Can you prove your compressed air savings?

Very often I hear of companies embarking on compressed air energy-efficiency projects after attending the Compressed Air Challenge seminars. Attendees learn that there are many low-cost/no-cost efficiency measures that can be implemented for some good savings without much effort. But when you undertake these projects, how do you know for certain how much energy you're saving, and how can you know over time that the reduction has been sustained?

Rarely do compressed air systems have any energy metering or flow metering installed. It is often up to some outside party to come in and measure your system to determine the energy consumption. Typically the energy auditor comes in and measures only once, before the projects are implemented. Many times, efficiency measures are implemented and the customer will just assume the promised savings have been achieved.

In my experience, many things can go wrong that lead to unexpected project results, and one should not assume that every project will be a success. For this reason, it's important to measure key compressed air parameters both before a project begins and after it is completed. This is called baselining the system. If compressor power, flow, and pressure are all tracked, it's easy to determine if the expected savings have materialized.

Outside contractors can be called in each time to measure your system, but the best practice is to constantly monitor and track your system. To do this, some sort of permanent system of measurement and tracking is required.

Fortunately, in this day and age, the instruments to do this are readily available and affordable. Modern instrumentation can be installed on any compressed air system to track system compressed air production efficiency (kW per 100 cfm), total kWh, average and peak flows, and average and peak pressure. These monitors can even stay the weekend to measure leak loads during nonproduction times.

Tracking and logging key system parameters can clearly show you where your savings are and help you maintain these savings for years to come.

An example of this is comes from a large fabric plant I visited recently. The managers were admittedly concerned about their compressed air because it accounted for 65% of the total facility energy use. Each of the plant's large air compressors was fitted with energy meters and flow meters. The operations staff members now know the exact energy consumption of their system. When air compressor performance falls below expected levels, rebuilds are done. Old compressors' performance also is compared with that of new replacement compressors, and a financial analysis done. Because the energy consumption is known, it's easy to calculate when the compressor should be completely replaced with a new, more-efficient unit.

Knowing the compressors' characteristics, the operators can select the most-efficient compressors for the requirements, keeping operating costs down. They can also assess the impact of other energy-efficiency measures, such as leak reduction programs and load management. Recently, some of the facility's production looms were replaced with more-efficient models. The management could see very quickly how energy consumption per unit of fabric dropped once the project was implemented. This makes it easier to sell future projects to management.

Learn more about baselining at Compressed Air Challenge's next Fundamentals of Compressed Air Systems seminar. Check out the calendar at www.compressedairchallenge.org.

 

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  • Several years ago I was the compressed air consultant to Carbon Trust. Without doubt there have been instances where an air-user has been sold equipment with promises of energy savings that simply never materialised. One report of mine showed an increase in energy consumption, solely due to the user installing equipment that a local air-house claimed would reduce energy consumption. The technology might be out there, but a local salesman might not understand where it should be applied and when it should not.

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