Energy harvesting technologies find their place in IoT


Consider a classic predictive maintenance IoT scenario: You place smart sensors on the wheel bearing housings of all the wheels of a railroad car to check for vibrations that portend failure in time to avoid disaster. Other: You tag each asset in your hospital with an RFID chip that not only locates the object on a screen, but stores its entire maintenance record.

What might make you think twice before deploying these IoT apps? Feed them. Batteries can make these solutions impractical, difficult, or expensive, as these sensors and tags can be placed in remote locations or number in the millions or require surgery to reach them.

This is where energy harvesting technologies, or better, energy harvesting technologies, come in. This is the capture, storage and reuse of light, vibration or light. movements, electromagnetic radiation, or other energies that otherwise dissipate into the atmosphere. The technology goes back as far as self-winding, battery-less watches. It is gaining momentum now because energy harvesting technologies are becoming more efficient at recovering milliwatts and, on the other hand, sensors are consuming less energy.

Energy recovery without radio for IoT

Bob Hamlin is CTO of Tego Inc., based in Waltham, Mass., Which harvests ambient RF energy.

“All FM stations transmit power from the antennas at 50 to 100 kilowatts,” he noted. “By the time it gets to your FM radio, it’s only a few milliwatts. Nowadays, those few milliwatts are enough to do all kinds of cool stuff with electronic circuits.”

The RFID devices that Tego manufactures take the carrier signal from the RFID reader and rectify it to a DC voltage. Tego uses this power – as little as 4 milliwatts – to power the processor which is the heart of its RFID chip. Tego’s combined RFID chip and antenna add writable, readable and encryptable data to any type of asset, moving intelligence to the edge of the IoT.

Originally, these chips could only work within five or 10 feet of the drive. “These days, traditional passive RFID – just ID tags – can operate from 50 to 100 feet. These things work in microwatts of power,” Hamlin said. But Tego’s goal isn’t to extend the distance between the RFID scanner and, say, the retail RFID tag, which might contain just 96 bits to identify the brand and price of a jersey. bath. Instead, it adds storage and processing workload to the chip. Obviously, it’s not about tagging swimsuits, but about tracking and documenting parts and devices in aerospace, oil and gas exploration, life sciences and applications alike. important.

Tego’s roots and wireless protocols are in RFID, but it also considers Wi-Fi and other radio transmissions as power sources. “When most people hear IoT, they think of their phones and laptops,” Hamlin said. “We think of this as the first ring outside the network. But further down there are other rings where the devices are no longer plugged into the wall, no longer work on Windows or iOS. They are smaller, n ‘ do not have full operating systems, have more dedicated processing, and by nature consume much less power. ” In addition, they can be so far from power sources that they have to operate “on their own”. Like the anemones at the bottom of the sea, they must feed on what passes.

One version of Tego’s beacons has a serial interface on its chip, suitable for connecting to sensors or microprocessors. A client is working on a new highway; installing these beacons every 300 feet in the pavement over a bridge so they can monitor the temperature as the pavement hardens, as a step towards improving durability.

Demonstration of a Tego device recovering RF energy to power an LED light.

Vibrational energy recovery for IoT

ReVibe Energy of Gothenburg, Sweden, also addresses predictive maintenance needs while focusing on converting vibration to AC power. Its two produced harvesters can be bolted directly to a vibration source and feed multiple sensors by wire. ModelA produces up to 150 milliwatts with a constant vibrating frequency of 15 to 100 Hz. ModelD produces up to 40 milliwatts. Like many of these harvesting devices, they also store energy for later use.

Its current customers are sensor manufacturers, but it has yet to produce in commercial volumes.

Out of four ways to convert vibrations into energy, ReVibe uses electromagnetic induction, company chief operating officer Erik Kling said. ReVibe’s patented technology improves the efficiency of this method so that more milliwatts are produced for a given weight and cost of the harvester. As resonant harvesters, ReVibe products require vibrations of constant amplitude and dominant frequency.

