California Utility Turns To Dresser-Rand For Peak Summer Power Needs

California Utility Turns To Dresser-Rand For Peak Summer Power Needs

Well before California’s energy crisis became critical, the Modesto Irrigation District (MID) public utility recognized the need to increase base load generating capacity, and to quickly boost output to meet sudden summer peak demands.

The utility turned to Dresser-Rand for a steam turbine that could ramp up from 13 to a 37 MW power within 15 to 20 minutes. The 37 MW steam turbine, in combination with a single General Electric LM6000 Sprint combustion turbine generator, will give the Modesto Irrigation District an additional 80 MW of power during peak periods.

"We needed flexibility," said Greg Salyer, generation manager for the Modesto Irrigation District. "We needed a sliding pressure steam turbine that could ramp up or down at any given time of the day." The plant will tie in with the district’s Woodland Generation Facility.

"It will be a very fuel efficient plant that offers a lot of flexibility," Salyer predicted.

The new generating plant, scheduled to go on-line next spring, is a combined cycle plant. "It includes a heat recovery steam generator to produce high pressure and low pressure steam for the turbine generator," said Fred Bender, Dresser-Rand’s project development manager in Laguna Hills, California.

"The impulse steam turbine utilizes a Lufkin gear that reduces from 4,500 rpm to 1,800 rpm," Bender said. Exhaust is 1.5 inches HgA (mercury absolute). The generator is a 4-pole, 1800 rpm machine provided by GE Canada.

"The boiler operates under a wide pressure range," he explained. "Steam conditions range from 468 psig at 737 degrees F, to 1,264 psig at 950 F." It produces the maximum amount of power on sliding pressure operation as the temperature and pressure go up to maximum design. "It’s a nice fit for us, a lot of flexibility in the controls."

The Dresser-Rand steam turbine is manufactured in Wellsville, New York. The turbine being produced for the MID Woodland Generation Facility will become the largest steam turbine to be combined with a single LM6000 combustion turbine. It is scheduled for initial startup in February 2003.

The package suits MID’s needs perfectly. The utility has a maximum summer peak load of approximately 600 MW. Only approximately 220 MW is generated internally while 80 MW is from externally owned generation. The remaining 300 MW of power is purchased through contracts or on the open market. MID also supplies irrigation water to agriculture in Stanislaus County, about 90 miles east of the San Francisco Bay area. The electric utility is a ratepayer cooperative whose board of directors is selected by public election.