Wind Energy Background - Revision history

Abhinandanb: /* Brief History of Wind Energy */

2011-05-11T05:01:57Z

‎Brief History of Wind Energy

Crazypaddu: /* Like this report? */

2011-05-04T06:42:57Z

‎<span style="color:#C41E3A">Like this report?</span>

Crazypaddu: /* Wind Turbine Control Systems */

2011-03-18T06:11:52Z

‎Wind Turbine Control Systems

Crazypaddu: /* Wind Turbine Control Systems */

2011-03-18T05:40:52Z

‎Wind Turbine Control Systems

Crazypaddu: /* IPC Classifications */

2011-03-18T05:39:33Z

‎IPC Classifications

Crazypaddu: /* IPC Classifications */

2011-03-18T05:33:29Z

‎IPC Classifications

Crazypaddu: /* IPC Classifications */

2011-03-18T05:32:03Z

‎IPC Classifications

Crazypaddu: /* Wind Turbine Control Systems */

2011-03-18T05:29:34Z

‎Wind Turbine Control Systems

Crazypaddu: /* Electrical Generating Systems */

2011-03-18T05:25:25Z

‎Electrical Generating Systems

Crazypaddu: /* Horizontal Axis and Vertical Axis Wind Turbines */

2011-03-18T05:21:55Z

‎Horizontal Axis and Vertical Axis Wind Turbines

← Older revision		Revision as of 05:01, 11 May 2011
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−	~~==Brief History of Wind Energy==~~
−	Although the use of wind power started around 5000 BC, but electric power generation through wind energy started in 18th century and increasing drastically in 19th and 20th centuries. A brief view on developments on wind power sector are listed below.
−	~~[[Image:totalcapacityworld2009.JPEG\|thumb\|right\|400px\|Fig 1 '''[http://www.wwindea.org/home/index.php Development of wind power worldwide]''']]~~
−	* [http://www.brighthub.com/environment/renewable-energy/articles/71440.aspx 1887] : Prof. James Blyth of Scotland used windmills for generating electricity.
−	* [http://www.brighthub.com/environment/renewable-energy/articles/71440.aspx 1888] : Charles Brush developed the first wind-powered turbine that generated electricity in the United States based on emulated James Blyth work.
−	* [http://www.brighthub.com/environment/renewable-energy/articles/71440.aspx 1927] : Joe Jacobs and Marcellus Jacobs improved the wind turbine generator for use in farms.
−	* [http://www.brighthub.com/environment/renewable-energy/articles/71440.aspx 1931] : development of Darrieus wind turbine. It is a vertical axis turbine that rotates with wind from any direction.
−	* 1941: Largest mega watt range wind turbine was connected to the local electrical distribution system on the mountain known as Grandpa's Knob in Castleton, Vermont, USA.
−	* 1971: Denmark installed the first offshore wind farms
−	* 1990s: More than 2200 MW capacity of wind turbines are installed in california.
−	* 2003: the largest offshore wind farm North Hoyle was built in the United Kingdom.
−	* 2003-2010: Research is going is on wind turbines in blades structures, generators, operation and protection, efficiency of wind turbines.
−	~~Source:[[Media:windenergy.pdf\| Wind Energy]]<br>~~
−	~~The total installed wind power capacity from 2001 to 2010 is shown in fig. 1. All wind turbines installed by the end of year 2009 worldwide are generating 340 TWh per annum.~~
−	~~The country wise share of wind energy by the end of year 2009 is shown in fig. 2.~~
−	~~[[Image:countryshare.JPEG\|thumb\|center\|350px\|Fig 2 '''[http://www.wwindea.org/home/index.php Country share of total capacity]''']]~~
−
	==Working Principle of Wind Turbine ==		==Working Principle of Wind Turbine ==
	Wind is air in motion. It is a form of solar energy. Solar radiation heats every part of the Earth’s surface unevenly due to irregularities and rotation of earth. The flow of wind patterns are modified by the earth's terrain, bodies of water, and vegetative cover. When air moves, causing wind, it has kinetic energy. The kinetic energy of wind can be captured by a wind turbine and converted to other forms of energy such as electricity or mechanical power.		Wind is air in motion. It is a form of solar energy. Solar radiation heats every part of the Earth’s surface unevenly due to irregularities and rotation of earth. The flow of wind patterns are modified by the earth's terrain, bodies of water, and vegetative cover. When air moves, causing wind, it has kinetic energy. The kinetic energy of wind can be captured by a wind turbine and converted to other forms of energy such as electricity or mechanical power.

