Clean Energy

By Ronald M. Dell, David A. J. Rand

The Royal Society of Chemistry

Copyright © 2004 The Royal Society of Chemistry
All rights reserved.
ISBN: 978-0-85404-546-4

Contents

Abbreviations, Symbols and Units Used in Text, xviii,
Glossary of Terms, xxiii,
Chapter 1 Energy Production and Use, 1,
Chapter 2 Clean Fuels, 32,
Chapter 3 Electricity Generation, 57,
Chapter 4 Renewable Energy – Thermal, 90,
Chapter 5 Renewable Energy – Electrical, 125,
Chapter 6 Why Store Electricity?, 161,
Chapter 7 Physical Techniques for Storing Energy, 179,
Chapter 8 Hydrogen Energy, 198,
Chapter 9 Battery Storage, 242,
Chapter 10 Electric Propulsion, 268,
Chapter 11 Towards 2020, 293,
Appendix Conversion Factors, 313,
Subject Index, 315,

CHAPTER 1

Energy Production and Use

It is generally held that the present production and use of energy pose a serious threat to the global environment, particularly in relation to the emission of greenhouse gases (principally, carbon dioxide, CO2) and the perceived influence of these gases on the Earth’s climate. Accordingly, industrialized countries are examining a whole range of new policies and technology issues to make their energy futures ‘sustainable’. That is, to maintain economic growth and cultural traditions whilst providing energy security and environmental protection. Clearly, the world is set to make major changes so as to maintain adequate supplies of Clean Energy.

1.1 A Brief History of Energy Technology

The mastery of energy has always been the key to a better world. Ironically, though, the concept of energy is difficult to grasp; it is an abstract quantity that manifests itself in many forms, e.g. chemical, electrical, mechanical, radiant, nuclear, and thermal energy. In an electrical power station, for example, fossil fuel (chemical energy) is converted via steam to mechanical energy and then, via an alternator, to electrical energy. In an electric vehicle, a battery is used to convert chemical energy into electrical energy, which is then converted to mechanical energy by a motor. The scientific use of the term ‘energy’ was introduced by Thomas Young (1773–1829), an English physicist, physician, and Egyptologist who also provided the most astute definition to date, namely: ‘energy is the ability to do work.’ It is commonly understood that ‘work’ means the application of effort to accomplish a task, and the rate at which work is performed is called ‘power’. Thus, machines consume energy, perform work, and provide power. A simple example of the relationship between these quantities is shown in Figure 1.1. The ‘efficiency’ of a machine is a measure of its performance obtained from the ratio of energy output to energy input. The efficiency must always be less than 100% (which would imply perpetual motion).

Until the advent of the Industrial Revolution in the 18th century, humankind derived its power mainly from its own exertions, from animal muscle (horses, oxen, camels, etc.), from the wind (windmills and sailing ships), and from water (watermills). Even with these limited resources, however, some of humankind’s achievements were remarkable. Consider, for instance, the ancient pyramids of Egypt, prehistoric Stonehenge, or the great cathedrals of Europe built in the Middle Ages. As late as the 18th and early 19th centuries, an extensive system of canals was constructed across England to permit the conveyance of freight by horse-drawn barge. Such canals, which are still in use today for recreational boating, were all hand-dug by labourers with spades and wheelbarrows. These feats are truly awe-inspiring when viewed from the comfort of the present mechanized age.

Sources of power began to change with the development of the ‘atmospheric’ engine in the early 18th century by Thomas Newcomen (1663–1729), who was inspired by the earlier work of Denis Papin (1647–1712) and Thomas Savery (1650–1716). Newcomen was assisted in his experiments by John Calley and, in 1705, they devised the first reliable engine. This invention was brought to practical realization in 1712 when the first working engine was installed at a colliery near Dudley Castle, in Tipton, Staffordshire, UK (Figure 1.2(a)). In Newcomen’s engine, atmospheric pressure drives a piston down into a vacuum, which is created by condensing steam introduced into the cylinder space below; hence, the description ‘atmospheric’ engine. The piston is raised again by the over-balancing weight of the pump rods.

