11rrIA-
r 1 sr rAxu-
mom(_ p• t•__ _ }.-.. - .i
lr _ 1R 4i d ON
A Maua" woo w
11. '1 116
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mcnoM D-O
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1/f' I Vr YbOY1 W f nuYMI[i f aril nn IA1l A 11/►rtr moon (l0 an lufl-
rinitl► XI/iM tiMn 111Y1iIfl — —^
O "A", td f1rM \u1on" rno Wwin \
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3-39
r/ ^ r
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DESIGN CONCEPT 15 ELECTRICAL - FIGURE 3-29
rata+ a9wu wt am wtA llw.l M llama or is r rrlw. slowftff .11I
• Iwo twstlQ h 11AP t0= N utra w N r. MOAp aw
1141, 111&111 A. yY .1911 A. oltllR NI j ,, alaga tM Itw. ltO t^lt^t—t I ,p Oi/tt^ IA sat .- / N A 1Mt OAI/IFR^ it to WAOM tWf (tN, w ".I
tar up-Munau —J9 -was. nil "It. , N19• .t lwO -._ rrn9 n0 (ram. • M)
La ^ N Rlw..tw uluw, PrArwAwt - rtlo up
rIIf9 tomAM11 aft 9[MAO _41111, 00. o.t,Ar
MR* a nw ^ 01111111111,1101111111111,1111I 410.1 ?am to" K IV 6K//r AIINAT NOW PAN
6sA6a /Mr
NA -wr t wr tlwl ow"tvwnul na9rtAO tea/
wr t 1/Y MLONNO ^ MaL[7.111,1111 sow. I9-""rKsas if rrlO
d A/e16 gifts I.wfor 101AO un s Jaw
rim ^ sl.w J..ow
rn9 CLM •'^ Yt• 6KI9 mom tMfr
K 9A9 JOla9
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/V ARRAY VLICTTtICAL SCHFMATSM seats
3-40
a—Ttarty fla^ 1
.nn umtw Wn
rta-au IsMlfita M*nlnt oai; att ►mottatttlttta*%W P%AMWQ/M[TAL 0[CK 1^^
Wo" t.e►r
rarl. etp.1^ ter
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vwbl ltt0 vm[it lalg4LA" w
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DESIGN CONCEPT 15 MECHANICAL - FIGURE 3-30
Vt► Nos eai 1 -L
arras
I$gSnRN A-A
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lay Mrtta 1'lli^ \ _ ^i'/^ `. I. / la
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3-41
A
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DESIGN CONCEPT 16 ELECTRICAL - FIGURE 3-31
. iliir (wcta iillrl. 1^a • ^.Aiwa .(r rrnn ^(ln. I tiw tr it w w ~I4tiwl N tt/wwl
- w ^^, n Nl• i u lw. lrir w (lilil MI ^ —mww/ rrl. nul. (q,10mv e-t ^Tiw.i r
W la w t. nrnt A w 3owl A "a mmom140,0011111111Mae tawimaim140,0011111111
utMIIOw), J nlnc
lNll t. "scl (1Ml It" k rlint+0t7 ttol .Ni. w law t _ &W lwl r. Uwmtr. tol4 wav
SCUTN 00040 w &MAY 1100/ PLAN0MMTH Qmxv t0tLxfk-T-
—T
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1171.t
M •i01Ai ter M.
unlnri
w "WAX"W w rt
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►Y ARRAY nICTOiCAL 109HO AT1^l.• .e u
— .511itwiw rlt•w 1r mum inumm"
-rnwl llllnl ,wnrii l lawN n V * t/lr[1r " l/Al A~ two. IF a
r rwY lwir wow f1w. w t mltr►
— N Pon w w a. rwY st(nw 8101 to 31W t w /l/wltwo W0001, an tiw ru tOrlw nwiw.n ~
3-42
.- -ve. some v I/li/f fairw 'lIM/ M7MVM,lf. t.^, tlr \
1
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DESIGN . CONCEPT 16 MECHANICAL - FIGURE 3-32
al"WA visa & ftwit ItimMllwf y r room t.yr 1 t't: YIrAI N Itk 1.:—\UIN'111vfAnnn.le!. no I lf.c— —
I!. Y, AL. Ittlsa4
re w. w. taro Im.of w w. "GUArf xii,
`Ir.• UA ma,lf ott vivo MI/tffeM N Ysaatltaf It*.)
