Why Batteries Are Ripe for Disruption

Energy-harvesting techniques are maturing and could provide a more sustainable approach to deploying IoT networks.
By Bob Hamlin

The battery-less operation of RFID tags is explanatory of other RF power-harvesting opportunities. There is energy available in the carrier waves that are ultimately modulated for communications signals, and it can be put to use in unexpected ways. Signals like wireless Ethernet, radio and television transmissions, and even the 50Hz or 60Hz from AC power distribution, are virtually everywhere and can be scavenged to energize low-power circuits. This is just the beginning.

Mechanical transducers can convert any type of motion to electrical energy, and micro-electromechanical (MEMS) technology is starting to be applied to this application to provide size, efficiency and price points not previously available. MEMS can be thought of as "moving parts on ASIC chips" and are the basis for harvesting power on single-chip devices. That self-winding watch can now be made on a single chip, without a spring to be wound or a battery to be replaced.

Reliability problems can also be addressed by combining energy harvesting with the latest in energy-storage technology, such as supercapacitors. Consider an IoT deployment to monitor the temperature of items in transit. Modules attached to the assets can use temperature sensors which store data locally and are periodically polled by a reader installed in transport vehicles. Depending on the application, asset data can be moved to the cloud, either during transit or at the end of a run. But how best to power the temperature modules? Mechanical transducers can harvest energy from vehicle vibration, but to keep the module size small and the cost down, it may not be enough to power the sensor and store the resulting energy. Including a supercapacitor enables vibration energy to be collected and stored.

Once enough power has accumulated, the module wakes up and stores a sensor reading, then goes back to sleep. These types of designs address not only the reliability of the battery that is no longer needed, but also the reliability of the power source, which may be intermittent.

So far, only RF and mechanical energy sources have been considered here, but advancements in transducer technology mean IoT edge devices can be powered from sources such as waste heat from machinery, chemical processes including biodegradation, salinity gradients, and internal processes in the human body, just to name a few. As IoT deployments proliferate, it will be critical to address the lifetime and reliability shortcomings of batteries and either replace or augment their usage with approaches based on energy harvesting.

Bob Hamlin is the chief technology officer of Tego, based in Waltham, Mass. Tego develops RFID products and related software used in aerospace and other industries. Hamlin is a senior engineering and product-management executive with more than 20 years' experience and a history of profitable products, including semiconductors for telecommunications and RFID tags.

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