1. Solar Energy Technology Science Summer Camp
Session 2 Monday 12:30 - 3:00 PM
Site Selections Factors 1

2. Session 2 Topics
Solar Radiation and Geometry (as part of a site assessment).
Basic Definitions
Son - Earth Relationships
Solar angle effect on irradiance
True vs. magnetic north and south
Solar Charts and diagrams 2 2

3. Basic Definitions Basic solar terms
Radiance - the amount of radiation leaving or arriving at a point on a surface
Radiation - the process in which energy travels through a medium or through space
Irradiance - the rate of light energy striking a given area of surface in a given amount of time
Types of irradiance: Global, Direct and Diffuse
Irradiation - the amount of solar energy that falls on the surface over time is called irradiation. This is the ENERGY density of solar radiation. It is measured in kilowatt-hours/square meter/day
Langley, a unit of solar radiation; equal to one calorie per square centimeter.
Radiation
Activity 2-1 In: Use Flashlight to Trace Terms 3
12:35 PM 3

4. Conversions Example: Convert 1000 Langleys per day to kWh/m2/day
To convert from……
Into….
Multiply by….
Langley (calorie/cm2)
kWh/m2
Btu/ft2
Mj/m2
0.2777
Example: Convert 1000 Langleys per day to kWh/m2/day
1000 Ly/day ( kWh/m2/Ly) = kWh/m2/Ly/day
12:37 PM

5. Earth - Sun Relationships
Sun Angle has a significant effect on the irradiance reaching a solar array
Higher angle more solar energy reaches array
Seasonal differences
Diurnal (daily) changes
Earth Orbit (year) versus Earth Rotation (day)
rotations per one orbit around sun
Tilt of earth on axis and Orbit cause of Seasons
Note: sun farther away during NH summer
We will Experiment with globe and flashlight

6. Orbit and Tilt the Cause of the Seasons
Sun’s Path
Reference 4 6

7. Seasons and Distance From Sun

8. Position of sun changes during year
Earth’s travel around the Sun as seen back here on Earth
Reference 2 8

9. Rotation Cause of the Day-Night Cycle

10. Azimuth Angle – Angle of Sun’s east-west position.90
180
Reference 4
12:45 PM
Activity 2-2 In : Use Flashlight to Illustrate Solar Angle on globe by time of day and season 10

11. Peak Sun Hours
Reference 4 11

12. 0 Atm
~1.5 Atm

13. Factors that Affect Surface Irradiance
Solar Angle:
Experiment that measures of solar angle changes and irradiance values
Use solar car to discover relationship of position of the sun to the power generated by solar panels.
Atmospheric conditions:
Clouds, Haze, Dusts, Humidity, Temperature
Temperature impact on solar performance cool panel with dry ice then warm up see degradation of performance.
Shading:
Determine effect of horizon on solar irradiation (shading)
Shading will cause disproportionate degradation of performance
Irradiation effects of various surfaces
Darker more absorbed
Temperature impact on solar performance cooler more

14. Factors affecting solar radiation
Angle of incident
Clouds
Snow, Rain, Fog, etc.
Dust particles
Air pollution
Reflective materials 14

15. Result of Factors US Solar Energy Distribution
Reference 3
12:55 PM 15

16. Global Declination Field
Global Declination Field is the difference of true from magnetic north 16

17. Magnetic vs. True North Pole
Magnetic North
changes with time
Daily Movement
~53 mi
1000 km (600 mi) last 100 years

18. Correction for Mag to True North18

19. Where is “Truth South”? http://www.magnetic-declination.com/
Must correct compass reading based on magnetic declination
About 13.5 degrees to the west of 0 correction in the Utica area (-13.5)
True = compass + declination
To correct for Utica = compass
Historic Changes of Declination: 19

20. Declination Calculation http://www.ngdc.noaa.gov/geomag/
Activity 2-3 In: Demo of finding
declination angle using online
calculator.
Declination calculator:
1:05 PM
Activity 2-4 In: Now Demo of finding True North using Compass and Without compass. 20

