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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
Photovoltaic Design and Installation For Dummies (9781119544357) was previously published as Photovoltaic Design and Installation For Dummies (9780470598931). While this version features a new Dummies cover and design, the content is the same as the prior release and should not be considered a new or updated product. The fun and easy way to get a grip on photovoltaic design and installation Designing and installing solar panel systems is a trend that continues to grow. With 'green collar' jobs on the rise and homeowners looking for earth-friendly ways to stretch their dollars and lesson their carbon imprint, understanding photovoltaic design and installation is on the rise. Photovoltaic Design & Installation For Dummies gives you a comprehensive overview of the history, physics, design, installation, and operation of home-scale solar-panel systems. You'll also get an introduction to the foundational mathematic and electrical concepts you need to understand and work with photovoltaic systems. * Covers all aspects of home-scale solar-power systems * Viable resource for professionals, students, and technical laymen * Can be used to study for the NABCEP exam Whether you're a building professional looking to expand your business and skills to meet the growing demand for solar power installation or are seeking a career in this rapidly expanding field, Photovoltaic Design & Installation For Dummies has you covered!
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Photovoltaic Design & Installation For Dummies®
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Published simultaneously in Canada
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Library of Congress Control Number: 2019932064
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Photovoltaic Design and Installation For Dummies®
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Table of Contents
Cover
Introduction
About This Book
Conventions Used in This Book
What You’re Not to Read
Foolish Assumptions
How This Book Is Organized
Icons Used in This Book
Where to Go from Here
Part 1: Here Comes the Sun: Shedding Some Light on PV Systems
Chapter 1: The Photovoltaic Revolution
Peeking into the Past, Present, and Future of PV Installations
Introducing PV Components and Systems
Knowing Your Electricity A-B-Cs
Solar Resource 101
Surveying a PV System Site
Delving into PV System Details
Sizing a PV System
Bringing a PV System to Life
Introducing the Sections of Code You Need to Know
Chapter 2: Checking Out Common Components and Systems
Introducing the Components That Make Up PV Systems
Differentiating between PV System Types
Figuring Out the Right System Type for Any Situation
Chapter 3: Powering through Electricity Basics
Going with the Flow: Current
May the (Electromotive) Force Be with You: Voltage
Making a Stop: Resistance
Connecting Current, Voltage, and Resistance with Ohm’s Law
Pondering Power and Energy
Wrapping Together Current, Voltage, Resistance, Power, and Energy
Another Electricity Concept: Circuit Configurations
Chapter 4: Warming Up to the Solar Resource
High (Or Low) Energy: Solar Radiation
Examining the Effects of the Sun’s Path on the Earth
Positioning PV Modules to Make the Most of the Solar Resource
Chapter 5: Properly Selecting a Site for a PV System
Setting the Stage for a Site Survey
Picture This: Documenting Your Entire Site Survey with Digital Photos
Collecting Basic Information during a Site Survey
Measuring Information in Degrees
Exploring Shading-Analysis Tools
Interpreting the Data and Bringing It All Together
Part 2: Digging into Complete System Details
Chapter 6: PV Modules: From Sand to Electricity
Creating Solar Electricity: It All Starts with a Cell
Reviewing Common Types of PV Modules
Pointing Out Electrical Specifications on PV Modules
Surveying Test Conditions for PV Modules
Relating Current and Voltage in IV Curves
Chapter 7: The Basics of Batteries
The Fundamentals of Battery Anatomy and Operation
Comparing Different Types of Batteries
Comprehending Battery Capacity
Specifying Batteries
Chapter 8: Keeping Current and Voltage in Check: Charge Controllers
The Essentials of Charge Controllers
Maximum Power Point Tracking Technology
Pulse-Width Modulation Technology
Specifying a Charge Controller
Chapter 9: Inverters: AC (From) DC
Getting the Goods on Grid-Direct Inverters
Investigating Battery-Based Inverters
Specifying Any Inverter
Chapter 10: Staying Secure: Wiring and Safety Components
Defining the Circuits in a PV System
Checking Out Types of Conductors
Considering Kinds of Conduit
Delving into Disconnects
Perusing Overcurrent Protection Devices
Focusing on Ground Fault Protection
Looking at the Basics of Labels
Part 3: Sizing a PV System
Chapter 11: Sizing a Grid-Direct System
First Things First: Evaluating the Budget and the Available Array Area
Estimating the Site’s Annual Energy Production
Sizing the Array to Meet Your Client’s Energy Consumption
Getting Ready to Match an Inverter to an Array
Matching Power Values for an Array and an Inverter
Coming Up with the Right Voltage Values for Your Array and Inverter
