1. Solar Energy Technology Science Summer Camp
Session 9 Tuesday 9: :30 PM
Basic Electrical Theory
Lunch and Pool 11:30 AM - 2:00 PM

2. Day 2 Introduction Description of Facilities – if needed
Go Over Day 2 and rest of Course
Handout Notes

3. General Saftey Rules
Safety first
Always follow safety rules

4. Part 3 Topics Atomic structure and electrons
History of PV technology and industry trends
Potential for solar in New York, US and the World
Needs (markets) and applications for PV (grid-tie, remote homes, telecom, etc.)
Types of PV systems (direct motor, standalone with storage, grid-backup, etc.)
Key features and benefits of PV with applications 4 4

5. Review the atomic structure
Focus on flow of electrons (or ions) are what move along wires or other substances to cause an electric current.
Use marbles with "marble holder - wire" to show flow of electrons down a wire.

6. Fundamental Components of the Atom - how the relate to charge

10. How a PV Cell works Structure of PV Cell How Electrons Flow
Uses marbles with "marble holder - PV cell" to show simplified movement of electrons in PV cell.

11. Shading issues
Sun –
Radiant Energy
PV module 11

12. Silicon Atom
Four electrons in outer shell
Reference 3 12

13. Crystalline Silicon Models
Reference 2 13

14. Definitions - Electrons and Holes14

15. Step 1 – Photoelectric effect
When sunlight (photon) hits silicon atom, an electron in its outer shell can be “liberated” and start moving throughout the crystalline structure.
A “hole” with a positive charge is “left” behind at the silicon atom that lost its electron.
Recombination - Eventually free electron combines with another hole.
Reference 3 15

16. Step 2 – Doping process
Doping - Process of adding impurities to prevent
free electrons randomly “moving” in PV cell. 16

17. Addition of Phosphorus
Addition of phosphorous creates
N-type (negative) semiconductor material 17

18. Addition of Boron Addition of boron creates
P-type (positive) semiconductor material 18

19. Step 3 – Putting PV cell together19

20. Electrical Field at P/N Junction
Reference 3
Free electrons from phosphorus atom cross over to fill “holes” in boron atoms. This creates a permanent electric field at p/n junction. 20

21. Space Charge Zone
Depletion Region 21

22. Step 4 – Sunlight hits PV module and current (electron movement) occurs
Reference 3 22

23. Typical PV Cell
Reference 2 23

24. Lab 1: (from Lab 102 Exp 6) - Resistance & Ohms Law
Theory: A basic resistance circuit is the simplest circuit and is used in an ordinary flashlight. There is a battery, which acts as a constant voltage source, and a light bulb, which is in effect a special resistor. In the figure below a schematic diagram of this circuit is shown, with the various parts labeled.
I = V/R or V = IR or R=V/I

25. Overview of components of a basic circuit
Energy source: Generator, Battery, Solar Cell
Wire
Load - Resistor
Capacitor

26. Electrical Concepts Electrical Concepts
 Electricity - water flow analogy
Voltage  Current, Resistance and Capacitance
Define: Voltage  Current, and Resistance
Ohms Law V = IR
Define Capacitance
Series Versus Parallel Circuits
Addition of V  for Series Versus Parallel Circuits
Addition of R  for Series Versus Parallel Circuits
Addition of C  for Series Versus Parallel Circuits
Describe DC versus AC Current

27. Current Flow of electrons (negative charge) through a circuit
Measured in terms of electron flow per time
Units =
1 Amp =Amps 6 x 1018 electrons per second
Symbol = ‘I’ 27

28. Voltage Pressure pushing electrons through circuit Electric Potential
Units = Volts
Symbol = “V” 28

29. Water Analogy
Voltage = The “height” tank that pushes water through a circuit
Current = The “gallons per minute” of water flowing through a circuit 29

30. Power Power = Rate of delivery of energy
Power = Current (I) x Voltage (V)
Units = Watts or kilowatts 30

31. Energy Energy = Work done by electricity Energy = Power (watts)
x Time (Hours)
Units = watt-hours or kWh 31

32. IV Curves
PV module Current-Voltage Curve
For all electrical devices, the power that they supply or consume is the product of the potential across the device and the current that flows through the device.
Reference 3 32

33. Types of Electricity Direct Current (DC)
Voltage and Current are Constant over Time
Electrons flow in one direction only
DC Power Sources
Batteries
DC Generators
Photovoltaic (PV) modules
Etc. 33

34. Power Factor
AC loads such as motors, compressors, etc. cause current and voltage wave forms to be out-of-sync with each other. The degree that the two wave forms are out-of-sync is measured by a phase angle, phi. The cosine of phi is called the Power Factor (PF). In a typical residence, the power factor is from 0.8 to 0.9 34

35. Types of materials
Conductors are those substances in which the outer electrons (typically only one or two in each atom) can move freely from one atom to the next
Insulators are substances in which all the electrons in the atoms of the substance are tightly bound. The electrons do not easily move from one atom to the next.
Semi-conductors is a general term for a class of substances which allow current to flow, but in a limited or controlled fashion. 35