James Watt (1736–1819) subsequently recognized that the ‘atmospheric’ engine is very inefficient – energy is wasted by having to reheat the cylinder after each stroke of the piston. Watt solved this problem by using a separate condenser and driving the engine by the pressure of steam itself. Thus, in 1769, he patented the first real ‘steam’ engine, which offered superior performance in terms of both energy efficiency and economy. Further developments followed, but Watt’s most decisive invention was to make the steam engine rotative, by using a rigid rod to connect the outer end of the beam to a crank below (Figure 1.2(b)). Watt also added a flywheel and devised a ‘governor’ by which the speed of the engine could be kept constant. In contrast to the up and down movement of the reciprocating engines of his day, the rotative motion made possible a much smoother action and a far greater range of industrial applications. The engines were used to pump water from mines, to drive machinery in factories, to dig tunnels, and to thresh corn. By 1800, there were about 2500 rotative steam engines operating in the UK. One-third of these were made by Watt and his partner Matthew Boulton (1728–1809) at the Soho Works in Birmingham, UK. The oldest surviving engine was built in 1785 for the London Brewery of Samuel Whitbread. After providing service for 102 years, the engine was presented in 1887 to the Power House Museum in Sydney, Australia, where it has been restored to a working condition.

It was only a short while before the utility of the steam engine was extended to the propulsion of ships, railway locomotives, and road tractors (Figure 1.3). Engines working on the principle developed by Watt were used to propel boats from as early as the 1780s in both France and the USA. Britain’s first practical steamboat was a tug, the Charlotte Dundas, designed by William Symington (1763–1831) and in use in 1802 on the Forth–Clyde canal. The world’s first steam-powered factory, the Blockmills, was opened in 1802 in Portsmouth Dockyard, UK, to mass-produce pulley blocks for sailing ships. Meanwhile, in early 1804, Richard Trevithick (1771–1833) produced the first steam engine to run successfully on rails; on 21st February 1804, it hauled 10 tonnnes of iron, 70 passengers and 5 wagons at an ‘easy’ 4 mph on a 9-mile journey from the ironworks in Pen-y-Darren, South Wales to the Merthyr–Cardiff Canal. Unfortunately, the engine proved too heavy for the rails, and the era of the practical steam locomotive began in 1813 with Puffing Billy, which was designed by William Hedley (1779–1843) and was the first to run on smooth rails, instead of the previous rack rails. By the early 19th century, steam was also replacing water to power cotton mills (see Chapter 5) and The Times newspaper was printed in London on a steam press as early as 1814. Thus, such engines turned steam into a universal source of power and heralded the beginning of the fossil-fuel age. By the end of the 19th century, there were steam-driven cars in London, Paris, and New York as well as lorries and trams. These competed with electric vehicles and petrol-driven vehicles. Eventually, the internal-combustion engine proved superior (see below) and steam vehicles were mostly phased out, although their use in agriculture continued for at least another 20 years.

Coal

Coal was the first fossil fuel to be exploited to produce power. Previously, wood and coal had been used principally for space heating and cooking and, in the form of charcoal and coke, for metallurgical purposes (e.g. in the smelting and casting of iron). Later, in the 19th century, the pyrolysis of coal yielded coal gas (‘town gas’), which was distributed in cities for lighting lamps and cooking, and coal tar, which was the early raw material for the organic chemicals industry (explosives, dyes, drugs, etc.). As recently as 1937, coal accounted for three-quarters of energy consumption world wide through its use as a fuel for space heating, cooking, industrial processes, and transportation (steam trains and ships).

Petroleum

In 1855, Benjamin Silliman (1816–1885), chemistry professor at Yale University in the USA, investigated the properties of crude oil and predicted that 90% of its contents could be distilled into saleable products (Figure 1.4(a)). Following this epochal discovery, the Seneca Oil Company was founded and started to search for oil by the novel method of drilling. Edwin L. Drake (1819–1880), a retired railway conductor, was put in charge of operations (Figure 1.4(b)). With an assistant, he erected an engine-house and derrick on a farm near Titusville, Pennsylvania, and on 27 August 1859 oil began coming to the surface. The extraction of crude oil from the ground was found to be remarkably simple and inexpensive, and large-scale distillation methods were soon developed to yield light and heavy fractions. Hence was born the petroleum (‘oil’) industry, based on the second-major fossil fuel.

