April 2013 (Union of Concerned Scientists)
Ramping Up Renewables
Renewable energy is providing reliable electricity today in the United States and around the world. From 2007 to 2012, electricity from renewable sources such as wind and solar nearly quadrupled nationally.
This growth is part of a transition away from dirty, coal-burning power plants—which harm public health and destabilize our climate—toward cleaner, more sustainable sources of electricity. Using existing technologies and smart policy decisions, the United States can continue this clean energy transformation while maintaining a reliable and affordable electricity system.
Transitioning to a system that relies heavily on wind and solar facilities—which provide variable amounts of power—does pose challenges to managing the electricity grid. After all, the wind doesn’t always blow and the sun doesn’t always shine, and grid operators must match electricity demand with supply each and every moment of the day (see Box 1, p. 2). However, meeting electricity demand in the face of variability and uncertainty is not a new concept for grid operators. They already make adjustments for constantly changing demand, planned power plant outages for maintenance, and outages stemming from severe weather, equipment failure, and other unexpected events. Adding variable energy sources to the system may increase the complexity of the challenge, but does not pose insurmountable technical problems or significant costs.
We know this because the U.S. grid and electricity grids throughout the world have already reliably integrated variable energy sources such as wind and solar power. We have the tools to significantly ramp up renewable energy use and keep the lights on. With ingenuity, innovation, and smart policies, we can fully transition to a clean, renewable electricity system.
Recent Growth in Wind and Solar Power
A number of utilities, states, and countries already have much higher percentages of renewable energy than many people thought possible just a few years ago (Figure 1). Wind power is growing rapidly in the United States—more than tripling from 2007 to 2012.
The nation broke a record in 2012, installing more than 13,000 megawatts (MW) of wind power capacity and investing $25 billion in the U.S. economy (AWEA 2013a). This made wind power the leading source of new capacity in the United States, representing 42 percent of the total, and surpassing new natural gas capacity.
While wind provided only 3.5 percent of the country’s electricity in 2012, several states and regions have reached much higher levels. For example:
• In 2012, wind power provided 24 percent of the electricity generated in Iowa and South Dakota, and more than 10 percent in seven other states (EIA 2013).
• On October 23, 2012, the Pacific Northwest set a new record as electricity from wind power exceeded that from hydropower for the first time ever (Sickinger 2012).
• On November 23, 2012, the Midwest set a record when more than 10,000 MW of wind power supplied 25 percent of the region’s electricity (Reuters 2012).
• On December 5, 2012, the Southwest Power Pool—which includes Kansas, Oklahoma, and the Texas panhandle—set a record as wind power supplied more than 30 percent of the region’s electricity (AWEA 2012b).
• On January 29, 2013, the main grid operator in Texas set a record when wind power produced 32 percent of total supply—enough to power 4.3 million average homes (AWEA 2013b; ERCOT 2013). Texas leads the nation in installed wind power capacity, with more than 12,200 MW at the end of 2012 (AWEA 2013a).
Solar power is also growing rapidly and supplying reliable electricity for U.S. consumers. The capacity of solar photovoltaics (PV) expanded by a factor of five from 2009 to 2012 (SEIA 2013). California leads the nation, with 35 percent of all U.S. PV capacity in 2012. New Jersey, Arizona, Hawaii, New Mexico, and New York have also seen significant investments in solar power during the past few years (Sherwood 2012). Some of the nation’s largest utilities are relying on significant levels of renewable energy. For example, renewables supplied 21 percent of the electricity Southern California Edison (SCE) sold to its 14 million customers in 2011, which included 7.5 percent from wind and solar (Karlstad 2012). SCE was the secondlargest retail supplier of solar power in 2011, and the third-largest supplier of wind power (AWEA 2012a; Campbell and Taylor 2012). SCE projects that wind and solar will supply 18 percent of its retail electricity sales by 2017, as the utility works to meet California’s renewable electricity standard of 33 percent by 2020 (Karlstad 2012).
