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CALIFORNIA ENERGY COMMISSION A GUIDE TO PHOTOVOLTAIC (PV) SYSTEM DESIGN AND INS

CALIFORNIA ENERGY COMMISSION A GUIDE TO PHOTOVOLTAIC (PV) SYSTEM DESIGN AND INSTALLATION JUNE 2001 500-01-020 CONSULTANT REPORT Gray Davis, Governor PV Installation Guide June 2001 Page 1 A GUIDE TO PHOTOVOLTAIC (PV) SYSTEM DESIGN AND INSTALLATION Prepared for: California Energy Commission Technology Systems 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 PUBLICATION # 500 – 01 – 020 Version 1.0 June 14, 2001 PV Installation Guide June 2001 Page 2 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. DISCLAIMER References in A Guide to Photovoltaic (PV) System Design and Installation to any resources, products, companies, or services are provided as a public service, and are not an endorsement, recommendation, or favoring of same by the California Energy Commission. The State of California and the California Energy Commission and its employees make no warranties, express or implied, and assume no legal liability for the information included in this PV Installation Guide. We apologize for any errors or omissions, and welcome suggestions to consider for future edition of this Guide. PV Installation Guide June 2001 Page 3 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 PV Installation Guide June 2001 Page 4 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). PV Installation Guide June 2001 Page 5 SECTION 2: SYSTEM DESIGN CONSIDERATIONS 2.1 Typical System Designs and Options PV Electrical System Types There are two general types of electrical designs for PV power systems for homes; systems that interact with the utility power grid and have no battery backup capability; and systems that interact and include battery backup as well. 2.1.1. Grid-Interactive Only (No Battery Backup) This type of system only operates when the utility is available. Since utility outages are rare, this system will normally provide the greatest amount of bill savings to the customer per dollar of investment. However, in the event of an outage, the system is designed to shut down until utility power is restored. Typical System Components: PV Array: A PV Array is made up of PV modules, which are environmentally-sealed collections of PV Cells—the devices that convert sunlight to electricity. The most common PV module that is 5-to-25 square feet in size and weighs about 3-4 lbs./ft2. Often sets of four or more smaller modules are framed or attached together by struts in what is called a panel. This panel is typically around 20-35 square feet in area for ease of handling on a roof. This allows some assembly and wiring functions to be done on the ground if called for by the installation instructions. balance of system equipment (BOS): BOS includes mounting systems and wiring systems used to integrate the solar modules into the structural and electrical systems of the home. The wiring systems include disconnects for the dc and ac sides of the inverter, ground-fault protection, and overcurrent protection for the solar modules. Most systems include a combiner board of some kind since most modules require fusing for each module source circuit. Some inverters include this fusing and combining function within the inverter enclosure. dc-ac inverter: This is the device that takes the dc power from the PV array and converts it into standard ac power used by the house appliances. metering: This includes meters to provide indication of system performance. Some meters can indicate home energy usage. other components: utility switch (depending on local utility) 2.1.2. Grid-Interactive With Battery Backup This type of system incorporates energy storage in the form of a battery to keep “critical load” circuits in the uploads/s3/ pv-installation-guide.pdf