36. Resistance
Measure of opposition to flow of electrons through a conductor
Resistance lowers the voltage in a conductor but not the current
Resistance = Voltage / Current
Units = Ohms 36

37. Ohm’s Law 37

38. Series Combinations of Resistance

39. Current Flow Notation / Different Conventions
Historic in nature. Used by electrical engineers and engineering text books
Reflect actual electron flow. Used in introductory texts and by scientists 39

40. Parallel Combinations of Resistance
1/Req = 1/Rl + 1/R2 + 1/R3

41. DC Circuits Series Circuits
Voltage is additive, current remains the same
Parallel Circuits Current is additive, voltage remains the same 41

42. Resistivity of a Wire
Resistivity is just the inverse of conductivity. We use the symbol σ for the conductivity, and ρ for resistivity. Thus σ = 1/ρ and R = resistance of a wire = ρL/A
L = Total length of the wire, A = cross-sectional area of the wire

44. Lab 2: (from Lab 102 Exp 5) – Capacitors & Dielectrics
Theory: A capacitor or condenser is a passive electronic component consisting of a pair of conductors separated by a dielectric. When a voltage potential difference exists between the conductors, an electric field is present in the dielectric. This field stores energy and produces a mechanical force between the plates. One of the main uses of capacitors is to store static charge. The relationships among:
Capacitance (C), Charge (Q) , Voltage difference (V)
Plate Area (A), Plate Separation (d), Dielectric Constant (εo) = 8.85 x10-12C2/Nm2.
in a parallel plate capacitor can be summarized by two equations
C = Q/V and C = εoA/d

45. Capacitors in Series
Ceq = 1/Cl + C2 + C3

46. Resistors in Parallel
Ceq = Cl + C2 + C3

47. Lab 3: (from Lab 102 Exp 7) – The Wheatstone Bridge
Theory: The Wheatstone Bridge circuit is used to determine the unknown resistance Rx of a resistor. This is done by adjusting the relative values of the R1 and R2 until the galvanometer reads zero, and the balance condition is met. In our apparatus, R1 and R2 are made of a single piece of high resistance wire 1 m long. Figure A shows the basic Wheatstone Bridge and figure B is how the circuit is arranged on the apparatus you will be using.

48. Wheatstone Bridge

49. Color Codes for Resistors
Digit
Multiplier
Black 1
Yellow 4
104
Gray 8
108
Brown 10
Green 5
105
White 9
109
Red 2
102
Blue 6
Orange 3
103
Violet 7
107

50. Lab 4: (from Lab 102 Exp 8) – DC Circuit Analysis
Theory: In this experiment we'll explore in more detail how Ohm's law determines the volt­age drops across and currents through resistors in various resistance circuits. This experiment also gives us a convenient opportunity to explain a little bit about the importance of fuses and light bulbs in general.
Circuit Analysis
We'll apply a few simple rules to study some simple circuits. Our basic goal will be to understand how the current flow is divided up between the multiple possible paths between the
+ and - terminals in the battery.
Series Circuits
Parallel Circuits

52. DC Circuit Calculations
Series Circuits
V total = V1 + V2 + V3+ V4
Current is constant
Parallel Circuits
I total= I1 + I2 + I3+ I4
Voltage is constant
Reference 3 52

54. Build DC Circuits Build galvanic cell - maybe hold off until Wed?
Build circuits,  make calculations using V = IR
Use 3 power sources
Hand generator
Battery
Solar Cell

55. Alternating Current (AC)
Current and voltage are constantly changing from positive to negative in value of time. Change in values represented as a sinusoidal curve.
Cycle – One complete change from positive to negative values
Frequency (Hertz) = Number of Cycles per Seconds
Household AC power typical is 120/240 V AC at 60 Hz 55

56. Root Mean Square (RMS) “Effective” AC current and voltage
Can apply Ohm’s Law
V (RMS) = I (RMS) x R
RMS = x Peak
Peak = 1.41 x RMS
Peak to Peak = 2 x Peak
170Volts
120 Volts 56

57. Types of AC Loads Resistive Loads Incandescent Lights
Resistance Heaters
Power factor = 1
Reactive Loads Motors Compressors Capacitors Power factor < 1 57

58. Apparent and Real AC Power
Power (apparent) = I (RMS) x V (RMS) However, current and wave forms, may be peaking at different times, therefore the “instantaneous” power (I x V) will not be the same as the “time average” power. We use the Power Factor (PF) to calculate the “real” power used by an AC motor load, Power (real) = I (RMS) x V (RMS) x PF of device 58

59. Current and Voltage Curves
Resistive Load PF=1
Reactive Load PF<1 59

60. Real and Apparent Power
Reactive Loads
Real Power = Power used by in circuit. Expressed in “Watts”.
Apparent Power = Power supplied to circuit. Expressed in “kVA”
Power = Real Power
Factor Apparent Power 60

61. Main Load Center
Reference 5 61

62. Symbols 62

63. Lunch and Pool 11:30 AM - 2:00 PM