Integration of Renewable Sources of Energy
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Foreword for the First Edition xix
Foreword for the Second Edition xxi
Preface for the First Edition xxiii
Preface for the Second Edition xxvii
Acknowledgements xxxi
1 Alternative Sources of Energy 1
1.1 Introduction 1
1.2 Renewable Sources of Energy 2
1.3 Renewable Energy versus Alternative Energy 4
1.4 Planning and Development of Integrated Energy 10
1.4.1 Grid?]Supplied Electricity 10
1.4.2 Load 11
1.4.3 Distributed Generation 12
1.5 Renewable Energy Economics 13
1.5.1 Calculation of Electricity Generation Costs 14
1.5.1.1 Existing Plants 14
1.5.1.2 New Plants 15
1.5.1.3 Investment Costs 15
1.5.1.4 Capital Recovery Factor 16
1.6 European Targets for Renewable Powers 16
1.6.1 Demand?]Side Management Options 17
1.6.2 Supply?]Side Management Options 19
1.7 Integrating Renewable Energy Sources 21
1.7.1 Integration of Renewable Energy in the United States 23
1.7.2 Energy Recovery Time 24
1.7.3 Sustainability 26
1.8 Modern Electronic Controls for Power Systems 29
1.9 Issues Related to Alternative Sources of Energy 31
References 35
2 Principles of Thermodynamics 37
2.1 Introduction 37
2.2 State of a Thermodynamic System 38
2.2.1 Heating Value 46
2.2.2 First and Second Laws of Thermodynamics and Thermal Efficiency 48
2.3 Fundamental Laws and Principles 49
2.3.1 Example of Efficiency in a Power Plant 51
2.3.2 Practical Problems Associated with Carnot Cycle Plant 54
2.3.3 Rankine Cycle for Power Plants 55
2.3.4 Brayton Cycle for Power Plants 58
2.3.5 Geothermal Energy 60
2.3.6 Kalina Cycle 61
2.3.7 Energy, Power, and System Balance 62
2.4 Examples of Energy Balance 66
2.4.1 Simple Residential Energy Balance 66
2.4.2 Refrigerator Energy Balance 67
2.4.3 Energy Balance for a Water Heater 68
2.4.4 Rock Bed Energy Balance 70
2.4.5 Array of Solar Collectors 70
2.4.6 Heat Pump 71
2.4.7 Heat Transfer Analysis 72
2.4.8 Simple Steam Power Turbine Analysis 73
2.5 Planet Earth: A Closed But Not Isolated System 77
References 79
3 Hydroelectric Power Plants 81
3.1 Introduction 81
3.2 Determination of the Available Power 82
3.3 Expedient Topographical and Hydrological Measurements 84
3.3.1 Simple Measurement of Elevation 84
3.3.2 Global Positioning Systems for Elevation Measurement 85
3.3.3 Pipe Losses 86
3.3.4 Expedient Measurements of Stream Water Flow 87
3.3.4.1 Measurement Using a Float 87
3.3.4.2 Measurement Using a Rectangular Spillway 88
3.3.4.3 Measurement Using a Triangular Spillway 89
3.3.4.4 Measurement Based on the Dilution of Salt in the Water 89
3.3.5 Civil Works 92
3.4 Hydropower Generator Set 93
3.4.1 Regulation Systems 93
3.4.2 Butterfly Valves 93
3.5 Waterwheels 93
3.6 Turbines 96
3.6.1 Pelton Turbine 97
3.6.2 Francis Turbine 99
3.6.3 Michell-Banki Turbine 102
3.6.4 Kaplan or Hydraulic Propeller Turbine 103
3.6.5 Deriaz Turbines 105
3.6.6 Water Pumps Working as Turbines 106
3.6.7 Specification of Hydro Turbines 107
References 109
4 Wind Power Plants 111
4.1 Introduction 111
4.2 Appropriate Location 112
4.2.1 Evaluation of Wind Intensity 112
4.2.1.1 Meteorological Mapping 116
4.2.1.2 Weibull Probability Distribution 118
4.2.1.3 Analysis of Wind Speed by Visualization 121
4.2.1.4 Technique of the Balloon 123
4.2.2 Topography 124
4.2.3 Purpose of the Energy Generated 124
4.2.4 Accessibility 124
4.3 Wind Power 125
