Iron-flow technology from ESS is being deployed at scale in the U.S.
The world’s electric grids are creaking under the pressure of volatile fossil-fuel prices and the imperative of weaning the world off polluting energy sources. A solution may be at hand, thanks to an innovative battery that’s a cheaper alternative to lithium-ion technology.
SB Energy Corp., a U.S. renewable-energy firm that’s an arm of Japan’s SoftBank Group Corp., is making a record purchase of the batteries manufactured by ESS Inc. The Oregon company says it has new technology that can store renewable energy for longer and help overcome some of the reliability problems that have caused blackouts in California and record-high energy prices in Europe.
The units, which rely on something called “iron-flow chemistry,” will be used in utility-scale solar projects dotted across the U.S., allowing those power plants to provide electricity for hours after the sun sets. SB Energy will buy enough batteries over the next five years to power 50,000 American homes for a day.
“Long-duration energy storage, like this iron-flow battery, are key to adding more renewables to the grid,” said Venkat Viswanathan, a battery expert and associate professor of mechanical engineering at Carnegie Mellon University.
ESS was founded in 2011 by Craig Evans, now president, and Julia Song, the chief technology officer. They recognized that while lithium-ion batteries will play a key role in electrification of transport, longer duration grid-scale energy storage needed a different battery. That’s because while the price of lithium-ion batteries has declined 90% over the last decade, their ingredients, which sometimes include expensive metals such as cobalt and nickel, limit how low the price can fall.
The deal for 2 gigawatt-hours of batteries is worth at least $300 million, according to ESS. Rich Hossfeld, chief executive officer of SB Energy, said the genius of the units lies in their simplicity.
Julia Song: Credit: Tojo Andrianarivo/Bloomberg
“The battery is made of iron salt and water,” said Hossfeld. “Unlike lithium-ion batteries, iron flow batteries are really cheap to manufacture.”
Every battery has four components: two electrodes between which charged particles shuffle as the battery is charged and discharged, electrolyte that allows the particles to flow smoothly and a separator that prevents the two electrodes from forming a short circuit.
Flow batteries, however, look nothing like the battery inside smartphones or electric cars. That’s because the electrolyte needs to be physically moved using pumps as the battery charges or discharges. That makes these batteries large, with ESS’s main product sold inside a shipping container.
What they take up in space, they can make up in cost. Lithium-ion batteries for grid-scale storage can cost as much as $350 per kilowatt-hour. But ESS says its battery could cost $200 per kWh or less by 2025.
Crucially, adding storage capacity to cover longer interruptions at a solar or wind plant may not require purchasing an entirely new battery. Flow batteries require only extra electrolyte, which in ESS’s case can cost as little as $20 per kilowatt hour.
“This is a big, big deal,” said Eric Toone, science lead at Breakthrough Energy Ventures, which has invested in ESS. “We’ve been talking about flow batteries forever and ever and now it’s actually happening.”
A worker at the ESS facility in Wilsonville, OR Credit: Tojo Andrianarivo/Bloomberg
The U.S. National Aeronautics and Space Administration built a flow battery as early as 1980. Because these batteries used water, they presented a much safer option for space applications than lithium-ion batteries developed around that time, which were infamous for catching on fire. Hossfeld says he’s been able to get permits for ESS batteries, even in wildfire-prone California, that wouldn’t have been given to lithium-ion versions.
Still, there was a problem with iron flow batteries. During charging, the battery can produce a small amount of hydrogen, which is a symptom of reactions that, left unchecked, shorten the battery’s life. ESS’s main innovation, said Song, was a way of keeping any hydrogen produced within the system and thus hugely extending its life.
“As soon as you close the loop on hydrogen, you suddenly turn a lab prototype into a commercially viable battery option,” said Viswanathan. ESS’s iron-flow battery can endure more than 20 years of daily use without losing much performance, said Hossfeld.
Plastic sheets are treated with plasma at the ESS manufacturing facility in Wilsonville, OR
Credit: Tojo Andrianarivo/Bloomberg
At the company’s factory near Portland, yellow robots cover plastic sheets with chemicals and glue them together to form the battery cores. Inside the shipping containers, vats full of electrolyte feed into each electrode through pumps — allowing the battery to do its job of absorbing renewable power when the sun shines and releasing it when it gets dark.
