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Behind every technological breakthrough that grabs headlines are scores of smaller-scale studies aimed at improving the way existing products and systems work. Often, the innovations in product or system design that result from such studies are difficult to envision: Who could have guessed that the chunky blocks of plastic that passed for mobile phones 15 years ago would evolve into the multifunctional, slim-as-a-credit-card fashion accessories they are today? In this feature—really a series of four featurettes—we highlight research projects in energy efficiency that point the way toward substantial improvements in the way buildings use (or harvest) power. How about thin, flexible solar cells that can be ordered by the roll, like paper? Or using your laptop to dim the lights and turn off the air-conditioning in your office when you step out at lunchtime? The science behind these scenarios is there, even if all the technological details and cost issues haven’t been resolved yet. As energy prices remain uncertain, it’s likely that owners will have more incentives in the future to employ strategies that curtail energy usage, whether for retrofits or new construction. Imagining what form those solutions might take—as these researchers are doing—is half the fun. - Deborah Snoonian, P.E.

This diagram shows the design of a flexible solar cell containing a layer of “quantum dots” that harvest sunlight, pioneered by the University of Toronto.

Tapping solar radiation’s unseen benefits

Most designers think of sunlight as a destructive force when it comes to surface treatments. They look for UV-stable paints and coatings, and calculate life-cycle costs with the expectation of regularly replacing exposed surfaces. But recent advances in materials science point to coverings—even paints and fabrics—that double as solar cells. Instead of worrying about the deleterious effects of the sun, designers could look forward to using a variety of building materials that have embedded energy-producing capacity.

Researchers at the University of Toronto, in Canada, have expanded the range of solar radiation that such materials can harvest, tapping infrared rays as well as the visible spectrum of light (current solar technology works in the visible spectrum only). This could boost the efficiency of new photovoltaic materials and make them more affordable; it also opens the way for cheap infrared cameras, which could figure in building-security systems.

The researchers’ infrared-active colloidal “quantum dots” are made up of lead sulfur nanocrystals and semiconducting plastic. By changing the size of the nanocrystals, the researchers can “tune” the quantum dots to absorb wavelengths from 800 to 2,000 nanometers.

Within five years or so, architects and builders might be able to specify rolls of thin, lightweight, and flexible plastic solar sheeting, made by spraying a solvent containing the nanocrystals onto a thin, flexible substrate within a controlled manufacturing environment. Manufacturers might also choose to coat glass or metal surfaces with the solvent, according to lead researcher Ted Sargent, a University of Toronto professor of electrical and computer engineering. Applying the solvent like paint to such materials in the field won’t work, says Sargent, because the process needs to be carried out in a controlled, clean environment to be successful.

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