Leading the World’s Sustainable Energy Future
Mahesh Morjaria, Ph.D. VP, PV Systems Development
Flexible Solar Power: Unlocking Solar’s Full Potential
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• Utility-scale PV Plants provides Essential Reliability Services & Grid Flexibility
• Combined with Storage, Solar provides Clean & Competitive Firm Capacity
• Utility-scale PV Solar contributes to Grid Stability & Reliability
Solar Power Provides Energy, Flexibility and Capacity
Solar Provides Essential Reliability Services
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Solar Can Provide Reliability Services
http://www.caiso.com/Documents/TestsShowRenewablePlantsCanBalanceLow-CarbonGrid.pdf
• NERC identified essential reliability services to integrate higher levels of renewable resources, including: — Frequency Control — Ramping capability or flexible capacity
2018 Intersolar Outstanding Project
Winner
2017 NARUC Award Winner
Utility Industry Innovative Pilots or
Demonstration Projects
• Reduces need for conventional generation — Goes beyond simple PV energy value
— Enables additional solar
— Reduces need for expensive storage
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170
180
190
200
210
220
230
0 200 400 600 800 1000 1200 1400
RELATIVE TIME (sec)
Available MW Min allowed MW Commanded MW Measured MW
Solar Plant Follows Grid Operator Commands (AGC) Very Accurately
• Source: http://www.caiso.com/Documents/TestsShowRenewablePlantsCanBalanceLow-CarbonGrid.pdf. AGC: Automated Generator Control
POW
ER (M
W)
MORNING
30MW Headroom
Available MW
Measured Power
Commanded
Power (4 s)
Regulation is ~27 %pts more accurate than best
conventional generation
10 min
20 min
300 MW PV Plant
Solar Contributes to System Flexibility
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0%
5%
10%
15%
20%
25%
30%
35%
0% 5% 10% 15% 20% 25% 30%
Sola
r Cur
tailm
ent
(% o
f Pro
duct
ion
Pote
ntia
l)
Annual Solar Penetration Potential (%)
Solar Curtailment Increases with Solar Penetration
2000 MW Solar
17% Curtailed
1200 MW Solar
~1% Curtailed
2400 MW Solar 31%
Curtailed
1600 MW Solar
6% Curtailed
Source: E3,TECO, First Solar Report “Investigating the Economic Value of Flexible Solar Power Plant Operation”, https://www.ethree.com/wp-content/uploads/2018/10/Investigating-the-Economic-Value-of-Flexible-Solar-Power-Plant-Operation.pdf .
~5 GW Peak Load
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As real time approaches…
Operational Flexibility Needed to Balance System While Managing Variability & Forecast Uncertainty
Load (MW)
Load Forecast
X Time Ahead
Headroom: Resources increase output
Actual Load could increase...
Footroom: Resources decrease output
Actual Load could decrease...
Time = 0
Lower solar generation...
Headroom Required
Higher Solar Generation
Footroom Required
Solar Forecast
11
Head and Foot Room are Needed to Ensure Operational Control
Forecast accuracy increases
Operational flexibility decreases
Week Ahead Day Ahead Hours
Ahead 5 Min Ahead
5-min Load
Up
war
d
(MW
of
inc)
D
own
war
d
(MW
of
dec
)
Forecast Load
Headroom
Footroom
Forecast Error
Forecast Load
Regulation
Forecast Error
Regulation
Headroom
Footroom
Forecast Error
Regulation
Headroom
Footroom
Forecast Load
Real Time (AGC)
Actual Load
Balancing Interval (5 minutes – 1 hour)
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Generation Dispatch For Thermal Generation Only
Thermal Generation Only
Oper
able
th
erm
al ra
nge
PMin Thermal
Gen
Avai
labl
e Ra
nge
Unav
aila
ble
Rang
e
M W
0
Footroom
Headroom
Required headroom & footroom fit within operating range of generation fleet
Generation Dispatch on a Spring Day
Load
Balancing Interval (5 minutes – 1 hour)
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Load
Generation Dispatch with Must-Take Solar – Infeasible Under Higher Penetration
Must -Take Solar Thermal Generation
Only Op
erab
le th
erm
al
rang
e
PMin Thermal
Gen
Avai
labl
e Ra
nge
Unav
aila
ble
Rang
e
MW
0
Footroom
Headroom
Required headroom & footroom fit within operating range of
generation fleet
Solar
Thermal Gen
PMin Load
Solar increases balancing needs
Footroom
Headroom
Ope
rabl
e th
erm
al ra
nge
Infeasible: Minimum thermal dispatch (PMin) above footroom --
no feasible range available
Balancing Interval (5 minutes – 1 hour)
Balancing Interval (5 minutes – 1 hour)
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Generation Dispatch with Curtailable Solar — Feasible but Higher Curtailment
Must -Take Solar
Solar
Thermal Gen
PMin Load
Ope
rabl
e th
erm
al ra
nge
Infeasible: Minimum thermal dispatch (PMin) above footroom --
no feasible range available
Balancing Interval (5 minutes – 1 hour)
Footroom
Headroom
MW
0 Generation Dispatch
on a Spring Day
Curtailable Solar Feasible:
Solar is curtailed until thermal dispatch is within
operable range
Thermal Gen
PMin
Solar Curtailed Solar
Ope
rabl
e th
erm
al ra
