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Energy Solutions
November 2010
Integrating Renewables
into the Power Grid
An Overview by
Barney Speckman
1
Overview
Why do we have to “integrate” renewablesWhat is meant by integrating renewablesHow does one think about renewable integration needsWhat are some of the challenges What are the options to meet the system’s integration
needsQ&A
2
Why do we have to integrate renewables?Before renewables, generation was added for– Low cost (coal, CCGT, hydro, geothermal)– Cost/Performance Ratio (GT, Pumped Hydro), and– Controllability and predictability was normally a given
With the most common renewables (wind and solar)– Production is variable and– Production is uncertain
For the first time, significant amounts of generation are being added that are not controllable and by their nature (variable and uncertain) they require a higher level of controllability and because of potential forecast error they require more resources be held in “reserve”
3
“Integration” can be thought of as the collection of steps or measures that are needed to operate the power system reliably with relatively large levels of renewablesA simple way to think about it is the electric power system must still– Serve customer needs and – Serve them reliably– Operate the system to meet the control requirements of the
NERC and WECC -control the power system from the seconds to hours to day time frames
– Maintain efficient “dispatch” through control and market mechanisms to result in low costs
What is meant be Integrating Renewables?
4
How does one think about integration needs
Lets look at California as an example to show the integration problem and one type of analysis to find potential solutionsCalifornia Legislature passed AB32 in 1996 and the voters supported its implementation with the defeat of Prop 23 in Nov. 2010Lets look at what it does and how one might think about what steps are needed to integrate the renewables envisioned by AB 32
5
Assembly Bill 32
AB 32 (2006) Requires California to reduce GHG emissions to 1990 levels by 2020California Air Resources Board (CARB) has been assigned task of developing a plan to implement AB 32CARB’s proposed plan includes establishing a 33% Renewable Portfolio Standard for the California electric industryCurrently a mandatory 20% RPS (by 2010) is in place for the states investor owned utilities (PG&E, SCE, SDG&E) with many Municipal Utilities voluntarily implementing RPS targets
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How the 33% RPS works
Would require 33% of the amount of energy sold to customers to be produced by eligible renewable resourcesApplies to all companies selling energy at retail in CASets 2020 as date to meet the 33% StandardEstablishes penalties for non compliance
7
How might the 33% RPS be met
No none knows for certain!!!
Many degrees of freedom in the implementation thus many uncertainties will have to be dealt withWhat technologies will utilized?Where, when and what plants will be built?How will the power be delivered to customers?What other infrastructure will be needed?How will integration needs be met?
Several studies have/are being conducted
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Possible 33% Renewable Futures Recent CPUC study used to consider several possible futures as a way to bracket the future implementation of the 33% RPSExamines cost, difficulty, GHG reductions for several mixes of technology, infrastructure requirements and integration requirementsLooks at:– 33% Reference– 27.5% Reference– High Wind– High Imports – High Distributed Generation
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Possible 33% Futures (Cont’d)
Energy and Capacity Requirements based upon CPUC Forecast compared to 2007
Renewable Portfolio Standard
Additional Energy Required
Additional Renewable
Capacity Required (Approx)
20% RPS 35 TWh 10,000 MWs
33% RPS 75 TWh 22,000 MWs
2007 Renewable Energy was 27 TWh
TWh = 1012 Watt-hours
10
Lets Look at the Technologies in California
Major contributors (potentially) to new production– Wind– Solar Thermal – Solar PV (utility and customer)– Geothermal
