1. Cloud Shadow Speed Sensor
The Future of Solar Forecast Technology
Ed Chen, National Tsing Hua University, Taiwan
Ricardo Vidrio: UC LEADS/UCSD STARS
Mentor: Dr. Juan Luis Bosch
PI: Dr. Jan Kleissl
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2. Opening Question Think about this
If we cover 30% of the Nevada area with solar power
plant, can we power the whole US?
Copper Mountain Solar 1
• Solar photovoltaic power plant in Nevada
• Area: 468 acres = 1.894 km2
• Annual Production: ~124,000 MWh/year
• Electrical Power Production in the US in 2012
= 4.048 x 109 MWh/year
• Nevada area: 286,367 km²
•
286,367×0.3
1.894
× 124,000 𝑀𝑊ℎ
𝑦𝑟 =5.625 × 𝟏𝟎 𝟗 𝑴𝑾𝒉
𝒚𝒓
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3. Introduction
Our way of life is not green
Solar Energy Engineering’s Challenge
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4. We all want renewable energy,
but there are some pros and cons.
• Pros
• Environmental friendly
• Avoid using fossil fuel
• Cons
• Generally more expensive than
unrenewable energy.
• Unstable dynamic output.
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5. We all want renewable energy, but
It’s usually more expensive.
Levelized Costs Of Energy
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6. We all want renewable energy, but
Output of renewable energy is usually unstable.
Output vs. time graph
SolarWind
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7. • Cons
•Generally more expensive than
unrenewable energy.
Fossil fuel will be more expensive in
the long run
Solar forecasting technology
•Unstable dynamic output.
Solar forecasting technology
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8. Why can’t we power the whole
US with only Solar Energy?
• Output Variation
• Day & Night
• Sunny & Cloudy
• Loss in Long Distance Transmission
• Cable Resistance
• Transformer Efficiency
• Energy Storage
• Store energy at day time for night time usage.
• Battery efficiency.
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9. Solar Energy Engineering’s Challenge
Changing cloud cover is a major source of solar
radiation variability, and pose challenges for the
integration of solar energy.
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10 kw Solar Panel Output in different situation
id10t naïve sunny cloudy
kW
hours
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10. Possible Solutions
for Dynamic Output of Solar Power
A. Build more solar power plant, so that we can still have high output in
cloudy day.
expensive, occupy spaces. Not practical at all.
B. Construct energy storage system, so that we can store energy when
it’s sunny, and release the energy when it’s cloudy.
a little expensive, energy loss. Not very practical.
C. Predict the solar output in the next few hours, so that
we can use other energy source to compensate the drop
off.
need solar energy forecasting technology, can
intergrade with current electric grid. Practical.
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11. How to
Predict the solar output in the next few hours?
A. Ask someone to monitor the cloud all day.
Not precise, tiring. Not practical at all.
B. Use Doppler radar to measure the velocity of clouds.
 Too expensive($200,000), cloud speed and direction
doesn’t totally represent cloud shadow. Not practical
at all.
C. Build a cheap system to gather the data of sky image
and cloud shadow speed.
Acceptable.
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12. Solar Forecast Technology
Goal:
Predict the solar output in the next few minutes or hours in
order to compensate the incoming drop off with other
adjustable energy sources and keep the electric grid stable.
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13. 14
USI
CSS
CSSCSS
CSS
CSSCSS
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14. CSS
Cloud Shadow Speed Sensor
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• Cheap feasible way to predict short term
cloud speeds and direction
• Estimated cost ~ $400
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15. The layout of the CSS
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16. The Cross Correlation Method
We need this to find our highest correlated
time lag between all nine sensors
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17. USI
UC San Diego Sky Imager
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18. Flood of Data
• Three persons team assigned to complete
spreadsheets such as this one
Date Multiple Cloud Layers Cloud Changed? Cloud Cover Cloud Direction
12/1/2013 no/no/no no 75/45/25 SW/SSW/SW
12/2/2013 no/no/no no 85/90/95 WSW/SW/WSW
12/3/2013 yes/no/no no 95/95/90 SSW/SSW/SSW
12/4/2013 no/yes/no no 35/65/55 WSW/WSW/SW
12/5/2013 no/no/no no 60/65/0 SW/SSE/NA
12/6/2013 no/no/no no 30/65/10 S/S/SSE
12/7/2013 no/no/yes no 95/100/85 W/WSW/W
12/8/2013 yes/yes/yes yes 95/40/85 WSW/S/W
12/9/2013 no/no/no no 40/75/65 W/WSW/WSW
12/10/2013 no/no/no yes 45/35/53 SSE/S/S
12/11/2013 yes/yes/no yes 30/55/85 NNE/SSE/SE
12/12/2013 no/no/no no 15/0/0 N/NA/NA
12/13/2013 no/no/no no 25/25/20 SW/SW/WSW
12/14/2013 no/no/no no 0/0/0 NA/NA/NA
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19. Was watching the videos worth
it?
