U.S. Renewable Electricity Future Is Within Reach

, director of energy research, Clean Energy | August 8, 2012, 9:45 am EDT
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In June, the National Renewable Energy Laboratory (NREL) released a groundbreaking new study showing that the United States could generate 80 percent of its electricity from renewable energy by 2050 with commercially available technologies, while meeting electricity demand in every hour of the year and every region of the country.

The study also found that a high renewable electricity future would result in deep reductions in power plant carbon emissions and water use at costs comparable to other studies.

As one of 140 peer reviewers of this massive four-volume, 850-page Renewable Electricity Futures Study, it is arguably the most comprehensive analysis of a high renewable electricity future in the U.S. to date. It provides unprecedented geographic and time resolution for long-term studies of the U.S. power sector. It also includes a detailed assessment of the costs, challenges, and opportunities for each renewable energy technology and uses state-of-the-art modeling to show how they can be effectively integrated into the electricity system. More than 110 experts representing 35 diverse organizations contributed to this landmark study.

Here are some of the key findings:

No major technological breakthroughs are needed

The study shows that an 80 percent renewable electricity future can be achieved with diverse technologies that are commercially available today. These include wind turbines, solar photovoltaics (PV), concentrating solar power (CSP), biopower, geothermal, and hydropower. Wind and solar are the biggest winners, providing roughly half of total U.S. electricity generation by 2050. Biopower, geothermal, and hydro also make meaningful contributions for the remaining 30 percent. They did not include many emerging renewable energy technologies that have significant long-term potential, such as enhanced geothermal systems, wave and tidal power, floating platform offshore wind turbines, and solar nanotechnology.

Renewable energy can make a significant contribution in every region

While wind power expands in most regions, the highest levels are found in the Great Plains, Great Lakes, Central, Northeast, and Mid-Atlantic regions. Offshore wind represents a large share of wind development in the Northeast and Mid-Atlantic. Regions with the greatest deployment of solar power are the Southwest, California, Texas, Florida, and the Southeast. Biopower plays a smaller but important role in the Southeast, Great Plains, Great Lakes, and Central regions. Geothermal development is concentrated primarily in California and the Southwest. Hydropower continues to play a big role in the Northwest, but also makes an important contribution in California, the Northeast, and the Southeast.

Regional electricity generation and capacity in 2050 under 80% renewable electricity future

NREL has posted some very cool visualizations on their website that show how the U.S. electricity system could be transformed to a high renewable energy future between 2010 and 2050, and the hourly operation and transmission flow of that system in 2050.

Multiple technology pathways are available

The study shows an abundance and diversity of renewable energy geographically distributed across the United States, with a technical potential of over 128,000 gigawatts (GW) of capacity from commercially available technologies. That’s 128 times the current capacity of the U.S. electricity system!  Because of this, NREL’s modeling of over two dozen scenarios considering a wide range of assumptions and conditions show that many different combinations of technologies could be deployed to achieve a high renewable energy penetration.

Grid operators can keep the lights on in every hour of the year in every region

The study also shows that with a more flexible electricity system, grid operators would be able to balance electricity supply and demand in every hour of the year with 80 percent renewable electricity. This includes scenarios with nearly 50 percent of total U.S. electricity coming from variable wind and solar PV generation.

Using their Regional Energy Deployment Systems (ReEDs) model, NREL projected changes in generation, transmission, and power flows for 134 power control areas in the U.S. through 2050. Then they analyzed the hourly impacts of these results by running them through a detailed production cost model of the U.S. electricity system frequently used by the utility industry. Despite this highly rigorous modeling, NREL humbly notes that they did not conduct a full blown reliability analysis, which would include “sub-hourly, stability, and AC (alternating current) power flow analysis.”


Installed capacity is sufficient to meet summer afternoon peak demand with 80% renewable electricity and a more flexible grid.

A more flexible electricity system is needed

Achieving 80 percent renewable electricity will require making several fundamental changes to the grid. These changes include building new high voltage transmission lines, designating larger areas for balancing supply and demand, and smoothing out renewable generation from multiple facilities, improving scheduling (every 10-15 minutes) and forecasting of variable renewable resources, investing in electricity storage technologies, paying customers for reducing electricity use during high demand periods (a.k.a. demand response), and implementing several institutional reforms. While these are big changes, the good news is that the Federal Energy Regulatory Commission (FERC), regional grid operators, and utilities are already pursuing many of them.

Power plant carbon and GHG reductions

A renewable electricity future will have big climate and water benefits

Achieving an 80 percent renewable electricity future would reduce coal and natural gas use by about 80 percent by 2050. This translates into an 80 percent reduction in power plant carbon emissions that are contributing to climate change and a 50 percent reduction in water use for power plant cooling by 2050. This is significant considering that the power sector is currently responsible for more than 40 percent of both energy-related carbon emissions and total freshwater withdrawals in the United States.

NREL’s cost estimates are conservative

NREL found that “the direct incremental cost associated with high renewable generation is comparable to published cost estimates of other clean energy scenarios” modeled by federal agencies between 2009 and 2011.

They also found that improvement in the cost and performance of renewable technologies is the most important driver for reducing costs. Even under scenarios that use different assumptions for electricity demand, technology costs, and natural gas and coal prices or impose transmission, grid flexibility, and renewable resource constraints, they show that the United States can still achieve 80 percent renewable electricity by 2050 with only small changes in costs.