Bringing It All Together: Combining Your Power and Voltage Information
One Last Check: The Inverter’s Maximum Current Input
Chapter 12: Sizing a Battery-Based System
Get Loaded: Looking at Loads in a Battery-Based System
Sizing the Battery Bank
Sizing the PV Array
Sizing the Charge Controller
Sizing the Inverter
Incorporating a Generator
Chapter 13: Sizing Conductors, Conduit, and Safety Components
Conductor Sizing 101
Sizing Conduit
Sizing Overcurrent Protection Devices and Disconnects
Part 4: Installing a PV System
Chapter 14: The Permitting Process
Obtaining Permits before You Install a PV System
Not Just Pretty Pictures: Creating Drawing Sets
Chapter 15: Staying Safe Anytime You Work on a PV System
Getting a Grip on General Construction Site Safety
Looking at Ladder Safety
Raising the Issue of Rooftop Safety
Examining Electrical Safety
Charging Ahead with Battery Safety
Chapter 16: Assembling the Mechanical Parts
Surveying PV Array Mounting Methods
Considering Loading When You Mount an Array on a Roof
Properly Attaching an Array to a Roof
Supporting Ground and Top-of-Pole Mounting
Chapter 17: Integrating the Electrical Elements
Location Is Everything: Knowing Where to Place Electrical Equipment
Working on Wiring
Bonding Yourself to Grounding
Connecting to the Utility
Chapter 18: Commissioning, Inspecting, and Maintaining a PV System
Making a List and Checking It Twice: Preparing for Commissioning
Start ’Er Up: The Commissioning Process
Arming Yourself for Inspection Issues
Surveying System Maintenance
Part 5: The Part of Tens
Chapter 19: Ten Ways to Avoid Common Code Mistakes
Providing Proper Working Clearance
Supplying the Right Structural Support
Keeping Water out of Buildings with Flashing
Ensuring All Conductors Have the Necessary Ratings
Managing the Conductors on Modules
Selecting the Correct Conduit
Locating the Disconnects
Grounding the Equipment
Grounding the System
Labeling the System Properly
Chapter 20: Ten Ways to Maximize Energy Production for Your Clients
Select the Right Site
Orient the Array Correctly
Configure the Array Properly
Work within the Limits of the Utility Voltage
Choose the Correct Inverter
Size Conductors Appropriately
Keep the Components Cool
Advise Clients to Monitor Their System
Clean the Array Periodically
Inspect the Array Annually
Index
About the Author
Connect with Dummies
End User License Agreement
List of Tables
Chapter 15
TABLE 15-1 The Working Heights for Various Ladder Lengths
List of Illustrations
Chapter 2
FIGURE 2-1: A main distribution panel and a subpanel in a residence.
FIGURE 2-2: A typical grid-direct PV system.
FIGURE 2-3: A utility-interactive, battery-based PV system.
Chapter 3
FIGURE 3-1: AC and DC current flow versus time.
FIGURE 3-2: Inline and clamp meters.
FIGURE 3-3: Measuring a PV module’s voltage with a DMM.
FIGURE 3-4: Measuring resistance with a DMM.
FIGURE 3-5: A diagram of the power equation.
FIGURE 3-6: Ohm’s Law and the power equation combined into one.
FIGURE 3-7: Five PV modules wired in series.
FIGURE 3-8: Five PV modules wired in parallel.
FIGURE 3-9: PV modules wired in a series-parallel configuration.
Chapter 4
FIGURE 4-1: Direct radiation and diffuse radiation are the components of solar r...
FIGURE 4-2: Irradiance measured on a cloudless day.
FIGURE 4-3: Irradiance measured on a partially cloudy day.
FIGURE 4-4: An irradiance curve with a box over it can help you calculate irradi...
FIGURE 4-5: An example of NREL peak sun hours data.
FIGURE 4-6: An insolation map of the United States.
FIGURE 4-7: The earth’s movement around the sun.
FIGURE 4-8: How earth’s tilt affects the amount of daylight on the solstices and...
FIGURE 4-9: Altitude and azimuth.
FIGURE 4-10: A sun chart for 30 degrees north latitude.
FIGURE 4-11: The solar window.
FIGURE 4-12: A PV module with an azimuth of about 165 degrees.
Chapter 5
FIGURE 5-1: Compass views showing positive and negative magnetic declination.
FIGURE 5-2: Obstructions as viewed on a sun chart.
FIGURE 5-3: A typical tilt and orientation graph.
Chapter 6
FIGURE 6-1: A solar cell with a PN junction.
FIGURE 6-2: The movement of electrons though the PN junction.
FIGURE 6-3: A monocrystalline cell module (a) and a multicrystalline cell module...
FIGURE 6-4: A typical IV curve for an individual PV module.
FIGURE 6-5: IV curves of the same module at varying temperatures.
FIGURE 6-6: IV curves of the same PV module at varying levels of irradiance.
Chapter 7
FIGURE 7-1: The construction of a typical PV system battery.
FIGURE 7-2: The chemical reaction that occurs when discharging and charging a ba...
FIGURE 7-3: Battery capacity versus discharge rates.
Chapter 8
FIGURE 8-1: Some examples of charge controllers.
FIGURE 8-2: Three-stage charging for a charge controller.
FIGURE 8-3: The power gained through the use of MPPT controllers.
Chapter 9
FIGURE 9-1: Your average grid-direct inverter.
FIGURE 9-2: A typical battery-based inverter.
Chapter 10
FIGURE 10-1: Different circuits in a PV system.
FIGURE 10-2: Conduit used in PV systems.
FIGURE 10-3: A disconnect integrated into an inverter (a) and separate disconnec...
FIGURE 10-4: Sample labels for PV systems.
