the role of energy storage as a renewable integration solution under a 50% rps joint california...
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The Role of Energy Storage as a Renewable Integration Solution under a 50% RPS
Joint California Energy Commission and California Public Utilities Commission Long-Term Procurement Plan Workshop on Bulk Energy Storage
November 20, 2015Sacramento, California
Arne Olson, Partner
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Storage is understood to be a key renewable integration solution
It is widely assumed that dedicated grid storage will be needed at high levels of wind and solar penetration
Studies to date have included storage as a renewable integration solution but have not provided clarity on when storage is needed, or what type
• E3’s Investigating a Higher RPS study estimated benefits from 5,000 MW of energy storage as a solution case
• E3’s Western Interconnection Flexibility Assessment tested benefits of 6,000 MW of energy storage as a solution case
• CEERT’s Low Carbon Grid study assumed 7,400 MW of grid storage in all cases
• CAISO investigating 500 MW of storage in 2014 LTPP case
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Overgeneration is the main challenge at 50% RPS
Studies show that the potential for over-generation becomes significant at higher renewable penetrations
Renewable energy production is concentrated during relatively few hours of the year
California will need to find ways to use, export or store surplus renewable energy
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Value of integration solutions is driven by the cost of overbuilding renewables
Renewable curtailment requires “overbuild” of renewable resources to replace curtailed energy
• Increases the cost of RPS compliance
Integration solutions reduce curtailment and overbuild costs
Optimal level of integration solutions minimizes balances the overbuild costs with solution costs
Least cost portfolio of solutions and
renewable overbuild
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E3’s Investigating a Higher RPS: storage provides value but is higher-cost than other solutions
Low-cost pumped hydro reduces average retail rate by 0.6¢/kWh under Large Solar case
• Assumes no other solutions are implemented!
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CAISO-CEC Integration Solutions Study
Study purpose: explore renewable integration solutions
• Previous studies have identified the need for solutions to integration challenges at 50% RPS
• E3’s Higher RPS study evaluated several individual solutions
• CEERT Low Carbon Grid study assumed all solutions in place
This study seeks to identify how much of which solutions are needed, and when
• Evaluate solutions needed for different combinations of renewable portfolio and operating regimes
Renewable Integration Solutions (RESOLVE) Model adds storage or other solutions if cost-effective
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Bulk storage provides two types of renewable integration services
Long duration services: storing energy during one period and providing it back to the grid during another
• Value from energy arbitrage and hourly ramps
• Particularly valuable when charging can occur during overgeneration conditions
Short duration services: providing ancillary services for meeting grid needs within the operating hour (Regulation, Load Following, Spin, Non-Spin)
• Particularly valuable during overgeneration conditions
Both services can be provided by multiple types of storage
• Li-ion batteries, flow batteries, pumped hydro
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Long-duration services
Storage charges during daylight hours and generates at night to displace fossil generation and meet evening ramps
Example April day
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Short duration services
Storage provides within-hour reserves, reducing the need for thermal generation to run
• This provides highest value during overgeneration hours by reducing renewable curtailment
Renewables
Scheduled Curtailment
Load following reserve requirements
Gross Load
Net Load
Using storage for Load Following reserves reduces the need for thermal generation
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Storage costs are a big driver of results
Technology Round-Trip EfficiencyLi Battery 85%
Flow Battery 70%
Pumped Hydro 75%
RESOLVE builds energy storage if it reduces the cost of RPS compliance• Independently solves for optimal
discharge capacity (MW) and energy storage (MWh)
Battery costs for bulk grid needs are not well understood today and are more uncertain in the future
More storage added under aggressive cost reductions
• Storage costs are traded off against overbuild cost
“Mid” storage costs assumptions($/kW-yr)
6-hr Li-ion battery
6-hr flow battery
12-hrpumped storage
2-hr flow battery
2-hr Li-ion battery
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Observations from preliminary RESOLVE runs
Significant quantities of storage resources are added under high-solar cases without other solutions
Implementation of other solutions can delay and reduce the need for energy storage
Some storage is needed for long duration services above 55% RPS in nearly all cases
Quantity, type and duration of storage depends on the relative costs
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“Pocket Guide” to Integration Solutions
Integration solution Findings
Regional coordination More efficient dispatch and reduced curtailment
Time of use rates Shifts energy consumption toward daylight hours
Subhourly renewable dispatch
Allows system to operate with fewer thermal resources during overgeneration events
Renewable portfolio diversity
Avoids curtailment by spreading renewable production over more hours of the year
Flexible loads Advanced DR
Shifts energy consumption toward hours with overgeneration, but cost and potential are unknown
Additional storage Reduces curtailment but requires significant investment
Gas retrofits Makes existing resources more flexible at a low cost
New flexible gas resources Provides limited dispatch flexibility at a high cost
Energy efficiency Provides significant cost and GHG savings but may not reduce curtailment
Conventional demand response
Provides cost savings but does not significantly reduce curtailment
Low cost solutions with
potentially large benefits
Costs and benefits should be evaluated on specific project
or program basis
Valuable, though not as
much for integration
Solutions with the highest
identified renewable integration
value
Net benefits even w/o renewables
Thank You!Energy and Environmental Economics, Inc. (E3)
101 Montgomery Street, Suite 1600
San Francisco, CA 94104
Tel 415-391-5100
www.ethree.com
Arne Olson, Partner ([email protected])