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§ A glance at EPRI GO&P§ Introduction§ Market clearing stages and implications§ Flexibility in a market environment§ Integration and participation of storage resources§ Conclusions
§ The power industry is undergoing a profound transformation:– Large penetrations of renewable energy sources (RES)– New sources interfaced through power electronics– Active demand and need for greater coordination between T&D– Integration of emerging technologies (e.g. storage, EVs, DER, etc.)– Greater interdependencies with other sectors (e.g. gas)– Electricity as energy carrier for other sectors (e.g. transport)
§ Fundamentally different power system:– Different needs, sources and modelling needs– Adapt existing market structures to accommodate
Mexico: Expectations and Potential§ Mexico has high RES potential for both, wind and solar§ How to pave the way for its optimal integration?
Sources:SOLARGIS. http://solargis.com/products/maps-and-gis-data/free/download/mexico Mexico Energy Outlook 2016, IEASolar Energy Potential in Mexico´s Northern Borders States, 2012, Wilson CenterWorld Energy Resources: Solar, 2013, WEC Marcelino Madrigal, CRE, 2018
AWS wind data based on actual 2016 meteorology–Hourly output simulated for advanced turbine: 125m hub height, 154m rotor diameter, 4 MW
Example from EPRI InFLEXion tool - Hourly Ramping by Month and Hour in the Southeast US
Large ramps in summer mornings, and winter eveningsAdding 7 GW of solar (8% energy) increases evening winter rampsAdding tracking increases ramps further
Y. V. Dvorkin, H. Pandzic, M. A. Ortega-Vazquez, and D. S. Kirschen, "A Hybrid Stochastic/Interval Approach to Transmission-Constrained Unit Commitment",IEEE Transactions on Power Systems, Vol. 30, Issue 2, pp. 621-631, Mar. 2015.
– Reserving flexible capacity for use in real time– Reduce price spikes
§ MISO Ramp Product & Look Ahead Dispatch– Capability to ramp 10-minutes ahead– Further look-ahead for ramping needs assessment
§ Xcel Energy Flex Reserve– Reserve for long-term wind ramps that are not regulation or contingency
§ ERCOT Ancillary Service Redesign– Wide scale reorganization of ancillary service products – Primary frequency response, fast frequency response, inertia service– Regulation requirements based on forecast error characteristics
Example: Utility study results (small system, 1300 MW peak)
Benefits system dependent based on quantity of variability and uncertainty, scheduling process, decisions that can be made, and existing reserve method.
Base case Static Rqmt90% conf.
By VER90% conf. EPRI 90% conf.
Operating cost, $ 531.76 M 542.22 M 541.47 M 539.29 M
Total violations (12×MWh) 2,148,894 197,027 153,653 103,333
Base case (RT Commitments)
EPRI 50%(RT Commitments)
Operating cost, $ 596.53 M 593.79 M
Total violations (12×MWh) 114,264 31,239
Utility Study found $20-$24M (3-4%) in savings using dynamic reserve method and cycling of mid-merit resources
Simultaneous Reliability Improvement and Cost Reduction
Significant Reliability Improvement at Modest Cost Increase
FERC Order 841 – Energy Storage Resources (ESR)§ ESR: “A resource capable of receiving electric energy from the grid and storing it
for later injection of electric energy back to the grid”
§ Summary:– Include participation model for ESRs in energy, A/S, and capacity markets if technically able to
do so§ Also includes ability to provide services that are not procured through organized market
(frequency response, voltage support, black start)– Eligibility of the ESR to set prices as buyer and seller when marginal– ISOs must account for technical parameters of the ESR through bidding or otherwise– ISOs must allow a minimum size requirement that is at most 100 kW– Energy stored from purchases in the wholesale market must be sold at wholesale prices
Order 841: ESR Operating CharacteristicsPhysical or Operational Characteristic Definition
State of Charge (% or MWh) State of Charge represents the amount of energy stored in proportion to the limit on the amount of energy that can be stored, typically expressed as a percentage. It represents the forecasted starting State of Charge for the market interval being offered into.
Maximum State of Charge (% or MWh) Maximum State of Charge represents a State of Charge value that should not be exceed (i.e., gone above) when a resource using the participation model for electric storage resources is receiving electric energy from the grid.
Minimum State of Charge (% or MWh) Minimum State of Charge represents a State of Charge value that should not be exceeded (i.e., gone below) when a resource using the participation model for electric storage resources is injecting electric energy to the grid.
Maximum Charge Limit (MW) Maximum Charge Limit represents the maximum MW quantity of electric energy that a resource using the participation model for electric storage resources can receive from the grid.
Maximum Discharge Limit (Pmax) (MW) Maximum Discharge Limit represents the maximum MW quantity that a resource using the participation model for electric storageresources can inject to the grid.
Minimum Charge Time (minutes/hours) Minimum Charge Time represents the shortest duration that a resource using the participation model for electric storage resources is able to be dispatched by the RTO/ISO to receive electric energy from the grid.