1811tr hlm IvNr1A MILI
-YN' r./rgtlf it Iw.nMnl.. lift"' 1..Vr 1 fir It W &ash lol.-
&.,tt trra7 Irw. tv • wroo
•--IH -f t... q . M. Wr.. 1..st1 w. w. M 177x.1
orw7 y ^fl.
in ~mmMCTIOM C-CKW VI'Ir
rlren. ,I.ra Iry w pw. ► r^1,•,
W of lrw Ir►wu411rf ^
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3.3 CONCEPT EVALUATION
Key evaluation objectives include: a) identification of major concerns
that affect concepts using the criteria discussed in Section. 3.1; and,
b) identification of each concept's significance in the optimization of
three generic concepts for least life cycle cost. Two stages of evaluations
were conducted following each team's concept presentation.. Major concerns
for proof of concept were assessed by the advisory panel using the market
penetration, fabrication, design and specification, installation, operation
and maintenance criteria. Then statistical methods were employed to rank
t.ne significance of each concept for cost optimization.
Factors that affect development and evaluation of all design concepts
are first discussed. Next factors that affect optimum use by mounting type
are summarized, followed by an identification of major concerns for each
concert. Factors that have broad applicability to design concept develop-
ment have been grouped into several major categories. A discussion of key
assumptions and evaluation observations in each category follows their
listing below.
e circuit configuration and wiring
e alignment and attachment
e reliability and operation
e codes and standards qualification
e roof construction practices
e life cycle cost estimation
Circuit Configuration and Wiring
An important assumption used was that array voltage is developed to
satisfy the voltage window of present day inverters to produce 240 Vac single
phase output for residential loads. Key considerations include: minimization
of busbar length; minimization of grounding needs; optimization of electrical
potential location and proximity; minimization of field electrical connections
and cabling; and optimization of circuit design to improve performance
reliability.
If module grounding needs can be minimized, major cost benefits from
reductions in the number of field connections can be realized using module
voltages higher than 30 Vdc at -200 C to reach present day inverter input
voltage requirements. Generic circuit configurations either develop array
3-44
voltage along the raof height with current along the roof length, or voltage
along the roof length and current along its height. In the first configuration
constant electrical potential along the eave can be maintained, as a safety
precaution, while for the second wiring costs associated with busbar length
can be minimized.
Alignment and Attachment
Major alignment concerns include minimization of individual module
positioning, reduction of cumulative positioning error and reduction of rough-
framing to finished-trim tolerance error. Panel/module attachment at the
roof/array interface must be durable and constructionally stable. The inter-
face must prevent water penetration, thermal expansion, and other environmental
hazards from causing damage to either the array or the residence. Important
criteria to evaluate the effectiveness of attachment was whether the array
surface serves as a watertight membrane. Live loads, dead loads, snow and
wind loads have been considered on a regional basis to ensure that damage to
the array or residence will not result.
Reliability and Operation
A major assumption was that module replacement would occur once every
four years, for a total of five replaced modules over the twenty-year service
lifa of the array. Among the types of degradation expected: soiling was
assumed to be minimized by nav;ral washing processes, assisted by some home-
owner upkeep; yellowing and insulation breakdown was assumed to be minimized
by ptimized module design. A fixed cell failure rate from cell cracking was
assumed to have a nominal value of one per ten thousand per year. Fatigue
and corrosion resulting in module wearout was expected to occur after 25
years.
Codes and Standards Qualification
While efforts are underway to incorporate photovoltaic systems in building
codes, specific provisions for photovoltaic arrays are not yet included.
Currently, arrays incorporated into or built onto roofs may be evaluated
under existing codes using requirements for such diverse elements, depending
on array mounting type, as roof coverings, roof structures, skylights, and
veneers. It was assumed that successful integration of the array/roof inter-
face will guide solutions to the inconsistencies of code inspection and approval.
3-45
Roof Construction Practices
Not only did evaluation of each concept consider ease of array installa-
tion preferably requiring minimal tools and expertise, it also considered
minimal departure from standard building construction practices. A key issue
of standard practice is dimensional modularity of rafter or trussed roof
framing as well as that of sheathing and roofing materials. Minimal impact on
framing will permit continued use of standard engineering design of chords and
web members provided by truss fabricators in response to critical factors such
as dead loads, concentrated loads, snow loads and truss spacing. Minimal
impact on framing will permit continued use of 3/8 in Group I plywood without
staggered joints or end blocking material using metal "H" clips to provide
the required edge support at the midspan of each truss space. Minimal impact
on roofing material will permit use of the standard 240 lb. (per 100 ft2)
asphalt shingle with a typical life expentancy of up to 25 years that employs
self-sealing tabs to provide extra protection against wind.
Life Cycle Cost Estimation
The cost used throughout the program is the life cycle cost (LCC).
