Princeton Plasma Physics Laboratory’s advanced design of the world’s largest and most powerful stellarator demonstrates the ability to moderate heat loss from the plasma that fuels fusion reactions.

A key hurdle facing fusion devices called stellarators, those twisty facilities that seek to harness on Earth the fusion reactions that power the sun and stars, has been their limited ability to maintain the heat and performance of the plasma that fuels those reactions.

W7X Stellarator Design Graphic. Image Credit: http://wiki.fusenet.eu . Click image for the largest view.

Now collaborative research by scientists at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) and the Max Planck Institute for Plasma Physics in Greifswald, Germany, have found that the Wendelstein 7-X (W7-X) facility in Greifswald, the largest and most advanced stellarator ever built, has demonstrated a key step in overcoming this problem.

The cutting-edge facility, built and housed at the Max Planck Institute for Plasma Physics with PPPL as the leading U.S. collaborator, is designed to improve the performance and stability of the plasma – the hot, charged state of matter composed of free electrons and atomic nuclei, or ions, that makes up 99 percent of the visible universe. Fusion reactions fuse ions to release massive amounts of energy – the process that scientists are seeking to create and control on Earth to produce safe, clean and virtually limitless power to generate electricity for all humankind.

Recent research on the W7-X aimed to determine whether design of the advanced facility could temper the leakage of heat and particles from the core of the plasma that has long slowed the advancement of stellarators.

PPPL physicist Novimir Pablant, lead author of a paper describing the results in Nuclear Fusion said, “That is one of the most important questions in the development of stellarator fusion devices.”

Pablant’s work validates an important aspect of the findings. The research, combined with the findings of an accepted paper by Max Planck physicist Sergey Bozhenkov and a paper under review by physicist Craig Beidler of the institute, demonstrates that the advanced design does in fact moderate the leakage.

Max Planck physicist Andreas Dinklage said, “Our results showed that we had a first glimpse of our targeted physics regimes much earlier than expected. I recall my excitement seeing Novi’s raw data in the control room right after the shot. I immediately realized it was one of the rare moments in a scientist’s life when the evidence you measure shows that you’re following the right path. But even now there’s still a long way to go.”

The leakage, called “transport,” is a common problem for stellarators and more widely used fusion devices called tokamaks that have traditionally better coped with the problem. Two conditions give rise to transport in these facilities, which confine the plasma in magnetic fields that the particles orbit.

These conditions are:

  • Turbulence. The unruly swirling and eddies of plasma can trigger transport;
  • Collisions and orbits. The particles that orbit magnetic field lines can often collide, knocking them out of their orbits and causing what physicists call “neoclassical transport.”

Designers of the W7-X stellarator sought to reduce neoclassical transport by carefully shaping the complex, three-dimensional magnetic coils that create the confining magnetic field. To test the effectiveness of the design, researchers investigated complementary aspects of it.

Pablant found that measurements of the behavior of plasma in previous W7-X experiments agreed well with the predictions of a code developed by Matt Landreman of the University of Maryland that parallels those the designers used to shape the twisting W7-X coils. Bozhenov took a detailed look at the experiments and Beidler traced control of the leakage to the advanced design of the stellarator.

“This research validates predictions for how well the optimized design of the W7-X reduces neoclassical transport,” Pablant said. By comparison, he added, “Un-optimized stellarators have done very poorly” in controlling the problem.

A further benefit of the optimized design is that it reveals where most of the transport in the W7-X stellarator now comes from. “This allows us to determine how much turbulent transport is going on in the core of the plasma,” Pablant said. “The research marks the first step in showing that high-performance stellarator designs such as W-7X are an attractive way to produce a clean and safe fusion reactor.”

This news is quite welcome for fusion enthusiasts. While both the stellarator and the tokamak designs have shown potential both have a very long way to go. Likened to holding water in your hands, these devices are much larger and the fuels are much smaller. They both look like immense engineering challenges with only a bit of macro practicality and essentially no micro elegance. Most all the small private efforts are making actual progress getting to net yield while these huge concepts are still trying to function steadily. But your humble writer isn’t giving up on them just yet. The mega billions of taxpayer wealth getting spent on these is more likely to drag things to a stop.

