NTU researchers design 'smart' device to harvest sunlight for underground spaces

The device was designed by Assistant Professor Yoo Seongwoo (left) and Dr Charu Goel.
The device was designed by Assistant Professor Yoo Seongwoo (left) and Dr Charu Goel.PHOTO: LIANHE ZAOBAO

SINGAPORE - Researchers from Nanyang Technological University have designed a "smart" device to harvest daylight and relay it to underground spaces.

They did this by mimicking the way a magnifying glass is used to focus sunlight onto a single point.

The device was designed by Assistant Professor Yoo Seongwoo from the School of Electrical and Electronics Engineering and Dr Charu Goel, principal research fellow at NTU's The Photonics Institute.

The prototype, which weighs 10kg and is 50cm tall in total, comprises an acrylic ball, a single plastic optical fibre - a type of cable that carries a beam of light from one end to another - and computer-chip-assisted motors.

"Our innovation comprises commercially available off-the-shelf materials, making it potentially very easy to fabricate at scale," said Prof Yoo on Wednesday (March 31).

The acrylic ball lens acts as the solar concentrator, enabling parallel rays of sunlight to form a sharp focus at its opposite side.

The optical cable, with one end sitting on a slider under the ball lens, then collects and relays harvested sunlight to underground spaces via the other end.

Meanwhile, the computer chip-assisted motors automatically adjust the position of the fibre's collecting end to optimise the amount of sunlight that can be received and transported as the sun moves across the sky.

The prototype can relay optimal output of sunlight at up to two levels underground.

However, Dr Charu said that the device is scalable and may be able to relay optimal output of sunlight up to 10 levels underground if glass fibres are used instead of plastic optical cable.

"Since the light-capturing capacity of the ball lens is proportional to its size, we can customise the device to a desired output optical power by replacing it with a bigger or smaller ball," she added.


The prototype weighs 10kg and is 50cm tall in total. PHOTO: LIANHE ZAOBAO

In experiments in a pitch-black storeroom - to simulate an underground environment - the NTU researchers found that the prototype produced more visible light than commercially available LED bulbs.

As the Singapore authorities look into the feasibility of creating new infrastructure, storage and utility spaces underground, NTU said this smart device addresses future demand for round-the-clock lighting in underground infrastructure.

Technolite, a Singapore-based design-focused agency specialising in lighting, is currently in the development stages of producing and incorporating the device for real-life consumption.

"While we have the commercial and application knowledge, NTU's in-depth know-how from a technical perspective has taken the execution of the project to the next level that is beyond our expectations," said Mr Michael Chia, managing director at Technolite.