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New Flow Battery Ups Storage Capacity by Factor of Ten

To smooth out the peaks and valleys inherent in generating electric power from the sun and the wind, utility companies want massive battery farms capable of storing the surplus energy from renewable power sources for use when the sun goes down and the wind isn’t blowing. One candidate for this application is a redox flow battery that uses liquids to store and release energy.

Redox flow batteries possess a number of features that make them attractive for large-scale energy storage for power girds. For instance, their cost per kilowatt-hour is lower than the lithium-ion batteries often used in mobile devices, and their overall energy capacity can easily be expanded by adding more fluid to match a grid's growing needs.

Heretofore, they’ve been limited by low energy density—that is, energy stored per unit volume. To offer the storage needed by a local or regional power grid, they would need a lot of space, which is often limited in the cities they are intended to power. For example, the energy density of the vanadium redox-flow battery, the most developed type of redox flow battery, is roughly one-tenth that of lithium-ion batteries.

But in a paper published in the 27 November online edition of the journal Science Advancesscientists in Singapore reported that they have developed new redox flow lithium batteries whose energy densities match those of their lithium-ion counterparts. “The energy density of redox flow lithium batteries can be about eight to 10 times as high as conventional redox flow batteries,” says Qing Wang, a materials scientist at the National University of Singapore who is a member of the team that made the breakthrough.

The key innovation: solid granules in the electrolyte tanks made from the same kinds of compounds that make up the anodes and cathodes in lithium-ion batteries. 

Previous research had explored using solid materials in redox flow batteries. But prior approaches used viscous slurries of solid materials, which can take a lot of energy to pump through a battery’s interior. The new redox flow lithium battery keeps the solid granules stationary, and only pumps the electrolytes around.

The scientists used granules of lithium iron phosphate for the cathode material and titanium dioxide for the anode material. The granules are porous, to increase the amount of surface area available for electricity-generating chemical reactions.

One challenge the scientists faced in developing this battery was fabricating the membrane separating the electrolytes. The membrane needed to possess high permeability to lithium ions, low permeability to other chemicals, and good mechanical and chemical stability. The researchers ultimately settled on a lithium-loaded composite membrane made of the commercially available electroactive polymer Nafion, which is commonly used in fuel cells, plus polyvinylidene difluoride, a tough plastic that is resistant to flame, electricity, and attack by most chemicals.

Still, says Wang, the membrane they used is not good enough for transporting lithium ions at the scale necessary for power storage applications. Future research is needed to improve the membrane and other parts of the battery before before the improved redox flow battery can be used by utilities.

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Belgian Regulators Approve Restart of Flawed Reactors

Belgian nuclear authorities have authorized the restart of two reactors whose steel reactor pressure vessels (RPVs)—which contain the reactors' fissioning cores and primary coolant—are riddled with flaws. The flaws were discovered during routine maintenance in 2012. After followup ultrasonic imaging of the RPVs, experimental testing of steel samples, and extensive computational analyses, the regulators accepted the operator’s argument that the RPV flaws are decades old and do not compromise the vessels’ structural integrity.

The flaws in Belgium’s Doel 3 and Tihange 2 reactors idled the two 1,000-megawatt reactors in 2012 and again in 2014, prompting preparations for potential blackouts in Belgium and stymying European grid operators’ efforts to upgrade their system for coordinating cross-border power flows. They also prompted European regulators to call for expanded ultrasonic testing of all RPVs—a move resisted by the U.S. Nuclear Regulatory Commission.  

The Belgian reactors will take about four weeks to restart, according to World Nuclear News. There’s no word yet on whether Brussels-based reactor operator Electrabel will seek to extend the operation of Tihange 2 and Doel 3, which reach their 40-year original design lifespan in 2022 and 2023, respectively. However, regulators approved 10-year extensions for the Doel plant's two older reactors last month.

An independent structural analysis by Oak Ridge National Laboratory (ORNL) in the United States affirmed the structural integrity of the Tihange 2 and Doel 3 reactors, says Richard Bass, a corporate fellow at ORNL and coauthor of the review commissioned by Belgium's Federal Agency for Nuclear Control (FANC). “As far as we’re concerned, the flaw population meets the ASME pressure vessel requirements,” says Bass, referring to the American Society of Mechanical Engineers’ RPV codes.

ORNL, the principal contractor for the U.S. Nuclear Regulatory Commission on RPV integrity issues, applied that expertise to evaluate the safety case for the Belgian reactors put forward by Electrabel. “We had about two months total, so we did everything that we could reasonably do during that period,” says Bass. 

