New technology out of Saskatchewan hopes to nail down the ideal time for aeration and automate fan operation.
Ron Palmer, of the Indian Head Agricultural Research Foundation, has released two projects, a bin-specific online calculator to determine if air conditions are right for drying and new software that monitors air going in and leaving the bin, switching fans on and off as conditions change.
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Palmer bases his work around absolute humidity, or the actual grams of water per cubic metre of air, using a function of relative humidity and temperature. If outside air has a lower absolute humidity than bin exhaust, air moving through the grain is removing moisture. If exhaust has a lower absolute humidity than air outside, grain is being wetted, the researcher said.
Farmers can measure exactly how much moisture they have removed, Palmer said, by multiplying the difference between outside absolute humidity and bin exhaust (how much moisture is removed per cubic metre of air pumped) with airflow.
“People have to realize what’s going on with drying,” Palmer said. “There’s actually a battle going on between the grain, which is trying to push the moisture out, and the air surrounding the grain that’s trying to push the moisture back into the grain. It’s a vapour pressure, so what we’ve got going on here is a little vapour war going on between the grain and the air surrounding it. If the grain has a higher vapour pressure than the air surrounding it, then the water’s going to go from the grain into the air and drying will occur. If the air has a higher vapour pressure than the grain, then it’s going to push water back into the grain and we’re actually going to be wetting our grain down.”
Palmer’s online calculator reveals how high relative humidity can get, given current bin conditions, before grain does not dry.
The application, available for free at www.planetcalc.com/4959/, takes grain moisture content, grain temperature and outside temperature and produces a list of relative humidity thresholds for various crops. If relative humidity outside the bin falls below that threshold, conditions are good for drying.
For example, if air outside is 25 C, grain inside the bin is 20 C and grain moisture is 12 per cent, the calculator estimates that relative humidity should be lower than 50.9 per cent for oats, 41.8 per cent for shelled corn, 34.7 per cent for soft winter wheat and either 60.7 or 62.3 per cent before canola will dry, depending on the method used to calculate equilibrium moisture content (EMC).
EMC represents the point where grain and air moisture is balanced and is often used to predict how natural air will affect moisture content.
Palmer is not the only one to target drying windows with technology.
BINcast, another free online program through Weather INovations Consulting, a division of Glacier FarmMedia, pulls in a region’s weather forecast and converts it to EMC for a list of grains.
Farmers are asked to mark their location and crop and the program generates a list of forecast temperatures, relative humidity and EMC values for the next five days.
“That is a good guideline,” said Joy Agnew, Agricultural Research Services project manager with the Prairie Agriculture Machinery Institute. “It’s a great guideline, actually, and it’s based off the standard equilibrium moisture content equations for each of the grain types. The trouble with that is it does not account for the effect of grain temperature.”
EMC calculations will be off if it is calculated using air temperature, but grain temperature is significantly different, she said, since EMC will change when air hits the grain.
That gap is addressed in Palmer’s model, she added, but noted that the new software is still obscure and hard to find online.
Palmer, however, pointed out that his program deals with existing conditions while BINcast deals with forecasts and uses a predictive model.
Bringing in automation
The calculator may promise the best drying environment, but the time needed to constantly check bin conditions will make it a hard sell for producers.
Palmer tested bins every 10 minutes in his own experiments and, while the average producer would not need that level of detail, he recommended at least an hourly check to deal with rapid air changes.
That is unrealistic for many farmers, Palmer acknowledged, one of the reasons that his latest project has turned to automation.
Palmer partnered with Regina’s IntraGrain after creating an algorithm that calculates current drying potential and turns fans on and off accordingly.
The software uses sensors to determine relative humidity and temperature both outside the bin and leaving through bin exhaust. The algorithm then calculates and compares absolute humidity for both, determines if conditions are good for drying, and controls the fan.
“If there’s 10 grams of water coming out and there’s two grams of water going in per cubic metre, then the difference is how much we’re drying,” he said.
The system can still be run if bins only have temperature cables, not relative humidity sensors, Palmer said, but EMC tables would have to be used.
His work was put to the test this year. The algorithm was used to control aeration on two 20,000-bushel bins of yellow peas north of Indian Head, as well as several bins at the Indian Head Agricultural Research Foundation’s experimental farm.