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Energy Manufacturing Research Highlights

 

By Ellen Kehoe
Senior Editor
Journals and Tech Papers

A few years ago, lights-out manufacturing might have meant literally turning off the switch and closing the factory doors. Today, the renewed focus on manufacturing is advanced and energized, not in the least by efforts to explore energy consumption and management at the process, material or equipment level.
 
Last June’s co-located SME North American Manufacturing Research Conference (NAMRC), ASME Manufacturing Science and Engineering Conference (MSEC) and JSME International Conference on Materials and Processing (ICMP) included papers investigating energy efficiency through process improvements, materials choices, recycling regimes and sustainability analysis. Additional material from SME’s collected research and conference papers shows how important managing energy is to manufacturing—and how important manufacturing is to managing energy.

 BMW’s Energy Center at the company’s Spartanburg, SC, manufacturing plant uses real-time energy conversion strategies to minimize cost and environmental effects. There are also a number of sustainability measures, such as co-generation of electricity and heat from landfill gas, and a photovoltaic solar array to produce electricity for the plant’s visitor center.

Semiconductor Spotlight

One of the institutes of the ever-expanding US National Network for Manufacturing Innovation (NNMI; www.manufacturing.gov)—PowerAmerica, the Next Generation Power Electronics Manufacturing Innovation Institute (led by North Carolina State University, Raleigh, NC; research.ncsu.edu/power)—is charged to “accelerate the commercialization of wide bandgap technologies” to help reduce energy consumption and increase US manufacturing competitiveness.

Silicon-based power electronics components are the most common type used today, integral to consumer electronic devices, such as phones, computers and televisions. They are also used in large-scale applications in industrial motor systems and electricity transmission. PowerAmerica aims to make wide bandgap (WBG) semiconductor technologies cost-competitive with silicon-based electronics by developing critical WBG technologies, spurring demand in high-value markets, supporting and growing a manufacturing base and building the US WBG semiconductor industry through education and training.

Energy consumption and heat dissipation through racks have increased as miniaturized semiconductors are arrayed in high-density processors at IT data centers that monitor and evaluate manufacturing processes and equipment. Such data centers, both within and outside of existing buildings, themselves require thermal management, often through refrigeration cooling systems at a significant energy load.

Researchers from Oregon State University’s Energy Efficiency Center (Corvallis, OR), in a paper from NAMRC 2014 (in press for SME’s Journal of Manufacturing Systems; http://tinyurl.com/JMS-datacenters), evaluated metrics developed to overcome the energy efficiency and thermal management challenges at data centers. Measuring the performance of IT centers using a combination of metrics can increase the opportunity for considerable energy reduction. Microelectromechanical system (MEMS) technology has helped create wireless sensor networks (WSNs) for real-time environmental (indoor/outdoor), power, process automation and structural monitoring.

 Hydrogen extracted from methane drawn from landfills fuels material-handling equipment at the BMW Manufacturing Co. plant in Spartanburg, SC. Shown here is the hydrogen storage and distribution area near the plant’s Energy Center.

The metrics explored include one of the most practiced ones, power usage effectiveness (PUE), as well as data center infrastructure energy (DCiE), rack cooling index (RCI), return temperature index (RTI) and supply and return heat indices (SHI, RHI). Future work is suggested on developing a single metric—for a more straightforward approach—and optimizing operational adjustments based on real-time measurements to more effectively evaluate energy efficiency and the impact of changes in data centers.

At NAMRC 2015 in paper #118, Oregon State authors again discuss manufacturing energy analysis of microchannel heat exchangers for high-density servers. Use of microchannel process technology (MPT) devices to provide liquid cooling is hampered by high manufacturing cost and energy requirements. Manufacturing process energy analysis of a microchannel heat exchanger is conducted and compared for photochemical machining and two joining methods, diffusion bonding and laser welding. The latter results in significantly lower life cycle energy impact due to reduced process energy and improved yield.