Chapter 11
FIGURE 11-1: The DC voltage window in an IV curve.
FIGURE 11-2:
NEC
®
Table 690.7.
Chapter 12
FIGURE 12-1: An example of a load-analysis spreadsheet.
FIGURE 12-2: A battery bank’s number of cycles versus its depth of discharge.
Chapter 13
FIGURE 13-1: A portion of
NEC
®
Table 310.16.
FIGURE 13-2: A portion of
NEC
®
Table 310.17.
FIGURE 13-3: A portion of the
NEC
®
“Conductor Properties” table (Chapter 9,...
Chapter 14
FIGURE 14-1: A one-line drawing used to obtain electrical permits.
Chapter 15
FIGURE 15-1: The right way to set up a ladder.
FIGURE 15-2: Essential fall-protection gear for rooftop work.
FIGURE 15-3: A locked and tagged disconnect.
Chapter 16
FIGURE 16-1: Flush-to-roof racking.
FIGURE 16-2: Ground mounting.
FIGURE 16-3: Top-of-pole mounting.
FIGURE 16-4: Different types of flashing.
Chapter 17
FIGURE 17-1: Equipment-grounding options for PV modules.
FIGURE 17-2: System-grounding options for utility-interactive PV systems.
FIGURE 17-3: A typical utility-required disconnect location.
Chapter 18
FIGURE 18-1: A sample system-commissioning form.
Guide
Cover
Table of Contents
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Introduction
Solar electricity is one of the most accessible forms of renewable energy available, and it can be adapted to fit anyone’s specific needs. The source of it, sunlight, allows photovoltaic (PV) modules to produce electricity and perform useful work, such as running electrical loads or putting energy back into the utility grid.
Globally, there has been an incredible increase in demand for solar modules and PV systems since the turn of the 21st century. No longer is PV technology limited to NASA spacecraft and backwoods cabins. Nowadays, PV systems are within reach for many people. This global demand and increased accessibility and affordability have helped transform the PV industry from a small cottage industry into a worldwide megabusiness.
As a renewable energy educator, advocate, and user, my primary goal is to see the solar industry grow successfully and sustainably — two things that require consistent high-level performance from the people “in the trenches” or, more appropriately, “on the roofs.” PV system designers and installers are tasked with providing high-quality systems that can benefit clients for more than 20 years. If you follow the information, advice, and tips I present in this book, you’ll be well on your way to completing this task with the best of them. (Of course, no perfect power source is out there. To be a good PV system designer and installer, you have to realize the limitations of PV systems, which is why I help you consider those limitations in this book, too.)
About This Book
As the PV industry expands and captures the attention of more and more individuals, so does the amount of information about these systems. Photovoltaic Design & Installation For Dummies adds to this ever-expanding mass of information, but it stands out in its ability to provide you with practical, hands-on specifics. My intention with this book is twofold: to give you the ability to jump headfirst into the PV industry and to arm you with the knowledge you need to competently install a system (more or less) on your own. I use my real-world experience and desire to see every roof holding a well-designed and properly installed PV system to help you.
My approach is to give you the information you need in easy-to-understand sections that are relevant to the work you’ll be expected to perform as a PV designer and installer. (I don’t expect you to read this book from cover to cover, but if you do, I’ll take it.)
Note: This book is focused on the applications used to power homes and small businesses — with or without the electrical utility present — but you can take the principles and guidelines I present and adapt them for just about any application you need.
Conventions Used in This Book
Even though the title of this book has the word photovoltaic in it, most folks in the industry don’t throw that word around day in and day out. Instead, we prefer to say PV — it’s simpler, and it creates far fewer tied-up tongues.
Also, throughout this book you’ll see references to PV array and PV system. The former term refers to the collection of PV modules that makes up the PV array, and the latter term refers to the PV array and all the associated components (disconnects, inverters, batteries, and so on) that make it operational and useful.
In addition, all time references throughout this book are based off solar time (which I cover in Chapter 4). Solar noon is the time of day exactly between sunrise and sunset, when the sun is at its highest point in the sky that day. Your longitude, the time of year, and whether you’re subjected to daylight saving time influence the relationship between your clock and solar time.
Last but not least, the following conventions help you more easily sort through all the new ideas I throw at you:
The key words in bulleted lists and the action steps I ask you to follow in a specific order appear in
boldface.
New terms that are important for your understanding of PV systems are in
italics,
as are words I choose to emphasize.
Web addresses appear in
monofont
. (Note that when this book was printed, some Web addresses may have needed to break across two lines of text. There’s no extra punctuation, though, so just type in exactly what you see, pretending as though the line break doesn’t exist.)
What You’re Not to Read
So many interesting side notes about PV technology, politics, and installation techniques exist that I could easily use all the pages of this book for nothing but various tangents. I think I’ve done a good job of sticking to the main points to give you the most important information you need, but some stories and bits of knowledge are just too good to keep to myself. These stories and tidbits are included in the gray-shaded boxes (sidebars) and paragraphs marked with the Technical Stuff icon. Don’t feel bad for skipping over this text if that’s what you choose to do; you aren’t going to miss out on the essential information a PV system designer and installer needs to know.
