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Energetic Research

All across campus, MIT is working on a big problem.

When President Susan Hockfield began her tenure last year, she asked faculty and students what the Institute’s top research priorities should be. The overwhelming response: energy.

“If we could provide cheap energy for everyone, we could uplift the world in ways we can’t foresee,” says Vladimir Bulovic. (Photograph by Asia Kepka)

Ernest Moniz, physics professor and codirector of the Laboratory for Energy and the Environment, explains that the energy problem has three parts. First, he says, with the economic emergence of developing countries, a simple supply and demand equation will keep prices high. Meanwhile, dependence on oil under the ground of other countries creates security risks for Western nations. And third, people are finally beginning to recognize the realities of climate change. “This may be one of those rare moments when our society suddenly looks at itself in the mirror and admits the truth,” says Hockfield. We have cheap and abundant fossil fuels to thank for our comfortable lives, she says, but if we don’t change our consumption habits, the price will be steep.

Soon after her inauguration, Hockfield established the Energy Research Council (ERC), which has proposed a three-part interdisciplinary research plan: basic science that will provide a foundation for future technologies, work aimed at improving today’s energy systems, and technology and systems that address the needs of a rapidly developing world. The council, cochaired by Moniz and Robert Armstrong, professor and head of chemical engineering, also proposed changes to the curriculum to encourage students to work on energy-related problems and recommended a major drive to improve energy efficiency on campus. At press time, the proposals were awaiting approval from the president’s and provost’s offices.

In May, when the ERC reported its findings to a packed Kresge Auditorium, President Hockfield said that energy research at MIT is “lots of flowers and no garden.” MIT researchers are making headway, she said, but “these discrete breakthroughs will have far more impact as parts of a coherent answer to the world’s energy problems.” That answer will be informed by political science, economics, and other disciplines, Hockfield observed, because “as a problem, energy is hydra-headed. Concentrating on one set of fangs while ignoring the others is hardly a strategy for self-preservation.” Here’s a look at three MIT researchers working on the problem.

Vladimir Bulovic: Solar Booster

Peering through a glass panel into a 13-foot-long steel vacuum tube, Vladimir Bulovic seems to see another world. In chambers branching off from the custom-built tube, he and his students make films that may one day provide an inexpensive boost to the efficiency of silicon solar cells. “If we could provide cheap energy for everyone, we could uplift the world in ways we can’t foresee,” says Bulovic, associate professor of electrical engineering and computer science.

Bulovic builds devices from electrically and optically active thin films of precisely placed molecules. These films can consist of semiconducting crystals called quantum dots (only 10 atoms across) or organic semiconducting dyes with names like copper stellacyanin. Bulovic keeps the films inside a vacuum during the manufacturing process; even the layer or two of water molecules from the air that would accumulate on a film if he carried it across the room would totally change its properties. But the vacuum is as sterile as outer space.

Bulovic compares his devices to cakes with layers of variously flavored icing and pastry. A typical device starts with a piece of glass coated with a transparent electrode. On this are deposited layers of quantum dots and other semiconducting molecules. When light shines on the film, photons hit the quantum dots and molecules, imparting their energy to electrons. These “excited” electrons move farther away from their base atoms; some break free and travel through the layers of the film to the electrode. The resulting current could power, say, a light bulb attached to the device. Bulovic’s lab works closely with chemistry professor Moungi Bawendi, a pioneer in quantum-dot research, and his students.

Bulovic’s solar-cell research has its roots in his work on light-emitting devices. “I learned how to take electrons, put them into molecules, and get out a photon,” he says. But putting in photons and getting out electrons is more difficult. Bulovic says commercially available silicon-based solar cells typically convert just 8 to 12 percent of sunlight into electricity. The organic photovoltaics he made before turning to quantum dots did no better than 3 percent.

Nanostructured materials will probably supplement, not replace, the silicon in solar cells, says Bulovic. Silicon is inefficient at converting ultraviolet light into electricity; but nanomaterial films could turn it into green light that silicon can absorb. Likewise, silicon can’t absorb infrared light, and “a good chunk of the sun’s light is there,” Bulovic says. “You can engineer a second solar cell in tandem with silicon to absorb these wavelengths.”

