Photovoltaic (PV) systems generate electricity directly from the light of the sun, and grid-connected systems are becoming increasingly important in many electricity supply networks. The photovoltaic effect is described and the use of standard test conditions to define the performance of PV equipment explained. The bond and band models are used to explain the behaviour of an illuminated silicon p–n junction and the shape of its V–I characteristic. Operation of a PV cell at varying irradiance and cell temperature is demonstrated and the importance of operating at the maximum power point explained. The equivalent circuit of a PV cell is shown. The connection of multiple cells into a PV module is described together with the metrics that are used to describe the performance of PV arrays. The principle of operation of a grid-connected PV system and its inverter are described. A final section summarizes the main technologies used to manufacture the different generations of PV cells. The chapter is supported by 7 examples, 16 questions with answers and full solutions in the accompanying online material. Further reading and online resources are identified.

The present importance of fossil energy is recognized and the consequences of its exponential growth explained. The mechanism of global warming from increasing greenhouse gases in the atmosphere is summarised and the need for a transition to renewable energy is identified. The units that are usually used to describe energy are listed. The consequences of exponential growth are explained. Approaches to limiting energy use and the difficulties of reducing energy use are discussed. The consequences of applying discounted cash flow analysis in the economic appraisal of energy-efficiency measures are described. The challenges of low-carbon energy electricity generation are discussed and the carbon intensity of generation illustrated. The low-capacity factors of many renewable energy sources and the high-capacity margin of an electrical power system with renewable energy generation are described. Environmental and social impacts of renewable energy schemes are summarized. The chapter is supported by 4 examples, 13 questions with answers and full solutions in the accompanying online material. Further reading and online resources are identified.

Most renewable energy sources depend on the sun and so vary with time and ambient conditions. Hence a consistent supply of renewable energy requires energy storage. The main approaches to storing renewable energy are described and quantified. Pumped hydro, compressed air and flywheels are discussed. Storing heat in the fabric of buildings and hot water using sensible heat are described. The increasing importance of phase change materials to store energy through latent heat is recognized. Battery technology is developing very fast; the principles of lithium-ion batteries are explained, together with their advantages and disadvantages. The various materials currently used for the positive electrode are listed. The electrochemistry of various battery technologies is summarized as well as how a large number of cells are connected to form are a useful store of energy. The principle of flow batteries is demonstrated and approaches to the estimation of the lifetime of a lithium-ion battery discussed. The chapter is supported by 10 examples, 16 questions with answers and full solutions in the accompanying online material. Further reading and online resources are identified.

The second edition of this popular textbook has been extensively revised and brought up-to-date with new chapters addressing energy storage and off-grid systems. It provides a quantitative yet accessible overview of the renewable energy technologies that are essential for a net-zero carbon energy system. Covering wind, hydro, solar thermal, photovoltaic, ocean and bioenergy, the text is suitable for engineering undergraduates as well as graduate students from other numerate degrees. The technologies involved, background theory and how projects are developed, constructive and operated are described. Worked examples demonstrate the simple calculation techniques used and engage students by showing them how theory relates to real applications. Tutorial chapters provide background material supporting students from a range of disciplines, and there are over 150 end-of-chapter problems with answers. Online resources, restricted to instructors, provide additional material, including copies of the diagrams, full solutions to the problems and examples of extended exercises.

Waterwheels have been used for centuries for grinding corn, and the first hydro turbine was built almost 200 years ago. Hydro power now produces around 16% of worldwide electrical energy. The hydrological cycle is described and the use of flow duration curves to quantify the resource is demonstrated. The power that can be generated from the hydro resource is calculated, as well as the energy that can be stored in a reservoir. The difference between impulse and reaction turbines is explained with illustrations, and simple approaches to their analysis described. High-, medium- and low-head hydro schemes are described. The use of specific speed to choose the type of turbine for a site is demonstrated. The environmental impact of hydro schemes is discussed. The development of small hydro schemes is addressed as well as the use of Archimedes screw generators. The chapter is supported by 6 examples, 16 questions with answers and full solutions in the accompanying online material. Further reading and online resources are identified.

