Conventional Power Sources

PG&E’s 163 MW Humboldt Bay Generating Station employs technology that produces significantly fewer emissions than the older plant it replaced.

PG&E’s efforts to build a clean energy portfolio also include making long-term investments in conventional generation that, under specific state requirements, must meet a greenhouse gas emissions performance standard equivalent to an efficient, combined-cycle natural gas plant. These efforts include new, highly efficient and flexible natural gas-fueled plants owned and operated by PG&E, as well as long-term contracts with third-parties.

Past Ownership of Conventional Generation

Prior to 1999, PG&E owned more than 7,000 MW of oil- and gas-fired conventional boilers and combustion turbine generating facilities. In the late 1980s and into the 1990s, PG&E began to modify its fossil fleet in a programmatic fashion to substantially reduce NOX air emissions.

In the late 1990s, in response to California’s electric energy deregulation law, PG&E sold all but two of its fossil-fueled power plants, Hunters Point Power Plant and Humboldt Bay Power Plant. PG&E also sold its renewable geothermal facilities at The Geysers. As part of an agreement with the City of San Francisco, PG&E retained its Hunters Point Power Plant and committed to retire it when the plant was no longer needed to ensure electric reliability for customers. PG&E retired this plant in 2006.

Separately and voluntarily, PG&E targeted the second remaining PG&E-owned conventional generating facility, the Humboldt Bay Power Plant, for replacement with a new cleaner, high-performance plant at the same site. PG&E did not sell the Humboldt plant because of its obligation to decommission a retired nuclear generating unit at the site.

New Plants Owned and Operated by PG&E

More recently, PG&E has received permission from the CPUC to own and operate new, state-of-the-art natural gas-fired plants with emissions levels that are best in class.

PG&E has safely commissioned three substantial, new generating facilities since early 2009:

  • Photo of the Humboldt Bay Generating Station.

    Humboldt Bay Generating Station: This 163 MW natural gas plant is 30 percent more efficient than the older fossil-fueled plant it replaced. It employs technology that produces significantly less SO2, NOX and CO2 emissions than the previous facility.

    The plant is located in a relatively isolated section of California’s north coast region and provides a significant majority of electrical capacity to the area. The plant’s design—selected for the region because of its low emissions and flexibility—uses reciprocating engines that are air-cooled, reducing water use by eliminating the need for once-through cooling from Humboldt Bay.

  • Photo of the Colusa Generating Station.

    Colusa Generating Station: This 657 MW combined cycle natural gas plant features cleaner burning turbines that allow the plant to use less fuel and emit significantly less CO2 than older plants. “Dry cooling” technology allows the facility to use 97 percent less water than plants with conventional “once-through” water cooling systems.

    The plant has 530 MW of base capacity and approximately 127 MW of low-cost peaking power that can be used during peak energy demands or in emergency situations. In addition, the plant is designed to lower its power output when renewable resources like wind and solar become available. The plant uses a zero liquid discharge system that recycles waste water and further reduces the amount of water needed by the facility.

    Proactively Managing Our Emissions

    At the Colusa Generating Station, a team of employees created a first-of-its-kind air emissions calculator that helps to protect local air quality and ensures that PG&E maintains full compliance with regulatory requirements. The calculator helps operators at the plant to proactively manage air emissions from the high-efficiency facility. The team has made the calculator available for use at other PG&E facilities that have similar complex air-quality permits. The team earned PG&E’s 2011 Richard A. Clarke Environmental Leadership Award.

  • Photo of the Gateway Generating Station.

    Gateway Generating Station: This 580 MW combined cycle natural gas plant has 530 MW of base capacity and 50 MW of low-cost peaking capability. On average, the plant yields dramatically less NOX, SO2 and CO2 for every megawatt-hour of power produced compared to older fossil-fueled plants. Gateway also uses dry cooling technology, which allows the plant to use 97 percent less water than older plants with once-through cooling water systems.

PG&E’s Air Emissions

To comply with stringent local air quality regulations, PG&E is focused on minimizing air emissions from its conventional sources of power generation. The following figures reflect emissions from PG&E-owned generation sources.

