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    RF Energy Harvesting: Delivering Power to the Next Generation of Smart Building IoT

    Feb. 25, 2025
    Wireless power transmission is revolutionizing smart building IoT by enabling maintenance-free, battery-free sensors and devices. Discover how RF energy harvesting works, its key applications, current limitations, and what’s next for this groundbreaking technology.

    Key Takeaways:

    • Battery dependency in IoT devices increases maintenance costs and risks system failures, while wired alternatives add cost and limit flexibility.
    • RF energy harvesting converts ambient or controlled RF signals into electricity, enabling battery-free, low-power IoT operation.
    • Current applications include environmental sensors, wireless access control, and occupancy/motion detectors in smart buildings.
    • Efficiency limitations mean RF power harvesting currently supports only low-energy devices, requiring further advancements for broader adoption.

    Smart building IoT such as temperature, humidity, motion, water flow, and RFID sensors, and lighting and access control switches often connect wirelessly and rely on batteries for power. This leads to situations where maintenance costs rise, and IoT systems fail when batteries are not replaced in time. Traditional alternatives are to connect these IoT devices to direct power or run network cabling that delivers Power over Ethernet (PoE) for operation. While this addresses battery constraints, it leads to deployment cost increases, scalability issues, and inflexible IoT placements.

    If smart building IoT truly wants to grow, striking a balance between deployment costs and flexibility with low maintenance and reliable IoT device power delivery must be addressed. For more than a century, the concept of wireless power transmission has been discussed as a far-fetched conspiracy dating back to the days of Nickola Tesla. However, technology companies are now on the cusp of being able to transmit sufficient electricity to low-power IoT devices and sensors using RF energy harvesting technologies.

    Let’s take a look at the current state of this technology, use cases, existing limitations, and its future potential.

    How Does RF Energy Harvesting Work?

    Using specialized hardware to capture, convert, and even store harvested power, IoT devices and sensors can collect radio frequencies that pass by, turning it into electricity. Depending on the amount of power needed, two different wireless power output solutions can be used:

    Ambient RF: This method takes existing RF signals that are being transmitted in an area for power conversion. A common RF source used today is Wi-Fi signals that are transmitted on the 2.4, 5 and 6GHz wireless spectrum.

    Controlled RF: Wireless power transmission base stations can be deployed to deliberately transmit signals that are collected and converted into wireless power by IoT devices.

    In both cases, the end result is allowing IoT devices to operate without batteries or wired connections, enabling continuous, maintenance-free power for low-energy IoT applications.

    Prevailing RF Energy Harvesting Smart Building Use Cases

    While still in its infancy, RF energy harvesting is already being deployed within smart buildings. The most popular use cases include:

    • Environmental Sensors—Temperature, humidity, and air quality sensors do not require much power to operate. Thus, RF harvesting chips are being built into these sensors, commonly relying on Wi-Fi signals for power consumption.
    • Access Control—For situations where door controllers are frequently moved, requiring wireless deployment flexibility, modern door controllers are now being installed with RF harvesting hardware as an alternative to batteries.
    • Occupancy & Motion Detectors—To help with smart lighting, automated HVAC control, and physical security needs, occupancy and motion sensors can now be deployed with wireless power delivery technologies.

    Overcoming Existing RF Power Harvesting Limitations

    The biggest limitation of current RF Power Harvesting technologies today revolves around efficiency and IoT device power draw. Reported efficiencies for converting ambient RF signal to electricity currently sit between 10% and 50%. Controlled power, on the other hand, has been shown to exceed 70% efficiency. Keep in mind, however, that controlled power delivery requires added hardware and is limited to regulated transmission standards.

    From a power draw and conversion to electricity perspective, RF power harvesting is currently limited to IoT sensors and devices requiring very low amounts of electricity. Thus, in order for more real-world use cases to emerge, IoT devices must either become far more efficient, or the efficiency rates that convert RF signals to electricity must increase. It is likely that it will be a combination of the two before this technology can become more mainstream.

    The Future of RF Power Harvesting is Bright

    With improved circuitry, multi-band capabilities, and continued commercialization by technology vendors, including Qualcomm and Texas Instruments, the future of RF power harvesting looks promising. With ongoing R&D thanks to increased industry investment, this technology is set to reshape smart buildings, industrial automation, and more, delivering the deployment flexibility and maintenance that’s needed for smart building IoT to truly take off.

     

    Next Steps for Building Professionals

    • Assess current IoT infrastructure. Identify battery-dependent devices that could benefit from RF energy harvesting to reduce maintenance costs.

    • Stay informed on industry developments. Track advancements in RF energy harvesting and potential vendors offering reliable solutions.

    • Pilot test RF harvesting solutions. Experiment with environmental sensors, occupancy detectors, and access control devices to evaluate real-world performance.

    • Engage with technology providers. Work with IoT manufacturers and RF power harvesting developers to understand implementation feasibility.

    • Plan for long-term integration. As technology matures, strategize how to incorporate wireless power into future smart building upgrades for greater cost efficiency and sustainability.

    About the Author

    Andrew Froehlich | Contributor

    As a highly regarded network architect and trusted IT consultant with worldwide contacts, Andrew Froehlich counts over two decades of experience and possesses multiple industry certifications in the field of enterprise networking. Andrew is the founder and president of Colorado-based West Gate Networks, which specializes in enterprise network architectures and data center build-outs. He’s also the founder of an enterprise IT research and analysis firm, InfraMomentum. As the author of two Cisco certification study guides published by Sybex, he is a regular contributor to multiple enterprise IT-related websites and trade journals with insights into rapidly changing developments in the IT industry.

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