Bass and his colleagues examined the flaws—a total of 16,196 disc-shaped gaps detected in the RPVs' steel plates—and ran simulations meant to indicate whether the faults would initiate cracks under various stress scenarios. Simulations focused on the rapid temperature fluctuations that could happen, for example, in the case of a loss-of-coolant accident such as occurred at Fukushima Daiichi in 2011. They also projected the embrittlement of the RPV as it ages.

Of the thousands of flaws in the two reactors, four faults flunked ORNL’s initial simulations. Bass said that ORNL then accounted for the fact that the loading on the RPV would occur while it was warm, which makes the steel more robust during subsequent cooling—a metallurgical phenomenon that ORNL demonstrated experimentally in the 1970s and 1980s. 

Three of the Belgian reactors' four questionable flaws were deemed compliant with safety regulations under pre-stress warming conditions. The remaining flaw, labeled flaw #1660, was cleared after closer scrutiny of its geometry. 

The initial screenings were performed with a simplification of the shape, in which each was assumed to be a circular disc—an approach that Bass calls “very conservative." When ORNL modeled flaw #1660 and found that it is an elliptical disc (roughly 8.5 millimeters across in one direction and 10 mm across in the other), it passed muster. 

"You change the problem and go back to the original representation that’s much closer to reality,” says Bass. "When we did that we found that the real flaw met the ASME code acceptance criteria.”  

ORNL did not estimate how big the RPVs' margin of safety is, but it is “significant” in Bass’ expert opinion: ”There is significant margin between the driving forces on the flaws and the toughness of the material."

ORNL also concurred with Electrabel’s calculations regarding the risk posed by hydrogen diffusing into the steel and forcing open cracks during temperature swings. "We looked at what they did and it looked reasonable to us,” says Bass.

FANC, meanwhile, concurred with Electrabel’s assertion, based on ultrasonic inspections in 2012 and 2014, that the flaws were created when the RPVs were forged and are not growing over time. Still, it approved the reactors to restart on the condition that Electrabel must reinspect the RPVs when they are next shut down for refuelling.

Several independent experts argued in 2014 that FANC had overlooked the risks posed by ongoing hydrogen diffusion. Among them was Digby Macdonald, a corrosion expert at the University of California at Berkeley. (Spectrum highlighted Macdonald’s concerns in April of this year.) 

FANC addressed their concerns in a special report released this week. The report cites input from several independent experts, including two proposed by Macdonald’s colleague Walter Bogaerts, a Belgian materials science expert. 

The independent experts affirmed that “significant experiment and theoretical results” constrain the pressure caused by hydrogen within the RPV to low levels: about 200 kilopascals at 25 degrees Celsius and 35 kPa at 300 °C. To put that in context, computations by Electrabel suggest that even hydrogen exerting 10 megapascals of pressure within the flaws would have a “small impact” on RPV integrity. 

Macdonald told IEEE Spectrum that he remains concerned about the FANC experts’ failure to “correctly address” the potential production of hydrogen within the reactor via radiolysis—the splitting of water molecules by nuclear radiation. However, he says he has yet to publish his own analysis of radiolysis.

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An All Wind, Water, and Solar Grid Will Be Stable Without Batteries

The U.S. electrical grid could rely completely on solar, wind, and water power, and existing low-cost methods of storing energy—rather than than giant battery farms—could help make up for the erratic nature of the sources of that electricity, researchers say.

Previous research suggested that the United States could get 100 percent of its energy from these green sources by 2050 and, more ambitiously, that the world could as well.

However, solar and wind are all intermittent sources of power—sometimes the sun doesn’t shine brightly and the wind doesn’t blow strongly. As such, power plants driven by fossil fuel are often brought in to compensate for the uncertain nature of these green sources of energy and to keep power grids stable.

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U.S. Airlines Could Cut Emissions In Half By 2050 With Minimal Cost

Heads of state will be talking climate in Paris this week. And next year, when the International Civil Aviation Organization meets, national representatives will find themselves under great pressure to sign a deal that reduces greenhouse gas emissions from air travel. Although improved aerodynamics, greater engine efficiency, and higher passenger density have cut per-passenger emissions in half compared with 1990 levels, total aviation emissions still increased by 3.6 percent every year, which means a doubling every 20 years.

But the aviation industry, which accounts for 2.5 percent of global carbon emissions, is already tackling the problem. In a bold open letter published in September, airline industry leaders including Boeing and Airbus vowed to flatten aviation emissions by 2020 and halve them by 2050 compared with a 2005 baseline.

