The world is facing gigantic ecological and economic challenges. Future-proof technologies are to shape the Internet of Things (IoT). The energy supply for millions of communicating devices is a key challenge. On a large scale, renewable energies have long been an integral part of energy generation. Fields with solar cells that generate energy from sunlight or wind turbines now dominate the landscape. This form of energy generation also exists on a smaller scale. This is called “energy harvesting.” Small energy converters “harvest” energy from movement, light, or temperature differences. These amounts of energy are sufficient to power a wireless sensor and transmit data via radio.

Energy harvesting for radio-based products that are already in mass production include four different sources:

1. Motion – the press on a switch, moving machine parts, the rotary motion of a handle
2. Light – the indoor or incoming sunlight in a room
3. Temperature differences – between a heat source such as a radiator, pipes, or boiler and the environment, and day and night variations
4. Electromagnetic field – a contactless coil in a cage clamp clipped around a cable powers the meter and measures the line current

For each of these sources, there are different energy converters with different power parameters. The type of energy generation, together with the corresponding power yield, decisively determines the possible sensor applications. 

Improved Sustainability

Thanks to this energy harvesting technology, radio sensors are becoming sustainable because they don’t even need cabling or battery power, which is not only environmentally friendly but also saves costs. Replacing a single battery in an industrial environment typically costs $300 US dollars. Although battery replacement in itself is a relatively fast process, traveling to the site, locating the sensor, testing the device, and documenting the process all dramatically increase the labor costs. Very often, batteries are said to have a service life of several years, but in practice maintenance companies are often replacing them every one or two years, at the latest, in order to avoid early failures.

Resource-saving and environmental protection are also becoming increasingly important; the prices for copper are steadily going up and the harmful components, as well as safety aspects, of batteries are a serious problem. Wireless energy harvesting sensors are a sustainable solution that take both the financial aspect and the effects on the environment into account.

In Operation for The Industry

Sensors have a key function in industrial production. They can be used, for example, for quality and process monitoring or condition-based maintenance. The range of applications is wide and is developing in the direction of an industrial Internet of Things (IIoT) due to the increasing use of wireless sensors. By combining energy-saving radio with local energy converters, battery-free and thus maintenance-free sensors can also be mounted directly on moving parts or in hermetically-sealed environments, for example, for measuring the position of mechanical parts, the current consumption, or the temperature of mechanical parts, liquids, or gases.

Sensors in Quality Control

Quality monitoring is used to control the entire production process and to ensure the desired properties of the end product based on various parameters. For this purpose, environmental factors such as temperature, humidity, and air quality, or process factors such as position or temperature must be monitored.

Automated monitoring systems need data generated by sensors. To do this, however, these sensors must fit seamlessly into existing production processes and must not require special training or generate follow-up costs in the ongoing operation. This is where the integration of self-powered and thus maintenance-free sensors offers decisive advantages.

Condition-based Maintenance with Battery-free Sensors

In addition to the product, machines must also be monitored to ensure a smooth production process. These are often subject to high wear, so early identification of problems and appropriate countermeasures are important prerequisites for continuous quality assurance and protection against production downtime.

A fundamental problem of maintenance planning is the calculation of the intervals between each maintenance cycle. On the one hand, the time between maintenance dates must be as short as possible in order to detect any deviations before a major problem occurs. On the other hand, each maintenance involves high costs for personnel and idle machines.

In many cases, it is possible to gain valuable information by monitoring a few simple parameters. For example, a rise in temperature can indicate higher friction and thus wear. Wireless temperature sensors can be used for the measurement processes. Humidity sensors monitor whether water is leaking to prevent water damage. Temperature and humidity sensors also provide information on air conditions to always ensure consistent air quality.

That is why wireless energy harvesting sensors are ideal for a wide range of industrial applications. They are maintenance-free, flexible, and inexpensive to install – ideal features for ensuring not only high-quality standards but also greater sustainability in the Industry 4.0 environment.

IoT in the Factory Building

In manufacturing, IoT enables significantly more efficient, flexible, and individualized production. With the help of sensors networked with an intelligent IoT platform, it is even possible to create a digital twin, i.e. an exact virtual image of a machine throughout its entire life cycle. Digitization is also advancing rapidly in buildings. This leads to automated service processes in facility management, higher energy savings, and greater individual well-being for users. One thing is essential for both industrial processes and factory buildings: battery-free wireless sensors.