2. Energy, Power, and Climate Change 8.8 Wave Power W AVES  Common water waves are produced by the sun-driven winds passing over the water's surface.  The height of the waves depends on the following three factors:  The speed of the wind  The duration of the wind  The fetch

3. Energy, Power, and Climate Change 8.8 Wave Power F ETCH FYI: The FETCH is the length of the water over which the wind passes. FYI: A NNE wind on Lake Michigan produces a much larger amplitude... than a west wind. FYI: The course of the Edmund Fitzgerald on Lake Superior.

5. L Energy, Power, and Climate Change 8.8 Wave Power P OWER IN A W ATER W AVE  The power of a water wave is complicated to calculate, so we'll simplify it some.  Think of the crest as storage of potential energy, and the falling water as conversion into kinetic energy. A

6. L Energy, Power, and Climate Change 8.8 Wave Power P OWER IN A W ATER W AVE U = mgh U = mgA/2 A U =  VgA/2 A/2 FYI: The AVERAGE HEIGHT of the water is A / 2. U =  LAgA/2 U =  LgA 2 /2 FYI: This much potential energy is converted into kinetic energy each period T. = VT K =  LgA 2 /2 K =  VTLgA 2 /2 FYI: Power is energy per time: P =  gVLA 2 2 Power Generated By A Wave FYI: Power is proportional to the SQUARE of the AMPLITUDE A. Power is proportional to the WAVE SPEED V. Power is porportional to the LENGTH of the WAVEFRONT L.

7. Energy, Power, and Climate Change 8.8 Wave Power P OWER IN A W ATER W AVE Waves having an amplitude of 2 m roll onto a beach at a rate of one every 8 seconds. The wave crests are 75 meters apart. (a) What is the wave velocity? V = d/t = /T = 75/8 = 9.75 m/s (b) How much wave power is there, per unit length? P =  gVLA 2 2 P / L =  gVA 2 2 = (1000)(10)(9.75)2 2 2 = 195 kW/m (c) How much wave power is there along 25 km of beach? FYI: The mass density of water is 1000 kg/m 3. P = (195 kW/m)L P = (195 kW/m)(25000 m) P = 4875 MW

8. Energy, Power, and Climate Change 8.8 Wave Power P OWER G ENERATION FROM A W ATER W AVE THE OSCILLATING WATER COLUMN Air Column - Compressed and rarefied by rising and falling wave. Wind Turbine Generator Turbine generates both ways

9. Energy, Power, and Climate Change 8.8 Wave Power P OWER G ENERATION FROM A W ATER W AVE THE PELAMIS  The pelamis is named after the sea snake for obvious reasons.  Each of four sections is hinged to the previous one.  Fluid inside moves back and forth.  The moving fluid drives a generator. FYI: A pelamis can generate 750 kW of power.