Why is an understanding of electricity necessary?

The CREST MSc concentrates mainly on those technologies that harness the Earth's natural energy flows and convert them to electrical energy. Therefore, an understanding of the ways in which electrical energy is generated and transported (whether in AC or DC applications) is fundamental to many aspects of these technologies.

Study tips

This section consists of six units (FE1 DC Circuits to FE6 Semiconductors) each with a series of compact study notes and some with self-test questions. In each section, work through the study notes sequentially. Make sure that you understand any worked examples. Where available, you may wish to tackle the self-test questions as they occur in the sequence. If you encounter difficulties, return to the study notes and focus on the relevant topics before re-visiting the self-test.

Introduction

Prior to commencing the foundation studies course, you should already have an understanding of the basic concepts of electricity, such as Ohm's law, series and parallel circuits and conductance. The following section is therefore intended only as a review of your existing knowledge.

Why is an understanding of DC Circuits necessary?

Electricity is generated transmitted, distributed and consumed mainly in AC form. This course mainly deals with those renewable energy technologies that are used to generate electricity; hence it is vital that a treatment of renewable energy technology deals with the integration of such sources into existing electrical networks.

DC circuit theory provides the necessary foundations for the treatment of AC circuits. It is also required in the analysis of photovoltaic systems and the understanding of power electronic converters used to interface some renewable energy-sourced generators to electrical networks.

AC circuit theory provides the information needed to understand the basic principles of:

the operation of electrical generators used to convert renewable energy into electricity.

the transfer of electrical energy from the point of generation to the point of use.

the effects of integrating dispersed renewable energy-sourced generation into a pre-existing power network fed mainly from conventional generators.

The material in the whole of this unit is required as background for all the other Foundation Units on electricity (FE-2 to FE-5).

At the beginning of each section the course module(s) that requires the material in this particular section as background knowledge are indicated in bold italics.

Study tips

This unit contains an itemised summary of the pre-requisite knowledge required prior to commencing the Foundation Studies course and self-test questions. You should be familiar with this materials from your high school Physics or university Science/Engineering degree courses. The material is very basic and it represents essential background knowledge for the study of AC circuits. You are recommended to study the unit in the following sequence:

From the "Syllabus" page, work through the list carefully making sure you are familiar with all the itemised elementary concepts. If any of these concepts are new to you (or perhaps you were once familiar with them but your memory requires refreshing), a link at the end of each section will take you to in-depth Foundation Backup (FB) material on each subject. It is hoped that very few students will need to follow this procedure!

Tackle the self-test questions as they occur in the sequence, if you decide to test your knowledge of this topic. If you encounter difficulties, return to the study notes and focus on the relevant topics before re-visiting the self-test.

Why is an understanding of DC Network Analysis necessary?

Renewable energy sources are used mainly to generate electrical power, which is injected into power networks consisting of a large number of transmission lines, other conventional generators and consumers. Such power networks, especially in developed countries, are of considerable complexity. To determine the way these injected powers flow from generators to consumers requires complex calculations based on network analysis. This unit provides background material for the development of AC circuit theory and of the mathematical expressions that define the power flows in a network.

The material in the whole of this unit is required as background knowledge for all the other Foundation Units on electricity (FE-3 to FE-5)

At the beginning of each section the course module(s) that requires the material in this particular section as background knowledge are indicated in bold italics.

Objectives

After completing this topic, you should understand:

Syllabus

Why is an understanding of AC Theory necessary?

Renewable energy sources are used mainly to generate AC electrical power, which is injected into power networks consisting of large number of transmission lines, other conventional generators and consumers. Such power networks, especially in developed countries, are of considerable complexity. To determine the way these injected powers flow from generators to consumers requires complex calculations based on network analysis. This unit introduces the basic AC circuit theory that enables students to carry out network analysis in simple power circuits consisting of R, L and C components. This knowledge is an essential prerequisite in the understanding of power flows in networks. Frequently, renewable energy generators are interfaced to power networks through power electronic converters. The non-linear nature of such converters is examined and the reasons why converters generate harmonics are explained. The undesirable effects of harmonics injected into power networks are discussed.

All sections of this unit are required as background material for Unit FE-4. Some sections contain simple exercises.

