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Debate: Tidal energy

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Should tidal energy be a major part of plans to fight global warming?

Background and context

Tidal energy utilizes the flow and energy of the tides and currents to generate electricity. Because the tides and currents are driven largely by the gravitational pull of the moon, tidal energy is actually a form of exploiting lunar gravitational energy. There are different general categories of tidal power, although they both exploit the same basic tidal-lunar forces: tidal stream generators and barage tidal energy.
Tidal stream generators are akin to wind turbine technology. They capture both the incoming and outgoing "stream" energy of tides, similar to how wind turbines capture wind energy. Barage tidal energy is much like dam hydroelectric technology. It involves building a barrage across a bay or an estuary to force tidal water through turbines situated in the barage. The debate surrounding tidal energy is mainly about analyzing the pros and cons of this technology, and comparing them with the pros and cons of the various other "green" energy alternatives such as "clean coal", natural gas, wind energy, solar, geothermal, nuclear, hydroelectricity, and biofuels. The purpose of this debate is to determine whether tidal energy should be a significant part of national and global energy and global warming plans, and whether it should receive government funding and private investments. The debate revolves around numerous questions. For the purpose of fighting global warming, will tidal power deliver a strong return on investment? Is it truly "green"? Are there any significant costs to marine wildlife? What are the economic benefits and costs? Is tidal technology sufficiently developed or is it too new? Is it cheap enough to install and maintain? Will the energy produced provide a good return on investment? What are the specific pros and cons of tidal stream generators and barage tidal energy systems?

See Wikipedia's article on tidal energy for more background.

Contents

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Marine ecosystems: Is tidal energy consistent with preserving marine ecosystems?

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Yes

  • A tidal barrage can safeguard coastlines from storms. Barrages can help protect coastal ecosystems from the devastation of a storm. This protective purpose more than adequately makes-up for any of the minor damage that tidal energy may do to marine ecosystems.
  • Offshore turbines don't hamper the flow of tides. Offshore turbines do not alter the flow of tides as much as barrages can, so have a smaller environmental impact.


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No

  • Tidal energy disrupts marine ecosystems like a dam. Barrages effectively dam estuaries and bays in order to build-up and concentrate water mass into turbines that convert the energy to electricity. Daming a bay or estuary in this way changes tidal flows, which can have significant consequences for aquatic and shoreline ecosystems, including changing the flow-dynamics of an marine ecosystem, disorienting animals that depend on the flow dynamics of an ecosystem, increasing silt build-up, killing marine wildlife (particularly fish populations), and destabilizing ecosystems that depend on that marine wildlife.[1]
  • Tidal energy can impair the natural "flushing" of water ecosystems. Bays and estuaries are always naturally "flushed" or cleansed and replenished by tide-waters flowing in and out. To the extent that tidal energy impairs the natural flows of these tides, it impairs this natural "flushing" mechanism. This can alter and even destroy an ecosystem.
  • Tidal energy can lead to prolonged and undesirable winter icing. Tidal energy can slow the movement of water in a bay or estuary, which reduces the amount of kinetic energy and causes the body of water to freeze-over more often or for longer periods of time. This has consequences for marine ecosystems.


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Global warming: Is tidal energy important in the fight against global warming?

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Yes

  • Tidal energy burns no fossil fuels and releases no emissions. Tidal power derives its power from the ocean tides and currents. Because it does not burn fossil fuels to obtain energy, it emits no greenhouse gases or air-borne pollutants. As such, tidal energy can act as an important substitute for fossil-fuel energy, removing greenhouse-gas polluters from operation.
  • Tidal power can generate massive energy and slash emissions Tidal energy can produce massive quantities of energy. And, because tidal energy is clean, it can replace fossil fuels and substantially reduce greenhouse gas emissions. According to one source, a single tidal barrage can prevent the release of approximately one million tons of CO2 per TWH generated.[2]


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No

The fact that individual tidal energy plants produce so little energy combines unfavorably with the fact that there are very few regions in the world that are suitable for tidal energy. Obviously, this combination means that tidal power's cumulative energy production (and potential) is very small comparatively. If tidal energy is incapable of generating significant quantities of energy, it is unviable as a "clean" substitute for fossil fuels. It will reduce greenhouse emissions by a negligible degree and will have effectively no positive impact in the fight against global warming.


