Wind turbines 02/23/16
Wind turbines are one of my favorite parts of Engineering. Wind turbines work by transferring energy from the wind into a spinning shaft (mechanical energy) which rotates a generator which converts all of that into electrical energy. There are two types of wind turbines, vertical axis and horizontal axis. In the latter, the larger profile allows it to catch more wind but the tower is higher and it is more complicated to build, while the former is easier to build/design/maintain but catches less energy as an offset. The part of the turbine that catches wind with blades and converts it to mechanical energy is called the rotor. One possible design for a wind turbine is known as the drag design, which uses a turbine whose axis of rotation is perpendicular is to the movement of the wind to catch the drag force provided by the wind as energy. This design is slower moving but provides a heavier torque, making it useful for tasks such as lifting water or hay 9 your stereotypical dutch farm activities) A more modern design is the lift design, which uses a rotor facing the wind movement to use the lift force caused by an asymmetric blade profile. Lift based mechanisms have a much higher rotation speed than drag types and therefore make excellent candidates for electricity generation.
The number of blades on a wind turbine can have a multitude of effects on a wind generation system. Increasing the number of blades increases efficiency at a diminishing rate. Going from one to two blades gives us a 6% increase in efficiency while going from two to three blades gives us a 3 percent efficiency. typically, the less amount of blades, the lower material and torque needed. Rotor blades are always twisted to account for a changing angle of attack, explaining the curved structure. The theoretical power generated by a wind turbine is given by the equation Power = 1/2**A*v3, with being the wind density Abeing the area of the profile andvbeing the wind velocity. The Betz limit is the theoretical efficiency of a wind turbine, given at 59.3 percent. However, most commercial systems operate at around 10-30 percent.
Wind turbines have contain a generator which converts mechanical energy into electrical energy, and transmission which increases the rotation rate of a generator to accomplish an efficient electricity generation rate. The cut in speed is the speed in which a turbine will generate usable power, typically between 7 -15 mph. The Rated speed is the speed in which a wind turbine will generate it’s designated power, typically at around 25-25 mph. To account for dangerously high wind speeds at around 45-80 mph, most wind turbines have a cut out speed feature which shuts down the wind turbine using a versatile repertory of methods. Tower heights are usually two to three times the blade diameter to account for efficiency.