Mobile device network signals, Wi-Fi, and other radio frequencies can actually be used as sources of power and not just communication signals. Special antennas can convert the signals that fill our air into useable electricity. So beyond natural elements, man-made technology can provide added benefit in a secondary function. In addition, RF is abundant and ubiquitous, owing to the interest it has garnered as an energy harvesting power source.
Using proprietary RF-to-DC conversion technology, Powercast enables wireless power or charging for low-powered electronic devices. The technology efficiency converts energy, allowing devices to operate without a battery, but the technology could also be used to resupply rechargeable batteries in devices that may not have continual proximity to an RF generator. The technology lends well to industrial applications, especially RFID tags. Powercast manufactures a batteryless RFID tag that also has built in temperature, light, and humidity sensors for added functionality (ie SuperTag). Wireless charging through RF energy harvesting also has application in powering or charging wearable devices.
Another producer of RF-harvesting technology, Drayson Technologies, was awarded ‘Best Technical Development Within Energy Harvesting’ for Freevolt technology. Freevolt is a breakthrough technology that can harvest energy from wireless networks (such as 3G, 4G, and WiFi, etc.) to power low energy IoT devices, including sensors, beacons, and wearables. Now, energy can be pulled directly from the air for a continuous power supply, eliminating the need for charging the devices with cables or replacing batteries. The technology offers more convenience for consumers and will aid in greater deployment of IoT solutions.
RF harvesting energy technologies could provide a good solution for powering sensor networks in remote areas or extreme environments where other energy harvesting technologies may not be feasible or ideal. Progress in more efficient power conversion or designing harvesters that can pick up a variety of frequencies will continue to advance the technology.
Piezoelectrics (Human Powered Energy)
With the advancement of energy harvesting technologies, human movement can now be used as an electricity generating power source. From the flooring we are walking on to the materials we wear, the movements we perform everyday can be converted to source of energy harvesting.
Pavegen has designed a custom flooring system which captures energy and data from footsteps and are aiming to a create a whole new level of connectivity within cities. Their tiles harvest kinetic energy when the displacement resulting from the compression of a footstep causes electromagnetic induction generators to shift vertically, creating a rotary motion that generates electricity. Further, their tiles are fitted with wireless technology to track movement data.
With the flooring, our footsteps would not only propel us forward but power us up, generating electricity for devices in smart homes, buildings, and cities. Yet, the co-present data connectivity applications are equally as exciting. With Pavegen’s data tracking and analytics, our steps can be used a sort of digital energy currency, earning rewards with businesses or able to be donated to charitable causes. Business could also use the flooring to track peak foot traffic times and learn consumer movement patterns.
Figure 8. An individual tile of Pavegen flooring, when compressed, creates mechanical displacement which generates electricity.
Pavegen has permanent installations all over the world and has just unveiled its first large scale outdoor installation, at Dupont Circle, Washington D.C., on November 18. The installation hosts three arrays which capture the busy foot traffic to power lighting and contribute power to the local grid. In 2014, Pavegen partnered with Shell and a solar energy company to install their technology in at a football pitch in a favela in Rio de Janeiro, Brazil. The energy creating by children and adults playing on the pitch during the day powers the floodlights at night, creating a safe environment for the community to be active. So, even in areas with limited resources, Pavegen technology is allowing people to use their own movement to power their environment. The technology beautifully represents the promise of energy harvesting to be eco-friendly, socially responsible, and promoting of a healthy human experience.
As featured in Top 10 Most Futuristic and Innovative Startups at IDTechEx USA 2016, EW Panel produces energy harvesting flooring panels. When walked on, the panels produce a small voltage that can be used for powering small electronic devices or for energy storage. This is another example of converting our environment to make the movements we perform everyday more productive for us.
StretchSense is also focusing on the harvesting power from human motion with their variable capacitor energy harvester targeted for microelectronics in wearables and smart garments. When their Soft Generator energy harvesting unit relaxes after being compressed (or stretched), mechanical energy is converted to high voltage electricity which is then stepped down to a lower voltage to power microelectronics. Footwear is a very promising area for this technology, as repeated, rhythmic compression could generate an ample amount of useable power, but their flexible material can also harvest from other body motion, such as joint movement or breathing. StretchSense is working towards combining this technology with their smart stretch sensors that track body motion to create self-powered wearables.
Though still in development, Adamant presented its electromagnetic energy (EME) harvester technology. The devices are compact, self-charging, and can come in several possible forms corresponding to different power generating methods: vibration, slide, switch, force-driven, and curve types. The small harvesters are able to achieve high output energy because good magnetic flux density is produced by surrounding a magnet and coil with a ferromagnetic yoke (better than magnet and coil alone). The vibration-type harvester can produce up to 62 mW, with an average output of 20 mW. Some possible applications include independently powering wireless sensor networks or security systems or for battery charging functions. By providing an on-demand, re-usable energy source, Adamant’s technology confirms the eco-friendliness of energy harvesting technology.
Just emerging to the market, Star Micronics exhibited their vibration power generator and vibration harvester beacon for IoT applications. Vibration generates electricity in the harvesters by causing movement of a magnet around a coil. The vibration harvester beacon is specifically designed to harvest energy during walking motion. When incorporated in the form of an ID Tag, the beacon could relay where a person was in a building (for tracking purposes) and be completely powered by walking motion. Another application of the beacon technology is to be embedded in a shopping cart wheel. The rolling motion of the wheel produced enough electricity to power the beacon and that would allow for cart location information or interactive experiences with consumers.
Small electromagnetic harvesting devices are enabling new self-powered IoT solutions. New form factors or different motion sources could be explored in the future.
On a larger scale, magnetic induction technology is looking to provide charging solutions for electric vehicles. Magment offers a tool in the form of magnetic cement for inductive applications, that would charge the battery of an electric vehicle traveling over the materials. They offer both a cement composite material and an asphalt composite material that are laden with magnetizable particles. The materials can be also used for wireless power transmission, or induction heating or cooking.
Figure 10. Sampling of magnetic concrete by Magment