Autonomous sensor nodes: live from inside the silo

Good silage is truly the basis for efficient biogas production. Thanks to autonomous sensor nodes from Fraunhofer IZM, it is now possible to monitor data from directly inside a silo and thus to keep an eye on the ensilage process.

© Fraunhofer IZM
A ball with hidden features. A very robust housing protects the sensors against the high pressure in the compressed silage.
© Countrypixel
Sensor system for monitoring of the ensilage process in biogas production.

Ensilage is a tried-and-tested method of using fermentation to make substrates (usually corn) durable for biogas plants. The crushed plant material is placed in the silo and compressed; the silo is then sealed airtight in order to prevent the spread of anaerobic microorganisms such as bacteria, yeasts, or fungi. Lactobacilli, on the other hand, are very happy in this environment and turn into acids (most lactic acid) due to the presence of sugar. The better the ensilage process, the more efficiently biogas can be produced.

Detecting disturbance variables early

Previously, there have not been any suitable methods to monitor the entire process from starting up the silo to removing the finished silage. Researchers at the Fraunhofer Institute for Reliability and Microintegration IZM have developed a seamless monitoring system together with the Julius Kühn Institute (JKI) and Esys GmbH. Autonomous sensor nodes make it possible, for the first time, to collect measurements directly inside the silo and to use this method to monitor critical parameters such as silage density when the silo is started up. Disturbance variables during the ensilage process and after removal can be detected early, before the quality of the silage is affected. The team used pre- tests to determine suitable sensors for measuring pH value, temperature, and density as well as designing a low-energy signal processing system and developing an extremely robust housing that can both withstand the high pressures inside the compressed silage and hermetically seal the outward sensors from the sensitive electronics. Project staff from the JKI developed a model silo for the sensor calibration.

Connection to established harvest management software

The communication concept includes a wireless connection between the sensor nodes and an Internet bridge equipped with a cellular network connection that forwards the data to a web server with a database. This system is being developed by Esys GmbH. The results can be called up using a web API. An Android app for mobile use offers geographic online representation of the measurements. The use of a software standard that is common in harvest data management also ensures that the sensor data can later be integrated into established agricultural software solutions and thus put into practical use straight away. After the first successful sensor tests, a practical test within the real operation of an ensilage cycle is imminent.

 

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