IB Wind and Wave Power

Mark Kapron, Luc LaLonde, Scott Johnstun

Wind Power

• A wind generator is commonly know as a wind turbine.

• Unlike a fan, producing wind with the help of electricity, the wind turbines produce electricity with the help of wind.



How Do They Work?

• A gust of wind blows through the blades of the turbine causing it to rotate, which creates large amounts of kinetic energy.

• This kinetic energy turns a shaft, which in turn turns the generator and creates electrical energy.

Power Generated by Wind

• Albert Betz was a German physicist who in 1919 concluded that no wind turbine can convert more than 16/27 (59.3%) of the kinetic energy of the wind into mechanical energy turning a rotor. To this day this is known as the Betz Limit or Betz' Law. This limit has nothing to do with inefficiencies in the generator, but in the very nature of wind turbines themselves.

Proof?

But seriously…

• You can’t convert all of the kinetic energy in the area of the circle that the blades cover because some of the wind will pass through without interacting with the system.

Problem Solving Wind

• Wind power = 1/2 x Swept Area x Air Density x Velocity3 • The world's largest wind turbine generator has a rotor

blade diameter of 126 meters and a rotor sweep area of 12470 m2. The turbines are also moving at a speed of 14m/s. Find the power produced by the turbines.

• The air is situated at sea level, so it equals = 1.23kg/m3

Wind Power = 0.5 x 12,470 m2 x 1.23 kg/m3 x (143) m3/s3

• Wind power = 21,000,000 Watts or 21 MW.

Not Drawn to Scale

Part 2: Wave Power

• Clean energy produced by using the power of oceanic waves. Around the world, day and night, waves produce a tremendous amount of untapped energy. Methods of harnessing this energy are being discovered rapidly.

Various Methods to Harness Wave Energy

Methods to Harness the Energy

This is the Oscillating Water Column Method

More on the OWC

• About 36 kW of power potential per 1 meter wave front.

• You must assume a rectangular profile of the wave, since waves are not rectangular this potential cannot be reached.

Wave Energy Problems• The best place to put these devices is usually in the

areas of the ocean with the strongest waves, but these places are also the most difficult to set up the generators, and maintain them.

• Oceanic waves are generally too slow (frequency) to rotate a turbine efficiently.

• The electric cables that bring the energy to the mainland could also be a possible threat to sea life. Tests on this are currently being conducted to see if it would really be a problem.

• Like wind turbines, wave energy converting devices are currently expensive.

Yes, that says friction…

Wave Energy Equation

• Power Per Unit Length=0.5A2ρgv• A= Area of the waves cross-section• ρ= Density of water• g= 9.8 m/s2

• v= Velocity of the wave

• You might also see the potential energy stored in one wavelength as Ep=.5A2λρgL

Proof

Sample Problem

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