NREL: Transmission Benefits Outweigh Costs

July 13, 2021

Department of Energy:

Periods of intense heat, cold, and other extreme weather can put significant stress on power systems as more people crank up the air conditioning or heat. But what if these periods of power system stress could be alleviated through a more fully integrated electric grid that spans the entire nation and efficiently and strategically shares power resources between regions? A recent study looked at the value of large-scale transmission projects that could accomplish just that.

The U.S. power system is divided into three major grids: the Western Interconnection, the Eastern Interconnection, and the Texas interconnection (overseen by the Electric Reliability Council of Texas, or ERCOT). These three grids operate almost independently of one another and share little power because of limited electricity transfer capacity. However, just east of the Rocky Mountains along the “seam” between the Western Interconnection and Eastern Interconnection, a collection of back-to-back converter stations enables 1,320 megawatts of electricity to flow—which is small compared to the size of the two networks.

Exploring the costs and benefits of enhancing the connections between grids offers insights as to the effects of shared energy resources. Strengthening these interconnections, by adding new or increasing the transfer capacity of existing connections, could help balance energy loads and increase efficient development and use of the nation’s abundant energy resources.

The study team conducted a transmission-planning analysis of the Western and Eastern Interconnections through 2038. They developed four transmission designs: (1) one in which existing seam capacity was maintained, (2) one in which back-to-back converter stations were expanded, (3) one that added three new HVDC transmission segments, and (4) one that simulated a national-scale HVDC network. The team then applied each design to eight different scenarios featuring varied assumptions about transmission costs, renewable generation, wind and solar costs, gas prices, and power plant retirements.

“Our multimodel approach allowed us to thoroughly evaluate the benefits and costs of the four transmission designs within each of the eight scenarios,” said study technical lead Novacheck. 

Through their analysis, the team found that expanding the means for intercontinental transmission would allow more U.S. homes and businesses to efficiently access and optimize their use of both fossil-fuel-based and renewable power when needed—and especially when the power grid was stressed, such as in heat waves or extreme weather.

“Our research showed that cross-seam transmission allowed more efficient use of renewable resources. For example, on hot summer days, excess solar from the Southwest could help serve peak electricity demand in the East. Then, as the sun sets on the West Coast, Midwest wind from the Eastern Interconnection could be sent back in the other direction,” said Novacheck. “By balancing loads across the country, we would be getting the benefit of competitive diversity among loads and among sources of generation.”

In addition, the study’s results showed that, for nearly every scenario studied, the benefits of increasing the transfer capability between the Western and Eastern Interconnections outweighed the costs by a ratio of at least $1.25 in net benefits for every $1 of cost and, in some cases, by a ratio of $2.90 in benefits for every $1 of cost. These benefits included reduced total system costs, such as transmission and generation infrastructure and operational costs. 

“These benefit-to-cost ratios either met or exceeded the industry threshold considered necessary to justify transmission investments,” said Novacheck. “This tells us that increasing transmission capacity and sharing generation resources between the Western and Eastern interconnections presents a significant value for all of the scenarios we studied.”

By simulating transmission and generation, the Interconnections Seam Study provides insight into how enhanced transmission could mitigate stresses on the power grid. The study includes areas for potential future work, including assessments of reliability, resilience, security, and the natural gas infrastructure.

12 Responses to “NREL: Transmission Benefits Outweigh Costs”

  1. ecoquant Says:

    There are arguments for keeping transmission to relatively short distances, say, less than 300 km. Cross-regional energy sharing might be done in other imaginative ways, whether they are long term, local regional energy storage, perhaps as compressed Hydrogen, or even sharing energy between regions by transporting compressed Hydrogen via electric trucks and trains.

    There is a proposal in the literature to have Australia synthesize Methane from chemical constituents bioproducts with heavy inputs of electrical energy, and ship that to Asia instead of the proposed long distance undersea electrical cables.

