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• Weakness of previous study: assumed no capacity on existing transmission system; upgrades essentially all single or double circuit 500kV lines “trunklines”
• Updates:– ISO high-level assessment of capacity from various CREZs 1.)
over existing system; 2.) over relatively minor new upgrades
– Additional lines on case-by-case basis: 500kV for large and out-of-state zones, smaller lines for smaller zones close to loads. Cost = function of length and capacity
– Incorporation of RETI work has been difficult – many CREZs tied to single line segments; many line segments tied to single CREZs; but additional detail would help in cost and timing review
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Transmission sizing and cost
• See:– California ISO assessment of capacity over existing system and
minor upgrades
– Zaininger Engineering assessment of capacity over RETI lines
• Each zone and transmission bundle/increment is assigned to a transmission schedule→ no generation in that bundle is available before transmission
• Non-CREZ, distributed resources, and resources accessing existing capacity not reliant on transmission→ available per contract or generic generation schedule
• Each scenario is assigned an “online date” according to the availability of the last generation resource chosen for that scenario
• No “bottlenecks” considered now; what assumptions are appropriate?
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Timeline Tool – Features to Come
• Aggregated portfolios for alternative cases presented with summary timelines and yearly generation charts
• Timelines for individual projects available for review
• Project development phases are broken out
Example Only
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Timeline Tool – Features to come (cont’d)
• Yearly generation charts can be broken out by viability class – high, medium, and low viability
• To provide direct input into 2010 LTPP, statewide portfolios will need to be “allocated” each IOU.
• Proposed approach:– Remove any POU resources from each portfolio;– Allocate public ED database projects to the IOUs with which
those projects have signed contracts (PUBLIC);– Allocate confidential ED database projects to the IOUs with
which those projects are negotiating contracts (CONF.);– Allocate generic projects to load on a pro-rata basis for each
resource type in each zone (PUBLIC);– Aggregate each IOU’s contracted, short-listed and generic
project allocations to generate IOU-specific RPS portfolios (PUBLIC, provided the aggregation sufficiently masks the confidential data).
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Integration assessment
• California ISO developing model that estimates integration needs and costs associated with 33% Reference Case from 2009 Implementation Analysis
• PG%E has developed Renewable Integration Model (RIM) tool – not as analytically comprehensive, but simpler and spreadsheet-based.
• Tools may be introduced into LTPP proceeding later this year. Possible next steps:– Parties vet methodologies and results– Models are re-run to estimate integration needs of final RPS
scenarios adopted in Scoping Memo– Results inform Commission consideration of the amount and
types of resources to authorize in 2010 LTPP
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Capacity Credit for Solar Resources
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Overview
PG&E and CAISO integration studies are considering capital costs of resources needed for intermittent renewable resource integration in addition to variable costs of increased operating reserves
Capital costs driven by assumptions about how much capacity would already have been online during the planning year
Online capacity is a function of Planning Reserve Margin
For intermittent renewables, Net Qualifying Capacity (NQC) is used to estimate contribution toward meeting peak demand
Issue: Capacity credit of intermittent renewables, particularly solar, depends on how much is online
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California Peak Load Hours
In California, peak loads occur during summer days when there are high air conditioning loads
Solar has been considered to have a high capacity credit because maximum output occurs during the hot day-time hours when load is highest The figure above shows the CAISO
load profile on June 20, 2008 which includes the annual system peak hour, 3-4 PM
0
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Hour Ending (HE)
Load
(M
W)
CAISO Load June 20, 2008
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Peak Load Day (June 20, 2008) with High Solar Penetration
“Must Run Gen” is an approximation of nuclear, coal, and minimum hydro
Solar resources are simulated fixed-tilt utility-scale PV and solar through with no storage at high penetration for June 20, 2008
High penetration of solar generation moves the “net peak” load hour, when load must be met from dispatchable generation, into the nighttime
0
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PV
Must Run GenLoad
Net Load
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CSP
Must Run GenLoad
Net Load
Load
(M
W)
Load
(M
W)
HEHE
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Top 500 Net Load Hours under high PV Penetration Levels
0
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4,000
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31,000
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0 100 200 300 400 500
Night Hours
Top 500 Net Load Hours with 0 MW PV
Top 500 Net Load Hours with 2,000 MW PV
Top 500 Net Load Hours with 4,000 MW PV
Top 500 Net Load Hours with 6,000 MW PV
Average PV Output Top 100 Hours with 6,000 MW PV
Average PV Output Top 100 Hours with 4,000 MW PV
Average PV Output Top 100 Hours with 2,000 MW PV
Average PV Output Top 100 Hours with 0 MW PV
Net
Loa
d (M
W)
Ranked Net Load Hour
Average P
V O
utput in Top 100 H
ours (MW
)
As PV penetration increases, the net load hours are re-sorted from highest to lowest and more nighttime hours are among the top 500 net load hours
E3 calculated a capacity credit for the first 1000 MW of resource equal to the average production during top 100 load hours
Added 1000 MW of resource, re-sorted hours from highest to lowest net load, and re-calculated average production during top 100 net load hours
Capacity credit declines rapidly for solar resources as more high net load hours occur at night
Marginal Capacity Credit can be negative when high renewable generation hours are displaced from the top 100 net load hours
Cap
acity
Cre
dit
Penetration (MW)
43
Capacity Credit Depends on the Resource Mix
The previous slides assumed penetration of only one technology The figures above assume a diversified portfolio with 8 MW Wind to every 3 MW PV
and 3 MW CSP Combined portfolio receives average capacity credit of 31% at 10,000 MW of
penetration, higher than any of the three individual technologies
0%
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Average Capacity Credit
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Marginal Capacity Credit
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Penetration (MW)
44
• CPUC and California ISO signed MOU on May 13, 2010 (http://www.caiso.com/2799/2799bf542ee60.pdf)– Agrees on certain elements of the ISO’s new proposed annual
Transmission Planning Process
– Commits to closer coordination between resource and transmission planning – ISO planning process considers scenarios provided by CPUC, CPUC gives substantial weight in the permitting process to projects consistent with ISO plan
• Umbrella LTPP proceeding considers EE, demand response, distributed generation, utility-scale renewables, fossil retirements, when determining overall system need– CPUC must consider these same things when assessing the need for
individual transmission projects, pursuant to statute
“The CPUC and the ISO will review the results of the California Transmission Planning Group modeling phases and evaluate their implications for the transmission needs of the CPUC's Long Term Procurement Plan renewable resource scenarios. The ISO will subsequently seek, within the time and human resource constraints of Phase 2 of the transmission planning process, to provide the CPUC and other stakeholders with a formal assessment of the transmission planning needs within the ISO balancing authority area for the Long Term Procurement Plan renewable resource scenarios.”
- May 13, 2020 MOU between California ISO and CPUC