It attracts the most interest from rail, aerospace, construction and mining equipment companies. Kling described a pilot study carried out with Deutsche Bahn (DB), Germany’s national railway. DB’s 50,000 track switches are currently equipped with battery-powered wireless sensors that measure their range of motion and download the data via a cellular signal. (Switching problems account for 20% of all DB delays, Kling said.) Their batteries need to be replaced every two years. ReVibe combines are testing the busiest trails to see if its vibration-recharged energy harvesting technologies can extend battery life or even replace them completely.

Another pilot – a “manual” application, Kling said – monitors the temperature of the wheel bearings of freight and passenger trains. Perpetuum, a UK company specializing in vibratory energy harvesting technologies, has contracts for such applications with UK railways. Kling also mentioned a construction vehicle supplier that wants to use vibration energy to capture data from sensors that will allow it to provide after-sales service to customers. A leasing company wants to attach sensors and data storage that will tell them where their leased vehicles are and how much they have been used.

ReVibe vibratory energy harvesting technologies
Model A (left) and Model D (right) from ReVibe Energy.

Light energy recovery for IoT

Solar is best known for its panels, an alternative energy source that, like wind, powers existing power grids. But on a much smaller scale, photovoltaic (PV) energy is harvested and stored by small, stand-alone (off-grid) devices, using indoor ambient light as well as sunlight.

Wibicom Inc. in Montreal, Canada, has produced a combination of PV harvester and antenna, which it offers with a range of sensors. (“Organic photovoltaic materials” – polymers combined with carbon chain fullerenes, replace inorganic PV materials, typically silicon-based, which are less environmentally friendly in both manufacture and disposal.)

Wibicom’s ENVIRO, a circular PV collector and antenna approximately 2 inches in diameter, can sense and report environmental data such as temperature, humidity, pressure and acceleration. Its maximum load, powering the Bluetooth LE radio and sensors, is 13 milliwatts in direct sunlight; its data sending range, with line-of-sight transmission, is over 100 meters. It can run for up to two months in the dark on stored energy. Price: around $ 100. Customers: in pilot phase.

Wibicom’s smallest Move harvester – pictured alongside a Canadian two dollar coin – is positioned as an advanced PV-powered beacon and comes with an accelerometer to detect activity. With lower power and price, it can broadcast messages to passers-by or even power portable devices.

Mina Danesh, CEO of Wibicom, explained that these communicating PV harvesters “can be connected like a beacon [that might transmit directly to a smartphone] or they can be connected to the Internet through a gateway, where a cloud server can collect and analyze the data. a WibiSmart mobile application that displays the detected conditions live and a web version that compiles data over time.

In 2013, Wibicom partnered with the Finnish research and development institute VTT and other companies on a three-year EU-funded ArtESun project, which demonstrated the product of their research on new organic photovoltaic (OPV) electrode and active layer materials, as well as coating and module interconnection techniques. These efforts are aimed at lower manufacturing costs, higher energy capture efficiency and a milder environmental impact. The project demonstrated an active RFID tag that used a credit card-sized OPV module and a built-in sensor to report detected conditions to an RFID reader. The module’s built-in energy storage and surge protection could power the tag for up to a day in low light conditions.

A second OPV use case demonstrated the potential for inexpensive mass production in the form of a flexible flower-shaped harvester / antenna module. Produced in a rotogravure printing process, it fed an antenna and an environmental sensor into a distributed Bluetooth LE wireless network.

And in a separate proof of concept, Wibicom’s partner, VTT, printed “leaves” that scavenge energy from light or wind, and wired them to 3D printed “trees” that could aggregate power. to power more demanding devices. The tree generated a lot of interest and purchase requests in 2015, said Tapio Ritvonen, head of the VTT research team, but the technology is still awaiting commercial production and implementation.

According to the French market research firm Yole Développement, the market for energy harvesting technology modules is expected to reach $ 227 million by the end of 2017, led by building automation, railway and industrial applications. . The IoT has given this academic field and its largely European group of tech startups a powerful new raison d’être and, they hope, the funding and contracts that go with it.

Wibicom photovoltaic energy recovery technologies