Xcel Energy, a Minneapolis-based utility serving customers in eight states, was the largest retail provider of wind power in the United States in 2011, and the fifth-largest solar provider (AWEA 2012a; SEPA 2012). On April 15, 2012—a night when the winds were strong and electricity demand was low—Xcel set a new U.S. record by relying on wind to produce more than 57 percent of its customers’ power in Colorado (Laughlin 2012). Xcel is pursuing several approaches to integrating high levels of wind power into its system efficiently and affordably while maintaining reliability (see Box 2).
Globally, renewable energy accounted for almost half of the generating capacity added in 2011, with wind and solar PV accounting for 70 percent of that amount (REN21 2012). In the European Union, renewable sources supplied nearly 20 percent of all electricity consumed in 2010 and more than two-thirds of the total installed capacity in 2012 (EWEA 2013; REN21 2012). Wind supplied 30 percent of electricity in Denmark in 2012 (EWEA 2013). In Germany, renewable energy provided about 25 percent of electricity used in 2012, with more than half coming from wind and solar PV (Figure 2) (Böhme 2012).
On May 8, 2012, wind and solar reached a record 60 percent of total electricity use in Germany (NREL 2012). On April 19, 2012, wind power set a new record in Spain, generating 61 percent of the nation’s electricity (Casey 2012).
Replacing Conventional Power Plants with Renewable Energy Can Enhance Reliability
While integrating large amounts of variable renewable energy into the grid poses challenges to grid operators, conventional power plants present their own reliability challenges. The potential for a sudden outage at large coal and nuclear plants and transmission facilities means that grid operators must always have generation and transmission reserves on hand to immediately replace them.
Because of their size, those facilities also make the grid less flexible and more vulnerable to blackouts when they go offline. Severe weather events can also affect power plant reliability. For example, freezing temperatures during a cold snap in Texas in February 2011 disabled 152 power plants—mostly coal and natural gas—leading to rolling blackouts across the state (AWEA 2011). Local wind power facilities kept operating and provided enough electricity for hundreds of thousands of homes, reducing the severity of the blackouts. According to Trip Doggett, CEO of the Electric Reliability Council of Texas, “We put out a special word of thanks to the wind community because they did contribute significantly through this timeframe. Wind was blowing, and we had often 3,500 megawatts of wind generation during that morning peak” (Galbraith 2011).
During extremely hot weather, especially droughts, lakes and rivers may be too warm or lack enough water to cool large thermal power plants. For example, in 2007 and again in 2010 and 2011, the temperature of the Tennessee River rose above 90°F. That ensured the temperature of water discharged from the Tennessee Valley Authority’s Browns Ferry nuclear power station would exceed permitted limits, and forced extended reductions in output from the plant (NRC 2011). These cutbacks compelled the authority to purchase electricity at high prices, and cost ratepayers more than $50 million in higher electricity bills in 2010 (Kenward 2011; Amons 2007; Associated Press 2007).
Extreme weather events are expected to become more frequent and more severe because of climate change, which will further strain our reliance on such conventional generating sources. That means events such as Hurricane Sandy—which caused $70 billion to $80 billion in damage and widespread power outages for 8 million people from Virginia to Maine—will become more common (Lee 2012; Webb 2012). Yet renewable energy facilities in the Northeast appear to have weathered the hurricane much better than their fossil and nuclear counterparts (Wood 2012).
Just as diversifying investments strengthens a financial portfolio, adding new energy sources and technologies to the electricity grid can fortify its portfolio—improving its reliability in the process. Renewable resources are less vulnerable to prolonged interruptions in fuel supplies stemming from weather, transportation problems, safety concerns, terrorist threats, and embargoes.
And because renewable energy technologies are more modular than conventional power plants, the impact on the grid is usually insignificant when weather damages individual facilities. Because they do not rely on fuels that are subject to price spikes or long-term price increases, renewables also add price stability for consumers.
While we urgently need to transition to a cleaner, low-carbon energy system to reduce the impact and cost of climate change, this transition could take decades because of the enormous scale of the U.S. energy infrastructure, and the complexity of planning, building, and operating electricity grids. We may need to rely on some existing power plants to ensure a reliable electricity supply in some locations, at least in the near term. However, with enough lead time, we can replace such plants with renewable energy, more efficient technologies in homes and businesses, natural gas plants, transmission upgrades, energy storage, and other cleaner approaches.
