Tidal stream generator - Revision history

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2022-08-21T17:46:19Z

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En>Jmdonev at 17:42, 21 August 2022

2022-08-21T17:42:06Z

← Older revision		Revision as of 17:42, 21 August 2022
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	[[Category:~~Jason edit~~]]		[[Category:Done 2022-12-31]]
	[[Category:Translated to French]]		[[Category:Translated to French]]
	[[fr:Hydrolienne]]		[[fr:Hydrolienne]]
	[[File:Bottom_Mounted_Turbines.png\|thumbnail\|300px\|right\|Figure 1. Axial turbines underwater.<Ref>Wikimedia Commons [Online], Available: https://commons.wikimedia.org/wiki/File:Bottom_Mounted_Turbines.png#/media/File:Bottom_Mounted_Turbines.png</ref>]]		[[File:Bottom_Mounted_Turbines.png\|thumbnail\|300px\|right\|Figure 1. Axial turbines underwater.<Ref>Wikimedia Commons [Online], Available: https://commons.wikimedia.org/wiki/File:Bottom_Mounted_Turbines.png#/media/File:Bottom_Mounted_Turbines.png</ref>]]
	<onlyinclude>'''Tidal stream generators''' use the [[kinetic energy]] of moving water to turn a [[turbine]]—similar to the way a [[wind turbine]] uses [[wind]] to create [[electricity]].</onlyinclude> However, the power available for [[tidal power]] generation in a given area can be ''greater'' than a wind turbine due to the higher [[density]] of [[water]]. These types of tidal generators tend to be the ~~cheapest (though still quite expensive) and most environmentally friendly of any~~ type of [[tidal power]] generation. There are several different specific types of tidal stream generators which will be discussed below.~~'''(maybe a reference in this paragraph?)'''~~		<onlyinclude>'''Tidal stream generators''' use the [[kinetic energy]] of moving water to turn a [[turbine]]—similar to the way a [[wind turbine]] uses [[wind]] to create [[electricity]].</onlyinclude> However, the power available for [[tidal power]] generation in a given area can be ''greater'' than a wind turbine due to the higher [[density]] of [[water]].<ref>Layton, 'A COMPARISON OF ENERGY DENSITIES
			OF PREVALENT ENERGY SOURCES IN UNITS OF JOULES PER CUBIC METER' International Journal of Green Energy, 2008</ref> These types of tidal generators tend to be the least invasive type of [[tidal power]] generation. There are several different specific types of tidal stream generators which will be discussed below.

	These types of generators have a very low visual impact and are mostly or totally submerged. Furthermore, they are less intrusive to marine life because they produce less noise pollution. As discussed on the main [[tidal power]] page, tides are more predictable than wind (which varies a great deal). The density of water is also much higher than air, which means that tidal turbines can be much smaller than wind turbines for the same output.<ref name =Ref3>EMEC. (Accessed July 30, 2015). ''Tidal Devices'' [Online], Available: http://www.emec.org.uk/marine-energy/tidal-devices</ref> This is further enhanced by the use of the [[Venturi effect]], which is a way of getting water to move faster through these [[turbine]]s.		These types of generators have a very low visual impact and are mostly or totally submerged. Furthermore, they are less intrusive to marine life because they produce less noise pollution. As discussed on the main [[tidal power]] page, tides are more predictable than wind (which varies a great deal). The density of water is also much higher than air, which means that tidal turbines can be much smaller than wind turbines for the same output.<ref name =Ref3>EMEC. (Accessed July 30, 2015). ''Tidal Devices'' [Online], Available: http://www.emec.org.uk/marine-energy/tidal-devices</ref> This is further enhanced by the use of the [[Venturi effect]], which is a way of getting water to move faster through these [[turbine]]s.

	The initial investment costs for all types of tidal power technology are extremely high and it takes quite a while to make back that investment. In addition, sea water is quite [[corrosion\|corrosive]] which leads to high maintenance costs.<ref name=Ref3/><ref name=Ref5>TETHYS. (Accessed July 30, 2015). ''Environmental Risk Evaluation System'' [Online], Available: ~~http~~://tethys.pnnl.gov/~~Environmental~~-~~Risk~~-~~Evaluation~~-~~System~~-~~ERES~~</ref>		The initial investment costs for all types of tidal power technology are extremely high and it takes quite a while to make back that investment. In addition, sea water is quite [[corrosion\|corrosive]] which leads to high maintenance costs.<ref name=Ref3/><ref name=Ref5>TETHYS. (Accessed July 30, 2015). ''Environmental Risk Evaluation System'' [Online], Available: https://tethys.pnnl.gov/publications/environmental-risk-evaluation-system-approach-ranking-risk-ocean-energy-development</ref>

	Since the tides flow-in and recede once per day, tidal stream generators provide [[intermittent electricity\|intermittent power generation]].<ref name=Ref5/>		Since the tides flow-in and recede once per day, tidal stream generators provide [[intermittent electricity\|intermittent power generation]].<ref name=Ref5/>

	==~~Varying types~~ of generators==		==Types of turbines and oscillating tidal generators==
	~~'''(Title is about generators while subsections are about turbines...)'''~~
	[[File:horizaxis_tidal_power.gif\|Right\|thumb\|Figure 2. An horizontal turbine, the flowing water makes the turbines spin. The turbine faces the flowing water.<ref name=FORE>Fundamentals of Ocean Renewable Energy : Generating Electricity from the Sea pg 71</ref><ref name=Aquanet>Picture also available online http://www.aquaret.com/indexa15e.html?option accessed May 27th, 2021.</ref>]]		[[File:horizaxis_tidal_power.gif\|Right\|thumb\|Figure 2. An horizontal turbine, the flowing water makes the turbines spin. The turbine faces the flowing water.<ref name=FORE>Fundamentals of Ocean Renewable Energy : Generating Electricity from the Sea pg 71</ref><ref name=Aquanet>Picture also available online http://www.aquaret.com/indexa15e.html?option accessed May 27th, 2021.</ref>]]
	Different designs of tidal power generation may prove to offer different advantages, extensive studies are still needed on this relatively new technology.<ref name=Ref6>Dueling Fuels. (August 7, 2015). "Harnessing the Power of Gravity with Modern Tidal Stream Systems" [Online], Available: http://duelingfuels.com/uncategorized/tidal-stream-systems.php</ref> Studies are needed for maintenance costs vs. income and [[environmental impact]]s over an extended period of time. Power output can vary considerably between these classes of turbines. Currently, research data on stream generators and their power output is scarce due to the emerging nature of the industry.		Different designs of tidal power generation may prove to offer different advantages, extensive studies are still needed on this relatively new technology.<ref name=Ref6>Dueling Fuels. (August 7, 2015). "Harnessing the Power of Gravity with Modern Tidal Stream Systems" [Online], Available: http://duelingfuels.com/uncategorized/tidal-stream-systems.php</ref> Studies are needed for maintenance costs vs. income and [[environmental impact]]s over an extended period of time. Power output can vary considerably between these classes of turbines. Currently, research data on stream generators and their power output is scarce due to the emerging nature of the industry.
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	As seen in Figure 2, axial turbines have a [[rotor]] that is parallel to the incoming water stream. They use rotors similar to those seen on wind turbines but have modifications due to the differing fluid properties of water from air.<ref name=Ref10>"Testing of a Ducted Axial Flow Tidal Turbine" Thomas A. Lokocz, The University of Maine DigitalCommons@UMaine</ref>		As seen in Figure 2, axial turbines have a [[rotor]] that is parallel to the incoming water stream. They use rotors similar to those seen on wind turbines but have modifications due to the differing fluid properties of water from air.<ref name=Ref10>"Testing of a Ducted Axial Flow Tidal Turbine" Thomas A. Lokocz, The University of Maine DigitalCommons@UMaine</ref>

