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Published on August 11th, 2013 | by Guest Contributor


Flexible Grid The Key To A Clean Energy Future

August 11th, 2013 by  

Editor’s note: We’re happy to feature this very useful and informative (exclusive) guest post from one the the solar industry’s true leaders, Arno Harris. This is an excellent piece that warrants a careful reading, or two. Enjoy it, and share it with your friends!

by Arno Harris

I’m looking forward to speaking at Senator Reid’s National Clean Energy Summit next week in Las Vegas. I’ll be on the “21st Century Energy Market” panel where we’ll address what can be done to make the grid friendlier to renewables while ensuring long-term access to affordable and reliable electricity.

This is an important conversation to have right now. Huge progress on costs has made renewables like wind and solar affordable and competitive. As a result, wind and solar are now two of the top three sources of new power generation planned by utilities. We’re entering the era of mainstream renewables where an increasing proportion of new power comes from clean sources.

With cost receding as the primary objection to renewables, our nation can “get clean” without breaking the bank. But that doesn’t mean we’re automatically going to get everything renewables have to offer. In order to get maximum impact—think 70% or more of our power coming from renewables—we need to begin making big changes to the way we operate the electric grid to make it more renewables-friendly.

The electric power grid (actually many regional grids) we have today is an amazing piece of engineering. It connects thousands of generators to millions of customers and delivers power so reliably we simply take it for granted. But it was built on a set of design assumptions that don’t fit today’s priorities. It assumed we’d have a big base of nuclear plants that ran steadily night and day, with hydro, gas- and coal-fired plants that could be ramped slowly up and down to meet demand for power.

By various estimates, today’s grid can probably accommodate 30%-40% renewable power with a few adjustments here and there. This is largely the approach we’ve taken so far to integrate renewables in the U.S. But getting to a 70%+ renewable scenario requires us to incorporate a different design assumption—that most of our power in the future will come from variable generators that create electricity when the sun shines and the wind blows.

Experts tell us that building a more renewables-friendly system requires us to evolve to a “flexible grid” designed around exactly that variability. A flexible grid can move power fluidly across regions from where it is generated to where it is used. It features large amounts of distributed generation and the ability to manage power demand by controlling large equipment that doesn’t have to run all the time. And it has quick-response resources like hydro and gas-fired generators (and storage) that can be ramped up and down quickly to cover short-term imbalances between supply and demand.

Broadly speaking, the changes needed to realize a “flexible grid” fall into four major areas:

  1. Regional Integration – we need more transmission lines and (just as important) we need agreements between regions to share resources and information about demand and available generation
  2. Demand-side Resources – we need to create markets or tariffs for distributed generation and demand-management that enables system operators to reduce, forecast, and control load
  3. Flexible Generation & Storage – we need to create markets for generation and storage that place value on the capability to ramp up and down quickly and maintain local power quality
  4. Forecasting & Scheduling – to make the most of all of the above, we need to give system operators access to current information about supply and demand plus the controls over transmission, generation, and load to make it all work together seamlessly

Moving forward on these efforts will be incremental and involve technical, market, and regulatory complexities. The form it takes will vary from region to region depending on resources and politics. And it will likely also force us to examine the role and business models of utilities; the current net-metering conflicts in the West demonstrate this challenge.

As always, it will also require us to sort out the costs and benefits and cost allocation. Some have already suggested imposing the cost of building flexible resources solely on renewable generators as an ‘integration cost,’ which creates a disincentive to building exactly the kind of resources we want to prioritize—these costs should instead be seen as part of the overhead of a flexible system that is necessary to achieve our overall system goals. While new investment in transmission and generation will certainly be required, most analysts also agree that there will be significant efficiencies from regional resource sharing that could create billions of dollars of annual savings.

In the West, this process of change is already underway. The California Independent System Operator (CAISO) recently announced an agreement with Pacificorp to create an energy imbalance market (EIM). The EIM is an important step forward in regional integration that will connect California’s grid to large areas of the Northwest. The two regions will exchange information on generation on 5-minute intervals and enable automated sharing of resources. The EIM’s success will hinge on our ability to remove barriers to new transmission. It will also require close harmonization with state RPS goals to ensure that sharing resources doesn’t create unintended consequences.