Many Tools Are Available To Ramp Up Renewable Energy And Maintain Reliability…
…storage technologies include:
• Pumped hydroelectric. These plants store energy by pumping water to a higher elevation when electricity supply exceeds demand, and then allowing that water to run downhill through a turbine to produce electricity when demand exceeds supply. With 22 gigawatts (GW) of installed capacity in the United States—much of it built a generation ago to help accommodate inflexible nuclear power plants—pumped hydro is the largest source of storage in the power system today. However, the potential for more pumped hydroelectric storage is limited, as the long permitting process and high costs make financing new hydro facilities difficult.
• Thermal storage. Heat from the sun captured by concentrating solar plants can be stored in water, molten salts, or other fluids, and used to generate electricity for hours after sunset. Several such plants are operating or proposed in California, Arizona, and Nevada. The Bonneville Power Administration is also conducting a pilot program in the Northwest to store excess power from wind facilities in residential water heaters (Mason County PUD 2012).
• Compressed air energy storage. These systems use excess electricity to compress air and store it in underground caverns, like those used to store natural gas. The compressed air is then heated and used to generate electricity in a natural gas combustion turbine. Such facilities have been operating in Alabama and Europe for many years, and developers have proposed several new projects in Texas and California (Copelin 2012; Kessler 2012).
• Batteries. Batteries can also store renewable electricity, adding flexibility to the grid. AES Corp. is using 1.3 million batteries to store power at a wind project in West Virginia (Wald 2011). Batteries in plug-in electric vehicles can also store wind and solar energy, and then power the vehicles or provide electricity and stability to the grid when the vehicles are idle. A pilot project with the University of Delaware and utilities in the mid-Atlantic region showed that such vehicles could provide significant payoffs to both the grid and owners of electric vehicles, who would be paid for the use of their batteries (Tomic and Kempton 2007).
• Hydrogen. Excess electricity can also be used to split water molecules to produce hydrogen, which would be stored for later use. The hydrogen can then be used in a fuel cell, engine, or gas turbine to produce electricity without emissions. The National Renewable Energy Laboratory (NREL) has also researched the possibility of storing hydrogen produced from wind power in wind towers, for use in generating electricity when demand is high and the wind is not blowing (Kottenstette and Cottrell 2003).
Powering the Future with Renewable Energy
With these tools in hand, we can ramp up renewable energy to much higher levels. Leading countries and states have set strong targets for renewable energy to realize this future. At least 18 countries have binding renewable electricity standards (REN21 2012).
Denmark is aiming to produce 50 percent of its electricity from wind by 2025—and 100 percent of its electricity from renewable energy by 2050. Germany has a binding target to produce at least 35 percent of its electricity from renewable sources by 2020—with the target rising to 50 percent by 2030, and 80 percent by 2050. China also has a near-term target of producing 100 GW annually from wind, and is considering doubling its solar target to 40 GW by 2015. These targets are 40 percent higher than installed U.S. wind capacity, and more than five times U.S. solar capacity, as of the end of 2012.
The United States does not have a national target or other long-term policy to expand the use of renewable energy. However, 29 states and the District of Columbia (DC) have adopted renewable electricity standards, which require utilities to supply a growing share of power from renewable sources. DC and 17 states require at least 20 percent renewables by 2025. Hawaii and Maine have the highest renewable standards in percentage terms (40 percent by 2030), followed by California (33 percent by 2020), Colorado (30 percent by 2020), and Minnesota (27.5 percent by 2025) (UCS 2011).
Numerous studies show that we could transition to a low-carbon electricity system based on large shares of renewables within two decades, given the right policies and infrastructure. For example, detailed simulations by U.S. grid operators, utilities, and other experts have found that electricity systems in the eastern and western halves of the country could work by sourcing at least 30 percent of total electricity from wind—and that the West could work with another 5 percent from solar (EnerNex 2010; GE Energy 2010). Using energy storage technologies to balance out fluctuations in these resources would be helpful but not necessary, and not always economical, according to these analysts.
These simulations did show that such gains would require significant investments in new transmission capacity, along with changes in how the grid is operated (as noted above). Expanding transmission lines to allow wind power to supply 20 percent to 30 percent of the electricity used in the eastern United States in 2024 would require just 2 to 5 percent of the system’s total costs (EnerNex 2010). However, as noted, reductions in the cost of operating coal and natural gas plants would offset most or all of these new costs.