	These devices use the lift of water to generate [[power]]. This requires specially shaped ~~airfoil~~ surfaces ~~'''~~(~~maybe define what~~ an airfoil ~~surface is?~~)~~'''~~ designed to ~~create a [[pressure]] difference~~. This leads to a net [[force]] in the direction perpendicular to the water flow and thus turns the device. Rotors of this type must be carefully oriented (the orientation is referred to as the rotor pitch), to maintain their ability to harness the power of the tide as it changes.<ref name=Ref10 />		These devices use the lift of water to generate [[power]]. This requires specially shaped surfaces (called an [[airfoil]]) designed to turn the turbine. This leads to a net [[force]] in the direction perpendicular to the water flow and thus turns the device. Rotors of this type must be carefully oriented (the orientation is referred to as the rotor pitch), to maintain their ability to harness the power of the tide as it changes.<ref name=Ref10 />


	===Cross-flow turbines===		===Cross-flow turbines===
	[[File:Ossberger_turbine_runner.jpg\|400px\|thumb\|Figure 3. A cross flow water turbine.<Ref>Wikimedia Commons [Online], Available: https://commons.wikimedia.org/wiki/File:Ossberger_turbine_runner.jpg#/media/File:Ossberger_turbine_runner.jpg</ref>]]		[[File:Ossberger_turbine_runner.jpg\|400px\|thumb\|Figure 3. A cross flow water turbine has water hitting the turbine in a sheet as opposed to a jet of water.<Ref>Wikimedia Commons [Online], Available: https://commons.wikimedia.org/wiki/File:Ossberger_turbine_runner.jpg#/media/File:Ossberger_turbine_runner.jpg</ref>]]
	Cross flow turbines (seen in figure 3) have a rotor that is perpendicular to the water flow but parallel to the water surface.<ref name=Ref12>Renewables First. (August 7, 2015). "Crossflow Turbines" [Online], Available: http://www.renewablesfirst.co.uk/hydro-learning-centre/crossflow-turbines</ref>		Cross flow turbines (seen in figure 3) have a rotor that is perpendicular to the water flow (which comes out in a sheet) but parallel to the water surface.<ref name=Ref12>Renewables First. (August 7, 2015). "Crossflow Turbines" [Online], Available: http://www.renewablesfirst.co.uk/hydro-learning-centre/crossflow-turbines</ref> These turbines have water flowing along the axis (across the flow of water, hence the name) rather than just having flow in the direction of motion.
	Unlike axial turbines, these devices typically use the ''[[drag]]'' of water to generate power. In drag-based turbines, the force of the water pushes against a surface, like wind on an open sail. This works because the drag of the open face of the turbine blade is greater than the drag on its closed face. Drag based devices are inherently less efficient than their lift-based counterparts because they operate with respect to the relative flow speed of the water. This means that as a turbine rotates faster ~~the relative flow speed of~~ the water will ~~decrease and thus transfer less of its~~ energy~~.'''(Could maybe use a sentence on how it is different from vertical axis turbines because~~ the ~~picture doesn't show how it works~~ in the water?)'''
			Unlike axial turbines, these devices typically use the ''[[drag]]'' of water to generate power. In drag-based turbines, the force of the water pushes against a surface, like wind on an open sail. This works because the drag of the open face of the turbine blade is greater than the drag on its closed face. Drag based devices are inherently less efficient than their lift-based counterparts because they operate with respect to the relative flow speed of the water. This means that as a turbine rotates faster the water will come out going faster (more kinetic energy leaving the system in the water) and the turbine won't extract as much of the fluid's energy. While this system is less efficient (especially for high velocity situations), it's other advantages can outweigh this inefficiency (operates well with low [[hydraulic head]] and they're simple to construct).<ref>Cross flow turbines https://www.alternative-energy-tutorials.com/hydro-energy/cross-flow-turbine.html accessed October 19th, 2021.</ref>

	===Vertical axis turbines===		===Vertical axis turbines===
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	Oscillating devices do not have a rotational component, instead these generators are pushed back and forth, or up and down by the flowing current to create a hydraulic pump. This pump transfers its energy to a motor, which then turns a generator and creates [[electricity]].<ref name=Ref3 />		Oscillating devices do not have a rotational component, instead these generators are pushed back and forth, or up and down by the flowing current to create a hydraulic pump. This pump transfers its energy to a motor, which then turns a generator and creates [[electricity]].<ref name=Ref3 />

	~~The mechanics on~~ the ~~bottom must,~~ of course, be different for this style of tidal technology.'''(not sure what "mechanics" is referring to)'''		This type of system must be fastened to bottom of the ocean floor. This type fastening would be diff of course, be different for this style of tidal technology.'''(not sure what "mechanics" is referring to)'''

	==For Further Reading==		==For Further Reading==

Jmdonev: 1 revision imported

2021-12-20T19:47:13Z

1 revision imported

← Older revision	Revision as of 19:47, 20 December 2021
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Jmdonev at 21:16, 22 October 2021

2021-10-22T21:16:45Z

← Older revision		Revision as of 21:16, 22 October 2021
Line 1:		Line 1:
	[[Category:~~Done 2021-10-29~~]]		[[Category:Jason edit]]
	[[Category:Translated to French]]		[[Category:Translated to French]]
	[[fr:Hydrolienne]]		[[fr:Hydrolienne]]
	[[File:Bottom_Mounted_Turbines.png\|thumbnail\|300px\|right\|Figure 1. Axial turbines underwater.<Ref>Wikimedia Commons [Online], Available: https://commons.wikimedia.org/wiki/File:Bottom_Mounted_Turbines.png#/media/File:Bottom_Mounted_Turbines.png</ref>]]		[[File:Bottom_Mounted_Turbines.png\|thumbnail\|300px\|right\|Figure 1. Axial turbines underwater.<Ref>Wikimedia Commons [Online], Available: https://commons.wikimedia.org/wiki/File:Bottom_Mounted_Turbines.png#/media/File:Bottom_Mounted_Turbines.png</ref>]]
	<onlyinclude>'''Tidal stream generators''' use the [[kinetic energy]] of moving water to turn a [[turbine]]—similar to the way a [[wind turbine]] uses [[wind]] to create [[electricity]].</onlyinclude> However, the power available for [[tidal power]] generation in a given area can be ''greater'' than a wind turbine due to the higher [[density]] of [[water]].~~<ref>Layton, 'A COMPARISON OF ENERGY DENSITIES~~		<onlyinclude>'''Tidal stream generators''' use the [[kinetic energy]] of moving water to turn a [[turbine]]—similar to the way a [[wind turbine]] uses [[wind]] to create [[electricity]].</onlyinclude> However, the power available for [[tidal power]] generation in a given area can be ''greater'' than a wind turbine due to the higher [[density]] of [[water]]. These types of tidal generators tend to be the cheapest (though still quite expensive) and most environmentally friendly of any type of [[tidal power]] generation. There are several different specific types of tidal stream generators which will be discussed below.'''(maybe a reference in this paragraph?)'''
	~~OF PREVALENT ENERGY SOURCES IN UNITS OF JOULES PER CUBIC METER' International Journal of Green Energy, 2008</ref>~~ These types of tidal generators tend to be the ~~least invasive~~ type of [[tidal power]] generation. There are several different specific types of tidal stream generators which will be discussed below.