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Economics: Is tidal energy robust and viable economically?

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Yes

  • Tidal power requires no fuel; free energy of the tides. Tidal energy does not require any fuel. Tides rise and fall naturally every day, and so supply a free source of energy. Therefore, once a tidal energy plant is built, the energy extracted from it is virtually free. This compares favorably to coal, petroleum, or nuclear power generation, in which fuel must be drilled for or mined (which takes energy and money), filtered or refined (which takes energy and money), transported (which takes energy and money), and burnt for energy (which has environmental and subsequent economic costs). This means that fossil fuels have a price while tidal energy is a free energy source.
  • Tidal energy has existed and been developed for ages. Tidal energy is one of the oldest forms of energy used by humans. It was used on Spanish, French and British coasts as early as 787 A.D.. Tide mills consisted of a storage pond, filled by the incoming (flood) tide through a sluice and emptied during the outgoing (ebb) tide through a water wheel. The tides turned waterwheels, producing mechanical power to mill grain. Tidal energy's long history testifies to the simplicity of the energy source and also demonstrates that it is a tried and tested renewable energy source, even if its modern designs are younger.
  • Tidal energy is still new; costs will drop over time. Give tidal energy time to develop, and its costs will drop dramatically. Just as solar energy was once seen as economically unviable, but now is viable, tidal energy will become more and more viable over time.


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No

  • Tidal power has a low capacity factor (poor return-on-investment) The net capacity factor of a power plant is the ratio of the actual output of a power plant period over its output if it could operate at the full capacity of the installed generator. Tidal energy has a very low capacity factor because tidal energy production peaks infrequently in the day. This means that a tidal energy plant could have the same turbines and generators as a hydroelectric dam, but produce half the electricity. Because it takes the same amount of money to build and install these generators, the return on investment in tidal energy plants would be about half that of hydroelectric plants.
  • Tidal power generates little return on investment so is unviable Lewis Page of The Register (UK) estimates that the US tidal energy project SeaGen will not recover the costs of its initial investment until the end of its predicted life of 20 years. In other words, there will be virtually no return on investment for SeaGen. Since return-on-investment is a necessary force in incentivizing market investments into an energy facility, SeaGen and other tidal energy plants may be entirely unviable.[3]
  • Tidal energy is new; it will be some time before it is viable. While it is possible that tidal energy will become viable in the future, it is a very young resource compared to other renewables, so cannot be expected to be viable for possibly decades to come. This compares starkly with alternative forms of renewable energy that are viable now. Governments should invest in renewable energy that is viable at this time, not in the uncertain future of tidal energy.


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Consistency: Is tidal energy generation consistent, reliable?

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Yes

  • Tidal energy is predictable and reliable The tides and currents are based on the movement of the moon around the earth, so they are entirely predictable. This makes it possible to precisely predict the daily energy production of tidal energy. This is important because the electric grid must precisely match supply and demand at every moment of the day. Predictability makes it easier to do so. This contrasts starkly with wind-power as well as solar, which depend entirely on unpredictable local weather conditions.


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No

  • Tidal energy production varies with tides; requires stand-by power Tidal energy varies on a daily basis with the movements of the tide. The tide moves fastest in the morning and night and is much slower in between as it shifts directions. This variability means that tidal energy requires a stand-by source of energy. This is generally considered in unappealing trait in an energy resource because it requires complex management and can require the burning of fossil fuels as the stand-by energy source.
  • Tidal energy supply is out of sink with peak energy demand. Tidal power misses peak demand due to the 12.5 hr tides-cycle. Peak demand around the world typically occurs in the middle of the day. Yet, tides flow fastest in the morning and at twilight. This means that tidal power is out of sink with every-day energy demands.


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Abundance/availability: Is tidal energy abundant or are there few good sites?

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Yes

  • Potential energy-production of tidal power is immense "Wave and Tidal Power: Energy from the Seas". Environmental Defense Fund. - "The potential of ocean energy is immense. The Snohomish County Public Utility District north of Seattle, WA, estimates that the tides in just seven areas under consideration for ocean energy development in Puget Sound could provide power for 70,000 homes. In places around the world where waves are big, fast and continuous, ocean energy could be generated 80–90 percent of the time. The Electric Power Research Institute estimates that ocean energy could provide power for up to 10 percent of US households."


