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Energy harvested from body, environment could power wearables, IOT devices

Agam Shah | Aug. 11, 2014
Energy harvesting technologies will work for really low-power wearables, not power-hungry smartwatches.

Low-power wearables may soon bid adieu to batteries and start drawing energy generated by body heat and movement, and ambient energy from the environment.

Consumer electronics devices are getting smaller but conventional batteries are not, and it's important to start implementing new energy harvesting techniques to keep devices powered for long periods of time, researchers said at the Hot Chips conference in Cupertino, California, on Sunday.

Energy harvested from body heat, motion and ambient light could be used in medical implants, monitoring sensors and disposable medical patches, said Yogesh Ramadass, lead design engineer at Texas Instruments, during a presentation at the Hot Chips conference.

The technologies are still emerging, but the chip performance and energy efficiency of some wearables are reaching a point where it has started becoming "convenient for us to replace the battery and replace it with ambient energy," Ramadass said.

Energy harvested from the body and environment is in the microwatt range, so it can't be used for smartwatches or fitness trackers, which draw milliwatts of energy, Ramadass said.

"You shouldn't be thinking about a regular wearable devices like FitBit, smartwatch or others," Ramadass said in an interview on the sidelines of the show.

Smartwatches have displays and software that can drain batteries, while energy harvesters are better for wearables that collect and transmit bits of data at specific intervals.

Self-powered devices could make an impact in the context of the Internet of Things, said Massimo Alioto, associate professor at the National University of Singapore.

There will be billions of Internet-connected devices supplying real-time information in the coming year. Data-gathering instruments today are designed around the size of batteries, and self-powered devices could resolve some power and size issues, Alioto said.

The researchers said that energy harvesting technologies could be relevant in smoke detectors, alarm sensors, smart meters and even remote controls.

There will be 26 billion Internet-connected devices by 2020, according to Gartner. Sensors will be used in wearables, industrial equipment, energy monitors, telematics systems, home appliances and other "intelligent" appliances, Gartner said. Another research firm, PricewaterhouseCoopers, is predicting IOT to become a multitrillion dollar industry by 2020.

The energy efficiency of circuitry plays a major role in determining the size, weight and operating time of self-powered IOT devices, TI's Ramadass said.

"Typically in indoor or wearable situations we're talking about few tens of microwatts, in an industrial situation or sunlight we're talking about few milliwatts per centimeter square or cube... depending on what the harvester is," Ramadass said.

One energy harvesting technology is solar energy, which is already used in calculators and other devices, but could also be used in data-gathering instruments that transmit information wirelessly. The average power generated through indoor lighting would be few tens of microwatts, while sunlight would generate milliwatts of power. Research is ongoing to improve the efficiency of energy generation, Ramadass said.

 

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