It is perhaps trite to observe that the laws of science that determine technical feasibility are immutable, whereas engineering design and manufacturing costs vary from place to place and from time to time. Thus, many goods that formerly were made in developed countries are now produced in lower cost, developing nations. Technical feasibility is, however, the sine qua non of any proposed new technology. Although outline costings are needed to determine whether a project promises to be economic, detailed manufacturing costs (with extrapolation to high – volume production) can only be ascertained after technical feasibility has been established and a prototype built. A technology that is too expensive for a particular application in a given nation at one point in time may be acceptable for a different application, or in a different place, or at a different time. This is one of the key problems facing anyone who attempts to predict the future prospects for technology on a global basis, and the task is complicated further by the need to factor in sociological and other considerations. Inevitably, therefore, some of the abovegeneralized predictions will not apply to specific applications in certain countries. A good example is Iceland or Brazil, where an abundance of cheap hydroelectric power might favor the production of hydrogen by electrolysis. Other forecasts will point in the right direction, but the timing will be wrong, as mentioned at the start of this chapter. Even so, we hope to have provided the reader with food for thought and stimulated some debate and discussion concerning energy futures.
Looking further ahead to 2050, the crystal ball becomes even more cloudy. Nevertheless, the lead-times for new energy technologies are such that it is necessary to take a long-term strategic view. The UK government has accepted this and stated that, by 2050, the country will need to have a clean and secure supply of energy that does not rely too heavily on fossil fuels. In 2001, it commissioned a comprehensive energy review to which 400 different organizations and individuals submitted evidence. Each of these had different, and often conflicting, viewpoints as to the future. Some favored an expansion of nuclear power as the only realistic alternative to fossil fuels and emphasized the importance of following this course soon, before all the expertise and trained staff are lost. Others took a diametrically opposed view and advocated the phasing out nuclear power permanently while vigorously developing all forms of renewable energy. Almost all parties accepted the need for a review of energy policy and agreed that tackling concerns over the security of the nation’s energy supply and the environmental impact of greenhouse gases would necessitate changes to the energy-supply infrastructure. The area of disagreement was over the exact form that these changes should take. As might be expected, the general conclusion of the review was that options should be kept open and that the UK should spend more on energy research and development programs. As a working strategy, a good target model for electricity generation in the UK might be 30% coal-based, 30% gas-based, 30% nuclear, and 10% renewables. This would ensure that the nation had a diverse and secure base for its electricity supply.
In other countries, the situation may be quite different. France, for example, has little fossil fuel and is firmly committed to its nuclear program. Germany has plenty of coal, but little gas of its own. The Netherlands and Denmark have good wind resources and are therefore enthusiastic about renewables. Outside of Europe, the USA has both coal and gas in copious amounts, so that there is little incentive to reinvigorate its nuclear programme. Japan has almost no indigenous fuel and is orientated towards nuclear technology and the importing of liquefied natural gas. Australia, like USA, is rich in both coal and natural gas. Each country has to look to its own position to optimize its electricity generation. This makes for difficulties in global forecasting, especially in meeting emission targets for greenhouse gases. In those countries where electricity generation is state-controlled, it is at least possible for the government to exert some influence over the fuels used. On the other hand, in countries such as the UK and the USA where a free and competitive market exists in electricity generation, the State has comparatively little control except through legislation or subsidies. Liberalized electricity markets are hardly compatible with government energy planning.
One general conclusion can be drawn from this discussion of the developing energy scene to 2020 – there will be no overall shortage of fossil fuels. The world has ample reserves of oil and gas for the present and these are widely distributed, although still with a preponderance in the Middle East. Other fossil fuels (coals, tar sands, asphalts, oil shales) are even more widely distributed, but their extraction and utilization impose technical and environmental problems. Moreover, barring political upsets or the imposition of a high carbon tax, fuels should remain comparatively cheap with modest increases in price above inflation. This will define a cost base against which renewable energy has to compete for business in most situations. The comparatively low cost of fossil fuels does nothing to address the greenhouse gas issue and there appears to be no easy answer to this problem. High carbon taxes, such as might make an impact, would be disruptive to the world economy and would be politically unacceptable. Unless and until the causative relationship between greenhouse gas emissions and global warming is established unequivocally and accepted by all, it is unlikely that the world will change dramatically its dependence on fossil fuels. Nevertheless, the time-scale for developing and implementing renewable energy technologies – decades – is such that efforts directed towards this goal should be continued and, moreover, enhanced.
