May 26, 2010
The United States has talked about the potential benefits of solar energy since the days of Jimmy Carter's presidency. To date, the technology has had a minimal effect on the nation's energy supply, but that may soon change, thanks to the work of researchers at the Massachusetts Institute of Technology.
Known for its top-notch engineering program, the university has recently taken the lead in energy research. In the fall of 2006, the academic institution forged the MIT Energy Initiative (MITEI), a program designed to bring all of the university's top minds together to work on solving energy problems. "MITEI represents the largest cross-campus initiative that MIT has ever undertaken," noted Ernest Moniz, director of the MITEI and a member of President Obama's Council of Advisors on Science and Technology. Approximately 20 percent of the faculty is working on various energy projects, and half of them have never focused on energy issues before.
Much of the effort has centered on clearing the hurdles evident with solar energy. The work of two faculty members, Marc Baldo, associate professor in MIT's Department of Electrical Engineering and Computer Science, and Dan Nocera, professor of energy, have made it out of the labs and into commercial ventures that are poised to address current solar energy shortcomings.
Although the sun has the potential to deliver a steady stream of energy, its use has been hamstrung by a variety of problems. One problem has been that the panels and cells used to store and conduct solar energy are expensive and inefficient, capturing only about 10 to 20 percent of the available energy.
Baldo is attacking these problems. Traditionally, these devices have been made of highly refined silicon -- mainly because its properties are well known and its performance can be tightly controlled. However, to mimic the sun's movement and harness its energy, this approach requires a complex series of curved mirrors or lenses, which are bulky, mechanical and costly. As a result, utilities need to deploy large solar cells to house the energy required. "The bigger the solar cells are, the more they cost," explained Baldo.
To drive down costs, his group took a different approach. Rather than use silicon, Baldo opted for glass sheets and off-the-shelf dyes used in car paints. Here, energy concentrators act as waveguides and channel light in the same way that fiber-optic cables transmit optical signals over long distances. As a result, solar economics are turned upside-down. The larger the surface of the glass compared with the thickness of the edges, the more the light is concentrated and the less the power costs. Another plus is that the system features a tandem solar module that captures more of sunlight's energy than single-function systems collect.
The end result is these new converters transform nearly twice the energy from sunlight as conventional solar cells do, which results in a 30 to 40 percent decrease in the cost of solar electricity. To exploit the technology, Baldo founded Covalent Solar, which is also based in Cambridge.
One solar energy challenge has been providing power at night when there is no sunlight. Nocera turned to photosynthesis to solve that problem. He has developed catalysts that divide water molecules and then create and store energy. Any excess capacity generated during the day is stored as hydrogen and oxygen, and then used in fuel cells at night whenever it is needed.
Several Hurdles
The MIT professor had to clear several hurdles to develop a commercially viable product. His system had to work with any type of water. Traditionally, electrolyzers have also been very expensive, but the one Nocera developed is produced using inexpensive PVC plastic. Historically, the platinum electrodes used in electrolysis work well for splitting off the hydrogen, but platinum does not mesh with oxygen. The MIT catalyst uses a new conductor that works well with oxygen.
After filing a series of patents for his approach, Nocera founded Sun Catalytix.
The MIT researchers are trying to ensure that solar energy becomes a key component in the U.S. energy supply. The goal is to get it done sooner rather later, particularly while Barack Obama presides and his priorities are the development of green energy.
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Paul Korzeniowski
