Recommendations for Grain Aeration

I have 11 recommendations for aeration.  These are conclusions that I have reached after considering all that I have learned in the past years from the data collected and analyzed, farmer discussions,  and practical considerations.

  1. All steel grain storage bins should be equipped with aeration storage bins.  To prevent spoilage, the grain must be cooled, even if it is dry.  The stored grain is very valuable, and cooling the grain is a very cost effective means of ensuring its safety and protecting its quality.  Even if the bin is not near grid power, a gen-set could be used to power the aeration fan for a couple of days to cool the grain.
  2. Smaller fans could be used.  We don’t really need the 10 or even 5 HP fans. One, two and at most 3 HP fans will do.  There are many advantages to do this.
    • Reducing the fan size from say 5 hp to 1 hp, does not reduce the airflow by the same ratio. The airflow might be halved.  If our main concern is to cool the grain, then the cooling might take twice as long — instead of taking one night to cool, it takes two. So what. But the power we use is only 2/5. We save power.
    • The infrastructure of installing large power sites is reduced tremendously.
    • Lower capital costs.  A one hp fan is obviously much less than a 5 HP.
    • A smaller fan is more portable.  One fan can be shared with many bins.
    • A smaller fan creates less pressure, which in turn causes less difference in top to bottom temperature, (from compression) and less difference in top to bottom moisture content.
  3. Open bottom screen.  I have observed a loss of 1 inch of water, or more going across the screen.  What a waste.  An open bottom screen would essentially reduce this loss in pressure to zero.
  4. Fan on first day and night until 9 the next morning.  We observed time and time again that we got as much as a 1 % reduction in Moisture Content in the first 24 hours.  This was even more evident when the grain came off the field hot. The fan should be turned on even as the bin is being filled.  We want to get the grain cooled down immediately.  Stop the spoilage as soon as possible.
  5. If no sensors and no knowledge of anything, not even the MC or temp of the grain, then use the YardLight Rule to turn the fan on. “On at night, you are bright; on during the day, you will pay”
  6. If we know just a little bit — let’s say the Grain Temperature and the Grain Moisture Content; then one can use the Calculator to determine if drying will occur:   www.planetcalc.com/4959/
  7. Many farmers have a temperature string in their grain, and they don’t know anything else.   The moisture content of the grain is unknown.  We do know the temperature of the air outside and its relative humidity.   We should then turn the fan on if:    Air Temp Outside < Grain Temp   AND   the RH outside < 80%  Better yet this simple algorithm should be realized with electronics that does this comparison continuously and controls the fan automatically.  This control algorithm is slightly less effective than the Absolute Humidity Controller BUT it is simpler, less costly,(requires no math or computer), and is more reliable. A simple thermistor in the bin will provide the temperature, and the temp and RH can easily be measured right at the fan. The electronics consists of a comparator and an actuator.   This would be my choice for an automatic controller, even though the optimum controller is theoretically the Absolute Controller.   The Absolute Humidity Controller requires the Grain Temp and RH as well as the Outside Air Temp and RH. The RH of the grain can be measured with a sensor, but it is not that accurate, and can easily be damaged with dirty air AND these sensors are much more expensive than the temperature sensor.  The other way of obtaining the RH of the grain is through EMC equations, but then one must know the grain type, the temp of the grain, and the MC of the grain.  This requires a computer.  More money, more complication, and therefore less reliable.
  8. Cool grain til January, then seal the bin until July.  Let the grain warm up naturally through the walls of the bin.  And then if you are going to store the grain for another year.  Unseal the bin and apply the fans using #7 until January. This will keep the grain as cold as possible, with the least spoilage.
  9. To obtain the temperature of the grain, two thermistors should be placed in the center of the bin, just a little higher than half way up.  Why two thermistors?  For reliability and validation.  If the two thermistors are reading the same value, then you can be assured that you have a reliable temperature value.
  10. The bottom always dries first, so one could remove a couple of hundred bushels from the bottom after a week or so.   Especially if the grain went in with a MC that was more than 2 points higher than dry.   In taking out the dry grain at the bottom, it would invert the cone at the top, and lower the overall depth as well as providing some mechanical movement, all to enhance the drying.
  11. Supplemental Heat might be need for MC more than 2.5 points above dry.   Use the natural bounce of the day by pumping energy into the grain during the day, and then by cooling and drying at night.  Also consider using #10 with this.

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