As discussed in the earlier chapters, we rely today for a significant part of our energy needs and related hydrocarbon fuels and products primarily on non-renewable fossil fuel sources. In pre-industrial times, as is still the case today in some developing countries, energy supply was based primarily on renewable sources. The power of watermills and windmills was used to grind grain, press oil or to pump water, while wind energy at sea moved ships, and biomass energy sources such as wood and dung warmed us and cooked our food. With industrialization, however, the role of renewable energy in the global energy supply was gradually taken over by fossil fuels - first coal, and later oil and natural gas. During the past two centuries - which is a relatively short time in human history - our energy needs have relied predominantly on fossil fuels. While the reserves of these fossil fuels are still significant, they are nevertheless limited and diminishing, and they cannot sustain our life-style and development in a permanent manner over the centuries to come. Therefore, in order to satisfy our future energy requirements, the use of energy alternatives to fossil fuels - including renewable sources and nuclear energy - must be increasingly relied upon and developed. But this increasing need to produce synthetic hydrocarbons for fuels and materials will also necessitate large amounts of energy, which must be obtained from non-fossil fuel sources. Therefore, it is necessary not only to discuss the availability and feasibility of alternative energy sources and atomic energy upon which we will need to rely in the future, but also to identify new, efficient ways in which to store, transport, dispense and use energy, while highlighting the advantages of the proposed "Methanol Economy"
Unlike fossil fuels, renewable energy is derived from sources that are not subject to depletion, and simply replenish themselves. These include heat and light from the Sun and wind, organic matter, hydropower, tides, waves and geothermal heat from the Earth's crust. Unfortunately, "renewable" does not necessarily mean non-polluting or "green". Renewable energy gained significance, especially in the United States, after the oil crises of the 1970s. The sudden oil shortages, which led to sharp increases in gasoline and electricity prices, shocked those nations which were used to cheap energy and prompted governments to find solutions to become more energy-independent. Steps were taken to restructure the energy industry and to reduce dependence on imported oil, in part by encouraging the development of renewable and alternative energy sources through government incentives and tax credits. In the early 1980s, many of these measures were in place, but by the mid-1980s fossil fuel prices had fallen substantially and ideas of renewable energy sources had faded as the core of attention of energy policies, because of their higher costs. Recently however, European countries with few or no fossil fuel resources, as well as Japan, driven by the desire of energy independence and adopting the Kyoto Protocol that mandates greenhouse gas emission reductions, have begun to invest again intensively in renewable energy sources. The increased use of renewable energy technologies can contribute to meeting, in parts, both environmental and energy security goals. However, as the overall energy needs of mankind are enormous, this cannot alone be considered as the solution, at least for the foreseeable future. Since few of the alternate energy sources depend on combustion to generate heat or electricity, they also offer substantial environmental benefits compared to fossil fuel technologies (vide infra). Renewable energies are typically based on indigenous sources whose supply is not easily disrupted, therefore their development and use also enhances energy security.
There is hope that renewable sources of energy could become a major factor in developing a secure energy supply for the future. In principle, renewables having the advantage of not being based on limited natural resources, have enormous potential. About ten thousand times more energy from the Sun reaches the surface of the Earth than is generated by all of the fossil fuels consumed. Although the large amount of exploitable primary energy is often scattered, it can be converted in many ways to usable heat and power. However, widespread use is faced with numerous challenges, and many forms of renewable energy are not currently economically viable; moreover, there are also technical problems associated with the integration of renewables into existing systems. These energy sources are also often less environmentally friendly than is suggested. Despite popular belief, no form of energy - whether renewable or subject to depletion - is pollutionfree. Some adverse effects occur either during the construction, operation or disposal of generating facilities and fuels:
• Geothermal energy, for example, is not strictly a renewable resource as underground reservoirs become depleted over longer periods, and solid waste and poisonous vapors can also be generated.
• The construction of large hydroelectric plants requires the draining of rivers and submerging of vast areas of land.
• The use of solar energy necessitates the production of photovoltaic solar cells, and the large amounts of energy needed for this may be derived from fossil fuels. This process also often involves the use of hazardous materials such as cadmium and arsenic. The extensive use of solar energy also would involve large areas of land to be covered by light-absorbing panels.
The main obstacle against the massive and widespread use of renewable energy, together with other renewable sources such as wind, solar or geothermal energy, is that of cost when compared to conventional fossil fuels. These renewable processes are relatively capital intensive, and require major investment to capture diffuse energy sources, making them unattractive for the short term. However, in the long term, when the initial investment has been made, the economics of re-newables improves, since operation and maintenance costs are relatively low in comparison with conventional energy sources using fossil fuels, particularly if the latter are subject to unavoidably significant price increases. In recent years, the progressive deregulation of electricity markets in the United States and Europe, resulting in rising competition between energy suppliers, was directed more towards the short term, a cost-minimizing strategy. This made renewable energies appear at a disadvantage. Governmental support, in the form of research funds, incentives, subsidies and tax credits, is therefore essential to develop sustainable and meaningful energy policies. The government must play an essential role in promoting the development and use of renewable energies, which still account today for only for a relatively small part of the overall global energy use.
In 2002, according to the International Energy Agency, renewables accounted for only 13.5% of the total primary energy supply (TPES) of the world (Fig. 8.1). More traditional sources, such as combustible biomass and waste comprised the bulk at 10.8%, with another 2.2% contributed by hydropower. New renewable energy sources for electricity or heat generation, including geothermal, wind and solar, accounted for less than 0.5% of the TPES.
Today, renewable energies are at various stages of development. Some are well established, such as the use of hydropower, steam from geothermal wells, and burning of biomass and waste. Others are newer but actively developed, such as wind power, photovoltaic cells (which convert sunlight directly into electricity), and the conversion of biomass into gaseous or liquid fuels. Still others are only emerging concepts in the research and development stage, as in the case of power production from ocean tides, waves, currents and temperature gradients. Some of the advantages, limitations and possible future of these energy sources are discussed in the subsequent sections.
Figure 8.1 (a) Share of renewables in world production in 2002. (Source: IEA Renewables total primary energy supply (TPES) in 2002. Information 2004.) (b) Share of renewables in world electricity a) b)
Figure 8.1 (a) Share of renewables in world production in 2002. (Source: IEA Renewables total primary energy supply (TPES) in 2002. Information 2004.) (b) Share of renewables in world electricity
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