Foolish Assumptions
Simply by picking this book up, you’ve already proven my first assumption, that you have an interest in finding out more about PV systems, to be true. I also make some other assumptions about you; here they are, for your viewing pleasure:
You’re one of the many individuals ready to make a career move that includes PV design and installation; you’re either already a building-trade professional or you’re enrolled in classes and want to secure an entry-level position in the PV industry.
Perhaps you’re a homeowner looking for a better understanding of PV systems; you’re thinking about having one installed and want to be as knowledgeable as possible when working with a PV system designer and installer.
You’re interested in technically challenging projects, and you can accept that good designs and installations don’t happen overnight. You want to prepare yourself and gain some knowledge first.
How This Book Is Organized
Photovoltaic Design & Installation For Dummies is arranged in five different parts. Each part can stand alone or be read in conjunction with the others. If one of the following parts (or a particular chapter within that part) excites you more than the others, by all means, head there first.
Part 1: Here Comes the Sun: Shedding Some Light on PV Systems
Get ready to discover the fundamentals of PV design and installation in this part. Here, I introduce you to the major components used in the systems you’ll most likely be working with. And in case you need a refresher course on (or an introduction to) the fundamental electrical principles, this part has you covered. It also explains the specific relationship between the sun and the earth and how this relationship affects where you should position a PV installation.
Part 2: Digging into Complete System Details
Everything you ever wanted to know about the major components of PV systems can be found in Part 2. If you’ve been wondering how a PV module works and how the acid inside a battery can make electricity, here’s your chance to find out those things. This part also covers the basic functions of the other major components of PV systems: charge controllers, inverters, and wiring. And because safety should always be your top priority, I also get you acquainted with essential safety devices (think fuses and circuit breakers).
Part 3: Sizing a PV System
In this part, I walk you through the different methods for sizing your PV systems (figuring out how many PV modules you need), whether they’re grid-direct or battery-based, and the necessary wiring and safety devices. Sizing is the area that can make or break your system. If you properly size and specify (select) all the system components, your system will likely pass inspection much faster, and your client will be left with a safe, efficient way of capturing and using solar energy. If, however, you make major errors in your preparation and design, fixing those errors after the system is already installed can be a difficult (and sometimes dangerous) task.
Part 4: Installing a PV System
Part 4 is where I cover the physical installation process, as well as the activities that precede and follow it. I kick things off by walking you through the permitting process so you have the permission you need to install the system. Next, I cover the safety considerations you need to have in mind when you’re out installing systems. (After all, PV construction sites offer a number of hazards for everyone on-site; by preparing for these hazards, you can avoid them altogether.) After that, I break the installation process into the mechanical and electrical portions. Then I give you a process to follow when you’re ready to commission (turn on) the system and get the modules working prior to the mandatory building department inspection. Finally, I address proper PV system maintenance.
Part 5: The Part of Tens
The Part of Tens is designed to give you small chunks of information for a quick and easy read. Prepare to find out some of the common mistakes made in PV installations so you can do your best to avoid them, as well as some quick tips on how to keep the PV systems you design and install working as well as they should.
Icons Used in This Book
Throughout this book, I use the following icons to bring your attention to interesting, important, or even downright critical information.
Although I’d love it if you remembered everything in this book, I know that’s practically impossible. That’s why I mark ideas I want you to keep in mind no matter what with this icon.
Every now and then I tend to “nerd out” on you with interesting but nonessential information. I promise to keep these asides (relatively) short and to warn you that they’re coming with this icon.
This little bull’s-eye brings your attention to information that may make your job a little easier.
Don’t let anyone fool you. PV systems pose real dangers. This icon alerts you to a situation that requires special attention and caution.
Where to Go from Here
Wondering where to start reading? If it were me, I’d jump to Chapter 6; this is where I get into the PV modules themselves — far and away the most interesting part of PV systems (in my humble opinion). If you’d rather choose the approach my children take — which is to decide what you think is best despite my advice — flip to the table of contents. There you can breeze through all the chapters and see what jumps out at you.
After you get what you want out of this book, I strongly suggest you find a way to put that knowledge into action. Numerous organizations that provide hands-on training and experience are available, and these classes are an excellent way to get your hands on some equipment and have access to individuals who are knowledgeable and eager to help you master PV systems. Then, if you have the means, install a PV system on your own home. Doing so lets you run the show and gives you some personal insight into what it takes to install PV systems (plus it provides you with a slightly less stressful situation for your first solo installation because you don’t have a client or supervisor looking over your shoulder).
Wherever you end up going first in this book, realize that you’re jumping into an exciting and rapidly evolving technology and industry. No matter where you go within the pages of Photovoltaic Design & Installation For Dummies, you’ll be well on your way to becoming involved with one of the most dynamic and exciting industries you can imagine.
Part 1
Here Comes the Sun: Shedding Some Light on PV Systems
IN THIS PART …
Understanding the fundamentals of photovoltaic (PV) systems is the key to designing and installing high-quality systems that’ll perform beyond your (and your clients’) expectations. That’s why this part provides the foundation you need to move forward with designing and installing PV systems.
