3 billion IoT devices have the potential to be powered by RF energy harvesting in 2030

Transforma Insights recently published a report ‘The potential for energy harvesting powering IoT devices’ that includes forecasts of the number of IoT devices that can potentially make use of four major energy harvesting sources – Solar, Kinetic, Thermal and Radio Frequency (RF) – and so can potentially operate without batteries or access to an external power source. One of the most interesting and quickly developing energy harvesting sources is RF. This blog post touches upon what RF harvesting means, what the potential for RF energy harvesting in IoT is and which IoT applications are suitable for RF energy harvesting.

What is RF energy harvesting?

The harvesting and conversion of ambient electromagnetic radio waves present from Wi-Fi, radio transmitters, GSM cellular stations, and other ambient sources into electrical energy is known as radio frequency (RF) energy harvesting. A core component enabling this technology is a ‘rectenna’ - an antenna on the device to collect ambient RF signals and a rectifier to convert radio signals into usable direct current (DC) power. As ambient RF energy is often not intense enough to be a reliable source of power, dedicated RF sources often need to be placed in a devices local environment to beam RF power to wireless RF harvesting nodes, a concept called ‘Controlled Harvesting’.

Which IoT applications can make use of RF energy harvesting?

RF energy harvesting provides low power at distances ranging from a few centimetres to a few meters. Since harvested energy is extremely small (μW to low-mW), only ultra-low-powered IoT devices or simple data transmitting tags are suitable applications for this technique of energy harvesting. This might include devices that are in sleep mode most of the time, transmit small data packets at infrequent intervals, have very simple sensors, and use low power communications technologies such as Zigbee or Bluetooth. Therefore, it is ideal for devices like electronic shelf labels and IoT sensors that monitor indoor temperature, humidity, and air quality, or other devices that need the broadest spatial freedom.

The graphic below highlights the IoT Applications that form the sweet spot for RF energy harvesting, with forecasts for the number of connected devices for each application in 2030 drawn from Transforma Insights IoT TAM Forecasts. As shown, Electronic Shelf Labels (ESLs), Indoor Air Quality Monitoring devices, Beacons, Trigger Devices, Loss Prevention – Goods Location Monitoring, Supply Chain Monitoring, and Stock Level Monitoring have high potential to use RF energy harvesting. Broadly, it is suitable for the following applications:

• Supply chain tracking – Tracking packages, pallets, containers, and roller cages and monitoring condition (temperature & humidity) of goods, especially perishables for location monitoring, theft prevention and waste prevention. This is where most of today’s commercial deployment happening. To give an example, Walmart’s is using Wiliot’s IoT Pixels to track pallets at scale, with a goal of reaching 90 million by the end of 2026. Another successful implementation is the deployment of Wiliot’s IoT Pixels by the UK’s Royal Mail to track more than 900,000 rolling cages.
• Inventory management – Retail items tracking (for example clothing, consumer goods, and more) and shelf labels, for asset tracking, theft prevention and stock management.
• Environmental monitoring – Low-power devices that monitor temperature, humidity and other environmental metrics in buildings, warehouses, retail stores and other locations.
• Beacons - Small wireless Bluetooth devices that transmit a signal to nearby Bluetooth devices such as smartphones for applications such as retail advertising. These devices usually run on very low levels of power consumption and only transmit data briefly but if the application involves frequent advertising or continuous sensing, RF energy harvesting can be challenging.

The RF Energy harvesting opportunity in IoT

Transforma Insights forecasts that the number of IoT connected devices that have the potential to be powered by RF energy harvesting by the end of 2030 will be 3 billion, around one-tenth of total IoT connected devices in 2030. The opportunity is dominated by Inventory Management and Monitoring (predominantly, ESLs and stock level monitoring), which will account for over 59% of the total potential with 1.72 billion connected devices. Inventory Management & Monitoring is followed by Building Automation and Track & Trace which will account for 15% and 10% of the total market potential, respectively. Building automation is comprised of simple sensors – such as door, window and occupancy sensors that detect motion or contact and are activated by specific events and Track & Trace includes devices used for location monitoring, theft monitoring and supply chain asset monitoring.

Challenges associated with RF energy harvesting

Despite the potential, RF energy harvesting faces challenges such as often low ambient RF power density, limited efficiency of power conversion, and fluctuations in signal strength.

• Low power density: The amount of RF energy present in ambient electromagnetic radiation is very limited and can often require large antenna surfaces, which might not be practical for the majority of IoT applications. Placement of dedicated RF transmitters might solve this problem to some extent but still RF energy harvesting will be suitable only for the lowest-power sensors or beacons.
• Limited efficiency of power conversion: The usable DC power obtained from weak RF signals is usually very low and so unable to support IoT applications other than very simple devices that transmit data infrequently.
• Intermittent availability: The reliability of ambient energy will always be a challenge considering RF fluctuations and intermittent availability, unless dedicated local transmitters are installed.

In conclusion

RF energy harvesting is already enabling a select set of IoT applications to run without batteries and has the potential to power up to 3 billion IoT devices in 2030. Ambient RF energy from Wi-Fi, Bluetooth and cellular networks can power sensors used for supply chain tracking, asset tracking, inventory management, and environmental monitoring. But there are significant challenges associated with the technology and significant advances in components are needed to deliver on the potential for RF energy harvesting.