Included in the LCC are the costs of installation and maintenance as well as
the manufacturing cost of the hardware under assumed annual module production
volumes of 50000 m2 , 100000 m 2 and 500000 m2 . The impact of array hardware
choices can be expressed meaningfully only by using LCC methods to reflect
application-oriented and hardware design oriented constraints. An early
evaluation was conducted to identify the life cycle cost sensitivity of
trade-offs between initial costs and replacement costs for an assumed replace-
ment scenario. A result of this study was to focus on minimization of initial
array cost for all of the design concepts considered.
Integral Mounting Concepts
Major concerns in use of integral mounted arrays include weather tightness,
alignment and attachment to rough framed rafters and electrical connection
beneath the roof.
Concept 1 uses a proven and available technology that compares favorably
with other integral concepts. Small array size appears to limit potential
relative cost reductions for such components as flashing and gasketing. Branch
circuit wiring costs appear reduced at the expense of increased internal
panel/module wiring costs. Modules may require non-standard environmental
protection at job site prior to installation.
3-46
Concept 2 combines the technical benefits of prefabricated assembly with
an aesthetically pleasing appearance. Non-standard roof framing and ability
of panel frames to resist racking appear to be the major installation concerns.
A high batten profile that may result in partial cell shadowing appears to be
the major operation concern.
Concept 3 applies a glazing technology developed successfully for the
commercial building industry to residential construction. A key concern is
the grid's ability to resist pre-installation damage and subsequent lift
forces after installation. Another concern is the amount of time needed for
sealant curing.
Concept 4 allows flexibility of either integral, direct or standoff with
minimal electrical wiring cost. One major concern is material continuity at
the intersection of horizontal and vertical mullions. A further concern is
the assurance of a watertight membrane under field conditions.
Concept 5 uses a proven and available technology appropriate for early
market penetration In custom homes. Embrittlement of the butyl tape on wood
members may require flashing for long term reliability. Module size may
require further concern for handling, shipping, snow and wind loading at the
glass thickness specified.
Direct Mounting Concepts
Major concerns in use of direct mounted arrays include weatherability
of roof connections, cell operating temperature penalties, and field cabling
requirements.
Concept 6 provides a good exploration of the potential benefits of
coextruded thermoplastics and embedded metal. Key concerns include mechanical
attachment, module alignment, moisture protection, and installation inspection.
Electrical connection concerns include module movement, access to connectors
and module polarity reversal.
Concept 7 applies a glazing technology developed successfully for the
commercial building industry to residential construction. A key concern is
the grid's ability to resist pre-installation damage and subsequent lift
forces after installation. Another concern is the amount of time needed for
sealant curing.
3-47
Concept 8 allows flexibility of either integral, direct cr standoff
mounting with minimal electrical wiring cost. One major concern is mechanical
continuity at the intersection of horizontal and vertical mullions. Further
concerns include assurance of a watertight membrane.
Standoff Mounting Concepts
Major concerns in use of standoff mounted arrays include protection of
roof penetrations, minimization of additional material and prevention of debris
and vennin collection beneath the array.
Concept 9 relies upon a module interconnector incorporated with alignment
blocks. Mechanical concerns include the need for EPDM gaskets together with
alignment blocks, capability of adhesive to hold array and close tolerances
for fastening. Further concerns include the need for detailing to minimize
collection of debris and vermin. Electrical concerns include handling require-
ments for small interconnects.
Concept 10 uses a proven and available technology that compares favorably
with other integral concepts. Small array size appears to limit potential
relative cost reductions for such components as flashing and gasketing.
Branch circuit wiring costs appear reduced at the expense of increased internal
panel/module wiring costs. Modules may require environmental protection at
job site prior to installation.
Concept 11 applies a concept developed for commercial applications to
residential applications that holds promise to minimize NOCT, and improve
array efficiency. Mechanically, key concerns include: the need for further
study to minimize collection of debris and vermin; the need to further consider
thermal expansions; and the need to minimize special roof framing. Electrical
concerns include significant grounding requirements and partial cell shading
potential.
Concept 12 relies upon a unique module interconnect incorporated with
alignment blocks attached to glazing gaskets. Concerns include attachment of
the alignment blocks to the EPOM gaskets, the capability of the specified
adhesive to withstand loading conditions and close tolerances and handling
requirements for small interconnects. Further concerns include the need for
detailing to minimize collection of debris and vermin.
3-48
Concept 13 focuses on the reduction of module installation alignment and
attachment requirements. Effectiveness of module interconnection is sensitive
to series string location that requires further study to improve interconnect
standardization. Operation concerns include the need for improvement of ice
and water drainage arrested by the horizontal rails. Removal of an entire
row of modules for one module replacement appears acceptable only with high
reliability assumptions.
Concept 14 provides a good representation of present technology capability
and cost using readily available components. Key concerns include prevention
of water leakage and the minimization of field assembled parts.