@@ Line 233: / Line 233: @@
 <br>
 {|border="2" cellspacing="0" cellpadding="1" width="15%"
 | style="background-color:#999990;padding:0.079cm;"| <center>[http://dolcera.com/wiki/index.php?title=Wind_Energy <<Back to main page]</center>
 |}

@@ Line 134: / Line 134: @@
 |-
 |rowspan="2" align = "center" bgcolor = "#DCE6F1"|'''Description'''
-|bgcolor = "#DCE6F1"|A method of controlling the speed of a wind turbine by varying the orientation, or pitch, of the blades, and thereby altering its aerodynamics and efficiency.
+|-valign="top' bgcolor = "#DCE6F1"|A method of controlling the speed of a wind turbine by varying the orientation, or pitch, of the blades, and thereby altering its aerodynamics and efficiency.
 Source:[http://www.moog.com/markets/energy/wind-turbines/blade-pitch-control/ Blade Pitch Control]
 |bgcolor = "#DCE6F1"|The rotation of horizontal axis wind turbine around its tower to orient the turbine in upwind or down wind direction.

@@ Line 133: / Line 133: @@
 |align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''Generator torque control'''</font>
 |-
-|bgcolor = "#DCE6F1"|rowspan="2" align = "center" bgcolor = "#83caff"|'''Description'''
+|rowspan="2" align = "center" bgcolor = "#DCE6F1"|'''Description'''
 |bgcolor = "#DCE6F1"|A method of controlling the speed of a wind turbine by varying the orientation, or pitch, of the blades, and thereby altering its aerodynamics and efficiency.
 Source:[http://www.moog.com/markets/energy/wind-turbines/blade-pitch-control/ Blade Pitch Control]

@@ Line 163: / Line 163: @@
 | align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''Description'''</font>
 |-
-| bgcolor = "#DCE6F1"| align = "center" bgcolor = "#99ccff"|1
+| align = "center"  bgcolor = "#DCE6F1"|1
-| bgcolor = "#DCE6F1"| align = "center"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=F03D F03D]
+| align = "center" bgcolor = "#DCE6F1"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=F03D F03D]
 | bgcolor = "#DCE6F1"| Machines or engines for liquids; wind, spring, or weight motors; producing mechanical power or a reactive propulsive thrust / '''Wind motors'''
 |-
-| align = "center" bgcolor = "#99ccff"|2
+| align = "center"|2
 | align = "center"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=F16C F16C]
 | Engineering elements or units; general measures for producing and maintaining effective functioning of machines or installations; thermal insulation in general/ '''Shafts; flexible shafts; elements of crankshaft mechanisms; rotary bodies other than gearing elements; bearings'''
 |-
-| bgcolor = "#DCE6F1"| align = "center" bgcolor = "#99ccff"|3
+| align = "center" bgcolor = "#DCE6F1"|3
-| bgcolor = "#DCE6F1"| align = "center"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=F16H F16H]
+| align = "center" bgcolor = "#DCE6F1"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=F16H F16H]
 | bgcolor = "#DCE6F1"| Engineering elements or units; general measures for producing and maintaining effective functioning of machines or installations; thermal insulation in general / '''Gearing'''
 |-
-| align = "center" bgcolor = "#99ccff"|4
+| align = "center"|4
 | align = "center"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=F03B F03B]
 | Machines or engines for liquids; wind, spring, or weight motors; producing mechanical power or a reactive propulsive thrust / '''Machines or engines for liquids'''
 |-
-| bgcolor = "#DCE6F1"|align = "center" bgcolor = "#99ccff"|5
+| align = "center" bgcolor = "#DCE6F1"|5
-| bgcolor = "#DCE6F1"|align = "center"|[http://www.wipo.int/ipcpub/#refresh=symbol&notion=scheme&version=20110101&symbol=H02K H02K]
+| align = "center" bgcolor = "#DCE6F1"|[http://www.wipo.int/ipcpub/#refresh=symbol&notion=scheme&version=20110101&symbol=H02K H02K]
 | bgcolor = "#DCE6F1"|Generation, conversion, or distribution of electric power / '''Dynamo-electric machines'''
 |-
-| align = "center" bgcolor = "#99ccff"|6
+| align = "center" |6
 | align = "center"|[http://www.wipo.int/ipcpub/#&refresh=page&notion=scheme&version=20110101&symbol=H02P H02P]
 |Generation, conversion, or distribution of electric power / '''Control or regulation of electric motors, generators, or dynamo-electric converters; controlling transformers, reactors or choke coils'''
 |-
-| bgcolor = "#DCE6F1"| align = "center" bgcolor = "#99ccff"|7
+| align = "center" bgcolor = "#DCE6F1"|7
-| bgcolor = "#DCE6F1"| align = "center"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=H02M H02M]
+| align = "center" bgcolor = "#DCE6F1"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=H02M H02M]
 | bgcolor = "#DCE6F1"|Generation, conversion, or distribution of electric power / '''Apparatus for conversion between ac and ac, between ac and dc, or between dc and dc, and for use with mains or similar power supply systems; conversion of dc or ac input power into surge output power; control or regulation'''
 |-
-| align = "center" bgcolor = "#99ccff"|8
+| align = "center"|8
 | align = "center"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=H02J H02J]
 | Generation, conversion, or distribution of electric power / '''Circuit arrangements or systems for supplying or distributing electric power; systems for storing electric energy'''
 |-
-| bgcolor = "#DCE6F1"| align = "center" bgcolor = "#99ccff"|9
+| align = "center" bgcolor = "#DCE6F1"|9
-| bgcolor = "#DCE6F1"| align = "center"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=G06F G06F]
+| align = "center" bgcolor = "#DCE6F1"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=G06F G06F]
 | bgcolor = "#DCE6F1"| Computing; calculating; counting /'''Electric digital data processing'''
 |-
-| align = "center" bgcolor = "#99ccff"|10
+| align = "center" |10
 | align = "center"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=G05F G05F]
 | Controlling; regulating / '''Systems for regulating electric or magnetic variables'''
 |-
-| bgcolor = "#DCE6F1"| align = "center" bgcolor = "#99ccff"|11
+| align = "center" bgcolor = "#DCE6F1"|11
-| bgcolor = "#DCE6F1"| align = "center"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=H02H H02H]
+| align = "center" bgcolor = "#DCE6F1"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=H02H H02H]
 | bgcolor = "#DCE6F1"| Generation, conversion, or distribution of electric power / '''Emergency protective circuit arrangements'''
 |}