21. Finding True North with a Compass
Online Link
Must correct compass reading based on magnetic declination
About 13.5˚ to the west of 0 correction in the Utica area (-13.5˚)
True = compass + declination
To correct for Utica:
True North = Compass N ˚
360˚ Compass Mag N = True North 346.5˚
60˚ Compass Mag = True 46.5˚
10˚ Compass Mag = True ˚
Note if answer is negative add 360˚
10˚ ˚ + 360˚ = - 4.5˚ + 360˚ = 356.5˚ N

22. Finding True North Without a Compass
Method 1
At solar noon find the shadow of a straight up and down stick - it will point due north
Solar noon:
Method 2
Place a stick upright in the ground so that you can see its shadow.
Mark the tip of the shadow with a small object, such as a pebble, or a distinct scratch in the ground.
Wait minutes. Mark the new position of the shadow's end. The shadow tip will move mostly from west to east in a curved line.
Draw a straight line in the ground between the two marks. This is an approximate east-west line.
Other Methods
Watch - Point the hour hand at the sun. N is ½ distance to 12
Stars - Locate the North Star (Polaris) in the night sky. The North Star is the last star in the handle of the Little Dipper constellation. If you have trouble finding it, find the Big Dipper. The two lowest stars in the Big Dipper (the outermost stars of the cup of the dipper) form a straight line that "points" to the North Star. N

23. Watch Method 12 3 6 9
True N

24. Be Careful! Inconsistency in PV industry
Compass Bearings are not the same as Azimuth Angles
1:10 PM
Reprinted from “Photovoltaic Systems, Jim Dunlop and Todd Stafford, ATP Publication, 2007” 24

25. Site Assessment How Much Sun?
Altitude Angle – Angle of Sun above the horizon
Theoretical Max Irradiance based upon clear sky is a function of latitude
Actual Irradiance is a function of:
(1) Cloudiness and other atmospheric conditions
(2) Shading (3) Roof pitch and orientation from south
Sun Angle 25

26. Site Assessment Shading Issues
Sun - Radiant Energy
Cloud 26

27. Solar Path - Sun Chart Diagram
Activity 2-5 In: Predict solar position using solar path diagrams
Given time of day and time of year find solar elevation angle 27

28. Sun Chart Diagrams and Shading 28

29. Solar Pathfinder Solar Pathfinder Video
Activity 2-6 In: Demonstrate use of Solar Pathfinder For Shade Analysis
A good way to analyze the sun’s path across a surface is using a Solar Pathfinder
Solar Pathfinder Home
Solar Pathfinder Video
Note show 5 min video at end of class 29

30. Pathfinder Solar Chart

31. Shading Analysis
Solar Pathfinder and Shading Analysis 31

32. Shading Analysis Nickerson House Example
Roof slope = 30 degrees 32

33. Shading Analysis Nickerson Solar Pathfinder33

34. Pathfinder Exercise Solar Chart

35. Nickerson Shading Analysis
Max Solar Fraction
0.88 means 12% lost due to shading 35

36. Additional Information
Information needed in addition to Solar Pathfinder for Shading Analysis
1. PV system size (Ex kW)
2. Solar Radiation Data
(Peak Sun Hours)
From Location (Lat/Lon)
3. Orientation - Magnetic Declination (Ex -14.5˚)
4. Roof Slope (5 :12) for Tilt of Collector
1:20 PM 36

37. Roof Pitch to Roof Angles
In NY 6 inches in 12 inches is good
Chart for
Conversion of Roof Pitch to Roof Angles
Tan Angle = Rise/Run
Sin Angel = Rise/Hyp
Y = Rise
Angle
X = Run
Note: Solar Cell = 4.3 "
So multiply by rise 2.79 to use table
Rise/Run converters: 37

38. Rise/Run - Angle Table % rise / run = rise/run x 100% How to use:
Measure your rise over run
Multiply by 100
Go to the % rise / run
Interpolate and Estimate Angle
Example: % rise/run = 6/12 x 100%
= 50%
50% is between and 57.7
Halfway would be 27.5 deg
It is a little closer to so ~27 deg

