California Independent System Operator Renewable Integration Study David Hawkins September 2007 Achieving California’s 20% Renewable Portfolio Standard
Over Generation Conditions Typical conditions that lead to over generation • Light load conditions - loads Imbalance between Generation and Load around 22,000 MW or less, • All the nuclear plants on-line and at maximum production, • Hydro generation at high production levels due to rapid snow melt in the mountains, • Long start thermal units on line and operating at their Pmin levels because they are required for future operating hours, • Other generation in a “Must Take” In Area Generation + Imports ≠ Load + Exports status or required for local reliability reasons, and • Wind generation at high production levels. 2
Minimum Generation Levels during light load conditions Generation/Load Production Level If wind generation exceeds Spring 2006 2,912 MW, then there is no room (MW) for the excess generation Nuclear 4,528 Minimum thermal generation could be 2,000 to 3,000 MW. Minimum “Must Take” such 2.400 as QFs Need for lower P min values and Minimum Geysers 650 more units that have fast start Accurate forecasting of day- Minimum Thermal 1,000 ahead wind generation Minimum Hydro 3,700 production will be essential to minimize over-generation Minimum Interchange 2,880 schedules Total Generation plus 15,158 Key Issue is what gets cut? Interchange Spill some wind ? Minimum Load 18,070 Spill some water? Difference 2,912 Spill some of both? 3
Over Generation typically drives real-time prices negative ACE versus Wind Gen - April 2006 1200 900 Wind Gen 600 Over Generation MWs 300 ACE 0 0:00 0:39 1:18 1:58 2:37 3:17 3:56 4:35 5:15 5:54 6:34 7:13 7:52 8:32 9:11 9:51 10:30 11:09 11:49 12:28 13:08 13:47 14:26 15:06 15:45 16:25 17:04 17:43 18:23 19:02 19:42 20:21 21:00 21:40 22:19 22:59 23:38 -300 April 15, 2006 - Real-Time Prices 100 80 60 40 Dollars 20 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 -20 SP15 NP15 -40 Hour Ending 4
Conclusions & Recommendations about Over Generation Over generation occurs with the existing amount of wind generation but it is relatively rare occurrence. The lack of good Day Ahead wind generation forecast contributes to the problem. The addition of large amounts of wind generation facilities will exacerbate the problem. MRTU Integrated Forward Market should help to mitigate the problem Generation schedules match the load forecast. Accurate Day Ahead wind generation forecasts will be a key component for the Day Ahead RUC process. Wind generation operators should be prepared to curtail some wind generation production to mitigate serious over generation conditions in the future. The amount of renewable energy lost will be small. The CAISO must work with the wind generator operators to ensure procedures, protocols, and communication facilities are in place so dispatch commands can be communicated to the plant operators. Additional storage capability on the system would help to mitigate both over generation and large ramp conditions. 5
Comparison of CEC IAP study and ISO Renewables Integration Report Issue CEC IAP Report CAISO Report Report covers both 20% RPS Yes report covers the No the CAISO report focuses target and 33% target transmission and only on the requirements renewable resources to meet the 20% RPS required to meet the 2010 target. The 2020 33% 20% RPS target and the RPS requirements will be 2020 33% RPS target. done as a future project. Report covers all types of The IAP report does a The CAISO report covers the renewable resources. forecast of the amount of amount of energy being all types of renewables delivered from the various that could potentially types of renewable developed in the State resources but then and then concentrates on concentrates on the the issues with transmission plan for the intermittent resources planned build out of wind such as wind and solar. generation in Tehachapi and the operations issues associated with intermittent resources. 6
Comparison of CEC IAP study and ISO Renewables Integration Report Issue CEC IAP Report CAISO Report The project conducted power Transmission Study The project built on the IAP flow and production cost modeling work and simulations to establish a engaged GE to do joint 2006 baseline, and to detailed studies of the develop renewable resource Tehachapi Transmission portfolios and infrastructure Plan. The CAISO and for 2010 and 2020. GE team did detailed Load flows were prepared using PowerWorld software. Load Flow, Transient Production costs were Stability and Post modeled using General Transient analysis of the Electric’s Multi-Area planned build out of wind Production Simulation (GE- and solar generation in MAPS™) modeling software the Tehachapi area for to evaluate grid operation with increasing levels of the 20% RPS target wind and solar generation in scenario. The the generation mix. 7
