Published on April 13th, 2015 | by Guest Contributor


80% Renewables By 2050 In US, Says NREL

April 13th, 2015 by  

By “He who shall not be named”

There are many ways to achieve high renewable penetration levels.

According to an NREL study examining high renewable energy integration in the US, 80% of US electricity could be coming from renewables by 2050.

Feel free to copy the above paragraph & link and use in response to incorrect claims that renewable energy can’t provide most of our electricity needs.

For responses to other anti-cleantech myths, see: Anti-Cleantech Myths Debunked (Your #1 Resource).

How can high levels of renewable energy be integrated when wind and solar resources are variable? First of all, it’s important to remember that wind and solar are not the only renewables out there. High overall renewable energy integration can be achieved via a composite of regions with different integration levels and different means.

Some think of renewables as only wind or solar, and that they must supply all of the load in a small region. However, considering the large area of the US, a high level of renewables can be achieved without requiring every region to meet the same integration levels. Wind and solar are not the only sources of renewable energy, and storage need not be more than a small fraction of total capacity.

While it might at first be difficult imagining wind turbines supplying all of the electricity in one region, this is not how a renewables-centered future will operate. Variable renewables will be mixed with dispatchable ones like geothermal and hydro to produce the desired result. And different regions will have different mixes of renewables, sometimes relying on neighbors sending energy over transmission lines, like borrowing a cup of sugar. 80% renewables will not be 80% wind and solar in each city, region, or state —  some places will have over 80% renewables, while others will have under 80% renewables.

The Power System: How Does It Work?

The power system is a complex system of generators, transmission lines, and distribution equipment overseen by system operators that keep generation matched with demand. Demand varies throughout the year, reaching a peak in the summer afternoon and changing shape year round.

electricity demand change

System operators work like air traffic controllers, forecasting demand and generation daily. Large generators are often slow to respond and need time to be at full capacity. Operators forecast day-ahead demand and schedule generation accordingly. Since the load changes rapidly during the day, large and slow-moving baseload generators must be combined with faster-responding peaker units to meet load. Operators can also adjust demand. During times of excessive demand, the operator has agreements with major electric consumers, like aluminum smelters and water pumps, to decrease demand. Operators use transmission, flexibility, and resources to match demand.

Like a good cook must keep extra ingredients in the pantry, a system operator must also keep generation reserves available in case generators malfunction or load increases unexpectedly because of forecast error. Because generation and transmission capacity must be sized to exceed the maximum annual demand, sizable reserve generation must be available all year. The power system is already designed to respond to the changing whimsical demands of the Superbowl, New Year’s Day, and big soccer games. This is one reason NREL found variable renewables can be integrated up to 35% with little effect on the existing system. (Similar findings have been made in Europe as well.)

The operator must also consider transmission and distribution equipment limits. During hot days, transmission lines must carry lower currents. Sometimes loads are too high in a small area. High demand can cause local congestion. If too much demand is placed on a transmission line, power must be routed another way. Power professionals use tools to analyze the effects of demand variation on generation and transmission to plan power system needs.

Men and Women at Work: NREL Used Tools and Techniques Used for Conventional Systems

In the study noted above, NREL used software programs to consider renewables in the US over a range of future scenarios, including from 30% to 90% renewables, with variations in assumed technology improvement, future electricity demand, and fossil fuel cost. One tool was used to considered generation and load matching. A different tool was used to look at transmission lines to study requirements needed to meet demand. Thousands of simulations were run to determine generation, demand, and transmission balance. The study was based on 2010 renewable technology and included only improvements to technologies available then. Technologies such as enhanced geothermal, ocean technology, and floating offshore wind were excluded, as were cost declines in solar and wind power. It did include an expectation of increased demand due to electric vehicles.

How Did NREL Balance Sources To Demand? The Recipe

Many people, when they think of a “renewable energy grid,” they think only of sunshine and wind producing the energy, but there is much more to a renewable grid than that. A cake is not just made of sugar.

renewable energy growth US

The capacity and generation mix for 80% renewables by 2050 can be examined in two charts on page xxx of the study (screenshots above).

