1. Solar Energy Technology Science Summer Camp
Session 7 Thur AM
System Components and Configurations

2. Day 3 Introduction Description of Facilities – if needed
Go Over Day 2 and rest of Course
Handout Notes
Review Safety Rules
Safety first
Always follow safety rules

3. Session 7 Topics Overview of System Components Activities: Cells
Modules
Arrays
 Inverters
Batteries
Charge Controllers 
Activities:
Consider:  Construct and observe basic galvanic cell
TBD 3 3

4. Shading issues
Sun –
Radiant Energy
PV module 4

5. Stand Alone PV System Components PV Array/Modules
Junction / Combiner Box
Charge Controller
Inverter
Batteries 5

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

9. How PV Cells, Modules and Arrays Work9

10. Solar Array Components
Cells
Modules
Panels
Arrays
Reference 1 10

11. PV Cell
A solar cell is a device that converts the energy of sunlight directly into electricity by the photovoltaic effect. Sometimes the term solar cell is reserved for devices intended specifically to capture energy from sunlight such as solar panels and solar cells, while the term photovoltaic cell is used when the light source is unspecified. Assemblies of cells are used to make solar panels, solar modules, or photovoltaic arrays.

12. PV Module
A photovoltaic module or photovoltaic panel is a packaged interconnected assembly of photovoltaic cells, also known as solar cells. The photovoltaic module, known more commonly as the solar panel, is then used as a component in a larger photovoltaic system to offer electricity for commercial and residential applications.

13. PV Array
A photovoltaic array is a linked collection of photovoltaic modules, which are in turn made of multiple interconnected solar cells. By their modularity, they are able to be configured to supply most loads.

15. 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.

16. Silicon Atom
Four electrons in outer shell
Reference 3 16

17. Crystalline Silicon Models
Reference 2 17

18. Definitions - Electrons and Holes18

19. 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 19

20. Step 2 – Doping process
Doping - Process of adding impurities to prevent
free electrons randomly “moving” in PV cell. 20

21. Addition of Phosphorus
Addition of phosphorous creates
N-type (negative) semiconductor material 21

22. Addition of Boron Addition of boron creates
P-type (positive) semiconductor material 22

23. Step 3 – Putting PV cell together23

24. 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. 24

25. Space Charge Zone
Depletion Region 25

26. Step 4 – Sunlight hits PV module and current (electron movement) occurs
Reference 3 26

27. Typical PV Cell
Reference 2 27

28. Crystalline Silicone
Polycrystalline
Monocrystalline
Reference 2 28

29. Thin Film Cell Examples
Reference 2 29

30. Differences in Cell Type Efficiencies30

31. Advantages / Disadvantages of Cell Types
Crystalline Silicone
Highest cell efficiencies
Well established manufacturing technology
Durable product
Thin Film Cells
Con’s
Less efficient than crystalline silicon
Harder to control / MPPT tracking devices
(flatter IV curve)
Pro’s
Wider spectral response (sunlight wavelengths)
More efficient at low irradiance levels
Use less energy and material to produce
More flexible than crystalline silicone
More tolerant of shading issues 31

32. Typical PV Module Construction
Reference 2 32

33. Typical PV module energy losses
Typical Polycrystalline Cell Efficiency
PV output = to 15%
Solar Irradiance
3% - Reflection and shading by
front contacts
23% - Insufficient photon energy
of long-wave radiation
32% - Surplus of photo energy
of short wave radiation
8.5% - Recombination losses
20% - Electrical gradient in cell,
especially in space charge zone
0.5% - Due to serial resistance
(electric heat loss)
Reference 2 33

