58 TILDAL POWER – coolmyplanet

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[mk_padding_divider size=”80″][mk_fancy_title tag_name=”h2″ style=”false” color=”#393836″ size=”48″ font_weight=”300″ margin_top=”0″ margin_bottom=”25″ font_family=”none” align=”center” el_class=”mk-letter-spacing” font_style=”inhert” txt_transform=”capitalize” letter_spacing=”1″]Tildal Power[/mk_fancy_title][mk_fancy_title tag_name=”h2″ style=”false” color=”#5dc677″ size=”20″ font_weight=”normal” margin_top=”15″ margin_bottom=”40″ font_family=”none” align=”center” el_class=”mk-letter-spacing mk-padding-sub-heading ” font_style=”normal” letter_spacing=”2″]DEFINITION & TYPES OF STRATEGIES[/mk_fancy_title]

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Tidal power converts the energy of tides into useful power (normally electrical power). A tide is the periodic variation in the surface level of the oceans and other water bodies caused by gravitational attraction of the moon and Sun.

During the year, the amplitude of the tides varies depending on:

The position of the Earth, the Moon and Sun: spring tides occur when the Sun, Moon and Earth are aligned; neap tides occur when the gravitational forces of the Earth-Moon axis are at 90 degrees to the Earth-Sun axis.

The shape of the ocean bed, the shoreline geometry and Coriolis acceleration.

Amphidromic points are places of the tidal system where the tidal range is roughly zero. Even in these points tidal currents will flow with high velocity as the water surface on either side of the amphidromic point is at different levels due to Coriolis effect and interference within oceanic basins, seas and bays, creating a tidal wave pattern, which rotates around the amphidromic point. The locations with the largest tidal ranges are resonant estuaries.The world’s theoretical tidal power potential (tidal range plus tidal currents) is in the range of 3 TW, with 1 TW located in relatively shallow waters. Note that only a fraction of the theoretical potential is likely to be exploited

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Tidal Currents are the ocean water mass response to tidal range. They are generated by horizontal movements of water. These movements are modified by seabed bathymetry. Tidal current flow result from the rise and fall of the tide; their timing and magnitude are highly predictable.The main difference between the turbines used in tidal and river (or ocean) is that currents flows are unidirectional, whilst tidal currents reverse ﬂow direction. For this reason, tidal current turbines have been designed to generate in both directions. The advantage of using tidal energy is that tides are more predictable than other renewable energies. A greatest use in tidal power in a future is promising since enhanced designs and turbine technologies are being developed.

There are variations of the height of a tide over a day.

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[mk_fancy_title tag_name=”h2″ style=”false” color=”#393836″ size=”35″ font_weight=”300″ margin_top=”0″ margin_bottom=”25″ font_family=”none” align=”center” el_class=”mk-letter-spacing” font_style=”inhert” txt_transform=”capitalize” letter_spacing=”1″]Types[/mk_fancy_title][mk_fancy_title tag_name=”h2″ style=”false” color=”#393836″ size=”20″ font_weight=”300″ margin_top=”0″ margin_bottom=”25″ font_family=”none” align=”center” el_class=”mk-letter-spacing” font_style=”inhert” txt_transform=”capitalize” letter_spacing=”1″ animation=”bottom-to-top”]Tildal stream generator[/mk_fancy_title][mk_padding_divider size=”50″]

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Tidal stream generators are devices that use the kinetic energy of moving water to power turbines. These generators are the least ecologically damaging among the forms of tidal power generation. The suitable places to locate these systems are areas with fast currents where natural flows are concentrated between obstructions (at the entrances to bays and rivers, around rocky points, headlands, or between islands).

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There are three kinds of tidal stream generators:

[mk_padding_divider size=”10″][mk_fancy_title tag_name=”h2″ style=”false” color=”#5dc677″ size=”20″ font_weight=”normal” margin_top=”15″ margin_bottom=”40″ font_family=”none” align=”center” el_class=”mk-letter-spacing mk-padding-sub-heading ” font_style=”normal” letter_spacing=”2″ animation=”left-to-right”]AXIAL TURBINES[/mk_fancy_title]

Axial turbines have rotary blades with axis parallel to the flow direction.

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These turbines can be deployed either vertically or horizontally. Most water turbines have axial or radial flows; in a cross-flow turbine the water passes through the turbine transversely, or across the turbine blades. Cross-flow turbines are mostly used in mini and micro hydropower units of less than two thousand kW and with heads less than 200 m.

