Study of PhotoYoltaic Residential Retrofits · Small Power Conditioners, Utility Interactive 48 Projected Total System Costs 50 Life-Cycle Cost Ratio's for $9,000 System 52 Tax Credits

CONTRACTOR REPORT

SAND81-7019/1 Unlimited Release UC-63a

Study of PhotoYoltaic Residential Retrofits

Volume I. Executive Summary

D. E. Mahone, P. L. Temple, J. A. Adams, B. B. Chalmers, A. E. Motter T.E.A., Inc. 7 Church Hill Harrisville, NH 03450

Prepared by Sandia National Laboratories Albuquerque, New Mexico 87185 and livermore, California 94550 for the United States Department of Energy under Contract DE-AC04-76DP00789

Printed April 1982

Issued by Sandia National Laboratories, operated for the United States Department of Energy by Sandia Corporation. NOTICE: This report was prepared as an account of work sponsored by an agency of the United States Government. N.ither the United States Govern­m.nt nor any agency thereof, nor any of th.ir .mploy .... nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any lagalliability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or pro-­cese discloeed, or represents that its use would _ infriDp privately owned rights. Reference h.rein to any specific commarcial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply ita endorsement, recommendation, or favorm, by the United States Government, any ag.ncy thereof or any of their contractors or subcontractors. The views and opinions expressed herein do not necesearily state or reflect those of the United States Governm.nt, any agency thereof or any of their contractors or subcontractors.

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Distribution Category UC-63a

SAND81-7019. Vol. I. Executive Summary Unlimited Release

Printed April 1982

STUDY OF PHOTOVOLTAIC RESIDENTIAL RETROFITS

Vo lume I. Exec ut i ve SUlTlTla ry

D.E. Mahone. P.L. Temple. J.A. Adams. B.B. Chalmers. A.E. Motter

T. E.A •• Inc. 7 Church Hill

Harrisville. NH 03450

Subcontractor:

A.E. Millner Tr i So I a rCorp

10 DeAngelo Drive Bedford. MA 01730

. ABSTRACT

This report analyses the problems and potentials for widespread residential retrofits of PV power systems. Included are data on the existing housing stock. designs for array mounting and system electrical wiring. and economic analyses for retrofits. The report comprises three volumes: Executive Summary. Main Report. and Appendices.

Prepared for Sandia National Laboratories under Contract No. 62-0229

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i ;-11 ------------------------------------------------Acknowledgements

This study has benefited from the thinking and contributions of many people. Principal among these has been John L. Jackson. the Technical Monitor for the project at Sandia National Laboratories. who has been In­volved from the earliest Inception. His active Interest In the project has gone well beyond simple monitoring. and his thoughtful comments and encourage­ment have had a valuable Impact on the outcome.

Another extremely important participant has been Alan Millner. of TriSolarCorp. As subcontractor. he has made numerous and invaluable contri­butions to our understanding of the retrofit implications of electrical phenomena In PV systems.

Richard Tabors. of the MIT Energy Laboratory. sponsored an aerial survey study of PV rooftop availability. done by the Jet Propulsion Labora­tory. He generously assisted in obtaining access to and cooperation from Nevin Bryant. the JPL Project Manager. Dr. Bryant and his associate. Richard Fretz. provided Important data to the study. .

Others who contributed thoughts. comments and advice Include: Edward Burgess. Kent Blrlnger and Gary Jones of Sandia National Laboratories; Ron Ross and Russell Suglmura of the Jet Propulsion Laboratories; Hiles Russell. John Solman and Edward Kern of MIT Lincoln Laboratories; John Schaefer of NMSEI; Gerald Noel and John Hagley of Battelle Columbus Laboratories; and Prof. A.G.H. Dietz of MIT. Many other people Involved with the housing and photovoltalcs industries across the country have helped. They are too numer­ous to mention here. but thel r contributions are gratefully acknowledged.

T.E.A. staff who participated In the project Include: Douglas Mahone, Project Manager; Peter Temple. Chief Engineer; Jennifer Adams and Barbara Chalmers, design and cost estimating; Andrew Hotter. housing characteristics and market penetration; and Lynn Lagasse. graphic design and production coordination. Additional technical support was provided by Carol Boemer. Margaret Fanning. Lisa Heschong. Joseph Kohler. Daniel Lewis. Richard Oswald. Paul Pietz. Victor Reno and Thomas Weller. Barbara Putnam did many of the illustrations. Typing. production and project support work were done by Mona Anderson; Pamela Carlson. Barbara Hann. Mary Kinzel and Karen Mahadeen •

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it I - iv

Preface

Although retrofitted PV systems have been considered since the inception of the National PV program, the design of such systems for resi­dential and commercial buildings has focused, until recently, on new con­struction. While new construction may represent an attractive market for PV systems, the existing building stock may Include a potentially larger retrofit market. particularly In light of the s!ow turnover rate of existing buildings. In addition, a recent survey of residential solar hot water systems has shown that two out of three such systems were installed as retrofits.

Sandia National Laboratories, as manager of both the DOE PV Systems Definition and PV Residential Programs Is charged with the design and test­ing of appropriate PV systems capable of widespread use In private and public sector applications. As part of this charter we have funded two outside contracts to study both residential and commercial PV retrofits. Total Environmental Action of Harrisville. New Hampshire. studied the residential sector and results of their work are presented In this document. SAND81-7019. Study of PV Residential Retrofits. The commerical retrofit work was per­formed by Battelle Columbus laboratories of Columbus. Ohio. Their results are contained in SAND81-7179. Design and Market Study of Retrofit Photo­voltaic Systems for Commercial BuIlding Applications. Additional copies of both studies may be obtained from these organizations or from Sandia National Laboratories, PV Systems .Definition Division.

J.L. Jackson Sandia Technical Monitor

v

VOLUME I EXECUTIVE SUI1MARY

Table of Contents Acknowledgements

Preface iii

Table of Contents v

O. Introduction

I • Objectives 3

I I • Conclusions 4

I I I • Characterizations of Res i den t i a I Sui Idings 7

I V. National Power Production Potential 15

V. Array Architectural Design 21

VI. System Electrical Design 41

V II. System Costing and Economic Analysis 49

V III. Conclusions and Recommendations for Further Study 57

IX. Annotated Contents - Volumes II & III 59

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vi

LIST OF FIGURES

Executive Summary

Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 FIgure 18 Figure 19 Figure 20

Housing Units and Structures U.S.Total Representative Residences Miami .- Ft. Lauderdale Representative Residences Hartford - New Haven Representative Residences Los Angeles Solar Economic Regions % Maximum Performance (Annual Basis) Madison, WI Adaptation to Roof Shape: Minimize Wasted Area Roof Area Generally Available for PV's Possible String Orientations Module Handling String Geometry and Size (two modules) Framed Panel Metal Pane 1 Vertical Gasket

a-h Vertical Gasket: Steps One through Eight Schematic of Recommended System Wiring Paralleling Junction Box/Inverter In Garage Inverter Enclosure/Paralleling Junction Box Effect of System Cost on Life-Cycle Cost Ratio Effect of Fuel Cost on Life-Cycle Cost Ratio

LIST OF TABLES

Executive Summary

8 11 12 13 16 24 25 26 26 27 27 31 33 35

36 - 40 42 46 47 53 55

Table 1 Table 2 Table 3 Table 4

Number of Residential Structures by Region (millions) 7

Table 5 Table 6 Table 7 Table 8 Table 9 Table 10

Buildings Suitable for PV Retrofit 9 Usable Roof Area for Retrofit 10 Power Production Potential from Residential

Photovoltalc Retrofits 18 Small Power Conditioners, Utility Interactive 48 Projected Total System Costs 50 Life-Cycle Cost Ratio's for $9,000 System 52 Tax Credits Required to Make PV Systems Cost Effective 52 Effect of Electric Codes on the LCCR of a $9,000 System 54 Barriers to Energy Conservation Retrofits 56

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O. INTRODUCTION

We have dIvIded thts report Into three volumes, in order to present the material at three different levels. The Executive Summary, this first volume, summarizes the most important conclusIons, and capsulizes the prin­cipal discussions of the study. It Is Intended to be a shortened, stand­alone version of the study report, and so provIdes more information than a simple presentation of the "bottom line." The second volume, the main body of the report, contains full descriptions of the methodologies used, along with deta·i1ed technical discussions of the various topics important to residential photovoltaic retrofits. The final volume contains the Appendices, which provide back-up material that Is too detailed· or bulky for the main report. The Appendices are included for the reader who Is Inter~sted in closely following how the work lead to the conclusions.

T~e major goal of this study was to provide a comprehensive analysis of the potentials and problems of retrofitting PV power.; systems into the Amer­ican housing stock. The starting point, both for estimating the national retrofit potential and for designing retrofit PV systems, was to gather data on the existing housing stock. This came both from published sources and

from field surveys. Major findings included the total numbers of residential buildings, and their physical characteristics, such as roofing material and type. Typical house types were selected, and field survey data was gathered, to provide a real-world context for developing retrofit designs. This data lead to the calculation of the size and number of retroflttable rooftops.

Once the potential numbers of retrofits and their size was known, we estimated how much electric power could be produced with full market penetra­tion of retrofit PV systems. To do this, we developed estimates of system performance and of economic feasibility of retrofits In different regions. Areas of the country where retrofits would be uneconomic were factored out of the total projected retrofit numbers. Estimates of retrofit potential also were Influenced by the details of system design and costing developed in other phases of the work.

From our understanding of the physical characteristics of U.S. hous­ing, we designed array mounting systems and wiring schemes for retrofitting PV systems onto residentIal rooftops. This work addressed several key as­pects of the array architectural desIgn, such as the concerns and nature of the residential building industry, the potential problems presented by build­ing and electrical codes, and the effects of tilt, orientation and other system details on performance. The work resulted in our recommendations for residen­tIal module size and design, and a set of recommended mounting system designs for putting arrays onto residential rooftops.

2 O. INTRODUCTION

The configuration of our recommended PV arrays, as well as the charac­teristics of residential power conditioners and utility company requirements for grid-connected PV systems, had implications for the electrical design and wiring details of the PV systems. We explored several key aspects of system· electrical design, Including system wiring and residential module details, diode protection for modules, saf~ty and system grounding, and power condi­tioner operating requirements.

For our detailed retrofit designs,'we developed cost estimates for eleven different PV system configurations. These estimates were used to study PV system economics, Including llfecycle costing analyses and the ef­fects of variations In the economic parameters. We used the economic analyses to modify and refine our estimates of national PV retrofit potential for photo­voltaics.

The objectives and major conclusions of the study are contained in the following sections. An Annotated Contents at the end of this Executive Summary volume describes the location of each major topic in the other two volumes of this report.

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3

I. Objectives The following objectives were established by Sandia National Labor­

atories at the outset of this project:

1) To characterize the existing housing stock. In 'terms of the principal aspects affecting residential PV retrofits.

2) To design and specify candidate PV systems for retrofit appli­cations. Including both electrical and hardware design. It is assumed that the systems will be grid-connected and will include no storage.

3) To design retrofit mounting and Installation systems that pro­vide ease and speed of Installation. while minimizing structural alterations and cost. and maximizing adaptability to residential building requirements.

4) To develop estimates of retrofit system costs. as well as to evaluate life-cycle worth and costs of the systems.

5) To prepare estimates of the possible retrofit market size and power production potential •

4 II. CONCLUSIONS

II. Conclusions The following points summarize

of Photovoltaic Residential Retrofits. main body of the report.

General Conclusions

the principal findings of this study Each is developed at length in the

1) There are approximately 60 million residential structures In the U.S. Of these, 35 percent (21 million) are candidates for photo­voltaic retrofits. This means that they are properly oriented, physically compatible, and potentially economic for PV retrofits, assuming DOE 1986 Cost Goals for PV components are met.

2) The national potential for residential PV retrofits is enormous:

• Residential rooftops could accept 81.5 x 106 peak kilo­watts of Installed PV capacity.

• Annual energy production could equal nearly 20 percent of the electricity used for residential purposes in 1980 •.

3) The major present barrier to acceptance .of photovoltaics for resi­dential applications remains the high cost of PV systems. If the DOE 1986 Cost Goals are met, however, the systems will become cost effective (on a lifecycle cost basis) in many regions of the country. With a 20 percent tax credit, they will be cost-effec­tive In all U.S. regions but the northwest, where electric rates are unusually low. The high first cost of the systems will require acceptable financing mechanisms for the homeowner.

4) Cost estimates for a 4 kWp retrofit array indicate a range of $8300 - $11,300 for total installed cost, or from $2.00 - $2.81 per peak watt, in 1980 dollars and assuming the DOE 1986 Cost Goal numbers for module costs.

5) Hounting system ~osts will account for 15 percent to 35 percent of total system cost. The most expensive mounting system design is 130 percent more expensive than the least expensive, however, there Is only a 17 percent difference in final system cost. For a given application, mounting costs have a small effect on the final economics of PV system retrofit and operation.

Specific Conclusions

6) The physical characteristics of the residential housing stock are

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5

favorable for widespread PV system retrofits. Asphalt shingles, plywood sheathing, and rafter spacings of 16" and 24" predomin­ate. Roof pitches on existing houses are also suitable for roof­tops.

Average retrofit roof area can accommodate array sizes ranging from 490 ft2 to 865 ft2 (45.5m2 to 80.4 m2). These roof areas Imply array sizes in the 4-8 kWp range.

The recommended residential photovoltalc module has the follow­Ing characteristics:

• Dimensions roughly 4 feet wide by 6 feet high (roughly 1.2 m x 1.8 m).

