How efficient are your air compressors?
When compressor manufacturers talk about how ‘efficient’ their air compressors are, they are generally talking about the ratio of energy in versus compressed air out. Known in the industry as Specific Power, a typical fixed speed rotary screw air compressor will consume around 6.5kW – 7.0kW of energy per cubic meter per minute of compressed air delivered to the plant (kWh/m3/min)
Despite claims to the contrary, most industrial grade air compressors have similar levels of efficiency in terms of Specific Power. That is, if a fixed speed air compressor runs 100% loaded for 100% of the time, its energy consumption will match that of the Specific Power rating
In reality, air compressors don’t run in perfect conditions, they run to match plant demand. As demand increases and decreases throughout the day, the compressors ability to react to that demand is where energy efficiency often goes out the window, along with the Specific Power ratings
Multi Compressor Systems
Most industrial compressed air systems consist of multiple air compressors. Often by design, but sometimes as a result of organic business growth, the compressors need to work in tandem to ramp up/down as plant demand varies.
What is system specific power?
System Specific Power is a more appropriate term for multi-compressor installations and better reflects the overall efficiency of a compressed air system. Simply put, System Specific Power is a function of the total energy consumed by all equipment versus the volume of compressed air delivered to the plant.
Air Compressor Control
Without proper control, System Specific Power consumption can spiral out of control, leading to a situation where a bunch of ‘efficient’ air compressors are collectively consuming much more energy than they should
On-board compressor controllers are designed to control a single machine. That is, they monitor and regulate the compressor to maintain a given pressure range. Multiple air compressors means multiple individual controllers that don’t effectively communicate with each other.
NO CONTROL = OUT OF CONTROL
Typically, multi-compressor installations are set up in a cascade arrangement, whereby compressor no1 comes online at a given pressure, say 7bar, and the remaining compressors come online at pre-set lower pressures, say 6.8bar, 6.6bar, 6.4bar and so on
This rudimentary method of control is inherently inefficient, as overall system pressure needs to be artificially higher than necessary to meet the minimum plant pressure. The more air compressors in a system, the wider the pressure band. For every additional 1.0 bar pressure, there is an energy penalty of around 7%
An intelligent Compressor Control System will bypass the on-board controllers and collectively manage the air compressors to react to a single pressure sensor. This means reduced system pressure and energy consumption. Further, a controller intelligently selects the most efficient group of compressors to run at any given time, to match plant demand and reduce energy waste by running the wrong compressor at the wrong time.
COMPRESSOR CONTROLLERS CAN REDUCE ENERGY CONSUMPTION BY AS MUCH AS 30%
Energy consumption is by far the greatest cost associated with owning an air compressor (around 70%). Intelligent compressor control and monitoring systems reduce energy consumption by;
- Reducing system pressure
- Reducing or eliminating unloaded running
- Reducing equipment downtime
For an obligation-free assessment to determine how intelligent compressor control and monitoring can help you, get in touch.