Chapter 1 gives you an understanding of where PV systems started, where they are now, and where they’re headed; Chapter 2 gives you a feel for the major components used in all types of PV systems and how they relate to each other. Chapter 3 provides an overview of the electrical fundamentals that drive system designs and installations, and Chapter 4 outlines the relationship between the sun and the earth and guides you on assessing the solar resource. Rounding out the bunch, Chapter 5 walks you through the process of selecting where on a client’s property to install a PV system; it also helps you quantify the solar resource at a particular location.
Chapter 1
The Photovoltaic Revolution
IN THIS CHAPTER
Taking a look at the PV timeline
Refreshing yourself on the basics of electricity and the solar resource
Selecting a site for a PV system and outlining the different system components
Making the sun work on your client’s behalf with proper system sizing and installation
Getting to know Code
In recent years, photovoltaic (PV) systems have popped up on people’s homes and businesses all over the United States. Believe it or not, this desire to use the sun to power people’s electricity needs is anything but new. Ever since scientists discovered materials that can produce electrical current by simply being exposed to light, people have been excited about this energy source. Get ready to dive into the exciting and ever-expanding world of solar power with the overview I provide in this chapter.
Peeking into the Past, Present, and Future of PV Installations
To truly appreciate PV, it helps to have an understanding of where the technology came from, where it’s at now, and where it’s going.
The operating principles for modern PV cells were first discovered in 1839 by a French physicist named A.E. Becquerel. After that, a number of scientists played with and improved on Becquerel’s original discovery. In the 1950s, Bell Labs created the first piece of PV technology designed for use in space. This technology soon found its way back down to earth for use in telecommunications applications in remote areas. In the 1970s and 1980s, people began using PV modules to charge batteries and then used those batteries to run various lights and appliances in their remote homes. These early PV pioneers helped set the stage for today’s PV industry.
The first PV cells weren’t very efficient or widely used outside of space programs. They were also quite costly. Yet over the years, researchers and manufacturing companies increased efficiencies and reliability and managed to drive down costs drastically. All of these contributions have led to the widespread use of solar modules and their availability to you and me. In the following sections, I describe some common PV applications, a few brief pros and cons of PV systems, and the future of the PV industry.
Acquainting yourself with typical PV applications
Modern PV systems can be found in a wide variety of applications. They power calculators, pump water, help offset the energy used by floodlights along highways, and, of course, power homes and businesses.
For you and me, electricity is available nearly everywhere we go, and PV systems are able to integrate with the existing utility grid. In remote, developing areas, PV systems provide valuable energy for powering lighting systems, running refrigerators, and helping deliver clean drinking water.
Checking out PV pros and cons
PV systems have some serious advantages on their side. Producing electricity from the sun has environmental benefits because the power source is an abundant renewable resource that’s available every day (even though PV systems aren’t as effective during cloudy weather, they still produce a small amount of power on those days). PV is also a highly adaptable power source. You can use individual cells to power small electronics and individual panels to power specific loads. You can build small arrays to power homes, or you can build utility-scale projects to send massive amounts of power into the utility grid. And after PV systems are installed, they can provide many years of clean, reliable power at virtually any location on earth.
On homes and businesses connected to the utility, PV systems are considered distributed generation, a power source that produces electricity close to the location where the power is used. They’re able to offset the requirements on the central power plants sending out the electricity most people use.
PV systems aren’t the right answer for all applications. They have some disadvantages too. For example:
The sun isn’t a continuous power source.
At night, the PV modules can’t produce power, so in some scenarios, you have to use a method to store the energy for later use (adding cost and complexity to the system design and installation).
The amount of area required to produce power is large in comparison to other sources of power.
For large-scale projects, significant portions of land or roof space are necessary. Not every homeowner or business owner has access to such space.
Looking into the future of PV
Most people accept that “alternatives” to the “conventional” power sources acquired by burning fossil fuels must be developed, and so, to use a really bad pun, the solar industry has a bright future ahead of it. The worldwide demand for solar electricity continues to grow on a global level, and the amount of time, effort, and money being put into the industry is amazing. Many research and development projects are underway that will help drive down costs further, increase efficiency, and deliver better PV systems.
I’m reluctant to make any bold predictions about the future of PV technology; ideas I had just a few years ago that I wrote off as too far-fetched and nearly impossible are proving to be real solutions in the PV industry. However, I am comfortable saying that the overall acceptance of PV systems and their integration into the built environment will do nothing but increase in the years to come. Solar power is no silver bullet, though. It’ll take a movement on many fronts to make the global shift away from over-reliance on fossil fuels.
Introducing PV Components and Systems
PV systems can be ridiculously simple (connect a module to a load and use the load as you wish), but they can also seem overwhelming when you first look at them. Every time I go to design and install a PV system, I look at the whole process as a real-life puzzle that must be arranged and put together just so. Each project is unique in its own way, and that’s part of the fun.
Yet despite the differences in the details, the PV systems you connect to homes and small businesses have some specific and very necessary components (all of which have an important role to play in the system).
PV modules:
The individual units that you place in the sun to produce electricity from the sun are called
PV modules.
A number of modules connected together in different configurations form a
PV array.
