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Power and Energy Directly from Water
and marine mammals, ice and other debris, as well as river and ocean bed stability
can significantly affect the performance of hydrokinetic energy machinery [34–65]
(Bertsch, 2012, pers. comm.). *,†
13.3.3 hydrokineTiC PoWer deviCeS
While tidal/river/ocean current energy and wave energy converters (WECs) are
sometimes categorized separately [51–60], both types of technology can be categorized under the general term “hydrokinetic power devices.” Another marine energy
technology, OTEC, is covered later in detail. It is mostly applicable to tropical
areas [72–77].
Modern ocean wave energy conversion machines use new technology that is
designed to operate in high amplitude waves, and modern tidal/river/ocean current
hydrokinetic machines use new technology that is designed to operate in fast currents. Both of these emerging technologies have the potential to provide significant
amounts of affordable power with low environmental impact. While each individual
device can give a limited amount of power, often, a farm of devices are used to
increase the total power generation capacity. All designs require careful thoughts
and implementations of their deployment and operation.
The devices that generate energy from waves and currents are called hydrokinetic
energy conversion devices. Hydrokinetic energy devices typically use vertical- or
horizontal-axis turbines similar to those developed for wind generation or old water
mills. Since water is approximately 850 times denser than air, the amount of energy
generated by a hydrokinetic device is much greater than that produced by a wind
turbine of equal diameter. In addition, river and tidal flow do not fluctuate as dramatically from moment to moment as wind does. This predictability benefit is particularly true for tidal energy. It can be predicted years in advance and is not affected
by precipitation or evaporation.
Hydrokinetic energy conversion devices are broken into two categories: WECs
and rotating devices [50,51]. WECs are generally installed at the surface of the water,
while rotating devices are generally installed beneath the water surface. While
the industry is still at the growing stage, there are a number of cost-effective and
environmentally acceptable devices being developed, constructed, and installed.
Some of these devices (and their modifications) have been tested at the pilot- and
commercial-scale levels. The industry wants to build “wave parks” and turbine
arrays that are capable of delivering clean and renewable electricity from different
forms of wave energy.
* 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).
Power and Energy Directly from Water
and marine mammals, ice and other debris, as well as river and ocean bed stability
can significantly affect the performance of hydrokinetic energy machinery [34–65]
(Bertsch, 2012, pers. comm.). *,†
13.3.3 hydrokineTiC PoWer deviCeS
While tidal/river/ocean current energy and wave energy converters (WECs) are
sometimes categorized separately [51–60], both types of technology can be categorized under the general term “hydrokinetic power devices.” Another marine energy
technology, OTEC, is covered later in detail. It is mostly applicable to tropical
areas [72–77].
Modern ocean wave energy conversion machines use new technology that is
designed to operate in high amplitude waves, and modern tidal/river/ocean current
hydrokinetic machines use new technology that is designed to operate in fast currents. Both of these emerging technologies have the potential to provide significant
amounts of affordable power with low environmental impact. While each individual
device can give a limited amount of power, often, a farm of devices are used to
increase the total power generation capacity. All designs require careful thoughts
and implementations of their deployment and operation.
The devices that generate energy from waves and currents are called hydrokinetic
energy conversion devices. Hydrokinetic energy devices typically use vertical- or
horizontal-axis turbines similar to those developed for wind generation or old water
mills. Since water is approximately 850 times denser than air, the amount of energy
generated by a hydrokinetic device is much greater than that produced by a wind
turbine of equal diameter. In addition, river and tidal flow do not fluctuate as dramatically from moment to moment as wind does. This predictability benefit is particularly true for tidal energy. It can be predicted years in advance and is not affected
by precipitation or evaporation.
Hydrokinetic energy conversion devices are broken into two categories: WECs
and rotating devices [50,51]. WECs are generally installed at the surface of the water,
while rotating devices are generally installed beneath the water surface. While
the industry is still at the growing stage, there are a number of cost-effective and
environmentally acceptable devices being developed, constructed, and installed.
Some of these devices (and their modifications) have been tested at the pilot- and
commercial-scale levels. The industry wants to build “wave parks” and turbine
arrays that are capable of delivering clean and renewable electricity from different
forms of wave energy.
* 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).