California ISO integration of renewable resources report (Draft)

This report details transmission and operating issues and recommendations for integrating renewable resources on the CAISO Control Grid. The CAISO discusses the gross variations in electric production from wind energy due to the intermittent nature of the resource. During periods of highest demand, the winds drop off.

Chapter 1: Background (Excerpt)

The purpose of this Draft CAISO Integration of Renewable Resources Report (Report) is to ensure the successful integration of wind generation and other renewable resources with the planning, and operation of the power grid. The required Renewables Workgroup combines the talents and resources within Planning and Infrastructure Development (P&ID), Grid Operations, Market Operations, Information Technology and External Affairs and further representatives from General Electric, Battle Labs – Pacific Northwest Division and AWS Truewind. It also involves coordination and collaboration with IOU’s, wind generator owner/operators, Scheduling Coordinators, the CEC, industry experts and adjacent control area operators.

The scope of this Report is a detailed focus on Transmission Planning and Operating Issues and secondarily, a focus on Market Issues and Use of Storage Technology. Our goal was to identify any voltage control problems, transient stability issues and transmission loading issues. The primary driver behind this Report is to ensure that any transmission control devices (SVC’s, reactors, capacitors, etc.) needed by 2010 are ordered as soon as possible.

Chapter 10 of this Report addresses conclusions and implementation tasks going forward. These tasks will focus on the remaining Operational Issues and Market Issues. This includes the need for better Day-Ahead forecasting and use of this information for Day-Ahead Unit Commitment decisions. It also covers technical and market issues on the import of renewables.

1.1. Wind Generation Fundamentals
To address wind generation and integration issues, it is useful to have a common understanding of some fundamental facts:

1.1.1. Wind generation is an energy resource and not a peaking capacity resource.

Because wind is an intermittent resource, it can not be counted upon in California to meet the peak loads on the hottest days of the year. Criticism that wind generation taken alone in California cannot be counted upon to help the CAISO meet the summer peak load is true. The wind typically does not blow on the hottest days of the year so the wind generation production is usually less than 10% of its nameplate capacity at the time of the summer peak load. Wind generation’s role is to displace fossil fuel generation resources, to help the state meet greenhouse gas initiatives and carbon reductions, and to reduce the exposure to volatile natural gas prices. Utilities purchase the power output from wind generators to meet their RPS requirements, and to back down the power required from the more expensive gas fired power plants.

1.1.2. Wind Generation, solar generation and system load are all quite variable.

The variability of any one of these items may be offset by the other or they can be additive and increase the total variability on the system. To accommodate this increase in variability, we need increase flexibility from other resources such as hydro generation, dispatchable pump loads, energy storage systems, and fast ramping and fast starting fossil fuel generation resources. The portfolio of future California resources must reflect this need for very flexible generation resources to assist with the integration of large amounts of intermittent resources. This required increased flexibility will be one of the cost drivers for integration for renewables.

1.1.3. The size of the control area matters

The larger the control area, the more diversified the resource areas, and the larger the benefits of aggregation. Production from geographically dispersed resources typically have much different meteorological conditions so they do not all move up and down together. The larger the amount of aggregation, the greater the reduction in variability and the easier it is to forecast the total renewables energy production.

1.1.4. The cost and complexity of wind integration starts low

The variability of wind generation energy production from a small number of units is usually much less than the variability of system load changes. The system operator is accustomed to dealing with daily load forecast errors, changes in hourly load forecasts, and the unpredictability of loads. As the amount of wind generation in an area increases, it will reach a point where its variability is greater than the variability of load. As wind generation further increases, the amount of variability will increase non-linearly. RPS goals to move from 20% to 33% energy from renewables could potentially more than double the integration problems and costs.

1.1.5. Forecasting of wind generation energy production, both Day-Ahead and Hour-Ahead is an essential integration strategy

Wind generation energy production is not typically scheduled in the Day-Ahead market. The forecast for wind generation energy production is a very important component in deciding what other generation should be scheduled for the next day. If 3,000 MW of wind is forecasted for the next day, it is inefficient and costly to start up fossil fuel generation that will not be needed. The CEC IAP study and other wind integration studies have pointed out the critical importance of Day-Ahead wind generation forecasts. The Day-Ahead forecast does not have to be 100% accurate to achieve substantial benefits.

1.2. Other Key Factors
1.2.1. Large ramps will be an issue

There will be periods where wind energy product rapidly declines while simultaneously the load is rapidly increasing. Energy ramps as high as 3,000 MW per hour or larger may occur between 0700 and 1000 hours. Fast ramping generation, such as hydro units, will be essential for the CAISO to keep up with the fast energy changes. There will be other periods, particularly in the winter months, where large pacific storms will impact the wind parks and their energy production will rapidly ramp up to full output. The solution is going to be the development of new ramp forecasting tools to help the grid operators.

1.2.2. Planning and managing transmission for renewable is a key strategy

Renewable resources can be built much faster than the required transmission upgrades can be designed, approved and built. New transmission and transmission upgrades are essential to link these locational constrained renewable facilities to the backbone power grid. New strategies are needed to manage the congestion on the transmission network to facilitate the maximum delivery of renewable energy to customer loads.

1.2.3. Coordination with neighboring control areas will be a key to success

For California to meet the 20% RPS goal, the CAISO will have to import some of the renewable energy from adjacent control areas. New rules and procedures will be needed to lower the barriers for import and export of intermittent resources between control areas. Coordinated transmission plans as well as coordinated energy scheduling and operating practices will be a key to success.

1.3. Renewables Portfolio Standard Goals
1.3.1. Twenty Percent (20%) Additional Renewable Resources - 2007 to 2013

Energy from renewable resources is expected to increase by 130% in the next five years. This large increase is driven by the State’s Policy on Renewables Portfolio Standard, which requires the IOU’s to serve 20% of their customers load from renewable resources by the year 2010. The CEC’s forecast of the renewable mix by 2010 is shown in Figure 1 below:

The CAISO interconnection queue for renewable resources through the year 2013 contains 14,116 MW of wind generation and 11,264 MW of solar generation. It is not anticipated that all the generation in the interconnection queue will be built by 2013 so our studies and the CEC studies have scaled back the amount of new renewables generation to the numbers shown in the table above. The transmission and operating plans and recommendations contained in this report are based on the scaled back amount of renewables that’s forecasted to be installed by 2010.

1.3.2. Thirty-Three Percent (33%) Additional Renewable Resources – 2020

The CEC IAP study for 2020 used 12,700 MW of wind and 6,000 MW of solar generation which is consistent with the numbers in the table above from their August 15, 2006 IAP workshop. The 33% RPS goal requires dramatic increase in solar generation as well as wind generation. Many of the most productive wind generation sites will be developed by 2020 or earlier so solar generation will have to play an increasing role to achieve the 33% RPS goal. The capacity value of the renewable resources typically is 20% to 37% of the name plate rating of the facility. The capacity value8 of 30% means that for every 100 MW of installed nameplate capacity, the facility is only capable of delivering 30% to the total energy potential of the resource on an annual basis. The exceptions are biomass and geothermal resources which have capacity values of 89% and 90% respectively. Therefore, to increase the amount of energy from renewable resources from 20% to 33% requires approximately a doubling of the installed capacity of the renewable resources.

Note: This CAISO report on the integration of renewables covers only the 20% RPS requirement and does not include an analysis of the 33% goal. We will address our approach on the 33% target in Chapter 10 after we have a clearer idea on the integration of 20%.

Caiso Integrationof Renewables

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SEP 1 2007
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