Ryan Mayfield has been working in the renewable energy field since 1999. He is President of Renewable Energy Associates, a consulting firm providing design, support, and educational services for commercial photovoltaic systems. He is also Photovoltaic Systems Technical Editor for StarPro magazine, where he regularly contributes feature articles.

Introduction 1

About This Book 1

Conventions Used in This Book 2

What You’re Not to Read 3

Foolish Assumptions 3

How This Book Is Organized 3

Part 1: Here Comes the Sun: Shedding Some Light on PV Systems 4

Part 2: Digging into Complete System Details 4

Part 3: Sizing a PV System 4

Part 4: Installing a PV System 4

Part 5: The Part of Tens 5

Icons Used in This Book 5

Where to Go from Here 5

Part 1: Here Comes the Sun: Shedding Some Light on PV Systems 7

Chapter 1: The Photovoltaic Revolution 9

Peeking into the Past, Present, and Future of PV Installations 9

Acquainting yourself with typical PV applications 10

Checking out PV pros and cons 10

Looking into the future of PV 11

Introducing PV Components and Systems 11

Knowing Your Electricity A-B-Cs 12

Solar Resource 101 13

Surveying a PV System Site 13

Delving into PV System Details 14

PV modules 14

Batteries 14

Charge controllers 15

Inverters 15

Wiring and safety devices 15

Sizing a PV System 16

Grid-direct systems 16

Battery-based systems 16

Conductors and safety devices 17

Bringing a PV System to Life 17

Permitting 17

Staying safe 17

Putting together the mechanical parts 18

Adding the electrical parts 18

Commissioning, inspecting, and maintaining a system 19

Introducing the Sections of Code You Need to Know 20

Chapter 2: Checking Out Common Components and Systems 21

Introducing the Components That Make Up PV Systems 21

PV modules and racking 22

Battery bank 23

Charge controller 24

Inverter 24

Loads 25

Load centers 26

Disconnects and overcurrent protection 27

Utility interconnection 27

Differentiating between PV System Types 29

Grid-direct systems 29

Battery-based systems 31

Figuring Out the Right System Type for Any Situation 34

The customer is connected to the grid 34

The customer isn’t connected to the grid 35

Chapter 3: Powering through Electricity Basics 37

Going with the Flow: Current 38

Understanding amps 38

Distinguishing between direct current and alternating current 39

Measuring current with a meter 40

May the (Electromotive) Force Be with You: Voltage 43

Grasping the concept of voltage 43

Getting a grip on nominal voltage and operating voltage 43

Measuring voltage 44

Making a Stop: Resistance 46

Introducing ohms 47

Measuring resistance 47

Connecting Current, Voltage, and Resistance with Ohm’s Law 49

Pondering Power and Energy 50

Recognizing the differences between power and energy 50

Relating power to current, voltage, and resistance with the power equation 51

Calculating energy in terms of watt-hours 53

Introducing amp-hours, a companion to watt-hours 53

Wrapping Together Current, Voltage, Resistance, Power, and Energy 54

Another Electricity Concept: Circuit Configurations 55

Series 56

Parallel 57

Series-parallel 58

Chapter 4: Warming Up to the Solar Resource 59

High (Or Low) Energy: Solar Radiation 60

Distinguishing between direct radiation and diffuse radiation 60

Determining the intensity of solar radiation: Irradiance 61

Calculating solar radiation energy: Irradiation 65

Just for a day: Peak sun hours 66

Examining the Effects of the Sun’s Path on the Earth 69

Getting a grip on seasonal effects 70

Understanding the sun’s relationship to your location: Altitude and azimuth 72

Ticking off solar time 74

Interpreting sun charts 74

Opening up to the solar window 76

Positioning PV Modules to Make the Most of the Solar Resource 77

Introducing tilt angle 77

Orienting your array to the azimuth 79

Chapter 5: Properly Selecting a Site for a PV System 81

Setting the Stage for a Site Survey 82

Putting aside enough time 82

Creating a standard site-survey form 83

Toting a site-survey bag 83

Picture This: Documenting Your Entire Site Survey with Digital Photos 84

Collecting Basic Information during a Site Survey 86

General site information 86

Structural and mechanical information 87

Electrical information 89

Measuring Information in Degrees 90

Understanding magnetic declination 91

Calculating the array’s tilt angle and azimuth 93