Battery bank:
Batteries provide a way of storing the energy produced by the PV array. Individual batteries connected together make up a PV system’s
battery bank.
Inverters:
Devices that take power from the PV array or the battery bank and turn it into AC power used to operate loads are
inverters.
Disconnects and overcurrent protection:
These components are necessary for ensuring the safety of the system and the people who come into contact with it.
Grid-direct PV systems, which send power back to the utility grid, have become the most popular type of PV system at locations where the utility grid is present. They offer increased efficiency and reduced maintenance as well as decreased costs compared to their battery-based counterparts. What they give up, though, is the ability to use the PV array whenever the utility power goes out. Luckily for most people who have utility power present, utility outages are relatively rare; when they happen, they’re generally short-lived.
Battery-based systems operate independently from the grid (stand-alone) or as a backup to the grid (utility-interactive).
In Chapter 2, I run through all the major components you need to install in a PV system — whether it’s a grid-direct one or a battery-based one — and what their relationship is to the other pieces of the puzzle. There, I also explain how to determine which type of system is best for any given client.
Knowing Your Electricity A-B-Cs
A good understanding of electrical concepts and fundamental equations is vital to designing and installing PV systems correctly. My goal is to have you feeling comfortable and confident in your understanding of the basic electrical terms and equations (don’t worry — no calculus here). If you design and install PV systems long enough, I guarantee you’ll find yourself using these concepts on a daily basis.
If you’ve never opened an electrical box for fear of the unknown monsters lurking behind the cover, or if you just need a refresher on all the terminology, check out the information I present in Chapter 3. The jargony, industry-specific terms that the PV world is filled with (many of which are born from the electrical trade) will be much clearer if you do.
Solar Resource 101
The solar resource is defined as the amount of solar energy received at a particular site. Following are some of the terms used to describe the intensity of the sunlight striking the earth (these terms are used pretty frequently in PV system design, so I suggest getting familiar with them; for specifics on the relationship between the sun and the earth, see Chapter 4):
Azimuth
describes the position of the sun (and the modules) in terms of how many degrees the sun or the array is from north.
Irradiance
describes how intense the sunlight is at a particular moment in time.
Irradiation
refers to the quantity of solar energy received for a given amount of time (a day is a typical time frame).
Solar window
refers to the portion of the sky where the sun appears at a particular location on earth. The solar window varies based on your latitude. You want to do your best to keep any obstructions out of the PV array’s solar window.
Tilt
describes the number of degrees that the PV modules are off of the horizontal surface.
But that’s not all you need to know about the solar resource. A PV system’s location on the earth has a definite effect on the overall system installation. Also in Chapter 4, I help you look out at the sky and see the big window that must be kept open for your PV system to perform as well as it possibly can; I also describe the specific effects of the sun’s path on the earth.
Surveying a PV System Site
PV systems are wonderful, magical things, but they can’t perform miracles all on their own. You have to give them a fighting chance for them to knock your client’s socks off. In other words, you have to survey the area where the array will be located and make sure nothing will block sunlight’s path to the array.
Shade is your enemy, so take a critical look at the potential PV location when you conduct your site survey. A tiny bit of shade on the array may be unavoidable at certain parts of the year, but it’s your job to predict and limit these scenarios to the best of your ability.
In Chapter 5, I show you what to keep an eye out for and how to properly assess your site’s potential. I also outline the most common tools you should have on hand in order to perform a successful site survey.
Delving into PV System Details
PV systems use a number of interesting components that can leave even the most seasoned electrician gawking in amazement. I walk you through the major components in the sections that follow. My goal is to boost your comfort level with the capabilities, limitations, and basic construction of all the major pieces of a PV system. I strongly encourage you to read these sections (rather than skip over them) so you can acquire some basic understanding; without it, any system you design is just a bunch of parts and boxes that likely won’t get the job done.
PV modules
PV modules are truly where all the magic of PV systems begins. They produce voltage and current, and, when wired correctly, they perform useful work. (To me, that’s more magical than making entire bridges disappear.) In Chapter 6, I show you the module specifications you’ll refer back to many, many times during the system design and installation processes. I also show you how the modules are at the mercy of their surrounding environment and will react to whatever sunlight and temperatures they’re exposed to.
Batteries
When you need to store the energy produced by a PV array and use it at a later time, you need batteries. I list your many options and go over the basic construction and operation of batteries in Chapter 7. (This information will prove invaluable when you start specifying [selecting] batteries for your battery-based PV systems.)
Whenever you need to incorporate batteries in a PV system, you need to define the following parameters:
The amount of energy the client needs daily
The number of days the client wants to be able to go without having to recharge the batteries
The amount of solar energy that’s available for charging the batteries
The temperature at which the batteries are stored
Charge controllers
When you use batteries, you have to make sure they’re properly charged by the PV array — that’s where a charge controller comes in. In Chapter 8, I show you how to evaluate the different charge controller technologies that are used most often and explain how the different technologies interact with the array and batteries to deliver the maximum amount of energy to the batteries. I also outline the different feature sets commonly found on charge controllers and introduce the specifications to consider when selecting a charge controller for a battery-based PV system.
