Illuminating Dark, Underground Spaces: Scientists Design “Smart” Device to Harvest Daylight

By NANYANG TECHNOLOGICAL UNIVERSITY

Device can be used to illuminate dark, underground spaces in daytime.

A team of Nanyang Technological University, Singapore (NTU Singapore) researchers has designed a ‘smart’ device to harvest daylight and relay it to underground spaces, reducing the need to draw on traditional energy sources for lighting.

In Singapore, authorities are looking at the feasibility of digging deeper underground to create new space for infrastructure, storage, and utilities. Demand for round-the-clock underground lighting is therefore expected to rise in the future.

To develop a daylight harvesting device that can sustainably meet this need, the NTU team drew inspiration from the magnifying glass, which can be used to focus sunlight into one point.

The acrylic ball (right) of the device acts as the solar concentrator, enabling sunlight to form a sharp focus. The focused sunlight is then collected into one end of a fiber cable (left) and emitted via another end directly. Credit: NTU Singapore

They used an off-the-shelf acrylic ball, a single plastic optical fiber — a type of cable that carries a beam of light from one end to another — and computer chip-assisted motors.

The device sits above ground and just like the lens of a magnifying glass, the acrylic ball acts as the solar concentrator, enabling parallel rays of sunlight to form a sharp focus at its opposite side. The focused sunlight is then collected into one end of a fiber cable and transported along it to the end that is deployed underground. Light is then emitted via the end of the fiber cable directly.

At the same time, small motors — assisted by computer chips — automatically adjust the position of the fiber’s collecting end, to optimize the amount of sunlight that can be received and transported as the sun moves across the sky.