A new study published in Nature Climate Change shows that this goal might just be reachable, at least in the industrialized world. The study shows that U.S. passenger airlines could cut emissions in half by 2050 compared with 2012 levels—a reduction of 2 percent per year for the next 35 years. Doing so would involve a few smart aircraft retrofits, design upgrades, and more efficient air traffic management and flight operations. These changes would have a minimal effect on the airlines’ bottom lines. In fact, a few carriers are already adopting some of these straightforward changes.

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Can Energous Deliver on Wireless Power Promises?

Wireless power sounds like an absolutely fantastic idea, in theory. All of your devices, charging themselves all the time, without you having to plug them in or even think about their batteries. Wearables you never have to take off. Cellphones that work when you need them to. Remote controls that never need the batteries changed. But, beaming power through the air in a safe, effective, and efficient way is hard, and so far, the technology isn’t always living up to the promises that it’s making.

The promises made by a company called Energous include multi-device charging using radio frequency energy out to a range of 4.5 meters, relying on transmitters integrated into home appliances and receivers that can easily fit into portable electronics. Last week, Energous released a report from Underwriters Laboratories (UL) that tested and verified the wireless power delivery provided by Energous’ WattUp transmitters and receivers. It answered some of our questions, but raised a few more, and we spoke with Energous founder and CTO Michael Leabman to get things all figured out.

Mostly.

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Getting Up Close and Personal With High-Voltage Electricity

As director of innovation at KEMA Laboratories in Arnhem, Netherlands, René Smeets is no stranger to power. The lab tests circuit breakers and transformers built for ultrahigh-voltage (UHV) transmission systems, ensuring that these components can control the titanic current flows unleashed during short circuits. KEMA’s strategies to mimic those extreme conditions in the lab, which Smeets describes in an article in the latest issue of Spectrum, give him an intimate understanding of how the components will perform when they’re deployed in vast, nation-spanning transmission networks.

Sometimes, however, this expert likes to get a broader view and see the equipment he tests in its natural habitat. In September, while in Shanghai for a meeting convened by the State Grid Corp. of China, Smeets and other UHV specialists got a tour of State Grid’s nearby Liantang substation (shown in the photo above). The utility says this facility, which receives electricity from coal-fired power plants in the interior province of Anhui, handles more high-voltage power than any other substation in the world. The brand new 1,100-kilovolt transmission system routinely delivers 6,900 megawatts of power to Shanghai. State Grid already has plans to scale it up to an astounding 10,000 MW.

What impressed Smeets most in this superlative substation? “All the components used in the station were Chinese-made,” he says. This fact didn’t surprise him, as KEMA Labs has tested many pieces of Chinese equipment in recent years. But it did demonstrate that China has developed a world-leading UHV industry. It’s an exciting time to be a UHV tourist, Smeets says: India’s Power Grid Corp. is now building a 1,200‑kV network, which will set a new mark for the highest-voltage transmission system. “It will be the pride of India,” Smeets says. He’s looking forward to a tour.

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Nuclear Waste Deep Storage Plans Approved

Finland’s government issued a construction license to nuclear disposal consortium Posiva last week, Reuters reported. The license gives the group approval to build a storage facility on Olkiluoto Island, Finland, designed to last 100,000 years.

The facility would be the first of its kind in the world. Since the beginning of the nuclear power age, energy firms have paid to store nuclear waste in temporary holding ponds unlikely to last more than a couple of centuries.  The Posiva facility, decades in the planning, may pioneer a more sustainable era of disposal. (See “Finland’s Nuclear Waste Solution,” IEEE Spectrum, December 2009.)

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The Global Energy Risk of Growing More Protein

The global shortlist of security concerns just became a bit longer: border security, cyber security, economic security, water security and now, protein security.

Access to high quality protein sources, beef or otherwise, is increasingly challenging for companies and nations as more of world’s population adopts Western diets, according to a new study from Lux Research.

With the considerable water and energy requirements to grow beef and many other protein sources, the research is meant to help stakeholders understand how to increase the amount of protein produced without jeopardizing environmental resources. 

The study looked at protein production data from more than 100 publications. The researchers then compared all of the protein sources across their entire life cycle. Each protein source was then benchmarked using the concept called “beef parity”, the total resource requirement and risk involved to produce the equivalent of 1 kilogram of beef protein.

