A New Wave of Energy Harvesting Ultra-Low-Power Devices May Disrupt RTLS and Outdoor Tracking, but Challenges Remain

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2Q 2019 | IN-5418

Across various verticals, and especially within energy constrained Internet of Things (IoT) applications, the industry has struggled with the problem of finite battery lifetime in devices that sense, locate, read, or control systems when they cannot be connected to a power source. As these devices are often numerous or placed in remote or dangerous locations, substituting their batteries frequently may not be an option, thus posing a challenge to IoT deployment. Nonetheless, the considerable progress made in the past decade to improve the power consumption of Integrated Circuits (ICs) means modern IoT chipsets can now meet the requirements of ultra-low-power IoT applications, such as simple sensing or low power transmission. With such low-energy consumption, these chipsets could be easily powered by harvesting energy from surrounding sources.

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The Dream of Infinite Battery

NEWS


Across various verticals, and especially within energy constrained Internet of Things (IoT) applications, the industry has struggled with the problem of finite battery lifetime in devices that sense, locate, read, or control systems when they cannot be connected to a power source. As these devices are often numerous or placed in remote or dangerous locations, substituting their batteries frequently may not be an option, thus posing a challenge to IoT deployment. Nonetheless, the considerable progress made in the past decade to improve the power consumption of Integrated Circuits (ICs) means modern IoT chipsets can now meet the requirements of ultra-low-power IoT applications, such as simple sensing or low power transmission. With such low-energy consumption, these chipsets could be easily powered by harvesting energy from surrounding sources.

Energy Harvesting Can Be a Driver for Scalability in RTLS

IMPACT


Usable energy can be found almost everywhere in the form of light, temperature differences, salinity differences, radiofrequency (RF), and vibration, to name a few instances. What has prevented energy harvesting from being used ubiquitously is its generally very low energy output efficiency, and ability to store the harvested energy. For example, a photovoltaic cell can harvest about 10µW per cm2 when indoors (see Figure 1). In the past, this energy output would not have been enough to power much more than a basic office calculator, let alone provide RF connectivity and location. However, the past decade has seen many breakthroughs in IC energy consumption, and renewed interest in energy harvesting means that many devices are becoming efficient enough to not need charging or any batteries at all.

  ABI Research  

With new developments in chipset design seeping into the IoT, we now begin to see a new generation of ultra-low-power devices targeting location applications. The batteries in these ultra-low-power devices can last for several years unaided, for instance in low-power GNSS (LP-GNSS) devices. These devices can leverage GNSS location information while consuming much less energy than is usually associated with the technology. Energy harvesting is an ideal target for LP-GNSS applications. For instance, in February 2019, u-blox announced a partnership with TransSiP and Matrix Industries to implement its low-power ZOE-M8B GNSS receiver into the PowerWatch 2. This smartwatch does not need to be charged as it harvests thermal energy released from the human body, as well as solar energy, to top up its internal battery.

However, for applications involving indoors tracking, like Real-Time Locating Systems (RTLS), solar energy harvesting is of little help. To counter this problem, a few innovative companies are finding new ways to harvest enough RF energy from surrounding Bluetooth, Wi-Fi, cellular, and Ultra-Wideband (UWB) waves. This form of energy harvesting is allowing them to release the first ever battery-free (passive) asset tracking tags for RTLS. For example, the recent partnership announced between ultra-low-power Bluetooth Low Energy (BLE) vendor Atmosic and Kontakt.io aims to bring this reality to BLE tags. Atmosic’s M3 Series chipsets can keep one radio receiver in a sleeping state, only to be woken up when alerted of an incoming message by its partner receiver, which is kept at a minimum listening state. Combined with what Atmosic calls Controlled Energy Harvesting, these devices can have an indefinite battery life. Wiliot has also come forward with passive BLE tags capable of temperature and pressure sensing. Furthermore, it can harvest energy from Bluetooth, Wi-Fi, or cellular RF waves. These tags work by accumulating the energy harvested until they have enough to send out a signal that allows nearby devices to locate them.

Within the UWB radio space, UWINLOC use a similar technique. The company sells passive UWB tags that harvest energy from UWB waves. In UWINLOC’s solution, the establishments deploy anchor points in the venue that flood the area with UWB RF. Then, UWINLOC’s tags harvest and accumulate this energy until they have enough to send out a signal. Passive tags like Wiliot’s, Atmosic’s, and UWINLOC’s are usually much cheaper than their active counterparts. This is because they are simpler and do not contain bulky batteries or expensive sensors like accelerometers or magnetometers. For comparison, Wiliot’s passive BLE tag is expected to reach the market at a sub-dollar price point, whereas the cheapest active BLE tags tend to retail around US$5. Equally, while active UWB tags could be as expensive as US$20, right now the price of their passive counterparts could go below US$3 mark if shipped in large volumes.

Therefore, using the passive tags made possible by energy harvesting for RTLS can potentially bring the CAPEX of such implementations down. Such a cost reduction constitutes an improvement in the scalability of RTLS implementations. Also, because passive tags do not suffer from battery depletion, their lifespans tend to be longer than those of active ones. Hence, they can reduce the maintenance costs involved in recharging or replacing the tag infrastructure. As a result, the OPEXassociated with such deployments is reduced and the ROI improved. Therefore, passive tags enabled by energy harvesting will likely claim a sizeable segment of the market that currently belongs to active tags.

Energy Harvesting in IoT Is Here to Stay, but It Is No Miracle

RECOMMENDATIONS


There is no doubt the addressable market for location tags based on energy harvesting is wide and diverse, ranging from tags addressing LP-GNSS applications to those addressing passive tags for asset tracking applications. ABI Research’s RTLS market data tracker (MD-RTLS-102) predicts that by 2025 tag shipments for RTLS purposes will reach almost 600 million units, whereas ABI Research’s MD-OSC-102 predicts 575 million location/tracking LP-GNSS connections by 2023. If energy harvesting location tags can grasp only 10% of the RTLS base, total shipments of these devices could generate US$800 million in revenues in 2025.

As one would expect, the greatest obstacles for energy harvesting devices have to do with power consumption. Beyond basic parameters, like temperature and pressure, sensors like magnetometers, barometers, and hygrometers are too power consuming to be supported by energy harvesting solutions for now. Thus, energy limitations pose a barrier in applications that require tracking and monitoring, like the tracking of products that need to be kept at specific humidity levels. Another obstacle is form factor. The capacity of any energy harvesting solution is proportional to the surface area of its harvesting engine, or “harvester.” Tag manufacturers cannot simply increase tag sizes to accommodate bigger harvesters to gather enough energy for sensing. Enlarging RTLS tags would render most of them unfit for their purpose, as in many applications they benefit from being small and, most importantly, cheap. Furthermore, companies venturing into battery-free RTLS must make sure to enable long enough communication ranges, as opposed to chokepoint tracking. Otherwise, they could face strong competition from passive RFID tags, which are offered at very competitive prices but are not able to support long-range tracking.

In conclusion, despite the considerable progress being made in energy harvesting technologies, businesses need to keep the scales in Figure 1 in mind. These technologies can convert only very little energy so far, which means that power-intensive devices like Access Points will not be able to run on environmental energy alone until the efficiency of such energy conversion 

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