Other studies have shown that the United States can achieve even higher levels of renewable power while significantly reducing reliance on coal plants and maintaining a reliable, affordable, and much cleaner electricity system. For example, NREL has found that renewable energy technologies available now could supply 80 percent of U.S. electricity in 2050, while meeting demand every hour of the year in every region of the country (Figure 4) (NREL 2012). Under this scenario, wind and solar facilities provide nearly half of U.S. electricity in 2050. NREL also found that an electricity future based on high shares of renewables would deeply cut carbon emissions and water use.
Needed investments in new transmission infrastructure would average $6.5 billion per year, according to NREL—within the recent range of such costs for investor-owned utilities.
In Climate 2030, the Union of Concerned Scientists analyzed a scenario consistent with targets set by states that are leaders in clean energy investments (Cleetus et al. 2009). The analysis set a national target to cut U.S. carbon emissions 57 percent by 2030, and at least 80 percent by 2050. When combined with improvements in energy efficiency, renewable energy could reliably supply at least half of U.S. electricity needs by 2030, according to this analysis.
To achieve these targets, more than half of the renewable power would come from bioenergy, geothermal, hydro, and concentrating solar plants with thermal storage—technologies that can produce electricity around the clock, and during periods of high demand.
Variable power from wind and solar PV would provide 22 percent of total U.S. electricity by 2030. Another study found that investing in energy efficiency and renewable energy could allow the nation to phase out coal entirely, and significantly reduce reliance on nuclear power (Synapse 2011). A 2011 study by the Intergovernmental Panel on Climate Change concluded that renewable energy could reliably supply up to 77 percent of world energy needs by 2050 (IPCC 2011). And several studies have found that renewables could provide 100 percent of the world’s energy needs by 2050 (DeLuchhi and Jacobson 2011; WWF 2011; Jacobson and Delucchi 2010).
Accelerating the Transition to Renewable Energy
Achieving high levels of renewable energy will require a major transformation of the U.S. electricity system, as NREL’s analysis of attaining 80 percent of electricity from renewables by 2050 suggests:
This transformation, involving every element of the grid, from system planning through operation, would need to ensure adequate planning and operating reserves, increased flexibility of the electric system, and expanded multi-state transmission infrastructure, and would likely rely on the development and adoption of technology advances, new operating procedures, evolved business models, and new market rules (NREL 2012).
Both NREL and MIT’s Future of the Electric Grid show that a more flexible and smarter grid can overcome challenges to integrating renewables into the grid. However, these changes alone will not be enough to achieve a meaningful transition to renewable electricity. Strong state and national policies are needed to overcome market barriers to developing clean energy and the supporting technologies, and to more fully realize the economic and environmental benefits of transitioning away from coal. Policy support is essential to ensure continued growth of the renewable energy industry, and the cost reductions that come from learning, innovation, and economies of scale.
Expanding on the success of the 29 states with a renewable electricity standard by adopting a strong national standard of at least 25 percent renewables by 2025 can accelerate the transition to clean energy.
Targeted incentives—such as tax credits, direct payments, grants, and low-interest loans—and more funding for research and development are also important for lowering the costs of emerging renewable energy and integration technologies. Strong pollution control standards for coal power plants are also essential to protect public health and the environment.
A national commitment to renewable energy will deliver deep cuts in carbon and other heat-trapping emissions swiftly and efficiently, enabling us to avoid the worst impacts of climate change and help level the playing field between fossil fuels and cleaner, lowcarbon energy sources. As Climate 2030 showed, combining these policies with standards and incentives to invest in more energy-efficient appliances, buildings, and industries can curb energy use, reducing the need to build new power plants and significantly lowering the cost of reducing carbon emissions.
Other low-carbon technologies for producing electricity—such as advanced nuclear plants and fossil fuel plants with carbon capture and storage—may also become available to compete with advanced renewables. If they do, we will have even more opportunities to create a low-carbon energy system. Meanwhile, renewable energy technologies available now—along with investments in energy efficiency and the appropriate use of natural gas—can affordably get us most of the way there.
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