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Powering the Internet of Things: New Technologies for New Markets
guably the most disruptive shift in In- ternet technology since the origination of the Internet itself. The IoT repre- sents a complex universe spanning communications, identification, loca- tion tracking, and security, enabled by multitudes of electronic equipment and electronic devices and sensors. A number of technological advances are driving the IoT, with the embedded chips that work as the brains of IoT products becoming more sophisticated and less expensive, along with more reliable communications capabilities. In addition, the growth of the cloud is increasing storage capabilities for data and applications. As the IoT expands, opportunities also expand for manu- facturers of power source devices to make it all run. Conventional batteries will not
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work in the future IoT because of the various requirements for emerging IoT devices, including their many different shapes and sizes, their low-power re- quirements, their high wireless fre-
he Internet-of-Things (IoT), a proliferation of interconnected sensors and processors, is ar-
quencies and operating distances, and their needs to be increasingly intercon- nected. The power sources for these IoT products will require some key fea- tures of their own, including small sizes and flexible shapes, wireless con- nectivity, the capability to draw from different available energy resources for recharging, self-charging capabili- ties to extend to the operating life- times of the main circuitry, and envi- ronmentally friendly, in order to co-ex- ist with other wireless and IoT devices in the same environment. As an example, the energy densi-
ty of the lithium-ion battery in an iPhone 5 cellular telephone from Apple is 142mAh/cm3, or 63 percent higher in capacity than conventional Li-ion batteries from nine years ago. This jump in capacity has far outpaced the approximate 5 percent/ year energy density growth rate for standard Li- ion batteries. For all IoT devices, smartphones
and beyond, the future power source re- quirements, such as rigid use (cycle life, specific energy, and power), high toler- ance capacity, and flexibility (including
wearability), don’t bode well for present bulky conventional batteries.
IoT Power Source Alternatives In most cases, conventional bat-
teries won’t meet IoT power-source re- quirements and other energy sources will be needed. As an example, induc- tive power supplies involve wirelessly transferring energy from one device (a transmitter or charging station) to an- other (a receiver or portable device). Wireless charging was introduced for smartphones and plays a strong role for this utility, with nearly all smart- phones and tablet computers support- ing wireless charging. Other inductive power applications include transcuta- neous energy transfer systems in sur- gically implanted devices (e.g., artifi- cial hearts) and environment-monitor- ing robots. Inductive coupling is typically
used to power RFID tags; IoT and RFID have common origins and exten- sive overlap. Such “passive” battery- free RFID sensor tags have an “on-de- mand” reliable source of energy, with no dependence on environmental con- ditions for the sensor to transmit data. They can be embedded in concrete (e.g., in walls and pillars), inside piping sys- tems, sealed within enclosures, and at many relatively inaccessible locations, so it is important for these applications to never require battery-change main- tenance. As the numbers of wirelessly con-
nected IoT devices grows, the technol- ogy to power them will likely evolve from inductive coupling to resonant charging, and from charging one de- vice at a time to charging multiple de- vices concurrently. Such an approach could support a myriad of IoT applica- tions, from smartphones to smart cars. Thin-film batteries are being con-
sidered as replacements for conven- tional batteries in a number of differ- ent IoT applications, including in smartphones, sensors, RFID tags, and smart cards and labels (including “smart” packaging for food and medi- cine). But this technology is still some- what further from commercial deploy- ment for IoT applications, including electronic shelf labels and “smart shelves,” and efforts are being made to bring these products to market. The three-dimensional (3D) printing of bat- teries offers the intriguing promise of batteries as small as grains of sand, along with the combination of battery thin-film material layers and coatings with textile materials.
Energy Harvesting Another source of energy for IoT
devices will be by means of energy har- vesting. This encompasses several technologies to facilitate ambient ener- gy conversion and storage: PV solar cells, piezoelectric, thermoelectric, py- roelectric, geomagnetic, electrostatic, and microwave conversion. The differ- ent natures of these ambient energy sources also means that IoT wireless sensor nodes will require microbatter-
ies as backup energy sources, capable of being re charged once a wireless node has harvested enough ambient energy. For these different battery-
recharging approaches to be effective for IoT products, a number of hurdles must be overcome. For one thing, the power efficiency must improve. The current technology for inductive and energy harvesting falls short of con- ventional wired charging techniques in terms of power transfer efficiency, roughly about 70 percent for inductive charging compared to 85 percent for wired charging. The difference trans- lates into slower charging times or tradeoffs in size and cost between de- vices using the two methods. The range of current wireless recharging approaches (inductive/resonant cou- pling or energy harvesting) is also lim- ited, and must cover at least an entire room, and eventually a house, to be ef- fective. The choice of wireless charging
frequency must be compatible with oth- er wireless standards and comply with electromagnetic-interference (EMI) and electromagnetic-compatibility (EMC) requirements. This compliance must al- so meld with the many different wire- less communications technologies wo- ven together as part of the IoT. Any wireless charging standard must be compatible with these many other wire- less standards within IoT applications, such as Bluetooth, Wi-Fi, and ZigBee. A solution may lie in integrating all of them into a single wireless standard, which will also solve security issues.
Cost Factors Cost will be an important con-
tributor to the success of any wireless charging solution. Many products within the IoT are small and low in cost, and the power sources must fol- low. Conventional chargers are gener- ally provided with products at no extra cost, but wireless chargers are usually included at an additional cost. For more widespread acceptance, especial- ly as the IoT expands, wireless charg- ers must be developed with better effi- ciencies and at lower costs. The IoT power-source technolo-
gies such as thin-film and printed bat- teries, energy harvesting modules, small flexible solar photovoltaic pan- els, and thermoelectric sources, have enjoyed niche successes and marginal revenues to this point, but the emer- gence of the IoT should pave the way for these products potentially generat- ing hundreds of millions of dollars in annual revenues. Thin-film and print- ed batteries make up the vast majority of the current total $57.1 million mar- ket for IoT power sources, with most of that for mobile telephones. But many other IoT products, including smart cards, semiconductor/computing, and wearable electronics, are expected to grow into hundred-million-dollar bat- tery markets by the end of this decade. Beyond batteries, NanoMarkets
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December, 2014
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