4.3.1 Wind Power Corrections 126
4.3.2 Wind Distribution 128
4.4 General Classification of Wind Turbines 129
4.4.1 Rotor Turbines 131
4.4.2 Multiple?]Blade Turbines 131
4.4.3 Drag Turbines (Savonius) 132
4.4.4 Lifting Turbines 133
4.4.4.1 Starting System 134
4.4.4.2 Rotor 134
4.4.4.3 Lifting 134
4.4.4.4 Speed Multipliers 134
4.4.4.5 Braking System 135
4.4.4.6 Generation System 135
4.4.4.7 Horizontal?] and Vertical?]Axis Turbines 135
4.4.5 Magnus Turbines 136
4.4.6 System TARP-WARP 136
4.4.7 Accessories 139
4.5 Generators and Speed Control Used in Wind Power Energy 140
4.6 Analysis of Small Generating Systems 143
4.6.1 Maximization of Cp 145
References 148
5 Thermosolar Power Plants 151
5.1 Introduction 151
5.2 Water Heating by Solar Energy 152
5.3 Heat Transfer Calculation of Thermally Isolated Reservoirs 155
5.3.1 Steady?]State Thermal Calculations 155
5.3.2 Transient?]State Thermal Calculations 156
5.3.3 Practical Approximate Measurements of the Thermal Constants R and C in Water Reservoirs 158
5.4 Heating Domestic Water 159
5.5 Thermosolar Energy 160
5.5.1 Parabolic Trough 161
5.5.2 Parabolic Dish 163
5.5.3 Solar Power Tower 164
5.5.4 Production of Hydrogen 166
5.6 Economics Analysis of Thermosolar Energy 168
References 170
6 Photovoltaic Power Plants 173
6.1 Introduction 173
6.2 Solar Energy 174
6.3 Conversion of Electricity by Photovoltaic Effect 176
6.3.1 Photovoltaic Cells 177
6.4 Equivalent Models for Photovoltaic Panels 178
6.4.1 Dark?]Current Electric Parameters of a Photovoltaic Panel 179
6.4.1.1 Measurement of I¿ 180
6.4.1.2 Measurement of Rp 180
6.4.1.3 Measurement of Id 181
6.4.1.4 Measurement of ¿ 182
6.4.1.5 Measurement of Is 183
6.4.1.6 Measurement of Rs 183
6.4.2 Power, Utilization, and Efficiency of a PV Cell 183
6.5 Solar Cell Output Characteristics 188
6.5.1 Dependence of a PV Cell Characteristic on Temperature and PV Cells 190
6.5.2 Model of a PV Panel Consisting of n Cells in Series 193
6.5.3 Model of a PV Panel Consisting of n Cells in Parallel 195
6.6 Photovoltaic Systems 196
6.6.1 Irradiance Area 197
6.6.2 Solar Modules and Panels 198
6.6.3 Aluminum Structures 198
6.6.4 Load Controller 200
6.6.5 Battery Bank 200
6.6.6 Array Orientation 200
6.7 Applications of Photovoltaic Solar Energy 201
6.7.1 Residential and Public Illumination 201
6.7.2 Stroboscopic Signaling 202
6.7.3 Electric Fence 203
6.7.4 Telecommunications 203
6.7.5 Water Supply and Micro?]irrigation Systems 203
6.7.6 Control of Plagues and Conservation of Food and Medicine 205
6.7.7 Hydrogen and Oxygen Generation by Electrolysis 206
6.7.8 Electric Power Supply 208
6.7.9 Security Video Cameras and Alarm Systems 209
6.8 Economics and Analysis of Solar Energy 209
References 214
7 Power Plants with Fuel Cells 217
7.1 Introduction 217
7.2 The Fuel Cell 218
7.3 Commercial Technologies for the Generation of Electricity 220
7.4 Practical Issues Related to Fuel Cell Stacking 231
7.4.1 Low?] and High?]Temperature Fuel Cells 231
7.4.2 Commercial and Manufacturing Issues 232
7.5 Constructional Features of Proton Exchange Membrane Fuel Cells 233
7.6 Constructional Features of Solid Oxide Fuel Cells 236
7.7 Reformers, Electrolyzer Systems, and Related Precautions 237
7.8 Advantages and Disadvantages of Fuel Cells 238
7.9 Fuel Cell Equivalent Circuit 239
7.10 Water, Air, and Heat Management 246
7.10.1 Fuel Cells and Their Thermal Energy Evaluation 247