Bottom line: Change is required to evolve the kind of renewables-friendly “flexible grid” that will put us on path to a clean energy future. This kind of change won’t be easy and it will happen incrementally. But the effort and investment this evolution requires will be well worth it. The reward will be a cleaner, more reliable and affordable electrical system that can meet the needs of future generations for decades and centuries to come.

Author Bio: Arno Harris is CEO of Recurrent Energy, one of North America’s leading solar project development companies with 2GW of solar projects in development and a more than 700MW portfolio contracted with utilities. Arno is a passionate advocate for solutions to climate change through the intersection of business and public policy. He has spent the last 10 years working in the solar industry to help solar make the transition to mainstream energy markets. His success was recently recognized with the Rising Star at the 2011 Platts Global Energy Awards. Arno is board chair of the Solar Energy Industry Association (SEIA), representing 1000+ member companies as the voice of the solar industry in the U.S. He also serves on the board of Advanced Energy Economy and as an advisory committee member of the Division on Earth & Life Studies at the National Academies. He is a frequent speaker and commentator on renewable energy topics and publishes his views via his blog Clean Energy Future.

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  • Doug

    I’d like to better understand the economic trade offs between investments in transmission lines and electricity storage. Stated another way, is it better to further integrate our electrical grids or is it better to make each local grid more self sufficient? Each major market will undoubtably be different. I recall Hawaii considering investment in high voltage transmission lines between the islands – but this never made sense to me economically.

    • Bob_Wallace

      Yes. ;o)

      I’m sure the answer will be more transmission in some cases, more storage in others. I suspect transmission will play a large role in moving power into regions which are experiencing multi-day very low wind/solar inputs.

      Having good transmission between regions would mean less storage required, not only could supply be shared but also storage could be shared.

      And then there’s the issue of what storage will really cost. If we have only the options that we now have, pump-up and flow batteries, transmission would probably play a larger role. If we get a cheap storage technology like liquid metal batteries might provide then the scale swings in the other direction.

      With Hawaii they have the ability to put a lot of wind generation on ____ Island (forgot which one) and ship it to other islands. Shipping solar would be unnecessary. I don’t know how well geothermal is distributed between the various islands.

  • Steeple

    Since no one in America seems to be thrilled by the prospect of new transmission lines running anywhere, we’ll have to pursue other options. We need to continue to focus on the demand side as well thru energy saving technologies like LED lighting.

    • Bob_Wallace

      That would be a brilliant comment were it not for the fact that we are building new transmission lines all over the place.

      A new HVDC line running north from the Texas Panhandle. A new HVDC line carrying Oklahoma wind to Tennessee. A new HVDC line bringing Wyoming wind to the Pacific Coast. One in the upper Midwest. And we’re getting ready to lay one underwater to bring offshore wind to the grid. And there are more.

      Certainly efficiency is very important. You’re right there.

    • Bob_Wallace



      These projects support the integration of renewable resource generation. Renewable energy technologies include: wind power, solar power, hydroelectricity, geothermal, biomass and biofuels. Highlighted projects that facilitate the integration of renewable resources reflect the addition or upgrade of 13,300 miles of transmission with an accompanying investment cost of approximately $38.7 billion of the total $51.1 billion in this report (nominal $).