But moon shot outbound technological contributions seem to be missing, something that huge undertakings usually throw off in abundance. Its a “lots in little out” situation that drives skepticism. One wonders how long this can go on.

A Washington State University team has developed a less expensive water electrolysis system that works under alkaline conditions but still produces hydrogen at comparable rates to the currently used system that works under acidic conditions and requires precious metals. This advance brings down the cost of water splitting technology, offering a more viable way to store energy from solar and wind power in the form of hydrogen fuel.

Anion Exchange Membrane Electrolysis Graphic. Image Credit: Washington State University . Click image for the largest view.

Currently the most popular system used for water splitting, or water electrolysis, relies on precious metals as catalysts, but a collaborative research team, including scientists from Los Alamos National Laboratory and Washington State University, has developed a system that uses less expensive and more abundant materials.

The WSU team described the advance in a paper published in Nature Energy.

Yu Seung Kim, a research scientist at Los Alamos National Laboratory and corresponding author on the paper said, “The current water electrolysis system uses a very expensive catalyst. In our system, we use a nickel-iron based catalyst, which is much cheaper, but the performance is comparable.”

Most water splitting today is conducted using a piece of equipment called a proton exchange membrane water electrolyzer, which generates hydrogen at a high production rate. It’s expensive, and works under very acidic conditions, requiring precious metal catalysts such as platinum and iridium as well as corrosion-resistant metal plates made of titanium.

The research team worked to solve this problem by splitting water under alkaline, or basic, conditions with an anion exchange membrane electrolyzer. This type of electolyzer does not need a catalyst based on precious metals. In fact, a team led by Yuehe Lin, professor at WSU’s School of Mechanical and Materials Engineering, created a catalyst based on nickel and iron, elements that are less expensive and more abundant in the environment.

Lin’s team shared their development with Kim at Los Alamos, whose team in turn developed the electrode binder to use with the catalyst. The electrode binder is a hydroxide conducting polymer that binds catalysts and provides a high pH environment for fast electrochemical reactions.

The combination of the Los Alamos-developed electrode binder and WSU’s catalyst boosted the hydrogen production rate to nearly ten times the rate of previous anion exchange membrane electrolyzers, making it comparable with the more expensive proton exchange membrane electrolyzer.

According to the U.S. Department of Energy about 10 million metric tons of hydrogen are currently produced in the United States every year, mostly by using natural gas in a process called natural gas reforming. Hydrogen produced from a water splitting process that is powered by electricity from renewable energy holds many economic and environmental benefits, Lin noted.

“Water splitting is a clean technology, but you need electricity to do it,” said Lin, who is also a corresponding author on the paper. “Now we have a lot of renewable energy, wind and solar power, but it is intermittent. For example, at night we can’t use solar, but if during the day, we can use extra energy to convert it into something else, like hydrogen, that’s very promising.”

The global hydrogen generation market is expected reach $199.1 billion by 2023. Potential markets for hydrogen energy include everything from mass energy conversion and power grid management to fuel cells for cars. Lin estimates that there are approximately 600 wind farms in the United States ready for direct connections to water electrolysis systems.

In addition to Los Alamos and WSU, researchers at Pajarito Powder and Sandia National Laboratories also contributed to this work. This research was supported by the HydroGen Advanced Water Splitting Materials Consortium established under the U.S. Department of Energy and Washington state’s JCDREAM program.

Could this technology be the breakthrough for hydrogen fuel? Maybe, but we’ve seen these ideas come for years now and steam reforming remains the primary production system. Its sure to be smarter than buying multimillion dollar batteries for wind turbines on wind farms, but that future looks pretty limited as folks wake up to the immense waste of money lost by taxpayers and ratepayers in those projects and may disappear entirely if true low cost energy production comes from nuclear or fusion designs. As Barnam essentially said, over a century ago, you can’t fool everyone forever.

On the other hand, hydrogen is a great fuel for fuel cells and would be a good one even for combustion engines, if only the solution(s) for storing the smallest atom can be found. That is the materials challenge of the century.

The U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) scientists found that a change in chemical composition enabled a boost the longevity and efficiency of a perovskite solar cell.

 

Perovskite/silicon tandem solar cells are contenders for the next-generation photovoltaic technology, with the potential to deliver module efficiency gains at minimal cost. Researchers developed a new triple-halide perovskite alloy that enabled increased power conversion efficiency and photo stability. Image Credit: Dennis Schroeder, NREL. Click image for the largest view.