	These types of generators have a very low visual impact and are mostly or totally submerged. Furthermore, they are less intrusive to marine life because they produce less noise pollution. As discussed on the main [[tidal power]] page, tides are more predictable than wind (which varies a great deal). The density of water is also much higher than air, which means that tidal turbines can be much smaller than wind turbines for the same output.<ref name =Ref3>EMEC. (Accessed July 30, 2015). ''Tidal Devices'' [Online], Available: http://www.emec.org.uk/marine-energy/tidal-devices</ref> This is further enhanced by the use of the [[Venturi effect]], which is a way of getting water to move faster through these [[turbine]]s.		These types of generators have a very low visual impact and are mostly or totally submerged. Furthermore, they are less intrusive to marine life because they produce less noise pollution. As discussed on the main [[tidal power]] page, tides are more predictable than wind (which varies a great deal). The density of water is also much higher than air, which means that tidal turbines can be much smaller than wind turbines for the same output.<ref name =Ref3>EMEC. (Accessed July 30, 2015). ''Tidal Devices'' [Online], Available: http://www.emec.org.uk/marine-energy/tidal-devices</ref> This is further enhanced by the use of the [[Venturi effect]], which is a way of getting water to move faster through these [[turbine]]s.

	The initial investment costs for all types of tidal power technology are extremely high and it takes quite a while to make back that investment. In addition, sea water is quite [[corrosion\|corrosive]] which leads to high maintenance costs.<ref name=Ref3/><ref name=Ref5>TETHYS. (Accessed July 30, 2015). ''Environmental Risk Evaluation System'' [Online], Available: ~~https~~://tethys.pnnl.gov/~~publications/environmental-risk-evaluation-system-approach-ranking~~-~~risk~~-~~ocean~~-~~energy~~-~~development~~</ref>		The initial investment costs for all types of tidal power technology are extremely high and it takes quite a while to make back that investment. In addition, sea water is quite [[corrosion\|corrosive]] which leads to high maintenance costs.<ref name=Ref3/><ref name=Ref5>TETHYS. (Accessed July 30, 2015). ''Environmental Risk Evaluation System'' [Online], Available: http://tethys.pnnl.gov/Environmental-Risk-Evaluation-System-ERES</ref>

	Since the tides flow-in and recede once per day, tidal stream generators provide [[intermittent electricity\|intermittent power generation]].<ref name=Ref5/>		Since the tides flow-in and recede once per day, tidal stream generators provide [[intermittent electricity\|intermittent power generation]].<ref name=Ref5/>

	==~~Types~~ of ~~turbines and oscillating tidal~~ generators==		==Varying types of generators==
			'''(Title is about generators while subsections are about turbines...)'''
	[[File:horizaxis_tidal_power.gif\|Right\|thumb\|Figure 2. An horizontal turbine, the flowing water makes the turbines spin. The turbine faces the flowing water.<ref name=FORE>Fundamentals of Ocean Renewable Energy : Generating Electricity from the Sea pg 71</ref><ref name=Aquanet>Picture also available online http://www.aquaret.com/indexa15e.html?option accessed May 27th, 2021.</ref>]]		[[File:horizaxis_tidal_power.gif\|Right\|thumb\|Figure 2. An horizontal turbine, the flowing water makes the turbines spin. The turbine faces the flowing water.<ref name=FORE>Fundamentals of Ocean Renewable Energy : Generating Electricity from the Sea pg 71</ref><ref name=Aquanet>Picture also available online http://www.aquaret.com/indexa15e.html?option accessed May 27th, 2021.</ref>]]
	Different designs of tidal power generation may prove to offer different advantages, extensive studies are still needed on this relatively new technology.<ref name=Ref6>Dueling Fuels. (August 7, 2015). "Harnessing the Power of Gravity with Modern Tidal Stream Systems" [Online], Available: http://duelingfuels.com/uncategorized/tidal-stream-systems.php</ref> Studies are needed for maintenance costs vs. income and [[environmental impact]]s over an extended period of time. Power output can vary considerably between these classes of turbines. Currently, research data on stream generators and their power output is scarce due to the emerging nature of the industry.		Different designs of tidal power generation may prove to offer different advantages, extensive studies are still needed on this relatively new technology.<ref name=Ref6>Dueling Fuels. (August 7, 2015). "Harnessing the Power of Gravity with Modern Tidal Stream Systems" [Online], Available: http://duelingfuels.com/uncategorized/tidal-stream-systems.php</ref> Studies are needed for maintenance costs vs. income and [[environmental impact]]s over an extended period of time. Power output can vary considerably between these classes of turbines. Currently, research data on stream generators and their power output is scarce due to the emerging nature of the industry.
Line 19:		Line 19:
	As seen in Figure 2, axial turbines have a [[rotor]] that is parallel to the incoming water stream. They use rotors similar to those seen on wind turbines but have modifications due to the differing fluid properties of water from air.<ref name=Ref10>"Testing of a Ducted Axial Flow Tidal Turbine" Thomas A. Lokocz, The University of Maine DigitalCommons@UMaine</ref>		As seen in Figure 2, axial turbines have a [[rotor]] that is parallel to the incoming water stream. They use rotors similar to those seen on wind turbines but have modifications due to the differing fluid properties of water from air.<ref name=Ref10>"Testing of a Ducted Axial Flow Tidal Turbine" Thomas A. Lokocz, The University of Maine DigitalCommons@UMaine</ref>

	These devices use the lift of water to generate [[power]]. This requires specially shaped surfaces (~~called~~ an [[~~airfoil~~]]~~) designed to turn the turbine~~. This leads to a net [[force]] in the direction perpendicular to the water flow and thus turns the device. Rotors of this type must be carefully oriented (the orientation is referred to as the rotor pitch), to maintain their ability to harness the power of the tide as it changes.<ref name=Ref10 />		These devices use the lift of water to generate [[power]]. This requires specially shaped airfoil surfaces '''(maybe define what an airfoil surface is?)''' designed to create a [[pressure]] difference. This leads to a net [[force]] in the direction perpendicular to the water flow and thus turns the device. Rotors of this type must be carefully oriented (the orientation is referred to as the rotor pitch), to maintain their ability to harness the power of the tide as it changes.<ref name=Ref10 />


