Geothermal's place in the U.S. power grid

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As states like California move forward with more aggressive Renewable Portfolio Standards (RPS) and seek to reduce greenhouse gas emissions, state officials need to consider the full value of the power sources they use, which is critical to ensuring that consumers get the most affordable overall system cost and recognizing the different reasons for choosing clean power sources.

The United States Navy's Coso Geothermal Powerplant in the Mojave Desert at the China Lake Navy Base, California.  Credit: U.S. Department of Energy

The California PUC recently noted active questions before policy makers in California and elsewhere, specifically: How increasing amounts of intermittent generation are impacting grid reliability, quantifying the impact and benefits of various resources to integrate intermittent generation, and what new policies should be adopted to manage the changing electric grid?

These questions are gaining in importance as the United States expands its renewable power production, which today means generating approximately 14 percent of the electricity nationwide. Much of this is coming from wind and solar photovoltaic technologies that rely heavily on the prevailing weather conditions in order to generate power.

New research from the Geothermal Energy Association (GEA) and Geothermal Resources Council (GRC) looks at geothermal as an alternative to intermittent renewable resources.

"Geothermal power offers both firm and flexible solutions to the changing U.S. power system by providing a range of services including but not limited to baseload, regulation, load following or energy imbalance, spinning reserve, non-spinning reserve, and replacement or supplemental reserve," according to the research.

The report contends that geothermal power production represents predictable output and long-lasting resources that quickly adjust to fit the needs set by variable renewable energy technologies.

"Having no reliance upon transitory environmental states such as wind and sunlight, geothermal facilities can produce electricity 24 hours a day, 7 days a week," the report says. "As a result, geothermal power plants have a high capacity factor, demonstrating a level of consistency not found in other sources."

The Energy Information Administration (EIA) reports that geothermal power has the highest capacity factor (92 percent) and uses existing transmission capacity efficiently because of its high capacity factor -- higher than coal (85 percent), gas (87 percent), or biomass (83 percent). For comparison's sake, the capacity factors for wind (34 percent), solar (20 percent) and solar PV (25 percent).

The retirement of coal plants will provide opportunities for geothermal power plant, which the report says represents the smallest carbon footprint and significantly lower CO2 emissions than coal or natural gas. The EIA estimates the average levelized cost for geothermal power at $89.60/MWh, slightly lower than coal, nuclear or biomass.

For more:
- see this report

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