39. Energy Production Adjustments for Orientation and Tilt Angle
Reference 4
150˚
230˚
180˚
Annual Solar Irradiation (kWh/m2) in Berlin as function of azimuth (x) and tilt angle (y) 39

40. Adjustments for Orientation
Energy Production
Adjustments for Orientation
and Tilt Angle 40

41. Nickerson Power Analysis - All Factors41

42. Solar Pathfinder Solar Pathfinder Video
Activity 2-6 In: Demonstrate use of Solar Pathfinder For Shade Analysis
A good way to analyze the sun’s path across a surface is using a Solar Pathfinder
Solar Pathfinder Home
Solar Pathfinder Video
1:25 PM 42 42

43. Outside Activities 1:35 - 3:00 PM
Break into groups - (Select someone to present results)
Activity 2-1 Out 1:35 - 1:45 PM: Measure True North (Glenn & Vince):
- Using compass (on the path finders)
- Watch (Use handout)
- Measurement with stick procedures. (Need ski poles and rock markers) - Note initial at 12:20 PM
Activity 2-5 Out 1:45 - 2:10 PM: Solar Pathfinder Exercise (Vince)
- Prepare hand drawn pathfinder solar path diagram – discuss shading analysis - (More Wed or Thur)
Activity 2-2 Out 2:10 - 2:55 PM: Solar Angle: Experiment with solar angle changes and irradiance impact
- Use solar car to discover relationship of position of the PV panel with respect to the sun to the power generated by solar panels.
- Race cars - calculate speed over course
- Variation: (1) Tilt Angle (2) Orientation to Sun (3) Impact of Shading
Activity 2-3 2:45 - 3:00 PM Out: Impact of Atmospheric Conditions: Clouds, Haze, Dusts, and Tree Shading
- Shade cells observe changes - degradation of performance of cars/fans etc. 43 43

44. Inside Activities
Break up into 3 groups - (Select someone to present results)
Inside:
Activity 2-1-in: Use Flashlight to Trace Terms Basic solar terms
Activity 2-2 in: Use Flashlight to Illustrate Angle
Effect of sun's angle on irradiance (solar power)
- Seasonal differences and Diurnal changes
- Experiment with globe and flashlight
Activity 2-3 in: Materials: need globe or large beach balls, basket balls good
Predict solar position using solar path diagrams
Activity 2-4 in: Go over use of Solar Pathfinder or sun charts
Experiment with pathfinder 44 44

45. Outside Activities
Break into 3 groups - (Select someone to present results)
Activity 2-1 Out: Measure True North (Glenn & Vince):
- Using compass (on the path finders)
- Watch (Use handout)
- Measurement with stick procedures. (Need ski poles)
Activity 2-2 Out: Solar Angle: Experiment with solar angle changes and irradiance values/impact
- Use solar car to discover relationship of position of the PV panel with respect to the sun to the power generated by solar panels.
- Race cars - calculate speed over course
Activity 2-3 Out: Impact of Atmospheric Conditions: Clouds, Haze, Dusts, and Tree Shading
- Shade cells observe changes - degradation of performance of cars/fans etc.
Activity 2-4 Out: Temperature impact on solar performance (May not be able to do this)
- cool panel with dry ice then warm up. See degradation of performance with higher temperature.
Activity 2-5 Out: Solar Pathfinder Exercise (Vince)
- Prepare hand drawn pathfinder solar path diagram – discuss shading analysis
Activity 2-6 Out: Calculate Potential Electrical Energy Production
- Using Roof Slopes
Group 1 Slope is 0 degrees (horizontal PV module),
Group 2 Slope is 6:12
Group 3 Slope is 10:12. Group 4 : Slope is 57 degrees from the horizon
- Calculate Shading Percentages, Daily Peak Sun-Hours, Monthly Power Production (DC kWh) and Annual Energy Production (kWh)
Activity 2-7 Out: Project: Graphing Heat Absorption
Activity 2-8 Out: Heat absorbing capacity of different colors and backgrounds
Activity 2-9 Out: Radiant water heat loss experiment 45