How to Stop Disposable Batteries and Foster the Energy-Harvesting Era

Article By : Geoffroy Gosset

How do we deal with the toxic waste in batteries? The solution is energy harvesting from ambient sources.

The first battery was invented back in 1800. More than 200 years later, we still use non-rechargeable batteries, even though they have negative practical and environmental implications. Those drawbacks could soon be a thing of the past as society shifts toward more sustainable and efficient ways to obtain energy for low-power devices. Such a shift would make our life easier, as there would be no need to change batteries. Industries would particularly benefit, as the cost of changing batteries on an industrial scale can be quite high.

Here are just a few downsides to using disposable batteries:
• They take up a lot of space in devices. If devices were without batteries, they could be made smaller. Alternatively, that freed space could be utilized for additional features.
• They run out of energy at the most inconvenient times.
• It takes time and financial means to replace batteries, which is especially complicated and costly for large industries in which thousands or more batteries need to be replaced.
• They can cause data loss in smart devices such as trackers, sensors, and monitoring devices.
• Batteries that contain heavy metals pollute the environment if not properly disposed of.

The number of IoT devices worldwide is growing rapidly, and so is the volume of batteries needed to support this growth. With an expected 78 million batteries to be discarded daily by 2025 and 100 billion wasted AA batteries in 2050 (equivalent to 300 Olympic-sized swimming pools), there is clearly a growing environmental problem for which IoT companies must take responsibility. But how do we deal with such an immense amount of toxic waste?

How to Stop Disposable Batteries and Foster the Energy-Harvesting Era
(Source: e-peas)

The solution is energy harvesting from ambient sources.

There is a lot of energy surrounding the devices we use: solar, thermal, vibration, and radio frequency (RF), among others. This energy can be used to charge low-power devices such as TV remotes, wireless headphones, fire alarms, watches, electronic shelf labels, animal and asset trackers, thermostats, smart switches, and scales, just to name a few.

All these devices can charge from different energy sources in their vicinity.

Depending on the available energy source, a device will require integration of an energy harvester such as a PV cell, thermoelectric generator, piezo material, electromagnetic transducer, or antenna.

One more necessary component is a power management unit, which optimizes the energy transfer to the storage element (rechargeable battery, supercapacitor, etc.) and supplies the power system (the application). Such a solution provides continuous power for years and solves the bottleneck of replacing batteries.

To see how this works, let’s consider a smartwatch, which can recharge from indoor and/or outdoor light. Three major elements are needed for this technology to work in a smartwatch platform:

  1. An energy harvester (in this case, a PV cell) for absorbing light and converting it into energy
  2. An integrated circuit for efficiently transferring the PV cell energy into a storage element
  3. A storage element for storing the collected energy, typically a Li-ion or Li-polymer battery, already present in standard smartwatches

Once all three components are integrated into a device, its battery lifetime can be sensibly extended, or in best cases, it can even run for many years without the need of replacing a battery or putting it on a charging station. To work properly in such an application, the power management IC must be able to allow for charging the watch battery both in very dim indoor environments and in bright outdoor light, adapting dynamically and automatically (ideally several times per second) the amount of power it extracts from the PV cell. This is primordial in the case of moving objects.

Another good example of energy harvesting is wirelessly charging electronic shelf labels (ESLs), which are used mainly in retail. Such labels can be charged from RF waves using a dedicated emitter placed on a ceiling or a wall. The dedicated emitter transmits RF power to the ESL and typically emits from 100 mW up to a few watts. The ESL integrates one or more antennas, a matching circuit, a rectifier, and a dedicated power management IC that uses the received power to charge the storage element. Depending on the distance between the emitter and the receiving antenna, the typical received power ranges from a few tens of milliwatts down to a few microwatts.

The advantage of using RF energy harvesting in this application is the ease of integration: No modification of the device external shell is required, as would be the case for photovoltaic energy harvesting, which requires the integration of a PV cell.

Like the shift to fully electric vehicles, the adoption of energy-harvesting technology requires redevelopment of devices. But the transition is inevitable, as energy harvesting will not only allow us to enjoy devices that don’t run out of energy but will also have a positive impact on the environment.


>> e-peas was featured as one of EE Times top 100 emerging startups to watch, now in its 21st edition. 

The Silicon 100 is a list of electronics and semiconductor startups that grabbed our attention during the preceding year. 

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