Flexible Solar Power: Unlocking Solar’s Full Potential · Generation Dispatch on a Spring Day . Downward Dispatch Solar . Increased Value: Curtailment reduced because solar contributes

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

http://www.caiso.com/Documents/TestsShowRenewablePlantsCanBalanceLow-CarbonGrid.pdf

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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

http://www.caiso.com/Documents/TestsShowRenewablePlantsCanBalanceLow-CarbonGrid.pdfSource




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

https://www.ethree.com/wp-content/uploads/2018/10/Investigating-the-Economic-Value-of-Flexible-Solar-Power-Plant-Operation.pdf



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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


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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



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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


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


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


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


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


MW

0 Curtailed Solar

+


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)


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

(%)


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

23

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


AugustSeptember


48% 1 hr Storage


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


AugustSeptember


72% 2 hr Storage


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


AugustSeptember


98% 4 hr Storage


+

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