Lesser contributors to new production– Biomass – Biogas – Small Hydro
Large percentage of new renewables in California are in Southern part of the state
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Renewable Portfolios: Incremental (MW) and Existing Renewables (MWh) for Cases Studied - Preliminary
Biogas Biomass Geothermal Small Hydro
Solar Thermal
Solar PV Wind
20% Reference 30 324 1,052 37 107 333 5,024
33% Reference 279 429 1,497 40 6,513 3,165 8,338
Out-of-State 279 339 2,532 49 1,753 (534
Outside CA)
890 10,870(6,290
Outside CA)
High Distributed Generation
234 328 1,298 37 1,095 15,959(15,098
DG)
5,067
27.5% 30 328 1,298 40 4,868 2,864 5,977
Low Load 30 328 1,299 40 4,907 2,867 7,091
Biogas Biomass Geothermal Small Hydro
Solar Thermal
Solar PV Wind
Existing (MW- hrs)
0 6,256 13,647 687 724 0 6,229
ISO 33% RPS Study of Operational Requirements and Market ImpactsSlide 11
12
Nexant Study - Assumed Locations of Incremental Renewables in California - 33% RPS, 2020 Preliminary
Excluded areas with high population density, national parks, landmarks, sensitive areas, etc., to exclude areas not practical for renewable project development
Geothermal 135Siskiyou
Solar 2303Wind 750
San Bernardino
Solar 1250Wind 500
Riverside
Solar 750
Imperial
Wind 513
San Diego/ Imperial
Biomass 100Solar 2250Wind 2610
LA/Kern
Biomass 100Humboldt
BiomassWind
200350
Bay Area
Solar 177San Luis Obispo
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Lets Look at the Technologies in California Wind Generation
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Wind Generation Characteristics
Low cost technology on an energy basisProduction is – Variable– Uncertain– Often Remotely Located– Not highly correlated in time with system load
Capacity credit 8-30% of nameplate for long range planning purposesThus is considered a source of energy but not a significant source of capacity
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Tehachapi Wind Generation in April – 2005Variable and Uncertain
0
100
200
300
400
500
600
700
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hour
Meg
awat
ts
−Average
Each Day is a different color.
−Day 29
−Day 5−Day 26
−Day 9
CAISO Data
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Wind generation tends to be inversely correlated to daily system load
CAISO Load -- Fall 2006
20,00021,00022,00023,00024,00025,00026,00027,00028,00029,00030,00031,00032,000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hours
MW
Load
Total Wind -- Fall 2006
300325350375400425450475500525550575600
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hours
MW
Total Wind
CAISO Data
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Wind vs. Actual Load on a Typical Hot Day in 2006
CAISO Wind GenerationJuly 2006 Heat Wave
0
200
400
600
800
1,000
1,200
07/1
6/06
07/1
7/06
07/1
7/06
07/1
8/06
07/1
8/06
07/1
9/06
07/1
9/06
07/2
0/06
07/2
0/06
07/2
1/06
07/2
1/06
07/2
2/06
07/2
2/06
07/2
3/06
07/2
3/06
07/2
4/06
07/2
4/06
07/2
5/06
07/2
5/06
07/2
6/06
07/2
6/06
MW
Wind Generation Wind Generation at Peak
Total Wind Generation Installed Capacity = 2,648 MW
Wind Generation at Peak
CAISO Data
18
Lets Look at the Technologies in California Solar Characteristics
Higher cost on an energy basisSeveral technologies– Thermal (central tower, trough, Sterling, etc)– Thermal with storage or supplemental gas firing– PV roof top– PV large scale (> 1MW)
Irradiation is variable but absent clouds relatively certainWith clouds, production is less certainSolar production correlates better with system loadTechnologies with larger thermal mass tend to filter out short term variability (e.g. solar thermal)Solar Capacity Credit 60% – 95% (depending upon technology) for the purpose of long range planning
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Lets Look at the Technologies in California Solar Thermal Generation
eSolar’s Modular Solar Power Plant Concept
Solar II Solar Central Receiver
Trough Design
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Lets Look at the Technologies in California Solar PV