	===Cross-flow turbines===		===Cross-flow turbines===
	[[File:Ossberger_turbine_runner.jpg\|400px\|thumb\|Figure 3. A cross flow water turbine ~~has water hitting the turbine in a sheet as opposed to a jet of water~~.<Ref>Wikimedia Commons [Online], Available: https://commons.wikimedia.org/wiki/File:Ossberger_turbine_runner.jpg#/media/File:Ossberger_turbine_runner.jpg</ref>]]		[[File:Ossberger_turbine_runner.jpg\|400px\|thumb\|Figure 3. A cross flow water turbine.<Ref>Wikimedia Commons [Online], Available: https://commons.wikimedia.org/wiki/File:Ossberger_turbine_runner.jpg#/media/File:Ossberger_turbine_runner.jpg</ref>]]
	Cross flow turbines (seen in figure 3) have a rotor that is perpendicular to the water flow ~~(which comes out in a sheet)~~ but parallel to the water surface.<ref name=Ref12>Renewables First. (August 7, 2015). "Crossflow Turbines" [Online], Available: http://www.renewablesfirst.co.uk/hydro-learning-centre/crossflow-turbines</ref> ~~These turbines have water flowing along the axis (across the flow of water, hence the name) rather than just having flow in the direction of motion.~~		Cross flow turbines (seen in figure 3) have a rotor that is perpendicular to the water flow but parallel to the water surface.<ref name=Ref12>Renewables First. (August 7, 2015). "Crossflow Turbines" [Online], Available: http://www.renewablesfirst.co.uk/hydro-learning-centre/crossflow-turbines</ref>
			Unlike axial turbines, these devices typically use the ''[[drag]]'' of water to generate power. In drag-based turbines, the force of the water pushes against a surface, like wind on an open sail. This works because the drag of the open face of the turbine blade is greater than the drag on its closed face. Drag based devices are inherently less efficient than their lift-based counterparts because they operate with respect to the relative flow speed of the water. This means that as a turbine rotates faster the relative flow speed of the water will decrease and thus transfer less of its energy.'''(Could maybe use a sentence on how it is different from vertical axis turbines because the picture doesn't show how it works in the water?)'''
	Unlike axial turbines, these devices typically use the ''[[drag]]'' of water to generate power. In drag-based turbines, the force of the water pushes against a surface, like wind on an open sail. This works because the drag of the open face of the turbine blade is greater than the drag on its closed face. Drag based devices are inherently less efficient than their lift-based counterparts because they operate with respect to the relative flow speed of the water. This means that as a turbine rotates faster the water will ~~come out going faster~~ (~~more kinetic energy leaving~~ the ~~system~~ in the water) ~~and the turbine won~~'~~t extract as much of the fluid~~'~~s energy. While this system is less efficient (especially for high velocity situations), it~~'s other advantages can outweigh this inefficiency (operates well with low [[hydraulic head]] and they're simple to construct).<ref>Cross flow turbines https://www.alternative-energy-tutorials.com/hydro-energy/cross-flow-turbine.html accessed October 19th, 2021.</ref>

	===Vertical axis turbines===		===Vertical axis turbines===
Line 40:		Line 39:
	Oscillating devices do not have a rotational component, instead these generators are pushed back and forth, or up and down by the flowing current to create a hydraulic pump. This pump transfers its energy to a motor, which then turns a generator and creates [[electricity]].<ref name=Ref3 />		Oscillating devices do not have a rotational component, instead these generators are pushed back and forth, or up and down by the flowing current to create a hydraulic pump. This pump transfers its energy to a motor, which then turns a generator and creates [[electricity]].<ref name=Ref3 />

	~~This type of system~~ must ~~be fastened to bottom of the ocean floor. This type fastening would be diff~~ of course, be different for this style of tidal technology.'''(not sure what "mechanics" is referring to)'''		The mechanics on the bottom must, of course, be different for this style of tidal technology.'''(not sure what "mechanics" is referring to)'''

	==For Further Reading==		==For Further Reading==

energy>Jmdonev at 21:41, 19 October 2021

2021-10-19T21:41:04Z

← Older revision		Revision as of 21:41, 19 October 2021
Line 1:		Line 1:
	[[Category:~~Jason edit~~]]		[[Category:Done 2021-10-29]]
	[[Category:Translated to French]]		[[Category:Translated to French]]
	[[fr:Hydrolienne]]		[[fr:Hydrolienne]]

	~~'''Dayna, I made some significant changes to this page. I added some figures, how does it look to you? - Jason'''~~

	'''Jason, the figures look great! Pretty hard to find any other picture for cross-flow turbine, so I think the current picture is fine. Made some edits and 5 comments are bolded. Also noticed that 2 links in the references don't work - "Dueling Fuels" and "TETHYS". - Dayna'''


	[[File:Bottom_Mounted_Turbines.png\|thumbnail\|300px\|right\|Figure 1. Axial turbines underwater.<Ref>Wikimedia Commons [Online], Available: https://commons.wikimedia.org/wiki/File:Bottom_Mounted_Turbines.png#/media/File:Bottom_Mounted_Turbines.png</ref>]]		[[File:Bottom_Mounted_Turbines.png\|thumbnail\|300px\|right\|Figure 1. Axial turbines underwater.<Ref>Wikimedia Commons [Online], Available: https://commons.wikimedia.org/wiki/File:Bottom_Mounted_Turbines.png#/media/File:Bottom_Mounted_Turbines.png</ref>]]
	<onlyinclude>'''Tidal stream generators''' use the [[kinetic energy]] of moving water to turn a [[turbine]]—similar to the way a [[wind turbine]] uses [[wind]] to create [[electricity]].</onlyinclude> However, the power available for [[tidal power]] generation in a given area can be ''greater'' than a wind turbine due to the higher [[density]] of [[water]]. These types of tidal generators tend to be the ~~cheapest (though still quite expensive) and most environmentally friendly of any~~ type of [[tidal power]] generation. There are several different specific types of tidal stream generators which will be discussed below.~~'''(maybe a reference in this paragraph?)'''~~		<onlyinclude>'''Tidal stream generators''' use the [[kinetic energy]] of moving water to turn a [[turbine]]—similar to the way a [[wind turbine]] uses [[wind]] to create [[electricity]].</onlyinclude> However, the power available for [[tidal power]] generation in a given area can be ''greater'' than a wind turbine due to the higher [[density]] of [[water]].<ref>Layton, 'A COMPARISON OF ENERGY DENSITIES
			OF PREVALENT ENERGY SOURCES IN UNITS OF JOULES PER CUBIC METER' International Journal of Green Energy, 2008</ref> These types of tidal generators tend to be the least invasive type of [[tidal power]] generation. There are several different specific types of tidal stream generators which will be discussed below.

	These types of generators have a very low visual impact and are mostly or totally submerged. Furthermore, they are less intrusive to marine life because they produce less noise pollution. As discussed on the main [[tidal power]] page, tides are more predictable than wind (which varies a great deal). The density of water is also much higher than air, which means that tidal turbines can be much smaller than wind turbines for the same output.<ref name =Ref3>EMEC. (Accessed July 30, 2015). ''Tidal Devices'' [Online], Available: http://www.emec.org.uk/marine-energy/tidal-devices</ref> This is further enhanced by the use of the [[Venturi effect]], which is a way of getting water to move faster through these [[turbine]]s.		These types of generators have a very low visual impact and are mostly or totally submerged. Furthermore, they are less intrusive to marine life because they produce less noise pollution. As discussed on the main [[tidal power]] page, tides are more predictable than wind (which varies a great deal). The density of water is also much higher than air, which means that tidal turbines can be much smaller than wind turbines for the same output.<ref name =Ref3>EMEC. (Accessed July 30, 2015). ''Tidal Devices'' [Online], Available: http://www.emec.org.uk/marine-energy/tidal-devices</ref> This is further enhanced by the use of the [[Venturi effect]], which is a way of getting water to move faster through these [[turbine]]s.