In summary, some of the major energy problems facing the world today are:
• how to reduce greenhouse gas emissions to acceptable levels while there is cheap fossil fuel still available to compete with renewables;
• how to persuade reluctant politicians and the general public of the need for a carbon tax;
• how to develop a practical and economic route for the sequestration of carbon dioxide without its release to the atmosphere;
• how to increase public awareness of the seriousness of the future energy situation and the need to start investing and planning now for a complete break from the present near-total dependence on fossil fuels; this is primarily a sociopolitical matter but does involve technological developments and choices;
• how to raise the huge amounts of capital investment that will be required to bring new sources of natural gas to market, to bum coal more cleanly, to sequester carbon dioxide, to build new nuclear facilities (if that route is chosen) and, in the longer term, to establish an entirely new, sustainable industry based on renewable sources of energy.
Whereas it is encouraging that schools, universities, interest groups and the media are enabling a new generation of young people, worldwide, to gain a greater understanding of environmental and energy issues, the practical difficulties of moving from fossil fuels to renewables remain enormous. The world’s scientists and engineers are striving to develop the required new energy technologies, but in the final analysis politicians, financiers, bankers, industrialists and the general public must act together to establish an economic climate in which sustainable forms of Clean Energy can flourish in competition with traditional fuels.
 Subsequently, it was established that the French engineer Alphonse Beau de Rochas was the true inventor of the four-stroke cycle in 1862 and Otto’s patent was revoked in 1886. In fact, Beau de Rochas never built a working model and it can be said that it was Otto’s later design of the engine that largely enabled the creation of automobiles, powerboats, motorcycles, and even aeroplanes.
 The total energy supply of the world has increased by 66% in 28 years, while that of OECD nations has increased by 42%. The difference represents the faster growth of many developing nations that start from a lower energy base.
• While the production of oil has increased everywhere, the expansion in activity has been fairly modest compared with natural gas, with the result that oil now provides a significantly smaller percentage share of the total energy supply.
• Coal is used mainly to generate electricity and, despite the fact that the industry is using more gas, the overall increase in electricity consumption has resulted in only a small decline in the percentage contribution made by coal to total world energy.
• The production of natural gas has risen appreciably following the discovery and opening up of new fields. Nevertheless, again because of the overall growth in energy demand, the percentage contribution of natural gas has increased only modestly. (Note: since the late nineties, there has been a ‘dash for gas’ in electricity production, using combined-cycle gas turbine
 The term ‘clathrate’ is derived from the Latin ‘clathratus’, which means ‘enclosed by bars’.
 ‘Petrol’ is the UK term for a light hydrocarbon liquid fuel for spark-ignition engines and is a blend of different components obtained by refining crude petroleum (‘oil’). Other terms for such fuel are ‘gas’, ‘gasoline’, and ‘motor spirit’. Diesel engines, which achieve ignition by the heat of compression of the air charge use heavier and less volatile hydrocarbons as fuel.
 200,000 m3 LNG – 90,0001 LNG = 0.11 Mtoe
 Below the lower flammability limit, there is an insufficient percentage of fuel in air to maintain combustion. Above the upper limit, there is too much fuel and insufficient air.
 34 km per litre = 2.94 litres per 100 km = 96 miles per UK gallon = 80 miles per US gallon.
 producer gas:
C + air -> CO + N2
 The equivalent of electrical energy units with other energy units is given in the Appendix.
 CHP generation. Waste heat from the microturbine can be transferred by a heat-exchanger to produce steam or hot water that can be used, for example, to provide central heating in buildings in winter. Thermal hosts are easier to find because the heat produced by a microturbine is so much smaller than that by a large power station.
• Distributed power generation. Hospitals, hotels, factories, farms, etc. can install microturbines on-site to supplement power supplied by the grid. Microturbines can also be used in remote areas where there is no access to electricity.
 Combustion. This is by far the most common practice. Dry wastes are compacted and then combusted to give heat. Combustion technology is well advanced and is widely used for industrial processes, for domestic purposes (hot water and space heating), and for the generation of electricity. Where applicable, the greatest overall efficiency is achieved by operating a combined heat and power scheme – a CHP scheme (see Section 3.4, Chapter 3). Combustion plant is available in a range of sizes from household boilers to 50-MW industrial furnaces.