It’s a promising first step. ESS’s battery is a cheap solution that can currently provide about 12 hours of storage, but utilities will eventually need batteries that can last much longer as more renewables are added to the grid. Earlier this month, for example, the lack of storage contributed to a record spike in power prices across the U.K. when wind speeds remained low for weeks. Startups such as Form Energy Inc. are also using iron, an abundant and cheap material, to build newer forms of batteries that could beat ESS on price.
So far, ESS has commercially deployed 8 megawatt-hours of iron flow batteries. Last week, after a six-month evaluation, Spanish utility Enel Green Power SpA signed a single deal for ESS to build an equivalent amount. SB Energy’s Hossfeld, who also sits on ESS’s board, said the company would likely buy still more battery capacity from ESS in the next five years.
Even as its order books fill up, ESS faces a challenging road ahead. Bringing new batteries to market is notoriously difficult and the sector is littered with failed startups. Crucially, lithium-ion technology got a head start and customers are more familiar with its pros and cons. ESS will have to prove that its batteries can meet the rigorous demands of power plant operators.
The new order should help ESS as it looks to go public within weeks through a special-purpose acquisition company at a valuation of $1.07 billion. The listing will net the company $465 million, which it plans to use to scale up its operations.
Siemens Energy will operate the unique €170m facility in a remote part of French Guiana, which will provide 10MW of power during the day and 3MW at night.
A unique baseload renewables project that combines the world’s largest hydrogen power plant with a 16MW electrolyser, a 3MW fuel cell, 55MW of solar panels and 20MW/38MWh of batteries has begun construction in French Guiana.
The set-up will enable the Centrale Électrique de l’Ouest Guyanais (CEOG) project to provide 10MW of baseload renewable power from 8am-8pm and 3MW from 8pm-8am.
The variable power from the solar panels will be sent to the grid during the day, with the batteries smoothing the output and extending it into the evening as the sun goes down. Excess solar power during the day will be converted into green hydrogen using the electrolyser, with up to 88MWh of hydrogen stored, and its energy converted back into electricity using the fuel cell, primarily at night.
Why hydrogen-fired power plants ‘will play a major role in the energy transition’
Because French Guiana — situated in northern South America, but technically a region of both France and the EU — is close to the equator, it has around 12 hours of daylight throughout the year, ensuring that the solar output and therefore operation of the project will remain fairly constant all year round.
Siemens Energy will act as manufacturer and operator of the €170m ($197m) facility, which is owned by French infrastructure company Meridiam (60%), Martinique-based oil refiner Société Anonyme de la Raffinerie des Antilles (30%), and French hydrogen power developer HDF Energy (10%).
The project is in a remote part of northwestern French Guiana, and the electricity will be injected into the local grid under a 25-year capacity contract with French utility EDF.
“This project is not only currently the largest power plant project in the world to store intermittent renewable energy using hydrogen, it is highly innovative,” said Meridiam CEO Thierry Déau. “It will stimulate local economic activity and contribute to positive environment and social impacts.”
Ambroise Fayolle, vice-president of the European Investment Bank, which provided a €25m loan to the project, added: “This project, combining a photovoltaic plant with innovative storage technologies including hydrogen systems, illustrates very well how climate change issues may find efficient answers through innovative solutions of energy production and storage.
“For the European Union and its climate bank, it is very important to support the deployment of very advanced renewable energy technologies that can be adapted to the specific characteristics of each territory.”
Although construction started on 30 September, it is not due to be fully commissioned until 2024.
According to a recent World Bank report, the price of power from the project will be lower or at least the same as local diesel-fired electricity.
Scientists have identified a chemical pathway to an innovative insulating nanomaterial that could lead to large-scale industrial production for a variety of uses – including in spacesuits and military vehicles. The nanomaterial — thousands of times thinner than a human hair, stronger than steel, and noncombustible — could block radiation to astronauts and help shore up military vehicle armor, for example.
