Solar Energy

NTU Singapore scientists design ‘smart’ device to harvest daylight

Published

4 years ago

April 1, 2021

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NTU Singapore scientists design ‘smart’ device to harvest daylight

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.

They used an off-the-shelf 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.

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 fibre cable and transported along it to the end that is deployed underground. Light is then emitted via the end of the fibre cable directly.

At the same time, small motors – assisted by computer chips – 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.

Developed 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 innovation was reported in the peer-reviewed scientific journal Solar Energy early this month.

The device overcomes several limitations of current solar harvesting technology. In conventional solar concentrators, large, curved mirrors are moved by heavy-duty motors to align the mirror dish to the sun. The components in those systems are also exposed to environmental factors like moisture, increasing maintenance requirements.

The NTU device, however, is designed to use the round shape of the acrylic ball, ridding the system of heavy-duty motors to align with the sun, and making it compact.

The prototype designed by the researchers’ weighs 10 kg and has a total height of 50 cm. To protect the acrylic ball from environmental conditions (ultraviolet light, dust etc.), the researchers also built a 3mm thick, transparent dome-shaped cover using polycarbonate.

Device compact enough to be mounted as a lamp post

Asst Prof Yoo, lead author of the study said, “Our innovation comprises commercially available off-the-shelf materials, making it potentially very easy to fabricate at scale. Due to space constraints in densely populated cities, we have intentionally designed the daylight harvesting system to be lightweight and compact. This would make it convenient for our device to be incorporated into existing infrastructure in the urban environment.”

The NTU team believes the device is ideally suited to be mounted as a conventional lamp post above ground. This would enable the innovation to be used in two ways: a device to harvest sunlight in the day to light up underground spaces, and a streetlamp to illuminate above ground at night using electricity.

The research by the NTU scientists is an example of NTU’s Smart Campus vision that aims to develop technologically advanced solutions for a sustainable future.

Smart’ automatic positioning to harvest maximum sunlight

As the sun moves across the sky throughout the day, so will the position of the focused sunlight inside the acrylic ball. To ensure that maximum sunlight is being collected and transported down the fibre cable throughout the day, the system uses a computer chip-based mechanism to track the sun rays.

The Global Positioning System (GPS) coordinates of the device location are pre-loaded into the system, allowing it to determine the spot where maximum sunlight should be focused at any given time. Two small motors are then used to automatically adjust the position of the ?bre to catch and transport sunlight from the focused spot at one-minute intervals.

To guarantee the device’s automatic positioning capability, pairs of sensors that measure light brightness are also placed around the sunlight collecting end of the fibre cable. Whenever the sensors detect inconsistencies in the light measurements, the small motors automatically activate to adjust the cable’s position until the values on the sensors are the same. This indicates that the fibre is catching the maximum amount of sunlight possible.

During rain or overcast skies when there is inadequate sunlight to be collected and transported underground, an LED bulb powered by electricity installed right next to the emitting end of the fibre cable, will automatically light up. This ensures that the device can illuminate underground spaces throughout the day without interruption.

Performs better than LED bulbs

In experiments in a pitch-black storeroom (to simulate an underground environment), the NTU researchers found the device’s luminous efficacy – the measure of how well a light source produces visible light using 1 Watt of electrical power- to be at 230 lumens/Watt.

This far exceeds those recorded by commercially available LED bulbs, which have a typical output of 90 lumens/Watt. The quality of the light output of the NTU smart device is also comparable with current commercially available daylight harvesting systems which are far more costly.

Dr Charu, who is the first author of the study, said, “The luminous efficacy of our low-cost device proves that it is well-suited for low-level lighting applications, like car parks, lifts, and underground walkways in dense cities. It is also easily scalable. 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.”

Michael Chia, Managing Director at Technolite, a Singapore-based design focused agency specialising in lighting, and the industry collaborator of the research study said, “It is our privilege and honour to take this innovation journey with NTU. While we have the commercial and application knowledge, NTU in-depth knowhow from a technical perspective has taken the execution of the project to the next level that is beyond our expectations.””

Moving forward, the lighting company is exploring ways to potentially incorporate the smart device or its related concepts into its industrial projects for improved efficiency and sustainability.

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Solar Energy

Scientists Probe Declining Earbud Battery Longevity

Published

1 day ago

February 5, 2025

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Scientists Probe Declining Earbud Battery Longevity

by Clarence Oxford

Los Angeles CA (SPX) Feb 05, 2025

Have you ever noticed how electronic devices, including wireless earbuds, seem to lose battery capacity faster the longer you use them? An international research team from The University of Texas at Austin set out to examine this familiar issue, known as battery degradation, by focusing on the earbuds that many people rely on daily. Through a series of x-ray, infrared, and other imaging approaches, the researchers investigated the hidden complexities behind these tiny devices and revealed why their battery life declines over time.

“This started with my personal headphones; I only wear the right one, and I found that after two years, the left earbud had a much longer battery life,” said Yijin Liu, an associate professor in the Cockrell School of Engineering’s Walker Department of Mechanical Engineering, who led the new research published in Advanced Materials. “So, we decided to look into it and see what we could find.”

Their analysis showed that crucial earbud features – like the Bluetooth antenna, microphones, and circuits – compete with the battery in a very confined space, producing a microenvironment that is less than ideal. This situation results in a temperature gradient that damages the battery over time, with different sections of the cell experiencing variable temperatures.

Real-world factors also complicate matters. Frequent changes in climate, shifts in air quality, and a host of other environmental variables challenge the battery’s resilience. While cells are generally designed to endure harsh conditions, constant fluctuations can take their toll.