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Shocking Trick To Desalinate Seawater

Getting clean water for drinking and agriculture to a burgeoning population is one of the most pressing challenges of this century. A natural place to turn to is the world’s oceans, but desalinating seawater has so far proven to be costly and energy-intensive.

Engineers at MIT have come up with a new desalination system that uses a shockwave to get the salt out of seawater. It could be a practical and energy-efficient method for desalination; water purification in remote locations and emergencies; and for cleaning brackish wastewater generated from hydraulic fracturing, the researchers say.

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Putting California Wind Power Out to Sea

Wind power developers eyeing California’s renewable energy market are literally floating a novel idea. Seattle-based Trident Winds has filed preliminary environmental documents for a farm of 100 floating wind turbines off California’s central coast, according to reporting this week by the San Jose Mercury News

Trident Winds’ proposal is a longterm bet—startup is probably a decade away according to CEO Alla Weinstein—but it's a vision that sounds less and less like science fiction. Just last week Norwegian oil and gas giant Statoil gave the green light to what is likely to be the world’s first floating wind farm, with construction set to begin next year near Scotland; it is to be generating 30 megawatts (MW) of power by the end of 2017. 

There is no doubt that California will need plenty of renewable energy as the state gears up to meet a new mandate requiring half of its power to be renewable by 2030. Less clear is whether it will be ready to stomach floating wind power's financial and maritime pricetag.

Floating turbines rely on the same types of spar buoys and tension-leg platforms used by offshore oil platforms, enabling them to access wind power in deeper waters well beyond the 40- to 50-meter limits of turbines on fixed foundations. That's an enabler for offshore wind power near coastlines that drop off quickly, such as California's, and it also provides access to the stronger, more consistent airflows that prevail further offshore. 

Trident Winds’ project would float offshore from the California coastal city of Morro Bay, which lies between Santa Cruz and San Luis Obispo. The plan calls for 10-MW floating turbines standing up to 194 meters tall, which the Mercury News notes is even taller than Morro Rock, "the craggy 581-foot-tall monolith that dominates” the local shoreline.

The fleet of 100 turbines would, of course, be 24 kilometers offshore and thus no competition for Morro Bay's iconic structure. That’s in marked contrast to Morro Bay’s old power plant. San Francisco–based PG&E shut down the coal-fired plant in 2013 but, according to the New York Times, the utility has no plans to demolish its three 137-meter smokestacks

Floating wind turbines have been in the pilot/demonstration phase since the first turbines were installed offshore in Europe in 2007 and 2008. They stepped up in power significantly with the 2009 installation of a 2.3-MW, 65-meter-tall machine off the Norwegian coast by Statoil. Berkeley-based floating wind developer Principle Power (previously led by Trident Winds' Weinstein) installed a 2-MW machine in Portuguese waters in 2011. 

Since then even bigger machines have been floated. In August a consortium of Japanese industrial firms anchored a 7-MW, 105-meter-high turbine off the coast of Fukushima. Statoil’s Scottish wind park plans call for six 6-megawatt machines

Larger scale is seen as critical to making deepwater installations cost-effective, which makes Trident Winds’ proposal for 10-MW turbines understandable. The Guardian’s reporting on Statoil’s project suggests that scale could ultimately render floating turbines more cost-effective than today’s fixed offshore turbines. Citing a June 2015 report from the U.K.’s Carbon Trust, it says the current global average for offshore wind is £112 ($169) per megawatt-hour (MWh), whereas “larger concepts” for floating wind such as Statoil’s could produce power at £85–95/MWh.

Design could help too. The innovator behind the very first floating offshore turbine test recently launched a crowd-funding campaign to fund certification of a simplified turbine for offshore use, redesigned from the ground up with floating installation and operation in mind. 

Cost reductions will be critical to selling offshore wind in the U.S. Since at least 2013, Principle Power has been advancing a proposal to install floating turbines off the coast of Oregon. But, as this weekend’s Mercury Star report notes, Principle Power's projected $240/MWh pricetag is “more than the utilities in Oregon want to pay.” 

Another challenge facing technology proponents is demonstrating that their floating leviathans will have limited impacts on the marine environment. European studies have found that offshore wind farms have limited impact on seabirds. But location is everything, and conservation groups will be looking for reassurance that the technology will be benign for the birds frequenting the U.S. Pacific coast.

A more difficult flashpoint could be impacts on fishing resources. Trident Winds’ project would create a 162-square-kilometer no go zone for drag nets, thanks to power cables dangling between the floating turbines.

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