This report outlines Southern California Edison’s (SCE’s) framework and stochastic method for the analysis it performed for the renewable integration track (Track 2) of the California Public Utilities Commission’s (“Commission’s) 2012 Long-Term Procurement Proceeding (LTPP).
On September 16, 2013, before testimony was submitted, the Commission cancelled Track 2 of the proceeding and deferred the Track 2 issues to the 2014 LTPP. In the meantime, to continue the dialogue on the important Track 2 issue of what additional procurement, if any, is needed to meet need associated with integration of increasing amounts of intermittent renewable generation resources that the SCE is making its work public. SCE’s work was enhanced by input it received at two CPUC sponsored workshops2 to vet SCE’s analysis and methods with the parties to the LTPP, as well as through direct communications with several parties.
The investor owned utilities (IOUs) are on target to provide 33% of their energy from renewable energy sources by 2020, a large portion of which is expected to come from solar photovoltaic and wind energy. In the past, when the primary source of generation was conventional, the primary variability in planning the power system was the amount of load on the system at any particular time. Unlike conventional resources, however, these renewable sources of energy are inherently intermittent and uncertain.
Conventional generation is more predictable and controllable than solar and wind generation and can be dispatched to meet load variations in a relatively predictable way. The variable characteristics of some renewable generation present challenges in planning new systems.
To analyze the impact of additional intermittent resources on the system, SCE created a daily net load by subtracting wind and solar generation from load on an hourly basis. This net illuminates the amount of load that must be satisfied by other types of generation. Because there is a daily pattern associated with intermittent resources, they have the potential to place new stresses on California’s dispatchable generation, such as a steeper ramp in a shorter timeframe during the evening hours.
In this example, dispatchable resources could be required to increase production drastically in the evening hours, causing concern that the current dispatchable generation fleet may not be able to meet load demand. In addition to the issue illustrated above, the minute-by-minute variability of intermittent generation adds to the natural variability of load. As a result, potential swings in 5-minute net load may be too drastic for the existing generation fleet to meet. In both cases, the high penetration of intermittent generation places new pressures on California’s dispatchable generation. These new pressures and the uncertain ability to meet future load demand with the new portfolio mix motivated SCE to conduct the renewable integration analysis presented in this report.
The question that SCE addresses in its analysis is “What additional resources and characteristic types are needed to satisfy system reliability standards in the face of increasing amounts of intermittent renewable generation?” SCE chose reliability
2011 Historical vs. the 2020 Environmental Case assumptions from the 2010 LTPP standards as the metric for the analysis because they represent an acceptable economic tradeoff between construction of new generation and possible system outages. The specific reliability standards that SCE used in its study are discussed later in this paper.
Every two years, the CPUC holds a Long-Term Procurement Plan proceeding to review and adopt the IOUs’ ten-year procurement plans. The LTPP proceeding evaluates the utilities’ need for new fossil-fired resources and establishes rules for rate recovery of procurement transactions.” (http://www.cpuc.ca.gov/PUC/energy/Procurement/LTPP/ ) Two workshops were held by the California Public Utilities Commission, during which SCE presented its methodology and results outlined in this paper. Workshop details can be found at:
Filed Under: News, Policy