Back to Basics

Published online: Jan 24, 2022 Articles, Potato Storage Ken Young, Director of Product Quality, Agri-Stor Companies
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This article appears in the January 2022 issue of Potato Grower.

I recently came across a news story about a newly constructed, state-of-the-art potato storage. It was a good article. You could feel the excitement and pride shared by both the new owner and the builder. Potato growers everywhere would envy this storage. It promised to deliver everything a pile of potatoes would ever need to make it through the storage season in great condition. I have personally visited this storage, and it really is a nice building with good controls. Plenty of bells and whistles. But I’ve had to ask myself: Is this storage designed for high performance? 

What are the qualifications of a “high-performance” storage ventilation system? Can those qualifications be verified? Are traditional storages too archaic to function well? Do they just point fans toward the pile and hope the air gets where it needs to go? What criteria are used to compare storages with different ventilation system designs?

The goal of the Agri-Stor ventilation system is high performance. I like to think of performance as something that can be measured. In his book The Effective Executive, business author Peter Drucker famously states, “If you can’t measure something, you can’t manage it.” His book obviously refers to success in business management—and I doubt he knew about or wrote about potato storages—but the principle applies wherever performance must be evaluated. It is impossible to evaluate success if there are no metrics.

Successful ventilation systems need to be measured to verify they’ll be able to create and maintain a uniform climate within an acceptable range. Performance can be assessed with just a handful of specific measurements, which, of course, have an acceptable range of variation. That being said, the better the system, the tighter the climate controls. Specifically, I want to be able to evaluate performance in the following key areas:

  • Ventilation rates
  • Temperature control
  • Humidity control
  • Post-harvest crop protection applications / Purgeability
  • Automated Controls

Ventilation Rate

The ventilation system should deliver precisely the right volume of air at precisely the right speed in a uniform fashion. To verify performance of the ventilation system, measure speed at the discharge holes with a handheld anemometer. It should be uniform across all the discharge holes. If the discharge holes cannot be accessed, measure air speeds at the duct entrances. Again, ensure uniformity in every duct. Run this test at upper and lower fan operating speeds.

Temperature Control

The internal temperature should be maintained consistently within a few tenths of a degree of the temperature set point. First, routinely verify the accuracy of all internal and external temperature sensors using a calibrated thermometer. Use a handheld thermometer to verify the temperature of the air in the duct entrances, preferably while the system is running. Check the pulp temperatures of potatoes near the ducts. Finally, review the history logs in the control panel. The plenum temperature history log will show the level of variation in air temperature going through the produce.

Humidity Control

Make sure the relative humidity of the delivered air is maintained within a couple percent points of desired levels. This is more difficult at high relative humidity (greater that 90%)—not because high humidity is difficult to maintain, but because RH sensors are not as reliable at the high end. Still, storage operators need to verify plenum humidity with a handheld sensor in the plenum (again while the system is running). As before, consult the control panel history log for signs of significant variation.

Post-harvest Crop protection Applications/Purgeability

The ventilation system must have the ability to remove the gases generated from produce respiration. It must also be able to apply and circulate post-harvest crop protection applications effectively. In potato storages especially, I carry a CO2 sensor since many are not equipped. It’s important to verify that levels fall below the established upper limits in the plenum and over the pile. Gases will settle when the fans are off, so this test is best performed while the system is running. History logs should be reviewed for any evidence of large deviations from acceptable conditions.

Automated Control

Ensure the system can automatically make adjustments in order to maintain the desired climate, as well as communicate remotely with operators and be controlled remotely. Automated control isn’t a measurement but can be assessed by asking a few simple questions:

  • Does the history log show significant variations in the above key metrics?
  • As the system changes modes and adjusts to changing outside weather conditions, does the internal climate struggle to remain constant?
  • Is the control panel easy to use?
  • How responsive is the app or desktop software?
  • Am I getting enough information remotely for it to be helpful?

In essence, whether it’s an old storage or a shiny new one, performing routine inspections to “measure what matters” is key to maximizing the money spent on storage costs. Most of the time, even poorly functioning storages can be improved with a few strategic component upgrades or modifications. It really is all about controlled climate and design.

Recent technological advances in storage design are exciting. Storage professionals like the team at Agri-Stor work hard to combine properly engineered designs, certified ventilation components, and scientifically supported best practices, meeting the demands of produce storage in a wide variety of climates.