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of the current cubed. The available hydrokinetic power thus depends on the speed of
the river, ocean, or tidal current. The operation of the hydrokinetic device requires a
minimum current and water depth. As water flows through a turbine or other device,
the kinetic energy of the flowing river, tidal fluctuations, or waves is converted into
electricity by the appropriate converting device.
Hydrokinetic energy is different from hydroelectricity in the fact that it does
not require a change in elevation. Also, unlike traditional hydropower projects,
hydrokinetic energy projects do not require impoundments or diversions of water
[34,61–65] (Bertsch, 2012, pers. comm.). * Instead, these projects harness the power
of moving water in waves, currents, and tidal channels [34,61–65] (Bertsch, 2012,
pers. comm.). † Hydrokinetic technologies can thus be distinguished based on these
three major sources for harnessing hydrokinetic energy. Waves, currents, and tidal
channels can be either from oceans, rivers, or inland waterways. Surface wave
energy is generally harnessed near sea or ocean shores while energy from undercurrents is harnessed using technologies installed below the water surface
[34–47,61–65] (Bertsch, 2012, pers. comm.; Dixon et al., 2008, pers. comm.). ‡,§
Tidal power is harnessed by new tidal power-harnessing technologies, such as tidal
barrage, tidal lagoons, and new axial or cross-flow turbine technologies [53,58].
While hydrokinetic energy can be obtained in a number of different ways, capturing
the energy contained in near and offshore waves is thought to have the greatest energy
production potential among various options. The rise and fall of ocean waves is driven
by winds and influenced by oceanic geology. The extraction of only 15% of the energy
in coastal waves would generate as much electricity as we currently produce in conventional hydroelectric dams [36–40] (Bertsch, 2012, pers. comm.; Dixon et al., 2008,
pers. comm.). ¶ Much of this wave potential is found along our Pacific coast, near big
cities and towns. Besides waves, ocean tides hold promise as an energy resource. Each
change in the tide creates a current, called tidal stream. Regular tidal streams have
the potential to provide a reliable new source of electricity without building dams and
barrages. Ocean currents, such as Gulf stream, also offer hydrokinetic energy. These
result from winds and equatorial solar heating. Free flowing rivers (without dams) and
constructed waterways such as irrigation canals also allow the use of hydrokinetic
* Bertsch, D.J., Juris Doctoral candidate, The University of South Dakota School of Law, 2011; Congress
defined hydrokinetic energy as “electrical energy from waves, tides, and currents in oceans, estuaries, and tidal areas; free flowing water in rivers, lakes, and streams, or man-made channels; and differentials in ocean temperature (ocean thermal energy conversion),” The Energy Independence and
Security Act of 2007, 42 USC §17211 (2006).
† Ibid.
‡ Hydrokinetic energy was included as an eligible renewable energy resource by the Energy Policy Act
of 2005. Various funding authorizations for research and development were also included in this Act as
well as the Energy Independence and Security Act of 2007.
§ Bertsch, D.J., Juris Doctoral candidate, The University of South Dakota School of Law, 2011; Congress
defined hydrokinetic energy as “electrical energy from waves, tides, and currents in oceans, estuaries, and tidal areas; free flowing water in rivers, lakes, and streams, or man-made channels; and differentials in ocean temperature (ocean thermal energy conversion),” The Energy Independence and
Security Act of 2007, 42 USC §17211 (2006).
¶ Hydrokinetic energy was included as an eligible renewable energy resource by the Energy Policy Act
of 2005. Various funding authorizations for research and development were also included in this Act as
well as the Energy Independence and Security Act of 2007.