Wind and Wave Power. By Nelle Anderson, Jenna Raderstrong, and Ryan Heltemes

Transcription

1 Wind and Wave Power By Nelle Anderson, Jenna Raderstrong, and Ryan Heltemes

2 How a Wind Generator Works How is the energy in the wind captured? The wind is used to generate mechanical power or electricity. Wind turbines convert the kinetic energy in the wind into mechanical power. A generator can then convert this mechanical power into electricity. A wind turbine works the opposite of a fan. Instead of using electricity to make wind, like a fan, wind turbines use wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity. They are often grouped together into a single wind power plant. Electricity from these turbines is fed into local utility grids.

3 Inside A Wind Generator Anemometer: Measures the wind speed. Controller: The controller starts up the machine at wind speeds of about 8 to 16 miles per hour and shuts off the machine at about 55 mph. Turbines do not operate at speeds above about 55 mph because they might be damaged by the high winds. Gear box: Gears connect the lowspeed shaft to the high speed shaft and increase the rotational speeds from about 30 to 60 rotations per minute to about 1000 to 1800 rpm, the rotational speed required by most generators to produce electricity.

4 Calculating Wind Power Kinetic Energy= 0.5 x Mass x Velocity² Mass/sec= Velocity x Area x Density Power = 0.5 x Swept Area x Air Density x Velocity³ P = 0.5Aρv³ These equations assume that all the kinetic energy can be converted into mechanical energy, where as in a real life situation some of the kinetic energy would be converted into heat and other forms.

5 Practice Problem A wind turbine has blades 20 m long and the speed of the wind is 25 m/s on a day when air density is 1.3 kg/m³. Calculate the power that could be produced if the turbine is 30% efficient. Power = 0.5 x Swept Area x Air Density x Velocity³ = 0.5(π(20)²)( 1. 3)(25³) =13MW 13(0.3)= 3.9MW

6 Practice Problem A wind generator is being used to power a solar heater pump. If the power of the solar heater pump is 0.5kW, the average local wind speed is 8.0 m/s, the average density of air is 1.1 kg/m³, and the blades of the generator are 20 m long. Deduce whether it would be possible to power the pump using the wind generator. Power = 0.5 x Swept Area x Air Density x Velocity³ P = 0.5(π(20²))(1.1)(8.0³) P = 354 kw 354(0.3) = 106 kw It is more than enough

7 Ways to Capture Wave Energy Floats or Pitching Devices: an object is attached to a floating raft or to the ocean floor and electricity is generated from its bobbing motion. Wave Surge or Focusing Devices: shoreline devices that channel waves into an elevated reservoir. Water that flows out of this reservoir is used to create electricity, using hydropower technologies. Waves are not as consistent as the tides and therefore aren t a very reliable energy source. This is why it has only been used on a small scale. Oscillating Water Columns

8 Oscillating Water Column(OWC) Generate electricity from the rise and fall of waves in a cylindrical shaft. The movement of the water channels air out of the top of the shaft and into an air-driven turbine. Installed on shore or to the seabed

9 Wave Power -Power equals one half of the period length in seconds times the height of the wave in meters squared P=½Th² -Wave Power is measured in kw/m -Depth of the ocean must be at least twice the wave height (amplitude) - Wavelength equals velocity in meters per second times period in seconds λ = vt

10 Wave Power Example Period = 8 seconds Height = 3.0 meters P=½Th² P=(½)(8)(3.0²) P= 36 kw/m

11 Wave Power Wavelength = 9.0m Frequency = 0.1/second Height = 3.0 meters P=½Th² T = 1/f P=½(1/f)h² P = ½(1/0.1)(3.0²) P = 45 kw/m λ = vt 9.0 = (v)(1/0.1) 9.0 =10v V = 0.9 m/s

12 Energy Flow Diagrams - A directional flow chart where the width of the streams is proportional to the quantity of flow, and where the flows can be combined, split and traced through a series of events or stages -Also called Sankey diagrams -Energy flow diagram for a heat engine

13 Energy Flow Diagrams Energy Degradation Input Power Output Node Total Input = Total Output

14 Energy Flow Diagrams To create an energy flow diagram 1. Identify the source or sources of energy 2. Identify all transfers of energy 3. Identify all losses of energy (heat, sound, light, etc.) 4. The output will be all of the energy that was not lost Gravitational Potential Energy (Water) Kinetic Energy (Turbine) Electric Energy (Generator) Power Generated Sound Heat (Friction) Flow Complications Heat (Friction)