When will wireless power transfer redefine the Industrial IoT?
The predicted number of networked and connected devices is constantly being revised. The reason may be that the definition of the Internet of Things (IoT) is also quite fluid. Limiting the definition to devices directly addressable through the internet over an Internet Protocol link excludes too many that are indirectly connected through a gateway or hub. That could include any number of sensors and actuators.
Perhaps it would be more reasonable to describe the IoT in terms of services. The concept of a service-oriented architecture (SOA) is beginning to gain traction in various verticals. As it expands, SOA could be a more accurate way of describing the IoT in the future.
This may seem pedantic, but it is important. By moving toward SOA, sensors no longer need to be thought of as individually addressable devices. This sits perfectly alongside the trend toward using artificial intelligence (AI) at the edge. Sensor fusion using AI to infer actions from clusters of “dumb” sensors would redefine the IoT. The output of that sensor cluster would be a service. The way the data is derived would be largely unimportant in comparison to the service provided by the connected endpoint.
Wireless power transfer for SOA in the IoT
Using AI and low-power processors puts powerful compute platforms at the heart of the data. It makes sense to capitalize on that by connecting those platforms to as many sensor nodes as possible. By consolidating and aggregating the sensor data, machine learning can be used to generate real intelligence. More specifically, endpoints can provide intelligence-driven services rather than raw data or even just basic insights.
Each endpoint could be connected to tens or even hundreds of individual single-purpose sensors. However, providing continuous power to an expansive array of sensors could become a limiting factor. No single operator would be prepared to maintain that many sensors if they were all battery powered. Implementing hard-wired power could also be restrictive.
This is where self-powered sensor nodes will make a real impact. Relying on alternative forms of energy as the primary source of power is becoming more viable every day. The availability of ultra-low power microcontrollers continues to grow and the use of wireless communications using harvested energy is now a proven reality.
All of this points to a renewed interest and increased investment in RF power transfer. There is precedence for this already in the form of radio-frequency identification (RFID) and wireless charging standards. Contactless power transfer operates across small air gaps using inductive or capacitive coupling. However, for wireless power transfer to become viable in wireless sensor networks it needs to work over greater distances, typically tens of feet. This points toward harnessing radiated energy traveling through the air.
The conventional way of achieving this is by emitting RF waveforms that are then received in the antennas of the devices being powered. The RF energy can be focused and purposefully emitted, or it can be stray RF energy from other wireless devices in the area, such as Wi-Fi access points.
Efficiency is the key to commercial success
The idea and practical implementation of wireless power transfer is far from new. It is well known that providing power without wires was one of Nikola Tesla’s life ambitions, having demonstrated it well over 100 years ago. It has also been used in applications where efficiency is low on the list of requirements, so the theory is sound.
What has changed over recent years is the way it can be achieved in a commercial environment, thanks to increased efficiency. One way to increase efficiency is to focus all the energy generated directly at the receiver in a point-to-point configuration. This is the approach taken by a company called Emrod, which recently secured a contract with New Zealand’s second-largest energy provider to demonstrate the delivery of several kilowatts of power — wirelessly — over distances that are only limited by the amount of power put in, the size of the antenna and having a clear line-of-sight between the two antennas.
Emrod says its patented technology uses metamaterials in the transmitting and receiving antennas. These metamaterials are key because they convert RF energy into electricity with virtually no losses. The company claims that its technology is scalable; larger antennas support more energy transfer.
In the Industrial IoT the question is likely to be more about scaling the technology down. Sensor nodes will be tiny, so there won’t be much room for large antennas. However, smaller wireless substations that supply several wired sensor nodes could presumably work.
Power transfer for wireless sensor networks
Several companies are now supplying solutions for wireless power transfer that could be used in wireless sensor networks. TransferFi is focused exclusively on RF power transfer using beamforming, enabled by its IIoT gateways. The company says its gateways have an effective range of up to 24 meters to power its sensors. The sensors themselves feature a three-axis accelerometer and communicate using Bluetooth.