@@ Line 159: / Line 159: @@
 A majority of patents describing wind turbines or wind energy are classified in the following IPC classifications.
 {|border="2" cellspacing="0" cellpadding="4" width="100%"
-| align = "center" bgcolor = "#99ccff"|'''S.NO'''
+| align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''S.NO'''</font>
-| align = "center" bgcolor = "#99ccff"|'''IPC Classification'''
+| align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''IPC Classification'''</font>
-| align = "center" bgcolor = "#99ccff"|'''Description'''
+| align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''Description'''</font>
 |-
-| align = "center" bgcolor = "#99ccff"|1
+|bgcolor = "#DCE6F1"| align = "center" bgcolor = "#99ccff"|1
-| align = "center"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=F03D F03D]
+|bgcolor = "#DCE6F1"|align = "center"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=F03D F03D]
-| Machines or engines for liquids; wind, spring, or weight motors; producing mechanical power or a reactive propulsive thrust / '''Wind motors'''
+|bgcolor = "#DCE6F1"| Machines or engines for liquids; wind, spring, or weight motors; producing mechanical power or a reactive propulsive thrust / '''Wind motors'''
 |-
 | align = "center" bgcolor = "#99ccff"|2
@@ Line 171: / Line 171: @@
 | Engineering elements or units; general measures for producing and maintaining effective functioning of machines or installations; thermal insulation in general/ '''Shafts; flexible shafts; elements of crankshaft mechanisms; rotary bodies other than gearing elements; bearings'''
 |-
-| align = "center" bgcolor = "#99ccff"|3
+|bgcolor = "#DCE6F1"| align = "center" bgcolor = "#99ccff"|3
-| align = "center"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=F16H F16H]
+|bgcolor = "#DCE6F1"| align = "center"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=F16H F16H]
-| Engineering elements or units; general measures for producing and maintaining effective functioning of machines or installations; thermal insulation in general / '''Gearing'''
+|bgcolor = "#DCE6F1"| Engineering elements or units; general measures for producing and maintaining effective functioning of machines or installations; thermal insulation in general / '''Gearing'''
 |-
 | align = "center" bgcolor = "#99ccff"|4
@@ Line 179: / Line 179: @@
 |Machines or engines for liquids; wind, spring, or weight motors; producing mechanical power or a reactive propulsive thrust / '''Machines or engines for liquids'''
 |-
-|align = "center" bgcolor = "#99ccff"|5
+|bgcolor = "#DCE6F1"|align = "center" bgcolor = "#99ccff"|5
-|align = "center"|[http://www.wipo.int/ipcpub/#refresh=symbol&notion=scheme&version=20110101&symbol=H02K H02K]
+|bgcolor = "#DCE6F1"|align = "center"|[http://www.wipo.int/ipcpub/#refresh=symbol&notion=scheme&version=20110101&symbol=H02K H02K]
-|Generation, conversion, or distribution of electric power / '''Dynamo-electric machines'''
+|bgcolor = "#DCE6F1"|Generation, conversion, or distribution of electric power / '''Dynamo-electric machines'''
 |-
 | align = "center" bgcolor = "#99ccff"|6
@@ Line 187: / Line 187: @@
 |Generation, conversion, or distribution of electric power / '''Control or regulation of electric motors, generators, or dynamo-electric converters; controlling transformers, reactors or choke coils'''
 |-
-| align = "center" bgcolor = "#99ccff"|7
+|bgcolor = "#DCE6F1"| align = "center" bgcolor = "#99ccff"|7
-| align = "center"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=H02M H02M]
+|bgcolor = "#DCE6F1"| align = "center"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=H02M H02M]
-|Generation, conversion, or distribution of electric power / '''Apparatus for conversion between ac and ac, between ac and dc, or between dc and dc, and for use with mains or similar power supply systems; conversion of dc or ac input power into surge output power; control or regulation'''
+|bgcolor = "#DCE6F1"|Generation, conversion, or distribution of electric power / '''Apparatus for conversion between ac and ac, between ac and dc, or between dc and dc, and for use with mains or similar power supply systems; conversion of dc or ac input power into surge output power; control or regulation'''
 |-
 | align = "center" bgcolor = "#99ccff"|8
@@ Line 195: / Line 195: @@
 | Generation, conversion, or distribution of electric power / '''Circuit arrangements or systems for supplying or distributing electric power; systems for storing electric energy'''
 |-
-| align = "center" bgcolor = "#99ccff"|9
+|bgcolor = "#DCE6F1"| align = "center" bgcolor = "#99ccff"|9
-| align = "center"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=G06F G06F]
+|bgcolor = "#DCE6F1"| align = "center"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=G06F G06F]
-| Computing; calculating; counting /'''Electric digital data processing'''
+|bgcolor = "#DCE6F1"| Computing; calculating; counting /'''Electric digital data processing'''
 |-
 | align = "center" bgcolor = "#99ccff"|10
@@ Line 203: / Line 203: @@
 | Controlling; regulating / '''Systems for regulating electric or magnetic variables'''
 |-
-| align = "center" bgcolor = "#99ccff"|11
+|bgcolor = "#DCE6F1"| align = "center" bgcolor = "#99ccff"|11
-| align = "center"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=H02H H02H]
+|bgcolor = "#DCE6F1"| align = "center"|[http://www.wipo.int/ipcpub/#refresh=page&notion=scheme&version=20110101&symbol=H02H H02H]
-| Generation, conversion, or distribution of electric power / '''Emergency protective circuit arrangements'''
+|bgcolor = "#DCE6F1"| Generation, conversion, or distribution of electric power / '''Emergency protective circuit arrangements'''
 |}