Bulovic imagines that nano solar-cell films could be printed like newspapers. “There is nothing different about it except for the need for precision in placement of the nanomaterials,” he says. “We may not need high-efficiency [solar] cells if the process is cheap enough.” (He notes, however, that less efficient devices would have to cover more area.) Though the idea of harnessing solar power is old, the costs of implementing it have made it impractical for most people. Tandem silicon and nanomaterial solar cells that tap the infrared spectrum might generate about 5 percent more energy than silicon alone, Bulovic says.

“We receive 10,000 times more energy from the sun than we spend,” he says. “If we can capture that, we can power the world many times over.”

Leon Glicksman: Less Is More

As the demand for energy escalates worldwide, MIT scientists are working on nuclear fusion, cheap solar panels, and more-efficient biofuel-producing microbes. But Leon Glicksman approaches the energy problem from a different perspective.

“People are always talking about how we can generate more energy,” says Glicksman, a professor of mechanical engineering and head of the architecture department’s building technology program. “But what about how we can use less?” Glicksman studies the physics of energy-efficient building design, then builds design tools to help architects incorporate energy-efficient features, such as natural air ventilation systems, into their buildings.

More-efficient ventilation could make a tremendous difference in the United States, where, Glicksman says, buildings consume 40 percent more energy than transportation (which gets so much attention as gas prices rise). He adds that residential and commercial buildings use 39 percent of the country’s total energy and about two-thirds of its elec­tricity. “In commercial buildings, the majority of that energy is used for heating, cooling, and lighting,” says ­Glicksman, who notes that most windows in high-rises cannot be opened.

The idea behind natural ventilation is simple: rather than sealing up a building and controlling its internal tempera­ture with a system of ducts, fans, and air chillers, architects and engineers could create systems that facilitate the natural flow of outside air using as little energy as possible. Glicksman says the air inside buildings is generally warmer than outside air. In an unsealed building, this temperature gradient creates a “chimney effect”: the denser, cooler air flows in, causing the warmer air to rise. “In some instances, you can add fans to assist the ventilation,” Glicksman says. “You’re using the entire building as a duct; the fan power is fairly nominal.” Design considerations, including a building’s overall shape and the placement of its windows, can also facilitate airflow. Glicksman’s studies have shown not only that natu­rally ventilated buildings save energy, but that people who live and work in them report a higher level of comfort.

Understanding the nuances of airflow requires “detailed numerical modeling using fluid dynamics,” says Glicksman. But “many architects don’t have a strong engineering background, and a lot of this stuff is Greek to them.” So he is working with a student to create software that will help architects design natural ventilation systems.

Glicksman has also built an online tool to encourage architects to plan sustainable buildings–buildings that use much less energy or rely more on renewable resources than on energy from polluting power plants. Architects can go to ­designadvisor.mit.edu and enter a future building’s location, use, and orientation and other specifications. The program, which has weather data for 30 cities around the world, then tells the designer the energy requirements for heating, cooling, and lighting the building. Using different sets of specifications, an architect can create four different scenarios for a building and use the advisor to compare their energy efficiency.

Some building owners and architects assume that energy-efficient design costs more. It doesn’t, says Glicksman, if energy efficiency is a goal from the start. He points to energy-efficient windows, which eliminate the need to install additional heat sources under windows to keep offices warm in winter. The windows cost more initially but ultimately save money because building owners don’t have to pay for the additional heating systems–or for the energy to run them.

Glicksman is intent on helping architects avoid energy-­sapping design: “We want to give designers tools to make sure they don’t repeat these mistakes in new buildings.”

Karen Polenske: Chinese Lessons

Brazil is hailed for its homegrown sugarcane-derived ethanol and its growing independence from foreign oil (see “Brazil’s Bounty,” Technology Review, July/August 2006). Meanwhile, China is decried for mining and burning its vast coal resources with little concern about environmental impact.

Karen R. Polenske, professor of regional political econo­my and planning, says that even though there are energy-use problems in China, the news isn’t all bad. Burning coal causes environmental and health problems, but while Brazil’s energy intensity–a measurement of energy used per unit of output, usually GDP–went up by 36 percent between 1980 and 2004, China’s fell by 61 percent.