 

The new formula enabled the solar cell to resist a stability problem that has so far thwarted the commercialization of perovskites. The problem is known as light-induced phase-segregation, which occurs when the alloys that make up the solar cells break down under exposure to continuous light.

Caleb Boyd, lead author of a newly published paper in Science said, “Now that we have shown that we are immune to this short-term, reversible phase-segregation, the next step is to continue to develop stable contact layers and architectures to achieve long-term reliability goals, allowing modules to last in the field for 25 years or more.”

Boyd and co-author Jixian Xu are associated with University of Colorado-Boulder Professor Michael McGehee’s research group, which investigates perovskites at NREL. The paper published in Nature is titled “Triple-halide wide-bandgap perovskites with suppressed phase-segregation for efficient tandems.”

Additional NREL scientists who contributed to the paper are Axel Palmstrom, Daniel Witter, Bryon Larson, Ryan France, Jérémie Werner, Steven Harvey, Eli Wolf, Maikel van Hest, Joseph Berry, and Joseph Luther.

Perovskite solar cells are typically made using a combination of iodine and bromine, or bromine and chlorine, but the researchers improved upon the formula by including all three types of halides. The research proved the feasibility of alloying the three materials.

Adding chlorine to iodine and bromine created a triple-halide perovskite phase and suppressed the light-induced phase-segregation even at an illumination of 100 suns. What degradation occurred was slight, at less than 4% after 1,000 hours of operation at 60 degrees Celsius. At 85 degrees and after operating for 500 hours, the solar cell lost only about 3% of its initial efficiency.

Boyd said, “The next step is to further demonstrate accelerated stability testing to really prove what might happen in 10 or 20 years in the field.”

The new formula created a solar cell with an efficiency of 20.3%.

Silicon remains the dominant material used in solar cells, but the technology is approaching its theoretical maximum efficiency of 29.1%, with a record 26.7% established to date. But putting perovskites atop a silicon solar cell to create a multijunction solar cell could boost efficiency and bring down the cost of solar electricity. NREL scientists were able to create a tandem perovskite/silicon solar cell with an efficiency of 27%. By itself, the silicon solar cell had an efficiency of about 21%.

This research now brings perovskite technology very close to being useful and attractive to commercial engineering. Even more interesting is how further improvement might trigger a lot of innovation into the tandem perovskite/silicon multijunction solar cell concept. Someday solar cells could become competitive to combusting fossil fuels for generating power without huge subsidies.

Osaka University researchers have found that thermoelectric power generators lose a great deal of their possible output power because of thermal and electrical contact resistance. Improving this limitation will help society power interconnected technologies of the future.

This image shows the external appearance of the developed compact, ultra-lightweight flexible thermoelectric conversion device. Image Credit: Osaka University, Click image for the largest view.

Interconnected healthcare and many other future applications will require internet connectivity between billions of sensors. The devices that will enable these applications must be small, flexible, reliable, and environmentally sustainable. Researchers must develop new tools beyond batteries to power these devices, because continually replacing batteries is difficult and expensive.

In a study published in Advanced Materials Technologies, researchers from Osaka University have revealed how the thermoelectric effect, or converting temperature differences into electricity, can be optimally used to power small, flexible devices. Their study has shown why thermoelectric device performance to date has not yet reached its full potential.

Thermoelectric power generators have many advantages. For example, they are self-sustaining and self-powered, have no moving parts, and are stable and reliable. Solar power and vibrational power do not have all of these advantages. Aviation and many other industries use the thermoelectric effect. However, applications to thin, flexible displays are in their infancy.

To date many researchers have optimized device performance solely from the standpoint of the thermoelectric materials themselves.

Tohru Sugahara, corresponding author of the study explained the team’s effort, “Our approach is to also study the electrical contact, or the switch that turns the device on and off. The efficiency of any device critically depends on the contact resistance.”

In their study, the researchers used advanced engineering to make a bismuth telluride semiconductor on a 0.4-gram, 100-square-millimeter flexible, thin polymer film. This device weighs less than a paperclip, and is smaller than the size of an adult fingernail. The researchers obtained a maximum output power density of 185 milliwatts per square centimeter. “The output power meets standard specifications for portable and wearable sensors,” said Sugahara.

