2. 2
Solar energy
• Promising technology
• Latitude and temperature
True North Power, Ontario
• Azimuth trackers
• Wind & solar
• Customers’ concerns
• Need to assess different configurations
3. I) State of the art
1) Passive and active trackers
2) One axis and double axis trackers
3) Limits of the technology
II) Solar radiation model
Two solar models: Orgill and Pérez
III) Computation of the solar model
1) Solar data
2) Different simulations
3) Modification of the model
IV) Results of the simulation
1) Slope and azimuth of double axis tracker
2) Radiation on panel
V) Discussion
VI) Conclusion
3
4. 1) Passive and active solar trackers
Passive
• Gas under partial pressure
• Memory of shape of an alloy
• Temperature dependant
• Bad with changing weather
4
Active
• Time-based: from solar equations and modeling
• Experimental: optical sensors
• Optimization
• Not weather dependant
The identical tubes are filled with gas
5. 2) Single and double-axis trackers
Single-axis
• Different configurations
• Fixed slope
• Rotation 2° every 8min
• Around 28% energy gain
5
Double axis
• Rotation of two axis: azimuth+slope
• Energy gain>40% around sunrise and sunset
• Around 32% energy gain
6. 3) Limits of the technology
Possible improvement of azimuth tracker
• Monthly hand-tilting = 3.1% energy gain
• One hour step = 99.75%
• Two hour step = 98.80%
• Two step tracker = 95%
6
• Double axis = 5-6% gain against 2-3% consumption of
total energy due to addition of a motor
• Costs and maintenance
• Cloudy days: diffuse radiation only
of continuous
azimuth tracking
Continuous Two step
Fixed tilt
9. 1) Solar data
• Queen’s University, Kingston
• One minute measurement of solar horizontal radiation for 2011
• 44.225°N 76.495°W
2) Different simulations
• Fixed South facing panel with optimum slope
• Azimuth tracker with ∆az=1° and optimum slope
• Double-axis tracker with ∆az=1° and ∆β=[1,2,5,10°]
• Perfect continuous tracker θ=0°
9
10. 3) Modification of the model
• Problem at sunrise and sunset, assumption: Ibeam=0 and Idiffuse=Iground
• Two cases: Pérez model + Liu & Jordan for Zenith angle > 85° or Pérez model
all the time
10
Orgill
model
Pérez
model
Pérez
model
Liu &
Jordan
model
Zenith angle > 85°Zenith angle ≤ 85°
OR
Ipanel
Ipanel
11. 1) Slope and azimuth of double axis
11
Δaz=Δβ=1°
12. 2) Radiation on panel
12
Pérez + Liu & Jordan when Zenith angle>85°
Continuous 100,00% 132,54%
Two axis with ∆az=1°
1° 99,99% 132,53%
2° 98,87% 131,04%
5° 98,78% 130,92%
10° 98,48% 130,52%
One axis ∆az=1° fixed slope 50° 97,14% 128,75%
Fixed slope 0° south 34° 75,45% 100,00%
• Two-axis tracker increases energy gain from 28.75% to 32.53%
compared to fixed panel facing south
• Only 1.73% gain of two-axis over one-axis with Δβ=2°
• Maximum gain of 2.85% with a very accurate tracking
13. 13
Use of Pérez + Liu & Jordan
• Received radiation for Zenith angle>85° represents only 1.96% of total
radiation on horizontal surface on earth.
• Comparison with 5 other sites in the USA with 43°<latitude<45.5° and
70°<longitude<83°
Syracuse, New York
Rochester, New York
Concord, New Hampshire
Burlington, Vermont
Massena, New York
• Fixed panel: consistent slope of 34°
USA sites
Queen’s
University
Two-axis
tracker 32.9% 32.53%
Azimuth
tracker 28.8% 28.75%
Energy gain over fixed south facing panel
Queen’s University:
44.225°N 76.495°W
14. 14
Uncertainty of the solar model
• 6.7% difference between use of Pérez or use of Pérez + Liu & Jordan for
continuous tracking
• High resolution data: error around sunrise and sunset & 5W/m² measurement
precision
• Geography of the site: top of a mountain? Shadow?
Feasibility of addition of a second axis
• 2.85% energy gain of two axis over azimuth tracker against 2% motor
consumption. Need of battery?
• 2.85% with very accurate tracking. Use of the motor
• Additional costs and maintenance
15. 15
Is it worth adding a second axis?
• Small energy gain
• Big uncertainty in solar models
• Additional costs
Solar tracker = optimized PV panels
• Gain of a few percent
• Better in sunny weather
• No need for perfect tracking
