By limiting the use of the two generating units at its coal-fired Coronado Generating Station and sharing emissions control capability between them, the Salt River Project believes it will be able to keep both units running until 2032 without installing new selective catalytic reduction, or SCR, equipment.
The metropolitan Phoenix public power utility announced its operational strategy for the plant on Jan. 6. The Salt River Project, or SRP, said it will share the SCR emissions controls it installed on unit 2 in 2014 to also handle emissions at unit 1. The SCR sharing plan will require increased seasonal curtailments of the plant's overall operation. In 2018, the plant had a capacity factor of 53.90%, according to S&P Global data, meaning it operated a little over half of all hours that year.
The SRP estimated that the work to re-engineer the SCR to accommodate both units will cost about $50 million to $60 million, considerably less than the $115 million to $120 million it would cost to equip unit 1 with its own SCR system. Most of the work needed for the re-engineering will involve installing ductwork to connect the SCR to Unit 1, SRP spokesman Scott Harelson said in an email.
Previously, the SRP faced a deadline to either install the SCR, which is used to reduce nitrogen oxide emissions, or retire unit 1 by 2025.
Coronado Generating Station
The utility said the SCR sharing arrangement will allow the SRP to close other coal units and postpone the need for an additional 380 MW of fossil generation to meet future peak load.
The SCR reconfiguration also will give impacted workers and communities more time to plan for the plant's eventual retirement, the utility said. Additionally, it additionally will provide "time for battery storage technology to further develop as SRP continues to increase its investments in renewable energy."
The SRP and other Arizona utilities have worked for years to comply with the U.S. EPA's emissions requirements, leading to extensive negotiations and legal battles. The federal agency in 2017 finally approved SRP's plan to curtail the use of Coronado unit 1 as an interim strategy to comply with its regional haze requirements.
Units 1 and 2 of the 762-MW plant near St. Johns in eastern Arizona began service in 1979 and 1980, respectively.