Shameday, shadows and light could team up to provide power. A new device uses the contrast between bright spots and shade to create an electric current . that current can power small electronice, such as a watch or LED lights.
By using shade ,"we can harvest energy anywhere on earth, not just open spaces,"says swee ching tan.he is a materials scientst who work at the national university of singapore.
someday,these generators might produce energy in shadawy spots between skyscrapers, he says,or even indoors.
tan and his team call their new device a shadow-effect energy generator. trhey made it by coatng silicon with a thin layer of gold.
silicon is often used in solar cells that produce electricity from sunlight.
Electrons are one of the particles that make up atoms. they have a nagetive electic charge .
as in a solar cell,
light shining on this generatorenergizes electrons in the silicon.
those electrons then jump into the gold.voltage is a measure of electrical potential energy, a type energy related to an object's condition(and not it's motion). light boost the voltage of the light metal, making it higer than in the dark part of the generator. electrons flow from high to low voltage . so the defference in light levels creates an electric current . sending electrons through circuite makes a flow of current that can power a small gedget.
than's team described it's new device april 15 in energy &environmental science.
each device measures 4 centineters(1.6inches) long and 2 centimeters wide. that makes its area slightly larger than a postage steamp.
in low light, eigt generators powerd an electrinice devices also can serve as self-powered motion sensors. for instance, when a toy car passed by, its shadow fell ion a generator. that createdenough electricity to light and LED.
"This is a creative way to think about how we can make energy from the world around us," says Emily Warren. she is a chemical engineer at the national Renewable Energy Laboratory. its in Golden, Colo."whenever you make energy you have a defference in somthing ," explains warren ,who did't take partv in the new work. water fallin from a high place to a low place can create energy.
so can a defference in temperature. even solarcells rely a defference in some property. in some solar cells, defferences in the meterial properties can creat energy under light. the team compared it's generators to commercial solar cells that are typically used under fullb sunlight.
with half of eacg device in shadow , the generatorsproduced roughly twice as much power per serface area as the soler cells. but,warren notes, it would be better to compare then to soler cells meant to work in low light, such as the siliconsoler cells in classroom calculators. these are designed to used indoor light. warren also would like to see the team measure the power the devices make over a longer time , such as a whole day.
Boosting how much light the generators can absorb would allow them to make better use of shadows. so the tem is woking to improve the device's performance with strategies that solar cells use to gether light ."A lot of people think that shadows are useless," Tan notes. But "anything can be useful, even shadows."