The gas-fired Jackson power plant, which Consumers Energy plans to purchase in December 2015, is a flexible, cost-effective way for the utility to meet its near-future capacity needs – with the Thetford new-build project still an option for the long term.
David B. Kehoe, employed by Consumers Energy as Director of Staff, Energy Resources Business Services, noted in Dec. 5 rate testimony filed at the Michigan Public Service Commission that in January 2014, Consumers Energy announced plans to purchase the 540-MW DPC Juniper gas-fired plant in Jackson, Mich. The purchase of this facility is projected to occur in December 2015 and is intended to partially replace the generating capacity that will be lost when the company’s seven oldest coal-fired units retire in 2016 due to clean-air needs.
Consumers Energy will incur expenses in 2014 and 2015 for monitoring operations and preparing for the company’s projected December 2015 purchase of the Jackson plant, Kehoe noted.
Kehoe said about the prudency of this purchase decision: “The Jackson Plant is an existing facility with a proven track record of being efficient, flexible, and available when called upon to operate. Also, the purchase of the Jackson Plant will allow Consumers Energy to continue to lower emissions and capitalize on today’s lower natural gas prices while providing customers with immediate value.”
The Jackson Plant was designed to take advantage of rapid-changing load and market conditions. Unlike a traditional combined cycle plant with two large frame combustion turbines and one steam turbine, the Jackson Plant has six smaller General Electric LM6000 turbines, a GE 7EA turbine and two steam turbines. All seven turbines have their own heat recovery steam generators (HRSG) with supplemental duct firing. Steam from the HRSGs supply steam to the two steam turbines.
“The LM6000s and 7EA turbine designs are among the most common in the power industry and have a long-proven track record,” Kehoe wrote. “Also, the LM6000s have inlet cooling and water injection to raise their efficiency towards the top in their class. Finally, the Jackson Plant’s availability has routinely been above 98%.”
The smaller turbines and HRSGs allow start-up and warm-up times to be approximately half of a traditional combined cycle plant. This allows quicker response to changing load conditions along with much lower fuel consumption during start-ups. The Jackson Plant can also reach near-design output during maintenance or failure of any one of the seven combustion turbines or steam turbines.
Also, outages for the smaller combustion turbines are routinely shorter than the larger frame turbines. If necessary, the Jackson Plant has a spare LM6000 turbine on-site, which would allow the company to maintain generation efficiency if an operating turbine fails.
The six LM6000s have a much lower minimum load point than traditional (2×1) combined cycle plants – two combustion turbines and one steam turbine. Traditional 2×1 plants have a minimum load point of 50% of its rated output – so a 540 MW plant would have a minimum load point of approximately 270 MWs. In contrast, the Jackson Plant has a minimum load point of 150 MWs. Finally, the Jackson Plant can change load at rates of 30 MWs per minute compared to 10 MWs per minute for a traditional combined cycle plant(s).
In 2013 and 2014, expenses were incurred for the owners engineer, site testing and land acquisition of the deferred Thetford gas-fired power plant. In 2018, Thetford will incur expenditures for the development of a new simple cycle unit. This new unit is intended to meet the needs of the company’s projected capacity shortfall with the Midcontinent Independent System Operator.
David F. Ronk Jr., Director for Electric Transactions and Wholesale Settlements at Consumers, noted that in June 2013, the company filed for approval of a Certificate of Necessity for Thetford, a nominal 700-MW natural gas-fueled combined cycle facility. The projected capital cost of the Thetford Plant was expected to be $700m. The company later determined that the purchase of the Jackson Plant, to address capacity shortfalls in years 2016 and beyond, for $155m was reasonable and prudent and would save its customers money compared to building the Thetford Plant for $700m.
Said Ronk about the future of the Thetford project: “The Company’s forecast of its capacity requirements indicates that additional capacity will need to be added beginning in 2021. Mr. Kehoe presents testimony regarding plans to add a simple cycle combustion turbine as an initial part of the Thetford Combined Cycle Plant in that year with some work to begin in 2018.”