      500 kV Upgrade Project Badger Coulee

      Big Stone South to Ellendale

      CapX2020 Transmission

      Cardinal Bluffs

      Cimarron – Mathewson
      Double Circuit 345 kV Line

      Devers – Colorado River and Devers – Valley No. 2 Transmission Project

      Eldorado – Ivanpah Transmission Project

      Elk city – Gracemont 345 kV Line

      ETT CREZ

      G905 Generator Interconnection

      Grand Rivers Projects

      Great Northern Transmission Line

      Greater Fresno Area Upgrade Project

      Hitchland – Woodward 345 kV Transmission Line

      Hitchland – Woodward District EHV Double Circuit 345 kV Line

      Kansas V-Plan

      KETA Project

      Mathewson – Tatonga 2nd Circuit 345 kV Line

      Michigan Thumb Loop Transmission Project

      MidAmerican Energy Expansion Projects

      Midwest Portfolio Phase 1-7

      Multi-Value Projects 3 & 4

      Northeast Energy Link

      Northern Pass Transmission Project

      Oncor CREZ Development

      One Nevada 500 kV Transmission Intertie

      Palo Verde Hub – North Gila 500 kV Project

      Palo Verde Substation – Delaney Substation – Sun Valley Substation – Morgan Substation – Pinnacle Peak Substation 500 kV Projects

      Path 42

      Pawnee – Daniels Park 345 kV Transmission Line

      Pawnee – Smoky Hill 345 kV Transmission Project

      Pioneer Transmission, LLC

      Prairie Wind Transmission, LLC


      San Joaquin Cross Valley Loop

      Sibley – Nebraska City 345 kV Transmission Line

      South of Devers

      South of Kramer

      Straits Flow Control

      Tehachapi Renewable Transmission Project

      Tehachapi Wind Energy Storage Project

      Tuco – Woodward District 345 kV Transmission Line

      Woodward – Thistle Double Circuit 345 kV Line

      Woodward – Tuco 345 kV Line

      Woodward District EHV – Tatonga 2nd Circuit 345 kV Line

      Zephyr Power Transmission Project

      These are just the new transmission associated with renewables. There are pages of new transmission projects on their main site….

    • globi

      This is easy.
      If one wants to seriously reduce fossil fuel consumption, there’s no way around electrifying the hot-water-, heating- and transportation-sector and they all create flexible loads almost automatically.
      (Heat energy can be stored cheaply and electric vehicles need batteries anyway).

  • Bob_Wallace

    You know, it could also be the case that little will change in the way the grid operates. At least in the way it operates for consumers.

    Consider what could happen if Ambri’s liquid metal battery works as prototypes are working. That would give utilities extremely cheap storage. Wind is now cheap (6c/kWh without subsidies in the US) and solar will almost certainly get as cheap as wind.

    Worst case utilities might sell a mix of wind, solar and other renewables at only slightly more than what we now pay for a mix of coal, NG, nuclear and renewables. But because we are being successful with our efficiency measures the impact on the economy and budgets would be unnoticeable.

    Most of us would continue to get our electricity from a utility company. Some of us would produce electricity with solar panels on our roofs and act as suppliers for the grid, most wouldn’t.

    Even if the Ambri battery doesn’t materialize storage is likely to be cheaper at the utility level than at the end-user level. Individuals are not going to build pump-up hydro (currently our cheapest way to store electricity) nor build CAES into large subterranean caverns. Even using chemical batteries, utilities are going to be able to purchase at much better prices than will individuals due to their volume of purchase.

    Utilities will take a financial hit due to having to write off stranded resources (coal and gas plants). In the case of publicly owned utilities these costs will be passed on to customers or paid by taxpayers (so that the costs are less visible). Privately owned companies will attempt to get the costs passed on and will be successful in places with corrupt local governments. But these financial adjustments will be a temporary transitional problem.

    • MikeSmith866

      Its very easy for Arno Harris to write an article with general recommendations but ultimately we need engineers and economists to look at this.

      The Ambri giant battery is a new solution that is not yet priced but may eventually be a big factor in decision making. Like you don’t have to construct large expensive transmission lines if you have cheap storage.

      I also see your point about large centralized storage but if we can come up with cheap solar panels and in home storage as they have in New Zealand then decentralized storage may become a factor.

      I have a feeling too that wind and solar may end up topping out at say 50% with 50% of the power coming from main stream sources like hydro or nuclear that are always on. The % figures will depend on hydro power availability in each state and the evolution of costs for nuclear, wind, solar, storage and transmission lines.

      I think we need solid engineering on the projected costs and long term economic studies using the best projections of interest rates to come up with the best mix of solutions for each state.

