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Green Gridworks

Case studies on integrating renewable resources.

Fortnightly Magazine - February 2012

to interconnect new geothermal and biomass resources in the Imperial Valley followed a different development path. The Imperial Irrigation District provides electric power to the Imperial Valley and parts of Riverside and San Diego counties, and it operates its own balancing area independent of CAISO. An Imperial Valley study group was formed as an outgrowth of CPUC Decision No. 0406010 to address transmission plans for geothermal and solar renewable resources in that region. The group’s 2005 report analyzed several transmission alternatives to export about 2,200 MW of renewable energy from the Imperial Irrigation District’s territory; the total potential for renewable energy was estimated to be even larger. According to a 2009 report by a statewide collaborative group, the Renewable Energy Transmission Initiative, the Imperial North A CREZ was found to have the best environmental ranking— e.g., the lowest score—and one of the best economic rankings (see Figure 7) . The potential renewable generation is much greater than the Imperial Irrigation District’s native load of about 1,000 MW—less than 2 percent of California’s statewide load—and is almost an order of magnitude greater than the amount the Imperial Irrigation District would need to meet its own 33 percent RPS target. Therefore, development of these resources would be primarily for the benefit of the other California balancing authority areas and would require associated transmission upgrades to export the added renewable energy from the Imperial Irrigation District.

Because of its small size, Imperial Irrigation District faced a significant risk that the transmission costs for 2,200 MW of exports might become stranded if renewable development was delayed or abandoned. However, the development of a statewide transmission plan under the auspices of the California Transmission Planning Group appears to have improved the likelihood that Imperial Irrigation District will be able to build transmission for export in the next few years. The group was formed in early 2009 as a result of discussions facilitated by FERC to address California‘s transmission needs in a coordinated manner that would include all California balancing authorities. It provides a forum for conducting joint transmission planning studies consistent with FERC Order 890 principles and for coordinating transmission planning among its members. In February 2011, the California Transmission Planning Group issued its first statewide plan that evaluated numerous potential transmission projects against four scenarios of potential renewable development and recommended selected projects.

According to the California Transmission Planning Group report, the Imperial Irrigation District wheels approximately 580 MW of geothermal energy from the Imperial Valley into the CAISO balancing authority. With new planned upgrades, Imperial Irrigation District exports could increase to almost 1,800 MW by 2014. The Imperial Irrigation District recently completed an open season for long-term wheeling contracts on Path 42, the interface between Imperial Irrigation District and Southern California Edison. More than 1,550 MW of capacity was requested, and generators will pay for all transmission studies and system upgrades on the Imperial Irrigation District portion of Path 42. The generators will be reimbursed for necessary system upgrades through transmission credits equal to the amount that they contributed to the upgrades.

Integrated Planning