Global: Slower, Steadier Storage Fans Cut Fan Energy by 33–45% in Idaho Research

Many potato storages were designed for 18 to 25 cubic feet per minute per ton, but much less airflow is typically needed after the crop has been cooled.

Older guidance handled that surplus capacity by switching fans on and off. A 1976 University of Idaho storage guide stated that ventilation “need only to be intermittent” and advised running fans only when the ventilating air was cooler than the bottom tubers in the pile.

Variable-frequency drives instead run fans for longer at reduced speed, and physics favours this. Under the fan affinity laws, airflow changes in direct proportion to fan speed, while power changes with the cube of the speed change. University of Idaho researchers reported that at half speed a fan delivers about half its airflow while the motor consumes only about 15% as much power.

An Idaho study reported energy savings ranging from 33% for potatoes stored 60 days up to 45% for potatoes stored more than 125 days, and a 1995 study in Maine estimated savings of 55–60%. Two years of University of Idaho testing found that variable-speed fan control can reduce energy use by up to 50% compared with conventional fan control.

University of Idaho research also concluded that a low, constant airflow is more desirable than periods of high airflow followed by periods of no airflow.

The researchers noted that variable-speed control is best suited to storages with airflow volumes of at least 15 cubic feet per minute per ton.

Sources: Bohl, Oberg & Kleinkopf, University of Idaho, Potato Progress, 2002; Potato Business, 2021; U.S. DOE Better Plants fan training, 2023; Spudman, 2023