Air Emissions1
2009 2010 2011
Total NOX Emissions (tons) 1,258 904 144
Humboldt Bay Power Plant2 1,167 819 N/A
Humboldt Bay Generating Station3 N/A 5 23
Gateway Generating Station4 92 78 73
Colusa Generating Station5 N/A 1.5 48
NOX Emissions Rates (lbs/MWh)
Humboldt Bay Power Plant 4.05 4.27 N/A
Humboldt Bay Generating Station N/A 0.08 0.10
Gateway Generating Station 0.07 0.05 0.06
Colusa Generating Station N/A 0.04 0.05
Fossil Plants 0.82 0.49 0.06
All Plants 0.09 0.06 0.008
Total SO2 Emissions (tons) 37 42 12
Humboldt Bay Power Plant 31 34 N/A
Humboldt Bay Generating Station N/A 1 2
Gateway Generating Station 6 7 6
Colusa Generating Station N/A 0.14 4
SO2 Emissions Rates (lbs/MWh)
Humboldt Bay Power Plant 0.11 0.179 N/A
Humboldt Bay Generating Station N/A 0.015 0.009
Gateway Generating Station 0.01 0.004 0.005
Colusa Generating Station N/A 0.004 0.004
Fossil Plants 0.02 0.023 0.005
All Plants 0.003 0.003 0.0007
Total Particulate Matter Emissions (tons) 53 62 96
Humboldt Bay Power Plant 35 23 N/A
Humboldt Bay Generating Station N/A 16 51
Gateway Generating Station 18 22 19
Colusa Generating Station N/A 0.9 27
Total CO Emissions (tons) 156 123 43
Humboldt Bay Power Plant 142 100 N/A
Humboldt Bay Generating Station N/A 9 15
Gateway Generating Station 14 9 10
Colusa Generating Station N/A 6 18
Total VOC Emissions (tons) 38 54 74
Humboldt Bay Power Plant 31 28 N/A
Humboldt Bay Generating Station N/A 19 66
Gateway Generating Station 7 8 7
Colusa Generating Station N/A 0.02 1

1 Due to rounding conventions, some data above sum to an amount greater or less than the totals provided. Additionally, there were no reportable mercury emissions from PG&E’s facilities during 2009 to 2011.

2 The Humboldt Bay Power Plant (Humboldt Bay) facilities, two operating fossil fuel-fired plants and two mobile turbines, were retired at the end of September 2010.

3 The new high-performance Humboldt Bay Generating Station became operational in September 2010.

4 Gateway Generating Station became operational in January 2009.

5 Colusa Generating Station became operational in December 2010.

Benchmarking NOX and SO2 Emissions1
2008 2009 2010
National average, NOX 1.78 lbs/MWh 1.34 lbs/MWh 1.33 lbs/MWh
PG&E’s emissions rate, NOX 0.09 lbs/MWh 0.09 lbs/MWh 0.06 lbs/MWh
National average, SO2 4.19 lbs/MWh 3.33 lbs/MWh 2.88 lbs/MWh
PG&E’s emissions rate, SO2 0.002 lbs/MWh 0.003 lbs/MWh 0.003 lbs/MWh

1 Source of national average data is the U.S. Energy Information Administration’s Electric Power Annual report.

New Plants Under Contract

In 2010, PG&E received CPUC approval of several long-term power purchase contracts with new natural gas-fueled plants to be owned and operated by third-parties. Consistent with our corporate environmental and environmental justice policies, PG&E strives to minimize impacts from these facilities by considering and working to address their potential environmental and community impacts as part of our comprehensive due diligence process.

PG&E received CPUC approval to purchase power from a new third-party owned 719 MW peaker plant near Antioch. As part of the power purchase agreement for the new facility, the project developer agreed to retire two older existing boiler units that use once-through cooling before bringing the new plant online in 2013. Doing so will reduce local air and water impacts and demonstrates our commitment to environmental justice.

PG&E also received regulatory approval to purchase power from a new third-party-owned 184 MW natural gas plant to be built in Alameda County. Planned for 2012, the plant will be capable of starting rapidly when needed, which is especially important for integrating intermittent renewables into the grid. Two other third-party contracts receiving CPUC approval involved converting existing combustion turbine facilities into high-efficiency, higher-capacity combined cycle units—a 299 MW plant in Tracy expected to begin operations in 2012 and a 289 MW plant near San Jose expected to begin operations in 2013.