Wind and Solar Integration in
Colorado: Challenges and
Solutions
Colorado Rural Energy Agency
Energy Innovations Summit
Energy Storage for Intermittent Resources: Is the “Silver
Bullet” on the Horizon?
Keith Parks, Senior Analyst
October 14, 2011
Agenda
 Colorado Wind & Solar Energy Today
 Renewable Energy Integration Challenges
 Solar
 Wind
 Is Storage the Solution?
 Natural Gas Price
 Carbon Policy
 Integration Costs
Colorado Wind and Solar Today
Wind = 1735MW
NSP-MN – 1591MW
1159 turbines
Solar = 131MW*
PSCo – 1735MW
Xcel Energy – 4062MW
8652 installations
*includes 27.4MW Utility Scale Solar PV
at two installations
2x30MW utility scale solar facilities to be
operational by end of 2011
Additional 400MW of wind energy
installed by end of 2012
SPS – 736MW
Solar Energy Integration
SunE Alamosa – Single Axis Tracking (7.1AC)
technology on the system and
will be for the near-term
 PV is dramatically affected by
cloud cover – variability can
occur in seconds.
July 1, 2011
 PV is the dominant solar
axis installations match poorly
with system peak needs
August 4, 2011
 Peak production from fixed-
Wind Energy Integration
PSCo Wind Output (MWh)
Week 1
1200
 Wind variability is
over a longer time
frame – tens of
minutes to hours.
capacity value
over summer
peak periods
400
0
24
48
72
96
120
144
168
0
24
48
72
96
120
144
168
0
24
48
72
96
120
144
168
0
24
48
72
96
120
144
168
Week 2
1200
1000
800
600
400
200
0
1400
1200
Week 3
 Wind has a low
600
0
1000
800
600
400
200
0
1200
Week 4
at all times of the
day – not just at
night.
800
200
FEBRUARY 2011
 Production peaks
1000
1000
800
600
400
200
0
-200
Wind Energy Integration
PSCO Wind as a Percentage of Obligation Load (Jan 2009 thru Oct 2011)
60%
55.6%
50%
45.4%
40%
38.5%
35.4%
30%
20%
10%
Hourly
Monthly
Annual
9/1/2011
10/1/2011
8/1/2011
7/1/2011
6/1/2011
5/1/2011
4/1/2011
3/1/2011
2/1/2011
1/1/2011
12/1/2010
11/1/2010
9/1/2010
10/1/2010
8/1/2010
7/1/2010
6/1/2010
5/1/2010
4/1/2010
3/1/2010
2/1/2010
1/1/2010
12/1/2009
11/1/2009
9/1/2009
10/1/2009
8/1/2009
7/1/2009
6/1/2009
5/1/2009
4/1/2009
3/1/2009
2/1/2009
0%
1/1/2009
In real-time, more
wind means fewer
dispatchable
resources are on-line
to manage the
variability. Additionally,
wind competes with
traditional baseload
facilities for system
bandwidth. Occasional
wind energy
curtailment is required
to maintain system
reliability.
Is Storage the Solution?
Charging Fuel (% of Time) vs. CO2 Cost
System with Coal Base Load
100%
90%
80%
Coal
70%
60%
50%
40%
Gas
30%
20%
10%
Wind
0%
$0
$20
$40
$60
CO2 Cost ($/Ton)
$80
$100
Increasing Natural Gas Price
Relative Value of Storage
PSCo System (Coal Baseload)
High Value
Low Value
Increasing CO2 Price
Wind Integration Costs: Uncertainty and Variability
 Energy Storage Reduces Wind
Integration Cost for Storage Sensitivities
Integration Costs
$6.00
 Upgrade Cabin Creek
$5.00
 Increase upper pond
 Increase turnaround
efficiency
 Additional Storage Resource
 2nd Cabin Creek
$4.00
$/MWh
 Higher nameplate capacity
$3.00
$2.00
$1.00
$0.00
Base
Case
Upgrade
New
Cabin
Storage
Creek Resource
2GW
Base
Case
Upgrade
New
Cabin
Storage
Creek Resource
3GW
Public Service Company of Colorado 2 GW and 3 GW Wind Integration Cost Study.
August 19, 2011. Pg 24.
Conclusion
 Currently, PSCo system uses Cabin Creek and gas
storage as buffers
 System doesn’t have sufficient wind curtailment
exposure that can be cured by energy storage in the
near-term
 Storage capital costs above arbitrage value
 BUT…as more renewable energy is integrated into the
system, energy storage provides more value. We will
continue to evaluate role and economics of storage.
Near-Term Mitigation Strategy