 

Geographic Considerations for Solar, Wind

A 1976 SME Technical Paper by a Honeywell manager of solar energy technology described the basic problems standing in the way of rapid commercialization of solar (http://tinyurl.com/tp76pub78), both of which somewhat still apply today. First was the geographic mismatch among the southwest US’s high insolation (solar radiation received), the high heating requirements of the north and the high population density of the East Coast. Second was the high initial cost of installed systems and the relatively slow economic payback through the displacement of conventional fuel.

In the automotive industry, energy use is intensive, making greenhouse gas (GHG) emission reduction a significant topic. A study reported in a NAMRC 2011 paper (http://tinyurl.com/tp11pub34) assessed the GHG emission reduction potential of solar PV (photovoltaic), wind and fuel cells at six global General Motors sites, which were selected based on differences in energy supply structure and geographic conditions.

Wind power was found superior to the other two clean energy systems in economic performance of the GHG mitigation effect, particularly in those regions with high wind energy density (around Bochum, Germany) and/or high GHG emission factor (near Shanghai, China). Among the six countries (US, Mexico, Brazil, Germany, Egypt, China) represented in the study, the highest mitigation potential of GHG emissions was estimated in China through wind power supply. Solar and fuel cell system applications showed much less potential for GHG mitigation in the six countries.

Although focused just on GHG mitigations, the analysis could be extended to other environmental emissions. Beyond the paper’s scope is consideration of alternatives available in some geographic locations for carbon credit trading and offsetting.

At MSEC 2014, the same authors, from the University of Wisconsin-Milwaukee and General Motors R&D, presented more on geographic differences of GHG emission reduction from electric vehicle deployment in the US. Considering the total GHG emissions generated from the life cycle of an electric vehicle (EV; represented by a Nissan Leaf) and an internal combustion vehicle (ICV; represented by a Toyota Corolla), the results indicate a 43% GHG emissions reduction from ICV levels with the deployment of EV, based on the average US electricity generation mix and driving styles across the 50 states (MSEC 2014 paper #4141).

 

Solar Technology

Solar cell technology is a promising source of clean energy but is hampered by low efficiency, high manufacturing cost and large consumption of material. In a NAMRC 2014 paper (in press for SME’s Journal of Manufacturing Processes; http://tinyurl.com/JMP-solarsubstrate), Himanshu Ingale and Murali M. Sundaram (University of Cincinnati, OH) describe a novel method of depositing a thin film direct bandgap semiconductor material on a lightweight substrate. The efficiency of such solar cells can be further increased by providing a textured surface (wrinkling), resulting in reduced optical losses, thus increasing light trapping. More than a 10% increase in transmittance and short circuit current resulted if a cadmium telluride (CdTe) solar cell is deposited on the textured substrate.
At At University of Wisconsin-Milwaukee’s (UWM) Lab for Sustainable and Nano-Manufacturing (LSNM), Professor Chris Yingchun Yuan shows a high-performance lithium ion battery pouch in development for electric vehicles.of Wisconsin-Milwaukee’s (UWM) Lab for Sustainable and Nano-Manufacturing (LSNM), Professor Chris Yingchun Yuan shows a high-performance lithium ion battery pouch in development for elec
A paper presented at this month’s NAMRC 2015 (hosted by the University of North Carolina at Charlotte, June 8-12; http://tinyurl.com/NAMRC2015), by Shilpi Mukherjee, Gregory Salamo and Ajay P. Malshe of the University of Arkansas (Fayetteville), examines the paradox of solar cell manufacturing plants and research laboratories in the US that use nonrenewable energy for their operations—“the energy cost of energy research.” A case study sought to quantify by life cycle assessment the energy demand of research on quantum-wire (QWR) based intermediate-band solar cells grown by molecular beam epitaxy (MBE) and fabricated by photolithography (NAMRC 2015-#131).

Automating the assembly of photovoltaic solar modules “presented a daunting task” due to widely different materials presented at each step, as described in SME Tech Paper TP05PUB85 (http://tinyurl.com/tp05pub85). A robotic assembly cell featured a vacuum (end-of-arm tool) manipulator that successfully picked up each of the materials without a tool exchange.

