TODAY’S STUDY: HOW WYOMING AND CALIFORNIA WINDS FIT TOGETHER
Wind Diversity Enhancement of Wyoming/California Wind Energy Projects: Phase
July 2015 (University of Wyoming)
On January 25, 2013, the Wyoming Infrastructure Authority (WIA) released the University of Wyoming’s “Wind Diversity Enhancement of Wyoming/California Wind Energy Projects.” The 2013 Study was based on one (1) year of modeled.
This study, also commissioned by the WIA, addresses the impact of diversifying the mix of renewable energy assets used in California’s electrical system. The study was carried out using 10-minute wind data from meteorological towers in Wyoming combined with actual 10-minute average wind and solar electrical production data from California to perform this assessment. The results of this report confirmed the findings of the earlier report, but goes on to provide an objective means of evaluating different combinations of renewable assets. Concrete examples of the benefits of diversity are then provided. The highlights of the results are the following.
• Due to the geographical difference in renewable energy resource availability, high Wyoming wind energy production often occurs during periods when California renewable energy production is low. Results using field data from Wyoming and production data from California support the results of an earlier report that only used modeled data (Wind Diversity Enhancement of Wyoming/California Wind Energy Projects). Correlation, the parameter used to quantify diversity, was found to behave in the same way as the modeled data suggested. In addition, seasonal and diurnal characteristics of wind in Wyoming and that in California were shown to be complementary as diversity would suggest.
• A group of Renewable Energy Quality Metrics (REQMs) is developed and applied to several different renewable energy scenarios. The metrics provide an objective means for characterizing the behavior of different combinations of renewable energy assets when added to existing assets so that the resulting resource mixes can be compared. The analysis can be applied to small scale (e.g. utility), regional scale (e.g. system operators), and national scale (e.g. western interconnect) perspectives.
• When applied to California’s electrical system, these metrics indicate that, relative to the existing renewable energy sources in California, adding Wyoming generated electricity to California’s existing renewable assets increases the performance metrics in all categories. Adding high capacity factor Wyoming wind results in better metrics then adding more California renewables.
o One of these metrics (the relative variability) indicates the amount of variation in the power availability from a group of renewables, so lower numbers are better. As evident in the bar graph, this study shows that the relative variability worsens (it increases) when additional California renewables (CA + CA 33%) are added to the existing California renewables (CA Exist), and improves (it drops) when Wyoming wind is added (CA + WY 33%).
o These Renewable Energy Quality Metrics (REQMs) provide an additional tool that can be used by decision makers (utilities, system operators, and policy makers) to help in choosing which renewables to add to their systems by providing an objective means of comparing different options.
o A companion white paper on these quality metrics authored by James Detmers will be released shortly highlighting the application of these metrics for real electrical systems.
• Example benefits of diversifying renewable energy assets are provided in terms of quantities important to electricity generation, storage, and distribution, as well as in terms of environmental impacts. Combining diverse renewable assets can produce the following results.
o A decrease in water use as well a reduction of greenhouse gas emissions are observed. Comparing the addition of 6000 MW of California renewables to 6000 MW split between California renewables and Wyoming wind yielded water savings in the billion gallon range and CO2 reductions in the millions of tons.
o A cost savings resulting from reduced backup generation is observed. For a 6000 MW addition, a combined Wyoming/California solutions yielded saving of 100s of millions in dollars annually when compared to an all California solution.
o A reduction in flexible capacity ramping requirements that cause large price increases.
o A reduction in the amount of storage needed to support renewables at a given level is indicated. When comparing a Wyoming/California mix of renewable energy added to the existing California renewables, a simplified analysis suggested a significant reduction in the amount of storage per GW-hr of energy generated necessary to meet a given demand without additional stand-by support from non-renewable generation sources.
Note that some of these benefits listed above are a mix of increased capacity factors as well as geographical diversity as the two effects are often hard to separate. However, these impacts are important to consider as California continues to build out its renewable portfolio. In particular, the results of the storage analysis suggest that geographical diversification can help reduce the amount of storage needed to support variable resources.
This study clearly demonstrates the benefits of diversity, and it is hoped that it spurs additional work by others including utilities and system operators to further analyze and quantify these benefits for specific cases. With the recent push to increase California’s renewable energy portfolio from 33% to 50%, considering new renewable resources that provide geographical diversity, and, as has been shown here, Wyoming’s high capacity factor wind in particular, would be in California’s best interest. With additional coal-fired plants shutting down over the next several years and additional closures of power plants due to the phase-out of once-through cooling, the opportunities for renewable energy to expand its footprint will be available.
The results of this study were initially presented at the Wyoming Infrastructure Authority’s Spring Energy Conference on June 11-12, 2015 at the Little America Resort in Cheyenne, WY. The Conference Agenda is posted on the WIA’s website.1
Complementary to the analysis performed herein is a companion work being performed by Mr. James Detmers, former COO, CAISO. Mr. Detmers’ work “New Metrics for Acquiring Renewable Energy.” A paper on this work is being released at the same time as this report, and preliminary results were presented at the WIA’s 2015 Spring Energy Conference.