Lower the Floor
Lower plant minimum capacity
Decommit - Reevaluate “must run” status
Decommission baseload (CACJA)
Upgrade Existing Storage Facilities (ie Cabin Creek)
Increase upper pond capacity
Move black start capability to diesel generators
Enable Wind to Participate in System Balancing
Implement set point control at wind plants (“optimal” curtailment)
Better forecasts = Better planning
Long-Term Solutions…
Add New Storage Facilities
Dispatchable Loads
A Big Picture View of Wind
Curtailment
System Perspective (2013)
7000
6000
Load
5000
MW
4000
3000
2000
1000
Hrs
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
0
System Perspective (2013)
7000
Load
6000
Net Load
5000
MW
4000
Wind
3000
2000
1000
Hrs
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
0
System Perspective (2013)
7000
Load
6000
Net Load
5000
MW
4000
N a t ur a l Ga s
3000
2000
D i spa t c ha bl e C oa l
1000
S y st e m M i ni m um =Must Take Cont ract s + Coal Minimum Capacit y + Must -Run Gas Minimum Capacit y - Pumping Capacit y
Ge ne r a t i on
Hrs
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
0
System Perspective (2013)
7000
Load
6000
Net Load
5000
4000
MW
Gas
N a t ur a l Ga s
Coal
3000
Wind
2000
D i spa t c ha bl e C oa l
1000
S y st e m M i ni m um =Must Take Cont ract s + Coal Minimum Capacit y + Must -Run Gas Minimum Capacit y - Pumping Capacit y
Ge ne r a t i on
Hrs
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
0
Visualization of How Off-Peak
Load Helps Mitigate Wind
Curtailment
System Bottoming Effects (No Storage)
System with Coal Baseload
Wind
(MW)
Load
Net Load (minus wind)
Gas
Dispatchable Coal
System Minimum
6:00
0:00
18:00
12:00
6:00
0:00
18:00
12:00
6:00
0:00
Curtailed
Wind
System Bottoming Effects (With Storage)
System with Coal Baseload
Wind
(MW)
Load
Net Load (minus wind)
Off Peak Charging
Increases Load...
Gas
Dispatchable Coal
System Minimum
6:00
0:00
18:00
12:00
6:00
0:00
18:00
12:00
6:00
0:00
And Reduces
Curtailed Wind
Xcel Energy Wind and Solar
Future
Xcel Energy Wind Farms Today
Xcel Energy manages
output from 4.1GW
(2972 turbines) of wind
energy across the
three operating
companies (NSP-MN,
PSCo, SPS) and
seven states (CO, TX,
NM, WY, MN, SD, ND)
NSP-MN – 1591MW
PSCo – 1735MW
Xcel Energy – 4062MW
SPS – 736MW
Forecast by end of 2011 Q3
Xcel Energy Wind Generation Growth
Installed Wind Capacity (MW)
 Xcel Energy has been the
nation’s largest wind power
provider for seven consecutive
years.*
6000
5000 MW
5000
4062 MW
4000
 Current resource plans have
5GW installed by 2015.
 PSCo will be at nearly 2GW by
3432 MW
3000
2000
the end of 2012.
1000
0
2010
*American Wind Energy Association (AWEA); US Wind Industry
Annual Market Report 2010
2011
2015
Colorado Solar Generation Growth
Distributed Solar PV Capacity
 HB10-1001 creates minimum
retail distributed generation*
requirement
350
300
 Requirement is largely met
Forecasted Minimum
Requirement
200
150
100
50
2020
2015
2011
2010
0
2009
(HB10-1342) allows for
community solar facilities
(<2MW) to qualify as well.
Historic Capacity
2008
 Solar Gardens legislation
250
MW
through Solar Rewards
program (current 99.4MW)
*Retail Distributed Generation - Must be renewable energy (wind, solar, bilmass,
hydroelectric) installed on the distribution system. There are further requirments
regarding the how much can be residential vs commercial/industrial, amount
installed by year, etc
Why Forecasting?
Obligations and Resources Today
Net Load – Load less variable output generation.
5000
MW

4500
4000
3500
Peakers
3000
Renewables
2500
Mid-Merit
2000
1500
Baseload
1000
500
0
1
25
49
PSCo - April 26, 2010 to May 2, 2010
73
97
121
145
Traditional Utility
Paradigm
Loads and Resources Today
Loads and Resources are forecast every working day for operational
planning purposes. This is called day-ahead commitment.
5000
MW

Loads
4500
4000
3500
3000
2500
2000
1500
Wind
1000
500
0
1
25
49
PSCo - April 26, 2010 to May 2, 2010
73
97
121
145
Actual – Thick Line; Forecast – Thin Line
Forecasts of loads,
variable energy
generation, and unit
availability are inputs
to the operational
planning process.
Typically 18 to 42
hours ahead, but as
much as five days.
Loads and Resources Today
Uncertainty is driven by the wind portfolio.

MW
1000
800
Mean Absolute Error
600
400
Load Error
Load = 86MW
Wind Error
200
Net Load Error
0
1
25
49
73
-200
-400
-600
PSCo - April 26, 2010 to May 2, 2010
97
121
145
Wind = 245MW
Net Load = 240MW
Renewable Energy Integration
Solutions
Loads and Resources – A New Paradigm
RE Forecasts are nice but don’t affect operations
RE is must-take
Fossil-based facilities operate to a define duty
New facilities chosen for least-cost energy
Storage facilities dispatched to peak shave
Peakers
Renewables
RE Forecasts drive operational decisions
RE is dispatchable
Fossil-based facilities are modified for flexible duty
New facilities chosen for least-cost energy w/ flexible
optionality
Storage facilities dispatched for RE/load shifting
Variable
Mid-Merit
Baseload
Balance Portfolio
Traditional Utility Paradigm (w/ some RE)
High Penetration Portfolio