Understanding the Total Cost of Compressed Air

Investment costs are fixed and include the purchase price, infrastructure expenses, installation and insurance. Investment costs are determined by both compressed air quality level and depreciation period. Energy expenses include annual operating time, degree of load/unload utilization, and the unit energy cost.

Below is a list of various components you'll encounter and how they impact the overall cost of compressed air systems.

• Air compressors - This is the machine itself. As noted above, the initial price tag only accounts for a tiny amount of the total cost of ownership. Since energy makes up most of the overall cost, investing in the most efficient machine makes sense.

• Dryers and filters - These components are especially important for sensitive applications like food and pharmaceuticals as they pertain to air quality. You'll want the right solution for your industry to guarantee standards are met.

• Drains - Intelligent zero-loss drains discharge the accumulated condensate of a compressed air system when needed. This will save energy, as opposed to timer drains that drain on a selected time interval, even when there is no condensate. 

• Piping - An adequate piping system eliminates air restrictions, pressure drops, and can reduce air leakage.

• Air receiver tanks - A related issue is the use of receiver tanks that store compressed air. If properly sized, this can eliminate false demand on your compressed air system and the need for additional compressors. It also helps reduce system pressure changes. 

• Air leakage - While many inefficiencies can be eliminated even before a system begins operation, it is essential to constantly monitor equipment. That includes the detection and repair of expensive air leaks.

• Central controller - In systems featuring more than one compressor, central controllers can play a major role. They can reduce the average pressure band, control compressor capacity, and regulate the compressor speed. 

• Energy recovery - Most of an air compressor's waste heat can be recovered and used in other areas of an operation. For example, to heat rooms, water or production processes.

When making calculations, applying the overall power requirement concept is important. All components involved in a compressor installation should be considered, including inlet filters, fans, dryers, separators, and energy recovery. To compare options, it's best to use International Organization for Standardization (ISO) standards.

Working pressure directly affects power requirements. Higher pressure means more electricity consumption. In fact, each 1 bar increment requires around 8% of power. Increasing the working pressure to compensate for pressure drop always results in impaired efficiency.

Generally, these pressure drops occur due to an inadequate pipe system or clogged filters. It's advised to investigate these factors before increasing compressor pressure. With installations fitted with several filters, the pressure drop can be significant and costly if such maintenance concerns aren't addressed.

In many installations it is not possible to implement large pressure reductions. However, the use of modern regulation equipment allows pressure to be realistically lowered by 0.5 bar. This method creates a slight power savings. While seemingly insignificant, this reduction impacts annual expenses.

Most compressors come equipped with onboard controls and regulation systems. If you run more than one machine, you can also add remote monitoring and central controls. Doing so will help optimize your entire system and ensure you're operating at peak performance. With this, motor speed regulation is a popular energy-saving method due to its substantial potential.

Some monitoring tools can also pinpoint areas of inefficiency. This information is helpful in determining leakage, worn equipment, poor filtration, and improperly configured components. As pointed out earlier, these maintenance issues can increase the overall cost of compressed air systems.

Frequently, leakage can amount to 20% of compressed air flow production. Leakage is also proportional to working pressure, which is why one method is to repair leaking equipment and lower the working pressure. Reducing pressure by only 0.3 bar reduces leakage by 4%. If the leakage in an installation of 100 m3/min is 12%, this reduction represents a savings of approximately 3 kW.

You'll also want to consider when you actually use your equipment. If a small amount of compressed air is used during nights and weekends, you may want to install a small compressor for these times. This segmentation can be achieved with shut-off valves. 

If a particular application needs a different working pressure, you'll need to determine whether centralized or split production makes sense. Sectioning off your compressed air network is also useful for segmenting between high and low peak times. Such planning should be based on airflow measurements.

Using a modern master control system, as described above, the compressor central plant can run optimally for different situations. Selecting the right regulation method encourages energy savings with lower overall system pressure and optimal utilization. These controls can also reduce downtime by spreading workload evenly.

Also, central control allows you to program automatic pressure reductions during off-peak times, like nights and weekends. As compressed air consumption is rarely constant, the compressor installation should have a versatile design. A combination of compressors with different capacities and speed controlled monitors should be implemented.

It's possible to utilize recovered air compressor waste energy to fully or partially replace external electricity, gas, or oil for heat. Decisive factors include energy cost in €/ kWh, the degree of utilization, and the amount of additional investment necessary.

A well-planned waste energy recovery system often produces a payback within 1-3 years. Over 90% of the power supplied to the compressor can be recovered in the form of valuable heat. The temperature level of the recovered energy determines possible application areas and, therefore, its value.

The highest degree of efficiency is generally obtained from water-cooled installations. This works when the compressor installation's hot cooling water outlet is connected to equipment demanding heat. For example, the existing heating boiler's return circuit.

Recovered waste energy can be utilized year round. Different compressor designs have different prerequisites. In some situations requiring a large and peaking heat flow, long heat transport distances, or varying requirements, you can also sell recovered energy. Learn more about energy recovery in compressor installations.