Microgrid Islanding: S&C and Ameren Show it Works at Illinois Microgrid

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Ameren’s new Illinois microgrid demonstrated that it’s able to seamlessly disconnect from the grid and run on renewable energy during a 24-hour microgrid islanding test this month.

S&C Electric and Ameren conducted the test at a 1.475 MW microgrid in Champaign that the Midwest utility unveiled in May.

Microgrid islanding — the ability to disconnect from the grid — is a key benefit of microgrid technology. When a storm or other disruption causes a grid outage, the microgrid can separate itself from the disturbance and use its on-site generators to provide power. Power continues to flow to microgrid customers even though those around them are in the dark.

“This successful test provided tangible proof that the system can accomplish what it was designed to do. The microgrid isn’t theoretical and our tests don’t need to be lab simulations. We were able to prove that this technology works and can provide key benefits to our customers,” said Ron Pate, senior vice president, operations and technical services at Ameren Illinois.

He added that the microgrid is one of the few in the world that operates at utility-scale voltages and can seamlessly transition from grid-connected to island mode.

“The microgrid isn’t theoretical…this technology works”

No loss of power after microgrid islanding

Ameren’s test focused on a 50 kW microgrid that powers an Ameren research facility. The complete microgrid includes 225 kW of renewable generation (PV solar and wind) and 250 kW/500kWh of battery energy storage.

S&C Electric and Ameren began the microgrid islanding test at 8 a.m. on Aug. 3, 2017, with the battery’s state of charge at 97 percent capacity. When the battery fell to 90 percent capacity, the microgrid’s solar and wind generation kicked in. The renewable generators simultaneously powered the research facility and charged the battery, in a pattern followed throughout the day. The battery capacity never fell lower than 88 percent.

More details about the test are hereshowing the activity of the battery and renewable energy. After the test, the microgrid moved back into grid-connected mode without any loss of power to those it serves.

In short, the test showed that the microgrid can function without any human interaction, automatically coordinate resources and ensure power does not falter.

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100 percent renewable

During the test, the Ameren microgrid functioned on 100 percent renewable energy throughout the day. Many microgrids of this scale need to rely on rotating machines or generators, which prevent 100 percent penetration of renewable energy in these situations. At the Ameren microgrid, when the generation produced exceeds the facility’s need for power, the excess power charges the battery. With a rotating machine, the influx of generation would have caused the system to trip due to penetration limits.

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“When designing this microgrid, we were confident that the seamless transition and the ability to run solely on renewable generation would be two of the biggest features to this system,” said David Chiesa, senior director, Business Development, S&C. “Microgrids are becoming more commonplace on the grid, and this test continues to prove how impactful they can be for energy users.”

S&C Electric will present more details about the Ameren microgrid at Microgrid 2018 in Chicago May 7-9.

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About Elisa Wood

Elisa Wood is the chief editor of MicrogridKnowledge.com. She has been writing about energy for more than three decades for top industry publications. Her work also has been picked up by CNN, the New York Times, Reuters, the Wall Street Journal Online and the Washington Post.


  1. Well what’s needed is a system design that provides power on demand, reliably 24 hours a day, 7 days a week and 52 weeks a year. To achieve that without diesel back-up generators, I would recommend –

    store energy capacity = 1.5 days x peak demand power
    annual maximum wind (+ solar) power = 7 x peak demand power
    (assuming I only know the system’s peak demand power) –

    So for this Ameren micro-grid where I assume “a 50 kW microgrid that powers an Ameren research facility” means that the peak demand power is 50kW, I would therefore recommend
    (see Grid Watch Demand Focus Table http://scottish.scienceontheweb.net/Wind%20power%20storage%20back-up%20calculator.htm?peak=50&units=kW#grid )

    storage energy = 1.5 days x 50kW = 36 hours x 50kW = 1800 kWh
    (whereas all the Ameren system has is “500kWh” which is too little by a factor of 3.6

    annual maximum wind (+ solar) power = 7 x 50kW = 350 kW
    (whereas all the Ameren system has is “250kW” which is too little by a factor of 1.4

    By “too little” I mean too little for 24/7/52 operation, even though the Ameren system worked perfectly well in the test conditions of that particular 24 hours. Clearly wind and solar power have days of plenty and days of shortage. My recommendations tell you how to design a system that works even on the days of shortage – for those dark days of winter when there’s not much wind blowing either – that’s when your system design gets its ultimate test.

    However, my above recommendation assumes that the system’s average power demand is about 60% (30kW) of peak power – (50kW), with an average daily energy usage of 24 hours x 30kW = 720kWh and a higher maximum daily energy usage.

    If the average power used is significantly lower than 30kW and in particular if the maximum daily energy usage is significantly lower than 720kWh then it may well be that not so much storage or wind+solar generation is required.

    Supposing although a micro-grid had a peak demand power of 50kW its maximum daily energy usage never was as much as 720kWh but was a lot less.

    Let’s assume that the average power was, say, only about 10kW and their average daily usage only 24 hours x 10kW = 240kWh, but their maximum daily energy usage in any one day was a maximum of 482kWh.

    Then all that would be need would be (see Off-grid daily usage Focus Table http://scottish.scienceontheweb.net/Wind%20power%20storage%20back-up%20calculator.htm?usage=482&units=kW#off )

    energy storage – 1157 kWh and annual maximum wind (+solar) power = 225 kWh

    which is still a factor of 2.3 times more energy storage the Ameren microgrid has (500kWh) but is exactly the wind+solar power they have.

    So it all really depends on what the maximum daily energy usage of the system is. Peak power doesn’t completely specify a system’s generation and storage requirements because both peak power and maximum daily energy usage are important design considerations.

    Likewise, a 50kW micro-grid which always runs flat out at 50kW (peak demand power was also the average power) and therefore had a maximum daily energy usage of 24 x 50kW = 1200kWh would have a greater energy storage and generation requirement.
    (See Off-grid daily usage Focus Table http://scottish.scienceontheweb.net/Wind%20power%20storage%20back-up%20calculator.htm?usage=1200&units=kW#off )

    In this case more energy storage 2880 kWh and maximum wind+solar power 560 kW would be required.
    Whatever system you are designing for, to make it easy to design reliable 100% renewable energy systems, I have provided this system design tool.

    Wind, storage and back-up system designer

    Peak demand, wind and back-up power / energy usage and storage capacity calculator

    For the specification and design of renewable energy electricity generation systems which successfully smooth intermittent wind generation to serve customer demand, 24 hours a day, 7 days a week and 52 weeks a year.

    Adopting the recommendation derived from scientific computer modelling that the energy storage capacity be about 5 hours times the wind power capacity, the tables offer rows of previously successful modelled system configurations – row A, a configuration with no back-up power and rows B to G offering alternative ratios of wind power to back-up power. Columns consist of adjustable power and energy values in proportion to fixed multiplier factors.

    Replies, comments and questions about using the Wind, storage and back-up system designer at this link please. https://scottishscientist.wordpress.com/2017/07/14/wind-storage-and-back-up-system-designer

    Scottish Scientist
    Independent Scientific Adviser for Scotland

    * Wind, storage and back-up system designer
    * Double Tidal Lagoon Baseload Scheme
    * Off-Shore Electricity from Wind, Solar and Hydrogen Power
    * World’s biggest-ever pumped-storage hydro-scheme, for Scotland?
    * Modelling of wind and pumped-storage power
    * Scotland Electricity Generation – my plan for 2020
    * South America – GREAT for Renewable Energy


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