| Fall 06: Research: Energy’s Future Happens Here
A new Rensselaer center explores the vanguard of a pressing global issue
Central
lighting. Superconducting wires. Nanophosphors. For a place dedicated to
conserving energy and to developing renewable energy resources, Rensselaer’s
Center for Future Energy Systems
is abuzz with it—in the form of ideas.
Just a little over a year old, the center has taken an active role in drawing together the myriad strands of energy research at Rensselaer. In fuel cells and solid-state lighting, distributed generation and nanotechnology, the drive is the same: to achieve breakthroughs that will provide major gains in energy efficiency and renewable energy.
Lighting Gets Smarter
“The conventional wisdom is that improvements in lighting efficiency can only be incremental,” said Nag Patibandla, the center’s director. “But decades ago, researchers made the leap from incandescent to fluorescent. Where is the next logical step in the progression?”
The answer, according to Rensselaer researchers, is solid-state lighting—the use of light-emitting diodes (LEDs) that could be four times as efficient as compact fluorescents. In this research, the Center works closely with Rensselaer’s Future Chips Constellation, which recently received a $1.8 million grant from the U.S. Department of Energy (DOE) to improve the power and efficiency of green and deep green LEDs.
Those two colors represent the field’s current state of the art. DOE’s ultimate goal, however, is to create a white LED by 2025. “Right now we create white light by mixing colored LEDs,” Patibandla said. “But actually developing a white LED would greatly improve light quality and energy efficiency.”
Toward that end, the center is sponsoring research from the nano arena. Because LED technology relies on quantum-sized phosphor particles—and different particles produce different wavelengths—a research team is working to create particles that will generate white light.
The center-sponsored LED research could lead to all kinds of applications: in-wall lighting turned on by a simple touch, central remote controls for lighting (analogous to central air and central heating), advanced sensors, timers, and more.
How important is lighting to the total energy picture? “Twenty-five percent of the total energy use in the United States is used in lighting,” Patibandla said. “So any leaps forward in efficiency here would make a significant impact.”
Bandgaps Get Broader
Most people think of solar energy as energy-efficient. But how do you convert the sun’s rays effectively to electric current? Behind that question lies a specific problem that the center is actively investigating.
“In simple terms, only a small fraction of all the photons from sunlight will have the proper energy to generate electrons for electric current,” Patibandla explained. “The challenge, then, is to put as many of those photons to work as possible.”
Therein lies the problem with current materials, which have narrow bandgaps (the difference between the valence band and conduction band of energy values). The narrower the bandgap, the fewer the appropriate photons that the material can capture.
To overcome this problem, the center works with Rensselaer researchers who are striving to create higher-bandgap materials for microelectronic and nanoelectronic applications. “These same materials can use a much broader spectrum of the sun’s energy to generate electricity at much higher efficiencies than today’s photovoltaic materials,” Patibandla said. “When optimized, they will provide a sufficient number of free electrons to run solar-powered applications with acceptable levels of reliability.”
Toward Wires Without Resistance
What if someone created a wire with almost no resistance?
The answer would gladden the heart of large urban utilities. By using such wires to replace copper cables of the same size, they could increase transmission capacity by a factor of three to five. That, in turn, would enable them to keep up with today’s skyrocketing demand—without squeezing more cables into their tightly packed underground networks.
The center’s research into high-temperature superconductivity (HTS) aims at making just such a wire out of ceramic. The major challenge is that wires of this type are exceptionally difficult to manufacture; as part of resolving this challenge, the center’s research is currently focused on second generation, yttrium-based HTS materials. (A first-generation, bismuth-based HTS cable is currently being installed as part of a demonstration project in Albany, New York.)
Patibandla and colleagues are also excited about the HTS cables’ potential bi-directionality—the ability to use the grid in either direction as a real long-term prospect. This property will become essential in a clean and renewable distributed-generation landscape.
Distributing Generation
In tried-and-true electricity generation, where nearly all electricity is generated at a central plant, the voltage differential between plant and users carries the current forth. But what happens when generation is more broadly distributed?
Center researchers are working to understand the dynamics of current flow in that new landscape—and how to ensure reliable supply.
“Let’s say an industrial customer introduces a fault into the grid,” Patibandla said. “A photovoltaic or fuel cell system in a nearby building could interpret that as a power outage and shut itself off. We want distributed generation to work so that when all these devices are connected to the grid, that grid works at its current level of reliability or better.”
Finding the answer will soon be critical. Several alternative technologies lend themselves to generating energy closer to the user: think fuel cells and solar panels. The more that users themselves become generators, the more they will need a grid that adapts with them.
…and Beyond
To say that the Center for Future Energy Systems is just getting started is true on several levels. Even beyond the current research, Patibandla is exploring relationships with industry and universities to explore a range of areas, from the use of carbon nanotubes for hydrogen storage to the conversion of corn stalks into biofuels.
“Anywhere we can contribute to the future of energy, we will seek to make that contribution,” he said. “Already we have brought together many institutions to create interesting synergies. The more synergies we create, the more potential solutions to benefit our world.”
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