Self-powering the internet of things

Harnessing ambient energy sources is critical to the rollout of the internet of things in industry

By Morand Fachot

The rapidly growing number of connected devices that form the backbone of the internet of things must become self-powered. The US research and advisory company Gartner, Inc. forecasts that 8,4 billion connected things will be in use worldwide in 2017, up 31% from 2016, and will reach 20,4 billion by 2020. Powering these with batteries or by connecting them to power networks would be totally impractical, even impossible.

Thermal energy harvesting powered wireless sensor Thermal energy harvesting powered wireless sensor (Photo: DELTA Microelectronics)

No power: no IoT!

The internet of things (IoT) relies on connected devices made up of sensors, microprocessors as well as wireless systems and protocols for data processing and transmission to communicate with each other and the larger system. All this physical and communication components depend, obviously, on some source of power.

For consumer IoT devices and systems such as “smart” phones, wearables, appliances and multimedia equipment as well as some gear used in smart homes, this is not such a problem. These devices don’t come in large numbers in a personal environment and can be connected to the grid, or powered by disposable or rechargeable batteries, which can be easily accessed, replaced or recharged.

The problem is totally different in an industrial IoT (IIoT) environment where countless connected devices and wireless power networks are meant to operate independently, over long periods, in places difficult to access or in harsh environments.

Connecting these devices to a power network is often not feasible, impractical and costly. Replacing batteries every few weeks or months can also be impractical and costly, or not feasible when, for instance these devices are deployed in very high temperature environments unsuitable for batteries.

The IIoT today still relies to a great extent on batteries.

The best solution for these devices is to be, as far as possible, self-powered, by relying and drawing on ambient energy sources, a process known as energy harvesting (EH). Tomorrow’s IIoT will be powered by its environment, by EH.

EH makes self-powered connected devices possible and brings connectivity for IIoT to previously unreachable places. It can also be combined with storage systems such as disposable and rechargeable batteries, capacitors or super capacitors, each with its own characteristics, making self-powered IIoT environments possible and flexible. 

Multiple EH sources

The IDTechEx technology market research and business intelligence company gave a broad overview of mature and developing EH sources for IoT at a recent event in Berlin.
Mature EH technologies that can be used currently for IoT applications are:

  • Electrodynamic, like that produced in dynamos (bicycle dynamos, for instance), crank-up devices and connected or not to a storage system
  • Light EH, with energy captured from the sun, from infrared (IR) or ultraviolet (UV) lights via photovoltaic (PV) systems (used in calculators, watches, IoT beacons, wearables)
  • Thermoelectric, which relies on the Seebeck effect, which is the generation of a voltage across a material as a result of a temperature difference. Electricity is produced using thermoelectric generators (TEGs)
  • Piezoelectric, where energy from vibration or movement is captured by piezoelectric effect (most widespread use so far has been in lighters, but is seen as offering interesting prospects)

Developing EH technologies are principally:

  • Electrostatic (capacitive) in which energy is harvested by changing capacitor dimensions by force, e.g. by applying torsion, stretching using elastomer dielectric and stretchable electrodes
  • Magnetostrictive, with movement generating electricity when magnetic properties of a material are changed following applied stress (Villari effect)
  • Triboelectric principle, where energy is generated through friction and based on contact electrification and electrostatic induction using materials with opposite charge affinity
  • Pyroelectric EH, using temperature changes
  • Ambient radio frequency (RF) radiation, with energy harvested from radio waves used for radio and TV transmissions, mobile and WiFi networks. RF EH is used to power RFID devices, such as transceivers (transmitters/receivers) 

IEC International Standards central to EH in all domains

Most current EH and storage technologies used to power IoT devices depend on IEC International Standards.

Light EH from the sun, IR or UV lights, relies on Standards developed by IEC TC 82: Solar photovoltaic energy systems.

Thermoelectric EH is based on TEGs, which use of semiconductor devices; International Standards for these are being prepared by IEC TC 47: Semiconductor devices.

Many aspects of piezoelectric EH rest on technology for which IEC TC 49: Piezoelectric, dielectric and electrostatic devices and associated materials for frequency control, selection and detection, prepares International Standards.

Storage for EH devices relies on standardization work by IEC TC 21: Secondary cells and batteries, IEC TC 35: Primary cells and batteries, IEC TC 33: Power capacitors and their applications, and IEC TC 40: Capacitors and resistors for electronic equipment.

In addition, Standards by more recently-created  IEC TCs, such as IEC TC 119: Printed electronics, IEC TC 124: Wearable electronic devices and technologies, are central to the development of IoT. 

Gallery
energy harvesting evaluation kit The E-821.EHD piezoelectric evaluation kit contains piezo transducers, storage electronics and all required cabling for integration in an application. The E-821 energy harvesting electronics kit and P-876 DuraAct patch transducers (Photo: PI Ceramic GmbH)
Thermal energy harvesting powered wireless sensor Thermal energy harvesting powered wireless sensor (Photo: DELTA Microelectronics)
eco-drive watch The Citizen Eco-Drive technology harnesses the power of light from any natural or artificial light source and converts it into energy to charge a lithium-ion battery that drives the watch's movement (Photo: Citizen)