Monitoring and Energy Performance of Compressed Air Systems
Canadian Standards Association C837-16 document “Monitoring and Energy Performance of Compressed Air Systems” specifies which information is to be gathered and how system parameters like power, energy, flow, pressure, and production output are to be measured or calculated using transparent, uniform, validated, repeatable, and consistent methods of measurement.
This standard provides guidance in defining methodologies for establishing energy performance indicators (EnPIs) and energy baselines (EnBs) to be used as part of an overall energy management system (EnMS) or other related purposes. For compressed air systems, specific requirements outlining a consistent methodology for measuring, estimating, and reporting the energy performance are provided.
The intent of this Standard is to align with the requirements of ISO 50006, Energy management systems — Measuring energy performance using energy baselines (EnB) and energy performance indicators (EnPI) — General principles and guidance, adapted for compressed air system.
This Standard is not intended as a replacement for a compressed air system energy efficiency assessment (audit) as defined by other Standards, such as ISO 11011, nor does it specify measures that can be used to improve the energy efficiency of a compressed air system.
This Standard is intended to be used for compressed air systems with the following characteristics:
- electrically driven three-phase air compressors equal to or greater than 5 horsepower;
- positive displacement stationary air compressors and associated equipment;
- operating pressures between 2.5 and 17 bar(g) (36 and 250 psi(g)); and
- industrial and commercial applications of compressed air.
General explanation of how to measure and quantify Energy Performance by defining Indicators (EnPIs) and Energy Baselines (EnBs) pertaining to compressed air systems are described in the picture below.
Key to the process is creating an energy baseline as a starting point to be used to compare subsequent measurement periods in which the system may have changed. Changes to the energy performance indicators can, for example, show changes to the system as a result of energy efficiency projects. These measurements can be used by the user, perhaps a power utility energy program or a plant manager, to quantify the improvement to the energy performance of the system. This might feed into the overall performance totals of an energy program. Important to this process is the ongoing continuous consistent measurement and comparison of the system to ensure energy savings are sustained and that the system is operating normally.
Energy Performance Indicators
The standard defines two EnPIs as mandatory in development of any baseline. These are system specific power (SSP) and total energy consumption (TEC). Optional indicators are specific energy consumption (SEC) and portion of non-productive usage (PNPU). These are defined as follows:
- SSP – Average kW sent into the measurement boundary divided by average flow coming out x 100, during the measurement period. An output of this might be average kW per 100 cfm. This is an indicator of how efficiently the compressed air is being produced.
- TEC – Total kWh consumed within the measurement boundary in the specific measurement period. This can be an indicator of compressor efficiency and also how much air is being produced.
- SEC – Total kWh consumed divided by a user defined and specified production unit. Often this is could be the number of product units produced or the weight of a product. This tracks how the system energy consumption varies with product output.
- PNPU – An estimate of the percentage of non-productive compressed air flow crossing the measurement boundary compared to the average flow measured within the measurement period. In some plants this might be readily measured during regular production downtime during weekends. In others some special testing might be required. In the majority of the plants this would be an indicator of leakage and system waste.
Parameters to be Measured
The standard identifies five parameters to be measured or estimated in various specified ways as inputs to the EnPIs. These measurements would be taken on all equipment inside the measurement boundary:
- Production output
The standard is available at the CSA Group website at www.csagroup.com