	The initial investment costs for all types of tidal power technology are extremely high and it takes quite a while to make back that investment. In addition, sea water is quite [[corrosion\|corrosive]] which leads to high maintenance costs.<ref name=Ref3/><ref name=Ref5>TETHYS. (Accessed July 30, 2015). ''Environmental Risk Evaluation System'' [Online], Available: ~~http~~://tethys.pnnl.gov/~~Environmental~~-~~Risk~~-~~Evaluation~~-~~System~~-~~ERES~~</ref>		The initial investment costs for all types of tidal power technology are extremely high and it takes quite a while to make back that investment. In addition, sea water is quite [[corrosion\|corrosive]] which leads to high maintenance costs.<ref name=Ref3/><ref name=Ref5>TETHYS. (Accessed July 30, 2015). ''Environmental Risk Evaluation System'' [Online], Available: https://tethys.pnnl.gov/publications/environmental-risk-evaluation-system-approach-ranking-risk-ocean-energy-development</ref>

	Since the tides flow-in and recede once per day, tidal stream generators provide [[intermittent electricity\|intermittent power generation]].<ref name=Ref5/>		Since the tides flow-in and recede once per day, tidal stream generators provide [[intermittent electricity\|intermittent power generation]].<ref name=Ref5/>

	==~~Varying types~~ of generators==		==Types of turbines and oscillating tidal generators==
	~~'''(Title is about generators while subsections are about turbines...)'''~~
	[[File:horizaxis_tidal_power.gif\|Right\|thumb\|Figure 2. An horizontal turbine, the flowing water makes the turbines spin. The turbine faces the flowing water.<ref name=FORE>Fundamentals of Ocean Renewable Energy : Generating Electricity from the Sea pg 71</ref><ref name=Aquanet>Picture also available online http://www.aquaret.com/indexa15e.html?option accessed May 27th, 2021.</ref>]]		[[File:horizaxis_tidal_power.gif\|Right\|thumb\|Figure 2. An horizontal turbine, the flowing water makes the turbines spin. The turbine faces the flowing water.<ref name=FORE>Fundamentals of Ocean Renewable Energy : Generating Electricity from the Sea pg 71</ref><ref name=Aquanet>Picture also available online http://www.aquaret.com/indexa15e.html?option accessed May 27th, 2021.</ref>]]
	Different designs of tidal power generation may prove to offer different advantages, extensive studies are still needed on this relatively new technology.<ref name=Ref6>Dueling Fuels. (August 7, 2015). "Harnessing the Power of Gravity with Modern Tidal Stream Systems" [Online], Available: http://duelingfuels.com/uncategorized/tidal-stream-systems.php</ref> Studies are needed for maintenance costs vs. income and [[environmental impact]]s over an extended period of time. Power output can vary considerably between these classes of turbines. Currently, research data on stream generators and their power output is scarce due to the emerging nature of the industry.		Different designs of tidal power generation may prove to offer different advantages, extensive studies are still needed on this relatively new technology.<ref name=Ref6>Dueling Fuels. (August 7, 2015). "Harnessing the Power of Gravity with Modern Tidal Stream Systems" [Online], Available: http://duelingfuels.com/uncategorized/tidal-stream-systems.php</ref> Studies are needed for maintenance costs vs. income and [[environmental impact]]s over an extended period of time. Power output can vary considerably between these classes of turbines. Currently, research data on stream generators and their power output is scarce due to the emerging nature of the industry.
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	As seen in Figure 2, axial turbines have a [[rotor]] that is parallel to the incoming water stream. They use rotors similar to those seen on wind turbines but have modifications due to the differing fluid properties of water from air.<ref name=Ref10>"Testing of a Ducted Axial Flow Tidal Turbine" Thomas A. Lokocz, The University of Maine DigitalCommons@UMaine</ref>		As seen in Figure 2, axial turbines have a [[rotor]] that is parallel to the incoming water stream. They use rotors similar to those seen on wind turbines but have modifications due to the differing fluid properties of water from air.<ref name=Ref10>"Testing of a Ducted Axial Flow Tidal Turbine" Thomas A. Lokocz, The University of Maine DigitalCommons@UMaine</ref>

	These devices use the lift of water to generate [[power]]. This requires specially shaped ~~airfoil~~ surfaces ~~'''~~(~~maybe define what~~ an airfoil ~~surface is?~~)~~'''~~ designed to ~~create a [[pressure]] difference~~. This leads to a net [[force]] in the direction perpendicular to the water flow and thus turns the device. Rotors of this type must be carefully oriented (the orientation is referred to as the rotor pitch), to maintain their ability to harness the power of the tide as it changes.<ref name=Ref10 />		These devices use the lift of water to generate [[power]]. This requires specially shaped surfaces (called an [[airfoil]]) designed to turn the turbine. This leads to a net [[force]] in the direction perpendicular to the water flow and thus turns the device. Rotors of this type must be carefully oriented (the orientation is referred to as the rotor pitch), to maintain their ability to harness the power of the tide as it changes.<ref name=Ref10 />


	===Cross-flow turbines===		===Cross-flow turbines===
	[[File:Ossberger_turbine_runner.jpg\|400px\|thumb\|Figure 3. A cross flow water turbine.<Ref>Wikimedia Commons [Online], Available: https://commons.wikimedia.org/wiki/File:Ossberger_turbine_runner.jpg#/media/File:Ossberger_turbine_runner.jpg</ref>]]		[[File:Ossberger_turbine_runner.jpg\|400px\|thumb\|Figure 3. A cross flow water turbine has water hitting the turbine in a sheet as opposed to a jet of water.<Ref>Wikimedia Commons [Online], Available: https://commons.wikimedia.org/wiki/File:Ossberger_turbine_runner.jpg#/media/File:Ossberger_turbine_runner.jpg</ref>]]
	Cross flow turbines (seen in figure 3) have a rotor that is perpendicular to the water flow but parallel to the water surface.<ref name=Ref12>Renewables First. (August 7, 2015). "Crossflow Turbines" [Online], Available: http://www.renewablesfirst.co.uk/hydro-learning-centre/crossflow-turbines</ref>		Cross flow turbines (seen in figure 3) have a rotor that is perpendicular to the water flow (which comes out in a sheet) but parallel to the water surface.<ref name=Ref12>Renewables First. (August 7, 2015). "Crossflow Turbines" [Online], Available: http://www.renewablesfirst.co.uk/hydro-learning-centre/crossflow-turbines</ref> These turbines have water flowing along the axis (across the flow of water, hence the name) rather than just having flow in the direction of motion.
	Unlike axial turbines, these devices typically use the ''[[drag]]'' of water to generate power. In drag-based turbines, the force of the water pushes against a surface, like wind on an open sail. This works because the drag of the open face of the turbine blade is greater than the drag on its closed face. Drag based devices are inherently less efficient than their lift-based counterparts because they operate with respect to the relative flow speed of the water. This means that as a turbine rotates faster ~~the relative flow speed of~~ the water will ~~decrease and thus transfer less of its~~ energy~~.'''(Could maybe use a sentence on how it is different from vertical axis turbines because~~ the ~~picture doesn't show how it works~~ in the water?)'''
			Unlike axial turbines, these devices typically use the ''[[drag]]'' of water to generate power. In drag-based turbines, the force of the water pushes against a surface, like wind on an open sail. This works because the drag of the open face of the turbine blade is greater than the drag on its closed face. Drag based devices are inherently less efficient than their lift-based counterparts because they operate with respect to the relative flow speed of the water. This means that as a turbine rotates faster the water will come out going faster (more kinetic energy leaving the system in the water) and the turbine won't extract as much of the fluid's energy. While this system is less efficient (especially for high velocity situations), it's other advantages can outweigh this inefficiency (operates well with low [[hydraulic head]] and they're simple to construct).<ref>Cross flow turbines https://www.alternative-energy-tutorials.com/hydro-energy/cross-flow-turbine.html accessed October 19th, 2021.</ref>

	===Vertical axis turbines===		===Vertical axis turbines===
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	Oscillating devices do not have a rotational component, instead these generators are pushed back and forth, or up and down by the flowing current to create a hydraulic pump. This pump transfers its energy to a motor, which then turns a generator and creates [[electricity]].<ref name=Ref3 />		Oscillating devices do not have a rotational component, instead these generators are pushed back and forth, or up and down by the flowing current to create a hydraulic pump. This pump transfers its energy to a motor, which then turns a generator and creates [[electricity]].<ref name=Ref3 />

