The Sierra Club on April 21 filed an appeal with the U.S. EPA’s Environmental Appeals Board to challenge an air permit issued by the Maricopa County Air Quality Department for the Ocotillo natural gas-fired power plant proposed by Arizona Public Service (APS).
APS is a utility subsidiary of Pinnacle West Capital Corp. (NYSE:PNW).
Environmental groups have pushed back repeatedly against the proposal to build a new natural gas “peaker” plant, arguing that it would increase greenhouse gas emissions and exacerbate air quality in an area that already violates standards for soot and ozone.
The permit would allow Ocotillo, a 500-MW simple-cycle plant, to emit greenhouse gases at a rate that is higher than what is allowed for a new coal plant, the club claimed. According to a recent EPA rule, newly constructed coal plants must meet a greenhouse gas emission rate of 1,400 lb CO2/MWh (pounds of carbon dioxide per megawatt-hour). In contrast, the proposed Ocotillo plant would be allowed to emit greenhouse gases at a rate of 1,460 lb CO2/MWh, the club said.
The high greenhouse gas emissions rate is a result of APS’s desire to run the facility at some points at low and inefficient loads. APS asserts that such operation is necessary to balance variable supply from renewable energy sources. The Sierra Club appeal claims that APS failed to consider a cleaner and even more responsive alternative, which is energy storage batteries.
“Utilities and regulators are out of step with changing energy markets and emerging technologies,” said Travis Ritchie, Staff Attorney with the Sierra Club’s Environmental Law Program. “In order to serve their ratepayers best, APS should look into all proven and affordable technologies for managing variability in renewable energy production. Instead they have stuck like glue to their plan to build an outdated, inefficient natural gas plant that fails to comply with Clean Air Act requirements. Integrating energy storage with conventional generation is part of the picture of any modern grid – it’s time for regulators to start factoring in this established approach when determining whether proposed natural gas plants meet regulatory standards for emissions.”
The Maricopa County Air Quality Department issued the Prevention of Significant Deterioration air permit on March 22. The Sierra Club’s April 21 appeal requires a response by May 12. APS is prohibited from starting construction during the appeal process.
The appeal noted that the Ocotillo plant currently consists of two 110-MW steam generators and two 55-MW gas turbines for a total output of 330 MW. In April 2014, APS filed an application with the county requesting a revision to its Title V permit to install five new 100-MW natural gas simple-cycle turbines, model LMS 100, to replace the two existing 110-MW steam generators.