Opinion ID: 6498394
Heading Depth: 3
Heading Rank: 1

Heading: The plant and its operational history

Text: The Bartow plant consists of four natural-gas-fueled combustion turbines (CT) and a much larger steam turbine. Each of the four CTs compress ambient air, mix it with natural gas, and ignite the mixture to produce a hot gas. The heated air-fuel mixture expands through the CT blades, causing each CT to rotate its shaft. The spinning shaft of each CT independently drives its own generator that produces electricity. Then, hot waste gas that exhausts from each CT is used to create steam that similarly rotates the larger steam turbine, thereby powering the larger fifth electrical generator. -3- When constructing the plant, DEF purchased an “aftermarket” steam turbine that Mitsubishi had originally designed for another plant, where it was intended to run on steam created from the exhaust of three CTs with a steam supply capable of generating 420 MW, which Mitsubishi had also listed as the nameplate capacity of the steam turbine at the time of manufacture. When the plant was placed online in 2009, however, DEF operated the steam unit using steam produced from the waste heat from all four CTs, producing electricity from the attached generator well above the steam turbine’s nameplate capacity. Because the steam-powered generator produced electricity using waste heat, operating this portion of the plant in this manner would have been cost-effective. However, during a routine inspection in March 2012, DEF discovered unusual wear or damage to the steam turbine’s blades, which required DEF to replace them. The parties refer to this initial period of operation, from June 2009 to March 2012, as Period 1. Although the steam turbine was not routinely operated above 420 MW after Period 1, the replacement blades suffered similar damage and had to be replaced again in 2014, twice in 2016, and again in -4- 2017 during the forced outage at issue in this case. The parties mark the operational time between each blade replacement as a separate period: Period 2 starts in April 2012 and ends in August 2014; Period 3 starts in December 2014 and ends in April 2016; Period 4 starts in May 2016 and ends in October 2016; and, finally, Period 5 starts in December 2016 and ends in February 2017. In 2017, at the end of Period 5, DEF decided against reinstalling any of the previous blade types—as they all experienced damage—and installed a pressure plate which derated the steam unit from 420 MW to 380 MW. This caused DEF to incur the replacement power costs that it now seeks to recover. The pressure plate remained in the steam turbine until Mitsubishi installed redesigned turbine blades in December 2019. The blades installed in 2019 have apparently been performing normally, without unusual wear or damage.