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Porous Silicon Battery Electrodes from Reeds

Natural structures in reed leaves could find use in advanced lithium-ion batteries, which could lead to a more sustainable way to create sophisticated energy-storage devices, scientists in China and Germany say.

Silicon-based materials can theoretically store more than 10 times charge than the carbon-based materials most commonly used in the anodes of commercial lithium-ion batteries, making them promising next-generation anode materials. However, silicon’s big problem is that it can swell by more than 300 percent when filled with lithium. The constant swelling and shrinking as the battery charges and discharges, causes the anode to crack. One way to overcome this problem is to make silicon porous enough to accommodate the expansion. But synthesizing these structures is commonly a complex, energy-intensive, and costly process.

Now scientists have developed 3-D porous silicon-based anode materials using the kind of reed leaves that are abundant in temperate wetlands. Reeds naturally absorb silica from the soil, which accumulates in sheet-like structures around micro-compartments in the plants.

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Nanowires Boost Hydrogen Production from Sunlight Tenfold

Using the energy of the sun to split water into hydrogen and oxygen gives you access to a completely carbon-free energy source for transportation. But so far, the efficiency of the process has been a bit disappointing, even when using systems called solar-fuel cells—a solar cells immersed in the water it’s splitting.

Now researchers from Eindhoven University of Technology in The Netherlands and the Dutch Foundation for  Fundamental Research on Matter (FOM) report in the 17 July issue of Nature Communications  that they have improved tenfold the hydrogen producing capacity of a solar fuel cell. The key was to use a photocathode—the electrode that supplies electrons when illuminated by sunlight—made from an array of gallium phosphide nanowires.

Previously, researchers used flat surfaces of the semiconductor gallium phosphide as the photocathode, but light absorption was low.  The GaP nanowires, about 500 nm long and 90 nm thick, increased enormously the surface of the photocathode exposed to light.  By adding platinum particles, its catalytic properties improved hydrogen production even more, report the researchers.

At the same time, the nanowires allowed a drastic reduction in the use of GaP material. “For the nanowires we needed ten thousand times less precious GaP material than in cells with a flat surface. That makes these kinds of cells potentially a great deal cheaper,” said Erik Bakkers of Eindhoven University of Technology, as quoted in a press release.

“In addition, GaP is also able to extract oxygen from the water—so you then actually have a fuel cell in which you can temporarily store your solar energy. In short, for a solar fuels future we cannot ignore gallium phosphide any longer,” he added.
 

Diesel-Powered Fuel Cell Produces Clean Electricity

Although several options to store hydrogen as a fuel for cars have been investigated, a practical and affordable way to store and distribute hydrogen is still the biggest hurdle to the wide deployment of green, CO2-emission-free cars. Now researchers in Europe have built a demonstration system that might be a first step in circumventing the limitations on hydrogen distribution and storage; they simply extract hydrogen from diesel fuel on the go.  

The research group, "Fuel Cell Based Power Generation (FCGEN)," which includes researchers from Volvo Technology (Sweden), Johnson-Matthey (United Kingdom), Modelon AB (Sweden), PowerCell AB (Sweden), Jožef Stefan Institute (Ljubljana, Slovenia), Forschungszentrum Jülich (Germany) and Fraunhofer ICT-IMM (Mainz, Germany) announced in a recent press release the creation of a prototype 3-kilowatt, diesel-fueled fuel cell system that has operated flawlessly for 10,000 hours. 

The extraction of the hydrogen from the diesel fuel happens through autothermal reforming, a catalytic reaction in which the diesel fuel is decomposed into hydrogen, steam, carbon dioxide, and carbon monoxide.  The CO is then converted to CO2 and water, explains Boštjan Pregelj of the Jožef Stefan Institute, and who is the Principal Investigator of the FCGEN project.

It didn’t escape their notice that the extraction of hydrogen from the diesel fuel releases CO2 directly into the atmosphere.  “Actually all carbon in the diesel is converted to CO2, but since the efficiency [of the overall process] is about five times [that of a diesel] engine idling, fuel consumption is 80 percent lower, and consequently, the produced amount of CO2 is decreased by 80 percent,” says Pregelj. That is why the “green” label was given."

The researchers say that the system could generate between 3 and 10 kW of power in trucks; on small aircraft, it would power air conditioners and refrigeration systems. In addition to lowering CO2 emission, the units produce little noise, making them suitable as mobile electricity generators in places, like field hospitals, where quiet is appreciated. 

Transactive Energy Controls Survive First Test in Pacific Northwest

For the past five years, a consortium of researchers, technology companies, and power utilities have been testing a novel power delivery system in the Pacific Northwest of the United States.

The Pacific Northwest Smart Grid Demonstration project was far reaching and had more than 50 experiments, but the most cutting edge was testing transactive controls for the power grid. The project was led by Battelle and funded by the U.S. Department of Energy. 

Transactive control involves an automated communication and control system connecting energy providers and users, who constantly exchange information about price and availability of power. When an energy provider predicts a surge in power demand, and therefore also higher prices, for example, it sends out this information as “transactive signals” to the rest of the network, including users. Based on these signals, smart grid technologies can react, reducing power use at the right time. The goal is improving reliability and efficiency, allowing for more dynamic balancing of resources, especially in regions that rely on high levels of renewables.

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Antineutrino Detectors Could Be Key to Monitoring Iran's Nuclear Program

President Obama has made it clear in a statement that the Iran nuclear deal signed yesterday was “built on verification.” Technology built to detect an elusive subatomic particle called the antineutrino could help.

