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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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iStock // Ekaterina Minaeva
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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Name the Author Based on the Character
May 23, 2017
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