In the current quest for energy independence and the fight against global warming, the future looks promising for energy harvesting. This concept encompasses the technologies that make it possible to retrieve energy from the environment or produced by the movements of human beings.
Solar, thermal, vibrational, kinetic, and electromagnetic energies can provide limited power, in the order of several microwatts to several milliwatts per square centimeter(1). When stored, they suffice for the running of low energy-consuming smart objects, such as small electronic devices worn by people (known as “wearables”) or wireless sensors that measure temperature, pressure, or humidity.
Reducing the IoT’s carbon footprint
Still an emerging concept, energy harvesting appears to be an answer to one of the main problems of the Internet of Things (IoT): battery autonomy and management. According to an article by electronics research firm Innovel, it can already “power devices without batteries, while ensuring them a long service life of up to twenty years”.
Biobatteries take their energy from the environment without polluting it in return.
This promise coincides with the expected boom in the number of smart objects. By the end of 2021, this had already reached 12.3 billion units, on the rise by 9 %, according to a study by IoT Analytics. A figure that could more than double by 2025 to “probably” reach over 27 billion IoT connections.
Beyond the savings made, on equipment maintenance in particular, energy harvesting helps reduce the IoT’s carbon footprint by replacing traditional batteries which, be they single-use or manually rechargeable, remain highly polluting from their creation to their end-of-life processing.
With these assets, the global market of energy harvesting systems should grow significantly. According to a Research and Markets study, it is expected to grow at a compound annual growth rate of 12.75 % to reach around 820 million dollars in 2026, compared to 354 million in 2019.
Many use cases
In a report on energy harvesting, consulting firm IDTechEx provides an overview of the various energy harvesting technologies. Many processes meet the definition of energy harvesting. It is thus possible to call upon photovoltaics, thermoelectricity, kinetics, piezoelectricity, or electromagnetism to harvest energy from the sun, heat, vibrations, or the body’s movements.
The conversion of vibratory energy is used in particular in industry, where machine tools themselves can provide electric energy to the smart sensors connected to them.
The aeronautical sector, for example, uses piezoelectricity, which is based on the ability of certain materials to produce an electric charge in response to applied mechanical stress. French company Enerbee combines magnetic and piezoelectric technologies. Its microgenerator for example, which delivers 1 to 10 mW, “equivalent to 1.5 to 6 AA batteries per year”, can make an air-quality sensor autonomous.
Providing IoT solutions to isolated territories and populations, Lean Connected uses photovoltaic energy to power its weather stations or connected collars for tracking herds over mountain pastures. Also in the area of photovoltaics, Wattway is at the origin of the first photovoltaic road surface in the world. With the energy produced, this Colas group company proposes to recharge electric bikes or to illuminate a pedestrian pathway.
Another world first, a team of American researchers has developed a “rectifying” antenna to harvest the electromagnetic energy of 5G and use it to power electronic devices. This type of antenna can convert radio frequency energy into direct current as is explained in a France Bleu article.
100 % biodegradable batteries
The future of energy harvesting will also include the development of “biobatteries”. These 100 % biodegradable batteries generate chemical energy from plants, algae, or bacteria, taking their energy from the environment without polluting it in return. A spin-off of the CNRS (the French National Center for Scientific Research), startup BeFC has designed an ecological battery whose biocatalysis system uses paper cellulose and enzymes to produce electricity.
The scope of energy harvesting is not limited to small sensors. According to an article in Scientific American, it will extend to smartphones or laptop computers. When scaled, this technology could cover much larger systems such as building lighting devices, medical equipment, and even satellites.
(1) Adila (A. S.), husam (A.) and husi (G.), “Towards the self-powered Internet of Things (IoT) by energy harvesting: Trends and technologies for green IoT”, 2018 2nd International Symposium on Small-scale Intelligent Manufacturing Systems (SIMS), Cavan, 2018, pp. 1-5.