• Cells entirely series-wired within the module, to produce an operating voltage of approximately 100 volts, and a power output of approximately 250 Wp.

• Two modules per string; strings are wired In parallel to maximize use of available roof area. Each string pro­duces approxImately 0.5 kWp

• Modules manufactured wIth Internal bypass diode protect­ion and wiring quick-connects.

9) We drew the following conclusions about array mounting systems for rooftops:

• Array mounting systems should not rely on interior, attic accessibility for wiring or structural fastening. All installatIon activities, Including replacement of damaged modules, should be possible from the exterior side of the array.

• Systems which Impose point loads on exIsting framing members (as do many rack mounts) may exceed allowable loadings of existing roof structures.

• It Is possible to fasten the PV mounting system directly to the roof sheathing, rather than to the framing members. This requires mounting designs having numerous, closely spaced fasteners, and the existence of a structurally ade­quate roof sheathing (a condition which can be met on mil­lions of existing buildings).

• Poorly cooled array mounting systems may experience signi-

6 11. CONCLUS IONS

flcant performance degradation due to the higher operat­ing temperatures of the array. Back cooling of the array to minimize these problems Is desirable.

• Aesthetic acceptability of the array can be enhanced by good design of the mounting system, including appro­pri~te color and scale, low profile on the roof, con­cealed fasteners, and an uncluttered appearance.

10) Safety must be planned into the module handling and installation process. Basic measures recommended Include:

• Quick-connects for wiring the modules to wire harnesses. These should prevent finger contact with live conductors.

• Temporary, opaque covers for each module in the array, which are removable after Installation Is completed.

• Disconnect junction boxes located on the exterior of the building.

11) The location of the power conditioner has Implications for build­Ing occupancy. maintenance and safety procedures, and wiring cost. It must be located away from living spaces, due to noise.

12) Present bui ldlng codes have littl,e provision, and present few problems for residential PV retrofits. However, there are pos­sible exceptions to this, and local code enforcement differences may cause problems for retrofits. The National Electric Code does not yet directly provide for PV systems, and may require some modification to deal with them; efforts are presently underway to accomplish this.

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III. CharaderizaHon of ResidenHal Buildings Summary

This section presents data on the characteristics of the existing housing stock in the United States. It provides a starting point, both for estimating the total power production potential of retrofits and for design­ing practical retrofit PV systems. The data came both from published sources and from field surveys. Findings Include:

• Total numbers of residences • Field survey results • Physical characteristics of houses; • Typical house types • Size and number of retroflttable rooftops

Numbers of Buildings

This study limited Its concern to buildings with four housing units or less. The basic data for the numbers of residential buildings was derived from the U.S. Census. Figure 1 shows that, of the grand total of 82.8 million units of housing, 80 percent (66.2 million units) are In buildings having four units or less. This transl~tes into 60 million residential structures, over 90 percent of which are single family dwellings.

The regional breakdown, according to major Census regions, is shown in Table 1. There are regional differences in the composition of the housing stock, which are discussed in Section 1.2.1 of Volume II, but the predomin­ance of the single family dwelling In all regions has the greatest impact on PV retrofits.

Northeast

11.5

Survey Data

Table 1 Number of Residential Structures by Region (millions)

North Central South West

16.1, 21.0 11.1

U.S.

60.0

We used field surveys of three cities to derive regional adjustments to the numbers of potential retrofits. The cities surveyed were Los Angeles, Miami-Ft. Lauderdale, and Hartford-New Haven. Two kinds of field surveys were used. The first was an aerial photogrpah survey performed by the Jet Propulsion Laboratory. In this study, JPL counted and measured the south-facing roof-tops in a random sample of bildings in each of the three cities. This data Is currently the most extensive available for assessing the solar orientation of existing residences.

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Figure 1

Housing Units and Structures U.S. Total

UNITED STATES YR. ROUND HOUSING

HOUSING UNITS 82.S MILLION UNITS

iKl. OF STRUCTURES UP TO II UNITS 60 MILLION. STRUCTURES

4.4%

15.6%

~.6%

7.4%

3.8:

63.2~

MOBILE HOME 3.7 MILLION

5 OR MORE UNITS 12.9 MILLION

3-4 UNITS ~.6 MILLION

'2 UNITS 6.2 MILLION

1 UNIT ATTACHED 3.1 r11LLlON

1 UNIT DETACHED 52.4 MILLION UNITS

--~"'r----87.q% 1 UNIT DETACHED 52.~ MILLION STRUCTURES

--\---:2.2% 3-1, UNITS 1.3 MILLION

~:---:=:::t--s.ll: 2 UNITS 3.1 MILLION

__ ~-S.3% 1 UNIT ATTACHED

SOURCE: ANNUAL BOUSZ.C SURVEY J,7. PARi A u.s. aUREAU 0, r.E CBWSUS

3.1 MILLION

----------------------- TOTAL ENVIRONMENTAL ACTION Inc.

9

The second survey was a '!wIndshield survey" performed by T.E.A. as a follow-up to the JPL study. Project team members visited neighborhoods that had been sampled by the JPL survey, and analysed conditions of roof shading, irregular roof plans, and rooftop obstructions (air conditioners, plumbing vents, chimneys, etc.).

Table 2 summarizes the survey data, and applies it to the Census numbers for existing buildings. Although house types can vary greatly from city to city, we assumed that the survey data for each city was representative for its entire region. We applied data for Hartford-New Haven to both the North­east and North Central regions.

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Table 2 Buildings Suitable for PV RetrofIt

Number of Residen6ial Buildings. x 10

Solar Orientation (JPL)

Number with Solar 6 Orientation x 10

Unobstructed Roofs (T. E.A.)

Number of Potent~al Retrofits x 10

Residential Buildings Suitable for Retrofit

North Northeast Central

11.5 16.1t

69% 69%

7.9 11.3

38% 38%

3.0 1t.3

26% 26%

Data is for residential buildings having

South West

21.0 11.1

78% 71%

16.1t 7.9

69% 52%

11.3 It. 1

51t% 37%

four dwelling units

u.S. Total

60.0

--

----

21.0**

35%

or less Total is less than the sum of the four census region numbers because areas where PV systems would not be economic, have been subtracted out

While the JPL survey covered over two million buildings, it is neverthe­less a small sample when viewed on a national scale, because it is limited to three cities. The T.E.~. sample was a small subset of the JPL sample, and so is even more limited. Despite these limitations, however, the data provides the best basis available for estimating the total numbers of houses that could be retrof i tted.

10 II I. CHARACTERIZATION OF RESIDENTIAL BUILDINGS

House Types

As part of our survey of residences in the three cities, we selected typical house types. The selection process was aided by local officials knowledgeable about prevailing housing styles. The representative buildings we selected are shown in Figures 2, 3 and 4. From studying these buildings several observations can be made:

• The diversIty In house design is great. There Is not a small number of prevailing roof shapes; exceptions and irregularities abound.

• Large, simple roof areas are more of an exception than a rule.

• Any retrofit PV array mounting system that can accommodate many different roof conditions will have an advantage over mounting designs that rely on a fixed set of roof conditions.

• There is an obvious similarity between the Miami-Ft. Lauderdale and Los Angeles house types. The northern house types differ considerably from the southern types.

Roof Area

We estimated the average size of available rooftop area using a number of sources, including theJPL and T.E.A. surveys, and data from the National Association of Homebuilders. We applied these numbers to our earlier estimates of building numbers to arrive at an estimate of total useable roof area for retrofits. Average rooftop areas are largest in the West and small­est in the Northeast; this perhaps is due to the larger number of single story residences in the West. Table 3 shows the average roof areas for retrofit

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Table 3 Usable Roof Area for Retrofit

Number of Potent~al Retrofits x 10

Mean Solar Roof Area per House ft2 (m2) x 106

Total Usable Roof Area ft2 (m2) x 106

Northeast

3.0

390 (36.2)

1170 (108.7)

North Central

4.3

450 (41.8)

1935 (179.8)

South West

11.3 4.1

410 685 (38.1) (63.6)

4633 2808 (430.4) (260.9)

U.S. Total

21.0*

--

9470* (879.8)

Totals are less than the sum of the four census region numbers because areas where PV systems would not be economic, have been subtracted out.

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Bungalow

Figure 2 REPRESENTATIVE RESIDENCES

MIAMI - FT. LAUDERDALE

Flat Clay Tile Ranch

Split-Roof Condominium

0 0 ill III Barrel Tile Ranch

0 n 1\ rn m -:;;;;

Two-Family Block House

Contemporary Suburban

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'--------------------TOTAL ENVIRONMENTAL ACTION Inc.

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Figure 3 REPRESENTATIVE RESIDENCES

HARTFORD - NEW HAVEN

Suburban Garrison

Suburban Cape

New Townhouse Condominiums

19th Century Masonry Townhouse

Victorian Two-Family Wood-Frame House

~-------------------TOTAL ENVIRONMENTAL ACTION Inc.

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Figure 4 REPRESENTATIVE RESIDENCES

LOS ANGELES

Shake-Roofed Suburban Ranch Two Story Contemporary

Post-War Tract House Gravel-Roofed Suburban Ranch

Spanish Revival Stucco Bungalow Suburban Ranch

New Townhouse Units

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'--------------------- TOTAL ENVIRONMENTAL ACTION Inc.

14 III. CHARACTERIZATION OF RESIDENTIAL BUILDINGS

Physical Characteristics

Data on the physical characteristics of the existing housing stock gives an indication of the construction conditions that retrofit PV systems must be able to accommodate. They were derived from several sources. including survey data taken by the National Association of Homebuilders. Major findings include:

• Roofing - Asphalt shingles and roll roofing account for 80% of the roofing material used on residences. The major exception occurs in the Pacific region. where wood shingles and shakes account for about half of the roofing. Asphalt roofing represents the easiest material to retrofit •

• Roof Pitch - 95% of residential roofs have pitches In the 4/12 to 7/12 (lSO - 300 ) range. This Is the easiest range of roof pitches to retrofit. Flat and shallow pitches (less than 7/12) are more difficult to weather seal, and may require rack mounting systems to achieve proper tilt for the array. It Is more difficult and expensive for workers to deal with roof pitches steeper than 7/12.

• Age of Housing -.Older housing, built before t9~O, and common in the Northeast and North Central regions, may be difficult to retrofit. This is due to possible deterioration of roof structure and sheath­Ing, and to the use of out-of-date construction techniques. Never­theless, nearly 60% of the buildings in those regions were built after 1940, which means they are similar to buildings built today in terms of roof pitch, framing modules and sheathing material. They will likely be suitable for retrofit by normal methods. In the West and South, the housing stock is considerably newer, with over half of the houses built since 1960.

• Spacing ~ The 16" and 24" on center rafter spacing Is extremely com­mon; estimates Indicate over 90% of existing houses were built using these standard spacings. This Is Important for mounting systems that must be attached directly to framing methods; for sheathing attached systems, It Is less significant.

• Value - Recent figures for the value of owner occupied housing show a concentration toward the lower end of the value scale. In 1978. the median value for houses was $41,000. In terms of distribution. 50% of all houses fell Into the $20,000 to $50,000 range. PV system costs, assuming cost goals can be met, are estimated to be in the $8,000 to $12,000 range for modestly sized arrays. This means that a PV system retrofit will be a major investment for most homeowners second only, perhaps, to the purchase of their home.

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15

IV. National Power Production Potential

Summary

Given the potential numbers of retrofits and their size, it is pos­sible to project a crude estimate of total power production potential. The estimate was refined by dividing the country Into regions, calculating poten­tial power production of a PV system in that climate, and applying regional electricity cost numbers to determine economic feasibility. The resulting figures for power production potential provIde an upper bound for PV retro­fit residential electricity output, If all feasible retrofits were performed. Major topics In this section include:

• Solar Regions • Peak power and energy production potential • Uneconomic regions for retrofit

Regions

In the previous discussions of physical characteristics, it was convenient to discuss the four major regions of the country, as defined by the Census. In evaluating photovoltaic system power output, and later for calculating the worth of that electricity, it is more reasonable to use re­gions corresponding to climate differences. These are greater in number, and so give a clearer picture of the effects of climate and varying utility rates than the four Census region divisions allow. For this purpose, the Solar Economic Regions, as defined In an earlier Sandia study done by West­inghouse*, were selected. Each has a representative city, and the weather data for each city was used to predict PV system output. The Solar Economic Regions, and their representative cities, are shown In Figure 5.

* P.F. Pittman et aI, Regional Conceptual Design and Analysis Studies for Residential Photovoltalc Systems, Westinghouse R&D Center for Sandia National Laboratories, SAND 78-7040-2, May, 1980.

16

Figure 5

Solar Economic Regions

eNorth Central

REGION

Lower NE-NVC Great Lakes Atlantic Bay Mid-South Southern Central North Central Southwest Pacific Northwest Cal ifornia

• Central

REPRESENTATIVE CITY

Boston. HA Madison. WI Washington. DC Nashville. TN Lake Charles. LA Omaha. NE Great Falls. MT Phoenix. AZ Seattle. WA Santa Maria. CA

-----------------------TOTAL ENVIRONMENTAL ACTION Inc.

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Power Output

Peak power for retrofit arrays was estimated from_a simple assump­tion of 8.61 peak Watts per square foot of array (92.6 Wp/m2). In practice, this number will vary depending on the module used and the area efficiency of the mounting system.

Annual energy production was estimated by the PV-FCHART computer simulation, which was developed at the University of Wisconsin**. The annual energy production varies with the ambient temperatures and available sunshine found in the different regions.

