Rabin, Rubloff, Takeuchi, and Wachsman Present at Sustainability Workshop

Department of Materials Science and Engineering professors Oded Rabin, Gary Rubloff, Ichiro Takeuchi, and Eric Wachsman presented their work on fuel cells, energy storage, reclaimed waste heat, and thermoelastic cooling at the 2011 Clark School Engineering Sustainability Workshop, held in honor of Earth Day. The workshop invites faculty, students and guests from industry and government to present and propose ways to maximize technology's positive impact on the long-term availability of natural resources, and to minimize its negative impact.

In "Electrons Feel the Heat: Materials for Thermal Energy Scavenging," Rabin described how his group is exploring how to capture waste heat, which accounts for about 60% of the energy produced by the fuels we burn, and convert it into electricity or other useful forms of energy. The group is investigating the fundamental science of the thermoelectric effect, which defines how electron transport and heat transport couple in materials. This has led to the development of devices that are used to increase the efficiency of energy usage. Thermoelectric devices can utilize heat normally lost to the environment to generate more electricity. As a result, there is an interest in placing thermoelectric devices in cars and power plants to produce more "work," or in the case of cars, miles per gallon. In particular, Rabin is studying how nanostructures express thermoelectric effects and in which conditions they perform better than normal materials.

In his presentation, "The Currency of the Energy Economy," Rubloff, the director of the Maryland NanoCenter, explained that the generation of clean and sustainable energy is only half of the equation: how we store and deliver that energy is just as important. Currently, there is no way to charge an electric car in the five minutes it would take to fill a gas tank. Sunlight and wind are intermittent.

"Electrical energy storage is to the energy world what currency—dollars, Euros, and yen—are to the economic world," he said, "a means to capture and hold value until needed at some other time."

Rubloff also discussed how the university's Nanostructures for Electrical Energy Storage (NEES) program, an Energy Frontier Research Center sponsored by the U.S. Department of Energy, is pursuing the science which will enable the next generation of electrical energy storage technology, directly based on nanotechnology. The NEES team is developing massive "forests" of nanowires composed of multiple materials that store and transport energy and maintain their stability while electrical charges are moved back and forth.

In his talk, "Thermoelastic Cooling: Shape Memory Alloys as a Novel Solid State Refrigerant," Professor Ichiro Takeuchi presented the latest developments in his group's efforts to design materials that can be used in more efficient cooling systems. Takeuchi and his colleagues, including MSE professor Manfred Wuttig, previously developed a two-state solid coolant that can take the place of fluids used in conventional refrigeration and air conditioning compressors. The alloy alternately absorbs or creates heat in much the same way as a compressor-based system, but uses far less energy, has a smaller operational footprint, and avoids the use of fluids with high global warming potential. Takeuchi's team recently won the University of Maryland's Office of Technology and Commercialization's physical science Invention of the Year Award for its work on the project.

The team is currently working on a cooling system design that employs commercially available thermoelastic wires. Using a simple hand-held device, Takeuchi demonstrated how one of these wires gave off heat when put under mechanical stress, and became cool when released. He also presented a 30W, hand-cranked device based on the same technology capable of cooling a water sample.

In "Low Temperature Solid Oxide Fuel Cells: A Transformational Energy Conversion Technology," Wachsman (joint; Department of Materials Science and Engineering), the director of the University of Maryland Energy Research Center, discussed his group's recent advances in the development of solid oxide fuel cells. These cells have the flexibility of operating on hydrogen or diesel fuel, which could make them feasible for use in vehicles before a hydrogen fuel infrastructure is in place, and allow them to remain functional after. His team is also working on reducing the cells' operating temperature to 600°C or lower in order to make them safe for automobiles. Wachsman also described his work on other types of fuel cells that could be used to power a home. Advances in cathode technology could provide ten times the power density—about 10W per cm³—at half the operating temperature than the commercially available cells currently sold by Bloom Energy.

Video of all of the event's presentations can be accessed from the Clark School Engineering Sustainability Workshop web site »

Published April 26, 2011