ABSTRACT
This chapter discusses state of knowledge and experience with wind, wave, and tidal energy, and presents an estimate of the magnitude, in energy terms, of possible future use. Winds, waves, and tides are of interest as possible future energy sources primarily because of their nondepletable character and their favorable environmental aspect, in comparison with energy technologies presently in use. The vast majority of large wind-electric generators constructed in the past have been two-blade or three-blade propellers. The degree of power concentration effected by waves is quite substantial. The mechanical energy in waves takes different forms. To harness the tides for power, two physical conditions are necessary. First, the tidal amplitude must be large–several meters at the very least. Second, the coastal topography must be such as to allow the impoundment of a substantial amount of water with a manageable volume of civil works.
