How can you conduct an energy audit for a compressed air system?

1 Prepare for the audit

Before you start the audit, you need to gather some information and equipment that will aid in assessing the current performance and condition of your compressed air system. This includes the layout and schematic of the system, operating hours, pressure settings, power consumption, maintenance records, service history, production requirements and demand patterns of the end-use devices. Additionally, you need a flow meter to measure the air flow rate at various points in the system, a pressure gauge to measure the air pressure at various points in the system, a power meter to measure the electrical input of the compressors and other components, a leak detector to locate and quantify air leaks in the system, and a thermocouple or infrared thermometer to measure the temperature of the air and components.

2 Measure the supply side

The supply side of the compressed air system consists of the compressors and their accessories, such as dryers, filters, and receivers. The main objective in measuring this side is to determine the capacity, efficiency, and quality of the compressed air generation. To do this, it is important to measure the flow rate and pressure of the compressed air delivered by each compressor, as well as its power consumption and specific power (kW per m3/min). Additionally, check the load factor (ratio of actual to rated output) and control mode (e.g., on/off, load/unload, modulating) of each compressor. Furthermore, you should measure the pressure drop and dew point of the compressed air after the dryers and filters, as well as the volume and pressure of the compressed air stored in the receivers.

3 Measure the demand side

Measuring the demand side of a compressed air system is necessary to determine its actual and optimal consumption, pressure, and quality. Parameters such as flow rate and pressure of the compressed air at various points in the piping network, flow rate and pressure of the compressed air at each end-use device, operating hours and duty cycle of each end-use device, pressure drop and quality of the compressed air along the piping network and at each end-use device, and type and size of the end-use devices and their suitability for the application should be monitored. This will enable you to identify any issues or inefficiencies in your system.

5 Calculate the energy and cost savings

The energy and cost savings that can be achieved by reducing or eliminating the losses and inefficiencies in the compressed air system can be calculated by using the following formula:

Savings = (Reduction in flow rate) x (Specific power) x (Operating hours) x (Electricity rate)

The reduction in flow rate can be estimated by adding up the flow rates of the leaks, artificial demand, and inappropriate use that can be eliminated or minimized. The specific power can be obtained from the power meter or the compressor specifications. The operating hours can be obtained from the production schedule or the compressor control panel. The electricity rate can be obtained from the utility bill or the electricity supplier.

6 Implement the improvement measures

The improvement measures that can be implemented to reduce or eliminate the losses and inefficiencies in the compressed air system can be divided into two categories: low-cost or no-cost measures and capital investment measures. Low-cost or no-cost measures do not require significant expenditure or modification, but can yield immediate and substantial savings, such as repairing or replacing leaking components, adjusting or lowering pressure settings, installing or optimizing compressor control systems, replacing or cleaning filters and dryers, and installing or optimizing receiver capacity and location. Capital investment measures require significant expenditure or modification, but can yield long-term and sustainable savings, such as replacing or upgrading old compressors with new ones, replacing end-use devices with more efficient ones, replacing piping networks with larger pipes to reduce pressure drop and friction losses, and installing a heat recovery system to recover waste heat from compressors.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?