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Animated gif visualizing a distorted map of the United States, switching between transmission lines susceptible to cascading failures highlighted in orange and transmission lines that were not, in green.

What Causes Cascading Power Grid Failures

Just a few vulnerable patches in North American power grids are responsible for most of the continent’s largest blackouts, a new study finds. These insights could lead to ways to make power grids more robust, researchers say.

Power failures sometimes only have mild and fairly local effects, but other times similar initial failures cascade to cause major failures across power grids. Understanding the causes of these cascades is challenging because the conditions of power grids can vary greatly by peak usage times, level of power demand, seasons and other factors.

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An illustration shows the Zunum Aero 12-seater hybrid jet flying through clouds.

This Hybrid Electric Jet is Preparing for Takeoff in 2022

The aviation industry has made steady progress in cutting its fuel use and carbon emissions. Planes have become lighter, engines more efficient, and airlines are starting to use biofuel blends and to better manage their traffic flow in order to save money and reduce emissions.

Still, aviation produces about 2 percent of the world’s carbon emissions. To reduce them further, Zunum Aero has a bold plan for a low-carbon flying future. The Kirkland, Wash.-based startup plans to deliver its first hybrid electric plane in 2022.

The company, which came out of stealth in 2017 and has backing from Boeing and JetBlue’s venture capital arms, unveiled details of its aircraft in October. The 12-seater jet will have a range of 700 miles and maximum cruise speed of 340 miles per hour. It will generate 80 percent fewer emissions and produce 75 percent less noise.

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man on bmx bike on a dirt road by a border wall

Mexico Border Wall Won’t Stop Cross-border Power Push

Relations between the United States and Mexico are strained at the national level, with President Donald Trump pushing his promised border control wall and demanding a U.S.-favored rewrite of the North American Free Trade Agreement (NAFTA). But Mexico and the southwestern states have continued working towards an international agenda for electricity, and regional players are talking up a first set of projects due to be completed before Trump’s term is up — projects that put the region on a path to a far more electrically-porous border.

These projects include a trio of new crossborder links between California, Arizona and Mexico to be completed in the next three years. They also include grid studies, revised market rules, and new power lines within Mexico that could rapidly expand flows over all of the U.S.-Mexico interties. "The proposition right now is fairly small because the interconnections are small. But that’s going to change,” says Carl Zichella, director for Western transmission at the Natural Resources Defense Council.

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In his laboratory at the Illinois Institute of Technology, Qing-Chang Zhong points to a computer diagram of his SYNDEM concept.

Smart Power Electronic Converters May Help Stabilize the Grid

When Qing-Chang Zhong, IEEE Fellow and a professor of energy and power engineering at the Illinois Institute of Technology, thinks of the words “democracy” and "harmony,” he envisions the future of the electric power grid.

To Zhong, the concept of who or what may generate electric power is in flux. The 20th century model of a monopoly utility that owns a uni-directional connection to a customer is vanishing. In its place is the 21st century paradigm that millions of users and their devices can consume or generate electricity as needed, democratizing the power grid.

Further, in Zhong’s view, these devices either can wreak havoc through asynchronous and random interactions with the grid and one another, or can work together to support a more robust and secure power system.

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A photo shows an “air-breathing” battery made of clear glass tubins with red caps and an orange liquid in one half.

New Sulfur Flow Battery for Affordable Long-Term Grid Storage

The high cost of batteries still prevents them from being used to store renewable energy for times when the wind dies down or there’s no sun. Pumped hydroelectric storage is the cheapest known energy-storage technology today, but is limited by geography.

With a new battery, researchers at MIT say they have found the sweet spot for energy storage. The energy-dense battery could be the first to compete with the installed cost of pumped hydro and compressed-air storage, which cost around $100 per kilowatt-hour of energy stored. Scaled-up versions of the new battery could store electricity for a fifth of that, at $20/kWh. By comparison, Tesla claims its Gigafactory can produce batteries for around $125/kWh. 

