Changes

| align = "center" bgcolor = "#83caff4F81BD"| <font color="#FFFFFF"> '''Onshore wind turbines'''</font>| align = "center" bgcolor = "#83caff4F81BD"| <font color="#FFFFFF"> '''Offshore wind turbines'''</font>

* Easily intergrated integrated with the electrical- grid network

* Less affected to turbulance turbulence in wind and low wind shear<br/>

| bgcolor = "#DCE6F1"| Disadvantages* Neagtive Negative visual impact or noise.* Limted avaliability Limited availability of lands* Restrictions asscociated associated with obstructions like buildings, mountains, etc.

* Afftected Affected to more turbulanceturbulence

| bgcolor = "#DCE6F1"| Disadvantages:* Installing offshore windturbines wind-turbines is much more complex and costly

* Operation and maintanances maintenance is also a complex task with off shore wind turbines

A tower that supports the nacelle and rotor hub at its top. These are made from tubular steel, concrete, or steel lattice. Height of the tower is an important in design of HWAT. Because wind speed increases with height, taller towers enable turbines to capture more energy and generate more electricity. Generally output power of the wind system increase with increase in height and also reduces the turbulance turbulence in wind. The theoritical theoretical view of tower height versus power out is shown in figure 7 .click on the link to get more about size of the towers  <font size="2">''' [[Wind Turbine Tower Size]]'''</font>

| align = "center" bgcolor = "#83caff4F81BD"|<font color="#FFFFFF">'''Different types of wind turbine towers'''</font>| align = "center" bgcolor = "#83caff4F81BD"|<font color="#FFFFFF">'''Structure'''</font>

|bgcolor = "#DCE6F1"|'''Tubular Tower: '''They are constructed from rolled steel plates welded together with flanges top and bottom, being sprayed with several coats of gray weatherproof paint at the construction yard. They have doors top and bottom allowing entrance to the vertical ladders inside used to access the power cables and the yaw mechanism. There are also a set of vertical ladders on the outside of the tower accessing the nacelle for maintenance and other checks.|bgcolor = "#DCE6F1"|[[Image:turbular.jpeg|200px|center|thumb|Fig 8(a) [http://americanrenewableenergycorp.com/towers Tubular tower]]]

| '''Lattice tower''': A Lattice tower can be constructed with perfectly shapped shaped steel rods that are put together to form a lattice. These towers are very strong and inexpensive to manufacture and easy to transport and erect.

|bgcolor = "#DCE6F1"| '''Guyed wind tower''': These are very strong and most economical when properly installed. But it requires more space around the tower for guy wires|bgcolor = "#DCE6F1"|[[Image:guyed.jpeg|center|200px|thumb|Fig 8(c) [http://itgiproducts.com/energy/windTowers.asp Guy tower]]]

| '''Tilt up wind towers:'''These type of towers are used for consumer wind energy. These turbines have locking system, while working the turbine is locked. It can easily ulocked locked and lowered to ground to perform repairs.

|bgcolor = "#DCE6F1"| '''Free standing tower:'''These can be used for small wind turbines with cautions.|bgcolor = "#DCE6F1"| [[Image:free.jpeg |center|thumb|Fig 8(e) [http://itgiproducts.com/energy/windTowers.asp Free stand tower]]]

| align = "center" bgcolor = "#99ccff4F81BD"|<font color="#FFFFFF">'''Single blade HAWT'''</font>| align = "center" bgcolor = "#99ccff4F81BD"|<font color="#FFFFFF">'''Two blade HAWT'''</font>| align = "center" bgcolor = "#99ccff4F81BD"|<font color="#FFFFFF">'''Three blade HAWT'''</font>

|bgcolor = "#DCE6F1"| It reduces the cost and weight of the turbine. These are rarely used due to tower shadow effects, needs counter weights on the other side of the blade, less stability.|bgcolor = "#DCE6F1"| It requires more complex design due to sustain of wind shocks. It is also less stable. It saves the cost and weight of one rotor blade.|bgcolor = "#DCE6F1"|Modern wind turbines uses three blade concept. Because this structure have hight strength to withstand heavy wind storms. Less effect due to tower shadow. Produces high output|-|[[Image:single.jpeg|center|200px|thumb|Fig 9(a) [http://www.wind-energy-the-facts.org/en/part-i-technology/chapter-3-wind-turbine-technology/evolution-of-commercial-wind-turbine-technology/design-styles.html Single blade turbine]]] | It requires more complex design due to sustain of wind shocks. It is also less stable. It saves the cost and weight of one rotor blade.[[Image:two.jpeg|center|300px|thumb|Fig 9(b) [http://www.trendir.com/green/?start=15 Two blade turbine]]]|Modern wind trubines uses three blade concept. Because this structure have hight strength to withstand heavy wind stroms. Less effect due to towe shadow. Produces high output[[Image:three.jpeg|center| 200px|thumb|Fig 9(c) [http://www.china-windturbine.com/wind-turbines-blades.htm Three blade turbine]]]

. Rotor hubs are made with welded sheet steel, cast iron, fored forged steel. The types of rotor hubs are * Hingeless Hinge-less hub

Wind speed is the most important factor for determing determining the power content in the wind. The power content in the wind is directly proportional to cube of the wind velocity. Measuring wind speed is important for site selection. The device which is used for measuring wind speed is called anemometer. These are usally usually located on top of the nacelle.