A sound energy policy must ensure that the quality of life of the world's people should continue and even improve on the present situation, and that people below this level should be brought up to the level enjoyed in the developing countries. This requires not only the production of sufficient energy but also taking care that the consequences of that energy production do not destroy the amenities of the earth by pollution and climate change. This is what is meant by a sustainable energy policy. Energy production is considered in this section and the problems of pollution and climate change have been discussed in previous chapters.
In order to see whether we have enough energy to supply our future needs it is necessary to evaluate the capacities of the various energy sources and whether they will continue to produce energy in the future. Energy from inexhaustible sources are sustainable, while those that depend on finite amounts of raw material are not. The renewable energy sources considered in Chapter 3 are sustainable, whereas the fossil fuels and nuclear are not. As we cannot foresee the scientific and technological advances that will certainly be made during the present century, it is unrealistic to try to evaluate the situation beyond fifty years from the present. This re-defines sustainability as referring to the next fifty years and not to the infinite future. On this criterion both coal and nuclear become sustainable. This restriction to the next fifty years does not apply to the problems of pollution and climate change.
To see if our lifestyle is sustainable we need to calculate the average total energy needed or habitually used by each person and compare it with that obtainable from sustainable sources. This has been done with great care by MacKay (2008) and the following summarises some of his results. The analysis refers to Britain, as most of the necessary statistics are available; much of it applies to other developed countries. He does not consider the economics of the various sources as he wants to establish the absolute upper limits to the availability of sustainable energy. In practice economic considerations impose severe constraints that greater reduce the available energy.
Considering the energy expenditures in turn, he finds for each person that travel by car uses about 40 kWh/day and travel by air by about 35 kWh/day for each long-distance return flight and about 6 kWh/day for a return short-haul flight. Domestic use averages 14 kWh/day, including cooking, cleaning (washing machines and dishwashers) and cooling (refrigerators and air conditioners). If electric fires are used for heating this uses 24 kWh/day, giving a total domestic use of 38 kWh/day. The lighting of homes, factories and streets requires about 4 kWh/day. Other household appliances (computers, radios, television and phones) use 5 kWh/day, food 12 kWh/day, commercial transport 12 kWh/day and other miscellaneous uses 10 kWh/day, a total of about 80 kWh/day.
The corresponding analysis of the maximum available energy from different sources requires a number of assumptions that can be questioned, but these are chosen deliberately to be on the optimistic side. MacKay then sketches six scenarios with different contributions from the various sources, insisting that they add up to the required total. All but one include nuclear power or coal. The remaining one relies heavily on wind power and requires a hundred lakes or lochs for energy storage. Thus even from the point of view of energy sustainability, without reference to costs, it is hard to see how the renewable sources can meet our needs.
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