7.11 Experimental Evaluation of the Fuel Cell Equivalent Model Parameters 250
7.11.1 Determination of FC Parameters 253
7.12 Aspects of Hydrogen as Fuel 256
7.13 Load Curve Peak Shaving with Fuel Cells 258
7.13.1 Maximal Load Curve Flatness at Constant Output Power 258
7.14 Future Trends 260
References 263
8 Biomass?]Powered Microplants 267
8.1 Introduction 267
8.2 Fuel from Biomass 272
8.3 Biogas 274
8.4 Biomass for Biogas 275
8.5 Biological Formation of Biogas 277
8.6 Factors Affecting Biodigestion 277
8.7 Characteristics of Biodigesters 279
8.8 Construction of a Biodigester 281
8.8.1 Typical Size for a Biodigester 282
8.9 Generation of Electricity Using Biogas 282
References
286
9 Microturbines 289
9.1 Introduction 289
9.2 Principles of Operation 291
9.3 Microturbine Fuel 293
9.4 Control of Microturbine 294
9.4.1 Mechanical?]Side Structure 295
9.4.2 Electrical?]Side Structure 297
9.4.3 Control?]Side Structure 298
9.5 Efficiency and Power of Microturbines 303
9.6 Site Assessment for Installation of Microturbines 305
References 307
10 Earth Core and Solar Heated Geothermal Energy Plants 311
10.1 Introduction 311
10.2 Earth Core Geothermal as a Source of Energy 313
10.2.1 Earth Core Geothermal Economics 314
10.2.2 Examples of Earth Core Geothermal Electricity 316
10.3 Solar Heat Stored Underground as a Source of Energy 317
10.3.1 Heat Exchange with Nature 319
10.3.2 Heat Exchange with Surface Water 322
10.3.3 Heat Exchange with Circulating Fluid 322
10.4 Solar Geothermal Heat Exchangers 323
10.4.1 Horizontal Serpentines 324
10.4.2 Vertical Serpentines 326
10.4.3 Mixed Serpentines 326
10.4.4 Pressurized Serpentines Heat Pump 326
10.5 Heat Exchange with a Room 328
References 329
11 Thermocouple, Sea Waves, Tide, MHD, and Piezoelectric Power Plants 331
11.1 Introduction 331
11.2 Thermocouple Electric Power Generation 331
11.2.1 Thermocouples 332
11.2.2 Power Conversion Using Thermocouples 334
11.2.3 Principle of Semiconductor Thermocouples 336
11.2.4 A Stack of Semiconductor Thermocouples 338
11.2.5 A Plate of Semiconductor Thermocouples 338
11.2.6 Advantages and Disadvantages of the Semiconductor Thermocouples 339
11.3 Power Plants with Ocean Waves 339
11.3.1 Sea Wave Energy Extraction Technology 341
11.3.2 Energy Content in Sea Waves 344
11.4 Tide?] Based Small Power Plants 345
11.5 Small Central Magnetohydrodynamic 347
11.6 Small Piezoelectric Power Plant 349
11.6.1 Piezoelectric Energy Conversion 350
11.6.2 Piezoelectric?]Based Energy Applications 352
References 352
12 Induction Generators 357
12.1 Introduction 357
12.2 Principles of Operation 358
12.3 Representation of Steady?]State Operation 360
12.4 Power and Losses Generated 362
12.5 Self?] Excited Induction Generator 364
12.6 Magnetizing Curves and Self?]Excitation 368
12.7 Mathematical Description of the Self?]Excitation Process 369
12.8 Grid?] Connected and Stand?]Alone Operations 372
12.9 Speed and Voltage Control 374
12.9.1 Frequency, Speed, and Voltage Controls 376
12.9.2 The Danish Concept: Two Generators on the Same Shaft 383
12.9.3 Variable?]Speed Grid Connection 384
12.9.4 Control by the Load versus Control by the Source 385
12.10 Economics Considerations 387
References 389
13 Permanent Magnet Generators 393
13.1 Introduction 393
13.1.1 PMSG Radial Flux Machines 394
13.1.2 Axial Flux Machines 394