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No

  • Very few sites globally are appropriate for tidal energy "Tidal Energy". Unisun.net.: "Similar to other ocean energies, tidal energy has several prerequisites that make it only available in a small number of regions. For a tidal power plant to produce electricity effectively (about 85% efficiency), it requires a basin or a gulf that has a mean tidal amplitude (the differences between spring and neap tide) of 7 meters or above. It is also desirable to have semi-diurnal tides where there are two high and low tides everyday. Tides out in the ocean have maximum amplitude of about one meter. As you move closer to shore, this can increase to as high as 12 or more. This can depend on local features such as shelving or funneling meaning the tidal range can vary considerably along any given coastline. This can mean that a lot of places just aren't suitable. When planning the location major consideration has to be given to see whether the tides ar high enough and if there is a suitable place for building the site."


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Installation: Is the installation of tidal energy difficult?

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Yes

  • Tidal power installation is easier than dams and nuclear plants. While it may not be easy or "cheap" to install tidal power turbines and barrages it is certainly much easier than installing massive hydroelectric dams and nuclear plants.
  • Tidal turbines can be built into existing bridges. These generators are easy to install because it does not require planting any new beams into the sea floor.
  • Offshore turbines are not too expensive to build. Offshore turbines are very simple. Vertical-standing ones are much like wind-turbines. Really, it is just a post stuck into the sea floor at a depth of around 10 to 30 meters, with a turbine and generator attached to it near the top. This is not difficult from an engineering stand-point, so should not remain very expensive in the long run.


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No

  • Installing tidal energy plants is difficult and expensive. The installation of tidal energy turbines and barrages requires special barges that are not cheap to manufacture. This is related to the fact that installing anything deep underwater is difficult and, thus, expensive. The problem is compounded by the fact that installation must take place while the tides are moving. This is not an easy engineering feet, particularly when some tidal energy units are planted in water that is 30-meters deep.



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Maintenance: Are tidal energy plants easy and cheap to maintain?

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Yes

  • Tidal energy systems are simple, so easy to maintain. Tidal energy technologies have been around for centuries because it is so simple. Barage systems are as simple and easy to maintain as a dam. Turbine systems involve propellers rotating around an axis, which is attached to a generator. The simplicity of this design makes it possible to design strong tidal turbines that require very few tidal repairs. Therefore, even if underwater repairs are expensive, they are so infrequent that the costs are negligible in the long-run.
  • Tidal power plants have long lives of operation. The economic life of a tidal plant is very long compared to many other energy resources. According to one source, a plant is expected to be in production for 75 to 100 years, in comparison with the 35 years of a conventional fossil fuel plant.[4]


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No

  • Repairing tidal energy is difficult and expensive. Repairing tidal energy systems underwater is very challenging and expensive, as is repairing anything underwater. The problem is that it requires a combination of divers and submarine equipment, both of which are expensive. This is all compounded by the fact that proposed tidal energy plants are generally located in environments with the most violent tides. The mass of water moving via tides can easily damage and corrode tidal energy systems.
  • Retrieving disintegrated tidal energy parts is problematic The disintegration of some tidal energy turbines and barages is unavoidable. The problem surrounds recovering the lost parts. While disintegrated wind turbines (a common problem) can be easily retrieved on land, it is nearly impossible to recover disintegrated tidal energy parts from the sea. Therefore, these parts may float around as a hazard to both boats and marine wildlife.
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Recreation: Is Tidal energy consistent with recreational demands on water-ways?

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Yes

  • Forms of tidal energy can be adjusted to limit impact. There are many different forms of tidal energy. Underwater turbines and barage systems are the most common. It is possible to adjust the type of tidal energy in certain areas to suit any recreational needs. The location of a tidal energy plant can also be adjusted to avoid impeding on any major recreational activities.
  • Most tidal energy sites have no recreational activities. One of the primary locations under consideration for tidal energy, for instance, is the NorthWest coast. On long-stretches of this coast, there is virtually no significant recreational activity in the water itself.