Maximum Charge Time (minutes/hours) Maximum Charge Time represents the maximum duration that a resource using the participation model for electric storage resourcesis able to be dispatched by the RTO/ISO to receive electric energy from the grid.
Minimum Run Time (minutes/hours) Minimum Run Time represents the minimum amount of time that a resource using the participation model for electric storage resources is able to inject electric energy to the grid (already provided by other generators).
Maximum Run Time (minutes/hours) Maximum Run Time represents the maximum amount of time that a resource using the participation model for electric storage resources is able to inject electric energy to the grid.
Minimum Discharge Limit (MinGen) (MW) The minimum MW output level that a resource using the participation model for electric storatge resources can inject onto the grid.
Minimum Charge Limit (MW) The minimum MW level that a resource using the participation model for electric storage resources can receive from the grid.
Discharge Ramp Rate (MW/min) The speed at which a resource using the participation model for electric storage resources can move from zero output to its Maximum Discharge Limit
Charge Ramp Rate (MW/min) The speed at which a resource using the participation model for electric storage resources can move from zero output to its Maximum Charge Limit.
“the following chart summarizes the physical and operational characteristics of electric storage resources for which each RTO’s/ISO’s participation model for electric storage resources must account”-FERC
Order 841: Capacity Market Eligibility§ ESR must be allowed to participate in capacity markets if able to do so§ Capacity contribution based on ratio of power to energy duration
Example: Energy Storage Capacity ValueStatus quo*: Ruling:
Power Capacity: 10 MWEnergy Storage: 40 MWhCapacity Value: 10 MW
Power Capacity: 10 MWEnergy Storage: 40 MWhCapacity Value: 10 MW
Power Capacity: 10 MWEnergy Storage: 20 MWhCapacity Value: 0 MW
Power Capacity: 10 MWEnergy Storage: 20 MWhCapacity Value: 5 MW
*In some markets
Key Question: What is the most appropriate way to measure capacity contribution from energy storage?
State of Art – ESR Participation§ PSH exists in great quantities in ISO-NE, NYISO, MISO, PJM, and CAISO and
participates in majority of ISO services:– Offer in as separate pump or gen. units that can get selected by ISO energy and ancillary
markets– PJM – Hydro optimizer, optimize mode of operation to minimize cost and leave PSH with
ending reservoir level and SoC limits§ Other limited ESR (e.g. less than a few hours of endurance) primarily participate
in ISO regulation market– Some software limitations for provision of energy and other A/S (SoC management?)– Regulation service typically most lucrative for ESR (bi-directional, mileage payment, etc.)– Typically only requires 15 minutes of sustained energy
§ CAISO Non Generator Resource - Submits offer curve from max consumption to max generation and can be selected anywhere between
Conclusions§ Variability and uncertainty have a profound effect on market outcomes§ The reserves should be estimated in a smart manner
– Assessment of the actual requirements:§ Uncertainty§ Inter-interval variability§ Intra-interval variability
§ Smart reserves can:– Reduce operating costs– Increase system reliability
§ Storage is a versatile result that can participate in energy, A/S and capacity markets– The value of storage is system dependent, regulation services are favored– Efforts to normalize the participation of across RTOs and ISOs
Where are the flexibility needs resolved?§ Ideally, there should be no deviations from day-ahead transactions§ Uncertainty and variability unavoidably materialize, and adjustments are needed
in real time§ How much are we relaying on real-time transactions?
*Capacity that must be committed by different markets in Western Interconnection
*EPRI, “Dynamic Operating Reserve and Advanced Scheduling Techniques to Support Variability and Uncertainty in Power Systems”, 3002008366, Dec. 2016.
Order 841: Price setting and Settlement§ Must pay/be paid price as a wholesale buyer and seller and set price as
wholesale buyer and seller and when available as a dispatchable resource and marginal resource– If block loaded or self-scheduled, cannot set price
§ Include make whole payments (e.g. cost recovery guarantee) when price is higher than bid price when charging or lower than offer price when discharging
§ Prices for buying and selling at nodal level, not zonal§ Transmission charges to load can be applied to ESR when charging§ Require direct metering for better accounting of wholesale
§ All ISOs – storage that participates as generator can set price§ ISO-NE – Allows PSH in pumping mode to set price as part of fast-start pricing
logic (relaxes block loading)§ PJM – PSH model separate from pricing model – cannot set price§ CAISO – Continuous ESR (NGR) can set price in either mode based on
continuous offer curve§ ISO-NE – Allows make whole payment (NCPC) for PSH when prices are above
Demand Response as Flexible Resource§ Types of Loads:
– What will be available and when?– How long will it be available for?– How is it controlled?– Will be examined in this project and quantified for case studies– Can contribute to system operators assessment of DR as a
resource for providing operational flexibility§ DR operations:
– Ramp limits– Call rate limits– Energy limits– Duration limits– Time of day/week/year availability– Efficiency of pre-loading & make up energy
System Operators will need to be able to characterize if and how DR can provide operational flexibility