13.1.3 Operating Principle of the PMSG 395
13.2 Permanent Magnets Used for PMSGs 397
13.3 Modeling a Permanent Magnet Synchronous Machine 398
13.3.1 Simplified Model of a PMSG 402
13.4 Core Types of a PMSG 407
13.5 PSIM Simulation of the PMSG 408
13.6 Advantages and Disadvantages of the PMSG 408
References 411
14 Storage Systems 413
14.1 Introduction 413
14.2 Energy Storage Parameters 416
14.3 Lead-Acid Batteries 419
14.3.1 Constructional Features 421
14.3.2 Battery Charge-Discharge Cycles 422
14.3.3 Operating Limits and Parameters 424
14.3.4 Maintenance of Lead-Acid Batteries 426
14.3.5 Sizing Lead-Acid Batteries for DG Applications 427
14.4 Ultracapacitors (Supercapacitors) 429
14.4.1 Double?]Layer Effect 430
14.4.2 High?]Energy Ultracapacitors 432
14.4.3 Applications of Ultracapacitors 433
14.5 Flywheels 435
14.5.1 Advanced Performance of Flywheels 436
14.5.2 Applications of Flywheels 437
14.5.3 Design Strategies 439
14.6 Superconducting Magnetic Storage System 441
14.6.1 SMES System Capabilities 443
14.6.2 Developments in SMES Systems 444
14.7 Pumped Hydroelectric Storage 446
14.7.1 Storage Capabilities of Pumped Systems 447
14.8 Compressed Air Energy Storage 449
14.9 Heat Storage 451
14.10 Hydrogen Storage 452
14.11 Energy Storage as an Economic Resource 453
References 457
15 Integration of Alternative Sources of Energy 461
15.1 Introduction 461
15.2 Principles of Power Interconnection 462
15.2.1 Converting Technologies 462
15.2.2 Power Converters for Power Injection into the Grid 464
15.2.3 Power Flow 466
15.3 Instantaneous Active and Reactive Power Control Approach 470
15.4 Integration of Multiple Renewable Energy Sources 473
15.4.1 DC?]Link Integration 475
15.4.2 AC?]Link Integration 477
15.4.3 HFAC?]Link Integration 478
15.5 Islanding and Interconnection Control 481
15.6 DG PLL with Clarke and Park Transformations 490
15.6.1 Clarke Transformation for AC?]Link Integration 490
15.6.2 Blondel or Park Transformation for AC?]Link Integration 492
15.7 DG Control and Power Injection 494
References 500
16 Distributed Generation 503
16.1 Introduction 503
16.2 The Purpose of Distributed Generation 506
16.2.1 Modularity 507
16.2.2 Efficiency 507
16.2.3 Low or No Emissions 507
16.2.4 Security 507
16.2.5 Load Management 508
16.3 Sizing and Siting of Distributed Generation 510
16.4 Demand?]Side Management 511
16.5 Optimal Location of Distributed Energy Sources 512
16.5.1 DG Influence on Power and Energy Losses 514
16.5.2 Estimation of DG Influence on Power Losses of Sub?]transmission Systems 518
16.5.3 Equivalent of Sub?]transmission Systems Using Experimental Design 521
16.6 Algorithm of Multicriterial Analysis 523
16.6.1 Voltage Quality in DG Systems 525
References 530
17 Interconnection of Alternative Energy Sources with the Grid 533 Benjamin Kroposki, Thomas Basso, Richard Deblasio, and N. Richard Friedman
17.1 Introduction 533
17.2 Interconnection Technologies 536
17.2.1 Synchronous Interconnection 536
17.2.2 Induction Interconnection 537
17.2.3 Inverter Interconnection 538
17.3 Standards and Codes for Interconnection 539
17.3.1 IEEE 1547 539
17.3.2 National Electrical Code 540
17.3.2.1 NFPA 70: National Electrical Code 540
17.3.2.2 NFPA 853: Standard for the Installation of Stationary Fuel Cell Power Plants 541
17.3.3 UL Standards 541
17.3.3.1 UL 1741: Inverters, Converters, and Controllers for Use in Independent Power Systems 541
