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kathleenseiber · 4 years ago

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A new kind of power walking

Scientists are constantly searching for new and clever ways to make electricity. Earlier this year, for example, Cosmos reported on a new device powered by a microbe that, the US creators say, can generate it from moisture in the air.

Others are working on clothes that can produce electricity, offering the enticing promise of plugging your phone into your jacket for a battery top-up.

Now researchers from China’s Beijing Institute of Nanoenergy and Nanosystems have developed a “tiny wind turbine” they say can scavenge energy while people walk and move their arms. And their vision is that rather than plugging in your phone, it could be added to the phone itself.

Luckily, it doesn’t involve strapping a windmill under your arm. Instead, two plastic strips in a tube flutter or clap together when there is airflow. As they separate, each becomes electrically charged thanks to the triboelectric effect, which can then be captured and stored.

The effect is basically similar to rubbing a balloon to your hair, or a pen on your sleeve. As the objects are separated, the electric charges either attract (like making your hair stand on end) or repel dissimilar or similarly charged objects, respectively. Those electric charges can be used as an energy source, the researchers suggest.

According to their results, which are published in the journal Cell Reports Physical Science, the effect can be created with minimal breeze: as little as 1.6 metres / second, or the same as someone’s arm swinging as they walk. It worked best with a wind speed of 4–8 metres / second, when the plastic strips would flutter in sync.

“You can collect all the breeze in your everyday life,” says Ya Yang, who oversaw the research. “We once placed our nanogenerator on a person’s arm, and a swinging arm’s airflow was enough to generate power.”

Already the device has a higher efficiency than other wind-scavenging approaches, say the researchers. They released a video (below) of the device powering 100 LED lights, albeit flickering on and off.

Credit: Chen, Ma and Ren et al./Cell Reports Physical Science

Not only does the device allow scavenging of wind energy that would otherwise not be exploited, the team says it can be made simply and cheaply using low-cost materials.

“Unlike wind turbines that use coils and magnets, where the costs are fixed, we can pick and choose low-cost materials for our device,” says Yang.

“We can place these devices where traditional wind turbines can’t reach. We can put it in the mountains or on the top of buildings for sustainable energy. Our device can also be safely applied to nature reserves or cities because it doesn’t have the rotating structures.”

Their next steps are to make the nanogenerator both smaller and larger.

They hope to shrink the device to make it compact and efficient enough that it can be added to existing devices. Yang says he sees a future where the generator can attach and provide sustainable power to mobile phones.

However, the team also want to scale it up and make it more powerful: potentially equal in output to traditional wind turbines.

“Our intention isn’t to replace existing wind-power-generation technology. Our goal is to solve the issues that the traditional wind turbines can’t solve,” Yang says.

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materialsworld · 7 years ago

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Hydrogels for stretchy, transparent power device

Image: Xiong Pu et al

Researchers at the Beijing Institute of Nanoenergy and Nanosystems, China, have developed a wearable device that can harvest energy from motions such as the tap of a hand.

It is highly stretchable and transparent – qualities that have never been simultaneously achieved in a biocompatible device. It could be promising in self-powered soft robots or self-powered electronic skins, among other applications.

In the last decade, researchers have made great strides in flexible electronics (see this article from June’s Materials World for just one example), but corresponding power devices – which should possess equal flexibility –haven't necessarily kept up.

Using hydrogels, Xiong Pu and colleagues created STENG, a transparent skin-like generator device capable of extreme stretchability. It is derived from a recently developed nanogenerator known as TENG, which converts mechanical or thermal energy into electricity and possesses reasonably good stretchability.

Distinct from its predecessors, STENG employs an ionic (not electrical) conductor as the electrode, allowing for greater stretch under strain. In various tests, this device achieved stretch ratios over 1,000% and ultra-high transparency (critical for transmittal of optical information) of 96.2%.

In addition to high transparency and stretchability, the device also showed durability at high temperatures (30ºC), and in high humidity (roughly 30%) – conditions which have deteriorated such devices in the past.

What is more, it successfully generated significant electrical power densities in several experiments, in response to motion, including in those involving repeated tapping by a human hand. It also generated sufficient power output to drive operation of other wearable technologies.

#power #generation #energy #hydrogel #flexible #electronics #biomedical #medical #science #materials

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lokis-mischievous-writer · 5 years ago

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CityU new droplet-based electricity generator: A drop of water lights up 100 small LEDs

A research team led by scientists from City University of Hong Kong (CityU) has recently developed a new form of droplet-based electricity generator (DEG).

It features a field-effect transistor (FET)-like structure that allows for high energy-conversion efficiency, and its instantaneous power density is increased by thousands of times compared to its counterparts without FET-like structure.

This groundbreaking achievement can help to advance scientific research into water energy generation and tackle the energy crisis.

The research was led by Professor Wang Zuankai from CityU’s Department of Mechanical Engineering, Professor Zeng Xiaocheng from the University of Nebraska-Lincoln, and Professor Wang Zhonglin, Founding Director and Chief Scientist at the Beijing Institute of Nanoenergy and Nanosystems of Chinese Academy of Sciences.

Their findings were published in the latest issue of the highly prestigious scientific journal Nature under the tile “A droplet-based electricity generator with high instantaneous power density”.

A conventional droplet energy generator based on the triboelectric effect can generate electricity induced by contact electrification and electrostatic induction when a droplet hits a surface. However, the amount of charge generated on the surface is limited by the interfacial effect, and as a result, the energy conversion efficiency is quite low.

In order to improve the conversion efficiency, the research team has spent two years developing the DEG. Its instantaneous power density can reach up to 50.1 W/m2, thousands of times higher than similar devices without the use of the FET-like design. The energy conversion efficiency is also markedly higher.

Professor Wang pointed out that there are two crucial factors for the invention. First, the team found that the continuous droplets impinging on PTFE, an electret material with a quasi-permanent electric charge, provides a new route for the accumulation and storage of high-density surface charges. They found that when water droplets continuously hit the surface of PTFE, the surface charge generated will accumulate and gradually reach saturation. This new discovery has helped to overcome the bottleneck of the low-charge density encountered in previous work.

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Another key feature is a unique set of structures similar to the FET that won the Nobel Prize in Physics in 1956 and has become the basic building block for modern electronic devices. The device consists of an aluminium electrode and an indium tin oxide (ITO) electrode with a film of PTFE deposited on it. The PTFE/ITO electrode is responsible for the charge generation, storage, and induction. When a falling water droplet hits and spreads on the PTFE/ITO surface, it naturally “bridges” the aluminium electrode and the PTFE/ITO electrode, translating the original system into a closed-loop electric circuit.

With this special design, a high density of surface charge can be accumulated on the PTFE through continuous droplet impinging. Meanwhile, when the spreading water connects the two electrodes, all the stored charges on the PTFE can be fully released for the generation of electric current. As a result, both the instantaneous power density and energy conversion efficiency are much higher.

“Our research shows that a drop of 100 microlitres [1 microlitre = one-millionth litre] of water released from a height of 15 cm can generate a voltage of over 140V, and the power generated can light up 100 small LED lights,” said Professor Wang.

Professor Wang said he hoped that the outcome of this research would help to harvest water energy to respond to the global problem of renewable energy shortage. He believed that in the long run, the new design could be applied and installed on different surfaces, where liquid is in contact with a solid, to fully utilise the low-frequency kinetic energy in water. This can range from the hull surface of a ferry to the surface of umbrellas or even inside water bottles.

https://www.cityu.edu.hk

#ILLUMNI: lighting Design #light art and lighting jobs from around the world

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