    Interestingly one of the scenarios in the Massachusetts Energy Pathways report from December of 2020 (“DER Breakthrough” scenario) increases the amount of rooftop PV and DER to reduce (but not eliminate by any means) the amount of utility scale solar and wind. (Storage is seen as a way of navigating long tail events.) Rooftop PV is acknowledged as being a grid stabilizing component in both Energy Pathways and the Massachusetts Decarbonization Roadmap.

    I wrote a bunch about all this just yesterday.

    • sailrick Says:

      Speaking of Australia

      World’s biggest wind and solar hydrogen hub planned for south-west Australia

      “The world’s biggest renewable energy hub – comprising an astonishing 50 gigawatts of wind and solar capacity – has been proposed for the southern coast of Western Australia to create millions of tonnes of green hydrogen for use in Australia and for export.

      It would would produce up to 3.5 million tonnes of green hydrogen or 20 million tonnes of green ammonia annually. …

      The consortium said the area featured a strong wind resource, with average speed of 9 metres per second, and good solar, with around 2,000kWh per square metre of solar irradiation. That translated into an expected capacity factor of around 70 per cent

      https://reneweconomy.com.au/worlds-biggest-renewable-energy-hub-planned-for-south-west-australia/

      • ecoquant Says:

        Hydrogen would be better than synthetic Methane, for sure.

        • rhymeswithgoalie Says:

          Hydrogen
          + not an ecological issue if it leaks
          – more ‘splody
          – requires more specialized pipes/tanks that resist embrittlement

          CH4
          + established infrastructure
          – pretty awful GHG
          – moderately ‘splody

          I have no idea how much of the existing pipeline/tanker infrastructure is vulnerable to hydrogen embrittlement.

          • Brent Jensen-Schmidt Says:

            As noted else where, apparently old coal gas largely/mostly Hydrogen and CO. OMG. This has caused questions about the embrittlement issue which never came up back then. I don’t know. Splody means goes bang bang?

    • Brent Jensen-Schmidt Says:

      Meh! Take electricity at point A, convert to hydrogen, pump by pipeline to point B, convert to electricity. Keep it simple and use wires to local nodes. Also removes conversion loses.

      • ecoquant Says:

        Local, yes. I said transmission to local. Distance is the problem.

        I think, too, the degree to which transmission is needed depends upon the degree to which the regions that it interconnects are autonomous or not. That depends in part on how equipped and overbuilt they are for supplying their own zero Carbon energy, and in part how geographically large they are, specifically, whether or not they extend over synoptic scales.

        If they are mostly autonomous, having continuous transmission lines between them may not be worth the capital investment, the loss of ecosystem continuity, and the fights to get these approved, as well as paying the computing resources and labor hours for the operators awhich keep the macrosystem balanced. That’s easier to do at the local level.

        I also assume long range transmission lines today can be designed to minimized effects of geomagnetic storms and the like.

        • Brent Jensen-Schmidt Says:

          Solutions will be neither simple or easy, the opposite in fact. Both local and national situations will need to be optimized (duh). Basic national blueprints should be established soonest. Probably already are in many countries, excepting Australia and the USA of course.

      • rhymeswithgoalie Says:

        [Can’t reply to nested comment.]
        AIUI* there are places, largely in the Northeast, which still run a lot of cast-iron pipe. Those would definitely need to be replaced.

        I recall stories from when I temp’d at a gas pipeline company of big steel pipe coming roaring out of the ground when breached with a backhoe. I think that H2 (as depicted in Chemistry lecture demonstrations) is even more eager to mate with oxygen.

        _______
        *Per chatter on The Energy Gang podcast.

        • Brent Jensen-Schmidt Says:

          Shall watch the recent iteration of ‘Hydrogen will save the world” with interest.

  2. rhymeswithgoalie Says:

    I can see the resistance to burying existing overhead lines, but new transmission lines should be buried from the get-go.

    (OK, I just like the idea of giant trenchers.)

    • greenman3610 Says:

      hopes are high for the ongoing SOO line construction, under grounding transmission along existing rail lines.
      If this works, could open up game changing pathways.


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