Table 4 summarizes the potential power output of retrofit PV systems on residences in each of the regions. The column showing kWh/year per Wp was derived In the same way as the data Tn Tables 2 and 3. except that the numbers were adjusted to correspond to the Solar Economic Regions.

The two regions identified as uneconomic for PV retrofits are the Pacific Northwest and the North Central regions. Lifecycle cost analyses. described In Chapter VII on system costing and economic analyses. show that PV systems are not economical in these regions. due to very low electric rates. The national totals in Tables 2 and 3 were adjusted to account for this conclusion.

In Table 4. the Economically Feasible Subtotals represent the maximum peak power and total annual energy production that could be achieved from residential PV retrofits. If all feasible installations were performed.

** Seigel. Michael D •• Sim llfied Desl n Methods for Photovoltaic S stems, Masters Thesis, University of Wisconsin, Madison, WI, 19 0

18 IV. NATIONAL POWER PRODUCTION POTENTIAL

Table 4 Power Production Potential

From Residential Photovoltiac Retrofits

# of Usable PV kWh/yr Buildiggs Roof Area per Wp

x10 ft2 (m2) x106

US TOTAL 22.7 10.550 (980.1)

Economically Feasible

Lower NE-NYC 1.64 640 (59.46) 1.30*

Cal ifornla 2.32 1,610 (149.5]) 1.90

Southwest .47 330 (30.66) 2.08

Central 1. 31 570 (52.95) 1.56*

Great Lakes 4.42 1.900 (176.51) 1.41*

Southern 6.82 2,780 (258.26) 1.49

Atlantic Bay 1.45 590 (54.18) 1.41

Mid South 2.58 1,050 (97.55) 1.44

SUBTOTAL 21.0 9,470 (879.8)

Uneconomic

North Central 1.04 620 (57.6) 1.56*

Pacific .66 460 (42. ]) 1.34 Northwest

SUBTOTAL 1.7 1,080 (100.3)

"'Takes into account snow cover and ground reflectance

kW Total Peag x10

MWh/6r x10

90.8 139.7

5.5 7.2

13.9 6.3

2.8 5.9

4.9 7.7

16.4 23.1

23.9 35_.7

5.1 7.2

9.0 13.0

81.5 126.1

5.3 8.3

4.0 5.3

9.3 13.6

Caveats

The accuracy of these numbers is limited by the accuracy of the original numbers (discussed in the previous chapter), by the assumptions made in our calculations, and by the assumption that PV module costs will

19

be reduced to the level of DOE's 1986 Cost Goal. Nevertheless, the numbers present a reasonable estimate of the maximum PV system output attainable by retrofitting existing houses. The actual numbers will be further Influenced by the degree of consumer acceptance, the availability of investment capital. and the success of the PV industry In developing and marketing acceptable products.

20

21

V. Array Architectural Design SUlTVTlary

With our understanding of the physical characteristics of U.S. housing, we designed array mounting systems for residential rooftops. The costs, practicality and reliability of array mounting systems will be Import­ant factors In achieving widespread retrofits. The detailed designs enabled us to make cost estimates for the retrofit PV systems. These estimates were used as inputs to the economic analysis. Several key aspects of array archi­tectural design are discussed:

• Concerns of the residential building industry

• Problems of building codes

• Effects of tilt and orientation on performance

• Recommended residential module size and design

• Recommended mounting system designs

The Residential Building Industry

Fundamental differences between residential photovoltalc systems and most other kinds of PV systems are created by the nature of the residential building Industry. This industry Includes consumers, builders. building code offic:ials, bankers, material suppliers, and specialty subcontractors. Success­ful retrofit designs for PV systems must accommodate the needs and attitudes of each of these participants.

Consumers. builders and their bankers are likely to be most concerned about the economics of the PV system and Its high Initial cost. They are also concerned about the value of the house and about how that value Is Impacted by the PV system attached to It. The appearance of the array, the convenience of operation and maintenance of the system. and it's reliability over many years are all important. Designing these features into residential PV systems is a major concern.

Building code officials will want standardized, tested and certified systems that do not require special expertise to inspect or make safe. Material suppliers will want either complete. packaged systems, or a small number of standardized parts and components. These suppliers will likely carry PV systems as only one of several product lines, and so may resist carrying equipment requiring special expertise to market.

22 V. ARRAY ARCHITECTURAL DESIGN

The installers of residential PV systems, especially for retrofits, are likely to be small, specialty contractors who can provide the hardware and associated installation services. There are many analogous specialty tradesmen already operating in the residential construction market, such as installers of air conditionIng, swimming pools, and security systems. A PV system installer will likely want a single module and basic system that can be adapted to most retrofit situations. Such a system will simplify servi­cing, replacement. and stocking of parts and hardware. The systems must be so simple that relatively unsophisticated installers can Install. trouble­shoot and warranty the entire package. If the retrofit market becomes well­established, there will be thousands of small businesses operating Installa­tion services. Residential PV system designs and distribution should accom­modate this kind of market.

Building Codes

Presently, widely adapted model building codes* for small residences have no direct provision for retrofit PV systems. The most relavent sections, and therefore the sections that may be applied to PV retrofits by local code officials, are those dealing with fire and structure.

Fire provisions are least restrictive for single family residences. except in special risk fire districts, where fire prevention standards are set higher. In these special cases. the fire resistance of roofing materials is specified by the code. This may exclude the use of modules fabricated with flammable plastic materials. The code would treat any modules installed as part of the roof surface (Direct and Integral mounts) as roofing materials sub­Ject to the same fire resistance standards as shingles, tiles or other roofing materials. If PV modules are constructed with plastic materials. the strict­est code Interpretation under these provisions would limit the roof area coverage by modules to 25 percent to 30 percent of the total roof area. For the great majority of residences, however. these code provisions are not likely to apply.

* Model Building Code References:

The BOCA Basic Building Code/1981, Building Officials & Code Administrators International, Inc •• Homewood, Illinois 60430, 8th Edition.

Uniform Building Code, 1979 Edition, International Conference of Building Officials, Whittier, California 90601

Standard Building Code, 1979 Edition w/1980 revisions, Southern Building Code Congress International, Inc~, Birmingham, Alabama 35213

23

For PV arrays that are mounted above the roof surface (Stand-off and Rack mounts), the code provisions dealIng with roof structures would apply. Under some conditions, the retrofit of such a PV array could invoke code requirements for higher fire resistance for the building structure. In a residence, this could mean Improving fire resistance ratings for floor and roof assemblies to one-hour ratings, which would be prohibitively ex­pensive. In most cases, however, these code provisions will likewise not apply.

Structural loading provisions of the codes are not likely to be a problem for retrofits of Direct and Integral mountIng systems, since the array would replace roofing materials of comparable weight. Other kinds of array mounting systems, however, add extra weight and point loads to the roof. Most roofs In good condition have a margin of strength that will ac­commodate the extra load. It will be necessary, however, for the system installer to verify that the roof structure was adequately built in each case, and also that it has not deteriorated below an acceptable level of structural integrity. If the roof fails soon after a PV retrofit, the In­staller will likely be held accountable. Building code officials will have to be satisfied beforehand that the roof structure can safely accept any additional loads Imposed by the PV array.

For a more complete description of building code restrictions, refer to Section 2.1.1 of Volume II or to the building code documents.

Tilt and Orientation

While array tilt and orientation have an Impact on the seasonal output of a PV array, the orientation of the building, and the tilt of the roof are beyond the control of the Installer, and must be taken as they are. The question, then, Is how great Is the performance penalty for non-optimum tilts or orientations. Our data for the potential numbers of retrofits Included all residences facing within 450 of south. Existing roof pitches are pre­dominantly In the 18 to 300 range. A series of calculations for Madison, Wisconsin, demonstrates the effects of different tilts and orientations on performance.

24 V. ARRAY ARCHITECTURAL DESIGN

The calculations demonstrate that annual electric output of PV arrays is not significantly affected by non-optimal orientations or tilts. Figure 6 shows that, for a given tilt angle, the annual performance penalty Is less than 5 percent for systems oriented 4SO from south. It also shows that, within the range of common roof pitches, the effect of tilt on per­formance likewise, is less than 5 percent.

ao o

FIgure 6 % Maximum Performance (Annual Basis)

Madison, Wisconsin

10 <0 30

00 aziolUth 450 azimuth

40 Collector Tilt An~le (de~rees from horizontal)

50 60

No Snow Cover

It is important to note, however, the effect of snow cover. Roof pitches less than 400 shed snow poorly, and so may be shaded by snow for significant portions of the winter. The reduction in insolation due to snow cover is shown as 20 percent and 40 percent during the winter months; the figure shows that the performance penalty of snow cover can be greater than that for either tilt or orientation. Thus, shallow pitched arrays will pay a penalty in performance In snow regions, possibly necessitating the use of a rack mount to increase the array tilt angle.

Module Size and Design

After considering a number of practical considerations for residen­tial PV retrofit systems, we recommend as desirable a residential module having the following characteristics:

• Dimensions of roughly 4 feet by 6 feet (1.2m x 1.8m).

25

• Cells wired entirely in series to produce maximum voltage. This will be roughly 100 volts per module, depending on cell characteri s tics.

• Glass superstrate construction, with cells laminated to the back side of the glass sheet. An alternative design would be to use a porcelain enameled steel substrate.

Arguments leading to this recommendation are described in detail in Sections 2.1.4 and 2.1.5 of the main report. The principal points of this arguement are summarized below:

• Retrofit systems must accommodate a wide variety of roof shapes and area sizes; therefore, it Is desirable that the area of the minimum building block, or string, of the array be as small as practical to minimize wasted roof area. See Figure 7.

Figure 7

Adaptation to Roof Shape: Minimize Wasted Area

• Utility Interactive residential power conditioners will require dc input voltages of approximately 200 volts (see Volume II, Section 4.2.1). Because of the desire to minimize string area, cells in the module should be wired in series to achieve the maximum voltage in the minimum area. With some basic assump­tions of cell size and voltage, this leads to 200 volt strings having roughly 50 ft2 (4.6m2) in area.

26 V. ARRAY ARCHITECTURAL DESIGN

• The slope length of residential roofs generally falls into the 13 feet to 17 feet range, due to the standard widths of resi­dential buildings. The horizontal dimension of the roof, how­ever, is variable. See Figure 8.

Figure 8

Roof Area Generally Available for PV's

• In order to minimize edge length and Intermodule wiring costs, modules should be as large as poss! ble within each string. More­over, the long dfmensions of the module should run vertically up the roof. This minimizes the number of horizontal joints in the array surface, which are more difficult to make watertight. It also gives greater flexibility In adapting to the available horizontal roof dimensions.

• Since the vertical dimension of the array Is relatively fixed, it is desirable to associate this vertical dimension with the array voltage (also fixed), and to maximize use of available hori­zontal dimension by placing strings side-by-side on the roof, and wiring them together In parallel (current is variable). See Figure 9.

Figure 9 Possible String Orientations

Desirable Possible Awkward

27

• A 50 ft2 module would be too big and heavy for workers to handle; two modules of approximately 25 ft2 would be more practical. This Is within the range of glass sizes commonly handled by two-person crews In building construction. See Figure 10.

Figure 10

Module Handling

• For reasons of compatibility with existing construction, a module approximately 4 feet by 6 feet (1.2m x 1.8m) is practical. An alternative size would be 3 feet by 8 feet (0.9m x 2.4m), although this would only be useful for roofs with a slope dimension greater than 16 feet, and thus not as widely applicable as the 4 feet by 6 feet module size. See Figure 11.

Figure 11

String Geometry and Size (two modules)

28 V. ARRAY ARCHITECTURAL DESIGN

• Modules used with roof mounting systems that attach to roof framing members must be compatible with 16 Inch and 24 inch rafter spacings. The 4 foot module width can do this. Array mounting systems having numerous, closely spaced fasteners may be attached directly to structurally sound roof sheathing, rather than to framing members. Module dimensions in such systems are not constrained to match conventional framing modules.

Mounting System Design

We do not recommend any single approach to mounting arrays on exist­ing roofs. There Is suffielent variety in roof type that no single design would serve in all cases. We have developed eleven mounting system designs, covering a wide range of retrofit situations.

Four are Stand-off type mounts; the array is supported above the roof surface and parallel to it. The waterproof membrane is not provided by the array, but remains a function of the existing roof surface.

Four designs are Direet type mounts; the array Is Installed over the structural roof sheathing, but replaces the water shedding function of the roof. This means that the Joints between module edges must be watertight. Two of our Direct mount designs, however, are a variation which we haved named the Modified-Direct mount. This type is similar to the true Direct mount, in that the array surface Is the primary barrier against water pene­tration; however, because It Is a retrofit and the existing roofing material Is left Intact, there Is a second line of defense against leakage. This means that the Modified-Direct mounts ean tolerate a small amount of leakage at the Joints between PVmodules. In general, this means the Modified-Direct mounts can be less expensive and/or more weather-resistant than the Direct mounts.

Two of the designs are Rack mounts, whieh are suitable for flat or very low-piteh roofs. The final design Is an Integral mounti the modules in the array replace both the surface material and the structural sheathing of the roof. The Integral type mount wIll not, In general, be favored for re­trofits, because both roofIng and sheathing must be removed. For buildings' where the sheathing is badly deteriorated, however, the Integral mount is a more attractive option than replaeing the sheathing so that one of the other mounts may be applied.

As a result of our evaluation of the requirements for compatibility with existing roofs that must be satisfied by successful retrofit mounting designs, we evolved the following objectives:

29

• No Interior access to the roof should be required to install the array or its wiring; this kind of access is not possible in build­ings having finished attics or very cramped attic spaces.

