When it comes to regular photovoltaic panels, the fewer shadows that are cast upon them, the better. An experimental new device, however, actually generates electricity via the contrast between shadows and light on its surface.
Developed by scientists at the National University of Singapore, the tool is what's known as a shadow-effect energy generator (SEG). The current prototype is made up of a flexible transparent plastic base along with four cells, each one of which consists of a thin gold film deposited onto a silicon wafer. These cells are cheaper to produce than comparable silicon solar cells.
When the whole SEG is placed either entirely in the light or in a shadow, it generates little if any electricity. However, when part of it is exposed to light and part of it is shadowed, a voltage difference occurs between the lit and unlit sections. This difference in turn produces a significant electrical current.
In lab tests conducted under partly-shadowed indoor lighting, the SEG was able to power small devices such as a digital watch. It performed best when half in light and half in shadow, as this arrangement provided equal areas for charge generation and storage, respectively. In fact, it was twice as efficient as a similar-capacity photovoltaic panel in the same conditions.
Along with being able to power small gadgets under less-than-optimal lighting, SEGs could also serve as motion sensors – when a moving object casts a shadow across one of the devices, it causes a detectable electrical current to be generated.
The scientists are now looking into replacing the gold with a cheaper material, in order to further reduce the cost of the technology.
A paper on the research, which is being led by Asst. Prof. Tan Swee Ching and Prof. Andrew Wee, was recently published in the journal Energy & Environmental Science.
Source: National University of Singapore