Summary
Vibration energy harvesting, particularly through electromagnetic mechanisms, represents an exciting advancement in industrial IoT and wireless sensor technology. By turning the natural vibrations of machines into a power source, it enables smarter, more efficient monitoring with minimal maintenance needs. The ability to store energy in a rechargeable battery further ensures that sensors remain operational even during machine downtime, providing uninterrupted insights into equipment health.
This technology not only supports operational efficiency but also reflects a step forward in sustainable industrial practices.
Introduction
Industrial machines like vibrating screens and feeders are critical in industrial processes such as mining and aggregates production, but also e.g. recycling, food processing, pharmaceuticals, oil & gas and many others. Monitoring their performance is vital to ensure efficiency and longevity. To make this possible without the hassle of external power sources or frequent battery replacements, vibration energy harvesting offers a very practical solution. This method converts the machine’s vibrations into electrical energy, enabling self-powered wireless sensors to send continuous data and monitor the equipment in real time.
This article takes a dive into the electromagnetic energy harvesting mechanism used in this context, explaining how it works and why it is particularly effective for these applications. Whether you have a technical background or not, the principles of this technology can be understood with a simple analogy and some basic science.
The Basics of Vibration Energy Harvesting
Energy harvesting is the concept of small-scale energy generation from ambient sources such as solar energy, wind power, thermal energy, salinity gradients or kinetic energy to power small wireless autonomous devices.
Vibration energy harvesting is one way out of many to convert the ambient energy into electricity. In ReVibe’s case, we leverage the natural mechanical energy present in vibrating machines. Instead of letting these vibrations dissipate as wasted energy, they can be captured and transformed into usable power. ReVibe has several patents in this field covering e.g. how to ensure mechanical robustness and a high size-to-output ratio.
The components of the vibration energy harvesting process are the following:
- Vibration Source: Machines like vibrating screens produce mechanical oscillations as they operate. These oscillations vary in intensity and frequency based on e.g. the machine type and settings and the material being processed. Generally, however, screens and feeders typically operate on a fixed frequency and acceleration.
- Energy Conversion: This vibration is converted into electrical energy using a suitable mechanism—in this case, an electromagnetic harvester.
- Powering the Sensor: The electrical energy generated powers a wireless sensor, which collects and transmits data about the machine’s health and operation.
How Electromagnetic Energy Harvesting Works
Electromagnetic energy harvesting is a very efficient method for small-scale conversion of mechanical energy into electrical power. Here’s a breakdown of the process:
- Inducing Motion: Inside the energy harvester, there is a small array of magnet(s) and coil(s). When the machine vibrates, the magnet(s) moves relative to the coil(s).
- Generating Electricity: This relative movement creates a changing magnetic field, which induces an electric current in the coil—a phenomenon known as Faraday’s Law of Electromagnetic Induction. The harvester is tuned to a specific resonance frequency, on which the motion is amplified. This means that it generates a significantly higher electric output when oscillating on or near that frequency, and that the resonance frequency should be matched with the frequency of the vibration source. For a crash course in resonance and natural frequency, have a look at this very educative video.
- Storing Energy: The electricity produced is stored in a rechargeable battery within the sensor. This battery, charged by the harvester, powers the sensor even when the machine is turned off. This ensures continuous operation and monitoring.
Why Electromagnetic Energy?
Even within the niche of vibration energy harvesting, there are several different transduction principles, of which electromagnetic induction is one. Others include e.g. piezoelectric materials and electrostatic converters, but electromagnetic energy harvesting stands out for this application because:
- Efficiency: It can generate significant power from low-frequency vibrations, which are common in vibrating screens and feeders.
- Durability: The design is simple and robust, with fewer parts likely to fail over time.
Why Vibrating Screens and Feeders Are Ideal Candidates
Vibrating screens and feeders are particularly well-suited for vibration energy harvesting due to their operating characteristics:
- Steady Frequency with High Acceleration: Screens typically operate at a consistent frequency with significant acceleration levels. Most screens operate within the range of 9 to 25 Hz (540 to 1500 RPM), which aligns optimally with the resonance behaviour of the harvester generator in ReVibe’s Anura sensors mentioned above. This frequency range allows the sensors to generate and store sufficient energy reliably.
- Durability in Harsh Environments: Electromagnetic harvesters are robust and can withstand the dust, dirt, and heavy-duty conditions typical of mining and aggregate operations.
- Simplified Maintenance: By eliminating the need for wired power or regular battery changes, maintenance becomes less frequent and less disruptive.
- Sustainability: Utilizing existing vibrations minimizes waste and aligns with energy-efficient and sustainable practices.
Applications in Real-World Scenarios
Imagine a vibrating screen used to sort minerals at a mining site. Over time, the screen’s components—like bearings or springs—can wear down, leading to inefficiencies or potential failure. A wireless vibration sensor powered by harvested energy can continuously monitor these components and alert operators to anomalies. This proactive approach reduces the risk of unexpected downtime and extends the life of the machine.
Perhaps more important than predictive maintenance, continuous monitoring of the screen can be used to enhance process performance, e.g. to increase output or to improve production quality.
Using batteries to power wireless sensors will always result in a tradeoff between sensor life on the one hand and data rate and quality on the other. An energy harvester acting as an inexhaustible power source allows for the sensor to provide a continuous flow of high quality data in real-time, which in turn enables significantly more advanced analyses and conclusions.
The Broader Impact of Vibration Energy Harvesting
This technology not only enhances the reliability of industrial equipment but also aligns with broader goals of energy efficiency and sustainability. By repurposing existing vibrations into usable energy, it minimizes waste and contributes to reducing the environmental footprint of operations.
Learn More: Insights from Our CTO
To help make these concepts even clearer, we’ve included a short film where our CTO, Per Cederwall, explains the electromagnetic energy harvesting mechanism in detail. Through simple visuals and demonstrations, he unpacks the science behind this innovative approach and its practical applications in real-world settings.
