1
Grid Effects of Cloud-Induced Variation
in Solar Photovoltaic Generation
Ward Jewell
Wichita State University
Power Systems Engineering Research Center
wardj@ieee.org
PSERC
Cost of PV Generated
Electricty (cents/kWh)
2
23
22
21
20
19
18
17
Year
September 2010:
– Modules: $4.08 / W
PSERC
-- Inverters: $0.715 / W
SolarBuzz Solar Electricity Prices, Sept. 2010, www.solarbuzz.com/SolarPrices.htm
3
3000
Full sun
load
Load (MW)
2500
2000
1500
solar
1000
500
0
1 3 5 7 9 11 13 15 17 19 21 23
Time Period (hour)
PSERC
Piyasak Poonpun, Effects of New Low Carbon Emission Generators and Energy Storage on Greenhouse
Gas Emissions in Electric Power Systems, PhD Dissertation, Wichita State University, 2009.
80
70
60
50
40
30
20
10
0
Solar (MW)
PV vs. demand
3000
2500
2000
1500
1000
500
0
wind
100
80
60
40
20
0
load
1 4 7 10 13 16 19 22
Wind Output (MW)
Load (MW)
4
Wind vs. Demand
wind
1 4 7 10 13 16 19 22
Time Period (hour)
PSERC
100
80
60
40
20
0
3000
2500
2000
1500
1000
500
0
load
wind
1 4 7 10 13 16 19 22
Time Period (hour)
Piyasak Poonpun, Effects of New Low Carbon Emission Generators and Energy Storage on Greenhouse
Gas Emissions in Electric Power Systems, PhD Dissertation, Wichita State University, 2009.
100
80
60
40
20
0
Wind Output (MW)
load
Load (MW)
3000
2500
2000
1500
1000
500
0
Wind Output (MW)
Load (MW)
Time Period (hour)
5
December 2
Sunlight
varies
Full sun
Partly cloudy
December 5
December 6
Cloudy
PSERC
R. Ramakumar, Ward Jewell, et al, “Issues in Utility Interactive Photovoltaic Generation,”
IEEE Power Engineering Review, Vol. 14, No. 4, April 1994, pp. 19-21.
6
Operating Reserves
Typical capacity credits
– Coal, nuclear, natural gas, oil, hydro: 100%
– Solar 60-90%
– Geothermal 80-100%
– Wind 20-40%
PSERC
7
Cloud Modeling
Statistical model, small cumulus clouds
PSERC
Ward Jewell, R. Ramakumar, "Insolation Model for Simulation of an Electric Utility with High Penetration of Dispersed
Photovoltaic Generation," Proceedings of the International Solar Energy Society Biennial Congress. June 1985.
8
Simulated cloud pattern for
50% shadow cover
PSERC
Ward Jewell, R. Ramakumar, "Insolation Model for Simulation of an Electric Utility with High Penetration of Dispersed
Photovoltaic Generation," Proceedings of the International Solar Energy Society Biennial Congress. June 1985.
9
Distributed PV Systems
PSERC
Ward Jewell, R. Ramakumar, "Insolation Model for Simulation of an Electric Utility with High Penetration of Dispersed
Photovoltaic Generation," Proceedings of the International Solar Energy Society Biennial Congress. June 1985.
10
Resulting Insolation
PSERC
Ward Jewell, R. Ramakumar, "Insolation Model for Simulation of an Electric Utility with High Penetration of Dispersed
Photovoltaic Generation," Proceedings of the International Solar Energy Society Biennial Congress. June 1985.
11
When a squall line moves across an
area with PV, all PV generation is lost
PSERC
Ward Jewell, R. Ramakumar, "The Effects of Moving Clouds on Electric Utilities with Dispersed
Photovoltaic Generation," IEEE Transactions on Energy Conversion, December 1987, pp. 570-576.
12
When clouds are moving over an area
with PV, PV generation varies rapidly
Maximum PV Variability
(% per minute)
PSERC
Ward Jewell, R. Ramakumar, Stanton Hill, "A Study of Dispersed Photovoltaic Generation on the
PSO System,“ IEEE Transactions on Energy Conversion, Vol. 3, No. 3, September 1988, pp. 473-478.
13
When clouds are moving over an area
with PV, PV generation varies rapidly
Example:
• 1000 km2 (about 400 mi2) service area
• 200 MW distributed PV
• 200 MW x 3%/minute = 6 MW/minute change
PSERC
Ward Jewell, R. Ramakumar, Stanton Hill, "A Study of Dispersed Photovoltaic Generation on the
PSO System,“ IEEE Transactions on Energy Conversion, Vol. 3, No. 3, September 1988, pp. 473-478.
