Compressed Air Storage Breakthrough

September 26, 2013


Simple idea. Storing energy as compressed air. It’s been done before, but with a fossil fuel assist that made it more carbon intensive and expensive.

This is a big deal. There will probably not be a one size fits all answer to energy storage – and storage is not needed nearly as much as some people think, but improvements like this will give planners more options and flexibility in designing distributed systems in coming years.

Daily Fusion:

SustainX, an energy storage technology developer, has completed construction and begun startup of the world’s first megawatt-scale isothermal compressed air energy storage (ICAES) system (detailed description available here). The system stores and returns megawatts of electricity to provide long-term grid stability and support integration of renewable energy sources like wind and solar.

The 1.5-megawatt isothermal compressed air energy storage system is located at SustainX headquarters in Seabrook, New Hampshire. It takes electricity from the grid and uses it to drive a motor that compresses air and stores it isothermally, or at near-constant temperature. To do so it captures the heat produced during compression, traps it in water, and stores the warmed air-water mixture in pipes. When electricity is needed back on the grid, the process reverses and the air expands, driving a generator. No fossil fuel is needed to reheat the air and no emissions are produced, making ICAES a safe and sustainable energy storage solution.

“Our isothermal CAES technology is a dramatic improvement over other bulk energy storage methods because it uses no fuel, produces no emissions, is power- and energy scalable, and can be sited virtually anywhere,” said Tom Zarrella, SustainX president and CEO. “Thanks to numerous innovations on core system elements, SustainX has developed, proven, patented and now built the key enabling technologies for isothermal CAES. We believe this places our company at the forefront of large-scale energy storage system development and commercialization.”

The system can be scaled in both power (megawatts) and energy (megawatt-hours) depending on the application, and can be located where needed thanks to its use of standard pipeline storage and clean, emission-free operation. Because it’s based on proven mechanical principles and mature industrial components, the system has a 20-year operating life with a very low levelized cost of energy, enabling cost-effective, large-scale storage of electricity. Unlike chemical battery systems, ICAES performance does not degrade over its lifetime or need frequent replacement. No hazardous materials are used.

SustainX isothermal compressed air energy storage technology is a significant improvement over conventional compressed air energy storage (CAES) systems, which have existed since the 1970s. CAES systems burn fossil fuel and are greatly limited by the need for specific geological locations (i.e. caverns) for air storage—as well as substantial investments in time and money. Because of these limitations, there are only two such installations worldwide. SustainX’s ICAES is the first megawatt-scale compressed air energy storage system built anywhere since 1991, and represents an opportunity to expand the availability and use of this bulk energy storage method.

18 Responses to “Compressed Air Storage Breakthrough”

  1. Now if they only would make one that stores only the CO2. 🙂

    • I’ve run the numbers on that idea.  The amount of CO2 in the air being cycled through even a very large CAES system is trifling.  It’s not worth the effort to try to capture it.

  2. MorinMoss Says:

    When I first heard about this, I overlooked the fact that this method isn’t simply a natgas turbocharger.
    That’s a very welcome innovation.

    I’ve not been to the Daily Fusion site before – the layout’s isn’t appealing but they have stories I’ve not seen elsewhere such as:

    Solid-state lithium-ion with iron-sulfur composite cathode? Interesting.

  3. Bruce Miller Says:

    Very good circumstance specific technology! We will see systems like this abound now that the gateway to U.S. plundering lesser countries for their oil has been closed at Syria by the Russian/Chinese/Iranian/ U.N. collusion, and the world’s Oil energy prices will no longer be manipulated by the U.S. Petro Dollar and the Feds. u.S. can expect only rising prices for oil, making energy conservations systems like this evermore valuable to her survival. my Question: In combination with Wind Turbine Farm can this technology yield higher efficiency rate? Satisfy the American peon’s demands? Can the American peon afford this?

  4. What this really needs is a carbon-free thermal assist on the expansion end.

    SustainX uses water as the heat-transfer fluid on both compression and expansion.  But what if they used something else, like an oil, on expansion?  The oil could be heated to 150°C or more to hold the expanding air well above its compression temperature and volume, making the system a net generator of electricity.

    Where to get this heat?  Why not tap steam from nuclear power plants?  The issue there is that a peaking plant integrated with a nuclear station needs to be a fair fraction of a GW, not a megawatt.

    • How about solar thermal?

      • What does a mmBTU of heat from solar thermal at 150°C cost, compared to tapping steam from a medium-pressure steam turbine?  Figuring 0.7¢/kWh(e) fuel cost for nuclear and 33% net efficiency, I get about 68¢/mmBTU for the uranium.  The actual cost of the steam would be less, because you’ve already tapped off a substantial amount of its available energy in the expansion from high pressure and ~300°C down to medium pressure and 150°C.

        How reliable is that solar thermal heat, and what could you use for backup?

        Holy crap, now I’ve got an idea I need to look at really carefully.

        • greenman3610 Says:

          the heat utilized here is from the adiabatic heat of compression. the heat is released during expansion. that’s the whole point. don’t need nuclear, or gas, or any input other than spare off-peak electricity to run the pump.
          This has been a theoretical idea for a while, now it looks like someone has figured it out.
          suspect this will be scaled up soon, either as a series of modules or a larger capacity device.

          • I was wondering what it would take to make the system a net electric generator, which the base system does not do (but many CAES systems are designed to do).  Capturing and restoring the heat of compression does not do this.  Earlier items on SustainX included speculation on adding heat to the water for the expansion phase.  These things need to be evaluated, comprehensively.

  5. redskylite Says:

    This world map and temperature percentiles for 2013 from NOAA speaks a thousand worlds and presents the problem in instantly understandably terms.

    If people, governments and rulers are still not convinced then I despair

    • MorinMoss Says:

      Not only is there so much of the Pacific that warmer than average but that “record warmest” patch north of Papua New Guinea and enveloping the Philippines looks to be 1/2 the size of Australia.

      How long did those conditions last?

  6. what we need is an efficient scale down version that fits for house hold instalations.
    Like solar panels the scale up advantage is in its dispersed deployment.

  7. kap55 Says:

    A very interesting and important concept. But even at 25 cents/kWh, its still cheaper to overbuild wind by a factor of 3 and throw away the excess than to store. The problem is still one of cost.

    • MorinMoss Says:

      There must be practical ways to put surplus energy to use as opposed to simply throwing it away.
      And how much must the cost fall in order for it to start displacing the dirtiest / most costly of the peaker plants?

      • Peak power can cost more than 25cents per kilowatt hour now. That is one of the reasons solar can be considered cost effective is the need for less peak power.

        • Certain forms of demand-side management, such as ice-storage air conditioners, are economic even with differences in peak/off-peak rates much smaller than 25¢/kWh.  If these could be coordinated with the amount and availability of RE and other power on the grid, overall cost might be reduced.

          The problem is that there are a lot more ways to get it wrong than right, and so many of the people involved simply do not get this.

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