17.3.3.2 UL 1008: Transfer Switch Equipment 541
17.3.3.3 UL 2200: Standard for Safety for Stationary Engine Generator Assemblies 543
17.4 Interconnection Considerations 543
17.4.1 Voltage Regulation 543
17.4.2 Integration with Area EPS Grounding 544
17.4.3 Synchronization 544
17.4.4 Isolation 545
17.4.5 Response to Voltage Disturbance 545
17.4.6 Response to Frequency Disturbance 546
17.4.7 Disconnection for Faults 548
17.4.8 Loss of Synchronism 549
17.4.9 Feeder Reclosing Coordination 549
17.4.10 Dc Injection 550
17.4.11 Voltage Flicker 550
17.4.12 Harmonics 551
17.4.13 Unintentional Islanding Protection 553
17.5 Interconnection Examples for Alternative Energy Sources 553
17.5.1 Synchronous Generator for Peak Demand Reduction 555
17.5.2 Small Grid?]Connected PV System 555
References 557
18 Micropower System Modeling with HOMER 559 Tom Lambert, Paul Gilman, and Peter Lilienthal
18.1 Introduction 559
18.2 Simulation 561
18.3 Optimization 566
18.4 Sensitivity Analysis 569
18.4.1 Dealing with Uncertainty 570
18.4.2 Sensitivity Analyses on Hourly Data Sets 573
18.5 Physical Modeling 574
18.5.1 Loads 574
18.5.1.1 Primary Load 575
18.5.1.2 Deferrable Load 575
18.5.1.3 Thermal Load 576
18.5.2 Resources 577
18.5.2.1 Solar Resource 577
18.5.2.2 Wind Resource 577
18.5.2.3 Hydro Resource 578
18.5.2.4 Biomass Resource 578
18.5.3 Components 579
18.5.3.1 PV Array 580
18.5.3.2 Wind Turbine 581
18.5.3.3 Hydro Turbine 582
18.5.3.4 Generators 583
18.5.3.5 Battery Bank 585
18.5.3.6 Grid 589
18.5.3.7 Boiler 591
18.5.3.8 Converter 591
18.5.3.9 Electrolyzer 592
18.5.3.10 Hydrogen Tank 592
18.5.4 System Dispatch 592
18.5.4.1 Operating Reserve 593
18.5.4.2 Control of Dispatchable System Components 594
18.5.4.3 Dispatch Strategy 597
18.5.4.4 Load Priority 598
18.6 Economic Modeling 598
References 601
Appendix A Diesel Power Plants 603
A.1 Introduction 603
A.2 The
Diesel Engine 604
A.3 Main Components of a Diesel Engine 604
A.3.1 Fixed Parts 605
A.3.2 Moving Parts 605
A.3.3 Auxiliary Systems 605
A.4 Terminology of Diesel Engines 606
A.4.1 The Diesel Cycle 606
A.4.2 Combustion Process 608
A.4.2.1 Four?]Stroke Diesel Engine 609
A.5 Cycle of the Diesel Engine 609
A.5.1 Relative Diesel Engine Cycle Losses 610
A.5.2 Classification of the Diesel Engine 610
A.6 Types of Fuel Injection Pumps 611
A.7 Electrical Conditions of Generators Driven by Diesel Engines 612
References 614
Appendix B The Stirling Engine 615
B.1 Introduction 615
B.2 The Stirling Cycle 616
B.3 Displacer?]Type Stirling Engine 619
B.4 Two?]Piston Stirling Engine 621
References 623
Index 625
1
Alternative Sources of Energy
1.1 Introduction
The basic human needs to survive are air, water, food, space to live, and energy, as well as the ability to reproduce, and humans have been constantly searching for means to harvest and convert energy to hence survive. But the interrelation of energy with other needs has not been so evident as in the recent years. When the industrial revolution in Europe caused an evolution of societies and large areas of increasing population density, people realized that factors such as comfortable housing and energy would be relevant to the development of a country. Fossil fuels have become essential in modern societies, and new strategies have been developed to guarantee their uninterrupted supply. In the last 250 years, our