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Designing RF-Powered Battery-Less Electronic Shelf Labels With COTS Components

Jarne Van Mulders, Gilles Callebaut

TL;DR

The paper tackles the challenge of designing batteryless electronic shelf labels powered by RF wireless power transfer using commercial components. It presents a dedicated testbed and a complete design flow, selecting a 22 mF leaded aluminum electrolytic capacitor and an AEM40940 harvester to enable energy-neutral operation, with updates achievable in as little as 4 minutes and up to 120 minutes depending on input power and frequency, and harvester efficiencies reaching around 30%. The work details architectural decisions, energy budgeting via a closed-form capacitor sizing equation, and wake-up sequencing to maximize usable energy, while identifying key challenges such as harvester efficiency and update latency that constrain practical deployment. Overall, the study provides concrete design guidelines and experimental evidence toward practical RF-powered ESLs and lays groundwork for energy-neutral IoT devices, with clear paths for future improvements in energy harvesting, storage, and antenna configurations.

Abstract

This paper presents a preliminary study exploring the feasibility of designing batteryless electronic shelf labels (ESLs) powered by radio frequency wireless power transfer using commercial off-the-shelf components. The proposed ESL design is validated through a dedicated testbed and involves a detailed analysis of design choices, including energy consumption, energy conversion, and storage solutions. A leaded aluminium electrolytic capacitor is selected as the primary energy storage element, balancing cost and performance while maintaining compactness. Experimental evaluations demonstrate that an ESL can update its display within 4 to 120 minutes, depending on input power and RF frequency, with harvester efficiencies reaching up to 30 %. Challenges such as low harvester efficiency, extended update times, and hardware constraints are identified, highlighting opportunities for future optimizations. This work provides valuable insights into system design considerations for RF-powered ESLs and establishes a foundation for further research in energy-neutral Internet of Things applications.

Designing RF-Powered Battery-Less Electronic Shelf Labels With COTS Components

TL;DR

The paper tackles the challenge of designing batteryless electronic shelf labels powered by RF wireless power transfer using commercial components. It presents a dedicated testbed and a complete design flow, selecting a 22 mF leaded aluminum electrolytic capacitor and an AEM40940 harvester to enable energy-neutral operation, with updates achievable in as little as 4 minutes and up to 120 minutes depending on input power and frequency, and harvester efficiencies reaching around 30%. The work details architectural decisions, energy budgeting via a closed-form capacitor sizing equation, and wake-up sequencing to maximize usable energy, while identifying key challenges such as harvester efficiency and update latency that constrain practical deployment. Overall, the study provides concrete design guidelines and experimental evidence toward practical RF-powered ESLs and lays groundwork for energy-neutral IoT devices, with clear paths for future improvements in energy harvesting, storage, and antenna configurations.

Abstract

This paper presents a preliminary study exploring the feasibility of designing batteryless electronic shelf labels (ESLs) powered by radio frequency wireless power transfer using commercial off-the-shelf components. The proposed ESL design is validated through a dedicated testbed and involves a detailed analysis of design choices, including energy consumption, energy conversion, and storage solutions. A leaded aluminium electrolytic capacitor is selected as the primary energy storage element, balancing cost and performance while maintaining compactness. Experimental evaluations demonstrate that an ESL can update its display within 4 to 120 minutes, depending on input power and RF frequency, with harvester efficiencies reaching up to 30 %. Challenges such as low harvester efficiency, extended update times, and hardware constraints are identified, highlighting opportunities for future optimizations. This work provides valuable insights into system design considerations for RF-powered ESLs and establishes a foundation for further research in energy-neutral Internet of Things applications.

Paper Structure

This paper contains 14 sections, 1 equation, 5 figures, 1 table.

Table of Contents

  1. Introduction
  2. ESL Requirements and Architecture
  3. System Requirements and Design Constraints
  4. RF Frequency Band Selection
  5. System Hardware Design
  6. ePaper display and Microcontroller
  7. Energy Storage Element and Boost Converter
  8. RF Harvester -- Charging and Triggering Update
  9. Capacitor Technology
  10. Experimental Evaluation and Validation
  11. Charge Time of the Buffer Capacitor
  12. Harvester Charge Efficiency
  13. Techniques to Deliver Energy to ESLs
  14. Conclusion and Future Work

Figures (5)

  • Figure 1: design with the AEM40940 harvester and references to the sections where each component is elaborated.
  • Figure 2: Prototype demonstration of the proposed architecture. The black box in the upper right corner includes two connectors, allowing real-time voltage monitoring of the capacitor.
  • Figure 3: Measured time to charge the buffer capacitor of 22mF to 3.1V with the AEM40940 harvester.
  • Figure 4: Measured efficiency related to the RF input energy and the stored energy in the buffer.
  • Figure 5: Measured harvester efficiency at 868MHz as a function of the capacitor voltage for input power levels of -5 and 10.