nge
Footroom
Headroom
MW
0
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Generation Dispatch with Downward Dispatch Solar – Increases Value
Generation Dispatch on a Spring Day
Downward Dispatch Solar
Increased Value: Curtailment reduced because solar contributes to footroom
Thermal Gen
PMin Oper
able
th
erm
al
rang
e
Solar
Sola
r op
erab
le
rang
e + Sola
r op
erab
le
rang
e Curtailed
Solar
Solar
Thermal Gen
PMin
Load
Footroom
Headroom
Balancing Interval (5 minutes – 1 hour)
MW
0
Footroom
Headroom
Curtailable Solar
Feasible: Solar is curtailed until thermal
dispatch is within operable range
Thermal Gen
PMin
Load
Oper
able
th
erm
al ra
nge
Solar
Curtailed Solar
MW
0
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Generation Dispatch with Fully Flexible Solar – Optimizes Value
Generation Dispatch on a Spring Day
Downward Dispatch Solar
Increased Value: Curtailment reduced
because solar contributes to footroom
Thermal Gen
PMin Oper
able
th
erm
al
rang
e
Solar
Sola
r op
erab
le
rang
e + Sola
r op
erab
le
rang
e
Curtailed Solar
Solar
Thermal Gen
PMin
Load
Footroom
Headroom
Balancing Interval (5 minutes – 1 hour)
MW
0 Curtailed Solar
+
Balancing Interval (5 minutes – 1 hour)
Sola
r op
erab
le
rang
e
Solar
Thermal Gen
PMin
Load
Footroom
Headroom
Fully Flexible Solar
Optimal Value: Solar contributes to both
footroom & headroom Headroom from Curtailed Solar
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Source: E3,TECO, First Solar Report “Dispatchable Solar: The Key to Unlocking the Clean Energy Grid of the Future”, under review. Dispatchable or Grid Flexible Solar: operating solar plants at an optimal point which may be lower than available resource and providing regulation reserves. Non-dispatacbable solar refers to where solar plant is
only used to avoid oversupply and not provide any reserves.
Comparison of Dispatch Profiles Over The Year (Animated)
Non-Dispatchable Solar Fully Flexible Solar
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Flexible Solar Reduces Curtailment
0%
5%
10%
15%
20%
25%
30%
35%
0% 5% 10% 15% 20% 25% 30%
Sola
r Cur
tailm
ent
(% o
f Pro
duct
ion
Pote
ntia
l)
Annual Solar Penetration Potential (%)
Must-Take
Downward Dispatch
Fully Flexible
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-25%
-20%
-15%
-10%
-5%
0%
0% 5% 10% 15% 20% 25% 30%
Annu
al P
rodu
ctio
n Co
st R
educ
tion
(%)
Annual Solar Penetration Potential (%)
Flexible Solar Reduces Production Costs
Downward Dispatch
Assumes Solar $0 Variable Cost
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PV can start up in seconds (when solar resource is
available)
< 1 sec 20 min 1-4 hrs 1-2 days
PV
CT
ST
CC PV follows AGC (4-sec) signal
with high accuracy
PV CT ST CC
Regu
latio
n Er
ror
Flexibility = Key Resource Attribute of the Future Grid
Utility-scale PV is more flexible and responsive than today’s fossil fleet:
PV can operate flexibly from 0 to available power (Pavail)
PV
CT ST CC
Pmin Pmin Pmin
Pavail
Combustion Turbine
ST
CC
CT
Combined Cycle
Steam Turbine
Solar Provides Firm Capacity
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Solar + Storage Provide Clean Dispatchable Generation
Intermittency
Grid Reliability & Stability
Dispatchable Generation Flexible
Generation
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Can Solar Provide Firm Capacity Required by Utility?
24
Solar and Storage Provide Firm Capacity
Hour of the Day1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
JanuaryFebruary
MarchAprilMayJuneJuly
AugustSeptember
OctoberNovemberDecember
25% NoStorage
Summer Evening Peak Period
Hour of the Day1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
JanuaryFebruary
MarchAprilMayJuneJuly
AugustSeptember
OctoberNovemberDecember
48% 1 hr Storage
Summer Evening Peak Period
Hour of the Day1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
JanuaryFebruary
MarchAprilMayJuneJuly
AugustSeptember
OctoberNovemberDecember
72% 2 hr Storage
Summer Evening Peak Period
Hour of the Day1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
JanuaryFebruary
MarchAprilMayJuneJuly
AugustSeptember
OctoberNovemberDecember
98% 4 hr Storage
Summer Evening Peak Period
+
Game Changer: Clean Energy Plant More Cost-effective Than Conventional Generation
25
Storage Enhances Grid Capability of PV Plant Power Regulation Ramp Control
dP dt
Voltage Support
P
Q
Grid Capabilities Enhanced with Storage
• AGC • Up-Regulation • Down-Regulation • Frequency
Regulation
Flexibility Capacity Firming Energy Shifting
+
Grid Reliability Services Base Capability
Summary
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• Utility-scale PV Plants provides Essential Reliability Services & Grid Flexibility
• Combined with Storage, Solar provides Clean & Competitive Firm Capacity
• Utility-scale PV Solar contributes to Grid Stability & Reliability
Solar Power Provides Energy, Flexibility and Capacity