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Power and Energy Directly from Water
vanes turning within a fixed outer ring [35,47–51,53,55–60]. Many other designs for
rotating devices are presented in an excellent review by Ortega-Achury et al. [91].
One commercial design—“the open-center turbine”—is designed to be deployed
directly on the seabed, and its installation is silent and invisible from the surface. It
is located at depth and presents no navigational hazard. Farms of open-center turbines can provide a significant and undetectable supply of clean, predictable, renewable power. More details of this type of turbine are given in “OpenHydro” company
website.
Fast currents, like those in the Missouri and Mississippi rivers, in tidal channels
such as the Puget Sound, or in ocean currents such as the Gulf Stream off Florida,
have enough power to turn large rotating devices. Since the power from a hydrokinetic machine is proportional to the cube of the current velocity, faster currents are
better, and sites with current velocities reaching 3 m/s are desirable.
13.3.3.4 devices to harness tidal Power
Harnessing tidal power has traditionally suffered from high cost and limited availability of sites, with sufficiently high tidal ranges or flow velocities. The topic has,
however, gained more attention due to new technological developments in design
such as dynamic tidal power (DTP) or tidal lagoons and new turbine technology such
as new axial flow and cross-flow turbines. Unlike in wave power, in tidal power, both
the kinetic energy of the moving water and the potential energy difference between
high and low tides can be used.
Tidal stream generator makes use of the kinetic energy of the moving water to
power turbines just as wind turbines use wind to power turbines. Some tidal generators can be built in the structures of existing bridges. The world’s first commercial
scale and grid-connected tidal stream generator—SeaGen—was built in Strangford
Lough [92]. This power generator is illustrated in Figure 13.7.
Tidal barrage makes use of the potential energy difference in height between
high and low tides. Tidal barrage technology takes advantage of predictable ocean
tides. A barrage, or dam across an estuary or tidal channel, traps tidal flows and
then releases them through turbines as tides fall [47–60]. When using tidal barrages
to generate power, the potential energy from a tide is seized through the strategic
placement of specialized dams. When the sea level rises and the tide begins to come
in, the temporary increase in tidal power is channeled into a large basin behind the
dam, holding a large amount of potential energy. With the receding tide, this energy
is then converted into mechanical energy as the water is released through large
turbines that create electrical power through the use of generators [93]. Barrages are
essentially dams across the full width of a tidal channel.
DTP device exploits an interaction between potential and kinetic energies in tidal
flows. These are very long dams (about 20–30 miles long) built from coasts straight
out into the sea or ocean, without enclosing an area. High and low tidal phase differences are introduced across the dam, leading to a significant water-level differential
in shallow coastal seas. These types of tidal currents are often found in the countries
like the United Kingdom, China, and Korea. Besides tidal power, tidal lagoons are
being rapidly developed and deployed.
Power and Energy Directly from Water
vanes turning within a fixed outer ring [35,47–51,53,55–60]. Many other designs for
rotating devices are presented in an excellent review by Ortega-Achury et al. [91].
One commercial design—“the open-center turbine”—is designed to be deployed
directly on the seabed, and its installation is silent and invisible from the surface. It
is located at depth and presents no navigational hazard. Farms of open-center turbines can provide a significant and undetectable supply of clean, predictable, renewable power. More details of this type of turbine are given in “OpenHydro” company
website.
Fast currents, like those in the Missouri and Mississippi rivers, in tidal channels
such as the Puget Sound, or in ocean currents such as the Gulf Stream off Florida,
have enough power to turn large rotating devices. Since the power from a hydrokinetic machine is proportional to the cube of the current velocity, faster currents are
better, and sites with current velocities reaching 3 m/s are desirable.
13.3.3.4 devices to harness tidal Power
Harnessing tidal power has traditionally suffered from high cost and limited availability of sites, with sufficiently high tidal ranges or flow velocities. The topic has,
however, gained more attention due to new technological developments in design
such as dynamic tidal power (DTP) or tidal lagoons and new turbine technology such
as new axial flow and cross-flow turbines. Unlike in wave power, in tidal power, both
the kinetic energy of the moving water and the potential energy difference between
high and low tides can be used.
Tidal stream generator makes use of the kinetic energy of the moving water to
power turbines just as wind turbines use wind to power turbines. Some tidal generators can be built in the structures of existing bridges. The world’s first commercial
scale and grid-connected tidal stream generator—SeaGen—was built in Strangford
Lough [92]. This power generator is illustrated in Figure 13.7.
Tidal barrage makes use of the potential energy difference in height between
high and low tides. Tidal barrage technology takes advantage of predictable ocean
tides. A barrage, or dam across an estuary or tidal channel, traps tidal flows and
then releases them through turbines as tides fall [47–60]. When using tidal barrages
to generate power, the potential energy from a tide is seized through the strategic
placement of specialized dams. When the sea level rises and the tide begins to come
in, the temporary increase in tidal power is channeled into a large basin behind the
dam, holding a large amount of potential energy. With the receding tide, this energy
is then converted into mechanical energy as the water is released through large
turbines that create electrical power through the use of generators [93]. Barrages are
essentially dams across the full width of a tidal channel.
DTP device exploits an interaction between potential and kinetic energies in tidal
flows. These are very long dams (about 20–30 miles long) built from coasts straight
out into the sea or ocean, without enclosing an area. High and low tidal phase differences are introduced across the dam, leading to a significant water-level differential
in shallow coastal seas. These types of tidal currents are often found in the countries
like the United Kingdom, China, and Korea. Besides tidal power, tidal lagoons are
being rapidly developed and deployed.