A breakthrough in concentrated photovoltaics may soon be available.
Revisiting a largely abandoned concept from three decades ago, a research team at MIT has developed a new solar concentrator that is cost-effective as well as energy-efficient. Advocated as a better way of utilizing the sun's energy output, and practically doubling the performance of existing solar panels while greatly simplifying the process, this development could make photovoltaic systems much more commercially viable in the coming years.

Most large-scale solar power operations are set up as systems of rotating mirrors that follow the path of the sun over a wide region and channel its rays into solar cells — silicon-based semiconducting devices that collect and store the energy. Cooling systems are in constant use to keep the large solar panels containing the devices from overheating. This method is less effective, more expensive, and more cumbersome than it should be, critics have long complained. The result is that energy from fossil fuels is currently still much cheaper to produce on a large scale. However, that may change soon, thanks to the MIT researchers, led by assistant professor of electrical engineering Marc Baldo.

In the MIT project, luminescent solar concentrators resembling windows absorb the sun's rays via thin films of organic color dyes that are applied in specific ratios to the surface of the glass panels. The light is then reemitted through the glass to small solar cells positioned around the edges of the panes. These solar cells take up less space, utilize less semiconducting material, and do not require extensive cooling systems or separate panels to house them. The “windows” themselves also occupy less space than the mirror system.

The glass panels can gather light while remaining stationary, they increase efficiency up to 50%, and the light can travel much farther. “We were able to substantially reduce light transport losses, resulting in a tenfold increase in the amount of power converted by the solar cells,” says team member Jon Mapel.

Ultimately, the cost-effectiveness of the new system may be its greatest advantage. After all, if ordinary pieces of glass can be converted into high-tech solar concentrators, then the technology becomes that much more accessible. Current systems could even be retrofitted with the new concentrators at very little cost. All of this will go a long way toward making the cost of solar electricity more competitive with that of the conventional grid energy.

According to the research team, if everything goes as planned, practical and affordable solar energy could be available on the market within the next three years. Three of the inventors on the team (Michael Currie, Jon Mapel, and Shalom Goffri) have just launched a start-up, Covalent Solar, with the help of several entrepreneurial grants from MIT, to commercialize the technology. For now, ensuring that it will come with at least a 20-year guarantee is the next step (the color-dye process currently remains stable for about three months). The team is already hard at work finding ways to increase the stability of these potentially revolutionary photon collectors. — Aaron M. Cohen

Sources: MIT, News Office, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139. Web site.

National Science Foundation, 4201 Wilson Boulevard, Arlington, Virginia 22230. Web site.

The Scent of the Future

Consumers didn't need to be told that Jazz Diet Pepsi was about to hit store shelves; they could smell it. The soft-drink company had placed an ad laced with scents of black cherry and French vanilla in the October 2006 edition of People magazine.

Four months later, British travel agency Thomson Holidays sprayed its store windows with a scratch-and-sniff scent of coconut suntan lotion, in order to remind those passing by that they, via Thomson Holidays, could leave February's icy chill for beaches in sunnier climes.

Since catchy jingles and flashy graphics are ubiquitous, many companies are hoping that nice smells will prove a new way to attract c