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Solar Irradiation Examples – Sacramento Area
Spring 2009 data collected at SMUD PV siteData is collected at 1 minute intervalsSeveral days shown in first week of March and MayIndicative of Solar production, especially PV
Source: http://www.nrel.gov/midc/
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Solar Irradiation Examples – Sacramento March 7
March 7, 2009
0
100
200
300
400
500
600
700
800
900
6:30
6:48
7:06
7:24
7:42
8:00
8:18
8:36
8:54
9:12
9:30
9:48
10:06
10:24
10:42
11:00
11:18
11:36
11:54
12:12
12:30
12:48
13:06
13:24
13:42
14:00
14:18
14:36
14:54
15:12
15:30
15:48
16:06
16:24
16:42
17:00
17:18
17:36
17:54
Time
Glob
al Ho
rizon
tal [W
/m^2
]
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Solar Irradiation Examples – Sacramento March 5
March 5, 2009
0
100
200
300
400
500
600
700
800
900
1000
6:33
6:51
7:09
7:27
7:45
8:03
8:21
8:39
8:57
9:15
9:33
9:51
10:09
10:27
10:45
11:03
11:21
11:39
11:57
12:15
12:33
12:51
13:09
13:27
13:45
14:03
14:21
14:39
14:57
15:15
15:33
15:51
16:09
16:27
16:45
17:03
17:21
17:39
17:57
Time
Glob
al Ho
rizon
tal [W
/m^2
]
24
Solar Irradiation Examples – Sacramento March 2
March 2, 2009
0
100
200
300
400
500
600
700
800
900
1000
6:38
6:56
7:14
7:32
7:50
8:08
8:26
8:44
9:02
9:20
9:38
9:56
10:14
10:32
10:50
11:08
11:26
11:44
12:02
12:20
12:38
12:56
13:14
13:32
13:50
14:08
14:26
14:44
15:02
15:20
15:38
15:56
16:14
16:32
16:50
17:08
17:26
17:44
Time
Glob
al Ho
rizon
tal [W
/m^2
]
25
Solar Irradiation Examples – Sacramento May 5
May 5, 2009
0
200
400
600
800
1000
1200
1400
5:05
5:23
5:41
5:59
6:17
6:35
6:53
7:11
7:29
7:47
8:05
8:23
8:41
8:59
9:17
9:35
9:53
10:11
10:29
10:47
11:05
11:23
11:41
11:59
12:17
12:35
12:53
13:11
13:29
13:47
14:05
14:23
14:41
14:59
15:17
15:35
15:53
16:11
16:29
Time
Glob
al Ho
rizon
tal [W
/m^2
]
26
Typical Daily Wind vs. Solar Generation Pattern Shows Complimentary Nature
Wind vs SolarMay 25, 2007
-10
190
390
590
790
990
1190
1390
00:0
0
00:4
5
01:3
0
02:1
5
03:0
0
03:4
5
04:3
0
05:1
5
06:0
0
06:4
5
07:3
0
08:1
5
09:0
0
09:4
5
10:3
0
11:1
5
12:0
0
12:4
5
13:3
0
14:1
5
15:0
0
15:4
5
16:3
0
17:1
5
18:0
0
18:4
5
19:3
0
20:1
5
21:0
0
21:4
5
22:3
0
23:1
5
00:0
0
MW
Wind Solar
CAISO Data
27
System Operations – Renewable Integration
Operating the Power System Reliably Requires:Sufficient Regulation (second to second Auto Generation Control of generators or other resources) and Within-the-hour Net Load Following (ramping generators or other resources minute to minute) andInter-hour Net Load Following (ramping over hour to hour) andUnit commitment to cover the peak plus reserves andIncreased unit commitment requirements due to Variability and Uncertainty (forecast error)
All of these are a function of the mix of renewables
28
Load-Following Up requirements under alternative, Summer 33% RPS Reference Case - Preliminary
Slide 28
0
2,000
4,000
6,000
8,000
10,000
12,000
33%Ref 20%HiLD HiDG OOS AllGas 27.5%HiLD
Load‐following up vs. forecast errors
All Forecast Error Improved Forecast Error No Forecast Error
ISO 33% RPS Study of Operational Requirements and Market Impacts
29
System Operations – Renewable Integration
Over-generation potential increases with renewablesOvergen occurs when inflexible generation exceeds load plus planned exports“Energy Dump” occurs when over-gen can not be sold to willing buyers in neighboring areas2008 Nexant studies indicate– Technology dependent– With high solar penetration can occur during high load
hours
30
System Operations – Renewable Integration Overgen/Dump Energy – Nexant Results
Most likely to happen in March-May period when hydro, wind and solar production can all be high and on weekends when load is lowIn 2008 simulations, more than 90% of dump occurs in SCE territorySimulation understates dump due to simplified transmission model used in production simulation and normal hydro conditions assumedMay require changes in current and future contract structure to allow more frequent curtailment, as well as needing to reduce minimum generation levels
31