The International Atomic Energy Agency wants a reactor-monitoring tool that is portable, safe, inexpensive, and remotely controllable. Antineutrino detectors, which give a peek into how much uranium and plutonium are in a reactor core, promise all of that.

The technology, which has been in the works since the early 2000s, has improved tremendously in the past five years, and it is now almost ready for practical use, says Patrick Huber, a physics professor at the Center of Neutrino Physics at Virginia Tech in Blacksburg. “Less than two years from now, you should have at least one maybe several types of antineutrino detector technologies that would work as nuclear safeguard detectors.”

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New Study Finds Feedback Loop Between Air Travel and Climate Change

Airplanes emit greenhouse gases that cause global warming. Now, a study published in Nature Climate Change suggests that air travel and climate change could actually be coupled in a loop. Changing wind patterns due to a warming climate could lengthen certain flight times, resulting in long-haul flights burning even more fuel and emitting yet more greenhouse gases.

Researchers at the Woods Hole Oceanographic Institution wanted to see how flying times between Hawaii and the western US coast were affected by jet-altitude winds. From a Department of Transportation public database, they got departure and arrival times for every single flight going back and forth between Honolulu and Los Angeles, San Francisco and Seattle for the past 20 years. That was a total of 250,000 flights operated by four major airlines.

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Wind Turbines Power Liquid-Air Energy Storage

One startup energy company is looking to reinvent not only wind energy, but also energy storage.

Keuka Energy recently launched a 125-kilowatt prototype vessel that uses its novel floating wind turbine design paired with liquid-air energy storage to create a steady source of electricity.

Unlike traditional wind turbines, which have three blades and a central gearbox, Keuka’s turbine is a pinwheel of aluminum blades that sits atop a floating V-shape platform containing liquid air.

The Florida-based company claims that its wind turbine design allows for larger turbines that could produce far more electricity. The world’s largest single offshore wind turbine is currently about 6 megawatts; Keuka says its full-size turbines could produce at least double that amount.

Liquid-air energy storage, also sometimes called cryogenic energy storage, is a long-term energy storage method: electricity liquefies air to nearly -200°C and then stores it at low pressure. When the energy is needed, the liquid air is pumped to a high level of pressure and heated to a gas state. The gas then drives a turbine.

Although it is an attractive energy-storage technology because of its long duration, liquid-air energy storage requires a significant amount of electricity to make the liquid air, limiting its usage by utilities. Keuka claims that because its design substantially reduced the cost by supplying the power directly from the turbines to the liquefaction equipment.

The company also says its wind turbine design is more cost effective, thanks to elimination of the gear box and the use of light-weight aluminum blades that cost less than 10 percent the price of traditional composite blades. Even if the technology is effective and can come in at lower costs, Keuka will likely face a long road to acceptance by the notoriously risk averse utility industry.

Keuka is not the only startup looking to advance liquid-air energy storage. In 2014, General Electric signed an exclusive global licensing deal with Highview Power Storage, a U.K. startup that makes utility-scale liquid-air energy storage systems.

Another similar technology that has gained more traction is compressed-air energy storage, which does not have the energy density of liquid air, but so far has proven more cost effective. Compressed air, while a cheap form of energy storage once built, is still expensive to build and geographically limited; underground caverns are needed to store the air.

Other startups are also looking offshore for cheap energy storage. Bright Energy is developing a system that would use offshore renewable energy to store compressed air in vessels in the ocean. Canadian startup Hydrostor also has a design to store compressed air underwater. 

If Keuka’s 125-kilowatt prototype is successful, it plans to launch a larger 25 MW demonstration project in early 2017.

DOE Launches New Grid-Connected Wave Power Project in Hawaii

The U.S. Department of Energy (DOE) has launched a new wave power device to bring renewable power to the island of Oahu in Hawaii.

Northwest Energy Innovation has developed a float that is attached to a hull under the water. The device captures both the vertical and horizontal motion of the wave, and the energy that is captured is the result of the relative rotation between the hull and the float. The energy is then transferred via a cable to land.

The device, named Azura, will be installed at the U.S. Navy’s Wave Energy Test Site in Kaneohe Bay. It will be independently tested by the University of Hawaii.

The 20-kilowatt demonstration project will run for one year. It is the first time a grid-connected, wave energy device has been deployed and independently tested for that period of time in the United States, according to the DOE.

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Chemical Battery Can Recharge Itself With Light

Batteries, by definition, convert chemical energy into electricity. Once you’ve sucked them dry, you have to reverse the process to convert electricity into chemical energy, and for that, you need a source of electricity. It’s not like it’s hard to do this, but it is certainly a minor annoyance that could do with a fix.

Researchers at the Indian Institute of Science Education and Research (IISER) in Pune, India, have skipped the annoying step by developing a battery that charges directly from light. We’re not talking about a battery with a solar panel on it: it’s a “photo battery” where the anode itself is made of titanium nitride and ambient light.   

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Doping Lithium-ion Batteries to Make Them Safer

Fires resulting from the catastrophic failure of lithium-ion batteries could be prevented with chemical additives, say researchers at Stanford University.

When lithium-ion batteries overheat, they can burn through internal pockets, burst into flames, and even explode. One reason such damage can occur is the formation of dendrites—finger-like deposits of lithium that can grow long enough to pierce the barrier between a lithium-ion battery's halves and cause it to short out.

Dendrites form when a battery electrode degrades and metal ions deposit onto the electrode's surface. Previously, scientists at Stanford developed a lithium-ion battery that can detect when dendrites start to puncture the barrier between its halves and warn that it needs to be replaced.

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