These discoveries highlight the importance of considering how batteries interact with devices such as phones, laptops, and even electric vehicles. Packaging solutions, strategic design decisions, and adaptations for user habits may all play a role in extending battery performance.

“Using devices differently changes how the battery behaves and performs,” said Guannan Qian, the first author of this paper and a postdoctoral researcher in Liu’s lab. “They could be exposed to different temperatures; one person has different charging habits than another; and every electric vehicle owner has their own driving style. This all matters.”

In conducting this study, Liu and his team worked closely with UT’s Fire Research Group, led by mechanical engineer Ofodike Ezekoye. They paired infrared imaging methods with their in-house x-ray technology at UT Austin and Sigray Inc. To expand their scope, they then teamed up with some of the world’s most advanced x-ray facilities.

Their collaborators included researchers from SLAC National Accelerator Laboratory’s Stanford Synchrotron Radiation Lightsource, Brookhaven National Laboratory’s National Synchrotron Light Source II, Argonne National Laboratory’s Advanced Photon Source, and the European Synchrotron Radiation Facility (ESRF) in France. These partnerships allowed them to observe battery behavior under more authentic operating conditions.

“Most of the time, in the lab, we’re looking at either pristine and stable conditions or extremes,” said Xiaojing Huang, a physicist at Brookhaven National Laboratory. “As we discover and develop new types of batteries, we must understand the differences between lab conditions and the unpredictability of the real world and react accordingly. X-ray imaging can offer valuable insights for this.”

Looking ahead, Liu says his team will continue analyzing battery performance in the settings people experience every day. They plan to expand their approach to larger batteries, such as those in smartphones, laptops, and electric vehicles, to learn more about their degradation patterns.

Research Report:In-device Battery Failure Analysis

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Solar Energy

Quantum factors elevate plant energy transport efficiency

Published

1 day ago

February 5, 2025

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Quantum factors elevate plant energy transport efficiency

by Robert Schreiber

Munich, Germany (SPX) Feb 05, 2025

For countless engineers, converting sunlight into easily stored chemical energy stands as an enduring goal. Yet nature perfected this challenge billions of years ago. A recent study reveals that quantum mechanics, once thought to be limited to physics, is also essential for key biological processes.

Green plants and other photosynthetic organisms draw on quantum mechanical mechanisms to capture the sun’s energy. According to Prof. Jurgen Hauer: “When light is absorbed in a leaf, for example, the electronic excitation energy is distributed over several states of each excited chlorophyll molecule; this is called a superposition of excited states. It is the first stage of an almost loss-free energy transfer within and between the molecules and makes the efficient onward transport of solar energy possible. Quantum mechanics is therefore central to understanding the first steps of energy transfer and charge separation.”

Classical physics alone cannot completely describe how this phenomenon unfolds throughout green plants and in certain photosynthetic bacteria. Although the exact details remain only partly understood, Prof. Hauer and first author Erika Keil consider their new findings an important step toward uncovering how chlorophyll, the pigment behind leaf coloration, functions. Applying these insights to engineered photosynthesis devices could unlock unprecedented solar energy conversion efficiencies for both power production and photochemical applications.

In their investigation, the researchers focused on two portions of the light spectrum absorbed by chlorophyll: the low-energy Q band (yellow to red) and the high-energy B band (blue to green). In the Q region, two electronic states are quantum mechanically coupled, promoting virtually loss-free energy movement. The system subsequently relaxes via “cooling”, i.e. by releasing energy in the form of heat. These observations demonstrate that quantum mechanical processes can play a major role in shaping key biological functions.

Research Report:Reassessing the role and lifetime of Qx in the energy transfer dynamics of chlorophyll a

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Solar Energy

HZB sets new efficiency record for CIGS perovskite tandem solar cells

Published

2 days ago

February 5, 2025

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HZB sets new efficiency record for CIGS perovskite tandem solar cells

by Robert Schreiber

Berlin, Germany (SPX) Feb 05, 2025

Researchers at Helmholtz Center Berlin for Materials and Energy (HZB) and Humboldt University Berlin have developed a CIGS-perovskite tandem solar cell that has set a new world record for efficiency, achieving 24.6%. The performance of the cell has been officially certified by the Fraunhofer Institute for Solar Energy Systems.

Thin-film solar cells, such as those based on copper, indium, gallium, and selenium (CIGS), require minimal material and energy to manufacture, making them an environmentally friendly alternative to conventional silicon-based solar cells. CIGS thin films can also be applied to flexible substrates, expanding their potential applications.

The new tandem solar cell developed by HZB and Humboldt University combines a CIGS bottom cell with a perovskite top cell. By optimizing the contact layers between these two components, the research team successfully increased efficiency to a record-breaking 24.6%. This milestone was confirmed by the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg, Germany.

This achievement was made possible through a collaborative effort among researchers. The top cell was developed by Thede Mehlhop, a master’s student at TU Berlin, under the supervision of Stefan Gall. The perovskite absorber layer was created in the joint laboratory of HZB and Humboldt University Berlin, while the CIGS sub-cell and contact layers were fabricated by HZB researcher Guillermo Farias Basulto. Additionally, the KOALA high-performance cluster system at HZB was used to deposit the perovskite and contact layers in a vacuum.

“At HZB, we have highly specialized laboratories and experts who are top performers in their fields. With this world record tandem cell, they have once again shown how fruitfully they work together,” said Prof. Rutger Schlatmann, spokesman for the Solar Energy Department at HZB.

HZB has a strong track record in achieving world records in solar cell efficiency, including past accomplishments in silicon-perovskite tandem cells and now in CIGS-perovskite tandem technology.

“We are confident that CIGS-perovskite tandem cells can achieve much higher efficiencies, probably more than 30%,” said Prof. Rutger Schlatmann.