Exploring Shading-Analysis Tools 95

Interpreting the Data and Bringing It All Together 97

Analyzing reports from your shading-analysis tool 98

Considering the total solar resource factor 98

Using other collected information to plan out the design and installation 100

Part 2: Digging Into Complete System Details 103

Chapter 6: PV Modules: From Sand to Electricity 105

Creating Solar Electricity: It All Starts with a Cell 106

Getting a grip on cell construction and manufacturing 106

Connecting cell construction to the photovoltaic effect 108

Reviewing Common Types of PV Modules 108

Checking out crystalline modules 109

Looking at thin film modules 111

Pointing Out Electrical Specifications on PV Modules 113

Current specifications 114

Voltage specifications 115

Maximum power point 116

Voltage temperature coefficient 117

Power tolerance 118

Series fuse rating 118

Surveying Test Conditions for PV Modules 118

Standard test conditions 119

Environmental effects on standard test conditions 120

Relating Current and Voltage in IV Curves 122

An IV curve with varying temperature 123

An IV curve with varying irradiance 124

Chapter 7: The Basics of Batteries 127

The Fundamentals of Battery Anatomy and Operation 128

Constructing a battery, from cell to bank 128

Discovering how batteries charge and discharge 130

Comparing Different Types of Batteries 133

Lead-acid batteries 133

Lead-calcium batteries 136

Nickel-cadmium batteries 136

Comprehending Battery Capacity 137

Considering the C rate for capacity 137

Recognizing factors that affect capacity 138

Specifying Batteries 141

Specifying the type of battery to use 141

Specifying the battery bank size 142

Chapter 8: Keeping Current and Voltage in Check: Charge Controllers 147

The Essentials of Charge Controllers 148

Seeing how a charge controller works in stages 148

Surveying special effects provided by some charge controllers 151

Maximum Power Point Tracking Technology 153

How MPPT works 153

The pros and cons of MPPT controllers 154

Pulse-Width Modulation Technology 155

How PWM works 155

The pros and cons of PWM controllers 156

Specifying a Charge Controller 156

Chapter 9: Inverters: AC (From) DC 157

Getting the Goods on Grid-Direct Inverters 158

Basic operation 158

Standard features 159

Power output sizes 162

The importance of transformers 162

Investigating Battery-Based Inverters 164

Utility-interactive inverter operation 165

Stand-alone inverter operation 166

Standard features for all battery-based inverters 167

Sizes of battery-based inverters 168

Low-frequency transformer technology 168

Specifying Any Inverter 168

Grid-direct 169

Battery-based 170

Chapter 10: Staying Secure: Wiring and Safety Components 173

Defining the Circuits in a PV System 174

Checking Out Types of Conductors 175

USE-2 176

PV wire 176

Building wiring 177

Battery wiring 178

Ground wiring 178

Considering Kinds of Conduit 179

Metallic conduit 179

Nonmetallic conduit 180

Delving into Disconnects 181

Perusing Overcurrent Protection Devices 182

Circuit breakers 183

Fuses 183

Focusing on Ground Fault Protection 184

Looking at the Basics of Labels 185

Part 3: Sizing a PV System 187

Chapter 11: Sizing a Grid-Direct System 189

First Things First: Evaluating the Budget and the Available Array Area 190

Estimating the Site’s Annual Energy Production 191

Sizing the Array to Meet Your Client’s Energy Consumption 193

Determining annual energy consumption 193

Looking at contract options with the utility 194

Using consumption and contract options to select an array’s needed power value 195

Getting Ready to Match an Inverter to an Array 196

Matching Power Values for an Array and an Inverter 197

Coming Up with the Right Voltage Values for Your Array and Inverter 199

Establishing the inverter’s AC voltage 200

Defining the inverter’s DC voltage window 200

Calculating the modules’ maximum DC voltage contribution 201

Figuring out the modules’ minimum DC voltage contribution 208

Bringing It All Together: Combining Your Power and Voltage Information 213

One Last Check: The Inverter’s Maximum Current Input 214

Chapter 12: Sizing a Battery-Based System 215

Get Loaded: Looking at Loads in a Battery-Based System 216

Evaluating the loads that the battery bank must serve 216

Calculating the energy required during an outage for utility-interactive systems 219