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No

  • Tidal energy systems can disrupt recreational activities. Boating, fishing, and swimming activities occur on many coastlines and estuaries. Tidal energy systems can disrupt these activities. A barage is particularly invasive on reactional activities, as it creates a wall and sometimes even isolates a large portions of a body of water. Tidal energy turbines would be particularly invasive on fishing activities.


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Aesthetics: Is tidal energy aesthetic?

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Yes

  • Tidal energy turbines are hidden beneath the water. Tidal energy turbines are hidden beneath the water, invisible to the human eye. This is an advantage of tidal turbines over tidal barages, which are visible above water and have the appearance of a dam.
  • The "cleanness" of tidal energy is beautiful. The beauty of an object is in the eyes of the beholder. Those that recognize the function of tidal energy in protecting the environment and fighting global warming will see tidal energy plants as a beautiful thing. Those that don't see this beauty should reassess their views regarding their relationship to the environment.


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No

  • Tidal energy barages look about as bad as dams. Barages have the look of dams. They are massive structures that intrude on the natural beauty of rivers. This is ugly.
  • Environmental impact of barages is ugly. Barages are fairly massive objects, like Dams, that obstruct the natural flow of water and can, subsequently, have harmful environmental impacts. These effects can be very ugly, causing frustration among locals and possibly reduced property values and tourism.


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Turbines: Are tidal turbine stream generators a good idea?

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Yes

  • Offshore turbines spin slowly, don't jeopardize marine life. There is a common concern surrounding wind turbines that they kill (too many) birds. This concern also exists in regards to the effect of tidal turbines on marine life. Yet, the much slower spinning-speed of water turbines does not significantly jeopardize marine wild-life.


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No

  • Tidal turbines can kill marine wildlife. The spinning blades of tidal turbines are capable of killing some wildlife, particularly larger fish and marine mammals.


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Barages: Are tidal barages a good idea?

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Yes

  • Tidal barages produce more energy than other forms of tidal. Barage tidal energy acts in a similar way as hydro-electric dams, stopping massive quantities of water and using the mass and pressure to spin turbines that generate electricity. It is capable of producing more energy than tidal turbines.
  • A tidal barrage can safeguard coastlines from storms. This can help protect coastal ecosystems from the devestation of a storm. This protective purpose more than adequately makes-up for any of the minor damage that tidal energy may do to marine ecosystems.


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No

  • Tidal barages disrupt marine ecosystems like dams do. Changing tidal flows by damming a bay or estuary could result in negative impacts on aquatic and shoreline ecosystems. One of the impacts is that it can reduce the tidal flow by up to 15 centemeters, according to some sources.[5]
  • Tidal barage energy can impair the natural "flushing" of water ecosystems. Bays and estuaries are always naturally "flushed" or cleansed and replenished by tide-waters flowing in and out. To the extent that tidal energy impairs the natural flows of these tides, it impairs this natural "flushing" mechanism. Tampering with this mechanism can have unpredictable and even disastrous consequences for an ecosystem.


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Vs. nuclear: Should tidal energy substitute for nuclear energy?

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Yes

  • Tidal energy could replace unsafe/polluting nuclear energy. There are many concerns surrounding nuclear energy, regarding the potential radiation hazards for nuclear-plant workers and locals as well as for the environment when radioactive nuclear waste is buried. There is pressure to continue to build nuclear plants because they can supply a significant amount of electricity and do so without producing greenhouse gases like coal. Yet, the above concerns remain. Tidal energy can act to replace nuclear-electricity generation, and so by-pass these concerns.



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No

  • Nuclear energy should be an important part of combating global warming. While there may still be some concerns regarding the safety and local environmental impact of nuclear energy, nuclear energy releases 0-emissions and so is an important part of the fight against global warming. It should be pushed forward; tidal energy should not "replace" it.
  • Tidal energy can't produce enough electricity to replace nuclear. Tidal energy is incapable of producing electricity on a large, global scale, due to its low capacity factor (0-production when tides aren't moving) and because it is viable in a very limited number of sites. Nuclear energy, on the other hand, is capable of scaling to produce massive quantities of electricity. It currently supplies around 20% of all electricity demand in the United States, and could supply the majority of electricity demand if more nuclear energy plants were constructed in the United States. For these reason, tidal energy is incapable of replacing nuclear energy as a fuel source.


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Pro/con resources

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Yes


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No

See also

External links and resources

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