A hot summer day in Montague Gardens, an indus­trial zone in Cape Town’s suburbs. Under the blazing sun, a ther­mometer shows over 40 degrees Celsius around noon. But in the new cold storage facility recently built here by the Wool­worths retail chain, the workers are processing fresh food at a frosty two degrees. They receive large quan­ti­ties of cooled produce from regional suppliers and repackage it in smaller units for delivery to the indi­vidual Wool­worths stores. While they work, the cold chain has to be main­tained at all times. An effi­cient air condi­tioning system sees to that, and fans from ebm-papst play an impor­tant role.

Focus on effi­cient cooling

Where cooling and air condi­tioning are involved, Main­stream Refrig­er­a­tion has been Wool­worths’ estab­lished partner for all projects in southern South Africa in recent years. Richard Drinkrow, Managing Director at Main­stream Refrig­er­a­tion, explains what was most impor­tant to Wool­worths during the expan­sion of its logis­tics center: “Sustain­ability is an impor­tant compo­nent of the corpo­rate philos­ophy at Wool­worths, so we designed the entire cold storage facility for maximum effi­ciency. Water is a scarce resource in South Africa, and the energy prices rose about 20 percent in the last five years — annu­ally!” To cool the new ware­house as clev­erly as possible against this back­drop, Main­stream Refrig­er­a­tion chose its coolants and compres­sors very care­fully and also focused on effi­ciency in the fans it used.

AxiTop works quietly and effi­ciently

In each of the twelve evap­o­ra­tors that supply cold air to the facility, there are three size 800 EC fans mounted with AxiTop diffusers. “A low noise level inside the ware­house is extremely impor­tant,” says Drinkrow while elab­o­rating on the require­ments. “If we were using 36 conven­tional fans without AxiTop here, it would constantly sound as if a Boeing was landing. We can’t expect people to work in a place like that.” And the good air throw from the fan-diffuser combi­na­tion pays off very nicely in the ware­house. The fans blow the cold air over nearly 50 meters from one side of the building to the oppo­site wall. Main­stream Refrig­er­a­tion placed temper­a­ture sensors there; with them the speed of the fans and the output of the compres­sors can be controlled auto­mat­i­cally.

If we were using 36 conven­tional fans without AxiTop here, it would constantly sound as if a Boeing was landing. We can’t expect people to work in a place like that.

Richard Drinkrow, Managing Director at Main­stream Refrig­er­a­tion

The fans blow the cold air over nearly 50 meters from one side of the building to the oppo­site wall. Main­stream Refrig­er­a­tion placed temper­a­ture sensors there; with them the speed of the fans and the output of the compres­sors can be controlled auto­mat­i­cally.

Easy control via MODBUS

Since the EC fans can be easily addressed and controlled via MODBUS, their output can always be exactly adjusted to current needs. So when nothing is happening in the ware­house at two o’clock in the morning, the control system slows the fans down for imme­diate energy savings. Wool­worths also uses eight effi­cient EC fans with AxiTop diffusers on each of the four condensers on the roof. Here, too, adjusta­bility and quiet oper­a­tion play a crucial role. “There are offices near the roof, so there it’s also impor­tant that the fans don’t make any noise,” says Drinkrow.

Richard Drinkrow, managing director at Main­stream Refrig­er­a­tion, on the ware­house roof, where 32 EC fans with AxiTop diffusers are installed.

In spite of their low noise output, the EC fans combined with the AxiTops generate such a strong air flow that Main­stream Refrig­er­a­tion was able to use air-cooled condensers. “The alter­na­tive would have been water-cooled condensers,” says Drinkrow. “But since we also wanted to save as much water as possible, that wouldn’t have been the best choice.” In addi­tion, energy consump­tion can be further reduced thanks to the adjusta­bility of the EC fans. “We have seasonal temper­a­ture vari­a­tions between zero and over 40 degrees. A fan that can only do ‘on’ or ‘off’ doesn’t help us much there. We can control the EC fans precisely to adjust their output to the outside temper­a­ture.”

For Drinkrow, the good adjusta­bility of the fans and the overall system is the key to sustain­able air condi­tioning in the future. “I always compare it with a car. The main differ­ence between a car from 15 years ago and one from today is the engine manage­ment system. That’s also how I see it with air condi­tioning. With smart control systems, we can still save a lot of energy in many ways.“