@@ Line 127: / Line 127: @@
 {|border="2" cellspacing="0" cellpadding="4" width="100%"
-|align = "center" bgcolor = "#83caff"|'''Control System'''
+|align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''Control System'''</font>
-|align = "center" bgcolor = "#83caff"|'''Pitch contol'''
+|align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''Pitch contol'''</font>
-|align = "center" bgcolor = "#83caff"|'''Yaw control'''
+|align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''Yaw control'''</font>
-|align = "center" bgcolor = "#83caff"|'''Stall control'''
+|align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''Stall control'''</font>
-|align = "center" bgcolor = "#83caff"|'''Generator torque control'''
+|align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''Generator torque control'''</font>
 |-
-|rowspan="2" align = "center" bgcolor = "#83caff"|'''Description'''
+|bgcolor = "#DCE6F1"|rowspan="2" align = "center" bgcolor = "#83caff"|'''Description'''
-|A method of controlling the speed of a wind turbine by varying the orientation, or pitch, of the blades, and thereby altering its aerodynamics and efficiency.
+|bgcolor = "#DCE6F1"|A method of controlling the speed of a wind turbine by varying the orientation, or pitch, of the blades, and thereby altering its aerodynamics and efficiency.
 Source:[http://www.moog.com/markets/energy/wind-turbines/blade-pitch-control/ Blade Pitch Control]
-|The rotation of horizontal axis wind turbine around its tower to orient the turbine in upwind or down wind direction.
+|bgcolor = "#DCE6F1"|The rotation of horizontal axis wind turbine around its tower to orient the turbine in upwind or down wind direction.
 Source:[http://zone.ni.com/devzone/cda/tut/p/id/8189 Wind Turbine Control Methods]
-|Stall control works by increasing the angle at which the relative wind strikes the blades (angle of attack). As the wind speed increases drag force on the blade increase and lift force gets reduces, thus finally reduces the speed of turbine.A fully stalled turbine blade, when stopped, has the flat side of the blade facing directly into the wind. Compare with furling.
+|bgcolor = "#DCE6F1"|Stall control works by increasing the angle at which the relative wind strikes the blades (angle of attack). As the wind speed increases drag force on the blade increase and lift force gets reduces, thus finally reduces the speed of turbine.A fully stalled turbine blade, when stopped, has the flat side of the blade facing directly into the wind. Compare with furling.
 Source:[http://www.windmeup.org/2008/03/stall-control-basics.html Stall-control basics]
-|As the aerodynamic torque control changes, rotor speed changes. it changes the output power frequency. A frequency converter is connected in between generator and the network to maintain generator power constant.
+|bgcolor = "#DCE6F1"|As the aerodynamic torque control changes, rotor speed changes. it changes the output power frequency. A frequency converter is connected in between generator and the network to maintain generator power constant.
 Source[[Media:windenergycontrol.pdf|Wind Energy Control]]
 |-