The generation mix shows 38% wind, 6% PV, and 6% CSP in the generation mix, neatly dividing electricity generation at about 50% variable renewables. Hydropower and biomass each make up about 15%, comprising about 30% dispatchable renewables. The remaining 20% generation is conventional. Only a small percentage of storage is included.

Of course, at any given time, the amounts of each source may vary, and the total capacity exceeds demand all of the time, with some in reserve.

With 50% from variable renewables, 30% dispatchable renewables, about 10% storage, and considering that some capacity is always in reserve, it is much easier to see why variable renewables can be integrated successfully.

What those numbers don’t show is how geographic dispersal, new system operations like Energy Imbalance Markets, transmission between regions, and demand response ease demand balancing. Those effects are baked into the simulations. The results show that variable renewables like wind and solar are not the only sources of renewable energy, and that storage is only a small fraction of total capacity.

Page xxxvi, Figure ES-6, shows an hourly dispatch curve, to give an example of the lowest coincident load and summer peak load responses, giving an idea of how they could be met. The study itself consists of many simulations of years of load data and generation mixes.

Particular attention was concentrated on the results of the 80% scenario. The US was divided into regions with results detailed for each. Some regions achieved higher integration and others less, while the balance of the US composite was 80% renewables.

Different Recipes for Different Folks

US renewable energy potential

You can get a general sense of the regions’ diverse renewable energy potential from the maps on page xxv (screenshot seen above). On page xxxii, you can examine the graphs of each region to understand the amounts of renewable energy for each region under an 80% renewable scenario.

As an example, the Pacific Northwest (PNW) achieved higher renewables integration than other regions. That area has abundant hydro and wind resources, and relatively low demand, so it’s presumed Paul Bunyan can send a little excess energy to Pecos Bill. Currently, there are also plans to transmit large amounts of wind energy from the Midwest to the East Coast and other regions.

In the end, the study concluded that 80% renewables by 2050 could be achieved and would be robust against constraints in transmission, flexibility, and resources. “Multiple technology pathways exist to achieve a high renewable electricity future. Assumed constraints, which limit power system infrastructure, grid flexibility, or the use of particular types of resources can be compensated through the use of other resources, technologies, and approaches.” Even under the high-demand scenario, demand was met by supply.

Here’s more from NREL’s Renewable Futures Study:

  • Renewable electricity generation from technologies that are commercially available today, in combination with a more flexible electric system, is more than adequate to supply 80% of total U.S. electricity generation in 2050 while meeting electricity demand on an hourly basis in every region of the country.
  • Increased electric system flexibility, needed to enable electricity supply and demand balance with high levels of renewable generation, can come from a portfolio of supply- and demand-side options, including flexible conventional generation, grid storage, new transmission, more responsive loads, and changes in power system operations.
  • The abundance and diversity of U.S. renewable energy resources can support multiple combinations of renewable technologies that result in deep reductions in electric sector greenhouse gas emissions and water use.
  • The direct incremental cost associated with high renewable generation is comparable to published cost estimates of other clean energy scenarios. Improvement in the cost and performance of renewable technologies is the most impactful lever for reducing this incremental cost.

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  • Bill

    The article’s title unfortunately perpetuates the confusion of “energy” and “electricity”, which in USA and most developed countries supplies about one-third of total energy consumption. Claiming “80% of energy from renewables” is incorrect and confusing to the public and decisionmakers. No wonder we haven’t a comprehensive energy policy for a benign, equitable, affordable, global energy future. Humanity’s obligation is nothing less that reconstructing the world’s largest industry, from ~85% fossil to ~100% renewable sources, as quickly as we prudently and profitably can. The “energy – electricity” confusion doesn’t help us compose and commit to the vision to do that.

    • eveee

      Not exactly. It says electricity right after the headline, for one. For another, the NREL study includes electric vehicles. So while it is only for electricity, it does include future uses of electricity that are now powered only by FF. It envisions a society that is much more driven by electricity for all forms of energy than today.
      Also, where do you get that it has to be 100% by 2050?

  • Matthew Rose

    I’m skeptical on their solar assumptions. Aren’t solar installations presently outpacing wind turbines? Yet this information is suggesting solar capacity will be less than one-half of wind.

