Weather could power the next generation of smart windows. Researchers have created glass by harvesting energy from wind and precipitation(降水). The approach offers an alternative to other smart windows powered by batteries, solar panels, and even standard power outlets." The creation represents a new kind of renewable energy source, "says Liming Dai, a nanomaterial engineer at Case Western Reserve University in Cleveland, Ohio, who was not involved in the research.
Smart glass, which changes its characteristics to block out light, has been around for decades. Common examples include glarefighting rearview(后视) car mirrors and windows that change color for energy savings and privacy. But many are expensive, and people are still looking for ecofriendly ways to power the windows. Batteries and plugin outlets aren't apparently "green", and builtin solar panels can cloud or hide parts of the glass.
In experiments, the glass produced up to 130 milliwatts per square meter, enough to power a pacemaker or a smart phone while it's asleep, the team reported online last month in ACS Nano. This output might suit many applications, such as being a power source for home or office electronics, says codeveloper and scientist Zhong Lin Wang of the Georgia Institute of Technology in Atlanta. Since their first project in 2012, a lightup sidewalk powered by footsteps, he and his colleagues have miniaturized（使小型化） their generators（发电机） to create everything from selfcleaning keyboards to sensors for security systems.
But Wang and his colleagues still have more work to do before this smart glass is ready for commercialization. Now, the glass has no way to store the energy it creates. To solve this problem, Dai says, transparent super capacitors(电容器) could be placed into the glass without decreasing visibility.
For now, the team wants to improve the energy efficiency of their nanogenerators. These tiny power plants can convert about 60% of the mechanical energy that they collect into electricity. "The output power is a constant goal, "Wang says."Free energy surrounds us, and anything can happen if you take control of it."