The petroleum industry was transformed from a thriving local activity into one of global influence when, in 1876, the four-stroke internal-combustion engine was built by the German engineer, Nikolaus Otto (1832–1891) (Figure 1.5). Otto’s engines ran at slow speeds and it was not until 1885 that a suitable power unit for motor cars (automobiles) became available – the high-speed engine invented by Gottlieb Daimler (1834–1900). Shortly afterwards, in 1892, Rudolf Diesel (1858–1913) introduced the diesel engine. These engines quickly led to the widespread development of the motor car, just over 100 years ago. Moreover, the success of internal-combustion engines operating on petroleum (‘gasoline’) was such that they rapidly replaced the steam engine (an external combustion engine) for almost all other applications although, of course, steam turbines are still used in electricity generation.

It is interesting to note that, at first, there was considerable hesitation and doubt about the wisdom of developing the internal-combustion engine for road vehicles, as is made clear by the following quotation, said to be from the Congressional Record of the USA for 1875.

“A new source of power, which burns a distillate of kerosene called gasoline, has been produced by a Boston engineer. Instead of burning the fuel under a boiler, it is exploded inside the cylinder of an engine. This so-called internal combustion engine may be used under certain conditions to supplement steam engines. Experiments are under way to use an engine to propel a vehicle.

This discovery begins a new era in the history of civilisation. It may some day prove to be more revolutionary in the development of human society than the invention of the wheel, the use of metals, or the steam engine. Never in history has society been confronted with a power so full of potential danger and at the same time so full of promise for the future of man and for the peace of the world.

The dangers are obvious. Stores of gasoline in the hands of the people interested primarily in profit, would constitute afire and explosive hazard of the first rank. Horseless carriages propelled by gasoline engines might attain speeds of 14 or even 20 miles per hour. The menace to our people of vehicles of this type hurtling through our streets and along our roads and poisoning the atmosphere would call for prompt legislative action even if the military and economic implications were not so overwhelming. The Secretary of War has testified before us and has pointed out the destructive effects of such vehicles in battle. Furthermore, our supplies of petroleum, from which gasoline can be extracted only in limited quantities, make it imperative that the defence forces should have first call on the limited supply. Furthermore, the cost of producing it is far beyond the financial capacity of private industry, yet the safety of the nation demands that an adequate supply should be produced. In addition, the development of this new power may displace the use of horses, which would wreck our agriculture.

– the discovery with which we are dealing involves forces of a nature too dangerous to fit into any of our usual concepts.”

Clearly, such fears did not quench a natural human desire to outpace and outdistance the horse-drawn carriage. The issue was finally put to rest in 1908 when Henry Ford (1863–1947) introduced the world’s first mass-produced, low-cost car – the Model T – which became even more affordable when assembly-line production was implemented in 1913 (Figure 1.5). Through such streamlining, the car could be put together in 98 min and sold for only US$ 400.

Just how far the motor car has come in a little more than 100 years is quite remarkable, although on the pollution front we have merely replaced one environmental problem (horse manure) with another (tailpipe emissions). The 20th century saw the widespread adoption of the internal-combustion engine for transport and for power applications. The use of this engine has become so extensive that grave concern has arisen over the pollution it causes in cities, and also over its contribution to global warming through enhancement of the ‘greenhouse effect’, which is attributable in part to the carbon dioxide (CO2) produced by combustion. The greenhouse effect is essentially the trapping of heat in the lower levels of the Earth’s atmosphere. Most of the short-wave and visible radiation from the Sun is transmitted through the atmosphere to the Earth’s surface where it is largely absorbed, while part is re-radiated as longwave infra-red radiation. Because of the anthropogenic build-up of gases such as carbon dioxide, methane, nitrous oxide, and ozone, however, a substantial amount of the long-wave rays are absorbed by these gases and re-radiated back to the Earth’s surface. Therefore, the lower levels of the atmosphere are heated to higher temperatures. In satisfying energy and agricultural needs, humankind has probably increased the amount of carbon dioxide alone by some 30% since the Industrial Revolution. It is widely believed that long-term climatic changes may result from such global warming.

(Continues…)Excerpted from Clean Energy by Ronald M. Dell, David A. J. Rand. Copyright © 2004 The Royal Society of Chemistry. Excerpted by permission of The Royal Society of Chemistry.
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