• When structural fastening of the array must be made directly to the framing members, there must be sufficient fitting tolerance to accommodate non-uniformities In the framing. In addition, structural loads must be adequately transferred to the existing framing so as not to exceed allowable forces In the timbers.

• Whenever possible, the array fastening should distribute the loads widely over the existing structure. It Is possible to attach the array directly to the sheathing, Instead of the rafters, if there are numerous, closely spaced fasteners. This approach Is simpler and gives greater flexibility In locating the array on the roof.

• Designs should minimize disruption of the weather protection function of the roof during Installation of the array. The re­qulr.ement for temporary waterproofing of the building during installation should be avoided.

• Designs should permit preserving the existing roofing materia1. This helps to meet the previous criterion, and reduces labor cost because the roofing need not be removed.

• Designs should be aesthetically compatible with residential con­struction. Generally, this means a low profile on the roof, blending Into the roof surface. Framing lines should be clean and continuous; fasteners, flashing and wiring should be conceal­ed and/or unobtrusive. Colors should blend with the dark colors of the PV modules.

Not all of our designs meet all of these criteria, although the better ones come close. In Chapter 5 of the main report, each of the designs is evaluated in detail, and compared to the others.

Of the eleven designs reported, we have chosen three as "recommended" designs. They are designs that succeed In several Important ways. They are simple and straightforward: they use reliable, time-tested materials; they are durable and weather-tight: they present a neat appearance on the roof.

Each of the three recommended designs Is presented briefly on the following pages. In the main report, they are fully described, with detailed drawings, cartoons showing the construction sequence, full specifications, and detailed cost estimates of time and materials to Install.

30 V. ARRAY ARCHITECTURAL DESIGN

FRAMED PANEL

The Framed Panel mounting system (Figure 12) Is a stand-off design that is largely shop fabricated. Each panel consists of a perimeter frame that has sufficient structural rigidity to resist the required live loads. The frames are held above the existing shingle surface by short legs at each corner. Roof Jacks are lag screwed to the roof framing members at four foot integrals, and these Jacks fasten the corners of each panel to the roof. The wiring harness Is strung under the panels. Unlike most stand-off designs, repairs to the shingles can be made by simply removing the panels. This is easily done because of the minimum number of attachments. and the structural Integrity of the individual framed panels. This design was also chosen as most suitable for existing modules, because several small modules can be com­bined in a single frame, and attached to the roof as a unit.

__ ---------------------------------------31 Figure 12

Framed Panel

FRAMED PANEL 1. ROOF JACK

2. FRAMED PV PANEL

TOTAL ENVIRONMENTAL ACTION Inc.

32 v. ARRAY ARCHITECTURAL DESIGN

METAL PANEL

The Metal Panel design can be either a Direct or a Modified-Direct mounting system, depending on whether or not the existing roofing Is removed before installation. The Metal Panel module is based on traditional roofing systems that utilize standing seam tray panels and battens. Numerous small metal clips are screwed to the roof sheathing; these, in turn, fasten the metal pans and their batten covers to the roof surface. The PV cells are mounted on a porcelain-enamel substrate, which forms the standing seam panel. The panels overlap at the horizontal Joints, and are capped with a contin­uous metal batten at the vertical joints. Built-in pigtail quick-connects and the wiring harnesses run vertically between the panels, under the battens. A ridge cap waterproofs the top of the array and provides a conduit for the wiring harness to run across the roof.

----------------------------------------------Figure 13-

Metal Panel

METAL PANEL 1. BATTEN CLIP

2. PV PANEL

3. BATTEN

4.SEAi..ANT

5.CONT.CLOSURE

8. RIDGE CAP

7. WIRING HARNESS

33

----------------------------TOTAL ENVIRONMENTAL ACTION Inc

34 V. ARRAY ARCHITECTURAL DESIGN

VERTI CAL GASKET

The Vertical Gasket mounting system (Figure 14) is a Modified­Direct design which relies on the existing roofing as a back-up waterproof­Ing system; some water Is expected to leak through the top surface of the array. Unframed, glass superstrate modules are fastened to the roof along their vertical edges by a neoprene zipper lock gasket, which Is screwed through wooden battens to the roof sheathing. A sealant tape beneath the batten seals the screw penetrations. Horizontal Joints between the panels are made water-resistant by a light-gauge plastic "h" extrusion which clips to the top of the lower panel and extends into the gasket at either end. Wiring runs vertically In the space between the bottom of the module and the shingles and horizontally through a ridge cap assembly.

In addition to the descriptive drawing, we include a series of "cartoons," showing the construction sequence. Each design described In the report Includes construction sequence cartoons such as these. They are useful in describing how the design works, and in developing installation cost estimates.

No Rack mounting systems were chosen for the Recommended Designs, because they are suitable only for flat roofs, which represent a small fraction of existing residential buildings.

~ ___________________________________________ 35

Figure t4

Vertical Gasket

VERTICAL GASKET 1. GLAZING TAPE

2. BLOCKING

3. NEOPRENE GASKET

4. LOCKING STRIP

S. H-CLIP

8. PV PANEL

7. CAP SUPPORTS

8. CAP FLASHING

9. WIRING

---------------------------- TOTAL ENVIRONMENTAL ACTION Inc.

36

Figure 15 a,b Vertical Gasket: Step One and Two

Step One:

In shop, fasten "h"-clips to tops of half of the PV

panels. Pre-assemble horIzontal wiring harness with quick-con~ect5 at

• four feet on center. Attach gaskets to treated wood members and. cut to length. Attach metal angles at one end of each batten.

Step Two:

Layout vertical chalk lines to locate vertical battens and

horizontal lines to outline array.

----------------------TOTAL ENVIRONMENTAL ACTION Inc.

Figure 15 c,d Vertical Gasket: Step Three and Four

Step Three:

Peel paper from glazing tape on underside of ,"Ood battens. Fasten bat tens to roof sheathing. Fasten cap supports across ridge at corner of each bay. Layout wi r i"9 l'Iarnes~.

Step Four.

Loospn ~da~ ~hinQI~~. in"rall .,tt'P fJ""hin~ a~d renail .,hin~le5.

Uo;e rccrillQ tar if rPQuired. Lock IO\"ler panel and fla.ning into ~ide casket witl, locking .,(rip and olace ~hortin9 pluQ" in qui ck-connect .

37

........ ---------------------- TOTAL ENVIRONMENTAL ACTION Inc.

38

Step Five:

Figure 15 e Vertical Gasket: Step Five

Place bottom edge of upper panel over "h""'clip. Quick-connect uppe- r and lower panel. toqether. Lock upper panel into Qa,ket.

----------------------- TOTAL ENVIRONMENTAL ACTION Inc.

Step Seven:

Figure 15 f,g

Vertical Gasket: Step Six and Seven

Stt'p Six:

Quick-connt'ct uppt'r panel. tn wirinq harne"",. Layout glazing lape acro" lOP edqe of lop panel •• InHa11 \creeninq along cap ~up­ports and -~ecure with angl~ flashing. Fa.ten vent cap and set in tar at back 'iide pf ridqe.

Run cable to parallelinq junction box On ,ide of Qui Id in9·

39

~---------------------- TOTAL ENVIRONMENTAL ACTION Inc.

40

Step Eight:

Figure 15 h

Vertical Gasket: Step Eight

Peel off paper face of collector array .

..... ----------------------TOTAL ENVIRONMENTAL ACTION Inc.

41

VI. System Eledrical Design

Summary

The configuration of residential photovoltaic arrays has Implica­tions for the electrical design and wiring details of the system. The elec­trical design is also Influenced by the characteristics of residential power conditioners and the utility company's requirements for grid-connected PV systems. Several key aspects of system electrical design are discussed.

• System wiring • Residential module details • Diode protection for modules • Safety and system grounding • Power conditioner operating requirements

Retrofit System Wiring

The recommended system design consists of a number of strings, which are wired together in parallel to make up the array. Each string con­sists of two panels, approximately 41 x 6' In dimension, mounted one above the other on the roof. As many of these strings as possible are accommodated within the existing roof area.

Internally. each module consists of cells wired In series to achieve a dc output voltage of approximately 100 volts per module, or 200 volts per string. A single. two-conductor cable runs from each string to a paralleling junction box mounted near one edge of the array. Figure 16 presents a schematic of the recommended system wiring.

The paralleling junction box should be located In an easily acces­sible and identifiable place. and should be equipped with an external dis­connect switch. The paralleling junction box approach Is preferred over using a bus bar, mainly because It simplifies testing and maintenance procedures. The disconnect switch is Important, as it can prevent power from being carried In the cable which runs from the junction box to the power conditioning equip­ment during an emergency. such as a building fire.

The preferred array cable for the strings is standard. 14 gauge, two-conductor non-metallic sheathed cable. Because it is produced in large quantities for the construction industry, It Is the least expensive and most widely available cable. For exposed locations, Type UF cable is recommended, because It can withstand ultra-violet exposure and environmental extremes.

quick­connects

VI. SYSTEM ELECTRICAL DESIGN

Figure 16

Schematic of Recommended System Wiring

----- etc.

junction box_

_____ etc.

...,. ......

shorting plug s -.,;..--

to power

conditioner

string #1 string #2 string #3

Interconnections between modules, and to the wiring harness should be accomplished with quick-connects. These may be either molded Into the modules or attached to the ends of pigtail leads. The Ideal connector does not presently exist; It would be a hybrid of presently available connectors having the following characteristics:

• Adaptable to standard-non-metallic sheathed two-conductor cable without need of special tools

• Waterproof and approved for exposed location

• Be designed so that metal contacts cannot be easily reached by a finger.

The current National Electric Code (NEC) does not address the special requirements of photovoltalc systems. Some of the recommended features of PV retrofit systems.mentioned previously may not be acceptable under interpre­tations of the present code. Work Is presently underway to write new sections of the NEC which would cover PV systems and the recommendations for system wiring included here.

Module Design

The recommended, series-wired module. does not have any low-level

43

parallel wiring between cells. The primary reason for this series-wired ap­proach is that it results In the greatest voltage output per unit roof area. In other words, It minimizes the roof area required by one string, thus en­hancing the flexibility of the array design in adapting to a variety of roof shapes and sizes. This series-wlred approach also simplifies the entire wiring scheme, and makes troubleshooting of the array relatively simple. How­ever, it makes good diode protection Imperative, to prevent hot spot failures of modules and propagating faults within the array. A well-designed module should have mUltiple Interconnects on cells, combined with bypass (parallel) diode protection for every 5 percent to 10 percent of a series circuit. This makes total current loss In the string less likely, and results In only a 5 percent to to percent voltage drop across a string in the event that one cell in a string becomes opencirculted. The bypass diodes are essential to good module design, and since their specific design depends only upon the cell/ module characteristics, they are built directly into the module during manu­facture. On the other hand, series (blocking) diodes mayor may not be re­quired depending upon the individual cell/module design (how much power any given cell can dissipate), and the likllhood of the array being partilally shaded by an object or obstruction. Arrays which are not shaded and have cells which can sufficiently absorb power, will not receive series diodes.

Metering

The arrangement, complexity and costs of power metering to determine utility buyback have significance for system economics. To avoid excessive costs of metering, attention should be focused on very simple schemes, such as a single, non-ratcheted meter with an extended rate schedule for negative readings. In more elaborate schemes, the equipment and administrative costs of metering can cancel the dollar savings of small PV systems.

Safety

Shock protection from high dc voltages must be provided at all times, from manufacturing, through Installation, to maintenance procedures. Well designed connectors will do much to minimize danger to personnel while handling and installing modules in the array. It may also be desirable to provide opaque, removable covers from modules to guard against shock hazard while Installing modules. Installation and maintenance procedures must be developed to minimize the possibility of exposure to dangerous dc voltages at every phase of operation, Including emergency situations.

Current NEC requirements do not address PV systems, and application of the existing code is unclear. We suggest that NEe requirements should dictate grounding of all metallic components of an array, unless they are separated from live conductors by a double Insulation system. Double in­sulation may be provided by Insulating layers within the module itself.

VI. SYSTEM ELECTRICAL DESIGN

While double insulation is the most likely approach, non-metallic mounting systems (e.g. neoprene or EPDM rubber) may also be attractive. In addition, de circuits can be configured to provide a ground reference and ground fault detectors can be used in the system.

Power Conditioning Equipment

Sizing of the power conditioner is determined by the maximum power expected on the dc side. This condition would occur under a combination of the coldest daytime temperature and the highest Insolation. Such a situation would further aggravate component electrical stresses If the system were shut down and then turned on suddenly.

Line commutated Inverters are not capable of limiting array current when the open circuit voltage exceeds the maximum operating point voltage of the power bridge. Therefore, they should be sized at least 30 percent larger than nomInal array current. ThIs should not result in significant cost or efficiency penalties with the power conditioner. because unit costs increase slowly with increasing unit size. and because standby losses are small for this type of power conditioner.

Self-commutated power conditioners on the other hand, should not be oversized. They are capable of self-limiting current. and both cost and standby losses would be signifIcant for oversized units.

The provision of a "max power tracker," an electronic circuit in the power conditioner which controls array operation for maximum power output, is not recommended. because of its high cost. Instead, a simple switch for summer/winter operation Is recommended. This will adjust array operation to the different seasonal operating conditions, and will maintain power output very close to the maximum.