    Unless they have left of a significant amount of solar due to people removing themselves from the grid opting instead to maintain on-site storage.

    • Bob_Wallace

      Are you perhaps looking at ‘nameplate capacity’?

      US onshore wind is now running over 40% output of nameplate or capacity factor (CF). PV solar runs something more like 20%.

      Grossly generalizing, one would need to install twice as many MW of solar to equal one MW of wind.

      • Matthew Rose

        Those charts are presented as Installed Capacity. I do not see them referencing capacity factor.

        Or, was there a change to citing solar installations by applying relative capacity factor?

        • Bob_Wallace

          The two bar charts at the bottom of the article. The top one is installed. The bottom is output.

          Aside from that I would say that they are “chart failures”.

          Those are hard to read charts and I hate how people are now using “shades” rather than colors.

          Tops chart breaks out rooftop and utility PV. Bottom chart lumps them together.

          Need to present both as percentages. Then you might be able to see how CF interacts with installed. (I assume they got it right).

          BTW, I’m not spending much time with those charts. Their predictions just don’t seem right. I can’t image the US will be using any coal in 2050. And I don’t see where that much nuclear will come from, All but five reactors will be long ago aged out.

          And they’re showing a pathetic amount of install PV. They’re showing about 100 GW after 35 more years. The US installed 6.2 GW of PV in 2014. We’re already close to 20 GW. That would mean installing only a couple GW per year going forward.

    • eveee

      In the opening comments of the report, NREL makes note of the fact that rapid solar advances and the drop in natural gas prices happened just after the study, with data from about 2010. They also say their conclusions are still similar, since they concluded there are many ways of achieving the same result.
      In that context, it suggests that it may be somewhat easier in light of solars great strides. IMO, there is good reason to believe solar will play a much larger role by 2050 than the report modestly predicts.

      • From what I learned from the folks at Younicos, it’s very reasonable to assume that renewables get up to ~80% penetration. Above that, there tends to be a seasonal challenge (more so in Europe, I assume) that is harder to cross.

        So, I presume the idea that we can get to 80% renewables by 2050 is true but conservative, but beyond that is the bigger challenge.

        Of course, you can overbuild capacity to meet those difficult periods, but there’s a point where that doesn’t become cost-effective. And there are some forms of storage that will fill much of the gap, but likely not 100%.

        Of course, we are far from 80%, and by that time, who knows what the best option will be (overbuilding renewables, storage, some use of natural gas…?). I am hoping we can speed up and get to 80% renewables by 2030. Wouldn’t that be nice!

        • Bob_Wallace

          One way we deal with seasonal differences now is to just turn off some coal plants during low-demand seasons. One option would be to convert coal plants to biomass burners and stock up fuel.

          • eveee

            The option of converting coal to biomass seemed high on the study authors minds. This topic is not as popular today. Perspectives have changed with new technology breakthroughs. They only envisioned about 5% solar PV and 10% CSP if I remember correctly. That’s off now.

  • Shiggity


    • oy, you scared me that we made a mistake.

      but i do agree.

    • Matt

      Well they assume 2010 cost, no improvements from scale or technical work. So yes they get to 80% in 2050 instead of a earlier data. And of course assume no market correction for FF externals or cuts to their support; both which could/should move the transition forward.

      • eveee

        They made multiple scenarios for different FF assumptions. The study is very wide ranging, which makes it powerful. Unfortunately, its so thick, that it tends to only be read by few.
        They make pains to point out that government support, both in policy and other support has an appreciable effect, but stayed primarily with technical areas for prediction.

  • Guest

    Nice! It even shows the effects of Daylight Saving Time on the timing of the peak load between April and October!

  • vensonata

    It often comes up on articles about “electricity” percentage that “energy”demand is a different and much larger category which is usually tainted by fossil fuel. But consider that as transport and other “energy” demands become electrical in nature, the difference between energy and electricity may fade away. Thus 80% of electricity might also be 70% of energy supply by 2050.

    • eveee

      Thanks for noticing that they included some expansion in electricity usage for transportation. Thats particularly interesting because of the need to lower GHG in transportation. The fact that they included transportation makes this study that much stronger.

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