Inverters
Because PV arrays and battery banks produce and store DC electricity, you almost always need to include an inverter in a PV system (or more than one, depending on the size of the array). An inverter takes DC electricity and turn it into the AC power used by most electrical loads in homes and businesses.
I go over the inverter categories used in PV systems in Chapter 9, but in general, you can classify inverters as either grid-direct or battery-based:
All grid-direct inverters are also classified as utility-interactive (meaning they can take power from the PV array and send it into the grid).
Battery-based inverters, on the other hand, can be classified as utility-interactive or stand-alone (meaning they can’t send power into the grid and are meant for off-grid applications).
Wiring and safety devices
Safety is one of the most important considerations you make during the design and installation process. To achieve proper equipment safety, you need to install a number of safety devices, not least of which is the right wiring. In Chapter 10, I introduce you to the different types of conductors (wires), the conduit that protects those conductors from damage, and the overcurrent protection devices you have to use to protect the conductors from having too much current flowing through them.
Another important piece of safety equipment is the disconnect switch that allows you to (no surprise here) disconnect the PV array from the inverter. When a disconnect switch is in the off position, you can safely access the components of a PV system for servicing.
Because other people (such as emergency personnel) may come into contact with the system, you need to make sure it’s safe for them by installing labels that explain how to quickly and safely access the system.
As a final note on safety precautions, you need to keep in mind that at some point the wiring in the PV system may become damaged and pose a risk. Ground fault protection (GFP) devices help protect against fire hazards in the case of damaged conductors. In grid-direct inverters, this protection is preinstalled; for battery-based systems, you must install GFP separately.
Sizing a PV System
In order to have a PV system operate properly and meet your client’s expectations, you need to spend some time in the design phase evaluating the individual components of the system and their interaction with all the other pieces. During this sizing process (which is when you determine the number of modules to use in a particular system), you have to consider the client’s available budget for the project, the PV array location, and the specifications for the individual pieces of equipment.
In this section, I explain the basics of sizing and installing the two main system types and talk about sizing the safety equipment used in your systems.
Grid-direct systems
Grid-direct systems offer more design flexibility than battery-based systems because you don’t have to worry about storing any energy; the grid will usually be there to make sure all the loads can run when the user wants them to. Even with this flexibility, you need to carefully consider the PV array you design and the components you connect to it. In Chapter 11, I show you what you need to consider in the sizing and design process, from evaluating the energy consumption at the site to the utility requirements for connecting to the grid to the calculations used when matching a PV array to an inverter.
Battery-based systems
Before you can size a battery-based system (either utility-interactive or stand-alone), you must evaluate the energy consumption used by the loads that will be powered via the battery bank. After you complete this step, you’re ready to move on to sizing the different system components, specifically the battery bank, the PV array, the charge controller, and the inverter. Chapter 12 has the how-to on sizing these components. (If you need to incorporate a generator into any battery-based system design, Chapter 12 has you covered as well.)
Conductors and safety devices
PV systems have some rather unique properties that need your attention when sizing wiring and safety components. The conductors are exposed to some extremely high temperatures, the current values passing through those conductors are at the mercy of the sun, and on top of all that, the DC current passing through the system requires you to seek out components that are specially listed for the application. Never fear. I walk you through the processes of properly choosing and sizing conductors, conduit, and overcurrent protection devices in Chapter 13.
Bringing a PV System to Life
After you spend all the required time designing a PV system, you’re ready for the real fun: going out in the sun and putting the modules to work. The next sections are dedicated to the different portions of the installation process to help get you up to speed. Of course, every situation you encounter will be slightly different from the last, but the fundamental ideas and processes behind PV system installation remain constant.
Permitting
An important activity takes place before a PV system is ever installed: permitting. The local building department is responsible for providing permits for any PV installation. You must apply for this permit, just like you would if you were doing any other major construction project.
Generally, you need to have two permits issued to you: an electrical permit and a building permit. The electrical permit is required so that the building department can ensure that the electrical portion of the system is safe, and the building permit helps keep the building safe from mechanical failure. (For full coverage of the permitting process, turn to Chapter 14.)
Staying safe
The safety of all individuals on the job site should be the most important factor during any installation — period. When you’re installing a PV system, you’ll be on a construction site with numerous hazards. The Occupational Safety and Health Administration (OSHA) rules regarding construction-related trades will be in full effect, and you need to be sure to address these requirements. The OSHA Web site, www.osha.gov, is full of information and resources to help you make your work sites as safe as possible.
Just because PV systems deal with solar power doesn't mean they don’t possess the same electrical hazards associated with any other electrical system. Always keep this fact in mind. Also, because PV systems run on energy they obtain from the sun, you’re going to be working on ladders, accessing roofs, and working in locations that are fully exposed to the elements — all of which add even more safety hazards you need to be aware of. (For a review of the major safety elements you need to consider, as well as methods you can use to keep yourself and others safe during a system installation, turn to Chapter 15.)
It takes a single accident to not only seriously injure an individual but also cripple an entire business. So do whatever you have to do to keep safety top of mind during each and every installation job.
