Closed-Loop Process Cooling Independent Case Study: Energy, Operations and Other Resources
by Gerald Church, UC Davis Energy Efficiency Center and Glen La Palme, PL Energy LLC
Bonus Content Summer 2010
This case deals with intelligent process cooling utilizing closed-loop systems, point-of-use chillers and ambient air managed with efficient motors and fans. Eliminating the traditional cooling tower with a closed-circuit fluid cooler, the Frigel Ecodry System is designed to provide clean water at the right temperature to process machines year round.
The case is a plastics manufacturer operating 22 injection molding machines. Support equipment: 150 ton cooling tower for hydraulics with central chiller utilized for HVAC and integrated to manufacturing floor to provide 60 tons of mold cooling. The chiller is required to operate at 44°F and pump throughout the plant.
The energy saving from Ecodry originated from a decentralized system saving on energy from pumping, operating at proper chilled water temperatures (50 to 80°F), and supporting processes cooling temperature control versus managing suboptimal temperatures from a central location with distributed thermal losses. The ability to automatically provide ambient cooling utilizing the Ecodry in lieu of chiller for cooling molds when dry bulb is below 71°F was an additional savings factor. Table 2 shows the potential energy savings from this measure.
But what about the improvements obtained from cycle time improvements utilizing smaller point-of-use chiller/temperature control systems providing higher flow and pressure at the mold with 20 percent reduction in mold cooling times, reduced mold changeovers with mold drain kits and improved product quality?
To measure the financial benefits from operations we used the Transformation Planner financial benchmarking tool. Restating, the process is two steps.
1. Input the current manufacturing performance.
2. Model the expected or desired changes in percentages or dollars.
The model recalculates benefits in annual cash flow and balance sheet. Calculating the improved state, we held the improvements in operational performance to 5 percent although productivity improvements from cycle times based on customer interviews achieved 20 percent and reduction in scrap and rework by better control over mold temperatures would be reduced by 10 percent or more over the current state .
The performance chart (Chart 2) shows the input/outputs from modeling with manufacturing changes held to 5 percent in relative improvement or absolute dollars with the target improvements ranging from 2-15 percentiles from this project.
The following charts show the computed savings in dollars accruing from a broader range of savings not customarily computed based on annual revenue of $243,000,000.This project moved from good to exceptional as these additional savings were calculated.
Finally, annual water savings were 1,847,814 gallons (existing tower 1,981,076 minus upgrade at 137,262). Water Treatment pre-Ecodry equals $15,000 annually and is reduced to $1,200 annually following installation. Total project savings from water is $15,001 but raises a question about this resource: what are the embedded electric costs with moving and treating all this water?
In conclusion, it is important to understand your process cooling system design and the costs associated with operating it versus your plastic processing requirements. Evaluate your process temperature and chiller loads. Understand the cost of integrating chilled process water for plant manufacturing with HVAC/comfort air. This can be a huge loss in energy and productivity.
PL Energy LLC is a California-based firm providing a number of engineering and technical services and dedicated to tailoring them to each client, including: comprehensive energy audits, energy consulting, energy management services, technical training and more. Learn more at www.pl-energy.com.
1) Extracted from Church, G. 2009: ACEEE Summer Study of Energy Efficiency in Industry, Energy Financial Project Analysis, What Have We Been Missing? 2009 Summer Study Program in Industry, American Council for an Energy Efficient Economy, Washington, DC, aceee.org.
2) A discussion about the relationship between calculating changes in manufacturing performance and energy savings can be found at; La Palme, Glen, et al: 2007, Generating and Calculating Energy Intensity Savings from Manufacturing Productivity Improvements, 2007 ACEEE Summer Study of Energy Efficiency in Industry, American Council for an 3) Energy Efficient Economy, Washington, DC, aceee.org.
United States Environmental Protection Agency, Lean and Energy Toolkit, Revised October 2007, EPA-100-K-07-003, www.epa.gov/lean.