However, there are several reasons to believe that the study’s cost estimates are conservative:

  • For most scenarios, NREL assumes the United States will adopt policies to increase energy efficiency that will flatten out electricity demand over time, but they do not include any savings on consumer electricity bills from reducing electricity use. A 2009 UCS study of a high-efficiency and renewable energy scenario showed net annual savings of over $100 billion after paying for the costs of investing in efficiency and renewable energy.
  • It does not include any savings from reducing natural gas use for generating electricity that could lower natural gas prices and bills for consumers and businesses that use natural gas for heating buildings, industrial processes, and other uses. Studies by EIA and UCS of renewable electricity penetrations of 25 percent by 2025 have shown that savings on consumer natural gas bills can offset most or all of the projected increase in electricity bills.
  • It assumes new renewable energy facilities will primarily replace existing fossil and nuclear power plants that have already paid off some or all of their capital investment instead of replacing more expensive new plants.
  • The study uses technology assumptions developed in 2009 and early 2010 that don’t fully capture recent cost reductions for solar PV and projected near-term cost reductions for wind.
  • It does not include the environmental and public health benefits of reducing air and water pollution and solid wastes from mining, drilling, transporting, and burning fossil fuels or reducing disposal of radioactive wastes from nuclear power. And it doesn’t consider any avoided costs and impacts of climate change that would occur under their baseline scenario.

Policies are needed to achieve an 80 percent renewable electricity future

While the study does an excellent job describing the technical changes that would be needed to operate the U.S. electricity grid with 80 percent renewable electricity, it does not identify the policies that are needed to get there.

Perhaps the most important near-term opportunities are for Congress to extend renewable energy tax credits and for states to enact and strengthen policies such as renewable electricity standards. State and regional implementation of FERC Order 1000 and new power plant regulations to protect public health also provide near-term opportunities for renewables to replace retiring coal plants, build new transmission lines, and advance grid planning and integration approaches.

But to really achieve a high renewable future, drive down costs, create new jobs, and significantly reduce carbon emissions and water use, the United States needs a long-term national renewable energy policy. This should include a national renewable electricity standard or well-designed “clean” energy standard, a price on carbon emissions, and a significant increase in research and development funding.

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  • Bill

    CSP is the best – 99% efficient storage. The best solution is to implement sufficient CSP with 24 hour thermal storage to allow adequate energy. Since there is less energy available in the winter, it is useful to incorporate hydrogen storage as well.

    • Steve Clemmer

      NREL’s analysis includes 33-126 GW of concentrating solar power (CSP) with 8-12 hours of thermal storage under their core 80% by 2050 renewable energy scenarios. This represents 3.4% to 14.1% of total U.S. electricity generation by 2050. The highest levels of CSP are experienced under the scenarios with greater cost reductions, higher electricity demand, and constrained resources. NREL’s ReEDs model optimally sizes the amount of themal energy storage for CSP subject to a minimum level of 5 hours, which they claim is enough to provide firm capacity to the system. Most of the CSP with storage deployment occurs during the second half of the forecast as the level of variable generation from wind and solar PV increases.

  • Bill

    Curtailment should not be a part of the energy mix. Curtailment is zero percent efficient energy storage. Pumped-hydro is 78% efficient, and hydrogen storage is probably at least 25% efficient, which is infinitely better than zero percent efficient. When you are operating 100,000 MW of wind farms, you do not want to lose any production, and even 1% efficient storage is better than curtailment. Please recognize this important fact and re-do the calculations based on storage instead of curtailment. Thanks.

    • Steve Clemmer

      NREL acknowledges that curtailment is primary challenge of a system with high levels of variable renewable energy generation. They claim “curtailments reduce capacity factors and introduce uncertainty in electricity sales, thereby negatively impacting plant economics.” Their analysis shows that under the 80% by 2050 core scenarios, 8-10% of wind, solar, and hydropower generation would need to be curtailed. Most of this curtailment occurs during periods of low electricity demand. However, to help reduce the level of curtailment, the model adds 80-131 GW of storage –primarily compressed air energy storage–to the 20 GW of existing pumped storage hydro that currently exists in the U.S. The model also adds new transmission capacity in congested corridors to reduce curtailment and help alleviate congestion. They also list three other possible ways to reduce curtailment including: 1) increasing the size of reserve staring groups, 2) improving the flexibility of the thermal fleet, and 3) encouraging new and existing industries to purchase this low cost electricity instead of wasting it.

  • Pete

    Has anyone shared these magnificent findings with Germany or Japan? It should come as a tremendous relief to them!

    They are doing more than idly dreaming about renewable electricity — they have foolishly committed themselves to achieving it right away. Seems, less than 18 months in they already are having second thoughts about the feasibility of it. They could sure benefit from your wonderful guidance in this matter. Perhaps you could set one or both of those countries up as examples of your engineering triumph, sort of an incandescent shining city on the hill, as it were?

    • Steve Clemmer

      While Japan is still in the process of sorting this out, Germany is light years ahead of the U.S. in transitioning away from nuclear (and coal) power to renewable energy. Last fall, my colleague Jeff Deyette and I spent over a week in Germany learning about the country’s strong commitment and comprehensive plans to achieving this energy transition, as highlighted in this three-part series. The Heinrich Böll Foundation (HBF), who sponsored this trip, has also written an excellent piece on topic: Myths and Facts: The German Switch from Nuclear to Renewables. Among other things, this paper describes how nuclear power is not very compatible with a high renewable electricity future because nuclear plants cannot be ramped up and down quickly to help balance variable generation from wind and solar photovotaics. As confirmed in the NREL study, natural gas power plants are much better suited to play this role.