Gas-fired options offered for Cayuga coal plant in New York

New York State Electric & Gas (NYSEG) on May 17 filed with the New York State Public Service Commission its Cayuga Repowering Analysis in response to the commission’s Jan. 18 order to look at options for this coal-fired facility.

The report’s recommendations are necessarily preliminary given the unverified nature of the information underlying the four repowering options proposed by Cayuga Operating Co. LLC, which operates the plant, said NYSEG, which controls the transmission over which the power from that plant flows. The report’s analysis and recommendations are also necessarily based on assumptions about uncertain future variables including the price of natural gas, the number of hours that the repowered generators would be called upon to run, the forward looking price of electricity and capacity, construction and permitting uncertainties, financing risk and other variables, NYSEG cautioned.

Also, NYSEG pointed out that its analysis is based only on data provided by Cayuga Operating, and that some of that data tends to be “optimistic” in favor of Cayuga Operating’s proposal.

The report recommends that the company’s transmission reinforcement alternative be adopted as the best available option. Moreover, given the uncertainty inherent in a generation option, ther also recommends that transmission planning be continued for risk mitigation until such time as any repowered generation is actually brought on line.

As the entity responsible for local reliability, NYSEG said it conducted an analysis of the proposed mothballing of Cayuga and identified adverse reliability impacts that could occur if the mothballing were to take place. NYSEG also identified transmission system reinforcements as a mitigation measure that would remedy those reliability impacts but estimated that all of the reinforcements would not likely be completed until 2017. Since the system reinforcements necessary to mitigate the reliability impacts would not be in service until after the proposed mothball date, NYSEG determined that Cayuga would need to remain capable of operating and available for commitment in order to maintain system reliability on an interim basis, with a deal covering that having an initial term out of Jan. 15, 2014.

On Feb. 19, NYSEG transmitted to Cayuga a solicitation for the repowering of tCayuga. The repowered facility was required to consist of at least two units of at least 150 MW each and be capable of producing at least 300 MW for a minimum of 600 hours per year, with the facility capable of operating for a period of 15 years.

Cayuga then presented four separate repowering options. Each of the options requires the permitting, siting and construction of a new natural gas pipeline to the Cayuga facility.

  • Option 1 – would repower the two existing coal-fired boilers with natural gas while continuing to utilize the balance of the existing plant facilities to generate electricity. This option involves the least amount of new construction, so it could be done quicker. The maximum output of Option 1 is 300 MW. The existing Cayuga facility entered commercial operation in the 1950s and exists today as two units with a total site output of 300 MW (net). Coal is the original and base fuel of the existing facility.
  • Option 2 – would repower Cayuga with simple-cycle combustion turbine generators firing only natural gas. Option 2 proposes three new General Electric LMS100 simple-cycle combustion turbines with a maximum combined output of 294 MW. The objective of Option 2 is to continue a reliable supply of approximately 300 MW of electricity to the grid and the proposed simple-cycle gas turbines offer a potential solution for this need. The identified GE LMS100 units offer effîcient, low emissions service for cyclic operating needs.
  • Option 3 – is to repower the Cayuga Unit 2 with a combined-cycle combustion turbine generator, a heat recovery steam generator (HRSG) and a condensing-cycle steam turbine generator. The objective of Option 3, like each of the preceding options, is to supply a nominal 300 MW to the grid on a high-reliability basis. This option also includes a fuel switch to natural gas on the existing Cayuga Unit 1. Option 3 will continue to utilize the Unit 2 steam turbine and once through cooling from the existing infrastructure. The General Electric PG7241FA would produce about 169 MW. Therefore, the nominal output of this configuration, prior to any supplemental duct fìring, would be 234 MW. Supplemental duct firing could boost the station output by a minimum of 25 MW to as much as 40 MW for a total output of between 259 MW to 274 MW.
  • Option 4 – proposes two new combined-cycle combustion turbine generator trains with a maximum output of 326 MW. The equipment that best matches an independent, two power train configuration sporting two combustion turbines, two HRSGs and two steam turbines for reliability, are Alstom 11N2 units, the report said. Two separate power trains, i.e., 1 x 1 CC x 2 trains, would provide maximum redundancy and reliability. Two trains of 1 x 1 CC separate plants are similar to the existing coal-fired configuration. It provides the most flexibility and reliability but at an added cost. The maximum combined output is 326 MW.

In general, Option 1 and Option 2 as well as Unit 1 for Option 3 are designed to meet the reliability need, but due to the inefficiency of the designs, are not projected to run much based on New York ISO economics, NYSEG pointed out. Cayuga Option 4 and Unit 2 for Option 3, utilize the most efficient technology available and would likely run a significant portion of the time. Their operation could result in a short-term reduction in market prices. Alternatively, absent repowering, the mothballing of the existing coal-fired facility would likely lead to the development of a new, potentially more efficient (due to economies of scale) natural gas-fired generator with an in-service date similar to the proposed in-service date for the repowering, NYSEG pointed out.

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.