Results – Dump Energy for 50% RPS (2008 Study)
05,000
10,000
15,00020,00025,00030,000
35,00040,00045,00050,000
55,00060,000
1 3 5 7 9 11 13 15 17 19 21 23
Hour
MW
05,000
10,00015,00020,000
25,00030,00035,000
40,00045,00050,000
55,00060,000
1 3 5 7 9 11 13 15 17 19 21 23
Hour
MW
Without Storage With Storage (6 hours)
Storage Technologies reduce dump energy
Conditions on a day with solar and wind conditions both high… 50% RPS
WindSolarTraditionalLoad+ExportsLoad
32
Analysis of generation fleet flexibility in 2020 with varying levels of renewables - Preliminary
4,000
4,500
5,000
5,500
6,000
6,500
All Gas 20% 27.50% 33%
Reg. Up & Load Following Up Req. (MW ) Summer Max
33
Analysis of generation fleet flexibility in 2020 - Preliminary
40,000
42,000
44,000
46,000
48,000
50,000
52,000
54,000
56,000
58,000
All Gas 20% 27.50% 33%
Total Resources (MWs) at 17% PRM That Provide Regulation & Load Following
34
33% Implementation Challenges - Transmission
Long lead time to build transmission Uncertain which generation projects will developUncertain where transmission upgrades will be needed2009 CPUC Study shows need for up to 7 new major high voltage transmission projectsIndicative Nexant results
35
Nexant Results – (2008) Transmission Expansion Bulk Transmission Upgrades For 33% RPS – 2020
36
33% Implementation Challenges - Transmission
Potential Source of Multi-Year Delay for HV TransmissionTypical lead-time 6-11 yearsTypical process involves:– Project study and approval by CAISO (1-2 years)– CPUC approval (2-3 years)
• Can add significant delays, e.g., delay in approval of Sunrise Project• Other litigation post CPUC approval can also delay the project
– Engineering/Procurement (1-3 years)– Construction/Environmental Mitigation (2-3) years
• Delays could be based on the route and degree of environmental mitigation
37
33% Implementation Challenges - Resources
Need for resources to integrate renewables dependent upon renewable mixFor example a high wind case would require more “capacity” to meet Planning Margin than a high solar– 3000 MW needed for Wind (10,000 MW) and Solar (2,000 MW)– 300 MW needed for Wind (4000 MW) and Solar (8000 MW)– Assuming wind at 15% and solar at 60% capacity credit
Regulation and ramping needs are dependent upon renewable mix– Not well understood at this time for full mix of renewables– CAISO 33% RPS Integration studies underway to clarify
requirements
38
What are some of the options to address these challenges
Focused geographical development to streamline transmission siting to reduce the time to build transmissionImproved longer term analytical tools to help narrow the uncertainty as 2020 approaches - more probabilisticPlanning Reserve Margin (PRM) may have to be expanded to include integration requirementsPotential increased use of distributed generation to reduce the transmission delays associated with larger scale remote wind and solar
39
Resources can potentially meet the system integration needs
In addition to traditional CCGTs and GTsImproved control over new wind and solar to deal with severe ramps and over-gen eventsPotential increased role for demand side responses to address regulation and rampsPotential increased role for storage to address regulation, load following and over-gen (full range of options from PP Hydro, CAES, batteries etc.)Improved wind forecasting to reduce daily uncertainty and thus reduce regulation and load following requirementsImproved solar generation forecasting through better cloud cover forecasting to reduce daily uncertainty
40
What potentially can meet integration needs (2)
In additionSolar thermal generation with integrated storage or supplemental firing to reduce Reg and LF requirementsIncreased contribution from existing hydro and pumped storage – may result in increased maintenance and costsIncreased contribution from existing thermal generation– may require capital improvements to achieve increased level of flexibility Fast regulation from high speed batteries or inertial storage Electric Vehicle battery managementIncreased reliance on RECs for out of state renewables
41
Questions
Questions?
