The least expensive way for the Western United States 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 (UC
The experts reached this conclusion using SWITCH, a highly detailed computer
model of the electric power grid for the states west of the Kansas/Colorado
border that will be an important tool for utilities and government planners.
“Decarbonization of the electric power sector is critical to achieving
greenhouse gas reductions that are needed for a sustainable future,” said
Daniel Kammen, Distinguished Professor of Energy in UC Berkeley’s Energy and Resources
Group. “To meet these carbon goals, coal has to go away from the region.”
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 carbon dioxide 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,” said
Kammen. “That is a modest cost considering that the future of the planet is at
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.
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.
The study, published in Energy Policy, highlights an analysis using
the SWITCH electricity planning model developed in Kammen’s Renewable and
Appropriate Energy Laboratory. SWITCH, which stands for Solar, Wind, Hydro and
Conventional generation and Transmission Investment, uses unprecedented detail
that includes generation, transmission, and storage of electricity.
“We use the SWITCH model to identify low-carbon supply options for the West,
and to see how intermittent generation may be deployed in the future,” said
first author James Nelson, a UC Berkeley graduate student. “We show that it is
possible to reach our goals of reducing carbon emissions using many possible
mixes of power, whether natural gas, nuclear, solar, wind, biomass, or
“Models like this are eagerly anticipated by many of the agencies involved
in planning,” Kammen said, noting that the model is now a prototype that could
be fine-tuned for specific users.
Setting targets for 2030 emissions
Mandates called Renewable Portfolio Standards (RPS) currently dominate carbon
reduction policy in the United
States. These standards require that a
certain fraction of electricity generation come from renewable sources. 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.
The UC Berkeley study concluded that current RPS targets are not sufficient
to put electric power sector emissions on track to limit atmospheric levels of
carbon to less than 450 ppm, a climate stabilization target recommended by the
Intergovernmental Panel on Climate Change. That target requires carbon
emissions from electricity production in industrialized countries to drop to no
more than 54% of 1990 emissions by 2030.
However, the study finds that the right mix of renewable energy sources can
meet climate goals given stronger carbon policy.
Of all 50 states, California
has been the most aggressive in setting goals for reducing carbon emissions,
with a target to return to 1990 levels by 2020. The first step along the path
of changing the balance of energy sources is the establishment of a carbon
trading market in California,
which will be up and running in September 2012, said Kammen.