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.
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.“