Looking back to 1977, when solar arrays for electrical power for space vehicles had been around for some time, SME Tech Paper TP77PUB19 (http://tinyurl.com/tp77pub19) (by an author from Lockheed Missiles & Space Co.) looked at ultrasonic bonding as a lightweight, reliable alternative to traditional soldering and welding for interconnecting photovoltaic solar cells.

 

Batteries

A roll-to-roll, multistation flexographic printing process for large-scale energy storage fabrication, scaled from previous solid-state, zinc-based battery technology, was proposed by University of California-Berkeley researchers in a NAMRC 2012 paper (http://tinyurl.com/tp12pub66). New functional materials suited to flexographic printing were developed and analyzed for use in manufacturing energy storage devices.

Electrical performance of laser braze-welded aluminum-copper interconnects for assembly of lithium-ion battery cells is the subject of collaboration by University of Luxembourg and General Motors Global R&D researchers, published recently in the Journal of Manufacturing Processes; http://tinyurl.com/tp12pub66). The main focus of the work is on the effect of intermetallic compounds on the contact electrical resistance of the Al-Cu joint, the correlation between mechanical and electrical properties of the joint and the impact of the weld seam layout on the contact electrical resistance.

Two papers from 2003’s International Conference on Composite Materials (ICCM-14; San Diego) describe the use of fibers in battery composition. The first paper (http://tinyurl.com/tp04pub113) covers development of solid-state, thin-film rechargeable batteries on fiber substrates for energy and power storage in novel, stand-alone thin-film battery applications, power composites and electrotextiles. In the second paper (http://tinyurl.com/tp04pub68), dual-function carbon fabric composite anodes are analyzed for strength and electrochemical activity.

 

Plant-Level Energy Analysis

Lean energy analysis (http://tinyurl.com/tp04pub337) is a methodology presented at a 2004 SME conference on advanced energy and fuel cell technologies. Energy usage in manufacturing facilities encompasses direct production of goods, space conditioning and general facility support, such as lighting. With as few as 60 easily obtainable data points, the lean analysis method graphically and statistically develops multivariable change-point models of electricity and natural gas use as functions of outdoor air temperature and production data.
The Molecular Foundry at the Lawrence Berkeley National Lab (Berkeley, CA) is exploring dynamic nanointerfaces for novel functionality in environments that are out of equilibrium, such as in solar cells.
A paper from MSEC 2014 (paper #4014) by Clemson University (Greenville, SC) and BMW Manufacturing Co. (Greer, SC) authors focuses on a multiobjective optimization strategy for a plant-level energy supply system. With an example from an automotive assembly manufacturer, a complex multiple-input, multiple-output (MIMO) system was used for single-objective optimizations and linearly scaled multiobjective optimization to analyze energy, economy and environment in the representative plant. Three aspects were identified for future work: better forecasting of energy demand and operations strategies; development of shorter time resolution, such as minute and second modeling of equipment operational dynamics; and consideration by economic analysis of the equipment, construction and labor cost of energy management.

 

Energy-Conscious Scheduling

Reducing energy cost in a factory may seem as simple as running machines at off-hours or turning down the heat and lights, but energy-conscious scheduling of a manufacturing facility is more complex and less flexible than is energy consumption management in residential and commercial buildings.

Purdue University’s Hao Zhang, Fu Zhao and John Sutherland proposed the feasibility of reducing electricity cost for a manufacturing factory through scheduling in a smart grid scenario while maintaining production throughput. A hypothetical region including a power distribution/transmission system, residential/commercial buildings and a flow shop operating 8/16 working hours/day was considered (MSEC 2014-#3926).

In an accepted NAMRC 2015 paper (#64), the same Purdue researchers expand on the theme by applying it to multiple collaborative factories to reduce energy cost. The multiple-factory scheduling problem is decomposed into suboptimization formulations by assigning each factory a virtual electricity price that is determined by the hourly power consumption threshold, the factory’s energy consumption and the predicted demand from all factories. Additional rules might need to be applied to proportionally reallocate electricity costs to participating factories and to safeguard sensitive production information.