	~~The mechanics on~~ the ~~bottom must,~~ of course, be different for this style of tidal technology.'''(not sure what "mechanics" is referring to)'''		This type of system must be fastened to bottom of the ocean floor. This type fastening would be diff of course, be different for this style of tidal technology.'''(not sure what "mechanics" is referring to)'''

	==For Further Reading==		==For Further Reading==

Jmdonev: 1 revision imported

2021-09-27T00:03:09Z

1 revision imported

← Older revision	Revision as of 00:03, 27 September 2021
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energy>Ethan.boechler at 20:12, 10 September 2021

2021-09-10T20:12:53Z

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	[[Category:~~Done 2018~~-12-10]]		[[Category:Jason edit]]
	<onlyinclude>'''Tidal stream generators''' ~~make~~ use of the [[kinetic energy]] of moving water to turn a [[turbine]]—similar to the way a [[wind turbine]] uses [[wind]] to create [[electricity]].</onlyinclude> However, the power available for [[tidal power]] generation in a given area can be ''greater'' than a wind turbine due to the higher [[density]] of [[water]]. These types of tidal generators tend to be the cheapest (though still quite expensive) and most environmentally friendly of any type of [[tidal power]] generation. There are several different specific types of tidal stream generators which will be discussed below.		[[Category:Translated to French]]
			[[fr:Hydrolienne]]

			'''Dayna, I made some significant changes to this page. I added some figures, how does it look to you? - Jason'''

			'''Jason, the figures look great! Pretty hard to find any other picture for cross-flow turbine, so I think the current picture is fine. Made some edits and 5 comments are bolded. Also noticed that 2 links in the references don't work - "Dueling Fuels" and "TETHYS". - Dayna'''


			[[File:Bottom_Mounted_Turbines.png\|thumbnail\|300px\|right\|Figure 1. Axial turbines underwater.<Ref>Wikimedia Commons [Online], Available: https://commons.wikimedia.org/wiki/File:Bottom_Mounted_Turbines.png#/media/File:Bottom_Mounted_Turbines.png</ref>]]
			<onlyinclude>'''Tidal stream generators''' use the [[kinetic energy]] of moving water to turn a [[turbine]]—similar to the way a [[wind turbine]] uses [[wind]] to create [[electricity]].</onlyinclude> However, the power available for [[tidal power]] generation in a given area can be ''greater'' than a wind turbine due to the higher [[density]] of [[water]]. These types of tidal generators tend to be the cheapest (though still quite expensive) and most environmentally friendly of any type of [[tidal power]] generation. There are several different specific types of tidal stream generators which will be discussed below.'''(maybe a reference in this paragraph?)'''

	These types of generators have a very low visual impact and are mostly or totally submerged. Furthermore, they are less intrusive to marine life because they produce less noise pollution. As discussed on the main [[tidal power]] page, tides are more predictable than wind (which varies a great deal). The density of water is also much higher than air, which means that tidal turbines can be much smaller than wind turbines for the same output.<ref name =Ref3>EMEC. (Accessed July 30, 2015). ''Tidal Devices'' [Online], Available: http://www.emec.org.uk/marine-energy/tidal-devices</ref> This is further enhanced by the use of the [[Venturi effect]], which is a way of getting water to move faster through these [[turbine]]s.		These types of generators have a very low visual impact and are mostly or totally submerged. Furthermore, they are less intrusive to marine life because they produce less noise pollution. As discussed on the main [[tidal power]] page, tides are more predictable than wind (which varies a great deal). The density of water is also much higher than air, which means that tidal turbines can be much smaller than wind turbines for the same output.<ref name =Ref3>EMEC. (Accessed July 30, 2015). ''Tidal Devices'' [Online], Available: http://www.emec.org.uk/marine-energy/tidal-devices</ref> This is further enhanced by the use of the [[Venturi effect]], which is a way of getting water to move faster through these [[turbine]]s.

	The initial investment costs for all types of tidal power technology are extremely high and it takes quite a while to make back that investment. In addition, sea water is quite [[corrosion\|corrosive]] which leads to high maintenance costs.<ref name=~~Ref4>EMEC. (Accessed July 30, 2015). ''Tidal Devices'' [Online], Available: http:~~/~~/www.emec.org.uk/marine-energy/tidal-devices</ref~~><ref name=Ref5>TETHYS. (Accessed July 30, 2015). ''Environmental Risk Evaluation System'' [Online], Available: http://tethys.pnnl.gov/Environmental-Risk-Evaluation-System-ERES</ref>		The initial investment costs for all types of tidal power technology are extremely high and it takes quite a while to make back that investment. In addition, sea water is quite [[corrosion\|corrosive]] which leads to high maintenance costs.<ref name=Ref3/><ref name=Ref5>TETHYS. (Accessed July 30, 2015). ''Environmental Risk Evaluation System'' [Online], Available: http://tethys.pnnl.gov/Environmental-Risk-Evaluation-System-ERES</ref>

	Since the tides flow-in and recede once per day, tidal stream generators provide [[intermittent electricity\|intermittent power generation]].<ref name=Ref5/>		Since the tides flow-in and recede once per day, tidal stream generators provide [[intermittent electricity\|intermittent power generation]].<ref name=Ref5/>

	==Varying types of generators==		==Varying types of generators==
	Different designs of tidal power generation may prove to offer different advantages, extensive studies are still needed on this relatively new technology.<ref name=Ref6>Dueling Fuels. (August 7, 2015). "Harnessing the Power of Gravity with Modern Tidal Stream Systems" [Online], Available: http://duelingfuels.com/uncategorized/tidal-stream-systems.php</ref> Studies are needed for maintenance costs vs. income and [[environmental impact]]s over an extended period of time. Power output can vary considerably between these classes of turbines~~. However, since the tidal power industry is so new predictions for power output vary considerably~~. Currently, research data on stream generators is scarce due to the emerging nature of the industry.		'''(Title is about generators while subsections are about turbines...)'''
			[[File:horizaxis_tidal_power.gif\|Right\|thumb\|Figure 2. An horizontal turbine, the flowing water makes the turbines spin. The turbine faces the flowing water.<ref name=FORE>Fundamentals of Ocean Renewable Energy : Generating Electricity from the Sea pg 71</ref><ref name=Aquanet>Picture also available online http://www.aquaret.com/indexa15e.html?option accessed May 27th, 2021.</ref>]]
			Different designs of tidal power generation may prove to offer different advantages, extensive studies are still needed on this relatively new technology.<ref name=Ref6>Dueling Fuels. (August 7, 2015). "Harnessing the Power of Gravity with Modern Tidal Stream Systems" [Online], Available: http://duelingfuels.com/uncategorized/tidal-stream-systems.php</ref> Studies are needed for maintenance costs vs. income and [[environmental impact]]s over an extended period of time. Power output can vary considerably between these classes of turbines. Currently, research data on stream generators and their power output is scarce due to the emerging nature of the industry.

