When discussing the cost of compressed air, it’s worth mentioning that electrical energy makes up most (80%) of your compressor-related expenses. As a result, many compressed air installations offer significant energy-saving possibilities including energy recovery, pressure reduction, leakage reduction, regulation systems, and controls and features. You’ll also want to pay attention to compressor size.

Determining the 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 utilisation, and the unit energy cost.

Planning your system

When investing in new equipment, it’s best to look at both your current needs and planned expansions. You’ll also want to consider factors which might impact the compressed air installation, including environmental regulations, energy-saving opportunities, production needs, and planned growth.

Optimising compressor operations are important for large, compressed air-dependent industries. If you work in a developing industry, production will change over time, which includes operation conditions.

Based on our experience, an extensive, unbiased analysis of your operating needs will greatly help reduce overall costs. Therefore, it’s important that your compressed air supply matches actual demand while leaving room for future expansion.

Components of a compressed air system

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.

Understanding your power requirement

When making calculations, applying the overall power requirement 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 the International Organisation for Standardisation (ISO) standards.

Working pressure

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.

How to reduce energy costs and save

As mentioned above, energy expenses are the dominating factor of the overall cost of compressed air. In fact, they can make up to 80% of owning and running a compressed air system. Therefore, it’s important to focus on the most efficient solutions to meet your demands.

Although the most advanced equipment comes with higher initial investment costs, it’s usually worth it for overall savings. An ideal situation is when a compressor’s capacity meets your application’s air consumption. There’s also variable speed drive (VSD) equipment to meet different pressure needs.

Optimising equipment

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 optimise 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 centralised 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.

Regulating your system

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 utilisation. 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.

Energy recovery

It’s possible to utilise recovered air compressor waste energy to fully or partially replace external electricity, gas, or oil for heat. Decisive factors include energy cost in Rs/kWh, the degree of utilisation, 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 utilised year-round. Different compressor designs have different prerequisites. Depending on some situations, such as a large and peaking heat flow, or long heat transport distances, or other varying requirements, you can also sell recovered energy.

This article is extracted from the Atlas Copco website. Link to the original article is here: https://www.atlascopco.com/en-us/compressors/wiki/compressed-air-articles/cost-of-compressed-air