DOE_GRID_9952255236_cba900cdff_o.jpg
TVA_racoon_mountain.jpg
DOE_GRID_9568562809_ea386d7ee7_o.jpg
DOE_GRID_9452926290_5fc6140c12_o.jpg
DOE_GRID_9952255236_cba900cdff_o.jpg

energy R&D, on the move: grid-scale energy storage


SCROLL DOWN

energy R&D, on the move: grid-scale energy storage


Arun Majumdar on the Future of the US Electric Grid

For the past century, the United States’ electric sector has continuously expanded to keep up with the steadily growing demand for electricity. The interconnectedness of the various independent systems makes the national electric system vulnerable. The effects of an outage, either because of technical failure or terrorist attacks, would have widespread impact on the system. What we need now is a grid that is more distributed, flexible, and robust.

A key part of this is the distributed large-scale storage or on-demand dispatch of electricity through fuel cells, directly in batteries, or even more exotic technologies. Our inability to cheaply store the electrons we generate at massive scale has become a major bottleneck to the performance of our country’s energy system. While we have long had an efficient way to store limited amounts of electricity using pumped hydro storage whereby water is pumped uphill in massive open mountainous reservoirs, its potential for further expansion is severely limited by the availability of appropriate geography. Nonetheless, pumped hydroelectric storage represents 99 percent of world-wide storage capacity. Meanwhile, the Electric Power Research Institute estimates that all battery storage technologies combined today offer an installed capacity of less than one full-size coal power plant.

And that is why research into grid-scale storage has exploded in material science, chemical engineering, and chemistry departments across the United States over the past five years. The efforts now underway draw on the best researchers from across the world with an unprecedented focus. Moreover, early achievements here are increasingly promising and coming faster than expected. 

TVA_racoon_mountain.jpg

Grid Storage - Available Today


Electricity is the most perishable commodity. The moment it is generated, it needs to be consumed or stored.

— Vladimir Bulovic, MIT School of Engineering associate dean for innovation 

Grid Storage - Available Today


Electricity is the most perishable commodity. The moment it is generated, it needs to be consumed or stored.

— Vladimir Bulovic, MIT School of Engineering associate dean for innovation 

photos: DOE/flickr

Compressed air energy storage

Compressing air with extra energy on hand and then getting it back out when needed is not a new concept. The city of Paris used a “pneumatic dispatch of power” network in the late nineteenth century to drive small machines, water pumps, and refrigerators. More conventional utility-scale electricity storage applications followed: hundreds of megawatts of capacity in underground salt domes in Germany in the 1970s and saline caverns in the 1990s in Alabama. In the years since, however, the technology has largely sat on the shelf.

The rise of intermittent renewables such as wind and solar power has now changed that, with utilities around the country taking a second look at deploying this relatively “mature” technology. One major attraction is the cost, which is more comparable to pumped hydro storage than today’s chemical batteries. Another is scale, which is potentially one hundred times that of alternatives.

“Compressed air energy storage v2.0” R&D has looked to reduce costs and improve efficiency by changing how these systems handle heat. When air is compressed, it gets extremely hot; the so-called “diabatic” systems deployed in the past lost this energy. “Isothermal” storage, on the other hand, reduces that wasted heat by spraying a fine mist into the compressing air, capturing the heated water separately for later use during expansion. A startup founded on research conducted at Dartmouth College’s Thayer School of Engineering is attempting to commercialize just this—a 1.5-megawatt unit was recently demonstrated in New Hampshire.

Another recent R&D focus has been the development of smaller, megawatt-scaled systems either above ground or in man-made caverns. Smaller, modular systems have the flexibility to be placed where they are most useful on the grid. Building on research carried out in the 1980s by Stanford graduate student Steve Chomyszak focusing on efficient “toroidal intersecting vane compressors” (initially envisioned for use in automotive hydrogen fuel cells), startup firm General Compression has recently completed its first 2-megawatt, wind turbine-driven compressed air storage facility in Texas.