population, and correspondingly the demands for industrial and commercial goods, has increased. We have to consider that we live on a planet of constant size and constrained resources, and increased population and their demands may have consequences: economic constraints, new frontiers, wars, international agreements, and heavy pollution [1-3]. Engineers and scientists are working toward the optimized use of resources. Humans are excavating the lands for charcoal, petroleum, gas, uranium, and other minerals, polluting the atmosphere, rivers, oceans, and food sources. Burning fossil fuels and thermal energy conversion just increase entropy and contribute to exhaustion of our planet's energy resources.
In the past the approach to generate large amounts of electrical energy was realized by means of constructing large power plants, which were considered more efficient than smaller ones on an economic scale, such as the Three Gorges Dam in China (18?GW with structure for 22.5?GW), Itaipu Binacional in Brazil (14.0?GW), Sayano-Shushenskaya Dam in Russia (6.4?MW), Churchill Falls Generating Station in Canada (5.43?GW), and Guri Dam in Venezuela (2.0?GW). However, such large power plants caused immense floods, massive power transmission lines and towers, air pollution, modified waterways, devastated forests, large population densities in cities, and wars for the dominion of energy resources. Because of these trends in development, distances to energy sources are increasing, material capacities are reaching their limits, fossil reserves are being exhausted, and pollution is becoming widespread. New alternatives must be devised if humanity is to survive today and for the centuries to come.
1.2 Renewable Sources of Energy
The Earth receives solar energy as radiation from the sun in quantity that far exceeds the needs of the entire humankind. The sun generates wind, rain, rivers, and waves by heating the plane. Along with rain and snow, sunlight is necessary for plants to grow. Biomass, the organic matter that makes up plants, in general can be used to produce electricity, transportation fuel, and chemicals. Plant photosynthesis (essentially, the chemical storage of solar energy) creates a range of biomass products, from wood fuel to rapeseed, which can be used for heat, electricity, and liquid fuels.
Hydrogen can also be extracted from many organic compounds, as can water. Hydrogen is the most abundant element on Earth, but it does not occur naturally in gas form. It is always combined with other elements, such as oxygen to form water. Once separated from another element, hydrogen can be burned as a fuel or converted into electricity.
The sun also powers the evapotranspiration cycle, which allows water to generate power in hydro schemes-the largest source of renewable electricity today. Interactions with the moon produce tidal flows, which can produce electricity.
Although humans have been tapping into renewable energy sources (such as solar, wind, biomass, geothermal, and water) for thousands of years, only a fraction of their technical and economic potential has been captured and exploited. Yet renewable energy offers safe, reliable, clean, local, and increasingly cost-effective alternatives for all our energy needs. It can dismantle the power promoted by petroleum, coal, and radioactive materials [2-6].
