Industrial Utility Efficiency
Given that compressed air leak management programs are meant to save energy, reduce CO2 emissions, and generate ROI, DENSO’s Maryville, Tennessee, manufacturing facility can definitively say it has scored a trifecta when it comes to results – and reaped benefits beyond hard numbers alone.
A small Australian company, Basil V.R. Greatrex (BVRG), is shaking up the compressed air industry in Australia. While other companies focus on the sale of more and bigger compressed air production equipment, BVRG is helping customers reduce their compressed air system size and lower system flow by attacking waste, inappropriate use, and at the same time improving air quality.
A major poultry processor and packager spends an estimated \$96,374 annually on energy to operate the compressed air system at its plant located in a southern U.S. state. The current average electric rate, at this plant, is 8 cents per kWh.
“Retro-Commissioning” (ReCX) of compressed air systems has become a trendy activity with many utility demand-side-management programs emerging in the last 5-10 years. This is intended to be the process of “tuning up” a compressed air system, getting low cost savings from mostly adjustments and repairs. The term was borrowed from the building/HVAC industry, where it means to get a system operating as it was originally “commissioned”.
UniFirst is one of North America’s largest workwear and textile service companies. They outfit nearly two million workers in clean uniforms and protective clothing each workday. Founded in an eight-stall garage in 1936, the Company has grown to 240 customer servicing locations throughout the U.S. and Canada servicing 300,000 business customer locations. The subject of this article is an energy-saving Air Demand Analysis (ADA), conducted by Kaeser Compressors, at UniFirst’s centralized 320,000 square foot hub Distribution Center located in Owensboro, Kentucky.
MHPSC Canada is a large facility specializing in machining and manufacturing large pieces for power generation (gas turbines, large hydro, wind) and deep sea oil and gas operations. Smaller machining and manufacturing are also done in the facility, as well as welding and piping fabrication. MHPSC purchased flow meters for two systems, the Large and Small Machine Shops, to measure the total compressed air production. Since the two systems have piping that is physically close together, it was felt that there was an opportunity to tie the two systems together to save energy. The readings showed that the compressed air demand was indeed low enough in the two systems to enable a 100 hp VFD compressor to feed the combined systems.
There is an often-quoted ratio of 7.5 hp input to one horsepower output used to illustrate the inefficiency of the energy transfer in compressed air systems. What this is saying is that you receive the benefit of only 13 percent of the energy you put into your air compressors as mechanical output at the shaft of a typical compressed air powered tool. While this ratio is generally true for compressed air system awareness discussion purposes, you should understand that in the real world compressed air efficiency is usually much lower.
When Compressed Air Consultants was starting, in 2003, we were approached by a company experiencing significant problems with their compressed air system. They had compressed air pressure problems causing production interruptions. They had moisture issues causing all kinds of havoc throughout the facility and appeared to be using far too many air compressors for what they wanted to accomplish.
The intent of this article is to provide readers with simple examples of calculations one can perform to evaluate two sample energy efficiency projects for compressed air systems; pressure sensing vortex vacuum generators and outside air intake (for air compressors).
Compressed air optimization measures adopted by PTMSB have reduced the consumption of compressed air by 31 percent resulting in savings of about 3,761,000 kWh per year in energy consumption. The monetary savings are MYR 1,090,627 per year (\$255,000 USD). The CO2 reduction is estimated at 2,735 ton per year.
Technology is available which enables a compressed air flow meter to measure not only the magnitude of the flow, but also the direction. Why is this important? In this article we will describe two case studies where bi-directional compressed air flow measurement plays a key role to come to the right conclusions. In the first case study, we will describe an electronics manufacturing plant, which has a large interconnected ring network with two air compressor rooms located in different buildings. The two air compressor rooms are about five hundred feet apart. In the second case study, the effect of compressed air flow measurement upstream of a local receiver tank is described.
