Intelligent Process Cooling Technology Saves on Water and Energy, Improves Productivity

Transcription

1 Intelligent Process Cooling Technology Saves on Water and Energy, Improves Productivity Presented at the Society of Plastics Engineer s ANTEC, May 1-5, 2011 in Boston, MA, USA Lou Zavala, National Sales Manager Frigel North America 150 Prairie Lake Road Unit A East Dundee IL

2 Abstract The concern for the environment in the plastics industry needs to go far beyond materials where it is typically found. Curbing energy use, water use and chemical disposal are significant responsibilities of the industry as well and can, to a large degree, be accomplished through a more streamlined approach to process cooling. When implementing closed-loop dry cooling, processors see immediate reductions in energy, water and chemical use, directly impacting the local environment as well as the bottom line. Introduction In the United States and in most industrialized nations, manufacturing is the culprit of a great deal of resource consumption. So it is our responsibility to continue to drive innovation and continuous improvement. Some improvements will be incremental such as motion sensor lighting systems and water saving fixtures for employee use, and other areas represent an opportunity for much more. Currently, approximately 92 percent of a manufacturer s energy consumption is attributed to processing machinery and 16 percent of that is used to operate process cooling systems [1]. Adding to significant energy use, in developed countries industry uses 45 percent of the available water [2], and one of the top five sources of that waste is in inefficient and poorly maintained methods for cooling [3]. At the heart of all of these environmental downfalls by industry is technology that plastics processors have long relied on such as cooling towers and central chillers. These inefficient methods are responsible for using an estimated 5.3 quadrillion liters (1.4 quadrillion gallons) of water/year. They also require fans and pumps to be continuously running to keep up with the water and cooling needs of these systems and the open looped nature of a tower system creates dirty water leading to scale accumulation that drives down efficiencies. Table 1: Effect of scale on heat transfer Page 2 of 10

3 Figure 1: Effect of scale on energy consumption of chillers Statement of Theory Traditionally processors incorporate open tower systems with centralized chillers, pumps, multiple insulating piping configurations and move cooled water over long distances to provide the needed temperatures machine side. The evaporation alone accounts for significant water consumption. For example, to achieve one ton of cooling, a tower must evaporate around 0.11 liters (0.03 gallons) of process water every minute. Extrapolating that into a common scenario, based on 8,760 operating hours per year (24 hours/day, 365 days/year) with tower operating at full capacity, a 100 ton tower consumes 5,968,838 liters (1,576,800 gallons) per year. The Ecodry System, or the closed-loop dry cooling system, offers processors advanced technology with a simplified set up that utilizes a single unit feeding machine side TCUs and a single set of non-insulated pipes running through the facility. The closed-loop nature keeps water clean and eliminates evaporation which means no continuous water or chemical consumption and the elimination of chemical emissions into the atmosphere and wastewater dumping into a community s water supply. Using the same scenario above, water savings would equal over 97 percent. Page 3 of 10

4 Description of Technology The closed-loop, dry cooling technology operates by pumping water returning from the process into heat exchangers and cooling it with ambient air flow. This process provides clean water at the right temperature to process machines year round. Desired water temperatures are continuously met through control and software that provides fully-automatic water and energy savings adjustments based on actual thermal load and outdoor temperatures. To maintain water below setpoint in hot weather, defined as 29.4 C (85 F), outside air passes through an adiabatic chamber before reaching the air-to-water heat exchanger coils. Adiabatic mode keeps LWT below 35 C (95 F) even when ambient temperatures reach 48.9 F (120 F). In the chamber, a fine mist of water (from a separate source) is pulsed into the air stream, evaporates immediately and cools the air before it impinges on the cooling coils. The spray function and volume of water used is controlled by the microprocessor based on ambient temperatures. Only cool, dry air makes contact with the heat exchanger coils, creating the concept of dry cooling. This ensures coils are kept completely dry and free of scale. Figure 2: Adiabatic cooling diagram During colder months, this closed-loop dry cooling technology automatically adjusts so the recirculation pumps turn off and the unit drains fully, providing 100 percent freeze protection. Non-draining units can be used in non-freezing climates or if desired, glycol can be used in freezing climates. In these situations, the technology also provides opportunities for free cooling, where machine side units are supplied with clean cooling water, replacing the need for chillers and turning off any chiller compressors, fans and other energy consuming functions. Depending on process set points and local ambient conditions, free cooling can benefit many processors. Page 4 of 10

