Battery-free wireless sensors conquer the IIoT

By Armin Anders, co-founder and vice president of business development with EnOcean

Wireless and battery-free radio sensors are proving increasingly beneficial as the Industrial Internet of Things matures. They can be used directly on moving parts or in hermetically sealed environments, for example to measure the flow, pressure and temperature of liquids or gases. Above all, industrial companies save themselves time-consuming and cost-intensive cabling.

However, it is of crucial importance that wireless sensors employ energy harvesting, rather than being powered by batteries. This is because replacing a single battery in an industrial environment costs between $250 to $500 US dollars. Although the actual battery exchange happens quite quickly, the travel, locating, device-testing, and documentation increase the hourly costs enormously. Very often, batteries are said to have a service life of two to five years, but in practice they are often replaced every one to two years 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. A sustainable solution is needed that takes both the financial aspect and the damage to the environment into account.

There is a more sustainable way for wireless sensors: sensors that obtain their energy from movement, light, and temperature differences according to the principle of energy harvesting. This means that they neither require cables nor batteries for smooth operation. Therefore, they can be flexibly mounted directly on moving parts. The combination of radio and energy harvesting enables new applications entirely without maintenance requirements and battery waste.

Sensors in quality control

Quality monitoring is a key aspect of the production process in order to ensure that the final product meets predefined parameters. To achieve this goal, a variety of parameters must be monitored, such as environmental factors like temperature, humidity, and air quality; process factors like speed, force, pressure, and temperature; or material factors like the starting materials used.

Many of these parameters are suitable for automated monitoring with the help of sensors. Ideally, sensors can be optimally integrated into existing production processes and require neither special training nor do they cause follow-up costs in ongoing operations.

Maintenance-free process monitoring

The aim of process monitoring is to ensure that a defined production quantity is achieved, taking into account various parameters such as the required time, material and personnel. Deviations in the production process must therefore be detected at an early stage and failures avoided. The integration of wireless sensors in production offers decisive advantages: wireless sensors can be used, for example, in hermetically sealed environments such as pipelines to measure the flow, pressure, and temperature of liquids or gases.

Condition-based maintenance with battery-free sensors

A central aspect of quality assurance is the monitoring of machines for production. These are subject to wear, so early detection 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. 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. Examples of such parameters are temperature, as wear often leads to higher friction, which in turn shows up in a rise in temperature on the machine. Another parameter is sound; experienced employees can often detect wear on machines by means of deviating sounds. Vibrations also play a role, as the combination of wear and friction often leads to asymmetries in the machine geometry, which manifest themselves through vibrations, especially in rotating machines.

Battery-free wireless sensors open up new possibilities

It has become obvious that wireless sensors offer decisive advantages for various applications in production. However, it is important to note that these sensors must also be constantly supplied with energy. Especially when used in places that are difficult to access (for example integrated in machines, tools, pipes, etc.), the disadvantages of possible maintenance due to the need to change batteries must be carefully weighed up. Cable and battery-free wireless sensors, on the other hand, enable completely new approaches.

Battery-free and wireless sensors tick all these boxes as they are maintenance-free, flexible, and cost-effective to install. That’s why they are ideally suited for a wide range of industrial applications, such as factory automation, the food-and-beverage industry, logistics, transport and many more. This makes them great prerequisites for ensuring high quality standards in any industrial environment.