@@ Line 69: / Line 69: @@
 {|border="2" cellspacing="0" cellpadding="4" width="100%"
-| align = "center" bgcolor = "#83caff"|
+| align = "center" bgcolor = "#4F81BD"|
-| align = "center" bgcolor = "#83caff"|'''Fixed speed generating systems'''
+| align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''Fixed speed generating systems'''</font>
-| align = "center" bgcolor = "#83caff"|'''Variable speed generating systems'''
+| align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''Variable speed generating systems'''</font>
-| align = "center" bgcolor = "#83caff"|'''Doubly fed induction generator'''
+| align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''Doubly fed induction generator'''</font>
 |-
@@ Line 81: / Line 81: @@
 |-
-| Machines
+|bgcolor = "#DCE6F1"| Machines
-| SQIG
+|bgcolor = "#DCE6F1"|SQIG
-| PMSG/WRSG/WRIG
+|bgcolor = "#DCE6F1"| PMSG/WRSG/WRIG
-| DFIG
+|bgcolor = "#DCE6F1"| DFIG
 |-
@@ Line 100: / Line 100: @@
 |-
-| Drawbacks
+|bgcolor = "#DCE6F1"| Drawbacks
-|  <nowiki>* </nowiki>No control on real and reactive power
+|bgcolor = "#DCE6F1"|  <nowiki>* </nowiki>No control on real and reactive power
 <nowiki>* Less optimum power extraction capability</nowiki>
@@ Line 108: / Line 108: @@
 <nowiki>* High mechanical stress on turbine mechanical components</nowiki>
-|  <nowiki>* Additional cost of power electronics</nowiki>
+|bgcolor = "#DCE6F1"|  <nowiki>* Additional cost of power electronics</nowiki>
 <nowiki>* Limited fault ride through capability</nowiki>
-| <nowiki>* Regular maintenance of slip ring and gearbox</nowiki>
+|bgcolor = "#DCE6F1"| <nowiki>* Regular maintenance of slip ring and gearbox</nowiki>
 <nowiki>* Limited fault ride-through capability</nowiki>

@@ Line 28: / Line 28: @@
 {|border="2" cellspacing="0" cellpadding="4" width="100%"
 | align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''Horizontal axis wind turbines'''</font>
-| align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''Vertical axis wind turbines''</font>'
+| align = "center" bgcolor = "#4F81BD"|<font color="#FFFFFF">'''Vertical axis wind turbines'''</font>
 |-
-|bgcolor = "##DCE6F1"|
+|bgcolor = "#DCE6F1"|
 * It is mounted on top of a tower ,requires huge towers leads to complex in operation, maintenance and high initial costs.
 * It operates only with upstream or down stream wind directions.
 * It can be constructed in off-shores.
 * It produces large amount of electricity with high efficiency.
-|bgcolor = "##DCE6F1"|
+|bgcolor = "#DCE6F1"|
 * These are easy to build and maintain, safer, easier to transport and they can be mounted close to the ground.
 * These can handle much turbulence in wind than horizontal wind turbines.