Direct methanol fuel cells for backup and off-grid power 

USC and Caltech

When you think of backup electricity for when the grid goes down, a noisy generator probably springs to mind. An increasingly available option, however, might be fuel cells. They are clean, quiet, and have few moving parts. But compared to a gasoline or diesel generator, they are not “corner hardware store” convenient: they can be large and heavy; they need gaseous fuels such as purified methane or even hydrogen, which is hard to transport and store; and they must operate hot and at high pressures. But a type of fuel cell developed by researchers over the past two and half decades at the University of Southern California’s Loker Hydrocarbon Research Institute in collaboration with Caltech’s Jet Propulsion Laboratory (JPL) changes that.

With funding from DARPA beginning in 1989, USC’s George Olah and Surya Prakash found that solutions of liquid methanol—an alcohol similar to ethanol fuel—could be oxidized across a catalyst to form CO2 and water, and an electron flow in the process. Compared to hydrogen fuel cells, this “direct methanol fuel cell technology” could run at low temperatures and atmospheric pressures across a wide range of sizes. Though the efficiency of the methanol’s conversion to electricity is relatively low, the high energy density inherent in the liquid fuel helps to compensate, making this technology particularly useful for long-lasting, low-power electricity delivery.

Years of additional research and refinement of ancillary systems alongside research teams at JPL and Caltech have resulted in a viable technology now used in a wide variety of applications: from portable consumer electronics to lightweight soldier-worn power supplies, and more recently off-grid or backup generator replace- ment for building-sized applications. Licensing their patent portfolio to manufacturers such as SFC Energy AG in 2011 has enabled the further development and commercial availability of this unique form of energy storage and delivery. 

 

Related: the US National Research Council on threats to the US electric grid →


 
I was part of the California Council of Science and Technology’s effort to see how we could get to 80% below 1990 emissions by 2050. We looked at everything; we looked at the context that the whole country was working on the same kind of problem; and we looked at biofuels and carbon capture and storage and nuclear energy and all the rest of it, and we came to the conclusion that you can’t do it with renewables alone without a nonexisting technology. That nonexistent technology is what we called zero emission load: grid-scale energy storage with no emission. If you’ll invent grid-scale energy storage with no emission, we saw how you could get there.
— Burton Richter, Stanford University Paul Pigott professor emeritus in the physical sciences and SLAC National Accelerator Laboratory director emeritus
 
DOE_GRID_9568562809_ea386d7ee7_o.jpg

Grid Storage - Near at Hand


We often think that there are logical connections between science, development, and manufacturing, in that expected order. But actually in the area of storage, there have been a number of surprises. They didn’t happen because people had ideas and they worked on them and it all went in the normal sequence, but actually some of these surprises came as a result of an unexpected outside influence and some came from mistakes.

— Robert Huggins, Stanford professor emeritus of materials science and engineering 

Grid Storage - Near at Hand


We often think that there are logical connections between science, development, and manufacturing, in that expected order. But actually in the area of storage, there have been a number of surprises. They didn’t happen because people had ideas and they worked on them and it all went in the normal sequence, but actually some of these surprises came as a result of an unexpected outside influence and some came from mistakes.

— Robert Huggins, Stanford professor emeritus of materials science and engineering 

Fuel cell superlattice materials 

MIT

Fuel cells make electricity by combining hydrogen, or hydrocarbon fuels, with oxygen. Now, MIT researchers have unraveled the properties of a promising alternative material structure for a key component of these devices.

The new structure, a “superlattice” of two compounds interleaved at a tiny scale, could serve as one of the two electrodes in the fuel cell. The complex material, discovered about six years ago and known as LSC113/214, is composed of two oxides of the elements lanthanum, strontium, and cobalt. While one of the oxides was already known as an especially good material for such electrodes, the combination of the two is far more potent in promoting oxygen reduction than either oxide alone. Oxygen reduction is one of two main reactions in a fuel cell, and the one that has limited their overall performance—so finding improved materials for that reaction could be a key advance for fuel cells.

The key to the material’s performance, explains MIT’s Bilge Yildiz, associate professor of nuclear science and engineering, is the marriage of complementary qualities from its two constituents. One of the oxides allows superior conduction and transfer of electrons, while the other excels at holding onto oxygen atoms; to perform well as a fuel cell’s cathode—one of its two electrodes—a material needs to have both qualities. The close proximity of the two materials in this superlattice causes them to “borrow” one another’s attributes, the MIT team found. The result is a mate- rial with reactivity that exceeds that of the best materials currently used in fuel cells; as Yildiz says, “It’s the best of the two worlds.”