 

Energy Consumption in Processes

Over the last few years, the energy expended during specific manufacturing processes has sparked increasing research interest. The effects of spindle speed, feedrate and lubricants on the energy used in single-point incremental forming (SPIF)—a dieless sheet-metal forming technique for complex asymmetrical shapes without the need for specialized tooling—are described in TP12PUB62 presented at NAMRC 2012 (http://tinyurl.com/tp12pub62). While the direct energy used increases with the feedrate, the idle energy used by the machine remains the same. Lubricants of different viscosities cause almost no change in energy use, and little appreciable difference in surface roughness was noted.

Two recent papers published in the Journal of Manufacturing Processes deal with energy input during friction stir welding (FSW). FSW is a process qualitatively known to use less energy than fusion welding, but no tools or data have existed to quantify the energy consumption. Amber Shrivastava and Michael Overcash (both of Wichita State University, KS) and Frank Pfefferkorn (University of Wisconsin-Madison) use the unit process life cycle inventory (UPLCI) concept to focus on the energy consumed in the FSW module, that is, the actual creation of the weld joint. The authors point out that strategies to reduce total energy use in FSW “may differ significantly from those used for metal cutting” because, although the same milling machines may be used, there are differences in idle power demand vs. required processing time and power. In FSW, the “first place to look for energy savings is in the welding parameters” (http://tinyurl.com/JMP-frictionstir).

Friction stir spot welding (FSSW) is a process attractive to manufacturers for joining metals like aluminum in components for lighter weight, fuel-saving vehicles. Vanderbilt
University (Nashville, TN) researchers explore how the number of tool rotations, rotation rate and dwell time affect the quality of a spot weld, and they quantify the energy generated during the welding operation. Spot welds created at lower energies, above some threshold energy level, are found to be significantly stronger than those created at higher energies. A control system for FSSW process energy monitoring is a future aim of this research, to increase the potential of the process in manufacturing (http://tinyurl.com/JMP-FSSW).

Energy-efficient 2.5D CNC milling toolpaths that have characteristics designed for reducing energy usage are proposed in NAMRC 2015 paper #106. The authors propose that “it is possible to reduce energy consumption in a manufacturing process without compromising on its productivity or performance by identifying and optimizing the underlying energy consuming phenomena.” In addition to material removal rate (MRR)—by which most analytical models of CNC milling estimate energy usage, the geometric characteristics of toolpaths must be considered. Further research is contemplated on energy-efficient toolpaths by design, machine-specific toolpaths and trade-offs with other performance indicators.

Manufacturing consumes energy and also produces greenhouse CO2 emissions. With previous research focused at the machine tool and spindles levels (where energy can be described by traditional empirical models), the authors of NAMRC 2015 paper #91 define a new concept—net cutting specific energy—to investigate the energy consumed at the process level in actual material removal in finish hard milling of tool steels.

 

 

Research Flashback

In 1977, discussing US Environmental Protection Agency (EPA) rules for hydrocarbon emissions, an industrial environment manager from General Motors aptly connected the stricter regulations to savings in energy, water and waste (http://tinyurl.com/tp77pub112). “Much emphasis is being given to low-solvent coating technology. It is our belief that this is the most acceptable long-range strategy for auto body painting, and for many components as well. We are hopeful that this work will be beneficial in lowering energy requirements, avoiding dependence on natural gas, and reducing water treatment and solid waste disposal loads.”

And in a paper (http://tinyurl.com/tp81pub61) at SME’s Finishing ’81 conference, the director of engineering for the Edison Electric Institute (Washington, DC; www.eei.org) gave this relevant summary: “Economic, technological, environmental, political and social factors are all in the mix, which must be dealt with realistically in a relatively short period of time to assure America’s energy future. We cannot risk, for example, a situation in which electricity shortages might be chronic. If this were to occur, a number of unhappy consequences could result, including the use of less advanced industrial processes and procedures. This, in turn, could downgrade productive efficiency, move the U.S. toward
economic decline, weaken its ability to compete on the international scene….”

 
For information on obtaining NAMRC and MSEC papers, contact publications@sme.org. SME Technical Papers (coded as TP…PUB…) and search options for the 16,000-document collection are available at http://tinyurl.com/SearchTPs

 

This article was first published in the 2015 edition of the Energy Manufacturing Yearbook.   


Published Date : 3/7/2016

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