Variable speed screw air compressors keep your energy costs down by only generating the compressed air you need. Here’s how they work
11 mar 2020
Air demand fluctuates in almost every production environment. After all, not every company operates at full capacity every hour of every day of every year. Major manufacturers might, but small and medium-sized businesses nearly all have periods during which production is lighter.
That is why it makes no sense for a compressor to produce as much air on the busiest production day as, for example, on a holiday. However, that’s precisely what many fixed speed screw air compressors do. That might work in production environments where the air demand is similar all the time, but studies have shown that the vast majority of all installations face substantial fluctuations in air demand. In more than two-thirds of them, the load cycle lies between 40 and 80%.
In most of these cases, it makes no sense to operate a screw air compressor at a fixed speed. After all, about 70% of the total life cycle cost of a standard compressor can be attributed to its electricity costs, which means that running one at a speed that produces too much air is incredibly inefficient.
Fortunately, there is a solution: Variable speed drive (VSD) compressors.
They don’t always produce as much air as you need on your busiest day. Instead, they always produce as much air as you need right now. As a result, variable speed screw air compressors significantly reduce your energy costs.
Over time, those savings quickly add up. For example, a GA VSD screw air compressor from Atlas Copco realizes energy savings of 35% on average and a VSD+ compressor achieves 50% energy savings on average.
In addition to matching the air flow of the compressor to the air demand, Atlas Copco variable speed products feature no unload.
“Unload” means the time when the compressor no longer produces compressed air and is venting its internal pressure (which is known as “blowing down”). During this unload period, the demand of the plant must be met by the stored air in the receiver(s) and piping.
However, Atlas Copco’s GA VSD+ oil-injected rotary screw air compressor can start and stop under full system pressure without the need to unload.
There are also no wasted idling times or blow-off losses during its operation, and the peak current penalty during start-up is eliminated.
To find the right model, you have to determine the peak and valley value of compressed air consumption. That helps you monitor and measure how much electricity you need to generate all the compressed air that you need. For this, you have to calculate the Specific Energy Requirement (SER), which means the amount of energy that is required to deliver 1 liter of free air delivery (FAD) at a certain pressure.
Finally, VSD screw air compressors impress with a wide turndown ratio. Turndown is the fraction of full-load flow that a compressor can handle without experiencing a surge. A wide turndown ratio means there is a large operational range between their maximum and minimum capacities.
With all of these benefits, it’s easy to see why Atlas Copco’s VSD screw air compressors are a popular choice for businesses across all industries.
Ask an air system professional about the best options for your needs.