Most green power solutions seek to generate large amounts of electricity to meet demand in the fight against global warming. However, some projects aim to harness more humble renewable energy sources to power sensors and wearables. If we recently talked about nighttime solar power, today it’s the turn of wind power with a wind turbine that works with the slightest breeze. Welcome to the electricity of small things, a world in which the slightest vibration can power a device.
The wind harvester that loved the breeze
The world’s most enormous wind turbines can reach 850 feet in height, and their electrical output is measured in megawatts. The prototype presented by scientists at the Nanyang Technological University (NTU) in Singapore pales in comparison: it is six inches high by eight inches wide and produces two hundred and ninety microwatts. But what’s so special about it?
First, the Singapore prototype can operate in a breeze of just two meters per second. That’s equivalent to a two on the Beaufort scale, the rating that measures wind intensity based on its observable effects. To put it in plain English, that’s the bare minimum to feel a breeze on your face.
Secondly, along the lines of the bladeless wind turbines we discussed some time ago, the Singapore prototype is based on a similar technology. Instead of using a turbine, it relies on the vibration of its materials.
The device comprises low-cost parts made of copper, aluminum, and Teflon, together with an epoxy fiber body. The mechanism converts vibrations into electric current thanks to a long piece of aluminum foil that, like a trampoline, vibrates in the breeze. These vibrations generate an electric charge transmitted from the aluminum foil to the copper foil to generate a triboelectric effect.
The researchers found that the prototype generated enough energy to light forty LED bulbs in laboratory experiments with a four-meter-per-second breeze. This electric current was also enough to power a thermal sensor and send data wirelessly to a cell phone. The device has a rechargeable battery that stores energy when the air is still.
Urban… and countryside applications
The new wind harvester is designed for an era of sensors and IoT devices that, thanks to 5G technology, will be able to multiply exponentially and communicate instantaneously. One of the first applications that NTU scientists have conceived is to power sensors installed on the facade of buildings in environments such as the suburbs of Singapore, where the wind often blows at a speed below 2.5 m/s.
These sensors could measure aspects such as the temperature and health of the structure, air quality, or wind intensity, among other parameters. And not only in cities. Since the device is free of heavy metals or toxic materials, it is ideal for use in sensors installed in forests to warn of the danger of wildfires or other eventualities. When the equipment reaches the end of its useful life, it will not cause harmful effects on forests.
The trillion sensor challenge
In IoT developments, the concept of trillion-sensor systems applies to networks with countless interconnected devices. In ecological and logistical terms, it would be a nightmare if all of them were powered by batteries, as they would need to be recharged or replaced regularly. The key to meeting this challenge is employing technologies that harvest energy for each sensor. And that do so in a renewable way.
In this sense, one of the fundamental breakthroughs is triboelectric nanogenerators (TENG), usually made of organic materials. The first versions of these electrical systems were announced in 2012 and are devices capable of generating energy by transforming vibrations or mechanical pressure into electricity.
One of the latest examples of this technology comes from China. Scientists at Fuzhou University have announced a new version of TENG dubbed CS-TENG, which harnesses wind even at speeds of 2.3 m/s and has demonstrated its ability to power a water quality sensor.
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