Arizona Public Service defends permit for 500-MW addition at Ocotillo

Arizona Public Service (APS) told the U.S. Environmental Appeals Board that the board should deny the Sierra Club’s April 21 petition for review of the Maricopa County Air Quality Department’s (MCAQD) prevention of significant deterioration (PSD) permit authorizing APS to construct five new natural gas-fired combustion turbines at its Ocotillo Power Plant.

Said the utility’s May 12 brief: “Sierra Club seeks to force MCAQD to conduct a more detailed analysis of whether battery storage of electricity should somehow be incorporated into the proposed source in order to reduce its greenhouse gas (‘GHG’) emissions.”

The board, mindful of a tight schedule for reviewing air permit appeals like this, recently allowed the Sierra Club to file a reply to the APS brief of May 12, and also gave APS and the MCAQD until May 20 to file any further briefs, if they choose.

Said the May 12 brief of APS: “At the outset, the Petition must be denied because Sierra Club failed to meet the threshold requirement of presenting its objections to MCAQD during the Permit’s notice and comment period. Sierra Club submitted comments on an initial draft of the Permit arguing that various forms of energy storage (including battery storage) should be considered in the ‘best available control technology’ (‘BACT’) analysis for GHGs. But when MCAQD did precisely that—by developing and publishing for public comment a revised draft permit and technical support document (‘TSD’) explaining that battery storage options would redefine the source and are technically infeasible—Sierra Club failed to comment or register its objections that are now presented in this Petition. By withholding its objections for appeal, Sierra Club denied MCAQD the opportunity to address those objections in the final Permit and forfeited its right to raise those issues before the Board.

“In any event, Sierra Club’s arguments are without merit. Sierra Club claims that MCAQD committed clear error when it concluded that integrating battery storage would redefine the proposed source and does not require further examination in the GHG BACT analysis. To the contrary, MCAQD took a hard look at the proposed source’s purpose and design, and correctly determined that battery storage is a wholly different method of providing electricity than the proposed gas-fired combustion turbines and would frustrate the purpose and design of the project. The proposed turbines are designed to provide quick-ramping, reliable backup generating capacity in support of intermittent renewable energy resources by generating up to 375 MW in less than two minutes. Sierra Club’s proposed battery storage approach would eliminate that quick-ramping capability because it would force the proposed turbines to start from complete shutdown each time they are called upon—a process that takes 10 to 30 minutes—and because batteries themselves, which have limited storage capacity and depend on other generation sources to charge them, cannot fill the gap with the required magnitude or duration of generation. Further, MCAQD also found that battery storage is technically infeasible for the proposed facility.

“Likewise, Sierra Club is incorrect that MCAQD failed to respond to its comments regarding battery storage. MCAQD did address Sierra Club’s concerns at length, both by developing and publishing a revised draft permit and TSD and by directly responding to those comments upon publication of the final Permit. To the extent MCAQD’s response is not as detailed as Sierra Club would prefer, that is only because Sierra Club failed to present the issues raised in this Petition with sufficient clarity—let alone any technical detail—in its comments.”

APS is the owner and operator of the Ocotillo Power Plant, located in Tempe, Arizona. APS has been issued a permit to construct the Ocotillo Power Plant Modernization Project, in which APS plans to replace two steam electric generating units at the site with five new natural gas-fired simple-cycle combustion turbines of approximately 100 MW each.

The new turbines will serve to replace the 200 MW of peak generation that will be retired at Ocotillo with cleaner units, and to provide an additional 300 MW of peak generation to handle future growth. The project is designed to serve as a peak load facility capable of providing 25 to 500 MW capacity that will quickly respond to rapid changes in electricity demand, particularly in response to fluctuation in generation from solar energy sources.

APS is a subsidiary of Pinnacle West Capital Corp. (NYSE: PNW).

About Barry Cassell 20414 Articles
Barry Cassell is Chief Analyst for GenerationHub covering coal and emission controls issues, projects and policy. He has covered the coal and power generation industry for more than 24 years, beginning in November 2011 at GenerationHub and prior to that as editor of SNL Energy’s Coal Report. He was formerly with Coal Outlook for 15 years as the publication’s editor and contributing writer, and prior to that he was editor of Coal & Synfuels Technology and associate editor of The Energy Report. He has a bachelor’s degree from Central Michigan University.