"A Guide to Photovoltaic (Pv) System Design and Installation" - California

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CALIFORNIA
ENERGY
COMMISSION
A GUIDE TO PHOTOVOLTAIC (PV)
SYSTEM DESIGN AND INSTALLATION
JUNE 2001
500-01-020
Gray Davis, Governor
CALIFORNIA
ENERGY
COMMISSION
A GUIDE TO PHOTOVOLTAIC (PV)
SYSTEM DESIGN AND INSTALLATION
JUNE 2001
500-01-020
Gray Davis, Governor
PV Installation Guide
A GUIDE TO PHOTOVOLTAIC (PV)
SYSTEM DESIGN AND INSTALLATION
Prepared for:
California Energy Commission
Energy Technology Development Division
1516 Ninth Street
Sacramento, California 95814
Prepared by:
Endecon Engineering
347 Norris Court
San Ramon, California 94583
with
Regional Economic Research, Inc.
1104 Main Street, Suite 630
Vancouver, Washington 98660
Version 1.0
June 14, 2001
Page 1
June 2001
PV Installation Guide
PREFACE
The California Energy Commission is providing this guide as an information resource to those installing
photovoltaic (PV) systems under the Emerging Renewables Buydown Program. This is the first published
draft of this guide and represents the current state-of-the-art in PV system installation. Revisions will be
made to the document as necessary to address suggestions made by users of the guide. If anyone has
suggestions on how to make this guide more useful, please do not hesitate to send those suggestions to the
California Energy Commission. We hope that this guide is a worthwhile addition to the resources available
for installers and look forward to your constructive comments for continued improvements.
Page 2
June 2001
PV Installation Guide
TABLE OF CONTENTS
SECTION 1: INTRODUCTION............................................................................................ 4
1.1. Basic Principles to Follow When Designing a Quality PV System ......................................... 4
1.2. Basic Steps to Follow When Installing a PV System ............................................................... 4
SECTION 2: SYSTEM DESIGN CONSIDERATIONS ........................................................ 5
2.1 Typical System Designs and Options......................................................................................... 5
2.1.1. Grid-Interactive Only (No Battery Backup).......................................................................... 5
2.1.2. Grid-Interactive With Battery Backup.................................................................................. 5
2.2. Mounting Options ........................................................................................................................ 6
2.2.1. Roof mount.......................................................................................................................... 6
2.2.2. Shade Structure .................................................................................................................. 7
2.2.3. Building-Integrated PV Array (BIPV)................................................................................... 7
2.3 Estimating System Output ........................................................................................................... 8
2.3.1. Factors Affecting Output ..................................................................................................... 8
2.3.2. Estimating System Energy Output ...................................................................................... 9
2.4. Installation Labor Effort ............................................................................................................ 10
2.5. Incentives to Reduce Costs ...................................................................................................... 10
2.6. Estimating Electrical Energy Savings ..................................................................................... 10
2.7. Supplier and System Qualifications ........................................................................................ 10
2.7.1. Pre-Engineered Systems .................................................................................................. 10
2.7.2. Warranties ......................................................................................................................... 11
2.7.3. Company Reputation (years in business, previous projects)............................................ 11
2.8. Overall Project Coordination .................................................................................................... 12
2.8.1. Utility Considerations ........................................................................................................ 12
2.8.2. Acceptance of Systems (performance evaluation) ........................................................... 12
2.8.3. System Documentation ..................................................................................................... 12
2.8.4. System Monitoring ............................................................................................................ 12
2.9. References.................................................................................................................................. 13
SECTION 3: SYSTEM INSTALLATION ........................................................................... 14
3.1. General Recommendations ...................................................................................................... 14
3.1.1. Materials recommendations .............................................................................................. 14
3.1.2. Equipment recommendations and installation methods ................................................... 14
3.2. PV System Design And Installation ......................................................................................... 14
3.2.1. Preparation Phase ............................................................................................................ 14
3.2.2. Design Phase.................................................................................................................... 15
3.2.3. Installation Phase.............................................................................................................. 16
3.2.4. Maintenance and Operation Phase .................................................................................. 19
SECTION 4: SOLAR ELECTRIC (PV) SYSTEM INSTALLATION CHECKLIST ............. 20
APPENDIX........................................................................................................................ 25
Page 3
June 2001
PV Installation Guide
SECTION 1: INTRODUCTION
Photovoltaic (PV) power systems convert sunlight directly into electricity. A residential PV power system
enables a homeowner to generate some or all of their daily electrical energy demand on their own roof,
exchanging daytime excess power for future energy needs (i.e. nighttime usage). The house remains
connected to the electric utility at all times, so any power needed above what the solar system can produce
is simply drawn from the utility. PV systems can also include battery backup or uninterruptible power supply
(UPS) capability to operate selected circuits in the residence for hours or days during a utility outage.
The purpose of this document is to provide tools and guidelines for the installer to help ensure that
residential photovoltaic power systems are properly specified and installed, resulting in a system that
operates to its design potential. This document sets out key criteria that describe a quality system, and key
design and installation considerations that should be met to achieve this goal. This document deals with
systems located on residences that are connected to utility power, and does not address the special issues
of homes that are remote from utility power.
In this early stage of marketing solar electric power systems to the residential market, it is advisable for an
installer to work with well established firms that have complete, pre-engineered packaged solutions that
accommodate variations in models, rather than custom designing custom systems. Once a system design
has been chosen, attention to installation detail is critically important. Recent studies have found that 10-20%
of new PV installations have serious installation problems that will result in significantly decreased
performance. In many of these cases, the performance shortfalls could have been eliminated with proper
attention to the details of the installation.
1.1. Basic Principles to Follow When Designing a Quality PV System
1. Select a packaged system that meets the owner's needs. Customer criteria for a system may include
reduction in monthly electricity bill, environmental benefits, desire for backup power, initial budget
constraints, etc. Size and orient the PV array to provide the expected electrical power and energy.
2. Ensure the roof area or other installation site is capable of handling the desired system size.
3. Specify sunlight and weather resistant materials for all outdoor equipment.
4. Locate the array to minimize shading from foliage, vent pipes, and adjacent structures.
5. Design the system in compliance with all applicable building and electrical codes.
6. Design the system with a minimum of electrical losses due to wiring, fuses, switches, and inverters.
7. Properly house and manage the battery system, should batteries be required.
8. Ensure the design meets local utility interconnection requirements.
1.2. Basic Steps to Follow When Installing a PV System
1. Ensure the roof area or other installation site is capable of handling the desired system size.
2. If roof mounted, verify that the roof is capable of handling additional weight of PV system. Augment roof
structure as necessary.
3. Properly seal any roof penetrations with roofing industry approved sealing methods.
4. Install equipment according to manufacturers specifications, using installation requirements and
procedures from the manufacturers' specifications.
5. Properly ground the system parts to reduce the threat of shock hazards and induced surges.
6. Check for proper PV system operation by following the checkout procedures on the PV System
Installation Checklist.
7. Ensure the design meets local utility interconnection requirements
8. Have final inspections completed by the Authority Having Jurisdiction (AHJ) and the utility (if required).
Page 4
June 2001