On the ac side of the power conditioner, the requirements of the utility must be met. These include an acceptable waveform. minimum power factor allowable. and safety features that will Isolate the array whenever the utility feeder Is depowered. In addition. it is possible that an isola­tion transformer may be required to prevent the injection of dc power Into the grid In the event of power conditioner failure. The most serious ques­tions to be resolved concerning power quality standards have to do with lIne commutated Inverters and their power factor, and the related cost of it's correction. Waveform quality (harmonic content) does not appear to be as serious a problem. because of the relatively low impedance of the ac distribution network and the projected size of typical retrofit PV systems. The unanswered question of overall utility distribution system stability and control under local blackout conditions can be fInally resolved only by a large. expensive experiment with a cluster of PV homes.

The power conditioner presents special problems to the building designer. They can be big; the largest units weigh several hundred pounds, and measure nearly 2'x2'x4'. Access must be possible from three sides, and the unit must be protected from the weather. In addition, since the units make considerable noise, they must be acoustically isolated from the living spaces. The unit should have reasonable proximity to the building's elec­trical service entrance and circuit panel, and It should not be a great distance from the array. For these reasons, an Ideal location would be an attached garage or shed. (See Figure 17.) Possibly the most flexible loca­tion would be as a free-standing unit outside the house, having its own enclosure. (See Figure 18.) This Is a similar concept to the presently com­mon practice of locating air conditioning equipment outside the building. The unit would have to be designed with a suitably weather-tight enclosure that Is visually compatible wIth the residential archItecture.

A comparison of currently available, residential size power condi­tioners, along with their estimated 1986 costs, Is found in Table 5.

46 VI. SYSTEM ELECTRICAL DESIGII

Q) 01 IV ... IV ~

c: -... QJ .... ... Q)

> c:

,.... ..... X

QJ ~ ... ::I c: 01 0

'"- .... u c: ::I ..., 01

.~ c: - 1&1 Q) -~ C!» IV U C ... Z I: IV :) Q.. C ..,

C!» C!» Z Z - .-... I: ... III ... ... ... I: C 1&1 I: > C Z L -

....... --------------------- TOTAL ENVIRONMENTAL ACTION Inc.

Figure 18

Inverter Enclosure/Paralleling Junction Box

.PARALLELING JUNCTION BOX

INVERTER ENCLOSURE

47

''-------------------rOTAL ENVIRONMENTAL ACTION Inc.

.l:-00

Table 5

Sma)) Power CondItIoners, UtIlIty InteractIve

COST COST MFG. KW RATING (KW) l x W x H (In.) WEIGHT (Ibs) TODAY 1286* Abacus 6 48 x 36 x 72 450 $ 4,000* $ 2,000 (controlled ferroresonant) 10 72 x 36 x 72 700 6,000* 6,000

Abacus 6 24 x 24 x 48 390 10.210 4.600 (trans Istorl zed) 10 26 x 30 x 72 520 14,300 5.720

GeminI 4 30 x 10 x 18 100 3.100 1.000 1<

8 36 x 10 x 20 150 3.500 1.500 tn American Power 2 12 x 10 x 24 100 4,000 2.000 -< tn Conversion -f ,.., 4 12 x 10 x 36 150 5,000 2.500 :x ,.., r-,.., ("') Hellonetlcs 2 24 x 2" x 36 150 5.400 2,700 -f ;0

("') 4 24 x 2" x 52 200 7.000 3,500 ;to r-*Estlmated 0 ,.., Vl

C'> z:

49

VII. System Costing and Economic Analysis

Summary

The mounting system designs we developed were used to prepare de­tailed cost estimates of retrofit systems. Using our conclusions about system costs. we analyzed PV system economics In the different regions of the U.S. These results were used to modify the total potential PV power product­ion. described in Chapter IV. Major findings of the costing and economic-; analysis Include:

• Cost estimating assumptions and results • Life-cycle cost analysis and conclusions • Parametric analysis of economic factors • Barriers and Incentives to widespread PV retrofits.

Costing

Installed cost of a 4 kWp retrofit system will range from $8300 to $11.300. These costs are based on complete cost estimates, which T.E.A. de­veloped for each mounting system design. They Include: the costs of PV mod­ules; mounting labor and hardware; manufacturer's mark-ups; and the balance­of-systems costs. which Included the power condItioner. wiring. metering, safety devices, etc. An 8kWp system would fall In a price range roughly twice that of the 4 kWp system.

All costs are In 1980 dollars. The PV module costs are based on the 1986 DOE Costs Goals of $0.70}wp ($0.91/Wp including manufacturer's mark-up). The power conditioner costs are based on the project staff's best estimate of 1986 costs, assuming that the power conditioners are mass-produced. All other costs are based on published prices for labor and materials for 1980. Final estimated system costs are shown in Table 6.

Several important conclusions can be drawn from these numbers:

• Total system costs. except for the most expensive mounting system designs. fall In the $2.00 - $2.50/Wp range.

• Hountlng system costs, Ignoring the least and most expensive de­signs, fall In the $0.34 - $0.63/Wp range. This Is 16% - 26% of total system cost.

• Within the Stand-off and Direct categories, the variations in system cost between mounting systems are 15% or less.

• Haterlals costs, which are dominated by the costs of the PV modules and power conditioner, are much larger than labor costs. Total system cost Is therefore relatIvely insensitive to anything but the PV module and power conditioner.

Table 6

Projected Total System Costs

Total System Cost Mounting Costs**

Days* Cost Cost Cost Cost % of to Total per per per per System

Mounting System Install Labor Materials Cost Wp ft2 Wp ft2 Cost

Standoff Batten Stand-off 2 $514 $7754 $8268 $2.00 $17.30 $.22 $1.91 II Framed Panel 2 641 7699 8340 2.17 17.97 .34 2.84 16 Thrust Plate 2+ 809 8368 9177 2.27 18.06 .47 3.80 21 Flat Cable 2 723 8784 9507 2.30 18.71 .53 4.31 23

Direct Metal Panel 4 935 8655 9590 2.32 18.06 .47 3.67 20 Vertical Gasket 2 736 8713 9449 2.36 21.14 .55 5.00 24 Structural Sealant 4 961 8746 9607 2.40 20.35 .63 5.36 26 Gasket Direct 5 1171 8508 9680 2.41 21.51 .62 5.56 26

Rack ---WOOd Truss 5 1238 8241 9479 2.36 20.88 .59 5.25 25

Pipe Truss 5 921 9998 11259 2.81 23.63 1.01 8.50 36

Integral Gasket Integral 7 1496 8647 10145 2.53 22.54 .74 6.60 29

-~ ------ -----

* two person crew ** total projected system costs minus total balance-of-system costs and module costs

I

\11 o

<:

en -< en -f I'TI :x n o en -f ;z: Cl

~ ;z: o ..., n o ;z:

~ n ~

S; r­-< en en

51

Life-Cycle Cost Ratio

We used a life-cycle cost analysis, which accounts for the time and value of money, to evaluate the economic feasibility of residential PV retro­fits. The analysis determined the cost of purchasing and maintaining a PV system over its lifetime, (assumed to be 20 years) including the earnings from selling excess power to the utility. In addition, a life-cycle cost analysis was done for the cost to purchase an equivalent amount of electri­city from the utility, without a PV system. The two options require differ­ent expenditures by the homeowner at different times, and the life-cycle cost analysis accounts for these differences. The iife-cycle cost with the PV system Is divided by the life-cycle cost without the system, to obtain the Life-Cycle Cost Ratio (LCCR). If the LCCR is less than 1, the PV system would cost less over its lifetime than the cost to purchase an equivalent amount of electricity. The converse Is also true: if the ratio Is greater than 1, the PV system would cost more and would not be a good Investment.

This life-cycle costs analysis was done for the ten Solar Economic Regions to represent the variety of weather conditions, house electric loads and utility rates which are found across the country. Table 7 shows the electric rates; the house electric loads; the amounts of electricity pro­duced, used and sold in the various regions; and the LCCR which will result under these conditions for a 4 kWp system costing $9,000. We found that In four of the ten regions the system has an LCCR of less than 1, even with no tax credit. The effect of tax credits is discussed In the next section.

Parametrics. Several parametrIc studies were performed to determine the sensitivity of the LCCR measure of economic feasibility to key variables. A 4 kWp system and a buyback ratio, for utility-fed power, of unity were assumed, as were typical house electric loads, weather characteristics and electricity costs for each region. The parameters which were examined in­clude: Effect of tax credits, effect of system cost, and effect of electric costs.

Tax Credits. Table 8 shows the tax credits which would be required in each region to make a 4 kWp system cost effective at various system costs. In all but two of the Solar Economic Regions, any of these systems will be cost effective with the present 40% tax credit. The two regions with an un­favorable economic climate for PV systems are in the northwest, where low electric rates overwhelm the savings produced by the PV system.

System Cost. The life-cycle cost ratio Is primarily Influenced by system first cost. It Is, however, an important conclusion of this study, that If the DOE cost goals for system components can be met, and rea-sonable mounting hardware, Installation, and balance-of-system costs are added, PV systems will be cost effective in most areas of the u.S. Figure 19 shows the effect of varying the system cost for a 4 kWp system for the the Solar Economic Regions.

52 VI I. SYSTEM COSTING AND ECONOMIC ANALYSIS

Table 7 Life-Cycle Cost Ratio's for $9,000 System

Typical Power Power Hous:e Distributed Distributed

Solar Fuel Cost Load To House To Utility LCCR Economic Region ($/kWh) (kWh/yr) (kWh/yr) (kWh/yr)

Pacific Northwest 0.03 15800 3650 1530 1.54 Cal ifornla 0.07 9130 3750 3650 0.84 North Central 0.035 7300 2570 3460 1. 79 Southwest 0.075 18300 6660 1410 0.86 Central 0.07 9130 3230 2820 0.98 Southern 0.068 12200 3920 1840 1.03 Great Lakes 0.072 7300 2500 2990 1.03 Mid South 0.061 12200 3730 1850 1. 10 Lower NE-NYC 0.101 4850 1780 3240 0.81 Atlantic Bay 0.067 12200 3650 1810 1.06

Tabl e 8 Tax Credits Required to Make PV Systems Cost Effective

Region % of Initial System Cost Required to make LCeR =

$8400 $9000 $10,000

Lower N.E.'"NYC 0 0 0 California 0 0 0 Southwest 0 0 0 Central 0 0 g Great Lakes 0 4 14 Southern 0 6 15 At I ant i c Bay 5 12 20 Hid-South 12 18 27 North Central 47 51 56 Pacific Northwest 62 65 68

,

53 ,-------------------------------------------------~

Figure 19

Effect o~System Cost on Life-Cycle Cost Ratio

1.6r--------r-------.r-----~~--------~------_,

1.4~-------+~~~~~--------4_------~~--~~~

UNFAVORA LE

t RATIO

FAVOR LE , O.L~~~ __ ~~ ______ ~~ ______ ~~ ______ ~ ________ ~

$4,000 6,000 8,000 10,000 12,000 14,000

Initial System Cost (1981 $)

RATIO. Li fe-Cycle Cost w/PV life-Cycle Cost w/o PV

---------------------- TOTAL ENVIRONMENTAL ACTION Inc.

54 VII. SYSTEM COSTING AND ECONOMIC ANALYSIS

Electrical Costs. Figure 20 shows that the PV system becomes un­economical once purchased power costs drop below the $0.06 - $O.08/kWh range. Above this range, the systems are economic In all regIons. Table 9 presents a more detailed picture of this phenomenon Tn each of the ten regions.

Table 9

Effect of Electric Costs on the LCCR of a $9,000 System

LCCR for. Electric Cost at which LCCR - 1

($/kWh)

Current Electric Cost

($/kWh) Current Cost

Southwest California North Central Central Southern Mid-South AtlantIc Bay Great Lakes Pacific Northwest Lower N.E.-NYC

0.052 0.06 0.068 0.068 0.072 0.072 0.072 0.076 0.080 0.082

0.075 0:070 0.035 0.070 0.068 0.061 0.067 0.072 0.030 0.101

0.86 0.84 1. 78 0.98 1.02 1.10 1.06 1.04 1.54 0.80

BarrIers and Incentives. Factors which influence the decision of a homeowner to Install a solar retrofit or conservation device were examined for their applicability to the Installation of a photovoltaic system. The eight barrIers to the Installation of energy conservation measures, reported by DOE In a report prepared by Hlttman Associates, are shown in Table 10. The most signifIcant barrIer was found to be the first cost of the system. It Is assumed that this will hold tnue for PV systems as well, partIcularly because of the high inItial cost of these systems ($8,000 - $12,000 If Cost Goals are met). Although the Investment may be attractive over the 20 year lIfe-cycle, it may be dIfficult, economically and psychologically for the homeowner to overcome the high initIal cost. ThIs means that attractive financing terms must be available, and investments Incentives like the present 40% tax credit should be continued. Other incentives should be considered and pursued by government and utilities to overcome these barriers.

'.

Figure 20

2.5 Effect of Fuel Cost on Life-Cycle Cost Ratio

2.0

RAT I t RANGE FOR 10 SOLAR ECONOMIC REGIONS

UNFAVORABLE

----------------- ------------------- ... --- .. -t

~ ,. r m Z S 0.5 t3 z l:

FAVORABLE

RA~'O • l!'e-Cycle to., w/p, Life-Cycle Cost w/o PV

m /

z > r ,. o· ::! a o

~----

FUEL COST ($/Kwh)

0.02 0.04 0.06 0.08 0.14 0.16 0.10 0.12

VI VI

S6 VII. SYSTEM COSTING AND ECONOMIC ANALYSIS

Table 10 Barriers to Energy Conservation Retrofi ts

Ranking Barrier

1 First cost of measure

2 Lack of precise or'customlzed information

3 Lack of sociological!psycological incentives

4 Low Fuel prices

S Lack of del ivery systems

6 Inability to evaluate contractor performance

7 Inability to evaluate retrofit products

8 High finance costs

Source: Analysis of Institutional Mechanisms Affecting Residential and Commercial Building Retrofit. Hittman Associates for DOE Office of Conserva­tion Policy DOE!PE!70044-TI

,

57

VIII. Conclusions and Recommendations for Further Study

Our findings Indicate that large numbers of residential photovoltalc retrofits could be economically accomplished. This is contingent upon several key circumstances becoming reality:

• Costs for modules and power conditioners drop to the level of the DOE 1986 Cost Goals.

