Scientists have created a nanoscale light detector that can convert light to energy, combining both a unique fabrication method and light-trapping structures.

In today’s increasingly powerful electronics, tiny materials are a must as manufacturers seek to increase performance without adding bulk. Smaller is also better for optoelectronic devices—like camera sensors or solar cells—which collect light and convert it to electrical energy.

Think, for example, about reducing the size and weight of a series of solar panels, producing a higher-quality photo in low lighting conditions, or even transmitting data more quickly.

However, two major challenges have stood in the way: First, shrinking the size of conventionally used “amorphous” thin-film materials also reduces their quality. And second, when ultrathin materials become too thin, they are almost transparent—and actually lose some ability to gather or absorb light.

The new nanoscale light detector, a single-crystalline germanium nanomembrane photodetector on a nanocavity substrate, could overcome both of these obstacles.

“We’ve created an exceptionally small and extraordinarily powerful device that converts light into energy,” says Qiaoqiang Gan, associate professor of electrical engineering in the University at Buffalo’s School of Engineering and Applied Sciences and one of the paper’s lead authors. “The potential applications are exciting because it could be used to produce everything from more efficient solar panels to more powerful optical fibers.”

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Instead of batteries, a new cell phone harvests the few microwatts of power it needs from a different source: ambient radio signals or light.

Researchers were also able to make Skype calls using the battery-free phone, demonstrating that the prototype—made of commercial, off-the-shelf components—can receive and transmit speech and communicate with a base station.

“We’ve built what we believe is the first functioning cell phone that consumes almost zero power,” says Shyam Gollakota, an associate professor of computer science & engineering at the University of Washington and coauthor of the paper.

“To achieve the really, really low power consumption that you need to run a phone by harvesting energy from the environment, we had to fundamentally rethink how these devices are designed.”

Researchers eliminated a power-hungry step in most modern cellular transmissions—converting analog signals that convey sound into digital data that a phone can understand. This process consumes so much energy that it’s been impossible to design a phone that can rely on ambient power sources.

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By: Richard B. Rood, University of Michigan

Earth’s climate is changing rapidly. We know this from billions of observations, documented in thousands of journal papers and texts and summarized every few years by the United Nations’ Intergovernmental Panel on Climate Change. The primary cause of that change is the release of carbon dioxide from burning coal, oil and natural gas.

One of the goals of the international Paris Agreement on climate change is to limit the increase of the global surface average air temperature to 2 degrees Celsius, compared to preindustrial times. There is a further commitment to strive to limit the increase to 1.5℃.

Earth has already, essentially, reached the 1℃ threshold. Despite the avoidance of millions of tons of carbon dioxide emissions through use of renewable energy, increased efficiency and conservation efforts, the rate of increase of carbon dioxide in the atmosphere remains high.

International plans on how to deal with climate change are painstakingly difficult to cobble together and take decades to work out. Most climate scientists and negotiators were dismayed by President Trump’s announcement that the U.S. will withdraw from the Paris Agreement.

But setting aside the politics, how much warming are we already locked into? If we stop emitting greenhouse gases right now, why would the temperature continue to rise?

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In an effort to develop a more affordable, plentiful alternative to lithium-ion batteries, researchers from Purdue University are pursuing rechargeable potassium based batteries, demonstrating a way to derive carbon for battery electrodes from old tires.

“With the growth of rechargeable batteries for electronic devices, electric vehicles and power grid applications, there has been growing concern about the sustainability and cost of lithium,” says Vilas G. Pol, an associate professor in the Davidson School of Chemical Engineering at Purdue University and former member of ECS. “In the last decade, there has been rapid progress in the investigation of metal-ion batteries beyond lithium, such as sodium and potassium.”

Researchers in the field believe that potassium based batteries show potential for large-scale grid storage due to their low cost and the abundance of the element itself.

“The intermittent energy generated from solar and wind requires new energy storage systems for the grid,” Pol says. “However, the limited global availability of lithium resources and high cost of extraction hinder the application of lithium-ion batteries for such large-scale energy storage. This demands alternative energy storage devices that are based on earth-abundant elements.”

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By: Joshua D. Rhodes, University of Texas at Austin

Science is messy, but it doesn’t have to be dirty.

On June 19, a group of respected energy researchers released a paper in the journal Proceedings of the National Academy of Sciences (PNAS) that critiqued a widely cited study on how to power the U.S. using only renewable energy sources. This new paper, authored by former NOAA researcher Christopher Clack and a small army of academics, said that the initial 2015 study had “errors, inappropriate methods and implausible assumptions,” about using only the sun, wind and water to fuel the U.S.

