Hydroelectric power is another clean alternative, but the number of river systems throughout the world suitable for large-capacity generation is limited. Moreover, construction of large dams to provide large amounts of electricity may cause new environmental destruction. Therefore, large-scale river developments including construction of hydroelectric plants will not be able to fill the blank in energy supply, which might occur in the near future. Nevertheless, any shortage of energy supply will not be allowed for contemporary civilization development. To cope with the energy problem affecting the global environment, utilization of solar energy is being widely studied. Unfortunately, for solar energy, its energy density is too low and its distribution is too wide, and thus its fullest utilization is at present unfeasible. It is estimated that it will take at least a few centuries to be able to fully utilize solar energy as a basic energy. Therefore, it is thought that solar energy will not meet the requirements of the times of energy supply shortage due to the depletion of fossil fuels, which may occur within 50 years at the earliest.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==