Amber Waves of Grain in Argentina: Siloed, Moist and Shiny

If you are an integrator of IoT solutions and find yourself confused about the differences in the technology, I recommend following Harald Naumann on LinkedIn (News - Alert). Harald is the Founder of Antennity, and he is not shy about sharing his analysis of various technologies.

Harald is also insightful about practical problems in various vertical applications. His recent post is about problems in storing grain in Argentina and using IoT to monitor the grain.

Warning: This is about to sound a little pitchy, but I will try to curb my enthusiasm for Harald and focus on the problems with grain storage.

The goal in storing grain in silos is to maintain a steady consistent quality of grain that is relatively dry and at a consistent temperature. Unfortunately, there are several obstacles that need to be monitored and addressed in a short period of time. Let’s break them down in no particular order.

• Silos: water seepage may happen in a poorly maintained silo, which will lead to inconsistent grain quality, as germination is likely to happen in the moist areas. The warping of the silos’ shape because of improper loading of grain can lead to the complete collapse of the silos’ structure. A silo may also develop a convection air flow pattern where the cool air travels down along the walls, and heat rises in the center, causing temperatures to exceed recommendations.
• Worker safety issues: These include situations like workers sinking (like quicksand) in the grain, or dust from loading into silos leading to explosions. If the grain is fermenting, it can produce nitrogen dioxide and carbon dioxide, which is particularly hazardous, since it confined to a finite space. Of course, there are also the “normal” issues of working with heavy equipment and at some heights.
• Insect infestation: This can happen in a variety of ways and can increase over time, as warmer temperatures will cause the insects to breed. The insects can represent a deadly cycle as they, themselves, can add to the heat.
• Proper monitoring of moisture and temperature: This is, perhaps, the most important factor, which I view as “the canary in the coal mine” in the silo, but its hard to get a signal from the sensors. If the grain is too moist, it dampens signals, which are then unable to reach the gateway. On the other hand, the grain itself can act as reflector, diffusing the signal and blocking it from reaching the proper destination.

Harald elaborates:

“A sensor buried five meters deep has two enemies to contend with:

• Moisture in the grain (up to 18% when stored in damp conditions) dampens radio signals like a sponge.
• Grain particles reflect radio waves, causing destructive interference in the nearby field.”

Another problem is geographic as the remote silo locations in Argentina's pampas often have no mobile phone coverage, satellite uplinks are not yet available everywhere, and battery replacement at a depth of 5m is uneconomical – it’s recommended that LPWANs have a 10+ years of battery life is a must.

Other recommendations include.

• Self-healing network with redundant data paths Gateways at the edge of the silo forward data via low-earth orbit satellites.
• 868 MHz penetrates grain masses better than 2.4 GHz.
• IP67-certified sensors with conformal-coated antennas prevent corrosion from condensation.
• Silo sheet metal walls create uncontrollable reflections.
• Moist grain reduces effective antenna bandwidth by up to 70%.

Antennity's solution goes further and provides a hybrid approach that includes:

1. Local NeoMesh network (868 MHz) → Data hopping between sensors
2. Satellite gateways on the silo providing the uplink sky
3. Edge computing to provide Local data pre-processing.

Antennity prides itself on solving connectivity with customized antenna solutions for extreme environments.

Harald is also about to publish the LPWAN Cookbook which you can preorder on his site.