• Development of sImple. reliable. inexpensive balance-of-system hardware and hardware for rooftop mounting of arrays.

• Resolution of terms and conditions for utility interface. Includ­Ing power quality. buyback metering and pricing. and other re­quirements for utility acceptance of widespread retrofits.

• Perception of the buying public and the financial community that systems are reliable and cost-effective, and will remain so for the life of the system.

Work is already underway to resolve many of the technical problems that must be solved to meet these conditions. There are some questions specific to residential PV retrofits that should be addressed, however:

• There are no established criteria for the performance of the mounting hardware on rooftops. Mounting systems should be torture-tested and the results published to guide designers of mounting hardware. Systems should be tested for resistance to structural loads. watertightness under extreme conditions, effectiveness of back-cooling details, and ease of installation and maintenance.

• The details of metering and utility buyback must presently be ex­amined on a utility-by-utility basis to determine cost-effective­ness. A detailed comparison of factors should be made for numerous localities so that buyers. sellers. policy makers and utilities can easIly understand the conditions necessary for widespread PV retrofits.

• The estimates of rooftop availability in this study were based on limited data. More extensive and detailed surveys, using both aerial photos and ground observations, should be made. A more comprehensive comparison of rooftop availability between regions, and more accurate estimates of actual numbers and sizes of solar rooftops could then be made available.

59

IX. Annotated Contents

This augments the Table of Contents, by pointing out the basic in­formation contained in each section of the report. Many of the sections constitute short papers on specific topics relating to residential PV system design, and may be of interest independently of their contribution to the major conclusions of the study. Other topics are discussed in more than one section of the report, because they are germain to different aspects of system design.

Volume I I, Main Report

1. Characterization of Residential Building In the United States

1.1 Background to Housing Information Cites sources of basic data, and introduces regionallzations used.

1.2 Specific Housing CHaracteristics Influencing PV Retrofits Cites national data on physical characteristics of the U. S. housing stock.

1.3 Rooftop Availability - Field Surveys Describes the most complete study on rooftop availability performed to date.

1.4 Assumptions and Conclusions Identifies four basic types of building, in terms of characteristics affecting PV retrofits, and relates these to common house types.

1.5 Potential Roof Area Available for PV Retrofit Summarizes data on usable roof area for retrofit

2 • Array Arch i tectura I Des i gn

2.1 Array Retrofit Considerations

2.1.1 General Requirements for Retrofits Describes major concerns of the consumer, the PV system Installer, and the building codes.

2.1.2 Retrofit versus New Construction Describes unique constraints on retrofit applications.

2.1.3 Sensitivity of PV Performance to Array Tilt and Azimuth Demonstrates performance penalties of non-optimal orientations,

2.1.4 Module Material Presents assumptions about module construction.

60 IX. ANNOTATED CONTENTS - VOLUMES II & III

2.1.5 Module Size Presents argument for recommended, large, high voltage residential PV module.

2.2 Generic Approaches to Roof-Mounting Arrays Presents detailed discussion of design considerations for retrofit mounting systems.

2.3 Conclusions and Recommendations for Generic Array Designs Summarizes guidelines used in developing mounting system designs found In Chapter 5.

3. Array Engineering and Electrical Design

3.1 General Requirements Explains design constraints imposed by consideration of performance, reliability, safety and electric codes.

3.2 Design Approaches and Issues

3.2.1 Fundamental Issues of Array Electrical Design Three basic module design approaches are discussed in relation to residential PV system wiring and design.

3.2.2 Reliability and Fault Tolerances Develops rules of thumb for diode protection of array and module.

3.2.3 Grounding and National Electric Code Issues Discusses implications for wiring details.

3.2.4 Connectors and Wiring Discusses currently available hardware, and need for improvements.

3.2.5 Array Operating Temperature Presents hourly bin analysis of expected temperatures, and compares to manufacturers recommended maximum operating temperatures.

3.2.6 Maintenance Procedures Discusses safety procedures for testing, maintaining, and replacing defective modules within the array.

3.3 Recommendations for Generic Array Electrical Design Summarizes recommended array and module design features.

4. Balance-of-System Design

.' 4.1 General Requirements

Discusses residential grid-connected applications

4.2 Design Approaches and Issues Discusses operating characteristics of currently available inverter designs, Including possible Improvements

5. Retrofit Array Designs

5.1 Summary of 11 Array Designs Developed Presents drawing and cost summary for each design.

5.2 Evaluation of Array Designs Compares characteristics of the 11 designs.

5.3 Recommended Array Designs

61

Describes four recommended designs in detail, including specifica­tions, wiring schematic, construction sequence drawings, and shop drawings of details.

6. Other Array Designs

6.1 Array Design for Existing Hardware Describes mounting and wiring of a retrofit array, using a currently available module.

6.2 PV Array Combined with Low Temperature Solar Thermal Systems Discusses possible match between PV and thermal applications

7. PV Economic Analysis

7.1 System First Costs Describes assumptions used in costing system designs, and presents sensitivity analysis of various factors

7.2.1 Life-Cycle Cost Ratio (LCCR) Methodology Gives simple description of the methods used.

7.2.2 Economic Assumptions and Utility Environment Describes economic regions analysed, along with electricity cost and consumption numbers for each.

7.2.3 Determination of Photovoltalc Array Performance Describes prediction method used (PV-FCHART), and gives potential PV output of each region of the country •

62 IX. ANNOTATED CONTENTS - VOLUMES II & II I

7.2.4 Results of Life-Cycle Cost Analysis Gives LCCR for each retrofit array designed.

7.3 Sensitivity Analysis for Economic Parameters Demonstrates effect of such parameters as buyback rate, system cost, cost of electricity, etc., on the worth of the PV system.

7.4 Barriers and Incentives Discusses problems of and sol:utions to consumer acceptance of PV retrofits.

7.S Conclusions Presents potential size of residential PV retrofit market in the U.S.

VOLUME III

APPENDICES * A Housing Units and Number of Structures

B Age of Owner Occupied Housing Units

C Financial Characteristics: Owner Occupied Housing

D Other Housing Characteristics: Basements, FoundatIons, Garages

E Cost Data

F Drawings, Details, and Specifications for 11 Array Designs

G Information on Array Structural Analysis

* A more detailed Table of Contents for the Appendices appears at the beginning of Volume III.

.;

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S. Weinstein 19 W. 44th Street New York, NY 10036

Ekosea Attn: Lee Porter BJtler 573 msslon Street San FrancIsco, CA 94105

Ellerbe "'ssocl ates, Inc. Attn: Jim Ge !fer Manager of ProfessIonal ServIces ElectrIcal DesIgn Department One Appletree Square Bloomington, MN 55420

Ellmore/Tltus/Archltects/lnc. Attn: S ..... Titus, AI ... 736 Chestnut Street Santa Cruz, C'" 95060

EI Paso ElectrIc Corrpany Attn: James Brown P. O. Box 962 EI Paso, 1X 79912

Energy Arch Itects Inc. Attn: Sk I MIl burn 885 Arapahoe Boulder, CO 80302

Energy Associates Attn: Ilia Iter A. Adams, P.E. 5109 Royene, NE AI buquerque, 1+1 87110

Energy COnversion Devices Attn: Mr. lionel Ibbbins 1675 West Maple Road Troy, MI 48084

Energy DesIgn &. Analysis Co. Attn: David Schwartz, AlA 1001 COnnecticut Ave., NW liIlte 632 Wash I ngton, 0::: 20036

Energy DesIgn Associates Attn: Steve tearhoof 114 E. Diamond Street ~tler, PA 16001

Energy Management Consultants, Inc. Att n: 001.131 as S. Stenhouse 1180 S. Bever Iy Dr I ve, Su Ite 315 Los hags I es, CA 90035

Energy Planning &. Investment Corp. Attn: R! chard Larry lied II n AlA 833 North Fourth Avenue Tucson, AZ 85705

Energy Services Organization of The Georgia Power Co. Attn: Edward Hey 7 Solar Circle Shenandoh, GA 30265

Engineers-Architects P.C. Attn: Arno I d Hanson, AlA 1407 24th Avenue South Grand Forks, NO 58201

Engineers-Architects P.C. Attn: Gord Rosey 408 FIrst Avenue BuildIng MInot, NO 58701

EnvIronmental Concern Attn: Druce lleuser, AI A Box 2128 Spokane, WA 92210

Envlronmentef DesIgn AlternatIves Attn: Dou;las G. Fuller 1951 BroOkvlew Drive Kent, OH 44240

EnvIronmental InstItute of MichIgan Attn: Reed flees P.O. Box 618 Ann Arbor, MI 48107

Envl ron me ntll I Research Laboratory Attn: I9len Kessler Tucson Intornatlonal AIrport Tucson, AI 85706

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Envlronomlc DeSign Attn: Dennis N. Young, AlA W. 905 Riverside Spokane, WA 99201

E~, Inc. Attn: Chuck 91erman 1650 W. Alaneda DrIve liIlte 140 Tewpe, AZ 85282

Erwin and Akers Associates Attn: Olarles DelIsio Benedum-Trees Bldg. PIttsburgh, PA 15222

Everett Zelgel Tumpes and Hand Attn: R. J. Mlrtln, AlA 1215 Spruce Street Boulder, CO 80302

Ezra D. Ehrenkrantz &. Associates Attn: WIllIam Meyer 19 Wast 44th Street New York, NY 10036

Fando ~1art In and MIlstead Attn: Hank Wa Iker 608 Tennessee Avenue Charleston, 'IN 25302

FIscher SteIn AssocIates Attn: Hans J. Fischer, AlA Route 51 South carbonda I e, I L 62901

FI sk RI nehert Ke Itch '<leyer Inc. Attn: Harley B. FIsk, AlA 100 Kentucky Exec. Bu I I d I n9 2055 DIxIe HIghway Ft. MItchell, KY 41011

FlorIda Power and LIght Attn: Ibbert Allen P.O. Box 529100 MIamI, FL 33152

Frenk H. WItchey Corbett Associates Box 1009 86 East BroadWey Jackson, WY 83001

Franta, Gregg 12819 W. Ellnorth Place Lekewood, CO 80228

Fred Meyer, AlA 3611 5th Avonue San Diego, CA 92103

Fred W. Forbes & AssocIates, Inc. Archltocts AlA and Englnoers NSPE P.O. Box 443 Xen Ie, OH 45385

.'

GallIher Schoenhardt & Baler Attn: Robert P. Mbrcarsky The Courtyard No. 10 SIlII$bury, CT 06070

Gary Cope I and 31-81 Poplal Avenue Mefl1)h 15, TN 38" I

Gary MarcIniak 6582 N. 90th Milwaukee, WI 53224

GeIger Berger & Associates Attn: Kar I Beltll n, PE 500 FIfth Avenue New York, NY 10036

General ElectrIc Co. Attn: J. Harz Advanced Energy Programs P.O. Box 8661 Ph IIadelph I!I, PA 19101

Gensler Architects, Inc. Attn: James l. Gensler, AI A 819 N. Marshall Street MIlwaukee, WI 53202

George A. Roman & AssocIates, Inc. Attn: George A. Ronan, AlA One Gateway Center Newton, lolA 02158

GeorgIa InstItute of Technology EngIneerIng Exp. StatIon Attn: Joan Wood 225 North Avenue, tM At I anta, SA 30332

GeorgIa InstItute of Technolo9f Attn: Hsnk Jackson, P.E. Technolo9f ApplIcations laboratory O'Keefe Rm. 211 EngIneerIng ExperIment StatIon Atlanta, ~ 30332

GeorgI a Power Conp any Attn: Gary Blrdwel I P.O. Box 4545 Atlanta, SA 30303

Gerken & Upham ArchItects, Inc. Attn: Mr. Carl Gerken P.O. Box 155 Ormond Beach, Fl 32074

GK AssocIates Attn: Draw GIll eth 319 flo I brook Road Bedford, NH 03102

Glass Energy ElectronIcs Attn: Ron WIlson 4463 Wood hmd Park Avenue North Seattle, WA 98103

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Grahm ltlbenthal Box 777 Soap lake, WA 98851

Green les/Reese AssocI ates, ltd. Attn: Frank l. Peese, AI A 6400 Flying Cloud DrIve Sllte 210 Eden Pralre, ~ 55344

Grlmball/Gorrondon~Savoye Attn: MIchael D. CDrtner 2352 Matarle Road lotItar I e, LA 70001

Gunnar, Blrkerts & AssocIates Attn: Charles Eleckensteln 292 Harmon Street BI rml ngha~ 1011 48009

Hahn Jackson lloyd Thresher Arch. & Eng. Attn: TImothy A. Henning, AlA Top Hat Road PrInceton, IN 47670

Hank I ns & Anderson, Inc. Attn: H. C. Yu 1680 Santa Rosa Richmond, VA 23288

Harthorne Hagen Gross AlA & Assoc. Attn: Cliff Gross, AlA 220 MarIna l-\art 1500 Westlake N. Seattle, WA 98109