      • Bob_Wallace

        I’d guess that solar will provide something like 30+% of our electricity. The Sun produces about 20% of the time and our consumption is highest when the Sun is up. Direct use is going to be cheaper than stored energy.

        Wind 50% or more. Again, direct use and the wind blows a lot of hours.

        Wind direct and solar direct will probably do about 100% of our EV charging. Parking over wireless outlets is such a simple technology to install and use that it makes sense to use EVs as a major way to match demand to supply.

        Hydro will largely be fill-in, cheaper than storage in most cases. Hydro, tidal and geothermal will, I guess, provide about 20%.

        (Those are very rough numbers and will, obviously, vary from location to location.)

        Nuclear is likely to die away over the next 20 years as we retire old plants and build almost no new ones. And one significant meltdown could cause a rapid abandonment of nuclear. Let Homer pop the top on one of our reactors in a western population center and nuclear is done.

        • MikeSmith866

          I like the part about EV charging. Its the type of thing that can permit variable use of power for load balancing. But if it happens mostly at night, load balancing may not be an issue.

          The price of storage will certainly effect how far we can go with solar and wind. The other issue is intermittency. If the wind stops blowing for say 5 days, then this could be a problem. But it could be that the sun shines best on doldrum days so with good sun and storage, maybe things would work out.

          I know that you are not enamoured with nuclear but a single nuclear plant in a state that has little hydro power could make a big difference.

          The Hoover Dam could drop below the hydro intakes in the next 10 years. If this happens, nuclear power may look a great deal more attractive for Arizona and Nevada.

          I wanted to include this link you gave me on tidal power.

          There is an absolutely phenominal amount of power in our tides and ocean currents. If we could ever figure this out, all states bordering on the oceans and even large rivers might get all their power from water flow.

          • Bob_Wallace

            Take a look at Fig.3, page 67 of the Budischak paper and see how often that mythical “5 days” actually occurs.

            And, remember, geothermal is cheaper than nuclear if there’s a need for ‘always on’ generation. Which is debatable.

          • MikeSmith866


            I don’t have to look at page 67, I can just look out the window.

            We had 5 days in a row with Lake Huron like glass in the second week of August.

            And I think we are going to see more of this as the jet streams get more disrupted by global warming. Here’s a couple of links


            Nobody really understands this yet but some of our old rules on intermittency may not apply in the future.

          • Bob_Wallace

            Did you happen to notice if the Sun came up at any time during those five days?

          • MikeSmith866

            Bob: I know where you are going and I agree with you. It does seem that on no wind days, we get clear skies.

            But I still think we have to be wary about intermittency being worse than what we have experienced in the past.

            Your point, I think, is that as long as we have 12 hours storage, we can get through the nights using stored sunshine and that may be true most of the time.

            My big toe is telling me that we should have some main stream power just in case. This is not going to be an exact science with global warming breathing up our backsides.

      • Matt

        One of the biggest problems with long term planning is the the estimates for cost from the big sources have almost zero value. Look at estimates for solar, wind, EV, storage ten years ago for today. Any of the big players even close? Heck some are predicting 2018 costs higher than today for wind/solar (WTF?). The second portion is that at some point we will get real on pricing CO2, that is going to push coal/oil/NG up. We can’t lie about the economic cost forever.

        • MikeSmith866

          Yes, you are making good points.

          Hopefully we are better at this today then we were 5 years ago but maybe not because technology is still evolving.

          Now about fossil prices. Remember there is no burden for the damage caused by Hurricane Sandy when the arrows are pointing to Global Warming. Ideally fossil fuels should be phased out on Policy without attempting to price out the damage burden.

  • Matt

    We also need to use the lessons learn in area that have made a lot of progress (Germany, Auz, Calf,…) to places that have only a little or none. One step that would likely help a lot would be the same approach we did for phone and Ma Bell. Make Split transmission and distribution from generation. Don’t allow management of one to have any ownership, board seats, etc in the other.

  • Omega Centauri

    Excellent article. We have to begin thinking about and planning for the next step after roughly 33% renewables penetration. We also have to begin creating the political/social climate that enables rather than inhibits this transition.

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