Putting together the mechanical parts
For many PV system installers, the truly difficult part of any PV installation is the mechanical portion, which includes setting up the rack to hold the modules and evaluating the interaction between the PV array and the building. Depending on the location of the array (on a roof or on the ground), the installation of the mechanical components can represent a large portion of the time spent on the job site. Refer to Chapter 16 for a complete rundown of the issues you’ll face as you install the mechanical components of a PV system, as well as effective solutions for them.
A number of PV installations occur on rooftops, especially for residential systems. Whenever you’re working with a rooftop system, you need to carefully consider the methods used to attach the racking system to the roof. For ground-mounted systems (including top-of-pole mounting), you have to evaluate how you plan to keep the array in place without overtaxing the racking system or constructing a structure that can support a small country.
Adding the electrical parts
The electrical installation is always the portion of PV systems that receives the most attention — and rightly so given the numerous regulations you must comply with. The majority of these regulations are spelled out in the PV-specific portion of the National Electrical Code® (NEC®), specifically Article 690. I point out the highlights of Article 690 later in this chapter; consider this information a primer on the NEC®, not a complete review of the Code. (Note: Some local building departments may have additional requirements, so be sure to check in with the local office to make sure you’re on the same page.)
As I walk you through the different portions of the electrical installation in Chapter 17, I refer to the NEC® and point out specific requirements. I cover the required locations for different electrical components such as disconnects and overcurrent protection, and I guide you through the ever-fun topic of grounding the PV system (as well as grounding methods that are commonly used throughout the United States). I also note the requirements you need to follow when connecting the PV system to the local utility grid.
You don’t have to memorize specific passages of the NEC®, but you do have to be knowledgeable about the layout and format of the Code so you can effectively refer to it while designing and installing your systems.
Commissioning, inspecting, and maintaining a system
After you install the system, you’re ready to commission it (in other words, you’re ready to flip the switch and release the magical electrons from the PV modules and put them to work). Before you get too excited, though, you need to take some time and make sure the system has been installed properly so you don’t have to spend the next three weeks on-site fixing a problem that could’ve been discovered earlier. I walk you through this self-inspection, as well as the commissioning process, in Chapter 18.
When you know for sure that the system works, you need to turn it off and await the official inspection from the local building department. You must set up an appointment for an inspector to come out and look everything over. The inspector’s job is to make sure you followed the basic requirements and installed the components you said you would. If he sees any major problems, he’ll document them and require you to fix them before he’ll pass the system and allow you to turn it on. Turn to Chapter 18 for the full scoop on inspection requirements and common problem areas in PV installations.
To avoid getting hung up for too long in the inspection process, speak with an inspector early in the process (even as early as when you apply for the permits). This way you can make sure you’re clear on the local building department’s guidelines and get initial approval on things like grounding and labeling while you’re in the design phase (when it’s easier to make changes).
Don’t think you’re done as soon as the system receives approval from the inspector. No matter how low maintenance it may be, every PV system still requires maintenance now and then. I outline the common maintenance issues you need to be aware of and share advice on how to approach them (as well as who’s responsible for them) in Chapter 18.
Introducing the Sections of Code You Need to Know
As you begin to install PV systems, including the electrical elements, you need to make sure you’re familiar and comfortable with the National Electrical Code® (NEC®), also referred to as NFPA 70®. I reference the NEC® (also known simply as the Code) throughout this book, directing you to specific sections and applications.
Here are some basics related to the NEC® that you may find helpful:
If you’ve never referenced the
NEC
®
or look at it only on rare occasions, I suggest you purchase a copy the
NEC
®
Handbook.
It contains the entire
NEC
®
, along with some pretty pictures and helpful explanations that make the Code easier to understand. Perhaps the easiest way to obtain a copy of the handbook is to head to the National Fire Protection Association’s Web site (
www.nfpa.org
) and click the Buy NFPA codes & standards link on the left-hand side of the page. From there, just search for the
NEC
®
Handbook.
The handbook is a little pricey, and you’ll have to keep purchasing new editions periodically. Rest assured, though, that the cost is worth it.
Always make sure you’re using the correct version of the handbook for your area. The
NEC
®
Handbook
is released every three years, but the local
jurisdiction
(the office that issues building permits) may not be using the most current version. To find out which version the jurisdiction in your client’s area is using, call the local building department.
As you work more and more with the Code, you’ll realize that people interpret the same section differently. The powers that be who author Code sections try for concrete language, but there’s no way to achieve total clarity with a document like this. If you ever have a question, your best bet is to research your question and maybe even consult with your electrical inspector to make sure you’re on the same page as he is (literally and figuratively).
Note:
The local
authority having jurisdiction
(AHJ) — in other words, the electrical inspector — has the final ruling on the Code interpretation; the Code is there as a guideline, but the enforcement is up to the AHJ.
Although a specific section in the
NEC
®
covers PV systems, you don’t get to ignore the other sections. The entire
NEC
®
applies to PV systems, so reference the other sections as appropriate. However, there may be situations where the requirements set in Article 690 are different than in other sections. In this situation, Article 690 supersedes the other Code sections because it relates to PV installations.
Chapter 2
Checking Out Common Components and Systems
IN THIS CHAPTER
Identifying the major parts of a PV system
Distinguishing between battery-based and battery-less systems
Helping your customers select the correct system for their needs
