least expensive way for the Western U.S. 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.
experts reached this conclusion using SWITCH, a highly detailed
computer model of the electric power grid, to study generation,
transmission and storage options for the states west of the
Kansas/Colorado border. The model will be an important tool for
utilities and government planners.
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
One example of low-cost, low-carbon energy generation and transmission around the West by 2030.
possible scenario for the electricity system in the Western U.S. in
2026-29. Pie charts show the proportion of different types of energy
sources generating power and flowing between load areas if there were a
carbon tax of $70 per ton. According to the SWITCH model, such a tax
could allow the West to reach a goal of 54% of 1990 emissions by 2030.
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.
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.
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,” said Kammen. “That is a modest cost considering that the
future of the planet is at stake.”
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
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
study, published in the April issue of the journal Energy Policy,
highlights an analysis using the SWITCH electricity planning model.
SWITCH, which stands for Solar, Wind, Hydro and Conventional generation
and Transmission Investment, uses unprecedented detail that includes
generation, transmission and storage of electricity. The model was
developed by Matthias Fripp to study California’s renewable energy
options while he was a Ph.D. student at UC Berkeley. Kammen and his
group extended the model’s capabilities and used it to study Western
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 geothermal.”
like this are eagerly anticipated by many of the agencies involved in
planning,” Kammen said, noting that SWITCH is a power-system model that
can be fine-tuned for many different types of studies.
Setting targets for 2030 emissions
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 percent
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.
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
However, the study finds that the right mix of renewable energy sources can meet climate goals given stronger carbon policy.
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.
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.
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.
High-resolution modeling of the western North American power system demonstrates low-cost and low-carbon futures
Professor Kammen’s laboratory website