14
Power Flow Modeling
Public Service of Oklahoma (AEP) southeast Tulsa area
(450 square kilometers)
PSERC
Ward Jewell, R. Ramakumar, Stanton Hill, "A Study of Dispersed Photovoltaic Generation on the
PSO System,“ IEEE Transactions on Energy Conversion, Vol. 3, No. 3, September 1988, pp. 473-478.
15
Power Flow Results
Public Service of Oklahoma (AEP) southeast Tulsa area
PSERC
Ward Jewell, R. Ramakumar, Stanton Hill, "A Study of Dispersed Photovoltaic Generation on the
PSO System,“ IEEE Transactions on Energy Conversion, Vol. 3, No. 3, September 1988, pp. 473-478.
16
Power Flow Results
Public Service of Oklahoma (AEP) southeast Tulsa area
15 % distributed PV can cause:
• Transmission power flow reversal
• Transmission overloads
under certain conditions
PSERC
Ward Jewell, R. Ramakumar, Stanton Hill, "A Study of Dispersed Photovoltaic Generation on the
PSO System,“ IEEE Transactions on Energy Conversion, Vol. 3, No. 3, September 1988, pp. 473-478.
17
Production Cost
Unit commitment and economic dispatch
For a system that is ramp-rate limited
to 1% of load per minute:
One PV generator with capacity =
1.3% of load
may exceed system ramp rate under
certain cloud conditions.
PSERC
Ward Jewell, Timothy D. Unruh, "Limits on Cloud Induced Fluctuation from Photovoltaic
Generation," IEEE Transactions on Energy Conversion, Vol. 5, No. 1, March 1990, pp. 8 14.
18
Ramp rate limited system
Fluctuation in PV Output
(% of installed PV
capacity per minute)
1% of load per minute
PSERC
50
45
40
35
30
25
20
15
10
5
0
2
4
6
8
PV Penetration
(% of installed generation)
Ward Jewell, Timothy D. Unruh, "Limits on Cloud Induced Fluctuation from Photovoltaic
Generation," IEEE Transactions on Energy Conversion, Vol. 5, No. 1, March 1990, pp. 8 14.
10
19
Optimal Power Flow
dispatch, LMPs, emissions
PSERC
Miaolei Shao , Ward Jewell; “CO2
Emission-Incorporated AC Optimal
Power Flow and Its Primary Impacts
on Power System Dispatch and
Operations,” 2010 IEEE Power and
Energy Society General Meeting,
Minneapolis, July 2010.
20
No PV
CO2 $0/ton
300 MW (9%) PV
CO2 $50/ton
PSERC
300 MW (9%) PV
CO2 $0/ton
System
Dispatch
Piyasak Poonpun, Matthew Riddel, and Ward Jewell, “Solar
Generation Prospects and Effects on System Optimal Power
Flow,” 2009 Frontiers of Power Conference, Stillwater,
Oklahoma, October 2009.
21
No PV
CO2 $0/ton
300 MW (9%) PV
CO2 $0/ton
300 MW (9%) PV
CO2 $50/ton
Marginal Prices
PSERC
at PV bus
22
Changes in system operating cost
CO2 $0/ton
PSERC
Piyasak Poonpun, Matthew Riddel,
and Ward Jewell, “Solar Generation
Prospects and Effects on System
Optimal Power Flow,” 2009
Frontiers of Power Conference,
Stillwater, Oklahoma, October 2009.
CO2 $50/ton
23
Changes in CO2 emissions
CO2 $0/ton
PSERC
CO2 $50/ton
Piyasak Poonpun, Matthew Riddel, and Ward Jewell, “Solar Generation Prospects and Effects on System
Optimal Power Flow,” 2009 Frontiers of Power Conference, Stillwater, Oklahoma, October 2009.
24
Energy Storage to Relieve Congestion
Bus 24 storage schedule
Storage output (MW)
Zhouxing Hu, Ward Jewell, Optimal Power Flow Analysis of Energy Storage for Congestion
Relief, Emissions Reduction, and Cost Savings, submitted to IEEE PES 2011 Power Systems
PSERC Conference and Exhibition, September 2010.
25
Operations with storage
Zhouxing Hu, Ward Jewell, Optimal Power Flow Analysis of Energy Storage for Congestion
Relief, Emissions Reduction, and Cost Savings, submitted to IEEE PES 2011 Power Systems
PSERC Conference and Exhibition, September 2010.
26
Research supported by
Power Systems Engineering Research Center
(pserc.org)
Kansas Electric Utilities Research Program
Public Service of Oklahoma (AEP)
Ward Jewell
Wichita State University
Power Systems Engineering Research Center
wardj@ieee.org
PSERC