Professor Krein took a sabbatical during the 2005–2006 academic year primarily to firmly establish the Grainger CEME collaborative network, currently consisting of the University of Illinois, Purdue, Berkeley, Georgia Tech, Wisconsin, Ohio State, and Oregon State. Visits were structured to conduct interactive research, initiate new research thrusts with national impact, and explore the state of the art in electromechanics based on the latest research results. The status of electrical energy research was examined at all the institutions. Summaries follow.
University members of the CEME collaborative network
University of Illinois at Urbana-Champaign
To learn more about our CEME program and what research we are working on, please see the Research Projects sections
University of California at Berkeley
Unique aspects of the program at Berkeley include the development of miniature engine-generator sets (less than 1 cm3) for power generation. The Berkeley team has also developed free-piston Sterling engines with integrated electrical generation for efficient solar energy conversion. Interactions at Berkeley introduced a new line of pursuit: so-called nuclear batteries in which energy from a radioisotope is converted directly to electricity. Prior approaches often recover energy from thermal effects of nuclear decay. More recent approaches use semiconductors to capture current flow from electronics displaced by collisions with decay particles. The collaborative effort with Berkeley will seek to gather energy much more directly as charged particles fly through an electric field.
A current industry interest is the expansion of digital control in the field of power electronics. Illinois is very well positioned in this research topic. Berkeley has applied sigmadelta modulation to power converters. In our collaboration, we found that this approach must be combined with more conventional pulse-width modulation controls to produce the best performance. A proposal was submitted in February 2006 to the National Science Foundation to support future work at Illinois in digital control of power electronics.
Another point of collaboration is spectrum management in switching power converters. Power converters usually operate at fixed switching frequency, which means electromagnetic interference appears at this frequency and its multiples. An important research question is how to define switching patterns that reduce interference without altering the operation of the converter. Past researchers have suggested randomized patterns, but these provide limited interference reduction and distort the control action. During the visit, collaboration with Berkeley team members confirmed that there are welldefined nonrandom patterns that offer better performance. Some of these results will be presented at the IEEE Workshop on Computers in Power Electronics in July 2006.
Georgia Institute of Technology
Georgia Tech is carrying out a major energy development project for remote areas in the developing world. In any communities, connection to the electricity grid is prohibitively expensive or simply unavailable. Lacking economic incentives, utility companies and communities have little motivation to establish an electricity nfrastructure. The Georgia Tech team has shown that even a few watts of electrical energy can greatly enhance quality of life. Water purification, lights, and basic communications can be supported at a small fraction of the power that the grid is designed to deliver to a home. Georgia Tech and Illinois will collaborate on devices, systems, and economic structures that could address this challenge.
Professor Ron Harley of Georgia Tech is a well-established expert in electric machines design. He and his coworkers plan to be part of the proposed MURI program for electric machine design. As an initial step in the future MURI project plans, a research project directed at intelligent algorithms for motor design will be supported by the CEME in the coming year. Professor Rincon-Mora, a new faculty member, has interests in the implementation of small-scale power converters for energy harvesting and communication processes, topics that overlap with research of Professor Patrick Chapman. This may be a fruitful area for future collaboration.
A current project is a reciprocating energy converter. An external developer has created a miniature engine that operates in an oscillatory fashion. The objective is to convert the energy of motion into electricity without adding complicated mechanical linkages. This has turned out to be fundamentally difficult.
The development of electric utility sensors is an important thrust area at Georgia Tech. They are seeking to create simple distributed sensors that can be placed throughout the grid both for monitoring and realtime control. Other major projects include the design of a circuit to extract energy from electric generators with reciprocating motion. The latter work may offer specific collaborative opportunities in the future.
The Ohio State University
Research activities in machines at Ohio State are modern and relevant to the CEME, although much of the curriculum in electric machines and power systems is relatively traditional. Prof. L. Xu has direct experience in the design of machines and has designed advanced devices for aerospace applications. An important aspect in the design procedure applies model-oriented analysis: circuit models and lumped parameters were related to the detailed geometry of the device. This procedure contrasts with FE-based approaches advocated by other researchers.
Ohio State has been preparing other leading-edge motor designs for a range of applications. For example, a motor with dual concentric rotors permits independent torque control of two half-axles—exactly what is needed for direct-drive electric vehicles. A high-efficiency motor for direct-drive washing machines is under development. Its effect on overall appliance energy consumption is substantial, and at the same time performance capabilities are markedly improved.
Other Ohio State faculty have interests that overlap with topics addressed at the CEME, including maintaining a high-voltage laboratory, boundary-element and blockelement modeling approaches that lead to modular simulation techniques, macro-scale magnetics, metamaterials, and advanced power semiconductors such as GaN. A research project directed at motor design for high efficiency will be supported by the CEME in the coming year.
