1. System Function and Design
Solar Photovoltaics
System Function and Design

2. How does Solar PV work?
Ted Talk on Solar Photovoltaic

3. Solar Cell N-type contains phosphorus with ‘extra’ electrons
P-type contains boron with ‘extra’ holes

4. Solar Cell Photons provide energy for electrons to flow into circuit
Photons provide energy for holes to move into position to accept electrons from circuit

5. Solar Systems Each cell = 1-2 Watts
Cell connected together into modules/panels
Modules/panels connected together into rooftop array
Commercial cell = 8-22% efficient
Current Max Efficiency = 46-48% (very expensive)

6. Solar Systems Modules/panels = 36-98 cells Residential usually 60
Commercial usually 72
Modules/panels connected together into rooftop array
Rooftop array = panels
Average 2000 ft2 home
Varies due to local conditions
Latitude
Weather/cloud cover

7. Solar Systems Electricity is produced ‘on demand’
Conversion from DC to AC is critical
Storage is difficult and inefficient
Not all systems have storage

8. System Design Solar cells are most efficient in direct light
Photons more concentrated/less diffuse
The sun does not stay in one position
How to optimize for this discrepancy?

9. Optimizing System Design
Sun’s angle varies and can’t be manipulated:
Latitude
Season
Time of day
Solar panel angle can manipulated:
Maximize 90º relationship with sun
Fixed or Tracking?

10. Optimizing System Design
Measure maximum output
At 90º light source to panel angle
Vary source angles
Sun altitude angle (between table top and center of light)
Based on realistic changes
Latitude, season, time of day
Vary panel angles

11. Optimizing System Design
Set angle based on latitude
Larkspur = 37.9º N
Determine angle for noon on:
Summer solstice
Winter solstice
Spring/Fall Equinox
Reduce angles (from above) to represent:
Early morning/late afternoon
Mid-morning/mid-afternoon