Determining the average daily energy consumption for stand-alone systems 219

Sizing the Battery Bank 222

Inverter efficiency 222

The days of autonomy 223

The temperature used for battery operation 223

The depth of discharge 224

Nominal voltages 225

Figuring out the battery capacity you need 226

Strung along: Wiring the battery bank 227

Sizing the PV Array 229

Sizing the array in a utility-interactive system 229

Sizing the array in a stand-alone system 230

Sizing the Charge Controller 232

Voltage specifications 233

Power or amperage specifications 234

A check before you move on: Comparing the array size to the battery capacity 236

Sizing the Inverter 236

Viewing voltage output 237

Calculating the power draw 237

Staying in charge 238

Looking at surge ratings 238

Evaluating inverter and array power output 239

Incorporating a Generator 239

Generator features 240

Generator sizing 241

Chapter 13: Sizing Conductors, Conduit, and Safety Components 243

Conductor Sizing 101 244

Defining the PV circuits’ maximum and continuous current 245

Calculating non-PV circuits’ maximum current 246

Considering conditions of use with some handy tables 247

Putting together the details to determine conductor sizing 250

Accounting for voltage drop after you size your conductors 253

Sizing Conduit 257

Sizing Overcurrent Protection Devices and Disconnects 258

Beginning with a few basics 258

Placing protection on PV circuits 259

Protecting inverter circuits 260

Part 4: Installing a PV System 261

Chapter 14: The Permitting Process 263

Obtaining Permits before You Install a PV System 263

In the beginning: Having the right licenses and certifications 264

Home grown: Permitting for residential systems 265

Big business: Permitting for commercial systems 269

Not Just Pretty Pictures: Creating Drawing Sets 272

Calling out components clearly 273

Depicting equipment locations 273

Showing conductor-sizing calculations 273

Jotting down job notes 274

Chapter 15: Staying Safe Anytime You Work on a PV System 275

Getting a Grip on General Construction Site Safety 276

Identifying job-site obstacles and putting on protective gear right away 276

Safely working alone and with others 277

Taking in tips for tool safety 278

Limiting your exposure to the elements 278

Stowing a first-aid kit on the job site 279

Looking at Ladder Safety 279

Selecting your stash of ladders 279

Properly setting up any ladder 281

Raising the Issue of Rooftop Safety 282

Restraining yourself with fall protection 283

Storing your tools 283

Maintaining safe walkways 285

Examining Electrical Safety 285

Staying aware of general shock hazards 285

Working with circuits 286

Charging Ahead with Battery Safety 290

Chapter 16: Assembling the Mechanical Parts 293

Surveying PV Array Mounting Methods 294

Roof mounting 295

Ground mounting 300

Top-of-pole mounting 302

Building-integrated mounting 303

Considering Loading When You Mount an Array on a Roof 305

Following building codes 305

Accounting for additional dead load 305

Looking at live loads 307

Properly Attaching an Array to a Roof 309

Making attachments with lag screws 309

Sealing roof penetrations with flashing 310

Supporting Ground and Top-of-Pole Mounting 313

Chapter 17: Integrating the Electrical Elements 315

Location Is Everything: Knowing Where to Place Electrical Equipment 316

Manufacturers’ requirements for equipment locations 316

Locations for disconnecting means 317

Combiner boxes and junction boxes and wiring, oh my! 318

Working on Wiring 319

Seeing red (and green and white): Color-coding 319

Managing wires on PV modules 321

Protecting wires with conduit 322

Bonding Yourself to Grounding 323

Equipment grounding 323

System grounding 326

Connecting to the Utility 329

Determining the utility’s requirements 329

Making a load side or line side connection 331

Chapter 18: Commissioning, Inspecting, and Maintaining a PV System 335

Making a List and Checking It Twice: Preparing for Commissioning 336

Mechanical elements? Check! 336

Electrical elements? Check! 337

Start ’Er Up: The Commissioning Process 341

Putting safety first 342

Gathering the gear you need 342

Commissioning different types of systems 343

Verifying that the system is working 347

Arming Yourself for Inspection Issues 349

Not having “a neat and workmanlike manner” 350

Forgetting about aesthetics 350

Failing to manage conductors on the array 350

Neglecting to label the system 351

Surveying System Maintenance 353

Mechanical maintenance 354

Electrical maintenance 354

Maintenance on a higher level: Taking care of battery banks 355

Part 5: The Part of Tens 359

Chapter 19: Ten Ways to Avoid Common Code Mistakes 361

Providing Proper Working Clearance 362

Supplying the Right Structural Support 362

Keeping Water out of Buildings with Flashing 363

Ensuring All Conductors Have the Necessary Ratings 363

Managing the Conductors on Modules 364

Selecting the Correct Conduit 364

Locating the Disconnects 365

Grounding the Equipment 365

Grounding the System 366

Labeling the System Properly 366

Chapter 20: Ten Ways to Maximize Energy Production for Your Clients 367

Select the Right Site 367

Orient the Array Correctly 368

Configure the Array Properly 368

Work within the Limits of the Utility Voltage 369

Choose the Correct Inverter 369

Size Conductors Appropriately 370

Keep the Components Cool 370

Advise Clients to Monitor Their System 371

Clean the Array Periodically 371

Inspect the Array Annually 372

Index 373

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