Oregon State University
The primary project at Oregon State is a program to design, build, and test machines for energy extraction from ocean waves. The Oregon State ocean wave energy project serves as a fascinating case study on distributed generation, the concept of widely dispersed small energy resources that deliver electricity into the power grid. It is often considered the future of the electrical system. Although there has been active research on this topic for twenty years or more, little actual hardware has been installed. Many nonengineering issues that act as barriers to distributed generation technology are exposed in the context of the ocean-wave project. For example, Oregon State faculty have anticipated the need to reach out to non-traditional stakeholders such as the fishing industry, local governments along the coast, and many state departments including parks and recreation as well as land use and energy. More traditional stakeholders such as the utility industry, environmental groups, marine biology researchers, and others have also been involved. In the fishing industry, there are several sub-groups with concerns about wave energy: crab fishermen worry about moorings that might interfere with crab pot retrieval; others worry about disrupting fisheries or placing large zones off limits.
Thanks to diligent—and protracted—efforts by Oregon State faculty, the various stakeholders are supportive of the project. However, even though all interested parties are supportive, actual ocean testing will require careful efforts over a few years just to secure the necessary permits. The lessons of reaching out to an unusually wide range of stakeholders and involving dozens of groups in the permitting process apply to other distributed generation projects. It could well be true that alternative and renewable energy sources that adapt best to distributed generation will be difficult to implement until a consensus framework is in place. The lack of such a framework could be an important reason why few distributed generation projects have been carried out. New authority granted to the Federal Energy Regulatory Commission in the recent Energy Policy Act could complicate matters.
Based on the Oregon State experience, it is clear that excellent engineering is only a small part of the effort necessary to implement advanced energy technologies. Even in the engineering aspects, there are significant multidisciplinary challenges. For ocean wave energy extraction, massive buoys must be designed and tethered to the seabed. Electrical cables must deliver energy in a raw form from the conversion step to a central processing location, from which connection can be made to the grid. Design aspects related to habitats and biological effects are a vital part of the work. For example, certain marine creatures are attracted to electromagnetic fields and are expected to congregate around wave energy buoys unless they are heavily shielded. Electrical engineering, marine engineering, mechanical engineering, bioengineering, and materials engineering experts must work together to design the initial test system.
The electromechanical design of a waveenergy device offers unusual challenges. The motion is reciprocating, like the challenge at Georgia Tech mentioned above, and extraction is a complicated process. The masses involved are large, typically several tons, so any energy extraction scheme that is oscillatory might add vibration and fatigue issues. A research project to refine a machine design for wave-energy extraction will be supported by the CEME during the coming year.
Purdue researchers have been applying genetic algorithm methods to design and multi-variable optimization of electromechanical devices and systems. Their significant contributions include design-oriented machine modeling methods and effective methods for multidimensional optimization. They have shown why conventional finite-element (FE) tools are not well suited to electromechanics design, and helped create reduceddimension models that provide a better design base. Although the results are promising, they have not been picked up elsewhere in the academic community or in industry. One outcome of the collaboration was to begin work on a major center-level multi-university proposal that will seek several million dollars for future electromechanics design tools. Another was Purdue’s recognition of the value of the CEME, with a commitment to participate actively in our seminar series, educational programs, and broad research thrusts. Discussions about FE tools and machine models at Purdue have influenced research at Illinois. Graduate student Marco Amrhein at Illinois, whose work addresses design methods for motors, has identified the fundamental bases for FE weaknesses.
Discussions at Purdue about textbooks and education issues were especially fruitful. The fresh perspective elucidated the contrast between analysis-based approaches and design-based approaches. Purdue has been placing strong emphasis on future engineering education. They are also in the process of establishing a research center for energy studies with about 130 faculty campus-wide involving research groups from biology, public policy, solar energy, nuclear sciences, and a wide range of other topics. Purdue has agreed to participate actively in the proposed MURI program for electric machine design.
University of Wisconsin-Madison
Wisconsin has developed the nation’s strongest reputation in the areas of electric machines and their control. An important basis of this reputation is their emphasis on industry interaction. Many current projects address specific sensing and control problems in industrial applications. Activities have been directed toward the national Center for Power Electronics Systems (CPES), an NSF Engineering Research Center directed by Virginia Tech with Wisconsin as a major partner. CPES also has a reputation for a strongly industry-oriented research program.
A major research emphasis is “self-sensing” in electromechanical devices. This is the principle that physical effects within a device generate detectable signals that can be used to infer information about position, electrical variables, or magnetic variables. Any real device has some degree of self-sensing capability by virtue of its construction. Effects can be enhanced with intentional design changes. Projects based on self-sensing have been carried out at Wisconsin for more than ten years. Some of these methods are widely used today in the industry.
This visit enhanced the participation of Wisconsin in the CEME. They are expected to become more regular participants in the CEME research seminar series. Two younger faculty members in their group are likely to benefit from research collaboration with Illinois.