Powering Bluetooth Sensor Beacons via Micro-Energy Harvesting

Recent research A Comprehensive Study on the Internet of Things (IoT) and Micro-Energy Harvesting from Ambient Sources, from researchers in Spain, discusses the potential of micro-energy harvesting (MEH) as a sustainable power source for Internet of Things (IoT) devices, specifically Bluetooth sensors.

Micro-Energy Harvesting (MEH) is a technology that captures and converts small amounts of environmental energy such as like light, heat, or motion into electrical energy, which can power small electronic devices. The study suggests that MEH could be a sustainable solution for powering Internet of Things (IoT) devices, including Bluetooth sensors, due to their low power requirements.

The benefits of MEH include reducing the need for costly and environmentally harmful battery replacements and enabling the deployment of IoT devices in remote or hard-to-reach areas. The study also points out challenges, such as the small and variable amount of energy that can be harvested, which may not provide a reliable power supply for devices that need a steady source of energy. However, even with small temperature gradients between the environment and the cold side of the thermoelectric generator, it wass possible to make several communications per hour.

Sensor Beacons

Solar iBeacons

We previously supplied solar beacons. These are beacons with a rechargeable battery topped up via a solar cell.

Solar iBeacon
Solar Beacon

Solar beacon’s weren’t popular and all the models we supplied are no longer manufactured. Some specialist solar beacon companies, whose models we didn’t supply, have also stopped selling beacons. So what happened?

Solar beacons seemed attractive in that they offered the prospect of not needing to change batteries. They weren’t that much more expensive so price wasn’t the reason for poor takeup. Instead, we believe these were the reasons:

  • Solar beacons were always the dumbest of beacons. The features in advanced beacons, such as sensors and advanced settings, never made their way to solar beacons. If you needed these features then the solar beacon wasn’t suitable.
  • While you didn’t need to change the battery because it was flat, the rechargeable battery still had an inherent lifetime of about 10 years. Given that some beacons’ batteries can last up to 5 years, the solar advantage wasn’t that great. Replacement batteries also cost considerably more than non-rechargeable.
  • Solar beacons with glass solar cells were much more fragile causing them to be more likely to be damaged in transit and use. The solar cell also needed to be kept clean which was a problem in some situations.
  • The rechargeable batteries in beacons tended to be LIR2032. Lithium rechargeable batteries suffer from non-use and once flat cannot be used. Beacons in storage required their batteries to be replaced.

In summary, solar beacons have too many problems that, on balance, outweighed what was a less than expected increase in battery life. For next generation self-powered beacons look to Wiliot who power beacons via energy harvesting. Instead of batteries, they use supercapacitors but even these have limited life.

New Wafer Thin Nordic nRF51 SoC

Nordic, the manufacturer of the System on a Chip (SoC) found in most beacons has announced that an ultra thin version will be available from American Semiconductor.

The AS_NRF51 Flex-BLE (pdf) is an ultra-thin version of Nordic’s nRF51822 SoC wafer-level CSP (WL-CSP), employing American Semiconductor’s ‘FleX™ Semiconductor-on-Polymer™’ (FleX SoP) process to reduce package size to approximately 35µm—roughly half the thickness of a human hair.

The largest component of beacons and Bluetooth sensors is usually the battery rather than the SoC. However, the Flex-BLE version will be especially suited to energy harvested and solar solutions where it will be possible to create very thin beacons that can be invisibly manufactured into products or their packaging.

Wiliot To Enable New Beacon Usecases

We mentioned Wiliot last March and since then their R&D team has created early engineering samples that prove it’s possible to create a battery-less Bluetooth LE beacon harvesting energy from radio frequencies (RF).

The Wiliot device looks more like a RFID tag than a traditional beacon in that it’s supplied as a very thin PVC inlay sheet containing the chip and wire antenna together. The thin form factor, no battery and the relatively low cost will allow it to be manufactured into or stuck onto clothing and packaging that will provide for many new usecases.

Producing such a device isn’t easy as it can’t use existing System On a Chip (SoC) devices as produced by Nordic, Dialog and Texas Instruments (TI) because they are too large and use too much power. Wiliot has had to create their own SoC from the ground up, including software tools to develop and program the devices. We have been told it will be a year before Wilot has all the components in place for commercial rollout. Meanwhile, selected organisations can join the Early Advantage Program (EAP). There’s a new a product overview (PDF below) that explains the EAP and the main usecases, connected packaging, connected apparel, logistics and asset tracking:

Wiliot already have Early Advantage Program (EAP) agreements in place with over a dozen brands including top fashion brands, a telco, appliance companies, a furniture brand and packaging companies.