• How far we were from one another
Month
(Morn) Person 1 Person 2 Similarity
DEC 217.1 219.6 98.50%
JAN 223 219 98.20%
FEB 223 219 98.20%
MARCH 224.1 216.3 96.60%
APRIL 221 202.5 91.70%
MAY 168.8 172.5 97.80%
JUNE 176.9 189.6 93.30%
JULY 221.5 183.2 82.70%
Month
(Evening) Person 1 Person 2 Similarity
DEC 0.13 0.13 100%
JAN 0.25 0.21 83.30%
FEB 0.26 0.35 75%
MARCH 0.3 0.37 81.80%
APRIL N/A N/A N/A
MAY 0.065 0.16 40%
JUNE 0.069 0.21 33.30%
JULY 0.4 0.53 75%
Cloud Direction Multiple Layer of Clouds
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20. The CSS Data
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21. Comparing the CSS and USI
• Some of our results are illogical. This makes sense,
and will take time to analyze
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1/2/2014 Morn
CD (CSS) CD (USI) #1 CD (USI) #2 Cloud Cover #1 Cloud Cover #2
No Cloud No Cloud 337.5/NNW 0% 5%
1/2/2014Afternoon
CD (CSS) CD (USI) #1 CD (USI) #2 Cloud Cover #1 Cloud Cover #2
No Cloud No Cloud 292.5/WNW 0% 10%
1/2/2014 Evening
CD (CSS) CD (USI) #1 CD (USI) #2 Cloud Cover #1 Cloud Cover #2
No Cloud 292.5/WNW 292.5/WNW 20% 10%

22. References(1/2)
• Fung, Victor, Juan Luis Bosch, and Jan Kleissl. "Cloud Shadow Speed Sensor."
Atmospheric Measurement Techniques, 2014: 1693 - 1700.
• Bosch, Juan Luis, and Jan Kleissl. "Cloud Motion Vectors from a network of
ground sensors in a solar power plant." Center for Renewable Resources and
Integration, 2013.
• Kent. Kent Solar Panels. 2011. http://uk-solarpanels.blogspot.com/
(accessed August 11, 2014).
• Wile, Rob. Business Insider. May 29, 2012.
http://www.businessinsider.com/chart-heres-why-renewable-energy-has-
miles-to-go-before-it-leaps-into-mainstream-2012-5 (accessed August 9,
2014).
• Levelized Cost of New Electricity Generating Technologies. n.d.
http://instituteforenergyresearch.org/wp-
content/uploads/2011/02/Levelized-Cost-of-New-Electricity-Generating-
Technologie11.pdf (accessed August 8, 2014).
• Zyga, Lisa. PHYS ORG. April 9, 2011. http://phys.org/news/2011-04-
energy_1.html (accessed August 8, 2014).
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23. References(2/2)
• US energy use chart shows we waste more than half of our energy
http://phys.org/news/2011-04-energy_1.html
• http://www.caiso.com/outlook/systemstatus.html
• Why Expanded Alternative Energy Increases the Need for Natural Gas
http://theenergycollective.com/jemillerep/178096/expanded-wind-and-solar-
power-increase-need-natural-gas
• Why is The Peak Output of Solar Panels So Low? Why do my solar panels
generate less than their rating?
http://uk-solarpanels.blogspot.com/2012/05/solar-panels-low-peak-
output.html
• CHART: Here's Why Renewable Energy Has Miles To Go Before It Leaps Into
Mainstream
http://www.businessinsider.com/chart-heres-why-renewable-energy-has-miles-
to-go-before-it-leaps-into-mainstream-2012-5
• Levelized Cost of New Electricity Generating Technologies
http://instituteforenergyresearch.org/wp-content/uploads/2011/02/Levelized-
Cost-of-New-Electricity-Generating-Technologie11.pdf
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24. Acknowledgements
• UC LEADS
• UCSD STARS
• University System of Taiwan
• National Tsing Hua University
• Summer Research International Undergraduates
• Victor Fung (Creator of CSS)
• Prof. Jan Kleissl
• Dr. Juan Luis Bosch
• Dominic Fong
• Joel Zahnd
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25. 26
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Questions
Thank You