1. Wind Generators Tom Rebold Monterey Peninsula College trebold@mpc.edu

2. 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)

3. 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 (  ) ▫Limits the amount of current

4. 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)

5. Voltage Can Be Provided From… A battery

6. Voltage Can Be Provided From… A generator

7. 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)

8. Resistors – Basic Specs Can be rated by… ▫Resistance (Ohms,  ) ▫Tolerance (% of nominal value) ▫Power Rating (Watts) Schematic Symbol…

9. Resistors – Types Fixed Variable (Potentiometer, Rheostat)

10. Resistors – Color Code

11. Resistors –Colour Code Example 3310 2 5% (gold) 1 st band: orange = 3 2 nd band: orange = 3 3 rd band: red = 2 (i.e. 10 2 ) 4 th band: gold = 5% 33 x 10 2 = 3300  = 3.3 k 

12. Resistors – Typical Power Ratings

13. 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

14. Calculate the current in this circuit using Ohm’s Law 3  6V I

15. Calculate the current in this circuit using Ohm’s Law 1.5  6V I

16. Calculate the current in this circuit using Ohm’s Law 3  3V I

17. Calculate the current in this circuit using Ohm’s Law 300  6V I

18. How Many Volts across Resistor? 2A 300 

19. Ohm’s Law, Including Power Reproduced by permission of Tony van Roon, 2002 http://www.uoguelph.ca/~antoonhttp://www.uoguelph.ca/~antoon

20. How Many Watts dissipated by Resistor? 2A 300  P=I 2 R

21. 1.5  6V I P=I 2 R = V 2 /R = IV How Many Watts dissipated by Resistor?

22. Water Pump Wind Generator I P=I 2 R = V 2 /R = IV For your Wind generator, same calculations apply To find the power delivered to our pump, we will have to measure V and I

23. Complete System Drawing Fuse Pump 10 ft wire

24. 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?

25. Engineering a Power Conversion System Wind Electrical Pumping PowerPowerPower 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

26. The Power in the Wind From basic physics we have “Kinetic Energy” ▫K = ½ M V 2  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)

28. 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/s 2 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

30. Tower Design In ENGR 8 You can determine tension in cables! Keep tower simple. 2x4 with 4 cords attached to stakes Mount motor using steel bands and screws

31. Thoughts on Propeller Blade Design http://www.practicalaction.org/docs/energy/bla des_manual.pdfhttp://www.practicalaction.org/docs/energy/bla des_manual.pdf

32. 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!

33. Pump Construction http://www.ircwcc.org/manual/PUMP/PUMPS.HTM http://bb_ops.tripod.com/RC_Combat/Hind_Pump.htm