Everactive’s sensors use multiple forms of energy-harvesting techniques to capture and store energy, including heat, light and RF as well as vibration. This battery-less, always-on and always-transmitting approach could support ubiquitous sensing without the expense of providing power.
Another example comes from a company called GuRu, which is using mmWave technology to deliver power wirelessly in a focused way. Its Smart Lensing technology is described as beams of energy. This is similar to other approaches in that it uses beamforming to increase efficiency, rather than using an ambient backscatter approach to capturing stray RF in the area. However, it seems to be unique in doing this at mmWave frequencies. This technology could find its way into the 6G networks of the future, where ubiquitous power is on the wish list.
Most wireless power transfer technologies use either near-field (inductive) or far-field (radiative) technologies. One company, Ossia based in Redmond, Washington, has combined the two to create a wireless power transfer solution that stands alone. Ossia has FCC approval for sale in the U.S. and recently received type approval for its wireless power technology for use in the European Union and U.K. markets, too. Unlike others, Ossia’s technology is not limited to line-of-sight and can instead create paths between a transmitter and receiver that not only detect obstacles — like furniture, people or pets — but can “bend” around them. This maintains power delivery even when there is no clear and direct path. This differs from others mentioned here which, typically, cut power when an obstacle is present.
Future developments in wireless power transfer
Part of the vision for the 6G communications network is to redefine the architecture. This includes moving to a distributed network that is far less like the cellular networks we have developed to date and more integrated into the fabric of buildings and other objects.
This extends to using the network to wirelessly provide power to ultra-low power – sometimes referred to as zero-energy – nodes. These nodes would also be part of the fabric and powered by RF energy provided by the network. They will enable both continuation of network coverage and fundamental functionality.
Although it is still only research at the moment, the inclusion of wireless power transfer in what will become 6G must be seen as significant. It implies that the IoT will, indeed, expand at the edge in a way that supports what we might start to refer as extreme endpoints, which are only indirectly addressable and largely unseen. These devices will be actively sensing and reporting on a local basis to contribute toward what will then possibly become known as the small data of the IoT.
If this happens, there will soon be a new generation of users who expect everything to be connected all the time. The thought that something may be “dumb” will be alien to the next generation and as strange as the idea of a world before the Internet is to this one. To learn more about what 6G may look like, take a look at the Reindeer Project, one of the funded projects working on the underlying technology needed.
Most of the technologies being used in wireless power transfer are based on fundamental principles. What has changed over the last few decades is the way we work out how to apply these principles, thanks to advances in areas including hyperscale processing and simulation.
Something that is not so fundamental is the use of metamaterials and rectifying antennas, or rectennas. A metamaterial is less about the material and more about the way it is used to manipulate electromagnetic waves, something that is critical in wireless power transfer. A rectenna is a receiving antenna designed to rectify RF energy into a direct current and, for that reason, will be equally critical in the development of wireless power transfer.
Today, there are several approaches to implementing wireless power transfer. They range from near-field to far-field, spanning frequencies from sub-GHz to tens of GHz. Wireless power transfer has been identified as one of the most important technologies for the next decade, and with good reason. To read more about how the IEEE is approaching wireless power transfer, visit wpt.ieee.org.
As with most emerging technologies, we can probably expect some consolidation and attrition in the various approaches being taken. The key elements are all available today, including power management ICs (PMICs) designed for energy harvesting applications, ultra-low power wireless microcontrollers and small energy storage devices such as (super)capacitors and rechargeable batteries.
The benefits of wireless power transfer may be most strongly appreciated in the IIoT. Predictive maintenance and condition monitoring are becoming fundamental in industrial automation, which relies heavily on sensors to capture real-time operational data on a 24/7 basis. The more sensors that can be deployed, the more data that can be captured and interpreted to keep the wheels turning.
Taking wireless power transfer mainstream
To realize the potential of wireless power transfer in the IIoT, more investment is needed in meta materials, more developments in rectenna technologies and continued evolution of ultra-low power integrated circuits.