What followed was a storm of debate as energy wonks of all stripes weighed in on the merits of the PNAS analysis. Mark Z. Jacobson, a Stanford University professor who was the lead author of the 2015 study, shot back with detailed rebuttals, in one calling his fellow researchers “fossil fuel and nuclear supporters.”

Why the big kerfuffle? As an energy researcher who studies the technologies and policies for modernizing our energy system, I will try to explain.

In general, getting to a clean energy system – even if it’s 80 percent renewable – is a well agreed-upon goal and one that can be achieved; it’s that last 20 percent – and how to get there – that forms the main point of contention here.

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Researchers from Argonne National Laboratory and Oregon State University have developed new cathode architecture for lithium-sulfur batteries. The team, led by ECS member Khalil Amine, incorporated graphene and sulfide nanoparticles to improve electrical conductivity in the promising lithium-sulfur batteries.

Lithium-sulfur batteries hold major promise as researchers explore the range of energy storage technologies. With an extremely high theoretical energy density, these batteries have the potential to store up to five times as much energy as today’s best lithium-ion battery.

But there are barriers preventing that theoretical density from becoming an actual density. Namely, the discharge products of sulfur electrodes and cycling intermediates produced.

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Using energy stored in the batteries of electric vehicles to power large buildings not only provides electricity for the building, but also increases the lifespan of the vehicle batteries, new research shows.

Researchers have demonstrated that vehicle-to-grid (V2G) technology can take enough energy from idle electric vehicle (EV) batteries to be pumped into the grid and power buildings—without damaging the batteries.

This new research into the potentials of V2G shows that it could actually improve vehicle battery life by around ten percent over a year.

For two years, Kotub Uddin, a senior research fellow at the University of Warwick’s Warwick Manufacturing Group, and his team analyzed some of the world’s most advanced lithium ion batteries used in commercially available EVs—and created one of the most accurate battery degradation models existing in the public domain—to predict battery capacity and power fade over time, under various aging acceleration factors—including temperature, state of charge, current, and depth of discharge.

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A new development in electrolyte chemistry, led by ECS member Shirley Meng, is expanding lithium-ion battery performance, allowing devices to operate at temperatures as low as -60° Celsius.

Currently, lithium-ion batteries stop operating around -20° Celsius. By developing an electrolyte that allows the battery to operate at a high efficiency at a much colder temperature, researchers believe it could allow electric vehicles in cold climates to travel further on a single charge. Additionally, the technology could allow battery-powered devices, such as WiFi drones, to function in extreme cold conditions.

(MORE: Read ECS’s interview with Meng, “The Future of Batteries.”)

This from UC San Diego:

The new electrolytes also enable electrochemical capacitors to run as low as -80 degrees Celsius — their current low temperature limit is -40 degrees Celsius. While the technology enables extreme low temperature operation, high performance at room temperature is still maintained. The new electrolyte chemistry could also increase the energy density and improve the safety of lithium batteries and electrochemical capacitors.

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Researchers have developed a new kind of semiconductor alloy capable of capturing the near-infrared light located on the edge of the visible light spectrum.

Easier to manufacture and at least 25 percent less costly than previous formulations, it’s believed to be the world’s most cost-effective material that can capture near-infrared light—and is compatible with the gallium arsenide semiconductors often used in concentrator photovoltaics.

Concentrator photovoltaics gather and focus sunlight onto small, high-efficiency solar cells made of gallium arsenide or germanium semiconductors. They’re on track to achieve efficiency rates of over 50 percent, while conventional flat-panel silicon solar cells top out in the mid-20s.

“Flat-panel silicon is basically maxed out in terms of efficiency,” says Rachel Goldman, a professor of materials science and engineering, as well as physics at the University of Michigan, whose lab developed the alloy. “The cost of silicon isn’t going down and efficiency isn’t going up. Concentrator photovoltaics could power the next generation.”

Varieties of concentrator photovoltaics exist today. They are made of three different semiconductor alloys layered together. Sprayed onto a semiconductor wafer in a process called molecular-beam epitaxy—a bit like spray painting with individual elements—each layer is only a few microns thick. The layers capture different parts of the solar spectrum; light that gets through one layer is captured by the next.

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Scientists have found a way to wirelessly transmit electricity to a nearby moving object.

The method may have applications in transportation, medical devices, and more. If electric cars could recharge while driving down a highway, for example, it would virtually eliminate concerns about their range and lower their cost, perhaps making electricity the standard fuel for vehicles.

“In addition to advancing the wireless charging of vehicles and personal devices like cellphones, our new technology may untether robotics in manufacturing, which also are on the move,” says Shanhui Fan, a professor of electrical engineering at Stanford University and senior author of the study.

“We still need to significantly increase the amount of electricity being transferred to charge electric cars, but we may not need to push the distance too much more,” he says.

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