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US Electrical Grid More Reliable with Renewables

Renewables on the grid: a swift transition?


If the U.S. ceases to burn coal, shuts down a quarter of existing nuclear reactors, and trims its use of natural gas by 2050, the resulting increased reliance on wind, solar and other renewables will not result in a less reliable electricity grid, according to a major new report prepared by Synapse Energy Economics, Inc., for the nonprofit Civil Society Institute (CSI).

The new study finds that, in the envisioned 2050 with a heavy reliance on renewables, regional electricity generation supply could meet or exceed demand in 99.4 percent of hours, with load being met without imports from other regions and without turning to reserve storage.  In addition, surplus power would be available to export in 8.6 percent of all hours, providing an ample safety net where needed from one region of the U.S. to the next.

Grant Smith, senior energy analyst, Civil Society Institute said: “This study shows that the U.S. electricity grid could integrate and balance many times the current level of renewables with no additional reliability issues. Recent improvements in both renewable technologies themselves and in the technologies that are used to control and balance the grid have been proceeding at a rapid pace, and the incentives and rewards for success in this area continue to drive substantial progress. In contrast, the alternative—continuing to rely on increasing combustion of fossil fuels to generate electricity, and producing ever-increasing levels of greenhouse gases—is far less feasible, and presents much more daunting technical, economic, and social challenges to human and environmental welfare. In comparison, the challenge of integrating increasing levels of solar and wind power on the U.S. power grids requires only incremental improvements in technology and operational practices.”

Report co-author Dr. Thomas Vitolo, analyst, Synapse Energy Economics, Inc.: “Put simply, the message today is this:  It is a myth to say that the United States cannot rely on renewables for the bulk of its electricity generation.  This study finds that the projected mixes, based entirely on existing technology and operational practices, are capable of balancing projected load in 2030 and 2050 for each region—in nearly every hour of every season of the year.”

In 2011, Synapse prepared a study for the Civil Society Institute that introduced a “Transition Scenario” in which the United States retires all of its coal plants and a quarter of its nuclear plants by 2050, moving instead toward a power system based on energy efficiency and renewable energy.  The Synapse study for CSI showed that this Transition Scenario, in addition to achieving significant reductions in emissions of carbon dioxide (CO2) and other pollutants, ultimately costs society less than a “business as usual” status quo strategy -- even without considering the cost of carbon. The 2011 study also projected that, over 40 years, the Transition Scenario would result in savings of $83 billion (present value) compared to the status quo strategy.

To achieve these lower-cost and low-emissions results, the Transition Scenario included large amounts of renewable energy resources with “variable output,” such as wind and solar. While the need for variable-output resources is well defined, questions have been raised about the impact of large-scale wind and solar integration on electric system reliability.  To address this, Synapse paid careful attention to the amount of wind and solar in each region when designing the Transition Scenario for the 2011 report, taking steps to ensure that the projected regional resource mixes could respond to all load conditions.

The new 2013 study for the Civil Society Institute takes the analysis one big step farther, in order to explore the extent to which the Transition Scenario’s resource mixes for 2030 and 2050 are capable of meeting projected load for each of the 10 studied regions — not just during peak demand conditions, but in every hour of every season of the year as consumers require.


Synapse developed a spreadsheet-based hourly dispatch model to test the capability of the Transition Scenario resource mix in each study region to meet hourly demand in that region. Hourly load data for each region was based on 2010 actual demand, and was adjusted — considering changes in demographics, wealth, and energy efficiency—so that the peak load and annual energy requirements closely matched those in the 2011 Transition Scenario. Data for these tasks were obtained from FERC 2011, NERC 2012, and U.S. EPA 2011. The generators used in the model came from the BBAU 2011 Transition Scenario.

To model the hourly generation of variable resources, a number of National Renewable Energy Laboratory (NREL) studies and data sets were used. To model hourly wind generation, data sets from NREL’s Eastern Wind Integration and Transmission Study (EnerNex Corporation 2011) and Western Wind and Solar Integration Study (GE Energy 2010) were applied to the power curve of a Vestas V 112 3.0 MW turbine. To model solar output, site specific data from NRELs PVWatts calculator was used. Annual hydroelectric capacity factors from the 2011 report were used for the Northeast, Southeast, Eastern Midwest, and Texas regions; monthly hydroelectric capacity factors from the U.S. Bureau of Reclamation were used for the Northwest, California, Arizona/New Mexico, Rocky Mountains, Western Midwest, and South Central regions.

SOURCE: Civil Society Institute

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