Concept 15 provides a good representation of present technology capability
and cost using readily available components. Key concerns include the minimiza-
tion of field assembled parts, and the dependence on present module construction
and performance.
Rack Mounting Concepts
Major concerns in use of rack mounted arrays include additional load and
subsequent structural requirements as well as applications limited by total
cost and aesthetic considerations.
Concept 16 provides a good representation of present technology capability
and cost using readily available components. Key concerns include minimization
of structural dead load and resistance to wind uplift.
C-49
3.4 CONCEPT SELECTION
Three concepts were selected from sixteen candidates to represent several
distinguishing characteristics. These characteristics include proof-of-concept
status, innovative design focus, and mounting type.
Concepts were classified into three proof-of-concept stages. Several
concepts that use off-the-shelf components appear currently ready for field
use. Concepts that modify methods, components or materials from other con-
struction sectors or industries may require structural and/or durability tests
prior to field use. Concepts that are based upon new methods, components or
materials may require further prototype development and testing prior to field
use. It was assumed that concept test qualification would require one year.
This would yield concept field applications in two years. Prototype concept
development was limited to two years as one of the program groundrules.
Concept field applications are expected two years after prototype development.
Concepts were classified into three areas of innovative design focus:
module design; wiring; and installation. Innovative module design features
include the use of large area (i.e. larger than lm 2 ) modules with square or
rectangular cells for improved packing density and methods that allow the
safe use of modules with open circuit voltages higher than 30 Vdc at -='00C.
Innovative wiring features include the elimination of wiring harnesses, the
use of ore-wired mounting hardware, and the safe minimization of wire size
and insulation. Innovative installation factors include minimization of
individual module/panel alignment, replacement of mechanical fastening with
mastics, use of pre-cut glazing gaskets, minimization of construction trade
constraints, and minimization of module rows to reduce the complexity of
panel frames.
Concepts using the same mounting type were compared to evaluate the
effects of design trade-offs peculiar to that mounting. Whiie reductions in
hardware/gasket costs contributed the most to lower total-net-installed costs,
the effect of changes in wiring cost, roof support costs, and material
replacement credits was not uniform. Examples of large material replacement
credits did not result in lower costs per peak watt for integral systems.
Additionally, nominal reductions in wiring cost did not y ield significantly
lower integral mounting costs. In either direct or standoff mounting,
savings from roof credits and wiring costs did not significantly reduce
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A
total costs below levels achieved through savings in hardware/gasket installa-
tion.V
The three design concepts selected are identified as concept numbers 1,
7, and 9.
Design Concept 1 represents that group of concepts fabricated with
"off-the-shelf" components using a minimum of assembly steps. This concept
relies on the transfer of skills between the commercial glazing industry and
the homebuilding industry; the use of non-standard construction practices
and tolerances appear minimized. Further design optimization may be required
for array operation and maintenance, dependent upon module reliability
assumptions. Loading, watertightness and attic temperature assumptions may
require verification.
Design Concept 7 represents that group of concepts using modified
techniques, components and materials. It minimizes individual module align-
ment and replaces mechanical Fastening. While the rigidity and durability
of the grid during installation is of concern, there appears to be sufficient
rigidity during operation. In view of the concept's technology basis from
the commercial building market, rigidity, module uplift and deflection may
require empirical verification. Further design optimization may be required
for array installation, dependent upon loading and mounting assumptions.
Design Concept 9 represents that group of concepts fabricated with new
components. Handling connectors of this size is of concern though it appears
that through optimization, standard construction practices and tolerances
can be maintained. Further design optimization in prototype development may
be required, dependent upon module size and reliability assumptions. Loading,
watertightness, and component damage may require empirical verification in
prototype tests.
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SECTION 4
CONCLUSIONS AND RECOMMENDATIONS
Three integrated array design concepts were selected by the advisory
panel for further optimization and development using a comprehensive set of
technical, economic and institutional criteria. The concepts selected are
the following:
1) An array of frameless panel/modules sealed in a "T" shaped
zipperlocking neoprene gasket grid pressure fitted into an
extruded aluminum channel grid fastened across the rafters
using off-the-shelf components.
2) An array of frameless modules sealed by a silicone adhesive
in a prefabricated grid of rigid tape and sheet metal
attached to the roof that minimizes individual module align-
ment.
3) An array of frameless modules pressure fitted in a series
of zipperlocking EPDM rubber extrusions adhesively bonded
to the roof. Series string voltage is developed using a set
of integral tongue connectors and positioning blocks that
eliminates wiring harnesses.
Further design optimization will be undertaken for these concepts to
develop design trade-off data relative to module size, module reliability,
structural loading, watertightness and component damage.
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