In the nineteenth century, condensers were developed for the steam engine—it was from these condensers that cooling towers originated.
Today, cooling towers lie at the heart of many industrial processes. Although cooling tower designs change from manufacturer to manufacturer, and vary in size from small rooftop towers to large hyperboloid structures that can be up to 200 meters tall and 100 meters in diameter, or rectangular structures that can be over 40 meters and 80 meters long, they all perform the same function.
They are designed to remove waste heat from water and transfer it to the atmosphere. And there are many different ways to accomplish this based how the air and water flows and on how the air is moved, whether mechanical or natural draft. Even so, fans are always used to move air through the cooling tower to cool the process water. Cooling towers provide cooled water for manufacturing, air-conditioning, and electric power generation.
This brings us to Variable Frequency Drives (VFD) and when to use them on a cooling tower. The cooling tower fan needs to be started and stopped and the speed and direction changed. With a VFD controlled fan, you can do that as the VFD operates over many speeds, adjusting the fan speed and reversing the fan rotation when required. By reducing the fan speed to match the rejected heat load requirements, you further reduce energy use.
In chiller plant applications, VFDs on the cooling tower fans can match the load and wet-bulb temperatures, helping to optimize plant efficiency.
Using a VFD on a cooling tower:
- Minimizes peak demand charges
- Eliminates motor voltage imbalance
- Maximizes the power distribution system
- Reduces energy consumption as it operates at the most efficient point
- Eliminates mechanical shock and stress on couplings, belts, drive shafts, etc.
- Saves on operating costs and energy
- Optimizes overall chilled water plant efficiency
For cooling towers, VFDs are the preferred method of capacity control. When you precisely match fan motor speeds to the required heat rejection, you not only reduce your energy consumption, but you also reduce your operating and maintenance costs.
Choose a VFD, they are cost effective to implement and will deliver maximum system efficiency.