• Gasification. This involves incomplete combustion in a limited supply of air and in the presence of steam to yield a mixture of combustible gases, mainly carbon monoxide and hydrogen, diluted in nitrogen. The process is similar to
 At first sight, it is surprising that in Table 3.1 the hydro and nuclear contributions to world electricity generation in 2001 are roughly equal, whereas in Table 1.1 the nuclear contribution to total primary energy supply is much larger than that of hydro. The explanation is that in Table 1.1 the nuclear contribution is counted as heat generated and not as electricity, whereas hydroelectric power does not involve a thermal cycle. See Section 3.1, Chapter 3 for further explanation.
 Some studies have also been conducted on ‘convecting’ solar ponds. In one version, the pond is shallow and uses pure water that is enclosed in a large bag with a blackened bottom and plastic or glass glazing on top. This arrangement permits convection but hinders evaporation. After being heated by the sun during the day, the hot water is pumped into a large heat-storage tank at night to minimise heat loss. To date, convecting ponds have met with little practical success.
 The mass moment of inertia provides a measure of an object’s ability to resist rotational speed about a specific axis. It is the sum of all the point masses of a rotating object multiplied by the squares of the respective distances of the masses from the axis of rotation. Thus, a flywheel is more effective when its inertia is larger, i. e. when the mass is located farther from the centre of rotation, e. g. by having a more massive rim or a larger diameter.
 When an electrode is immersed in an electrolyte solution charge separation occurs at the interface and a so-called ‘double-layer’ is formed. The excess charge on the electrode surface is compensated by an accumulation of excess ions of the opposite charge in the solution. The amount of charge is a function of the electrode potential. The double-layer behaves essentially as a capacitor and since charge separation occurs at the molecular level, very high values of capacitance are obtained.
 The concept of using hydrogen had in fact been suggested much earlier in such diverse publications as Jules Verne’s science-fiction novel The Mysterious Island (1874) and J. B.S. Haldane’s paper Daedalus, or, Science and the Future (1923). It is further notable that Haldane proposed the use of wind power to produce hydrogen via electrolysis of water; the gas would be liquefied and stored in vacuum-jacketed reservoirs that would probably be sunk in the ground.
 inertia to change an existing technology, industry, and way of life
• long time-scale for introducing a new energy industry and the large capital investment required
• difficulties of manufacturing, distributing and storing hydrogen on the megatonne scale in a form suitable for transportation applications
• manufacture of hydrogen at a price that competes with natural or synthetic liquid fuels
 removes the need for a precious-metal electrocatalyst, which reduces cost
• allows the reforming of fuels internally, which enables the use of a variety of fuels, simplifies the engineering (especially heat balancing) and reduces the capital cost; it should be noted, however, that whereas SOFCs can operate on gases made from coal, MCFCs are less resistant to impurities from coal such as sulfur and particulates
• provides high tolerance to carbon monoxide poisoning.
On the other hand, there are disadvantages, such as:
• slow start-up (Table 8.3)
• slow response to changing power demands
• the requirement for significant thermal shielding
 Manganese dioxide, used for the positive-electrode material in primary alkaline cells (with zinc as the negative electrode), is not normally regarded as rechargeable. It is possible, however, to design small (2.5 Ah) rechargeable cells of this type using special components. These cells must not be discharged too deeply and must be recharged with a special charger.
 The open-topped design was a natural progression from the horse-drawn tram in which, obviously, it had been important to minimize weight. Moreover, in the UK, the 1870 Tramways Act gave local authorities the right to enforce the compulsory purchase of any routes that ran through their areas for 21 years after the respective routes were first built, and every seven years thereafter. Thus, many tram companies were reluctant to invest in new, closed-topped fleets.
 This is the same principle as used in the familiar charging of an electric toothbrush, wherein there is no direct contact by wire between the electrical supply and the battery. Elimination of the possibility of ‘wet wires’ enhances safety.
 Mention has already been made (under trolleybuses and railway locomotives) of all-electric mains- battery configurations, such as the ‘Duo-Bus’, and of the operational advantages that such hybrids offer. Another all-electric concept, suitable for all types of EV, is the fuel-cell-battery hybrid (see Section 10.5). This combination serves to overcome the limited peak power of the fuel cell and the restricted range of the pure BEV.
 the requirement for compactness, to fit into a very limited space;
• the availability and supply of a suitable fuel;
• intermittent operation;
• fast start-up from cold;
• high cost.
 It is salutary to note that at US$ 20 the cost of a barrel (159 L) of crude oil is of the same order as the retail price of 1 L of whisky – and the latter did not take geological time to mature!
 A companion volume in this series written by J. Aguado and D. Serrano is entitled Feedstock Recycling of Plastic Wastes.