Harvard UnIversIty Attn: John M!rtl n 204 Pierce Hall Cambridge, MA 02138

Heery Energy Consultants Inc. Attn: MarvIn WIley, P.E. 880 W. Peachtree Street, NW Atlanta, SA 30309

Heery & Heery, ArchItects & EngIneers, Inc. Attn: Mr. RIchard YelvIngton 880 West Peachtree Stroet, NIl Atlanta, SA 30309

Helen McEntIre .,60 S. 1785 w. Heritage Bank Building Sllte 200 Salt lake City, UT 84119

He" onet I cs Att n: liIrry Sue I zl e 17312 Eas~an Street Irvine, CA 92714

Herbert Sands 2013 S. Malborne Ct. Melbourne, Fl 23901

.Hood Miller Associates 0

Attn: lbbble Sue ~od, AlA 2051 leavenworth St. Sen franc I sco, CA 94133

ff.U.D. Aft n: Willi em Freeborne Office of the Assistant Secretary

for Policy Development and F9search floom 8162 IIIosh I ngton, OC 20410

'nteractlve Resources, Inc. Attn: Carl Bouville 117 Park Piece

-1'olnt Richmond, CA 94601

°lowa Stete University (2) Attn: David Block, AlA Attn: laurent Hodges Physics OGpertment 290 College of Design IIIlIes, IA 50011

J. L. Harter Assocletes Attn: James l. Harter, Sr., AlA 41 S. Tenth Street Allentown, PA 18102

.rackson lllbs Attn: Tom Hyde Otter Creek Rolld &r ItIrbor, ME 04609

James Sudler Associates Attn: JOIII o-onewett, AlA 200 Cable Bulldl ng Denver, CO 80202

Jllmes Sud ler, FAIA 1201 18th Street Suite 200 Denver, CO 80202

Jllmes T. Barretta Architect Attn: James T. B3rrette, AlA 1832 Nd 2nd Avenue Boca Reton, Fl 33432

Jllmmel Finn & Associlltes Attn: "'nold Finn 1516 E. Hillcrest Street P.O. Box 8963 Or lando, Fl 32856

Jim Dennison Weter Street E I I.seworth, ME 04605

John D. Swetlsh No. 7 WI I dlO)Od Trill I Bettendorf, IA 52722

John Martin Associlltes Architects Attn: John T. Mlrtln, AlA 506 Heights Blvd. Hooston, 1)( 77007

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John R. Taylor Architect Attn: John R. Taylor, All. 815 Shady Bluff Drive OlarI otte, tC 28211

John Yellott Engineering Association Attn: John Ve Ilott 901 West EI Camlnlto Phoen 1110 AZ 85021

Johnstown Architects, Inc. Attn: Benjamin J. Pollclcchlo, All. GKI Building 777 Goucher Street Johnstown, PA 15905

Jones & Mllyer Attn: Olllr les Mayer 13100 Manchester Road St. lools, Me 63131

Jones & Strange-Boston Ross Building Attn: Donald L. Strllnge-Ebston, AlA, PE Ma I n St reet lit 8th Richmond, VA 23219

Joseph J. Del Clotto, Jr., Architect Attn: Joseph Del C1otto, AlA 20 I Church ROlld lIInsdllle, PI. 19446

JSR Associlltes Att n: Dr. John S. Aluyl 2280 Hanover Street Palo Alto, CA 94306

Kammeraad St roop van der leek Attn: Pllul VIIn der leek 355 Settlers Road lei I lin d, loll 49423

Keith Vaughan Associates Attn: Keith Vaughan 3136 E. Madison Street 50attl II, WI. 98112

Kelbaugh and lee Architects Attn: Douglas Kelbaugh, All. 240 Nassau Princeton, NJ 08540

Kitchen & Associates Attn: Deborah K. Gawthrop Off I ce Manager Ebx 935 Philadelphia, PA 19105

Knoell/Quldort Architects Attn: Hugh Knoell, Jr. AlA 1131 East Highland Phoen 1110 AZ 85014

Korsunsky Krank Erickson Architects Attn: Daryl P. Fortier, All. Director of DeSign 570 G8laxy Building 330 Second Avenue South Minnesota, MN 55401

Kruger Kruger AI ben berg Attn: Kenneth Kruger 2 Central Square Cambridge, MIl 02139

lancaster and lancaster ArchItects Attn: Ear I M. lancaster AlA P.O. Box 10 Aubur n, At 36830

lane & Associates ArchItects Attn: John E. lane, AlA 1318 North B Street P.O. !bx 3929 Fort Smith, AR 72913

laplckl/Smlth Associates Attn: earo I A. Iobore 617 Pllrk Avenue Baltimore, I() 21201

lee R. Connell Arch Itect, Inc. Attn: leeR. Connell, Jr •• AlA 2500 Joseph Street New Orleans, LA 70115

leo A. Daly Attn: kturo Bsntog 1025 Connecticut Ave., NW ~ Ite 712 Washington, DC 20036

leon De lIer 911 22nd street Santa Monica. CA 90403

leonard Wr I nberg, A I A 160 HII lair Circle White Plains, NY 10605

II vi ng Systems Attn: Johathan Hammond Route 1 Box 170 Winters. CA 95616

loftness, Vlvan 6055 Bunker HII I Pittsburgh. PA 15206

londe Parker Michels Consultants Attn: Timothy I. Michels 7438 Forsyth ~Ite 202 St. louiS, Me 63105

long Hoeft Architects Attn: Mr. Gary Long, AlA 1228 Fifteenth Street. Suite 401 Denver. CO 80202

louisiana Institute of Building Sciences Att n: RI chard C. Thevenot 830 North Street Baton Rouge, LA 70802

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lydia Straus-Edwards Arch. DeSigner Attn: lydl a straus-Edwards 331 Main Street South w:>".jbury, CT 06798

!O!. (":'vl d Egan. PE P.(,. Dox 365 Anderson, SC 29621

Manuel Perez 1056 Hunting lodge Drive Miami Springs. Fl 33166

Marce I E. Sammut, Arch, & Struct. Eng. Attn: ""rcel E. Sammut. AlA 30 Anthony Circle Newtonville, MA 02160

Mark Beck Associates Attn: Peter Powell, AlA 762 Fairmount Avenue Tcwson. I() 21204

Marlin H. Andersen Homes Attn: ""rlln Grant, President 8901 lyndale Avenue South Blooml ngton. MN 55420

Martin Marietta Corp. Attn: M. S. I manura P.O. Box 179 Denver. CO 80201

Mass Design Attn: Gordon Tully 138 Mr. Auburn St. Cambridge, lolA 02138

Massachusetts Institute of Technology Attn: Tim Johnson Department ot Arch I tecture Cambridge, MA 02139

Matrix Inc. Mtn: Edward MaZl" I a 400 San Felipe NW Slite 6 P.O. Box 4883 Albuquerque, ~ 87106

Mayh III Homes Corp. Attn: John OdegJard P.O. Box 1778 Gal nesvll Ie, Gt. 30501

Meeleer Architect Attn: loll ke McCleer 2249 FI rst Nat lona I BI dg. Detroit. loll 48226

McKinley Management Att n: Dob ~lcKI n ley RFD 17, Box 742 Hancock, NH 03449

101 Attn: M1 chae I C. ~rchant P.O. Box 7707 stenford, CA 94305

Merrlem, Deasy & Whlsenent, Inc. Attn: Bruce D. Freser, It I It 979 Osos Street 5.J Ite C Sen luIs ObIspo, CA 93401

Met celf end AssocI ates Att n: 5.Jsan Shaw 3222 N Street NW ~sh I ngton, [C 20007

Mleml UnIversIty of OhIo Attn: Fuller t-bore Department of Arch. Oxford, OH 45056

MIchael Albanes 2368 Olerry street Denver, CO 80207

MIller Hanser Westerbeck Be II Arch Itects, Inc. Attn: Jay Johnson Suite 300 Butler Square 100 N 6th street MInneapolIs, MN 55403

Miller Wagner Coenen, Inc. Attn: Fobert M. Miller, AlA 250 N. Green Bay Road P.O. Ebx 396 Neeneh, -WI 54956

MIT Attn: Mike Joroff Rm. 4-209 Csnbrldge, MA 02139

MIT/Energy Leboretory Attn: Or. R. Tabors

N. Wheetley 100m E-38, 5th Floor Cembrldge, 14ft 02139

Mobil Tyeo Soler Energy CorpDretlon Attn: MI chee IF. EIII s 16 Hickory DrIve "'Ithem, MA 02254

Mogavero & Unruh Att n: Davl d J. Ibgavero 811 J Street Secrenento, CA 95814

Moore, Grover & Harper Attn: !bbert L. Harper, AlA MIl I ne St reet CBnterbrook, CT 06049

More, Combs, Burch Arch. & Eng. Attn: Donald H. Ibre, AlA 3911 E. Exposition Avenue Denver, CO 80209

Morton, Wolfberg. Alvarez, Taracldl & AssocIates 9400 S. Oadeland Blvd. Mleml, FL 33156

Motorola, Inc. Al10 Attn: Ebb HlI1Imond P.O. Box 2953 Phoen I lro AZ 85062

Mauney, J. Marshal I, AlA DIvision of Plant Qleretlon 306 Education BuIldIng ~Ielgh, NC 27611

Mueller AssocI ates Att n: J. Ibore 1900 Sulphur SprIng Roed Bsltlmore, I() 21227

Mueller Associates Attn: T. KIng 1900 Sulphur SprIng Road Bsltlmore, I() 21227

Mueller AssocIates Attn: A. Parker 1900 Sulphur SprIng Road Bs It lmore, I() 21227

N.C. Solar Energy Assoc. Attn: Bruce John~on, AlA P.O. Box 12235 Research TrIangle Perk, He 27709

NAHB Research FoundatIon Att n: J. Cr owl ey

Z. S I mmernen R. Johnson

14 MIfflIn PIece Csnbr Idge, 14ft 02138

NAHB Research FoundatIon Attn: R. Johnson

H. Engleton P. Kendo

P.O. Box 1627 RockvIlle, I() 20850

NASA Lewis Research Center Attn: lema I d C. CuI I Ma I I Stop 49-5 21000 Il-ookpark !bad CI eve lend, OH 44135

NatIonal Assocletlon of Home BuIlders Attn: L. FI sher 15th end M St., NW waShIngton, [C 20005

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National Homes Corp. Attn: Steven J. Wilson Director of Research & Technologr P.O. Box 7680 Lafayette, IN 47903

Natura I Power Attn: RI ck Katmnberg Francestown Turnpike New Boston, NI'! 03970

Neils O. Brown Development Corrpany Attn: tells O. Brown, President 368 Sunway Lane

RR " Creve Coeur, f.O 63141

New Mexico SollSr Indus. Dev. Corp. Attn: Leland Alhorn 530 1 Centra I Ave., NE Slite 817 AI buquerque, NM 87108

New Mexl co State Government Construction IndJstrles Division Attn: Richard Lisle Bataa n Memor I a I BI d 90 Santa Fe, NM 87503

New f~exlco State Government Construction Industries Division Elec. Bureau Attn: C. A. Lovette Bataan Memorial BI d90 Santa Fe, N~ 87503

Nixon Brown Brokaw Bowen Attn: Paul G. Flehmer AlA 1800 Commerce St reet Boulder, CO 80301

Northeast Design DistributIon Attn: Davl d Campbe II 727 - 11th Ave. New York, NY 10019

Northeast Solar Energy Center Attn: Drew A. Gillett 470 Altantlc Avenue Boston, MIl 02110

Oceanside Solar Consultants Attn: Ra Iph L. SherloOOd 10 East Ma I n Street Hysnn I s, MA 0260 I

Of f I ce of Franz Peter Scheuernann Attn: Franz P. Scheuerrrann, AlA Park Street P.O. Box 1008 Stowe. VT 05672

Off Ice of Glen H. Mortensen Inc. Attn: Glen H. ~brtenson, AlA Suite 201 1036 W. ~blnhood Dr. Stockton, CA 95207

Orner Mlthun, FAIA 2000 112th Avenue, IltI Belewr, WA 98004

Optical ScIences Group, Inc. Attn: Dieter W. Grabl s 24 TI buron Street San Rafael, CA 94901

Pacific Gas & Etectrlc Corrpany Att n: Stephen L. Hester 3400 Crown Canyon Road San Ramon, CA 94583

PacifIc Power & LIght Corrpany Attn: Bill McTavish Box 720 o.sper, Wf 82602

Parker Croston Associates Attn: M. E. Q-oston, Jr., AlA P.O. Box 1927 3108 W. 6th Street Fort Worth, TX 76101

Perez & Hurtado ArchItects, Inc. Attn: Jess F. Perez 850 E. Chapman Avenue SI Ite A Orange, CA 92666

Perkins & Will Attn: Bill Bobenhausen 445 Haml fton Avenue White Plains. NY 10601

Peter D. Paul. AlA P.O. Box 271 50 Galesl DrIve Wayne, NJ 07470

Peter Dobrovolny, AlA Box 133 Old Snowmass, CO 81654

Peter Van Deesser 634 Garcl a Street Santa Fe, NM 87501

Peterson Construction Corrpany Attn: ~bert Peterson, President 6100 S. 14th Street LIncoln. NE 68512

Pettit & Bullinger Architects Attn: Hell C. Pettit. AlA P.O. Box 2726 1202 East FIrst Wichita. KS 67201

Phi lip West. Donald Bergstrom & Assoc. Attn: Edward J. I-brcyn, AlA 33 East First Streot Hinsdale. IL 60521

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PhIneas Alpers ArchItects, Inc:. !lttn: PhIneas Alpers, AlA 344 Newbu ry St reet Boston, MA 02115

