Transcript Introductory Electronics

Wind Generators
Tom Rebold
Monterey Peninsula College
[email protected]
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)
Electron Current Flow (-) to (+)
Conventional Current Flow (+) to (-)
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)
Resistors – Color Code
Resistors –Colour Code Example
3




3
102
5%
(gold)
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
Resistors – Typical Power Ratings
Ohm’s Law
“Current (I) is proportional to Voltage (V)
and inversely proportional to Resistance (R)”
V
I
R
V  I R
V
R
I
UNITS: 1 Volt across 1 Ohm produces 1 Amp of current
Calculate the current in this circuit
using Ohm’s Law
3W
I
6V
V
I
R
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
3W
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, 2002 http://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
Wind
Generator
I
P=I2R = V2/R = IV
To find the
power
delivered to
our pump,
we will
have to
measure V
and I
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
Each conversion results in a loss of power
Wind
Power
Electrical
Power
Pumping
Power
50 W
5W
1W
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=mgh
(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 determine
tension 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/bla
des_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://www.ircwcc.org/manual/PUMP/PUMPS.HTM
http://bb_ops.tripod.com/RC_Combat/Hind_Pump.htm