As Climate Extremes Grow, a More Resilient Grid Emerges

September 6, 2017


Hurricanes, floods, snow/ice storms, and other weather events are the leading cause of power outages in the United States.  That’s not going to get better.


If you think you can use the solar panels on your roof to power your home during an outage, think again. During an outage, while your home remains connected to the grid, the devices that manage your solar panels are powered down for safety reasons. In other words, this permanent connection to the grid makes it impossible for homeowners to draw on power generated by their own renewable energy resources.

A team of engineers at the University of California San Diego wants to change this. They have developed algorithms that would allow homes to use and share power from their renewable energy sources during outages by strategically disconnecting these devices, called solar inverters, from the grid. The algorithms work with existing technology and would improve systems’ reliability by 25 to 35 percent. Researchers detail the algorithms and their applications in a paper they presented at the American Control Conference in Seattle, Wash.

“We were inspired to start investigating a way to use renewable power during outages after Hurricane Sandy affected eight million people on the East Coast and left some without power for up to two weeks,” said Abdulelah H. Habib, a Ph.D. candidate in mechanical engineering at UC San Diego and the paper’s first author.

Just a few hours without power can cause massive losses to both product and revenue. Every year, 7 million customers experience power outages. Outages that last more than 5 to 10 minutes cost customers more than $80 billion each year.

How the algorithm works

The innovation here is the algorithm’s capability to prioritize distribution of power from renewable resources during an outage. The equations take into account forecasts for solar and wind power generation as well as how much energy storage is available, including electric vehicles, batteries and so on. The algorithm combines that information with the amount of energy that the residents are projected to use as well as the amount of energy that a cluster of homes can generate.

The algorithm could also be programmed to include a priority function, based on different parameters. For example, customers who are willing to pay more could get priority to get power during an outage. Or customers who generate more energy than they produce during normal operations would not lose power during an outage. More importantly, the algorithm could give priority to customers who are in urgent need of power, because they use life support equipment, for example.

Hardware and storage

Researchers investigated what energy storage configuration would work best with their algorithm. Although having energy storage systems in each home leads to optimal performance, most customers preferred to share a community-scale storage system, which dramatically cut down costs.

“Houses connected together are much more resilient during outages,” said Raymond de Callafon, a professor of mechanical engineering at the University of California San Diego, and one of the senior authors of the paper. “They’re also more resilient to price fluctuations. They can do a much better job at sharing resources and it benefits every house.”

The algorithms work with existing technology but they require each home to be equipped with circuit breakers that can be remotely controlled–and these devices are not yet widespread. Utilities also would have to install advanced communications methods that allow the power systems in a residential cluster to talk to one another.

Electric Light and Power:

Ameren Corp., a Midwest-based utility, and S&C Electric Co., conducted a successful 24-hour islanding test this month at the recently deployed Ameren microgrid in Champaign, Illinois.

The microgrid has been operational since May and can provide a seamless transition from grid-connected to island mode.

The test focused specifically on the 50kW microgrid at the site, which powers an Ameren research facility. The complete microgrid includes 225 kW of renewable generation (PV solar and wind) and 250kW / 500kWh of battery energy storage.

The test began at 8 a.m. on Aug. 3, 2017, with the battery’s state of charge at 97 percent capacity. Once the battery was depleted to 90 percent capacity, solar and wind generation kicked in, simultaneously carrying the load and charging the battery.

This pattern continued throughout the day, never letting the battery fall lower than 88 percent capacity. In short, the microgrid functioned without any human interaction, automatically coordinating resources and ensuring power never faltered.

Upon conclusion of the 24-hour test, the microgrid successfully moved back into grid-connected mode without any loss of power for end users.

“We have one of the few microgrids in the world that operates at utility-scale voltages and can seamlessly transition from grid-connected to islanded mode,” said Ron Pate, senior vice president, operations and technical services at Ameren Illinois. “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.”

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 exceeds the load, the excess powers the battery. With a rotating machine, the influx of generation would have caused the system to trip due to penetration limits.



7 Responses to “As Climate Extremes Grow, a More Resilient Grid Emerges”

  1. wpNSAlito Says:

    Solutions like this are all very doable, just a matter of designing, testing, and (often the biggest challenge) getting it to the market.

  2. J4Zonian Says:

    “customers who are willing to pay more could get priority to get power during an outage.” That’s one piss poor idea.

    So now we’re creating electric ghettos, concentration camps in which poor people–at least those with medical conditions–are sentenced to death so rich people aren’t inconvenienced by having their big screens stop working for a couple of hours. Because that’s exactly what will happen unless we stop it; as long as there are rich people and wealth and power are interchangeable commodities, they’ll exercise their power to separate themselves from the feedback loops their actions cause. Just one more step along the road we’ve been traveling for five centuries.

    Here’s another, in a different way: We need UREA, the Urban Renewable Electrification Agency, to coordinate and build micro grids and neighborhood co-ops, especially in poor neighborhoods. Get ready to whip the tablecloth of wealth out from under the rich. Or, if we don’t have the courage and strength to outlaw rich people outright, at least we need to drastically limit their predation while we slowly drain wealth from the…castle?

    • funslinger62 Says:

      I guess you missed this sentence: “More importantly, the algorithm could give priority to customers who are in urgent need of power, because they use life support equipment, for example.”

  3. Greg Wellman Says:

    Peter (or anyone!), can you explain the last paragraph of the EL&P pull quote? Does “rotating machine” mean “flywheel storage”? Does “penetration limit” in that context mean that flywheel storage can’t absorb an increase in generation fast enough to keep the system stable (whereas a battery can)?

    • Ron Voisin Says:

      It means that your Beany-and-Cecil propeller cap is not spinning fast enough.

      Try looking into the wind as you walk.

    • greenman3610 Says:

      does sound like a flywheel. that’s why batteries of some kind are taking over, look for another post on this tomorrow.

    • dumboldguy Says:

      No to both your questions (I’m pretty sure). I’m no electrical engineer, but I think “rotating machine” refers to (SG) spinning generators powered by thermal sources—coal, gas, oil, nuke.

      The “penetration limit” problem arises when the too much DG (Distributed Generation, i.e., from a microgrid source) enters the grid—-can cause a system trip. Renewable energy which enters through inverters is a special case, and at present, seems harder to integrate than that from SG.

      A lot of gobbledy gook here—-look at page 10 for something that is sort of understandable.

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