Gizmorama - January 18, 2016

Good Morning,

In today's issue I have a pair of stories that deal with makeovers. Maybe 'makeover' is the wrong word, 're-design', that's better. Scientists are working on the re-design of the incandescent light bulb and lithium-ion battery which could mean huge developments in the energy world.

Learn about this and more interesting stories from the scientific community in today's issue.

Until Next Time,
Erin

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*-- MIT scientists give the incandescent light bulb a makeover --*
BOSTON - Even the most eco-friendly miss the warm glow of incandescent light.

Concerns about energy efficiency -- and subsequent regulatory standards -- and have brought about hybrid incandescent and halogen bulbs, CFLs and LEDs, that do more with less. But detractors say the light they produce is harder and colder.

Researchers at MIT have set out to solve this problem, intent on bringing back the soft buttery yellows of the traditional incandescent light bulb, but with 21st century tech.

The incandescent bulb is more than a century old. They produce beautiful light by passing electricity through a tiny filament. The problem, however, is that 90 percent of their energy is wasted, escaping in the form of heat.

Physicist at MIT have solved this problem by creating a light bulb that prevents the thermal energy from dissipating. Their new light bulb encases a traditional light-emitting filament in a photonic crystal that reflects the escaping thermal energy back toward the filament where it is reabsorbed and converted to light.

The crystal is made of thin layers of Earth-abundant elements, stacked and deposited on a substrate. The crystal works to reflect a variety of wavelengths, arriving at an array of angles, but allows the necessary wavelengths of warm incandescent light to pass through.

"It recycles the energy that would otherwise be wasted," lead researcher Marin Soljacic, a physics professor at MIT, told MIT News.

Computer models suggest the technology can eventually be perfected enough to achieve efficiencies as high as 40 percent. The best incandescent bulbs peak at 2 or 3 percent. Flourescents boast efficiencies between 7 and 15 percent, while compact LEDs range from 5 to 15 percent.

The first proof-of-concept prototype topped out well short of 40 percent, but its 6.6 percent efficiency is already on par with LEDs and CFLs.

"The results are quite impressive, demonstrating luminosity and power efficiencies that rival those of conventional sources including fluorescent and LED bulbs," said Alejandro Rodriguez, an assistant professor of electrical engineering at Princeton University who was not involved with the research.

Rodriguez thinks the findings will inspire additional incandescent emission technologies. Soljacic says the true potential of the research -- published in the journal Nature Nanotechnology -- isn't yet realized, and that unforeseen applications, beyond illumination, lie ahead.

"The ability to control thermal emissions is very important," he said. "That's the real contribution of this work."


*-- Stanford scientists build battery that won't overheat --*
PALO ALTO, Calif. - Scientists at Stanford have designed a lithium-ion battery that doesn't overheat. The battery shuts itself off when temperatures get too high, and powers back on once it's sufficiently cooled.

Researchers say the new technology will help prevent battery fires in electronics like laptops and hoverboards.

"People have tried different strategies to solve the problem of accidental fires in lithium-ion batteries," Zhenan Bao, a professor of chemical engineering at Stanford, explained in a press release. "We've designed the first battery that can be shut down and revived over repeated heating and cooling cycles without compromising performance."

Your average rechargeable lithium-ion battery is made up of two lithium electrodes, one positive and one negative, and an intermediary electrolyte liquid or gel that enables ionic movement -- the transfer of electrons from one end to the other.

Under certain conditions, the cycle of charging and discharging can push the temperature of the battery's electrolyte material into unsafe territory. When the electrolyte's temperature rises above 300 degrees Fahrenheit, it can catch on fire and cause an explosion of flames.

Hoverboards were a popular gift over the holidays, and in their wake, dozens of YouTube videos have documented the contraption's tendency to spontaneously combust. The problem was enough to move some college campuses to ban the vehicle.

To solve this battery problem, researchers installed a thin film of elastic polyethylene between the electrodes and the electrolyte. The film acts like a governor. Inside the film are spiky nanoparticles made of nickel. The spikes are coated with graphene to enhance conductivity.

"We attached the polyethylene film to one of the battery electrodes so that an electric current could flow through it," lead study author Zheng Chen, a postdoctoral scholar at Stanford, said in a press release. "To conduct electricity, the spiky particles have to physically touch one another. But during thermal expansion, polyethylene stretches. That causes the particles to spread apart, making the film nonconductive so that electricity can no longer flow through the battery."

The film can be calibrated so that the particles don't separate until a specific temperature is reached. In their prototype battery, researchers designed the film to expand at just the right pace for the nanoparticles to separate and the battery to shut down above 160 degrees Fahrenheit.

Scientists tested the new technology -- described in the journal Nature Energy -- using a hot air gun, and found the safety mechanism is accurate, effective and reversible. The battery's electricity quickly resumes after it cools below 160 degrees Fahrenheit.

"Compared with previous approaches, our design provides a reliable, fast, reversible strategy that can achieve both high battery performance and improved safety," Stanford engineer Yi Cui said. "This strategy holds great promise for practical battery applications."

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