Solar energy in progress and future research trends
Environmental prospects
It has been stated by Dunn [35] that several problems have arisen from the increased use of energy. For example, oil spillages result from the tanker transportations. Burning of various energy resources has caused global scale carbon dioxide rise due to especially fossil fuels. If the necessary precautions are not considered in the long run, this gas in the atmosphere could exceed the natural levels and may lead to climate change. Another problem is big scale air pollution in large cities, especially, during cold seasons. Use of fossil fuels in automobiles causes exhaust gases that give rise to another sort of air pollution as well as the surface ozone concentration increases, which are dangerous for human health and environment. Air pollution leads to acid rains that cause pollution of surface and groundwater resources, which are the major water supply reservoirs for big cities.
In order to reduce all these unwanted and damagefull effects, it is consciously desirable to shift towards the use of environmentally friendly, clean and renewable energy resources, especially, the solar energy alternatives. It seems that for the next few decades, the use of conventional energy resources such as oil, coal and natural gas will continue, perhaps at reduced rates with the replacement of renewable sources to a certain increasing rate. It is necessary to take the necessary measures and developments toward more exploitation of solar and other renewable energy alternatives
by the advancement in the research and technological progress. Efforts will also be needed in conversion and moving towards a less energy demanding way of life.
Use of energy is not without penalty in that energy exploitation causes many undesirable degradation effects in the environmental surrounding and life. It is, therefore, necessary to reduce the environmental impacts down to a minimum level with the best energy usage. If the energy consumption goes at present level with present energy sources which are mainly of fossil types, then the future prospective cannot be expected as sustainable or without negative impacts. It has been understood by all the nations since about 1970s that the energy usage and types must be changed towards cleaner and environmentally friendly sources so as to reduce both environmental and atmospheric pollutions. Sustainable future development depends in a major scale on the energy sources pollution potential. The criterion of sustainable development can be defined as the development, which meets the needs of the present without compromising the ability of future generations to meet their own needs. Sustainable development within a society demands a sustainable supply of energy in addition to an effective and efficient utilization of energy resources. In this regard, solar energy provides a very potential alternative for future prospective development.
The major environmental problems are classified by Dincer [28] as follows:
1. major environmental accidents,
2. water pollution,
3. maritime pollution,
4. land use and sitting impact,
5. radiation and radioactivity,
6. solid waste disposal,
7. hazardous air pollution,
8. ambiant air quality,
9. acid rain,
10. stratospheric ozone depletion, and finally,
11. global climate change leading to greenhouse effect.
The last three items are the most widely discussed issues all over the world. The main gaseous pollutants and their impacts on the environment are presented in Table 2. Herein, plus and minus signs indicate proportional and inversely proportional effects, whereas ± implies either effects depending on circumstances.
At present, large-scale fossil energy production is cheaper than the available solar energy generation alternatives [18]. However, conventional energy generation technologies based on fossil fuel have reached maturity leaving little room for significant cost reduction. Indeed, current research on these technologies is mainly concerned with pollution abatement (e. g. clean coal technologies or the use of hydrogen) rather than with improving fossil fuel conversion efficiencies, which are nearing their theoretical limits. Similarly, the important progress in energy conservation serves mainly to mitigate the rapid increase in energy demand, but does not contribute directly to reduce the production costs of fossil energy. In contrast, solar technologies still have large potential for improvement, pending appropriate research and development studies. Moreover, the true price of fossil energy must include scarcity and pollution components to allow a valid evaluation of social costs and benefits of alternative energy options.