	===Axial (horizontal) turbines===		===Axial (horizontal) turbines===
	~~[[File:Bottom_Mounted_Turbines.png\|thumbnail\|200px\|right\|~~Figure ~~1: Axial turbines underwater.<Ref>Wikimedia Commons [Online]~~, ~~Available: https://commons.wikimedia.org/wiki/File:Bottom_Mounted_Turbines.png#/media/File:Bottom_Mounted_Turbines.png</ref>]]~~		As seen in Figure 2, axial turbines have a [[rotor]] that is parallel to the incoming water stream. They use rotors similar to those seen on wind turbines but have modifications due to the differing fluid properties of water from air.<ref name=Ref10>"Testing of a Ducted Axial Flow Tidal Turbine" Thomas A. Lokocz, The University of Maine DigitalCommons@UMaine</ref>
	~~Axial~~ turbines have a [[rotor]] that is parallel to the incoming water stream. They use rotors similar to those seen on wind turbines but have modifications due to the differing fluid properties of water from air.<ref name=Ref10>"Testing of a Ducted Axial Flow Tidal Turbine" Thomas A. Lokocz, The University of Maine DigitalCommons@UMaine</ref>
			These devices use the lift of water to generate [[power]]. This requires specially shaped airfoil surfaces '''(maybe define what an airfoil surface is?)''' designed to create a [[pressure]] difference. This leads to a net [[force]] in the direction perpendicular to the water flow and thus turns the device. Rotors of this type must be carefully oriented (the orientation is referred to as the rotor pitch), to maintain their ability to harness the power of the tide as it changes.<ref name=Ref10 />

	These devices use the lift of water to generate power. This requires specially shaped airfoil surfaces designed to create a [[pressure]] difference. This leads to a net [[force]] in the direction perpendicular to the water flow and thus turns the device. Rotors of this type must be carefully oriented (the orientation is referred to as the rotor pitch), to maintain their ability to harness the power of the tide as it changes.<ref name=Ref10 />

	===Cross-flow turbines===		===Cross-flow turbines===
	[[File:Ossberger_turbine_runner.jpg\|~~200px~~\|thumb\|Figure 2. A cross flow water turbine.<Ref>Wikimedia Commons [Online], Available: https://commons.wikimedia.org/wiki/File:Ossberger_turbine_runner.jpg#/media/File:Ossberger_turbine_runner.jpg</ref>]]		[[File:Ossberger_turbine_runner.jpg\|400px\|thumb\|Figure 3. A cross flow water turbine.<Ref>Wikimedia Commons [Online], Available: https://commons.wikimedia.org/wiki/File:Ossberger_turbine_runner.jpg#/media/File:Ossberger_turbine_runner.jpg</ref>]]
	Cross flow turbines have a rotor that is perpendicular to the water flow but parallel to the water surface~~, see Figure 2~~.<ref name=Ref12>Renewables First. (August 7, 2015). "Crossflow Turbines" [Online], Available: http://www.renewablesfirst.co.uk/hydro-learning-centre/crossflow-turbines</ref>		Cross flow turbines (seen in figure 3) have a rotor that is perpendicular to the water flow but parallel to the water surface.<ref name=Ref12>Renewables First. (August 7, 2015). "Crossflow Turbines" [Online], Available: http://www.renewablesfirst.co.uk/hydro-learning-centre/crossflow-turbines</ref>
	Unlike axial turbines, these devices typically use the ''[[drag]]'' of water to generate power. In drag-based turbines, the force of the water pushes against a surface, like wind on an open sail. This works because the drag of the open face of the turbine blade is greater than the drag on its closed face. Drag based devices are inherently less efficient than their lift-based counterparts because they operate with respect to the relative flow speed of the water. This means that as a turbine rotates faster the relative flow speed of the water will decrease and thus transfer less of its energy.		Unlike axial turbines, these devices typically use the ''[[drag]]'' of water to generate power. In drag-based turbines, the force of the water pushes against a surface, like wind on an open sail. This works because the drag of the open face of the turbine blade is greater than the drag on its closed face. Drag based devices are inherently less efficient than their lift-based counterparts because they operate with respect to the relative flow speed of the water. This means that as a turbine rotates faster the relative flow speed of the water will decrease and thus transfer less of its energy.'''(Could maybe use a sentence on how it is different from vertical axis turbines because the picture doesn't show how it works in the water?)'''

	===Vertical axis turbines===		===Vertical axis turbines===
	~~With~~ vertical axis ~~turbines~~ the ~~rotational~~ axis of the rotor is vertical to the water surface and also perpendicular to the incoming water flow. Both lift and drag type blades can be used in these turbines.<ref name=Ref14>S. Khalid, Z. Liang and N. Shah. (August 7, 2015). "Harnessing Tidal Energy Using Vertical Axis Tidal Turbine" [Online], Available: http://maxwellsci.com/print/rjaset/v5-239-252.pdf</ref>		[[File:vertaxis_tidal_power.gif\|Right\|thumb\|Figure 4. Conceptual design of a vertical axis turbine. The flowing water moves across the turbine spinning it on an axis that points down, instead of towards the water.<ref name=FORE/><ref name=Aquanet/>]]
			As seen in Figure 4, vertical axis turbines have a rotor that is vertical to the water surface and also perpendicular to the incoming water flow. Both lift and drag type blades can be used in these turbines.<ref name=Ref14>S. Khalid, Z. Liang and N. Shah. (August 7, 2015). "Harnessing Tidal Energy Using Vertical Axis Tidal Turbine" [Online], Available: http://maxwellsci.com/print/rjaset/v5-239-252.pdf</ref>

			This style of turbine is less familiar to most people because [[horizontal axis wind turbine]]s are more common than [[vertical axis wind turbine]]s. Despite the lack of familiarity, vertical axis wind turbines have been in operation for a fairly long time. Also notice that these particular tidal stream generators are attached to the surface rather than the bottom. The advantage of this style of turbine is that the tidal flow can come from different directions, and motion can still be harnessed for electricity. This is similar to the advantage of a vertical axis wind turbine.



	===Oscillating generators===		===Oscillating generators===
	Oscillating devices do not have a rotational component, instead these generators ~~make use of sections which~~ are pushed ~~sideways~~ by the flowing current to create a hydraulic pump. This pump transfers its energy to a motor, which then turns a generator and creates [[electricity]].<ref name=Ref3 />		[[File:reciprocating hydrofoil.gif\|Right\|thumb\|Figure 5. An oscillating generator, the flowing water makes the foil move up and down, with the generator housed out of the flow of the tidal water.<ref name=FORE/><ref name=Aquanet/>]]
			Oscillating devices do not have a rotational component, instead these generators are pushed back and forth, or up and down by the flowing current to create a hydraulic pump. This pump transfers its energy to a motor, which then turns a generator and creates [[electricity]].<ref name=Ref3 />

			The mechanics on the bottom must, of course, be different for this style of tidal technology.'''(not sure what "mechanics" is referring to)'''

	==For Further Reading==		==For Further Reading==

Jmdonev: 1 revision imported

2019-01-04T18:14:57Z

1 revision imported

← Older revision	Revision as of 18:14, 4 January 2019
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2dev>Jmdonev at 22:12, 1 November 2018

2018-11-01T22:12:47Z

← Older revision		Revision as of 22:12, 1 November 2018
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	[[Category:Done ~~2015~~-08-21]]		[[Category:Done 2018-12-10]]
	<onlyinclude>'''Tidal stream generators''' make use of the [[kinetic energy]] of moving water to turn a [[turbine]] ~~- similar~~ to the way a [[wind turbine]] uses [[wind]] to create [[electricity]].</onlyinclude> However, the power available for [[tidal power]] generation in a given area can be greater than a wind turbine due to the higher [[density]] of [[water]]. These types of tidal generators tend to be the cheapest (though still quite expensive) and most environmentally friendly of any type of [[tidal power]] generation. There are several different specific types of tidal stream generators which will be discussed below.		<onlyinclude>'''Tidal stream generators''' make use of the [[kinetic energy]] of moving water to turn a [[turbine]]—similar to the way a [[wind turbine]] uses [[wind]] to create [[electricity]].</onlyinclude> However, the power available for [[tidal power]] generation in a given area can be ''greater'' than a wind turbine due to the higher [[density]] of [[water]]. These types of tidal generators tend to be the cheapest (though still quite expensive) and most environmentally friendly of any type of [[tidal power]] generation. There are several different specific types of tidal stream generators which will be discussed below.