Research has made renewable energy more affordable today than it was 30 years ago. Wind energy has declined from 40 cents per kilowatt hour (¢/kWh) to less than 5¢. Electricity from the sun through photovoltaics (which literally means "light electricity") has dropped from more than $1/kWh in 1980 to nearly 15¢/kWh today. Ethanol fuel costs have plummeted from $4/gal in the early 1980s to $1.20 today. As a result, renewable energy resource development will result in new jobs, local power plants, and less dependence on oil and radioactive materials from foreign countries [5-7].
There are some drawbacks in developing renewable energy solutions. An example is when solar thermal energy is used, because solar rays are captured through collectors (often huge mirrors) and solar thermal generation requires large tracts of land, and affects natural environment. The environment is also affected when buildings, roads, transmission lines, and transformers are built. In addition, the fluid often used for solar thermal generation is toxic, and spills can occur. Solar or photovoltaic cells are produced using the same technologies as those used to create silicon chips for computers, and this manufacturing process also uses toxic chemicals. In addition, toxic chemicals are used in batteries that store solar electricity through nights and on cloudy days. Manufacturing this equipment also has environmental effects. Therefore, even though the renewable power plant does not release air pollution or use fossil fuels, it still has an effect on the environment.
Wind power has also some drawbacks, involving primarily land use. For example, the average wind farm requires 17 acres to produce 1?MW of electricity (about enough electricity for 750-1000 homes). However, farmers and ranchers can use the land beneath wind turbines. Wind farms can cause erosion in desert areas, and they affect natural views because they tend to be located on or just below ridgelines. Bird deaths also result from collisions with wind turbines and wires. This is the subject of ongoing research. Ultimately, combined with energy efficiency, renewable energy can provide everything fossil fuels offer in terms of energy services: from heating and cooling to electricity, transportation, chemicals, illumination, and food drying.
Energy has always existed and has been used and transformed in one form or another. For example, the energy in a flashlight's battery becomes light energy when the flashlight is turned on. Food, the most natural stored chemical energy, resides in fat tissues and cells as potential energy. When the body uses that stored energy to do work, it becomes kinetic energy. Telephones transform a voice into electrical energy variations, which flow over wires or are transmitted through air. Other telephones change this electrical energy into sound energy through speakers. Cars use stored chemical energy in fuel to move, and they change chemical energy into heat and kinetic energy. Toasters change electrical energy into heat. Computers, television sets, and DVD players change electrical energy into coordinated types of mechanical movement and image and sound energy to reproduce the ambient of life. That means that as soon human beings are awake in the morning, they begin to use more energy than that keeping them alive to switch lights on, for a bath, morning cooking, heaters on, car on, going to work, and so on.
In all such transformations of energy, intermediary transformations are involved. For example, consider the case for a home computer. Electricity allows self-organization of the main processor, according to a preestablished program, to convert ventilator movement to the cooling process for the main processing unit and the motherboard. The alternating current (ac) source power after being distributed to all houses is converted into integrated direct current (dc) power to feed peripheral plates. After many electric processes, the monitor produces a luminous energy on screen. Many processes and intermediary sources are integrated into a simple computer. They produce heat, light, movement, and circulation of electrical current to make it an impressively organized machine. This diversity of energy forms is an example of the changes happening in power systems since the primary source conversion.
1.3 Renewable Energy versus Alternative Energy
All forms of energy are renewable after a lapse of time. For example, coal can be renewed in nature after millions, perhaps billions, of years. Sugar cane would take no more than one year to be replanted. Therefore, a source of energy is considered renewable if the time it takes to be recovered is referred to human life duration. Furthermore, a renewable energy source cannot run out and causes so little damage to the environment that its use does not need to be restricted. On the other hand, no energy system based on mineral resources is renewable because, one day, the mineral deposits will be used up. This is true for fossil fuels and uranium. The debate about when a particular mineral resource will run out becomes irrelevant in this context. A renewable energy source is replenished continuously.
Renewable energy sources-solar, wind, biomass (under specific conditions), and tides-are based directly or indirectly on solar energy. Hydroelectric power is not necessarily a renewable energy source because large-scale projects can cause ecological damage and...