34. Impact of shading on PV array performance34

35. PV Inverter
A Solar inverter or PV inverter is a type of electrical inverter that is made to change the direct current (DC) electricity from a photovoltaic array into alternating current (AC) for use with home appliances and possibly a utility grid.
Solar inverters may be classified into three broad types:
* Stand-alone inverters, used in isolated systems where the inverter draws its DC energy from batteries charged by photovoltaic arrays and/or other sources, such as wind turbines, hydro turbines, or engine generators. Many stand-alone inverters also incorporate integral battery chargers to replenish the battery from an AC source, when available. Normally these do not interface in any way with the utility grid, and as such, are not required to have anti-islanding protection.
* Grid tie inverters, which match phase with a utility-supplied sine wave. Grid-tie inverters are designed to shut down automatically upon loss of utility supply, for safety reasons. They do not provide backup power during utility outages.
* Battery backup inverters. These are special inverters which are designed to draw energy from a battery, manage the battery charge via an onboard charger, and export excess energy to the utility grid. These inverters are capable of supplying AC energy to selected loads during a utility outage, and are required to have anti-islanding protection
Solar inverters use special procedures to deal with the PV array, including maximum power point tracking and anti-islanding protection.

36. PV Inverter

37. Inverter Functions
Convert DC power from solar array into AC household power
Change voltage levels
A) Grid-tied systems
Up to 600 VDC to 240 VAC,
B) Grid-tied with battery backup From 12, 24, 48 VDC to 120 VAC
Provide maximum power point tracking (MPPT) according to IV curve. 37

38. Types of Inverters
1. Grid-Dependent – Inverter provides power to household loads or grid during daylight hours. No storage
2. Bi-Directional – Performs like grid-dependent inverter but also has ability to charge stand-by batteries. Can charge batteries from PV modules or utility grid.
3. Stand-Alone – Inverter designed to operate independently of the grid. Energy stored in batteries. Remote sites. 38

39. Energy Conversion and Storage
Shading issues
Sun –
Radiant Energy
PV module 39

40. Batteries
A voltaic cell for demonstration purposes. In this example the two half-cells are linked by a salt bridge separator that permits the transfer of ions, but not water molecules

41. Battery System Components
Grid-Tied with Battery Backup (Hybrid)
Stand Alone PV Systems
PV Systems 41

42. Batteries
Function
Store energy from PV array for when it is needed by household loads.
Provide stable power supply to loads upon demand (stable voltages / suppress transients)
Provide surge currents to electrical loads (motors, etc).
Reference 2 42

43. Electron Flow from Negative plate to positive plate
Battery Cell Components
Active materials
PbO2 (positive electrode)
Pb (negative electrode)
Grid
Plate (grid and active material)
Separator
Electrolyte (diluted sulfuric acid, H2SO4)
Case
Vent
Chemical reaction occurs between the active materials on the plate and the electrolyte) 43

44. Lead Acid Cell Chemical Reaction (reversible)
Electrons used “up” at positive plate
Electrons “released” at negative plate 44

45. Batteries will deteriorate over time
Sulphation – Small quantities of lead sulphate (PbSO4) do not redissolve when battery is charged
The greater the “depth of discharge”, the greater the loss of capacity due to sulphation.
Stratification – Electrolyte concentration stratifies due to insufficient charging and gassing
Leads to severe negative grid corrosion and, hence loss of battery capacity.
Overcharging can lead to water (H20) being hydrolyzed into hydrogen (H2) and oxygen (O2) which escape from the battery in the form of gas. Leads to H2SO4 concentration and stratification 45

46. Charging Terminology
Battery Capacity – Measure in Amp-hours. Usually given at C20 discharge rate (battery total discharged over 20 hours)
Autonomy – Days of battery storage without additional PV array input
State of Charge (SOC) – Percentage of energy stored in battery.
Depth of Discharge (DOD) – Percentage of capacity that has been drawn down from full battery
Battery cycles – Number of times that a battery has been drawn down to a specified level of discharge. 46

47. Battery capacity (Amp-Hrs) changes with time to discharge47

48. Depth of discharge vs. battery life
Gel
Wet 48

49. charge controller
A charge controller, charge regulator or battery regulator limits the rate at which electric current is added to or drawn from electric batteries. It prevents overcharging and may prevent against overvoltage, which can reduce battery performance or lifespan, and may pose a safety risk. It may also prevent completely draining ("deep discharging") a battery, or perform controlled discharges, depending on the battery technology, to protect battery life. The terms "charge controller" or "charge regulator" may refer to either a stand-alone device, or to control circuitry integrated within a battery pack, battery-powered device, or battery recharger.