Collaborative researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have proposed a step-by-step chemical pathway to the precursors of this nanomaterial, known as boron nitride nanotubes (BNNT), which could lead to their large-scale production.
“Pioneering work”
The breakthrough brings together plasma physics and quantum chemistry and is part of the expansion of research at PPPL. “This is pioneering work that takes the Laboratory in new directions,” said PPPL physicist Igor Kaganovich, principal investigator of the BNNT project and co-author of the paper that details the results in the journal Nanotechnology.
Collaborators identified the key chemical pathway steps as the formation of molecular nitrogen and small clusters of boron, which can chemically react together as the temperature created by a plasma jet cools, said lead author Yuri Barsukov of the Peter the Great St. Petersburg Polytechnic University. He developed the chemical reaction pathways by performing quantum chemistry simulations with the assistance of Omesh Dwivedi, a PPPL intern from Drexel University, and Sierra Jubin, a graduate student in the Princeton Program in Plasma Physics.
The interdisciplinary team included Alexander Khrabry, a former PPPL researcher now at Lawrence Livermore National Laboratory who developed a thermodynamic code used in this research, and PPPL physicist Stephane Ethier who helped the students compile the software and set up the simulations.
The results solved the mystery of how molecular nitrogen, which has the second strongest chemical bond among diatomic, or double-atom molecules, can nonetheless break apart through reactions with boron to form various boron-nitride molecules, Kaganovich said. “We spent considerable amount of time thinking about how to get boron – nitride compounds from a mixture of boron and nitrogen,” he said. “What we found was that small clusters of boron, as opposed to much larger boron droplets, readily interact with nitrogen molecules. That’s why we needed a quantum chemist to go through the detailed quantum chemistry calculations with us.”
BNNTs have properties similar to carbon nanotubes, which are produced by the ton and found in everything from sporting goods and sportswear to dental implants and electrodes. But the greater difficulty of producing BNNTs has limited their applications and availability.
Chemical pathway
Demonstration of a chemical pathway to the formation of BNNT precursors could facilitate BNNT production. The process of BNNT synthesis begins when scientists use a 10,000-degree plasma jet to turn boron and nitrogen gas into plasma consisting of free electrons and atomic nuclei, or ions, embedded in a background gas. This shows how the process unfolds:
− The jet evaporates the boron while the molecular nitrogen largely stays intact; − The boron condenses into droplets as the plasma cools; − The droplets form small clusters as the temperature falls to a few thousand degrees; − The critical next step is the reaction of nitrogen with small clusters of boron molecules to form boron-nitrogen chains; − The chains grow longer by colliding with one another and fold into precursors of boron nitride nanotubes.
“During the high-temperature synthesis the density of small boron clusters is low,” Barsukov said. “This is the main impediment to large-scale production.”
The findings have opened a new chapter in BNNT nanomaterial synthesis. “After two years of work we have found the pathway,” Kaganovich said. “As boron condenses it forms big clusters that nitrogen doesn’t react with. But the process starts with small clusters that nitrogen reacts with and there is still a percentage of small clusters as the droplets grow larger,” he said.
“The beauty of this work,” he added, “is that since we had experts in plasma and fluid mechanics and quantum chemistry we could go through all these processes together in an interdisciplinary group. Now we need to compare possible BNNT output from our model with experiments. That will be the next stage of modeling.”
A silicon anode virtually intact after one cycle, with the silicon (green) clearly separate from a component of the solid electrolyte interphase (fluorine, in red). Credit: Chongmin Wang | Pacific Northwest National Laboratory
Silicon is a staple of the digital revolution, shunting loads of signals on a device that’s likely just inches from your eyes at this very moment.
Now, that same plentiful, cheap material is becoming a serious candidate for a big role in the burgeoning battery business. It’s especially attractive because it’s able to hold 10 times as much energy in an important part of a battery, the anode, than widely used graphite.
But not so fast. While silicon has a swell reputation among scientists, the material itself swells when it’s part of a battery. It swells so much that the anode flakes and cracks, causing the battery to lose its ability to hold a charge and ultimately to fail.
