Energy Harvesting Trends
Despite the growing number of benefits that energy harvesting presents, there are challenges engineers face in integrating harvesting platforms into the design process.
Energy harvesting is altering the way engineers think about power management and smart energy. Today’s harvesting trends suggest more institutions are taking advantage of it. Despite this, and the growing number of benefits that energy harvesting presents, there are challenges engineers face in integrating harvesting platforms into the design process, from both the manufacturer and developer perspective. As both a concept and practical application, energy harvesting has existed for quite some time. It is only now, however, that we’re discovering its extended potential.
Present Use Cases
We are already seeing unique and interesting applications of energy harvesting solutions across industries. Phillips, for example, is working on a television remote control powered by motion. European universities are building entire academic programs dedicated to studying the use of nanomaterials for energy, as well as the motion of bridges to harvest energy. Even automotive manufacturers have referred to the “efficient dynamics” of newer cars, which harvest energy from the driver’s braking motions. All are examples of how the benefits of energy harvesting are encouraging institutions and industries to reevaluate their existing practices.
Energy harvesting presents several financial, environmental and design benefits for engineers and users alike. The most inherent of these is the replacement of traditional batteries. Returning to the example of television remotes, the costs associated with creating, shipping, purchasing and disposing of the batteries found in these devices offer little return value when considering the rate at which they are drained. Energy harvesting dispenses with the need for continuous power sources among lower power devices. In addition, energy harvesting offers a safer alternative to the various chemicals emitted into the atmosphere by traditional battery packs.
From a sustainability perspective, energy harvesting is one in a range of solutions which help us live greener lives. We can, for example, reduce our consumption of batteries by harvesting energy. We can also power devices in a cleaner and more efficient way. It is important, however, to bear in mind that as with many renewable sources of energy—solar, wind, etc. —energy harvesting operates under similar constraints. These power sources are not continual; they have peak times and times when they generate little to no power at all. Engineers must apply this logic across the board when using green technologies, and energy harvesting can substantially aid in the design process.
Despite these benefits and more, energy harvesting faces several roadblocks to mass design integration. Energy harvesting is also known as “energy scavenging,” and as the term implies, it attempts to latch onto energy “scraps.” It is therefore not ideal for applications which will require a great deal of continuous power.
For engineers, they must re-think their understanding of energy: how do you take full advantage of it when it is present, how do you store it, and what do you do when it is not present? With a continuous power source, these issues simply don’t exist. For all other power conditions, however, there are pros and cons to various development approaches engineers might take.
To use an example, in our recent Energy Harvesting challenge, an engineer from Poland decided to make a carbon monoxide alarm that didn’t require battery or mains power. His first approach was to check how much energy he could derive using the Peltier module in the “Energy Harvesting Solution to Go” kit provided to him. He quickly realized that the energy wouldn’t be sufficient to power a conventional alarm.
This approach had the virtue of assessing what his energy budget was, and then building the application around it; however, it could be argued that he should have looked at how he could create such an alarm that used as little energy as possible first, then decided how to power it. In the first case, power sources determined the functionality; but perhaps functionality should be used to determine which form of energy harvesting is used, if not multiple sources of energy harvesting at once.
However the power conditions may vary, design engineers experimenting with energy harvesting are still guessing which conditions their solutions will be used in, and those guesses won’t always be right.
Emerging Solutions and Technologies
Solutions to energy harvesting design flaws will most likely arise from utilizing multiple sources of energy harvesting in one solution or product. Engineers may also take the approach of minimization: taking the functionality of a system and curbing its power system to the lowest level possible. This can be done by selecting the right low-energy chips, sensors and microcontrollers, and matching them with the correct energy harvesting power supply (such as the Piezoelectric and Peltier harvester modules). This isn’t easy—engineers will have to be able to store and manage energy when it is not available.
In the case of the aforementioned example, it was necessary to use a Figaro TGS 5042 sensor for our engineer’s carbon monoxide detector. This is an electrochemical sensor which doesn’t require power to operate. In terms of microcontrollers, the Silicon Labs EFM32 series have very low power consumption and are adapted for practical applications of this nature.
The key determinant in choosing among these various development approaches is environment. If you are in a scenario in which there are limited sources from which to derive power, i.e., somewhere that has thermal energy but no light or other forms of energy, then the power is going to determine the functionality you can have. If, on the other hand, you have access to multiple sources of energy, then perhaps the functionality can determine what power sources you tap into, and how much redundancy you put into your solutions.
Manufacturers can also play a part in easing the transition to energy harvesting designs. It is important to present the opportunity for engineers to get their hands on harvesting platforms if they wish to move beyond traditional power solutions. Capacitive manufacturers and battery manufacturers can also develop and offer batteries that already store energy efficiently, so that engineers are free to focus on other aspects of the design process. Again, this isn’t an easy task. If harvesting offers a viable energy alternative, and early applications suggest that it can, then it should be treated as one.
As the power requirements for applications continue to drop and, with the help of engineers, harvesting gathers increasing amounts of energy, we will all begin to see more practical uses of energy harvesting solutions arise.
Christian DeFeo is the e-supplier manager at Newark element14, a global electronics distributor and online community of 200,000 design engineers and tech enthusiasts. Recently, he oversaw an energy harvesting challenge at the element14 Community, in which engineers around the world developed power solutions for everyday devices. www.newark.com