A Feasibility Study - Aaltodoc - Aalto-yliopisto

LITERATURE REVIEW
2 Ocean Waves
Waves have interested humanity for ages and when visiting the coast, one is typically
awestruck by the simple rolling of waves onto shore. Waves and oceans have also been
important for humanity, first with fishing and shipping, but currently with energy
production possibilities. The energy content in waves is staggering and the world –
desperate craving for clean and renewable energy – is soon ready to embrace it.
This Chapter first introduces waves as a physical phenomenon, describes their
characteristics and explains how physical laws control their behavior. Secondly the
numerous different techniques for the utilization of wave power are described. Thirdly
this Chapter demonstrates the huge energy resource in waves and that wave power
could – and most likely will – play an important role in the future in supplying
humanity with renewable energy.
2.1 Physics of ocean waves
Waves are a renewable and an abundant source of energy (Folley, Whittaker & Henry
2007). They can be considered as an indirect form of solar energy, as they are originated
by wind, which in turn is created by the uneven distribution of solar radiation. The
interactions of wind and the surface of the water, which result in the formation of
waves, are complex, but three key factors affecting the size of the wave can be named:
the wind speed, its duration and the distance over which the wind affects the wave, i.e.
the fetch (Boyle 2004).
Figure 1. A simple sinusoidal wave. Adapted from (WMO 1998).
It can be stated that “The surface waves are sets of unbroken sine waves…” (Twidell,
Weir 2006, p. 402). Even though sine wave is a simple mathematical function, modeling
actual waves is very difficult task. This is due to the fact that actual waves are a sum of
nearly infinite sine waves and it is next to impossible to know the composition of each
individual wave. Figure 1 has an example of a single sine wave with some of its
common characteristics:
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