The new battery might even have what it takes to replace fossil fuel “peaker” plants that can quickly inject power into the grid at high demand times. To compete with peaker plants, we need immense batteries that store energy from wind and solar for multiple days, even months, at an installed cost of around $50/kWh.

The device, reported in the journal Joule, is a type of flow battery, in which both the anode and cathode are liquid electrolytes. The anode in this case is sulfur dissolved in water, while the cathode is an aerated liquid salt solution that takes up and releases oxygen.

Lithium ions move between the electrolytes, and the salt solution at the cathode takes up or releases oxygen to balance the charge. During discharge, it takes up oxygen and the anode ejects electrons into an external circuit. When the oxygen is released, electrons go back to the anode, recharging the battery.

MIT materials scientist and engineer Yet-Ming Chiang says that his team’s main goal in building it was to keep costs to a minimum. They chose a water-based flow battery concept, which would have lower energy than a traditional battery but would be much cheaper per kWh.

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Hurricane Maria scrambled Puerto Rico's Humacao solar power plant

Why Solar Microgrids May Fall Short in Replacing the Caribbean's Devastated Power Systems

After the destruction inflicted across the Caribbean by hurricanes Harvey, Irma, and Maria, renewable energy advocates are calling for a rethink of the region's devastated power systems. Rather than simply rebuilding grids that delivered mostly diesel generation via damage-prone overhead power lines, renewables advocates argue that the island grids should leapfrog into the future by interconnecting hundreds or thousands of self-sufficient solar microgrids.

“Puerto Rico will lead the way for the new generation of clean energy infrastructure. The world will follow,” asserted John Berger, CEO for Houston-based solar developer Sunnova Energy in a tweet before meeting in San Juan with Puerto Rico Governor Ricardo Rosselló this week. Rosselló appears to be on board, inviting Elon Musk via tweet to use Puerto Rico as a “flagship project” to "show the world the power and scalability” of Tesla’s technologies, which include photovoltaic (PV) rooftops and Powerwall battery systems.

Some power system experts, however, say the solar-plus-batteries vision may be oversold. They say that the pressing need to restore power, plus equipment costs and other practical considerations, call for sustained reliance on centralized grids and fossil fuels in the Caribbean. “They need to recover from the storm. Unfortunately I think the quickest way to do that is to go back to how things were before,” says Brad Rockwell, power supply manager for the Kauaʻi Island Utility Cooperative that operates one of the most renewable-heavy grids in the U.S.

Now is a tough time for a debate, given the ongoing power and communications blackouts afflicting many Caribbean islands, including Puerto Rico, the U.S. and British Virgin Islands, Dominica, and St. Martin. As of Thursday 12 October—more than three weeks after Maria’s cyclonic wrecking ball crossed the region—over four-fifths of customers in Puerto Rico and the U.S. Virgin Islands remained without power, according to U.S. Department of Energy status reports.

Puerto Rico lost major transmission lines that dispatched electricity generated at oil, coal, and natural gas-fired power plants on its lightly populated South shore to all corners of the territory. Its outage level actually slipped from 88.3 to 89.4 percent earlier this week after a tie line went down near San Juan. But it bounced back slightly, to an estimated 83 percent outage level, by yesterday.

What is clear is that several firms are trying to move fast while they talk, equipping rooftop solar systems with battery storage that enables consumers to operate independently of stricken grids. For example:

  • German storage system manufacturer sonnen launched a PV-plus-battery collaboration with local Aguadilla-based solar developer Pura Energía early this month;
  • Sunnova is crafting storage options for roughly 10,000 customers in Puerto Rico that it has already equipped with PV systems;
  • Tesla says it is sending “hundreds” of its Powerwall battery systems to Puerto Rico and, after reports of price gouging by independent installers, plans to dispatch installers from the mainland to expand its local teams.

Peter Asmus, a microgrids analyst with Navigant Research, says that such solar microgrids will deliver power to solar system owners far faster than grid restoration, which is still months away for many customers. He says microgrids will also make the island systems more resilient in the long run.

