18 



The data in Table 2 indicate that a total energy savings of 40% is possible 

 if evaporator fans could be turned off half of the time. Total savings approach 

 60% when fans ire off 16 hours out of 24 hours. Based on early research by 

 Smock and later reports by Yost (5) half-time reduction in fan operation is 

 feasible and causes no detrimental effects on stored fruit quality or condition. 



Table 2. Daily energy use and potential energy savings through fan cycling 

 in 120,000 bushel CA storage 



During storage trials (1), we investigated the efficiency of high velocity 

 direct throw air handlers presently used in CA storages. (Efficiency is defined 

 as the quantity of air returning through pallet runner openings conpared with 

 the total quantity of air delivered from the evaporator discharge). When 

 efficiency measurements were made in a 30,000 bushel CA room, 70% of the 

 discharge air never passed through the stacks; it simply short-circuited over the 

 top of the bins and back to the evaporator. When air flow was reduced 50% by 

 turning off half the fans, the return air flow decri;ased only 22%. Since the 

 measured return flow coming out of the stacks was still uniform over the entire 

 room, we concluded that half of the evaporator fans could be safely shut down 

 after field heat was removed and the CA room was sealed. 



Control Strategies 



The energy crisis of the 1970s prompted eastern growers to begin using 

 evaporator fan cycling to save energy. The first storage operators to employ 

 fan cycling simply turned their refrigeration systems off at night and back on 

 again in the morning during the winter. Research studies (2,4) indicated that 

 tennperature variations on the order of +^ 1**F from the set point would be 

 expected when systems were turned off for 12 to 14 hours. We found these 

 variations to ho, greater than those experienced when refrigeration systems 

 operated continuously. Since fruit quality and condition after CA storage in the 

 cycled rooms was equivalent to that in rooms operated continuously, the cycling 

 practice became widely accepted. 



