The Secret to Eliminating Battery Waste: Energy Harvesting
By Srenik Mehta, Senior Vice President, Engineering at Atmosic
Every year around Earth Day (April 22), there are conversations about making the technology around us more sustainable. At Atmosic, we’re working hard year-round to help solve one key sustainability issue: battery waste. So many of the devices around us are battery-powered, leading to billions of batteries being thrown out every year, contaminating landfills with harmful chemicals. As the Internet of Things (IoT) increases the number of battery-powered devices in our homes, our workplaces, and our retail outlets, the frequent replacement of batteries is not just an environmental problem, but an operational one as well. Imagine the time and expense required to replace batteries in hundreds of electronic shelf labels in a retail store, or in the environmental monitoring sensors used in an office building or factory.
Atmosic’s ultra low power wireless connectivity solutions are helping to solve this problem by making it possible for batteries to last the entire lifetime of a device, and in certain cases, our technology can even enable devices to operate totally battery-free. Our larger vision is to usher in an era where the IoT is totally battery-free! So, what’s the secret to making this vision a reality? The answer is energy harvesting.
Energy harvesting promises to be one of the biggest trends for all kinds of connected devices over the next few years. In fact, customers of Atmosic are already delivering products such as remote controls and wireless keyboards that will never require a battery change in their lifetime. To show energy harvesting’s environmental benefits, a remote control solution based on the Atmosic solution eliminates the need for 10 AAA batteries over a lifetime of usage, and for one million remote controls, this amounts to the reduction of a staggering 525 tons of greenhouse gas emissions!
The same environmental advantages hold true for larger commercial IoT deployments, where bottom-line benefits can be seen by both management and IT teams looking to reduce costly battery maintenance intervals or unscheduled device outages in stores that may have implemented thousands of electronic shelf labels, factories using asset trackers and environmental monitors, or airports/stadiums where hundreds of wayfinding beacons help passengers or spectators navigate a facility.
This blog will explore several energy sources that can be captured with Atmosic’s technology, including ambient light, radio, mechanical/kinetic motion, and thermal sources. It’s important to remember that no single energy source works for every application. The best solution for a particular application is highly dependent on the operating environment and energy needs of the device.
One common misconception of photovoltaic (PV) harvesting is that there needs to be a lot of light to harvest enough energy for a wireless device to operate. However, the combination of Atmosic’s extremely low power consumption combined with PV cell technologies that harvest light at low indoor light levels makes it possible to accomplish this today with a PV cell that fits easily on a keyboard or remote control. What’s even cooler is that you don’t have to see the light to get power from it; Atmosic’s solutions support harvesting from visible and non-visible (e.g., infrared) light sources.
While PV cells can be found on some wireless keyboards and remote controls, there are technology advancements that make PV harvesting more efficient as an energy source and more flexible for integration into many more products. While a glass substrate is the most common material for PV cells today, the capability for building PV cells into a variety of flexible materials has reached the mainstream market. This makes it easier to integrate PV harvesting into window sensors, door locks, cameras around your home, environmental sensors in the office or factory, or the shelf labels at the corner grocery store.
Radio Frequency Harvesting
Radio frequency (RF) harvesting pulls energy from RF transmitters and is a great way to power multiple devices at the same time over a distance. Think about how much money and time could be saved when powering many sensors in a factory or reading asset tags when compared to traditional battery solutions that require constant replacement.
Atmosic’s wireless connectivity solutions have an integrated RF harvester with a separate antenna input specifically tuned to the desired harvest frequency. This gives the solution flexibility while minimizing the cost of adding RF harvesting.
One important aspect of RF harvesting to keep in mind is the need for an RF source (often called a transmitter) to be in relatively close proximity to the device being powered. The exact distance depends on the frequency, transmit power, and duty cycle of the transmitter. At lower RF frequencies (such as 900 MHz) with higher transmit power, devices can be up to five or six meters away from the source; for higher frequencies (like 2.4 GHz), devices might need to be a few inches from the source to make a harvesting solution feasible. In some cases it may be possible to leverage existing RF devices to provide an RF harvesting source, but often a dedicated transmitter must be set up to provide this RF power source. By taking these factors into consideration, designers can determine whether RF harvesting makes sense for a particular application, or whether another energy source might be a better option.
Mechanical motion can also be used as a power source, whether it comes from an actuating motion like a button press, the vibration of a motor, or the pressure on the sole of a running shoe. Different types of mechanical harvesters are used to generate bursts of energy from each type of motion, such as piezoelectric generators that respond to mechanical pressure and resonant vibrational harvesters for motors. Today, customers are using Atmosic in battery-free mechanical harvesting wall switches for smart lighting controls. In the future, mechanical harvesting technology better able to harvest non-specific motion will be available to power smart clothing and other wearable products. Along with the more traditional resonant harvesters used with machinery, it is easy to see the great potential for mechanical harvesting across many potential applications. Getting the most out of the energy generated by mechanical harvesting requires the advanced energy management and low power wireless technology offered by Atmosic.
Heat sources like motors, hot water pipes, and even the human body can also be used as a source of energy to power wireless monitors and sensors. A thermoelectric generator (TEG) converts the temperature gradient between a heat source and the ambient environment into electrical energy that can be fed into Atmosic’s low-power wireless solutions. As greater temperature differences generate larger amounts of energy, it is possible to leverage a heat source to generate and store sufficient energy and eliminate the need for a battery entirely. For hard-to-reach sensors in a commercial or industrial setting, the elimination of expensive battery maintenance can more than pay for the additional cost of the TEG in a wireless sensor. On the human body, thermal harvesting can be used to create wearables capable of monitoring vital signs or transmitting location beacons without the need for bulky batteries.
For more information about how Atmosic achieves best-in-class power consumption, check out our recent post “A Groundbreaking New Approach to Reducing Power Consumption.” And stay tuned for our next blog post to learn more about how Atmosic’s integrated Power Management Unit (PMU) differentiates our technology in low power energy harvesting applications.