Science & Technology

Scientists design “smart” devices for harvesting sunlight

A “smart” device for harvesting sunlight.Credit: NTU Singapore

This device can be used to illuminate dark underground spaces during the day.

A team of researchers at the Nanyo University of Science and Technology (NTU Singapore) in Singapore have designed “smart” devices that collect sunlight and relay it into underground space, reducing the need to utilize traditional lighting energy sources.

In Singapore, authorities are exploring the feasibility of digging deep underground to create new space for infrastructure, storage, and utilities. Therefore, it is expected that the demand for 24-hour underground lighting will increase in the future.

To develop a daylight collector that could sustainably meet this need, the NTU team was inspired by a magnifying glass that could be used to focus the sunlight on one point.

Acrylic ball solar concentrator

The device’s acrylic ball (right) acts as a solar concentrator, allowing sunlight to form a sharp focus. The focused sunlight is collected at one end (left) of the fiber optic cable and emitted directly from the other end.Credit: NTU Singapore

They used off-the-shelf acrylic balls, a single plastic fiber optic (a type of cable that carries a beam of light from one end to the other), and a computer chip assist motor.

The device is placed on the ground, like a magnifying glass lens, allowing the acrylic ball to act as a solar concentrator, allowing parallel sun rays to form a sharp focus on the opposite side. The focused sunlight is collected at one end of the fiber optic cable and carried along it to the underground located end. The light is then emitted directly from the end of the fiber cable.

At the same time, with the help of computer chips, a small motor automatically adjusts the position of the fiber collecting ends, optimizing the amount of sunlight that can be received and transported as the sun moves across the sky.

Bright idea: Thanks to scientists at NTU Singapore who built a “smart” device to harvest sunlight to illuminate the underground space, it is now possible to bring sunlight underground. A device shaped like a crystal ball, like a magnifying glass, concentrates sunlight at one point, collects it at one end of a fiber optic cable, and then carries it to the other end, which is located underground, where it delivers light. Release. This reduces the need to utilize traditional energy sources for lighting.Credit: NTU Singapore

Developed by Assistant Professor Yoo Seongwoo of the Department of Electrical and Electronic Engineering and Dr. Charu Goel, a senior researcher at NTU’s Photonics Institute, the innovation was reported in a peer-reviewed scientific journal. Solar energy Earlier this month.

This device overcomes some limitations of current solar harvesting technology. In traditional solar concentrators, a large curved mirror is driven by a rugged motor to align the mirror plate with the sun. The components of these systems are also exposed to environmental factors such as humidity, which increases the need for maintenance.

However, the NTU device is designed to use the round shape of an acrylic ball, removing the rugged motor system to align it with the sun and make it compact.

The prototype designed by the researchers weighs 10 kg and has a total height of 50 cm. To protect the acrylic balls from environmental conditions (ultraviolet, dust, etc.), researchers also used polycarbonate to create a transparent dome-shaped cover with a thickness of 3 mm.

A device compact enough to be installed as a streetlight post

Assistant Professor Yoo, the lead author of this study, said: Due to space constraints in densely populated cities, sunlight collection systems are intentionally designed to be lightweight and compact. This makes it convenient to integrate our devices into the existing infrastructure of the urban environment. “

Yoo Sung Woo Char Goel

The researchers behind the “smart” devices for collecting sunlight are Assistant Professor Yoo Sung-woo (left) of the Department of Electrical and Electronic Engineering and Dr. Char Goel (right), a senior researcher at NTU’s Photonics Institute.Credit: NTU Singapore

The NTU team believes this device is ideal for ground-based installation as a traditional streetlight pole. This allows innovation to be used in two ways. One is a device that collects sunlight during the day and illuminates the underground space, and the other is a street light that uses electricity to illuminate the ground at night.

Research by NTU scientists is an example of NTU’s smart campus vision aimed at developing technologically advanced solutions for a sustainable future.

“Smart” automatic positioning for maximum sunlight harvest

As the sun moves across the hollow for a day, so does the position of the focused sunlight in the acrylic ball. The system uses a computer chip-based mechanism to track the sun’s rays so that maximum sunlight is collected and carried to fiber optic cables throughout the day.

The Global Positioning System (GPS) coordinates of the device location are pre-loaded into the system, allowing you to determine where the maximum sunlight is at any given time. It then uses two small motors to automatically position the fibers, capturing and transporting sunlight from the focused location at 1-minute intervals.

To ensure the device’s auto-positioning capabilities, a pair of sensors that measure the brightness of the light are also placed around the solar collection end of the fiber optic cable. When the sensor detects a discrepancy in the light readings, a small motor automatically activates to adjust the position of the cable until the sensor values ​​are the same. This shows that the fiber captures as much sunlight as possible.

When it’s not enough to collect sunlight and bring it underground in the rain or overcast sky, an electrically powered LED bulb located right next to the radiating end of the fiber optic cable will automatically light up. This allows the device to illuminate the underground space all day long without interruption.

Better performance than LED bulbs

In a pitch-black warehouse experiment (to simulate an underground environment), NTU researchers found the device’s luminous efficiency (a measure of how well a light source produces visible light using 1 watt of power). Was found to be 230 lumens / watt. ..

This far exceeds that recorded by commercial LED bulbs with a standard output of 90 lumens / watt. The quality of the light output of NTU smart devices is also comparable to the much more expensive daylight collection systems currently on the market.

Dr. Charu, the lead author of this study, said: “The luminous efficiency of our low-cost devices has proven to be ideal for low-level lighting applications such as parking lots, elevators, and dense underground walkways. Cities. It can also be easily expanded. Ball lenses Because the light-collecting capacity of the device is proportional to its size, the device can be customized to the desired output light power by replacing the device with a larger or smaller ball.

Michael Chia, Managing Director and Research Collaborator at Technolite, a Singapore-based lighting-focused design agency, said: We have commercial and application knowledge, but NTU’s deep know-how from a technical point of view has taken project execution to the next level beyond our expectations. “

Going forward, lighting companies are looking for ways to incorporate smart devices or related concepts into their industrial projects to improve efficiency and sustainability.

Reference: “Hybrid Daylight Collection System Using Static Ball Lens Condenser and Movable Optical Fiber”, Charu Goel and Seongwoo Yoo, January 28, 2021 Solar energy..
DOI: 10.1016 / j.solener.2020.12.071

Scientists design “smart” devices for harvesting sunlight Scientists design “smart” devices for harvesting sunlight

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