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Wind Generators. Tom Rebold Monterey Peninsula College trebold@mpc.edu. Need to know… . Basic Electricity Measurements Power Calculations Power in wind, electricity, and movement of water Wind Tower Design (engineering statics) Wind generator blade design (aerodynamics)

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## Wind Generators

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**Wind Generators**Tom Rebold Monterey Peninsula College trebold@mpc.edu**Need to know…**• Basic Electricity Measurements • Power Calculations • Power in wind, electricity, and movement of water • Wind Tower Design (engineering statics) • Wind generator blade design (aerodynamics) • Water Pump Design (hydraulics)**Electrity: Three Main Invisible Quantities**• Voltage, V, Volts • Provides the “push” • Current, I, Amperes (Amps) • Flow of Electrons • Amount of Current is dependent on Voltage and Resistance • Resistance, R, Ohms (W) • Limits the amount of current**Safe Levels**• Voltage: 30 V • Voltages inside a computer do not exceed 12 V, except at the power supply and power switch, which are at 120 V.Be careful in these areas! • Current: 5 mA (0.005 Amperes)**Voltage Can Be Provided From…**• A battery**Voltage Can Be Provided From…**• A generator**Current**• …is simply the flow of electrons • Direction depends on convention • Electron flow is from (-) to (+) (flow of electrons) • Conventional flow is from (+) to (-) (hole flow)**Resistors – Basic Specs**• Can be rated by… • Resistance (Ohms, W) • Tolerance (% of nominal value) • Power Rating (Watts) • Schematic Symbol…**Resistors – Types**• Fixed • Variable (Potentiometer, Rheostat)**5%**(gold) 3 3 102 Resistors –Colour Code Example • 1st band: orange = 3 • 2nd band: orange = 3 • 3rd band: red = 2 (i.e. 102) • 4th band: gold = 5% 33 x 102 = 3300 W = 3.3 k W**Ohm’s Law**“Current (I) is proportional to Voltage (V) and inversely proportional to Resistance (R)” UNITS: 1 Volt across 1 Ohm produces 1 Amp of current**Calculate the current in this circuit using Ohm’s Law**3 W I 6V**Calculate the current in this circuit using Ohm’s Law**1.5 W I 6V**Calculate the current in this circuit using Ohm’s Law**3 W I 3V**Calculate the current in this circuit using Ohm’s Law**300 W I 6V**How Many Volts across Resistor?**300 W 2A**Ohm’s Law, Including Power**Reproduced by permission of Tony van Roon, 2002http://www.uoguelph.ca/~antoon**How Many Watts dissipated by Resistor?**300 W 2A P=I2R**How Many Watts dissipated by Resistor?**1.5 W I 6V P=I2R = V2/R = IV**For your Wind generator, same calculations apply**Water Pump To find the power delivered to our pump, we will have to measure V and I I Wind Generator P=I2R = V2/R = IV**Complete System Drawing**10 ft wire Pump Fuse**Wind and Hydro Power Calculations**• How much power is in the wind? • How much power does it take to pump a liter of water 2 m uphill in 5 minutes? • How can we evaluate how effective our wind system is at pumping water?**Engineering a Power Conversion System**Wind Electrical Pumping Power Power Power Each conversion results in a loss of power 50 W 5 W 1 W This system has an overall efficiency of 1/50 or 2% In subsequent designs, engineers would try to improve the efficiency**The Power in the Wind**• From basic physics we have “Kinetic Energy” • K = ½ M V2 • K = energy in Joules (or N-m, or even KW-hr) • M = mass, kg • V = velocity of object, m/s • In the context of wind, we can determine the mass of the cylinder of air that hits our generator in a certain time interval. • Power is the amount of Kinetic Energy we capture divided by the time we are gathering it. ( Watts)**Hydraulic Power**• In order to pump a mass m kg of water h meters uphill, we require an amount of energy equal to • E = m g h (Joules) where g = 9.8 m/s2 • To pump uphill in T seconds, would require a power of • P = E/T (Watts) • Suppose m = 1 kg, d = 2 m, T = 60 s • P = 1 x 9.8 x 2 / 60 = .3 W**Tower Design**• In ENGR 8 You can determinetension in cables! • Keep tower simple. 2x4 with 4 cords attached to stakes • Mount motor using steel bands and screws**Thoughts on Propeller Blade Design**• http://www.practicalaction.org/docs/energy/blades_manual.pdf**Balance**• By all means, make sure you balance your blades before testing! • Use some small weights, coins, anything to make sure the blades are evenly weighted. • Otherwise your generator could quickly destroy itself!**Pump Construction**http://bb_ops.tripod.com/RC_Combat/Hind_Pump.htm • http://www.ircwcc.org/manual/PUMP/PUMPS.HTM

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