With millions of sensors, beacons, trackers, nodes, and devices, the Internet of Things (IoT) is expanding into every nook and cranny of the modern world.
What do all these devices have in common?
They are all powered from some form of the storage element. Whether it’s a battery, capacitor, fuel cell, or wind up watch, all devices need something that can store and provide stable, predictable power.
Primary batteries, rechargeable batteries, and capacitors are the most common storage elements used in IoT systems, and they can be paired with solar energy harvesting to enhance a device's power performance.
Each storage method has benefits and drawbacks, which make them suitable for different applications.
Primary batteries have a fixed amount of energy and cannot be recharged. AA alkaline and 3V Lithium coin cells are two examples of prevalent primary batteries used in IoT devices.
Primary batteries are relatively inexpensive, have a long shelf life, and easily integrate into a product’s circuitry. Of course, the downside of primary batteries is that they typically only last a year or two before dying and needing to be replaced.
Although pairing solar power with a primary battery may seem counterintuitive, they can actually work together to increase battery life, sometimes indefinitely.
The key is to set up your system to run using solar power when light is available and fall back on the primary battery when it's not. You can also use capacitors to provide an additional buffer, allowing the system to run on solar power longer without light.
This is a great option if you already have a finished product with a primary battery and are looking to extend battery life with solar.
Rechargeable (Secondary) Batteries
As the name implies, the most significant benefit of secondary batteries is the ability to recharge them. They are inherently a good fit for solar harvesting, which can provide that charging power.
Li-ion, Li-Polymer, and other Lithium chemistries are by far the most popular rechargeable battery used in modern electronics, due to their high power density and cycle life. Other rechargeable batteries include Lead-Acid, NiMH, NiCad, and Solid State.
When using rechargeable batteries, it's important to charge them properly. Luckily, there are many off the shelf charge controllers and development kits which handle the solar input, battery charging, and may provide other features, like regulated voltage outputs.
Rechargeable batteries are generally an excellent choice for any IoT device. As long as the system, on average, collects more energy than it consumes, the batteries will maintain charge.
Advances in low power electronics have enabled many devices to operate without a battery, instead of using capacitors or super-capacitors.
Think of a capacitor as a tiny rechargeable battery with thousands of times less storage capacity than traditional batteries. They can be charged up quickly, but also discharged quickly when solar power is removed.
The most significant advantage of a capacitor-based system is not having a battery, which is very beneficial for many applications.
The downside is devices are unable to operate for long periods without light. Systems with standard surface mount capacitors run for several minutes without light, while systems with large super-capacitors operate for several days.
Using capacitors as storage elements is a great solution for low power applications that only need to operate when light is available. Retail spaces are a great example of an application that could greatly benefit from IoT systems, which only need to perform during the day when customers are shopping, and lights are on.
Benefits of Solar For IoT Systems
No matter what storage element your system uses, it can benefit from a solar solution. Although there are many benefits, here are the top three.
Extends the Battery Life of Your Device.
Many devices suffer from short battery life. Solar power can be used to extend that lifetime significantly, in some cases doubling, tripling, or extending lifetime indefinitely. Longer battery life means less system maintenance, end cost, and increased convenience for system admins, which is invaluable.
Reduces Size or Eliminates Batteries Altogether.
With less demand on the battery, systems may be able to choose less bulky or costly options. This is very useful for space-critical applications where reducing device volume is essential. Solar can also enable systems to eliminate batteries altogether, opening a broad range of new opportunities.
Promotes Sustainable and Eco-Friendly Electronics
A rapidly expanding IoT, combined with the age of disposables, is a recipe for environmental disaster. Solar energy harvesting enables the long-lasting, sustainable electronics needed for the next generation of eco-friendly IoT systems.
With PowerFilm's extensive experience developing power solutions for IoT devices, we can work with you to find the best solar, charge controller, and storage element solution for your application.
If you would like to learn more about how you can pair solar or light-harvesting with primary, rechargeable, and capacitor-based storage elements, please contact us.