Credit: David Chandler, ©Massachusetts Institute of Technology, used with permission, 2013

Replacing platinum with graphene in fuel cells 

Stanford

The high price of platinum catalysts used inside fuel cells has provided a roadblock to widespread use. Now, chemistry professor Hongjie Dai’s nanoscale research at Stanford University has found a way to reduce the cost.

Over the past five years, the price of platinum has ranged from just below $800 to more than $2,200 an ounce. Among the most promising low-cost alternatives to platinum is the carbon nanotube—a rolled-up sheet of pure carbon, called graphene, that is one atom thick and more than 10,000 times narrower than a human hair. Carbon nanotubes and graphene are excellent conductors of electricity and relatively inexpensive to produce. For the study, the Stanford team used multiwalled carbon nanotubes consisting of two or three concentric tubes nested together. The scientists showed that shredding the outer wall, while leaving the inner walls intact, enhances catalytic activity in nanotubes, yet does not interfere with their ability to conduct electricity.

“A typical carbon nanotube has few defects,” said Stanford post- doctoral fellow Yanguang Li. “But defects are actually important to promote the formation of catalytic sites and to render the nanotube very active for catalytic reactions.” For the study, Li and his colleagues treated multiwalled nanotubes in a chemical solution. Microscopic analysis revealed that the treatment caused the outer nanotube to partially unzip and form nanosized graphene pieces that clung to the inner nanotube, which remained mostly intact.

“We found that the catalytic activity of the nanotubes is very close to platinum,” says Li. “This high activity and the stability of the design make them promising candidates for fuel cells.”

Credit: Mark Shwartz for the Stanford Precourt Institute for Energy, 2012 

Associate Professor Bilge Yildiz, MIT

Associate Professor Bilge Yildiz, MIT

Professor Hongjie Dai, Stanford

Professor Hongjie Dai, Stanford

DOE_GRID_9452926290_5fc6140c12_o.jpg

Grid Storage - On the Horizon


In general, when we think about storage, the game changers will come from three buckets. One is new materials—new chemistry that will store more energy, at less cost, and will be easier to produce. The second is the architecture of the storage device. That starts a round of innovation that was not there previously. And then the third is the issue of manufacturability and scale.

— Yet-Ming Chiang, MIT professor of materials science and engineering 

Grid Storage - On the Horizon


In general, when we think about storage, the game changers will come from three buckets. One is new materials—new chemistry that will store more energy, at less cost, and will be easier to produce. The second is the architecture of the storage device. That starts a round of innovation that was not there previously. And then the third is the issue of manufacturability and scale.

— Yet-Ming Chiang, MIT professor of materials science and engineering 

Liquid-metal grid storage batteries 

MIT

A new system developed at MIT to lower the costs and increase longevity of large-scale energy storage uses high-temperature bat- teries with liquid components that, like some novelty cocktails, naturally settle into distinct layers because of their different densities.

The three molten materials form the positive and negative poles of the battery, as well as a layer of electrolyte—a material that charged particles cross through as the battery is being charged or discharged—in between. All three layers are composed of materials that are abundant and inexpensive, explains MIT’s Donald Sadoway, professor of materials science and engineering. One promising recipe: magnesium for the negative electrode (top layer), a salt mixture containing magnesium chloride for the electrolyte (middle layer,) and antimony for the positive electrode (bottom layer). The system would operate at a temperature of 700 degrees Celsius.

In this formulation, Sadoway explains, the battery delivers current as magnesium atoms lose two electrons, becoming magnesium ions that migrate through the electrolyte to the other electrode. There, they reacquire two electrons and revert to ordinary magnesium atoms, which form an alloy with the antimony. To recharge, the battery is connected to a source of electricity, which drives magnesium out of the alloy and across the electrolyte, where it then rejoins the negative electrode.

