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Advanced Materials

Roofs Covered With Plastic Grass Could Harness Wind Energy

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Advanced Materials

One group of scientists is trying to harness wind energy by mimicking the motions of a field of grass rippling in the breeze—except their grass is made of plastic and their field is on a roof.

According to the findings publishing in the journal Advanced Materials, a joint team of Chinese and American researchers created an experimental turboelectric nanogenerator (TENG). Here's how it works: The team adhered plastic strips to a board in a way that makes them stand upright in rows. One side of each strip is coated with nanowires and the other side with indium tin oxide (ITO). When the “grass” is pushed by the wind, the nanowires brush against the ITO sides of the surrounding strips, allowing electrons to pass from one piece to the next. This generates a current via the triboelectric effect.

This method of generating wind power could be practical in many situations. In addition to harnessing power from steady gusts, the technology would be able to effectively work with choppy winds blowing in any direction and would be ideal for spots where windmills would be impractical.

The experimental TENG—which so far has only been tested in a lab by using an electric fan and 60 strips of plastic on a model rooftop—generated enough energy to light 60 LEDs. The system was also functional in wind speeds as low as 13 mph and was most effective in close to 62-mph winds—a speed too high to be practical, as one researcher noted to New Scientist.

While the project is still far from ready to be used out in the real world, a 985-square-foot rooftop carpeted with the strips would generate 7.11 kilowatts, enough energy to mostly power a home, according to the researchers. For now, the team is focused on figuring out a way to efficiently store the energy that’s generated. They will also need to find a substitute for indium tin oxide because it's both toxic and expensive. 

[h/t: New Scientist]

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11-Year-Old Creates a Better Way to Test for Lead in Water
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In the wake of the water crisis in Flint, Michigan, a Colorado middle schooler has invented a better way to test lead levels in water, as The Cut reports.

Gitanjali Rao, an 11-year-old seventh grader in Lone Tree, Colorado just won the 2017 Discovery Education 3M Young Scientist Challenge, taking home $25,000 for the water-quality testing device she invented, called Tethys.

Rao was inspired to create the device after watching Flint's water crisis unfold over the last few years. In 2014, after the city of Flint cut costs by switching water sources used for its tap water and failed to treat it properly, lead levels in the city's water skyrocketed. By 2015, researchers testing the water found that 40 percent of homes in the city had elevated lead levels in their water, and recommended the state declare Flint's water unsafe for drinking or cooking. In December of that year, the city declared a state of emergency. Researchers have found that the lead-poisoned water resulted in a "horrifyingly large" impact on fetal death rates as well as leading to a Legionnaires' disease outbreak that killed 12 people.

A close-up of the Tethys device

Rao's parents are engineers, and she watched them as they tried to test the lead in their own house, experiencing firsthand how complicated it could be. She spotted news of a cutting-edge technology for detecting hazardous substances on MIT's engineering department website (which she checks regularly just to see "if there's anything new," as ABC News reports) then set to work creating Tethys. The device works with carbon nanotube sensors to detect lead levels faster than other current techniques, sending the results to a smartphone app.

As one of 10 finalists for the Young Scientist Challenge, Rao spent the summer working with a 3M scientist to refine her device, then presented the prototype to a panel of judges from 3M and schools across the country.

The contamination crisis in Flint is still ongoing, and Rao's invention could have a significant impact. In March 2017, Flint officials cautioned that it could be as long as two more years until the city's tap water will be safe enough to drink without filtering. The state of Michigan now plans to replace water pipes leading to 18,000 households by 2020. Until then, residents using water filters could use a device like Tethys to make sure the water they're drinking is safe. Rao plans to put most of the $25,000 prize money back into her project with the hopes of making the device commercially available.

[h/t The Cut]

All images by Andy King, courtesy of the Discovery Education 3M Young Scientist Challenge.

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Switzerland Flushes $1.8 Million in Gold Down the Sewer Every Year
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Switzerland has some pretty valuable sewer systems. As Bloomberg reports, scientists have discovered around $1.8 million worth of gold in the country's wastewater, along with $1.7 million worth of silver.

Scientists at the Swiss Federal Institute of Aquatic Science and Technology examined sewage sludge and effluents, or discharged liquid waste, from 64 water treatment plants and major Swiss rivers. They did this to assess the concentrations of various trace elements, which are "increasingly widely used in the high-tech and medical sectors," the scientists explained in a press statement. "While the ultimate fate of the various elements has been little studied to date, a large proportion is known to enter wastewater."

The study, which was recently published online in the journal Environmental Science & Technology, revealed that around 94 pounds of gold makes its way through Switzerland's sewage system each year, along with 6600 pounds of silver and high concentrations of rare metals like gadolinium and niobium. For the most part, these metals don't harm the environment, researchers say.

With gold and silver quite literally flowing through their sewers, is there any way that Switzerland could turn their wastewater into wealth? Scientists are skeptical: "The recovery of metals from wastewater or sludge is scarcely worthwhile at present, either financially or in terms of the amounts which could be extracted," the release explains.

However, in the southern canton of Ticino, which is home to several gold refineries, the "concentrations of gold in sewage sludge are sufficiently high for recovery to be potentially worthwhile," they conclude.

Switzerland is famous for its chocolate, watches, and mountains, but it's also home to major gold refineries. On average, around 70 percent of the world's gold passes through Switzerland every year—and judging from the looks of it, much of it goes down the drain. As for the sewer silver, it's a byproduct of the chemical and pharmaceutical industry, which is a cornerstone of Switzerland's economy.

[h/t Bloomberg]

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