Compressor energy saving is more than just hot air

With the cost of electricity set to rise even further, there has never been a more critical time for manufacturers to look at solutions that will save both energy and money.

Air compressors represent a significant portion of most manufacturer’s electricity consumption, however many companies are unaware of how much money that really is. 

For example, a 90kW air compressor that is sized with 20% extra capacity could be costing the user over $140,000* a year in electricity to operate. 

To reduce this figure, the first step is to understand what the user’s costs really are.

Using Atlas Copco’s air measurement tool and associated simulation software, our highly trained sales engineers can accurately measure the electrical consumption of compressors on site and then accurately simulate the saving against this consumption using modern Variable Speed Drive (VSD) technology. 

Our VSD technology has been proven to save an average of 35% of energy consumption compared to standard load/unload compressors.

Using the 90kW example, VSD technology is able to provide savings of $49,000 a year, every year, over the life of the compressor. Over a 10 year period that can add up to $490,000 in savings.  

As a pioneer of VSD technology in the early 90s, Atlas Copco has continued to refine the technology over four generations of improvements. 

Atlas Copco’s integrated VSD solutions incorporate dedicated VSD motors that can  handle eddy currents generated by varying the power frequency, plus as they are designed to work with the VSD control system incorporated in the compressor they can be slowed as low as 20% of full speed, something standard motors struggle to achieve due to insufficient torque at low speeds. 

Added to this, should the compressor actually stop Atlas Copco’s VSD separator vessels don’t need to blow-off and waste valuable air like traditional and other VSD compressors before restarting.

Atlas Copco compressor motors are specifically designed to provide high torque at slow speeds so the motor can readily start against high back pressure.

VSD components fully integrated

With EMC compliance as standard, the VSD components are fully integrated into the Atlas Copco control panel. 

To control the VSD, the compressors feature a fully integrated, in-house designed Elektronikon controller that controls the operation of the VSD plus the operation of the entire compressor. 

For fixed speed machines, the Elektronikon control module has the ability to save further energy with several control algorithms built into the operating program. 

For example, the delayed second stop algorithm provides additional savings by monitoring and predicting future operating variables; stopping the compressor as many times as possible without affecting the longevity of the motor. 

Further energy savings are made through the fan saver algorithm, which monitors the compressor temperature and turns the cooler fan off at lower temperatures. 

Starting current and power factor

For some manufacturing operations, the starting current and power factor can make a significant difference to the current supply required for the site and to the compressor. 

In some cases, a high starting current and low power factor can result in a required upgrade to the power supplied to the site, adding cost and time. 

Add to this the fact that some electricity providers base their billings on the peak current reached, meaning the current peak provided by traditional compressors, utilising star delta start, can increase the overall energy cost per kWhr. With VSD, the current never exceeds the compressor’s full load current.

Multi compressor control systems are also an important consideration when there are two or more compressors working together to meet the required plant air demand. 

With every 1 Bar of pressure drop adding 7% extra energy consumption, the Atlas Copco ES Control system helps reduce the operating pressure band and further save energy.

The ES control system is built into the Elektronikon controller and provides a load sharing platform ensuring each compressor operates for equal hours, consolidating service costs and ensuring users get the most out of their compressors equally.

The set up of the compressor’s dryer system can also make a significant difference in the energy consumed. Unlike traditional systems that utilise a free standing external dryer, Atlas Copco offers Full Feature (FF) machines with the dryer incorporated into the compressor, saving space and installation costs.

A less obvious benefit of the innovative design is that FF machines save on pressure drop, with the system’s pressure measured at the outlet of the dryer and not the compressor.

Having the dryer integrated to the Elektronikon controller means that the compressor can control the dryer and turn it off when the compressor turns off, unlike separate dryers which will run all day, every day, unless manually turned off. 

Added to this, the Elekronikon dryer algorithm will monitor ambient temperatures and ensure that a relative humidity of less than 50% is achieved whilst minimising the dryer use.

The FF machines also offer a fully integrated filtration system, which can reduce pressure drop and save energy costs even further.

The FF compressors are designed to operate in some of the world’s harshest environments; up to 46degC ambient temperature as standard and up to 50degC with the addition of the High Ambient option.

To further save energy, Atlas Copco compressors are available with a simple to install and effective to use energy recovery system, available as a stand-alone unit or integrated. 

With around 90% of the energy used to generate compressed air dissipated as heat, the innovative energy recovery system utilises this wasted heat energy for space or hot water heating.

Atlas Copco compressors are designed to be at the forefront of energy efficiency with in house designs that are continuously improved ensuring that they stay that way. 

* Estimate based on compressor operation at $8,000 hours a year, sized to 80% capacity, $0.25/kWhr. Does not consider losses due to unloaded power consumption and does not consider complete system power.

[Jeff Treble is business line manager, Industrial Air Division, Atlas Copco.]