However, approximately 40% of the possible output power from the device was lost because of contact resistance. In the words of Sugahara: “Clearly, researchers should focus on improving the thermal and electrical contact resistance to improve power output even further.”

Japan’s Society 5.0 initiative is aimed at helping everyone live and work together and proposes that the entirety of society will become digitalized. Such a future requires efficient ways to interconnect our devices. Technological insights, such as those by Ekubaru, co-lead author, and Sugahara, are necessary to make this dream a reality.

This research is quite welcome and is really just a start on a whole system look at thermoelectric development. Now that the team has started and the losses are revealed some thermoelectric researchers may do well to re-examine their work to see how much better their work might actually be. More news good coming one hopes.

University of California – San Diego nanoengineers have developed a safety feature that prevents lithium metal batteries from rapidly overheating and catching fire in case of an internal short circuit. The clever tweak does not prevent battery failure, but rather provides advance warning of failure and makes it much safer.

The team made a clever tweak to the part of the battery called the separator, which serves as a barrier between the anode and cathode, so that it slows down the flow of energy (and thus heat) that builds up inside the battery when it short circuits.

UC San Diego nanoengineers developed a separator that could make lithium metal batteries fail safely so that they do not rapidly overheat, catch fire or explode. Image Credit: David Baillot/UC San Diego Jacobs School of Engineering. Click image for the largest view. Many more photos at the press release link above.

The researchers, led by UC San Diego nanoengineering professor Ping Liu and his Ph.D. student Matthew Gonzalez, detail their work in a paper published in Advanced Materials.

Gonzalez, who is the paper’s first author said, “We’re not trying to stop battery failure from happening. We’re making it much safer so that when it does fail, the battery doesn’t catastrophically catch on fire or explode.”

Lithium metal batteries fail because of the growth of needle-like structures called dendrites on the anode after repeated charging. Over time, dendrites grow long enough to pierce through the separator and create a bridge between the anode and cathode, causing an internal short circuit. When that happens, the flow of electrons between the two electrodes gets out of control, causing the battery to instantly overheat and stop working.

The separator that the UC San Diego team developed essentially softens this blow. One side is covered by a thin, partially conductive web of carbon nanotubes that intercepts any dendrites that form. When a dendrite punctures the separator and hits this web, electrons now have a pathway through which they can slowly drain out rather than rush straight towards the cathode all at once.

Gonzalez compared the new battery separator to a spillway at a dam.

“When a dam starts to fail, a spillway is opened up to let some of the water trickle out in a controlled fashion so that when the dam does break and spill out, there’s not a lot of water left to cause a flood,” he said. “That’s the idea with our separator. We are draining out the charge much, much slower and prevent a ‘flood’ of electrons to the cathode. When a dendrite gets intercepted by the separator’s conductive layer, the battery can begin to self-discharge so that when the battery does short, there’s not enough energy left to be dangerous.”

Other battery research efforts focus on building separators out of materials that are strong enough to block dendrites from breaking through. But a problem with this approach is that it just prolongs the inevitable, Gonzalez said. These separators still need to have pores that let ions flow through in order for the battery to work. As a consequence, when the dendrites eventually make it through, the short circuit will be even worse.

Rather than block dendrites, the UC San Diego team sought to mitigate their effects.

In tests, lithium metal batteries equipped with the new separator showed signs of gradual failure over 20 to 30 cycles. Meanwhile, batteries with a normal (and slightly thicker) separator experienced abrupt failure in a single cycle.

Gonzalez explained, “In a real use case scenario, you wouldn’t have any advance warning that the battery is going to fail. It could be fine one second, then catch on fire or short out completely the next. It’s unpredictable. But with our separator, you would get advance warning that the battery is getting a little bit worse, a little bit worse, a little bit worse, each time you charge it.”

While this study focused on lithium metal batteries, the researchers say the separator can also work in lithium ion and other battery chemistries. The team will be working on optimizing the separator for commercial use. A provisional patent has been filed by UC San Diego.

Simple, perhaps easily engineered into a battery and hopefully very low cost. And we’ll not likely ever know that this technology is included in a battery we buy . . .


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