Wind energy is a major source renewable electricity generation in many countries and the diameter of wind turbine rotors is increasing. Onshore and offshore wind farms are described. The principles of wind turbine operation is explained and the importance of the power curve identified. Wind turbine rotors are analysed using axial momentum theory and the Betz limit; the power and torque coefficients are derived using the axial momentum factor. The generation of torque through lift on the blades is described and the principles of pitch and stall power regulation discussed. Fixed- and variable-speed operation of wind turbine rotors is described and variable-speed operations using two full-power converters demonstrated. Site wind speeds are described in terms of Weibull statistics and the method of bins discussed. The importance of wind turbulence and its effect on turbines is identified. Development of wind farms and the use of measure–correlate–predict to estimate long-term windspeeds is reviewed. The chapter is supported by 3 examples, 14 questions with answers and full solutions in the accompanying online material. Further reading and online resources are identified.

Many renewable energy sources produce electricity, and the fundamental operation of a national alternating current electric power system is described. The difference between real and reactive power is explained. The impact of renewable energy sources on the voltage of the power system is demonstrated through an example and approaches to controlling network voltages are discussed. The control of frequency is described and the importance of maintaining sufficient inertia is highlighted. Scheduling generation in a power system with significant fraction of renewable energy generation is explained. Approaches to demand-side participation and the importance of this concept are discussed. The connection of onshore and offshore wind farms to the power system is discussed. Approaches to the design of PV farms are illustrated. The chapter is supported by 6 examples, 10 questions with answers and full solutions in the accompanying online material. Further reading and online resources are identified.

Communities living far from a grid network are increasingly being supplied by off-grid renewable energy systems. However, a consensus of the best approach to their design has yet to emerge. A number of options are being trialled and these are described. Small dc photovoltaic systems with batteries are well established but can only supply limited amounts of power. An example of the supply of power to a remote health facility is shown. Microgrids combine a number of energy sources connected using either ac or dc. These connection architectures are demonstrated. An example of an operating ac microgrid is shown, together with the initial design calculations of the scheme. The concept of community energy is explained with a demonstration of the potential benefits of peer-to-peer energy trading. The chapter is supported by 4 examples, 7 questions with answers and full solutions in the accompanying online material. Further reading and online resources are identified.

The development and appraisal of renewable energy schemes is described. The phases of project development are explained, as well as the importance of careful assessment of the renewable energy resource. The use of a special purpose vehicle (SPV) for the development of projects is discussed and the agreements and contracts that are required for a scheme are listed. Simple discounted cash flow calculations are used for the economic appraisal of a renewable energy scheme. The importance of the Environmental Impact Assessment and the production of an Environmental Statement are emphasized. The chapter is supported by 1 example, 7 questions with answers and full solutions in the accompanying online material. Further reading is identified.

Radiation from the sun ultimately drives most of the forms of renewable energy discussed in this book, and this chapter describes the solar energy resource and how it is quantified. Direct and diffuse radiation are described with examples of irradiance and insolation (irradiation). The motion of the earth around the sun is described and the position of the sun as seen from the earth is illustrated. The geocentric or earth-centred representation of earth–sun geometry is used to explain the optimal orientation of a solar energy collector. Equations are provided to determine the location of the sun from a point on the earth. The solar spectrum is described and the air mass concept explained. This short chapter is supported by 4 examples, 10 questions with answers and full solutions in the accompanying online material. Further reading and online resources are identified.

The second edition of this popular textbook has been extensively revised and brought up-to-date with new chapters addressing energy storage and off-grid systems. It provides a quantitative yet accessible overview of the renewable energy technologies that are essential for a net-zero carbon energy system. Covering wind, hydro, solar thermal, photovoltaic, ocean and bioenergy, the text is suitable for engineering undergraduates as well as graduate students from other numerate degrees. The technologies involved, background theory and how projects are developed, constructive and operated are described. Worked examples demonstrate the simple calculation techniques used and engage students by showing them how theory relates to real applications. Tutorial chapters provide background material supporting students from a range of disciplines, and there are over 150 end-of-chapter problems with answers. Online resources, restricted to instructors, provide additional material, including copies of the diagrams, full solutions to the problems and examples of extended exercises.

This type of flow is usually observed on surfaces with low permeability and has therefore been one of the central problems in urban hydrology; its relevance lies in the design of small engineering structures for roads, highways, airports, and also for some surface irrigation systems. Detailed numerical solutions of the shallow-water equations have shown that the analysis of most overland flow situations can be reliably simplified using the kinematic wave approximation. The basic assumption of this approach is that the friction slope can be taken to be equal to the slope of the underlying surface. Analytical solutions of the resulting equation, albeit for special runoff situations, still provide useful insight regarding the rising and recession hydrographs for more general applications.