How Close are we to Eliminating Batteries in the IoT?

April 17, 2019 David Su, Atmosic Technologies

When the first version of the Wi-Fi® (standard 802.11a) was originally developed and released in 1997, it was intended to provide internet connectivity to and from computers (primarily desktops). The original designers of Wi-Fi may have foreseen applications in laptops and phones, but they likely didn’t expect Wi-Fi to become the essential, ubiquitous connectivity for all kinds of devices—from smartphones to drones—in many different locations worldwide. Consumers quickly began to expect Wi-Fi to be virtually everywhere—the home, public transit, the automobile, work, school, the mall, at concerts and events, and even when they are on vacation. Wireless connectivity has indeed freed us from the data cable, but what about the power cord?

And now with the advent of the Internet of Things (IoT), a multitude of additional wirelessly connected devices are entering the market. In fact, ABI Research predicted that there will be 35+ billion connected IoT devices worldwide by 2023. IoT devices typically fall into six categories: personal, home, automobiles, healthcare, industrial & enterprise, and smart cities.

A great deal of consideration has gone into eliminating the wires for connectivity, but what about the power cord? Even if electrical power cords aren’t required, batteries are—all IoT devices must have power. And with power comes additional costs, not only for power itself (electricity or batteries), but the cost of maintaining or changing batteries. When we’re looking at 35+ billion IoT devices, the costs multiply quickly. We are all guilty of throwing away too many batteries every year.

As an example, what if you were running a large-scale, robotic assembly-line manufacturing facility for children’s toys? You might have the doors, lights, conveyor belts, thermostats, asset trackers, security and robotics, all of which are likely powered by batteries and managed through a central sensor hub. In this scenario, you’d want to minimize any significant amount of time spent maintaining the batteries in all these devices. Imagine you’ve got over a thousand of these battery-powered connected devices in a single manufacturing plant; that’s a massive expense, both in terms of maintenance as well as potential equipment downtime.

Addressing the Challenge on an Unlikely Platform

To solve the battery life challenge, its best to start with a low power connectivity solution with a large deployed base. Bluetooth® technology meets both of these criteria. It has the lowest power consumption of any of the widely deployed wireless connectivity solutions. With the addition of coding gain in the Bluetooth 5 standard, its range has increased by four times (now comparable to Wi-Fi), making it more suitable for IoT connectivity. The battery life of such a Bluetooth 5-connected IoT device can be improved significantly as shown in the graph below.

A bottoms-up redesign of a Bluetooth radio—focused on power reduction—can decrease its power consumption by five to 10 times. The new Bluetooth 5 augmented with lowest power connectivity technologies provides the ideal connectivity for IoT devices. Considering the power usage of just a portion of 35+ billion devices by 2023, a reduction of five-to-10 times equates to massive impact on a global basis.

On-Demand Wake-Up

Another approach to reducing power consumption is keep the IoT device in OFF state unless it is required for operation. This function is analogous to that of a motion-sensor triggered light bulb, turning on only when needed. This On-demand Wake-up feature, which is built into SoCs, essentially works like a second pair of ears that listens for RF signals coming in. The primary transmitter and receiver remain off until the second pair of ears “hears” RF traffic and notifies the primary pair that relevant RF is coming in; then, the primary pair, which performs more functions and therefore requires more power, turns on to complete the transaction. This On-demand Wake-up technique, depending on the applications, can reduce power consumption by up to 100 times relative to other Bluetooth 5 solutions on the market. It works particularly well for applications that are required to be on only occasionally. In those cases, there is no need to utilize power unless RF is being received or transmitted.

Energy Harvesting

Over the past decade, wide deployment of battery-free applications with energy harvesting has only been viable for very short-range applications such as NFC. With the advent of Bluetooth 5, combined with ultra-low-power functionality, power consumption is low enough to be supported by harvested RF, light, or heat energy, while still able to provide the range and coverage equivalent to Wi-Fi. In other words, in many IoT applications for which Bluetooth 5 is best suited, power consumption can be lower than the harvestable energy. This makes the concepts of “forever-battery” and “battery-free” IoT realistic. IoT devices can work for the lifetime of the devices on the batteries they come with, or without batteries at all.

System-Level Optimization

Ultimately the IoT market will continue to demand low-power wireless connectivity. The biggest benefit inherent in combining lower power consumption and energy harvesting technologies is to reduce our dependency on battery power. Along that line, here are a few closing thoughts:

  1. Our battery consumption trajectory is not sustainable. We are getting close to a time when frequent battery change is not viable for IOT growth. We must and will find ways to increase the battery life of connected devices. 
  2. Low power consumption and energy harvesting technologies are ready to significantly improve battery life. With careful design, the concerns about “battery life” can and will become a forgotten issue—something we used to worry about.
  3. Analogous to the transition from incandescent light bulbs to LEDs, consumers must and will demand this change.

I can’t wait for the day when most, if not all, of our connected devices are free from the power cord. We, as consumers, can usher in an IoT world with forever battery life or battery free devices.

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