Wellhead Electric Company, Inc.
Escondido Energy Center
The Benefits of MeeFog Technology
- Several MW additional output
- Improved heat rate
- Lower emissions, resulting in less load on the turbine combustor and SCR
Additional quick-start power was needed for peaking and to smooth out the fluctuations of renewable energy sources.
By lowering inlet temperatures by up to 30 °F, a MeeFog system provided several extra MW of peaking power, while improving the heat rate and lowering emissions.
The Physical Site
In 2009, Wellhead Electric Company acquired the existing, but idle, 35 MW Escondido Energy Center from MMC Energy, Inc., with plans to upgrade it to 45MW. The plant is located in an industrial park within the city limits. Summer afternoon temperatures frequently run in the 90s and often in the 100s, sapping output when most needed to power air conditioners.
California has a 33% renewables portfolio requirement, but also has some of the most stringent emissions requirements. San Diego Gas and Electric (SDG&E) serves more than 3 million customers in San Diego and southern Orange County. In 2011, SDG&E signed contracts for 450 MW of local quick-start generation to provide peaking and to backstop the renewable sources.
“SDG&E continues to sign contracts for as much renewable power as we can get to meet the state’s 33-percent mandate, but we also need resources that can be brought online quickly to provide power when other sources, such as wind or solar plants, are not available,” said James P. Avery, SDG&E’s senior vice president of power supply in announcing the contracts. “The output from most kinds of renewable generation fluctuates throughout the day, posing a challenge for our system operators who must balance supply and demand every few seconds to maintain reliability in the region.”
Wellhead’s Escondido Energy Center was part of that announcement. Following approvals by local and state regulators, Wellhead began rebuilding the site in 2013. While much of the equipment remained in place, the existing GT was replaced by an LM6000 and the stack height was raised another ten feet.
To provide the maximum peaking output and energy efficiency, while minimizing emissions, Wellhead decided to use inlet fogging on the new LM6000PC. Wellhead already was using Meefog systems at several of its other peaker plants and went with the same for the Escondido Energy Center.
“We felt inlet fogging was a cost-effective means of power enhancement,” says Tom Tinucci , Wellhead’s Director of Engineering, who works out of the company’s main office in Sacramento.
To keep the turbine operating efficiently even during record-setting heat waves, the Meefog system was designed with enough capacity to drop the inlet temperature all the way down to 75°F when the ambient temperature reached 105 °F. The fogging system includes 448 fogging nozzles divided into seven stages, each providing 4.25 °F of cooling. The fogging system has a built-in local weather station and programmable logic controller. Depending on the ambient temperature and humidity, the system will activate the number of stages needed to lower the inlet temperature to the desired set point.
Tinucci says that they use the Meefog system for most dispatches, though it is used less frequently during the winter months when daily temperatures average from the low-40s to the upper 60s. When in use Wellhead does recover several MW of lost output.
“We also get a consistently better heat rate,” says Tinucci. “The Meefog system also results in lower emissions, resulting in less load on the turbine combustor (water injection) and SCR.”