Variable Speed Drive, often abbreviated simply as VSD, is a hallmark of the compressed air world. Air compressors equipped with VSD are automatically able adjust their operating speeds to precisely match compressed air demand in real time. Pretty nifty, right? This is especially important in terms of energy savings, given that that largest aspect of a compressor’s total cost of ownership is the electricity it consumes – not the purchase price of the air compressor itself! On average, and depending on the size and type of applications, VSD technology can reduce these energy costs by 35% to 50%. Turn that percentage into money, and you’re looking at some serious savings.
What’s the Difference Between Fixed Speed and VSD Compressors?
Before we get into the nitty-gritty of Variable Speed Drive, let’s cover a few of the differences between a fixed speed and a VSD compressor. Fixed-speed compressors are usually simple(r) machines with a lower upfront cost. You turn a fixed speed compressor on and let it run at full speed until it needs to be shut off. Not a complicated concept! VSD compressors, on the other hand, are not built to be operated continuously at full speed. They do more than only running and stopping. Instead, they’re precisely matching output to the demand, making them more sophisticated compressors than their fixed speed counterparts. This means that the initial investment for these machines can be significantly higher.
When Should I Consider a Variable Speed Drive (VSD) Compressor?
Although VSD technology may sound like an ideal option for any business, it isn’t always the best solution! VSD compressors are ideal for businesses that experience fluctuating demand; think facilities that operate different processes or multiple shifts. Specific instances that may warrant compressors with Variable Speed Drive include when the demand for compressed air varies significantly between jobs; when the demand fluctuates by shift, day of week (i.e. weekends), or seasonally; or when production requires tight pressure bands. If your process is consistent in operation and doesn’t experience fluctuating demand, or if these variations are minimal, using a fixed speed compressor might be the best option.
You can also consider a solution that combines a fixed speed compressor and a VSD compressor, with the fixed speed compressor providing the base load and one (or more) VSD compressors that “trim” to meet changes in demand. And added benefit of a system with multiple smaller compressors instead of one larger compressor? Redundancy! This means that not only is either compressor is fully capable of handling the entire demand for compressed air on its own, but if one of the compressors shuts down, the second compressor takes on the full demand and production continues.
Investing in a variable speed drive compressor comes with quite a few benefits. Here are just a few:
Though VSD compressors have a higher initial investment cost, they pay back the added investment through energy savings. The greater the variation in demand, the greater the potential savings.
VSD compressors operate within a much tighter pressure band than a fixed speed compressor can attain.
They operate at lower delivery pressures while still maintaining the air system’s required minimum working pressure. They are also able to deliver a more consistent discharge pressure for all the compressed air applications throughout your facility.
A VSD compressor’s net pressure can be set lower than the unloaded pressure on fixed speed compressor, and each 1 bar reduction results in 7% savings in energy.
A VSD compressor can start/stop under full system pressure. There is no need to unload, which saves both time and energy. There is also no time lost to idling and no blow-off losses that occur in normal operations.
Atlas Copco is celebrating the 25th anniversary of our VSD compressors! Want to learn more and see what VSD is all about? Visit us at www.atlascopco.com/air-usa!