Southern California Edison supports the California ISO’s structure for assessing renewable resource integration needs, the Edison International (NYSE:EIX) subsidiary said.
The Rosemead, Calif.-based utility on Oct. 5 registered comments on the renewable resource integration needs analysis to be conducted in the ISO’s long-term procurement plan (LTPP) proceeding.
The proceeding analyzed a series of resource planning scenarios for 2020 that varied by the amount of load, the quantity of renewable energy production, and the mix of solar and wind renewable energy production. For each scenario, the regulation, load/generation following and spin/non-spin reserves required to manage intra-hour intermittent renewable energy production were identified (“Step 1 requirements”) and then the ability of the California grid to accommodate this intra-hour variability was tested (“Step 2 analysis”).
“It is standard practice to procure additional capacity resources beyond the forecasted needs under normal conditions in order to have sufficient margin to accommodate more extreme ‘stress’ conditions such as high loads or an unexpectedly large shortfall in generation resource availability,” SoCalEd said.
The Step 2 analysis, which is based on normally expected conditions, resulted in a surplus of capacity resources that would be able to meet intra-hour renewable resource and load variability, the company noted.
“Indeed, since California IOUs are currently resourced above the desired 15-17% [planning reserve margin], there are considerable resources available to meet these Step 1 requirements,” the company said.
CAISO should further investigate to understand better how renewable resource intermittency requirements vary at different points, and to see whether there is any overlap between certain Step 1 requirements and the block hourly dispatch of energy resources in the Step 2 analysis, the company said.
Further, CAISO should address the results associated with a so-called “all gas” scenario, which stopped growth in renewable energy resource expansion at about 12% statewide, in order to have a baseline to measure the costs and greenhouse gas emissions reductions associated with the 33% renewable portfolio standard scenarios, the company said.
“In this [the all gas] scenario, there were additional integration needs despite maintaining the current portfolio of renewable resources,” SoCalEd said, adding that the reason for this was probably a sufficient amount of load growth by 2020 to erode the availability of surplus generation to meet integration needs.
However, SCE said it was unclear whether the Step 1 requirements in this scenario were consistent with what the CAISO is currently procuring for grid operations.
The company also said it doesn’t support performing planning reserve margin modeling in the LTPP. Solar energy’s contribution to meeting reliability needs should be studied separately, SCE said.
In addition, SCE said it supports CAISO’s proposal for testing a selected set of energy storage technologies to assess whether their performance characteristics differ significantly from the use of conventional fossil-fired resources in addressing renewable intermittency.