Environmental Engineering Reference
In-Depth Information
Intermediate Depth Waves
As the water becomes shallower, the properties of the waves become increasingly
dominated by water depth. When waves reach shallow water, their properties are
completely governed by the water depth, but in intermediate depths (i.e., between
d
= λ/2π and
d
= λ/4π), the properties of the waves will be influenced by both water
depth
d
and wave period
T
(Phillips, 1977).
Shallow Water Waves
As waves approach the shore, the seabed begins to have an effect on their speed, and
it can be shown that if the water depth
d
is less than a quarter of the wavelength then
the velocity is given by
v
=
d
Group Velocity
As waves propagate, their energy is transported. The energy transport velocity is the
group velocity. The wave energy flux, through a vertical plane of unit width perpen-
dicular to the wave propagation direction, is equal to
P
=
E
×
c
g
where
c
g
is the group velocity (m/s).
W
ave
e
nergy
C
onversion
T
eChnology
Development of modern wave energy dates back to 1799 (Ross, 1995), but the tech-
nology did not receive worldwide attention until the 1970s when an oil crisis occurred
and Stephen Salter published a notable paper about the technology in
Nature
(Salter,
1974). In the early 1980s, after a significant drop in oil prices, technical setbacks,
and a general lack of confidence, progress slowed in the development of wave energy
devices as a commercial source of electrical power. In the late 1990s, awareness of the
depletion of traditional energy resources and the environmental impacts of the large
utilization of fossil fuels significantly increased, thereby facilitating the development
of green energy resources. The development of wave energy technology grew rap-
idly, particularly in oceanic countries such as Ireland, Denmark, Portugal, the United
DID YOU KNOW?
Wave height increases with increases in the following factors:
•
Wind speed
•
Time duration of the wind blowing
•
Fetch
•
Water depth
