PG&E mounts tidal power project
Pacific Gas and Electric Co. (PG&E), the city and county of San Francisco, and Golden Gate Energy Co. have agreed to undertake a comprehensive study of harnessing San Francisco Bay tides to generate power.
Specifically, PG&E is committing up to $1.5 million to fund research by "third-party experts." San Francisco is putting up as much as $346,000 for "feasibility studies and stakeholder outreach." Golden Gate Energy, a Florida company that holds a Federal Energy Regulatory Commission license to bring tidal turbines to the bay, says it will cooperate with the project.
In addition to being renewable and emissions-free, tidal power is reliable and predictable because tides rise and fall with the phases of the moon. PG&E says that siting tidal turbines (Figure 1) would not raise issues of land-use and visual impacts—as do other forms of renewable energy, including wind and solar. A 2006 EPRI study identified San Francisco Bay as one of the world's most promising sites for tidal power technology.
1. Spin cycle. An artist's conception shows one possible way to capture the dependable power of tides in the Golden Gate area. Courtesy: PG&E
"Exploring the potential for harnessing the tide in the Golden Gate to deliver new supplies of clean power to our customers is one of the most exciting renewable energy possibilities being explored anywhere in the world today," said outgoing PG&E CEO Tom King. San Francisco Mayor Gavin Newsome said, "We all agree that it is imperative that we develop new alternative energy sources like tidal energy."
Key drivers of the research program are California's aggressive renewable portfolio standard (RPS) program and the state government's push to reduce greenhouse gas emissions. PG&E says it is now adding more than 300 MW annually in renewable resources. This year, the San Francisco–based company has already signed contracts to buy 274 MW of wind, solar, geothermal, and other qualified renewables under the state's RPS program.
PG&E says the initial phases of the tidal current study will begin this summer and take about a year to complete. "If findings in the initial rounds of research affirm the feasibility and promise of tidal power," the utility said, "future plans could ultimately lead to the development of a full-scale commercial project."
The San Francisco utility says it is now getting some 13% of its energy from renewables that qualify under the California RPS program: solar, wind, biomass, geothermal, and small hydro. Counting large hydro and nuclear, more than half of the electricity that PG&E delivers to its customers comes from generation that emits no or little carbon dioxide. PG&E is also looking at the possibility of harvesting electric power from Pacific Ocean waves off the coasts of Mendocino and Humboldt Counties.
GE F-class turbine breaks record
General Electric Co. reports that its installed fleet of F-technology gas turbines has now accumulated more than 20 million hours of commercial operation in power plants around the world.
What's more, says GE Energy, the company is expecting to ship its 1,000th F-class machine this summer. Steve Bolze, GE Energy's power generation chief, said the F-class turbine (Figure 2) "has become an industry benchmark for efficient and reliable electricity production" over the past 20 years. A company press release adds that the machines "were the first gas turbines in their class to reach 40% turndown while maintaining single-digit NOx and CO emissions."
2. F, for first. General Electric's long-lived, high-performing Frame 7 gas turbine has repeatedly raised the bar for efficiency since its introduction in 1987. Courtesy: General Electric Co.
GE introduced F technology in 1987, just as use of natural gas to generate electricity was beginning a worldwide boom. The first unit was shipped in 1988 and entered commercial service in 1990 at Dominion Virginia Power's Chesterfield site in Virginia. In 1989, Tokyo Electric Power picked F-class turbines for a 2,800-MW expansion of its Yokohama power station.
In 1994, notes GE, a 7FA unit at Korea Electric Power Corp. became "the first gas turbine in the world to reach 55% thermal efficiency in commercial combined-cycle operation." In late 1995 and early 1996, a Frame 7FA at Sithe Energies' Independence plant in Oswego, N.Y., recorded 100% availability and reliability over 108 days of continuous operation.
Moving into the 21st century, in 2002, GE Frame 7s surpassed 5 million fired hours in worldwide service. In 2004 and 2005, China's Gas Turbine Power Plants Construction Project picked GE to supply 20 F-class machines for the first two phases of its plan to meet growing electricity demand while limiting pollution. In late 2006 and 2007, Saudi Arabia said it would buy 35 F-technology gas turbines for power projects in the oil-rich kingdom.
According to data from GE's Operational Reliability Analysis Program, the 7F is the most reliable F-class turbine and the first to achieve 99.1% reliability. According to GE, the newest member of the F family, the Frame 9FB, "has achieved combined-cycle efficiency exceeding 58%." Mated with GE's high-efficiency advanced technology (HEAT) steam turbine in a combined-cycle operation configuration, the 9FB "can produce more than 412 MW, a significant increase over the 9FA's combined-cycle output of approximately 390 MW."
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