Now scientists have witnessed the process for the first time, an important step toward making silicon a viable choice that could improve the cost, performance and charging speed of batteries for electric vehicles as well as cell phones, laptops, smart watches and other gadgets.
“Many people have imagined what might be happening but no one had actually demonstrated it before,” said Chongmin Wang, a scientist at the Department of Energy’s Pacific Northwest National Laboratory. Wang is a corresponding author of the paper recently published in Nature Nanotechnology.
Of silicon anodes, peanut butter cups and packed airline passengers
Lithium ions are the energy currency in a lithium-ion battery, traveling back and forth between two electrodes through liquid called electrolyte. When lithium ions enter an anode made of silicon, they muscle their way into the orderly structure, pushing the silicon atoms askew, like a stout airline passenger squeezing into the middle seat on a packed flight. This “lithium squeeze” makes the anode swell to three or four times its original size.
When the lithium ions depart, things don’t return to normal. Empty spaces known as vacancies remain. Displaced silicon atoms fill in many, but not all, of the vacancies, like passengers quickly taking back the empty space when the middle passenger heads for the restroom. But the lithium ions return, pushing their way in again. The process repeats as the lithium ions scoot back and forth between the anode and cathode, and the empty spaces in the silicon anode merge to form voids or gaps. These gaps translate to battery failure.
Scientists have known about the process for years, but they hadn’t before witnessed precisely how it results in battery failure. Some have attributed the failure to the loss of silicon and lithium. Others have blamed the thickening of a key component known as the solid-electrolyte interphase or SEI. The SEI is a delicate structure at the edge of the anode that is an important gateway between the anode and the liquid electrolyte.
In its experiments, the team watched as the vacancies left by lithium ions in the silicon anode evolved into larger and larger gaps. Then they watched as the liquid electrolyte flowed into the gaps like tiny rivulets along a shoreline, infiltrating the silicon. This inflow allowed the SEI to develop in areas within the silicon where it shouldn’t be, a molecular invader in a part of the battery where it doesn’t belong.
That created dead zones, destroying the ability of the silicon to store lithium and ruining the anode.
Think of a peanut butter cup in pristine shape: The chocolate outside is distinct from the soft peanut butter inside. But if you hold it in your hand too long with too tight a grip, the outer shell softens and mixes with the soft chocolate inside. You’re left with a single disordered mass whose structure is changed irreversibly. You no longer have a true peanut butter cup. Likewise, after the electrolyte and the SEI infiltrate the silicon, scientists no longer have a workable anode.
A silicon anode after 100 cycles: The anode is barely recognizable as a silicon structure and is instead a mix of the silicon (green) and the fluorine (red) from the solid electrolyte interphase. Credit: Chongmin Wang | Pacific Northwest National Laboratory
The team witnessed this process begin immediately after just one battery cycle. After 36 cycles, the battery’s ability to hold a charge had fallen dramatically. After 100 cycles, the anode was ruined.
Exploring the promise of silicon anodes
Scientists are working on ways to protect the silicon from the electrolyte. Several groups, including scientists at PNNL, are developing coatings designed to act as gatekeepers, allowing lithium ions to go into and out of the anode while stopping other components of the electrolyte.
Scientists from several institutions pooled their expertise to do the work. Scientists at Los Alamos National Laboratory created the silicon nanowires used in the study. PNNL scientists worked together with counterparts at Thermo Fisher Scientific to modify a cryogenic transmission electron microscope to reduce the damage from the electrons used for imaging. And Penn State University scientists developed an algorithm to simulate the molecular action between the liquid and the silicon.
Altogether, the team used electrons to make ultra-high-resolution images of the process and then reconstructed the images in 3-D, similar to how physicians create a 3-D image of a patient’s limb or organ.
“This work offers a clear roadmap for developing silicon as the anode for a high-capacity battery,” said Wang.
More information: Chongmin Wang et al, Progressive growth of the solid–electrolyte interphase towards the Si anode interior causes capacity fading, Nature Nanotechnology (2021). DOI: 10.1038/s41565-021-00947-8
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