In 1997, Polenske decided to investigate why. She focused on one of China’s most energy-intensive products: metallurgical coke, which looks like black lava rocks and is critical to steelmaking. Coke is made by burning coal at temperatures ranging from 900 to 1,400 °C, either in crude, highly polluting ovens or in new slot ovens that capture gaseous by-products. Her research has targeted Shanxi province, where 40 percent of the country’s coke is made.

What has she learned about why energy intensity is falling? “In China, we have shown very conclusively that it’s new technologies rather than change in industries,” she says. In 1978, China opened up to international trade and replaced 50-year-old Russian machinery. “The fact that they could import new technologies is what we think affected energy intensity,” Polenske says.

Polenske’s research is grounded in input-output analysis, a mathematical modeling method used in economics. “Input-output analysis looks at what all industries in a region produce and purchase,” she says. Simpler economic analyses take only an industry’s direct requirements into account: for example, iron and steel are directly required to make automobiles. “But iron and steel require iron ore, coke, coal,” she says. “And each of these have supply chains.” Indirect inputs, such as coal’s contribution to steelmaking, “often produce more pollution” than direct ones.

In China, people are starting to see the connection between coal and pollution, says Polenske, but most plant owners don’t have the money to replace their polluting machinery. However, the situation may improve soon. Polenske says foreign investors who have been pouring money into companies based in big cities like Beijing are redirecting their attention to industry in Shanxi as China’s demand for steel increases.

In the meantime, Polenske’s team has measured the concentration of fine particulates all around coke plants and in workers’ homes, to help demonstrate that pollution from coke production causes cancer. “Part of my desire is to get them to see what we in the U.S. are learning far too late–that these industries are highly polluting,” she says.

After years of research trips to China, Polenske is now embarking on a project to compare the country’s energy usage with that of Brazil and India, which also have major steel industries. Of the developing countries, China, Brazil, and India are the three biggest energy users, she notes. Her project will study the effects of policy on the adoption of new technologies. In Chinese industry, adoption of new technology is driven by the mandates of the central government; in Brazil and India, democratic republics, the picture is likely to be different.

Sidebar: Glicksman in China

Professor Leon Glicksman recently completed a project, funded by the Alliance for Global Sustainability, the V. Kann Rasmussen Foundation, and Kawasaki Heavy Industries, to recommend sustainable building strategies for China. Buildings account for only 18 percent of China’s total energy consumption, but that number is on the rise, according to Glicksman, as the country builds more than 10 million new residential units a year. Glicksman originally intended to develop energy-efficient designs, with features like natural ventilation, for Chinese buildings. But during trips to Beijing, Shanghai, and Shenzhen with researchers from Tsinghua University (Beijing’s equivalent of MIT), he says, “we saw poor construction quality, loosely fitting windows, buildings with enclosed balconies that end up with a greenhouse effect.”

“We changed our emphasis to simple design ideas and technologies,” says Glicksman, who taught classes in China for architects and developers. He and his Chinese collaborators have published a book of recommendations that take into account local materials and building methods, as well as what’s affordable.

Professor Leon Glicksman recently completed a project, funded by the Alliance for Global Sustainability, the V. Kann Rasmussen Foundation, and Kawasaki Heavy Industries, to recommend sustainable building strategies for China. Buildings account for only 18 percent of China’s total energy consumption, but that number is on the rise, according to Glicksman, as the country builds more than 10 million new residential units a year. Glicksman originally intended to develop energy-efficient designs, with features like natural ventilation, for Chinese buildings. But during trips to Beijing, Shanghai, and Shenzhen with researchers from Tsinghua University (Beijing’s equivalent of MIT), he says, “we saw poor construction quality, loosely fitting windows, buildings with enclosed balconies that end up with a greenhouse effect.”

“We changed our emphasis to simple design ideas and technologies,” says Glicksman, who taught classes in China for architects and developers. He and his Chinese collaborators have published a book of recommendations that take into account local materials and building methods, as well as what’s affordable.

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