5 Figure 3: Chart shows what percentage of the year you can start to take advantage of free cooling based on Chicago, IL weather data for purpose of example [4]. The limited times of the year when it is necessary, additional air flow is generated by axial fans with variable DC motors, creating the lowest energy consumption available. The fans provide extremely high efficiency under partial load conditions and have an average annual consumption of less than 0.03 kw/ton. kw / fan O U T D O O R T E M P. ( F) Figure 4: Chart shows energy consumption of 0.03 kw/ton based on LWT of 32.2 C (90 F) in Los Angeles, CA. While the above description focused primarily on the substitution of a cooling tower with a closed-loop, dry cooling unit, the other part of the system involves the machine side units. Large pumping stations and central chiller systems create difficulty for a processor to achieve precise water temperature at all process machines and achieving that means significant energy consumption. Modern machine side technology can include both chiller and temperature control unit functionality in one compact unit and adjust for required temperature, flow and pressure individually. With cooling parameters optimized at each machine, results are better part quality, cycle time improvements of up to 20 percent and less scrap that would end up in landfills or require energy to regrind. As an alternative to central chillers, this method can save up to 80 percent of energy consumption from reduction of thermal losses and minimal pump horsepower required. Page 5 of 10

6 Figure 5: The top illustration represents the flow of water through an injection mold using a central chiller and flow meter combination, the result is a T of 11.1 C (20 F). The bottom illustration represents a dedicated machine side unit showing a low T of 1.1 C (2 F). The result of less T is better quality parts, faster cooling and less scrap. Results As a result of the negative impact cooling towers and central chillers have long had on the environment and company s bottom lines, closed-loop dry cooling provides a new way to benefit from performance improvements as well as meet sustainability goals. Those environmental benefits include: Highest global energy efficiency and lowest energy operating cost Lowest water consumption Zero ongoing chemical use and disposal, eliminating costly filtration and contamination of water supply Lowest risk of refrigerant gas emission to atmosphere Reduce production of plastic scrap Highest productivity (generating additional savings of energy, water, resin and effort) Specifically, the following benefits can be seen by an operation: Energy savings: A typical 100-ton cooling system operates with about 0.8 to 1.2 kwh/ton energy consumption. A comparable-sized closed-loop dry cooling system uses 0.05 kwh/ton. Water savings: In addition to pollution prevention and ending contamination of community water sources, the water volume savings are significant. In a typical 100-ton cooling system, this technology reduces consumption by over 3.78 million liters (1 million gallons) of water/year. Maintenance time savings: This technology operates with minimal maintenance. It can save companies up to 40 hours in maintenance per month. Page 6 of 10

7 In many cases, adding up the energy, maintenance and water savings results in payback of less than two years, and depending on the climate and system demands, can be as soon as one year. Additionally, rebates from state and local government, as well as utilities, are available for manufacturers implementing energy saving technology and tax incentives such as the American Recovery and Reinvestment Act of 2009 [5] are also available to those implementing closed-loop dry cooling technology. Independent Study In an independent study lead by researchers at the UC Davis Energy Efficiency Center and PL Energy LLC, a California-based energy consultancy, a processor operating 22 injection molding machines was analyzed [6]. The existing system consisted of a 150 ton cooling tower with a central chiller operating at 6.7 C (44 F) and providing 60 tons of mold cooling. This set up was replaced by a closed-loop dry cooling unit and press side units. The ability to automatically provide ambient cooling in lieu of a chiller for mold cooling created savings as well as the reduction in pumping and the method of cooling. Potential energy savings from this measure are shown in Table 2. Table 2: Annual total energy savings projected during study [6]. Page 7 of 10

8 Additional analysis found that in addition to environmental and financial benefits, manufacturing performance including on-time deliveries, inventory turns, machine hours available and other measures were improving with closed-loop dry cooling as well. See noted improvements in Figure 6. Figure 6: This performance chart 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 [6]. Finally, the savings in dollars were computed on these benefiting production items that are not customarily included in an analysis of a process cooling system but proved to be positively affected in the end. Table 3: Energy and operations savings broken out annually and monthly based on closed-loop dry cooling system implementation [6]. Page 8 of 10

9 Figure 7: The annual results above are represented here as a pie chart to see which savings had the most financial impact on the molder [6]. Conclusion Energy and water every day become more scarce and more of a concern to the commercial, government and residential sectors alike. Because of industry s significant demand on these available resources, it goes beyond the bottom line and becomes a responsibility of manufacturers to take action to lessen its reliance. As demonstrated here, great opportunity lies in process cooling technology available today that can support these initiatives. With measurable savings available, it is important to first understand the current process cooling system and its impact on the environment as well as the company s financial performance. With that information in hand, it will be easy to see the post-installation results that many companies have experienced to date including: Improved productivity Substantial savings on volume of water and energy use Eliminated dumping fees associated with chemical treatment Nearly zero gas emissions due to consistently clean water Met sustainability goals Realized less maintenance and associated costs Page 9 of 10

10 References 1. Dr. Robin Kent, Energy Management in Plastics Processing Strategies, targets, techniques and tools (2008). 2. Global water crisis overview. April How to save water in the workplace. June National Environmental Satellite, Data, and Information Service (NESDIS) U.S. Department of Energy, Business Tax Incentives Church, G. 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. Page 10 of 10