Comparison of CEC IAP study and ISO Renewables Integration Report Issue CEC IAP Report CAISO Report Transmission Conclusions Significant transmission A detailed study of the 20% RPS target by 2010 investments are necessary approved $1.8 billion to meet the 2010 and 2020 Tehachapi transmission RPS targets. For the 2010 plan meets all planning Tehachapi case, 74 new standards for voltage or upgraded transmission control, line loading, and line segments are needed dynamic system at a first order estimated response. The results are cost of $1.2 billion plus dependent on the type of $161 million for wind generation installed transformer upgrades and in Tehachapi so all future unknown costs for land turbine installations must use and right-of-way costs be type 3 or Type 4 units which have power factor controls and meet WECC LVRT standard. 8
Comparison of CEC IAP study and ISO Renewables Integration Report Issue CEC IAP Report CAISO Report Transmission Conclusions The 2020 case would require The first step in developing a 33% RPS target by 2020 128 new or upgraded transmission plan for 33% transmission line segments, renewable resources is to with just over half (66) needed determine where the to serve increasing load resources will be located and requirements. For just the what type of resources will be 500kV and 230kV additions, a built. The CAISO currently first order estimated cost has 20,000 MW of solar and would be $5.7 billion. In 20,000 MW of wind addition, 40 new or improved generation facilities in our transformers would be interconnection queue. needed at an estimated cost CAISO will work with the of $655 million (excluding developers, utilities and state detailed land use and right-of- agencies to determine the way costs). most likely renewable locations that will be developed and then develop a transmission plan that connects these resources to the load centers in the State. 9
Comparison of CEC IAP study and ISO Renewables Integration Report Issue CEC IAP Report CAISO Report A combination of in-state generating Minimum load The CAISO report agrees with the IAP resources and power exchange report and recommendations. The operation and agreements or capability should be report does a more in-depth analysis potential over pursued to allow operation to a of potential over generation problems generation minimum net load of between 18,000 during light load conditions with conditions to 20,000 MW. maximum hydro generation that Pursuing generating resources with occurs during spring runoff. The greater minimum turndown and conclusions are similar to the IAP diurnal start/stop capabilities, report in that we will need More fast start fossil fueled units that ensuring greater participation by loads, and optimizing use of pumped can be shut down during periods of storage hydro will also aid with maximum wind generation production, More hours of 3 pump operation at integrating variable renewable energy generation. Helms Pump Storage Plant, and the • In-state generating resources should need to evaluate new storage also be targeted for providing technologies Potential need to implement pro-rata scheduling flexibility hourly. • Maintaining or improving hydro cuts in wind generation production to flexibility and accessing generating mitigate serious over generation resources with faster start and stop problems for a limited number of capabilities will aid with hourly hours per year. scheduling flexibility. 10
Comparison of CEC IAP study and ISO Renewables Integration Report Issue CEC IAP Report CAISO Report Regulation and The IAP report concludes that The CAISO study developed a Load Following there will be an increase of 10 new method and model for MW/minute of load following and calculating the amount of 70 MW/minute of down load- regulation and load following following during light load periods. that will be required. The The increase in regulation is average amount of regulation relatively modest at 20 MW increase is approximately 100 MW annually. There is a major seasonality factor for calculating the amount of regulation required. Regulation up may increase by 250 MW for some hours and regulation down may increase by 500 MW for some hours. Ramp Rates The IAP report included a finding The CAISO study found similar that ramp rates will increase to as ramp rates as the IAP study. high as 12,000 MW over a three hour period during the morning load pick up. 11
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