Asmus sees the situation as reminiscent of post-war Europe, when devastated European grids left a vacuum that enabled something better. “They built a more advanced grid than we have in the U.S.,” says Asmus. He says the Caribbean has a similar opportunity today: “The infrastructure was devastated so severely. They can start over with a cleaner slate.”

Some suppliers see microgrids actually supplanting some of the region’s largest transmission lines. “The grid in Puerto Rico will never be built back the way it used to be,” wrote John Merritt, applications engineering director for Austin, Texas-based Ideal Power in an email to IEEE Spectrum. Ideal Power's multi-port power converters enable microgrids to efficiently swap power between their alternating current and direct current components, including PV systems, generators, and storage batteries.

Giving up big transmission lines sounds optimistic to Rockwell at the Kauaʻi Island Utility Cooperative (KIUC). It would, he says, represent a major system overhaul and thus lost time that Puerto Rico’s residents and economy can ill afford. “The people of Puerto Rico are not going to want to withstand any more delays than they have to while people figure out how to rebuild in a different way,” he says.

Rockwell adds that batteries are still a rather costly way to balance variable renewable generation. He speaks from experience. KIUC’s grid is over four-fifths solar-powered during some midday hours. Several utility-scale storage systems help integrate such a high degree of  variable power by quickly covering for lost PV generation when clouds pass overhead or by absorbing surplus midday generation and discharging it after the sun sets. But Rockwell says high battery costs mean KIUC still relies heavily on its diesel power plants.

Merritt at Ideal Power acknowledges that the same is true for microgrids. Integrating solar can cut an island microgrid’s fuel consumption by 60 to 70 percent, slashing operating costs and pollution, but he says diesel generators remain “important" assets. “Moving a site from 24/7 diesel-powered microgrid to a 24/7 solar + storage microgrid would be cost prohibitive in most cases,” says Merritt.

There are also questions about PVs’ hardiness. Harvey, Irma, and Maria left many PV systems in shambles. Merritt says that a microgrid for a commercial facility on Saint Croix that Ideal Power participated in assembling before the storms is operating without its six 33-kilowatt solar arrays. While they are out of commission for the next few months, the microgrid is relying solely on its diesel generators, battery, and converters.

Some utility-scale solar plants also took a beating, especially Puerto Rico’s solar array at Humacao. PV panels shattered and flew out of their frames when Maria’s Category-4 winds ripped over the Humacao solar plant, where its French owner Reden Energie was in the process of doubling capacity from 26 to 52 megawatts.

Houston-based microgrid developer Enchanted Rock advocates rugged microgrids supported by natural gas, which is cheaper and cleaner than diesel and may be more reliable than both diesel and solar during heavy weather. "You can build community-type microgrids that have some combination of natural gas generation, solar and storage,” says Enchanted Rock CEO Thomas McAndrew.

Enchanted Rock made a name for itself during Hurricane Harvey when its natural gas-powered microgrids at Houston-area grocery stores and a truck stop turned into hubs for first responders and weary residents. Diesel deliveries were hard to come by for 4-5 days, says McAndrew, but natural gas kept flowing underground throughout the storm.

At present few Caribbean islands have access to natural gas, and even Puerto Rico’s gas infrastructure is limited to one liquefied natural gas (LNG) import terminal that pipes the fuel to two power plants. Before Irma and Maria struck Rosselló had been working to expand LNG imports so more of its oil-fired power plants could burn gas.

Enchanted Rock’s McAndrew favors a network to distribute the gas more widely, which he says would be much cheaper than putting power lines underground to protect them from weather. He acknowledges that his proposal is ambitious, but says the outside investors that Puerto Rico will need to attract to support its revival can insist on infrastructure that will survive future storms. As McAndrew puts it: “Whether it’s private or government money, there’s got to be some sense that we might want to do this differently so we don’t just end up rebuilding it every couple of years.”