The inspiration for the concept came from Sadoway’s earlier work on the electrochemistry of aluminum smelting, which is conducted in electrochemical cells that operate at similarly high temperatures. Many decades of operation have proved that such systems can operate reliably over long periods of time at an industrial scale, producing metal at low cost. In effect, he says, what he figured out was “a way to run the smelter in reverse.”

Credit: David Chandler, ©Massachusetts Institute of Technology, used with permission, 2012 

Long-life crystalline copper hexacyanoferrate battery electrodes 

Stanford

Stanford researchers have developed part of new long-life grid-scale battery: a new electrode that employs crystalline nanoparticles of a copper compound. In laboratory tests, the electrode survived 40,000 cycles of charging and discharging. “At a rate of several cycles per day, this electrode would have a good thirty years of useful life on the electrical grid,” says graduate student Colin Wessells.

The electrode’s durability derives from the atomic structure of the crystalline copper hexacyanoferrate used to make it. The crystals have an open framework that allows ions—electrically charged particles with movements that en masse either charge or discharge a battery—to easily go in and out without damaging the electrode. Most batteries fail because of accumulated damage to an electrode’s crystal structure.

Because the ions can move so freely, the electrode’s cycle of charging and discharging is extremely fast, which is important because the power you get out of a battery is proportional to how fast you can discharge the electrode. To maximize the benefit of the open structure, the researchers needed to use the right-sized ions. Too big and the ions would tend to get stuck and could damage the crystal structure when they moved in and out of the electrode. Too small and they might end up sticking to one side of the open spaces between atoms, instead of easily passing through. The right-sized ion turned out to be hydrated potassium, a much better fit compared to other hydrated ions such as sodium and lithium.

“It fits perfectly—really, really nicely,” said Stanford’s Yi Cui. “Potassium will just zoom in and zoom out, so you can have an extremely high-powered battery.”

Credit: Louis Bergeron for the Stanford News Service, 2011

A simplified lithium polysulfide membrane-free flow battery

Stanford

Researchers from DOE’s SLAC National Accelerator Laboratory and Stanford University have developed a new flow battery with a simplified, less-expensive design that presents a potentially viable solution for large-scale production.

Today’s flow batteries pump two different liquids through an interaction chamber where dissolved molecules undergo chemical reactions that store or give up energy. The chamber contains a membrane that only allows ions not involved in reactions to pass between the liquids while keeping the active ions physically separated. This battery design has two major drawbacks: the high cost of liquids containing rare materials such as vanadium—especially in the huge quantities needed for grid storage—and the mem- brane, which is also expensive and requires frequent maintenance.

The new Stanford/SLAC battery design uses only one stream of molecules and does not need a membrane at all. Its molecules mostly consist of the relatively inexpensive elements lithium and sulfur, which interact with a piece of lithium metal coated with a barrier that permits electrons to pass without degrading the metal. When discharging, the molecules, called lithium polysulfides, absorb lithium ions; when charging, they lose them back into the liquid. The entire molecular stream is dissolved in an organic solvent, which does not have the corrosion issues of water-based flow batteries.

“In initial lab tests, the new battery also retained excellent energy-storage performance through more than 2,000 charges and discharges, equivalent to more than 5.5 years of daily cycles,” says research group leader Yi Cui.

Credit: Andy Freeberg for the SLAC National Accelerator Laboratory, 2013 

Professor Donald Sadoway, MIT

Professor Donald Sadoway, MIT

Graduate student Colin Wessells, Stanford + Alveo Energy

Graduate student Colin Wessells, Stanford + Alveo Energy

Associate Professor Yi Cui, Stanford + SLAC

Associate Professor Yi Cui, Stanford + SLAC

Related: US DOE's Joint Center For Energy Storage Research battery innovation hub →

Hear an introduction to grid-scale battery chemistry from professor Donald Sadoway at a 2011 MIT World lecture

 

 
When I first arrived at MIT, I started talking to people about what our opportunities and responsibilities were for the next decade. Much to my astonishment—having been in academic institutions my entire life, I was expecting to get about 5,000 views from 1,000 faculty—there was almost complete unanimity that the most important thing for MIT to do was to make a significant difference in changing the world’s energy system.
— Susan Hockfield, MIT president emerita