At the beginning of each section the course module(s) that requires the material in this particular section as background knowledge are indicated in bold italics.

Note: The text uses 60Hz rather than 50Hz as the mains frequency. This is of no consequence in the understanding of the material and in its application to 50Hz systems.

Objectives

After completing this topic, you should understand:

Why is an understanding of Power in AC Circuits necessary?

Renewable energy sources are used mainly to generate AC electrical power, which is injected into power networks consisting of a large number of transmission lines, other conventional generators and consumers. Such power networks, especially in developed countries, are of considerable complexity. To determine the way these injected powers flow from generators to consumers requires complex calculations based on network analysis. This unit introduces the basic concepts of active, reactive and apparent power. These are the basic tools needed to understand and calculate flows of energy from generators to consumers. In all AC power systems (excluding very low capacity ones) power is generated and transported in three-phase form. The reasons why this is so and the tools to deal with power flows in such systems are outlined. All this knowledge is an essential prerequisite for the understanding of power flows from renewable generators into networks.

All sections of this unit are required as background material for Unit FE-5.

At the beginning of each section the course module(s) that requires the material in this particular section as background knowledge are indicated in bold italics.M/p>

Note: The text uses 60Hz rather than 50Hz as the mains frequency. This is of no consequence in the understanding of the material and in its application to 50Hz systems.

Objectives

After completing this topic, you should understand:

  Syllabus

Power in AC Circuits. Three-phase Systems

Why is an understanding of Electrical Machines necessary?

Renewable energy sources are used mainly to generate AC electrical power, which is injected into power networks consisting of large number of transmission lines, transformers and other conventional generators and consumers. Such power networks, especially in developed countries, are of considerable complexity. To determine the way these injected powers flow from generators to consumers requires complex calculations based on network analysis. This unit introduces the basic concepts of the electrical machines that are found in power networks. Transformers are used in all but the most primitive networks to step-up or -down transmission network voltages for efficient operation. The knowledge of the transformer equivalent circuit is essential to perform power system analysis studies. There are two types of generators (synchronous and asynchronous) for the conversion of mechanical into electrical energy. Knowledge of the basic operating principles of these generators is essential to appreciate their advantages and limitations when used in renewable energy conversion systems.

All sections of this unit are required as background material for Unit FE-6.

At the beginning of each section the course module(s) that requires the material in this particular section as background knowledge are indicated in bold italics.M/p>

Note: The text uses 60Hz rather than 50Hz as the mains frequency. This is of no consequence in the understanding of the material and in its application to 50Hz systems.

Objectives

After completing this topic, you should understand:

What is this unit about?

This unit provides some basic qualitative grounding on the physics underpinning the development of semiconductor devices. The atomic structure of matter is discussed with reference to (i) the distinct energy levels at which electrons may exist in isolated atoms and (ii) the energy bands in solids. The differences between a conductor, an insulator and a semiconductor are then explained in terms of conduction, forbidden and valence bands. The electron and hole flow theory in semiconductors is then discussed as well as how the properties of the semiconductor are affected by doping. The characteristics of N-type and P-type semiconductors are explained and how a PN junction is realised in practice. The investigation of current flow in PN junctions with forward and reverse bias leads to the concept of the semiconductor diode and its construction and operation. Finally the principle of transistor operation is briefly outlined and how this has spawned solid state switching devices suitable for power electronic applications.

Why is an understanding of Semi-conductors necessary?

The direct generation of electricity from sunlight is a major part of the Solar Power I and II modules. This energy conversion is achieved through photovoltaic devices, which are based on semiconductor technology. This unit provides the basic qualitative background material necessary to understand the analytical treatment of photovoltaics in Solar Power I. Renewable energy generators are often interfaced to the electricity power networks through energy conditioning interfaces. Such interfaces use power electronic switching devices to implement the conditioning. The qualitative knowledge of how solid switching devices operate is an essential prerequisite for the understanding of the mode of operation of interfaces and the influence such interfaces have on the RE generators and power networks to which they are connected.

Objectives

After completing this topic, you should understand:

 Contents

1. Semiconductor Theory

2. The PN Junction

3. The Junction Barrier

4. Solid State Switching Devices

Self-Test