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The least expensive way for the Western US to reduce greenhouse gas emissions enough to help prevent the worst consequences of global warming is to replace coal with renewable and other sources of energy that may include nuclear power, according to a new study by University of California, Berkeley, researchers. Their paper is in press in the journal Energy Policy.

The researchers used a mixed-integer linear programming model—SWITCH (a loose acronym for Solar, Wind, Hydro and Conventional generators and Transmission)—to analyze least-cost generation, storage, and transmission capacity expansion for western North America under various policy and cost scenarios. Their analysis also found that current renewable portfolio standards (RPS) are insufficient to meet emission reduction targets by 2030 without new policy.

With a stronger carbon policy consistent with a 450 ppm climate stabilization scenario, power sector emissions can be reduced to 54% of 1990 levels by 2030 using different portfolios of existing generation technologies, they found. Under a range of resource cost scenarios, most coal power plants would be replaced by solar, wind, gas, and/or nuclear generation, with intermittent renewable sources providing at least 17% and as much as 29% of total power by 2030.

Although the carbon price to induce these deep carbon emission reductions is high, if the carbon price revenues are reinvested in the power sector, the cost of power is found to increase by at most 20% relative to business-as-usual projections.

Decarbonization of the electric power sector is critical to achieving greenhouse gas reductions that are needed for a sustainable future. To meet these carbon goals, coal has to go away from the region.

—Daniel Kammen, Distinguished Professor of Energy in UC Berkeley’s Energy and Resources Group

To achieve this level of decarbonization, policy changes are needed to cap or tax carbon emissions to provide an incentive to move toward low-carbon electricity sources, Kammen and the other study authors said.

While some previous studies have emphasized the high cost of carbon taxes or caps, the new study shows that replacing coal with more gas generation, as well as renewable sources like wind, solar and geothermal energy, would result in only a moderate increase to consumers in the cost of electric power—at most, 20%. They estimate a lower ratepayer cost, Kammen said, because the evolution of the electrical grid over the next 20 years—with coordinated construction of new power plants and transmission lines—would substantially reduce the actual consumer cost of meeting carbon emission targets.

While the carbon price required to induce these deep carbon emission reductions is high—between $59 and $87 per ton of CO2 emitted—the cost of power is predicted to increase by at most 20%, because the electricity system will redesign itself around a price or cap on carbon emissions. That is a modest cost considering that the future of the planet is at stake.

—Daniel Kammen

Burning coal, a non-renewable resource, produces about 20% of the world’s greenhouse gases, but also releases harmful chemicals into the environment such as mercury, sulfur dioxide, nitrogen oxides and sulfuric acid, responsible in some areas for acid rain and respiratory illness.

California has few coal-fired power plants, but gets about 20% of its electricity from coal-burning plants in neighboring states. About 46% of the state’s power comes from gas-burning plants, 11% from hydroelectric, 14% from nuclear and 11% from other renewables: geothermal energy, wind and solar.

While California has a relatively high RPS target of 33% renewable sources by 2020, other Western states have less ambitious targets. Additional policy action throughout Western North America will be required to meet climate targets, Kammen said.

Reposting of Mike Millikin repost of Robert Saunders from UC Berkeley News Center:

Coauthors of the study are Josiah Johnston, Ana Mileva, Ian Hoffman, Autumn Petros-Good and Christian Blanco of UC Berkeley’s RAEL lab and the Energy and Resources Group; and Matthias Fripp of the Environmental Change Group at Oxford University in the United Kingdom.

Funding for the Energy Policy study was provided by the National Science Foundation, the Environmental Protection Agency, NextEra Energy Resources, the Karsten Family Foundation, Vestas Wind LLC, the UC Berkeley Class of 1935, the CPV Consortium, the Berkeley Nerds Fellowship and the Link Energy Fellowship.


  • James Nelson, Josiah Johnston, Ana Mileva, Matthias Fripp, Ian Hoffman, Autumn Petros-Good, Christian Blanco, Daniel M. Kammen (2012) High-resolution modeling of the western North American power system demonstrates low-cost and low-carbon futures, Energy Policy doi: 10.1016/j.enpol.2012.01.031