Photowatt Inc:. !Itt n: loll ke Kee II ng Ch lef Engl neer T&"" &, AZ 65262

Potonec Energy Group !lttn: Davl d Johnston 40 I Wythe Street Alexandria, VA 22314

PPG IndustrIes, Inc:. !lttn: I...8rry S. McGee Flat Glass DivIsion One Gateway Cl3nter Pittsburgh, PA 15222

Price and Partners 7301 BIrch Avenue Takoma Park, MD 20012

Price Roth & Muse Architects !lttn: William Price P.O. Box 1014 Trl-Clty AI rport BlountvIlle, TN 37617

Public Service eo""eny of New Mexico !lttn: Frank Burcham Post OffIce Box 2267 AI buquerqu e, />t., 87103

PublIc Service eo""eny of New MexIco !Itt n: Davl d Sumners Post Office Box 2267 Albuquerque, NM 87103

PublIc Service eo""any of New Mexico !lttn: T. M. Lechner E I varedo Square Albuquerque, NM 87158

RA Solar Consultants, Inc:. !lttn: Harry E. Burns, Jr., AlA Park 20 West Blountstown HIghway Tallahassee, FL 32304

Ralph E. Kiene & Associates !lttn: Ralph E. KIene, AlA 1006 Grand Avenue kansas City, MJ 64106

Ralph Jefferson, AlA ArchItect 497 SpringfIeld Avenue Summl t, NJ 07901

Ramon Zambrano & AssocIates !lttn: Dan fbI lend lOIS Battery Street San Franc I sco, CA 94111

Rasmussen Hobbs ArchItects/Planners !lttn: D. L. Hobbs, AlA 19 SaInt Helens The Henry Drum House Tecoma, WA 98402

Reymon d E. Ph III1 ps, Ar ch Itect !lttn: Raymond E. PhillIps, AlA 703 SW McKinley Des ~Ines, IA 50315

Raymond J. Bahm 2513 Kimberley ct. NW AI buquerque, NM 67120

Reed So I ar Heat !lttn: John Kaestner Ro 3 Box 845 t«>rth Routo 50 Easton, MD 21601

Renewable Energy Institute !lttn: Pau I Maycock 1050 17th Street, NW Wash I ngton, IX: 20006

Rensselaer PolytechnIc Institute !Itt n: Wa Iter M. Kroner Troy, NY 12181

Reyn HendrIckson 4460 Grand River Street Novl, loll 46050

RI chard Schwarz/Ne II Weber Attn: Nell ""'ber, AlA 3601 Park Center Boulevard loll nneapo" s, M'l 55416

RIddIck EngineerIng CorporatIon, I);)nsultants Attn: James R. Bailey, P.E. 2310 FIrst tetlonal BuildIng Little Rock. AR 72201

Robb Axton, AlA 4741 Laurel cenyon Blvd. North Hollywood, CA 91607

Robert 01 ncecco Arch Itect !lttn: Ibbert 01 ncecco 326 W. Lawrence Lane Phoen I X, AI 85021

Robert G. Werden & AssocIates, Inc:. !lttn: WI I II am F • Milburn P.O. Box 414 Jenkl ntown, PA 20736

Robert J. Johnson, ArchItects 1220 Santa Barbera St. P.O. Box 2673 Santa Barbera, CA 93101

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'~he Dlnkeloo Associates . Attn: Ms. Curta I n 20 Davl s Street Hilnden. CT 06517

. 'Rogers-«age I & Lenghart, Inc:. Attn: Mr. Pogor Q-osby 1576 Sherman Street

.Denver. CO 80203

Ron Plotras lbrtheast Carry 9Jlldlng '10 Water Street tB II 0I0e I I. ME 04347

ibn Yeo. FAIA Architect, Inc:. Attn: Ron Yeo. FAIA !i00 Jasml ne Avenue .corona Del Mar. CA 92625

Ronald R. Campbell & AssocIates ~n: Jan Kafranlc 2150 NOrth 107th Str~et Seattle, WA 98133

Rotz Engl neers, Inc:. Att n: Thonas Ch I pi Is 2828 North HIgh School Road P.O. Box 24357 IndIanapolIs, IN 46224

Rowe Ho I mes Assoc:. Arch. Inc:. Attn: Dave 1T0nccok 215 S. Adams Street Tallahassee, FL 32301

&sdlron Deck Attn: Bruce Browne I I AlternatIve Energy c/o Browne II Lunber Route 4 Eden burgh. NJ 12134

Salt River Project Attn: S. M. Chalmers Dlr. En gr. Sere Dlstrl but Ion Ma Iys I s P.O. Box 1980 Phoen I X, AI 8500 I

Sam Cravotta One Des Ign Mountel n Fa II RTE WInchester, VA 2260 I

Sargent, Webster. Crenshaw. Folley Attn: Dona I d Skowron 2112 Erl e BI yd. East Syracuse. NY 13224

Schaffer Bonavolonta Arch •• Inc:. Attn: Msrtl n Schaffer 24 West ErIe Street ChIcago, IL 60610

Schlpporelt Inc:. Attn: Davl d Ursche I One American Plaza EVilnstori. IL 6020 I

SEIGroup Attn: DavId Wright AlA 418 Broad Nevada CI ty. CA 95959

Sierra EngIneerIng Attn: Tom Carver 1129 Tudor Street Lod I. CA 95240

Skoler & Lee ArchItects. P.C. Attn: Kermit J. Lee. Jr •• AlA 1004 UniverSity BuIlding SyraaJse, NY 13202

SMALCIXRE Attn: Jim Pest I I 10 McClellan AFB Silcramento, CA 95652

SmIth. Hinchman. and Grylls Attn: Randal E. Swelch 455 West Fort Street DetroIt. loll 48226

SOHIO Research Center Attn: C. E. Thomas 3092 Broadway Ave. Cleveland. OH 44115

Sol Tec Attn: JIm Q-ouch 2160 Clay Street Denver. CO 80211

Solar BuildIng Corp. Att n: Joh n Newman 1004 Allen St. LouIs, Me 63104

Solar Design Associates Attn: steven J. strong Conant Road LIncoln. MA 01773

Solar Environmental EngineerIng Attn: Dave Gunther 2524 East Vine DrIve Fort COllins, CO 80524

Solar Processes Inc:. Attn: Gordon PreIss II Vel vet Lane Mystl <7 CT 06355

Solar Technology Systems Attn: Charles Orr BIA Upper St. Giles St. Norwl ch, . ENGLAND NR2lAB

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SolArc Attn: Inthon Iy QJtr I 2040 Addison Stroot Berkeley, CA 92704

Solerex Corporetlon Att n: f.Brth Boznen lJ)5 Plccard Drive Rockvlll e, Kl 20650

Son PQ/er Conpeny /Itt n: Julien Baker 512 Eest 4th Avenue Olynple, WA 98501

South Street Des Ign Attn: Don Prowler 22)3 Greys Ferry Avenue Phlledelphla, PA 19146

Southern Call forn la Ed I son Conpeny Attn: Nick W. Patapoff P.O. Box BOO Rosemeed, CA 91770

Steelcreft Corporetlon Attn: Gary Ford Box 1240B Menphls, TN 3B112

Sunrise BuIlders Attn: RI ch SchloO Isky P.O. Box 125 Grefton, VT 05146

Sverdrup and Parcel Eng & Arch Attn: Frank Kessler 1650 W. Alemeda Drive Tenpe, lIZ 85282

Talbot & Associates Attn: Thones L. AI nscough, AlA P.O. Box 2224 VirgInia Beach, VA 23452

Tennessee Valley Authority Attn: Henry M. HeCl ley, P.E. Solar Applications Branch 350 Q-edlt Union Bldg. Chattanooga, TN 37401

Texas Tech Un Ivers Ity Att n: Professor Olr I Ch II ders Division of Architecture fbx 4140 lubbock, 1X 79409

Thayer School of Engineering Att n: Peter Vescuso Resource Po II cy Center Oer1lnouth ())llego Ha novo r, NH 03755

The Arch Itects Co Ilaborat I ve Attn: Ms. GClII Flynn 46 Brattle Street Cllllbr Idge, MA 02138

The Architects Taos Attn: Willi am MI ngenbach Box 1884 Taos, N-1 87571

The Architectural Alliance Attn: Peter Pfister, AlA 400 Clifton Avenue M1 nneapo 115, MN 55403

The BDM Conpany Attn: Pete Sowa 1801 RClndolph Rd. SE AI buquerque, N-1 87106

The BDM Conpany Attn: M. G. Semnens 1801 RClndolph Rd. SE AI buquerque, N-1 87106

The Burns/Peters Group Attn: William L. Burns, AlA 8000 Pennsyl van I a C I rc I e NE AI buquerqu e, N-1 87110

The Burr AssOCiates, Architecture & Planning Attn: Doneld F. Burr, FAIA P.O. Box 99885, lekewood Center Tecome, WA 98499

The Clerk Enerson Pertnershlp Attn: Cherles l. Thol!&en 600 NBC Center Llnco I n, . NE 68508

The Orcutt/WlnslQ/ Partnership Attn: Paul Winslow AlA 1109 North Second Street Phoen I X. lIZ. 85004

The Royal Arch. Institute of Canada (RIIIC) Attn: Robbins Elliott 151 Slater Ottawa Olnada KIP .5H3

The Wolf Partnership Architects Attn: wn nam G. Schlneneck., AlA Attn: Paul J. SchmItz, AlA 7 South 7th Street Allentown, PA 18101

ThOMCls Russe II 80 9tleld Street West Hartford, CT 06110

Thomas Vonler Associates Attn: Peter H. Smell I lie Suite 413 2000 P Street, NW Washington, DC 20036

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Thomas W. MerrIll ArchItects Attn: Thoms W. Io9rrlll 321 SW SIxth Albany, OR 97321

Total DesIgn Four Attn: carter Howard P.O. Drawer 3947 Corpus ChrIstI, TX 78404

Toflll En vI ronmanta I Act I on (100) Attn: Peter Telllll e Church HIlI HarrIsvIlle, NH 03450

Trell 15 & WatkIns 6565 Pennacook Court Columbl a, I() 21045

TrlSo I arCorp (25) Attn: Alan MIlner 10 DeAngelo Drive Bedford, MA 01730

Trynor Hermnson & Hahn Architects Attn: Gil bert F. Hahn, AlA 311 Medical Arts Building Ibx 156 St. Cloud, MN 56301

Tucson ElectrIc Power Attn: Jon GJenther P.O. Box 711 Tucson, AZ 85311

UnIversIty of ArIzona Attn: M3r I e Jensen Environmental Research Laboratory Tucson, AZ 85706

UnIversity of Arkansas Attn: James Lambeth, AlA 1591 Clark Fayettevlll e, AR 72701

UnIversIty of North Carolina Attn: Dean Charles HIght College of Architecture UfoCC Stilt I on Charlotte, He 28223

Unl verslty of Puorto RI co Attn: Angel Lopez Ctr for Enorgy & En vI ronmenta I Research College StatIon, P.R. 00708

Unlverslt)' of Southern Cllllfornill Attn: Ra Iph Knowl es School of ArchItecture and FIne Arts Los Angeles, CA 90007

VllnOorRyn Clllthorpe & Partners Att n: Peter ca I thorpe Drawer 7 Inverness. CA 94937

Vonler AssocIates 1927 s. Street, NW Su Ite 300 WBshlngton, DC 20009

Walter S. Withers Architect Attn: W!tlter S. Withers, AlA 1250 Chambers Road Co I umbus, OH 43212

Warehouse SpecIalIst, Inc. Attn: f.\Irk van Deyae I at 655 Brighton Beach Road Io9nash II, WI 54952

Warner Burns Toan Lunde Attn: Fr I tz Lunde 330 W. 42nd Street New York, NY 10036

WED Enterprises Attn: MI ke McCullough 1401 Flowers Street Glenda Ie, CA 9120 I

Wendell H. Lovett Architect Attn: \'bndell H. Lovett, FAIA 2134 ThIrd Avenue Seatt I e, WA 98121

Westinghouse Electric Corporation Attn: p. PIttman P.O. Box 10864 Pittsburg", PA 15236

11'1111 am Drevo Arc" Itect Attn: WIlliam Drevo, AlA 6125 29t" Street, tM WBshI ngton, DC 20015

WIllIam J. Bates Architect Attn: William J. Bates, AlA 57 Marlin Drive West Pittsburgh, PA 15216

WIlli am ~Iorgan Arch Itect Attn: Thomas A. McQ-ary, AlA 220 East Forsyth Street Jacksonvlll e, FL 32202

William Tao & Associates Attn: Richard Janus 2357 59th Street St. Louis. Me 63110

WI III am Thomas Meyer, AlA Attn: 11'1111 am T. Meyer 353 East 72nd Street New York. NY 10021

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Wlndworks Attn: Tom Werking Rt. 3, Box 44A MuklJOnago, WI 53149

Wright, Pierce, Eng, & Arch. Attn: DOUJlas Wilkie 38 Roosevelt Avenue Glen Head, NY 11545

Wrlght-Plerce Associates & Eng, Attn: Earbara Freeman 99 lola I n St reet Topsha~ ME 04086

WSUN Attn: MI chae I Edds 715 Southwest Morrison 8th Floor Portland, OR 97205

ZOEworks Attn: Garth (bIller, All. 70 Zoe Street San francisco, CA 94107

Zomeworks Inc, Attn: Steve Eaer P.O. Box 712 AI buquerque, If.1 87103

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* u.s. GOVEltNMENT PltlNTING O .... ,CE. nU-O-87 .. DZI'.47'