Researchers on two continents hoped to learn if multiple systems could work together to stabilize a storm-damaged grid

Stress-Testing a Hypothetical Global Grid

After this year’s series of hurricanes, an electric grid–focused experiment carried out in late September by research laboratories in the United States and Europe may prove especially timely.

It’s no stretch to imagine a hurricane cutting electric power across a wide swath of the United States, upsetting grid stability. The researchers wondered: Would be possible to stabilize the grid in such a situation using a high voltage direct current (HVDC) line reaching between the U.S. and, say, Europe, allowing grid operators to tap into excess generating capacity?

More to the point of the late September test, the researchers wanted to learn whether multiple systems on different continents could work simultaneously to balance the grid after a simulated disruption?

The answer is yes, but with a few qualifications.

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A photo shows several of Statoil's floating wind turbines surrounded by ships at dusk.

Floating Wind Turbines on the High Seas Could Produce Massive Amounts of Power

The world’s first offshore wind farm employing floating turbines is taking shape 25 kilometers off the Scottish coast and expected to begin operating by the end of this year. New research by atmospheric scientists at the Carnegie Institution for Science in Stanford, Calif. suggests that the ultimate destination for such floating wind farms could be hundreds of kilometers out in the open ocean. The simulations, published today in the Proceedings of the National Academy of Sciences, show that winds over the open ocean have far greater staying power than those over land.

Wind power generation is obviously contingent on how fast and how often winds blow. But only over the past decade have scientists and wind farm developers recognized that the winds measured prior to erecting turbines may not endure. For one thing, dense arrays of wind turbines act as a drag on the wind, depleting local or even regional wind resources. 

It is now generally accepted that drag from wind turbines in the boundary layer (where the atmosphere interacts with Earth's surface) limits the kinetic energy that large land-based wind farms can extract to about 1.5 megawatts per square kilometer (MW/km2). "If your average turbine extracts 2-6 MW, you really need to space those turbines 2-3 kilometers apart because the atmosphere just doesn’t give you more kinetic energy to extract,” says Carnegie postdoctoral researcher Anna Possner.

What Possner and climate scientist Ken Caldeira reveal today is that the atmosphere is more generous out in the open ocean. There, they estimate, wind farms could be packed more tightly, because energy should flow down from above the boundary layer to quickly restore winds depleted by wind turbine rotors. In some regions, such as the North Atlantic, the simulations suggest that large wind farms can extract 6 MW/km2 or more.

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Jayant Baliga, a bald, bearded man with greying hair, sits in a laboratory in front of instruments and a microscope.

Jayant Baliga's Quest to Make Silicon-Carbide Power Electronics Succeed

When Jayant Baliga invented the insulated gate bipolar transistor in the 1970s—something for which he won the 2014 IEEE Medal of Honor—it went from prototype to commercial product in about a year and a half. His quest to make silicon carbide a key material for power electronics has taken decades longer. But thanks to some recent innovations, he’s almost there. Two are new devices, impossible to make in silicon, and the third is a foundry process that will finally make SiC devices cost-competitive with silicon.

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A rescue crew surveys damage as they drive a large truck through several feet of water in a residential area.

Logistics Complicate Puerto Rico's Electric Grid Recovery

Like a careless driver in a fast car, Hurricane Irma plowed through the Leeward Islands in early September. It sideswiped Puerto Rico, knocking out electric power to 1 million people. It ran over Caribbean resort islands including Saint Kitts and Saint Martin, then skidded north at Key West. Careening up the Florida peninsula, Irma left millions of people without power.

A multi-billion-dollar smart grid investment and an unprecedented repair effort helped Florida Power & Light—the state’s largest utility—restore most service to 4.4 million customers by 22 September.

In a statement, the utility credited what it said was one of the largest restoration workforces assembled in U.S. history. Some 28,000 workers from 30 states and Canada had the power back on within 10 days.

Then, almost improbably, a second storm plowed through the Leeward Islands two weeks after Irma. This time, Puerto Rico was hit head-on by Hurricane Maria. Essentially 100 percent of its power was knocked out.

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