Advantages:

Low price.

Good regulation.

Well-suited to unattended electricity production.

Simple construction makes it easier to maintain than other turbine types; only two bearings must be maintained, and there are only three rotating element.

It can often clean itself.

Although the turbine’s efficiency is somewhat lower, it is more reliable than other types.

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The shrouded turbine is used to increase the flow rate. The shrouded tidal turbine is an emerging tidal stream technology that has a turbine enclosed in a venturi shaped shroud or duct, producing a sub atmosphere of low pressure behind the turbine. They can operate in shallower slower moving water with a smaller turbine at sites where large turbines are restricted.

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Artificial photosynthesis has the intention of constructing systems doing the same type of processes that the natural photosynthesis. One of the simplest designs is where the photosensitizer is linked in tandem between a water oxidation catalyst and a hydrogen catalyst:

The photosensitizer transfers electrons to the hydrogen catalyst when light reaches it; the electrons becoming oxidized in the process.

This drives the water splitting catalyst to donate electrons to the photosensitizer. The oxidized donor is able to perform water oxidation.

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[mk_fancy_title tag_name=”h2″ style=”false” color=”#393836″ size=”35″ font_weight=”300″ margin_top=”0″ margin_bottom=”25″ font_family=”none” align=”center” el_class=”mk-letter-spacing” font_style=”inhert” txt_transform=”capitalize” letter_spacing=”1″]Types[/mk_fancy_title][mk_fancy_title tag_name=”h2″ style=”false” color=”#5dc677″ size=”20″ font_weight=”normal” margin_top=”15″ margin_bottom=”40″ font_family=”none” align=”center” el_class=”mk-letter-spacing mk-padding-sub-heading ” font_style=”normal” letter_spacing=”2″ animation=”bottom-to-top”]HYDROGEN CATALYSTS[/mk_fancy_title]

Hydrogen is the simplest solar fuel to synthesize because it involves only the transference of two electrons to two protons.

The reaction is as follows:

2 e− + 2 H+ ↔ H+ + H− ↔ H2

The enzymes involved in the proton-to-hydrogen converting catalysts are hydrogenases. These can either reduce protons to molecular hydrogen or oxidize hydrogen to protons and electrons.

There is a lot of information related to the hydrogen catalyst and thanks to this information a big amount of molecules reproducing the structure of the active site of both nickel-iron and iron-iron hydrogenases have been synthesized.

Other catalysts are not structural mimics of hydrogenase but rather functional ones. Synthesized catalysts include structural H-cluster models,a dirhodium photocatalyst, and cobalt catalysts. There is another catalyst to produce solar fuel but it is more expensive and more difficult to carry out due to a higher temperature is required. This is the water-oxidizing catalysts.

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Research in artificial photosynthesis is a multidisciplinary field. Some techniques employed in making and investigating catalysts and solar cells include organic and inorganic chemical synthesis, spectroscopic methods, electrochemistry, molecular biology, microbiology, synthetic biology and crystallography, among others.

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Photoelectrochemical cells are heterogeneous systems that use light to produce electricity or hydrogen. Dye-sensitized solar cell is a hopeful, recent type of solar cell. This cell depends on a semiconductor for current conduction on one electrode and it is covered by a coating of an organic or inorganic dye that acts as a photosensitizer; the counter electrode is a platinum catalyst for H2 production. These cells have a self-repair mechanism and solar-to-electricity conversion efficiencies rivaling those of solid-state semiconductor ones.

[mk_fancy_title tag_name=”h2″ style=”false” color=”#5dc677″ size=”20″ font_weight=”normal” margin_top=”15″ margin_bottom=”40″ font_family=”none” align=”center” el_class=”mk-letter-spacing mk-padding-sub-heading ” font_style=”normal” letter_spacing=”2″ animation=”right-to-left”]PHOTOCATALYTIC WATER SPLITING IN HOMOGENEOUS SYSTEMS[/mk_fancy_title]

Direct water oxidation by photocatalysts is a more efficient usage of solar energy than photoelectrochimical water splitting because it avoids an intermediate thermal or electrical energy conversion step. Some ruthenium complexes are able to oxidize water under solar light irradiation. They have photostability. Improvement of catalyst stability has been tried resorting to polyoxometalates, in particular ruthenium-based ones.

There are another emerging methodologies as the hydrogen-producing artificial systems and NADP+/NADPH coenzyme-inspired catalyst and photobiological production of fuels.