	These types of generators have a very low visual impact and are ~~mainly, if not~~ totally submerged. Furthermore, they are less intrusive to marine life because they produce less noise pollution. As discussed on the main [[tidal power]] page, tides are more predictable, than wind which varies a great deal. The density of water is also much higher than air, which means that tidal turbines can be much smaller than wind turbines ~~of comparable~~ output.<ref name =Ref3>EMEC. (Accessed July 30, 2015). ''Tidal Devices'' [Online], Available: http://www.emec.org.uk/marine-energy/tidal-devices</ref> This is further enhanced by the use of the [[Venturi effect]], which is a way of getting water to move faster through these [[turbine]]s.		These types of generators have a very low visual impact and are mostly or totally submerged. Furthermore, they are less intrusive to marine life because they produce less noise pollution. As discussed on the main [[tidal power]] page, tides are more predictable than wind (which varies a great deal). The density of water is also much higher than air, which means that tidal turbines can be much smaller than wind turbines for the same output.<ref name =Ref3>EMEC. (Accessed July 30, 2015). ''Tidal Devices'' [Online], Available: http://www.emec.org.uk/marine-energy/tidal-devices</ref> This is further enhanced by the use of the [[Venturi effect]], which is a way of getting water to move faster through these [[turbine]]s.

	~~As with~~ all types of tidal power technology ~~the initial investment costs~~ are extremely high and it takes quite a while to make back that investment. ~~Unfortunately~~, sea water is quite corrosive which leads to high maintenance costs.<ref name=Ref4>EMEC. (Accessed July 30, 2015). ''Tidal Devices'' [Online], Available: http://www.emec.org.uk/marine-energy/tidal-devices</ref><ref name=Ref5>TETHYS. (Accessed July 30, 2015). ''Environmental Risk Evaluation System'' [Online], Available: http://tethys.pnnl.gov/Environmental-Risk-Evaluation-System-ERES</ref>		The initial investment costs for all types of tidal power technology are extremely high and it takes quite a while to make back that investment. In addition, sea water is quite [[corrosion\|corrosive]] which leads to high maintenance costs.<ref name=Ref4>EMEC. (Accessed July 30, 2015). ''Tidal Devices'' [Online], Available: http://www.emec.org.uk/marine-energy/tidal-devices</ref><ref name=Ref5>TETHYS. (Accessed July 30, 2015). ''Environmental Risk Evaluation System'' [Online], Available: http://tethys.pnnl.gov/Environmental-Risk-Evaluation-System-ERES</ref>

	Since the tides flow-in and recede once ~~each~~ per day tidal stream generators provide [[intermittent electricity\|intermittent power generation]].<ref name=Ref5/>		Since the tides flow-in and recede once per day, tidal stream generators provide [[intermittent electricity\|intermittent power generation]].<ref name=Ref5/>

	==Varying types of generators==		==Varying types of generators==
	Different designs of tidal power generation may prove to offer different advantages, extensive studies are still needed on this relatively new technology.<ref name=Ref6>Dueling Fuels. (August 7, 2015). "Harnessing the Power of Gravity with Modern Tidal Stream Systems" [Online], Available: http://duelingfuels.com/uncategorized/tidal-stream-systems.php</ref> Studies are needed for maintenance costs vs. income ~~and~~ and [[environmental impact]]s over an extended period of time. Power output can vary considerably between these classes of turbines. However, since the tidal power industry is so new predictions for power output vary considerably. Currently, research data on stream generators is scarce due to the emerging nature of the industry.		Different designs of tidal power generation may prove to offer different advantages, extensive studies are still needed on this relatively new technology.<ref name=Ref6>Dueling Fuels. (August 7, 2015). "Harnessing the Power of Gravity with Modern Tidal Stream Systems" [Online], Available: http://duelingfuels.com/uncategorized/tidal-stream-systems.php</ref> Studies are needed for maintenance costs vs. income and [[environmental impact]]s over an extended period of time. Power output can vary considerably between these classes of turbines. However, since the tidal power industry is so new predictions for power output vary considerably. Currently, research data on stream generators is scarce due to the emerging nature of the industry.

	===Axial (horizontal) turbines===		===Axial (horizontal) turbines===
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	[[File:Ossberger_turbine_runner.jpg\|200px\|thumb\|Figure 2. A cross flow water turbine.<Ref>Wikimedia Commons [Online], Available: https://commons.wikimedia.org/wiki/File:Ossberger_turbine_runner.jpg#/media/File:Ossberger_turbine_runner.jpg</ref>]]		[[File:Ossberger_turbine_runner.jpg\|200px\|thumb\|Figure 2. A cross flow water turbine.<Ref>Wikimedia Commons [Online], Available: https://commons.wikimedia.org/wiki/File:Ossberger_turbine_runner.jpg#/media/File:Ossberger_turbine_runner.jpg</ref>]]
	Cross flow turbines have a rotor that is perpendicular to the water flow but parallel to the water surface, see Figure 2.<ref name=Ref12>Renewables First. (August 7, 2015). "Crossflow Turbines" [Online], Available: http://www.renewablesfirst.co.uk/hydro-learning-centre/crossflow-turbines</ref>		Cross flow turbines have a rotor that is perpendicular to the water flow but parallel to the water surface, see Figure 2.<ref name=Ref12>Renewables First. (August 7, 2015). "Crossflow Turbines" [Online], Available: http://www.renewablesfirst.co.uk/hydro-learning-centre/crossflow-turbines</ref>
	Unlike axial turbines, these devices typically use the [[drag]] of water to generate power. In drag-based turbines, the force of the water pushes against a surface, like wind on an open sail. This works because the drag of the open face of the turbine blade is greater than the drag on its closed face. Drag based devices are inherently less efficient than their lift based counterparts because they operate with respect to the relative flow speed of the water. This means that as a turbine rotates faster the relative flow speed of the water will decrease and thus transfer less of its energy.		Unlike axial turbines, these devices typically use the ''[[drag]]'' of water to generate power. In drag-based turbines, the force of the water pushes against a surface, like wind on an open sail. This works because the drag of the open face of the turbine blade is greater than the drag on its closed face. Drag based devices are inherently less efficient than their lift-based counterparts because they operate with respect to the relative flow speed of the water. This means that as a turbine rotates faster the relative flow speed of the water will decrease and thus transfer less of its energy.

	===Vertical axis turbines===		===Vertical axis turbines===
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	===Oscillating generators===		===Oscillating generators===
	Oscillating devices do not have a rotational component, instead these generators make use of sections which are pushed sideways by the flowing current to create a hydraulic pump. This pump transfers its energy to a motor, which then turns a generator and creates [[electricity]].<ref name=Ref3 />		Oscillating devices do not have a rotational component, instead these generators make use of sections which are pushed sideways by the flowing current to create a hydraulic pump. This pump transfers its energy to a motor, which then turns a generator and creates [[electricity]].<ref name=Ref3 />

			==For Further Reading==
			*[[Tidal power]]
			*[[Generator]]
			*[[Venturi effect]]
			*[[Pressure]]
			*[[Drag]]
			*Or explore a [[Special:Random\|random page]]

	==References==		==References==
	{{reflist}}		{{reflist}}
	[[Category:Uploaded]]		[[Category:Uploaded]]

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2015-08-26T21:31:44Z

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