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NTU Singapore scientists design ‘smart’ device to harvest daylight



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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Research team achieves significant solar cell efficiency milestone




Research team achieves significant solar cell efficiency milestone

Research team achieves significant solar cell efficiency milestone

by Simon Mansfield

Sydney, Australia (SPX) May 26, 2024

A research team has created a tandem solar cell using antimony selenide as the bottom cell material and a hybrid perovskite material as the top cell, achieving over 20 percent power conversion efficiency. This advancement highlights antimony selenide’s potential for bottom cell applications.

Photovoltaic technology converts sunlight into electricity, offering a clean energy source. Scientists aim to enhance the efficiency of solar cells, achieving over 20 percent in conventional single-junction cells. Surpassing the Shockley-Queisser limit in these cells would be costly, but tandem solar cells can overcome this limit by stacking materials.

The team focused on antimony selenide for tandem cells, traditionally used in single-junction cells. “Antimony selenide is a suitable bottom cell material for tandem solar cells. However, because of the rarity of reported tandem solar cells using it as a bottom cell, little attention has been paid to its application. We assembled a tandem solar cell with high conversion efficiency using it as the bottom cell to demonstrate the potential of this material,” said Tao Chen, professor of Materials Science and Engineering at the University of Science and Technology of China.

Tandem cells absorb more sunlight than single-junction cells, converting more light into electricity. The team created perovskite/antimony selenide tandem cells with a transparent conducting electrode, optimizing the spectral response and achieving over 17 percent efficiency. By optimizing the antimony selenide bottom cell, they reached 7.58 percent efficiency.

The assembled four-terminal tandem cell achieved 20.58 percent efficiency, higher than independent subcells. The tandem cell is stable and uses nontoxic elements. “This work provides a new tandem device structure and demonstrates that antimony selenide is a promising absorber material for bottom cell applications in tandem solar cells,” said Chen.

The team aims to develop an integrated two-terminal tandem cell and further improve performance. “The high stability of antimony selenide provides great convenience for the preparation of two-terminal tandem solar cell, which means that it may have good results when paired with quite a few different types of top cell materials.”

Research Report:Sb2Se3 as a bottom cell material for efficient perovskite/Sb2Se3 tandem solar cells

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Flower or power? Campaigners fear lithium mine could kill rare plant




Flower or power? Campaigners fear lithium mine could kill rare plant

Flower or power? Campaigners fear lithium mine could kill rare plant


Rhyolite Ridge, United States (AFP) May 23, 2024

Delicate pink buds sway in the desert breeze, pregnant with yellow pompoms whose explosion will carpet the dusty corner of Nevada that is the only place on Earth where they exist.

Under their roots lie vast reserves of lithium, vital for the rechargeable electric car batteries that will reduce planet-heating pollution.

But campaigners fear the extraction of the precious metal could destroy the flower’s tiny habitat.

“This mine is going to cause extinction,” says Patrick Donnelly, an environmentalist who works at the Center for Biological Diversity, a non-governmental organization.

“They somehow claim that they’re not harming the (plant). But can you imagine if someone built an open-pit mine 200 feet from your house? Wouldn’t that affect your life profoundly?”

The plant in question is Tiehm’s buckwheat.

There are only around 20,000 known specimens, growing in a few very specific places on a total surface area equivalent to around five soccer fields.

In 2022, the wildflower was classified as endangered by US federal authorities, with mining cited as a major threat to its survival.

The plant and the lithium reserve on which it grows embody one of the key challenges and contradictions of the global climate struggle: how much damage can we inflict on the natural world as we seek to halt or reverse the problems we have already created?

– ‘Coexist’ –

Bernard Rowe, boss of Australian miner Ioneer, which holds the mineral rights to the area, says the lithium produced at Rhyolite Ridge “will be sufficient to provide batteries for about 370,000 vehicles” a year.

“We’ll do that year-on-year for 26 years,” he said.

Those nearly 10 million vehicles will go a long way towards meeting the goal President Joe Biden has set of cutting down the nation’s fleet of gas-guzzlers as a way to slash US production of planet-warming pollutants.

So-called zero-emission cars make up around 7.5 percent of new vehicle sales in the United States today — more than double the percentage just a few years earlier.

In California, the figure is more than 20 percent.

And while expansion in the sector has slowed, the category remains the fastest-growing, according to Kelley Blue Book.

And it’s not only in the United States: Global demand for lithium will increase five to seven times by 2030, according to the International Energy Agency.

The difficulty for US manufacturers is that much of the world’s lithium supply is dominated by strategic rival China, as well as Australia and Chile.

“The United States has very, very little domestic production,” said Rowe.

“So it’s important to develop a domestic supply chain to allow for that energy transition, and Rhyolite Ridge will be an integral part of that.”

Ioneer’s plans show that over the years the mine is in operation — it is projected to start producing lithium in late 2027 — around a fifth of the plant’s habitat will be directly affected.

But the company, which has spent $2.5 million researching the plant, says mining will not affect its survival; it is already growing well in greenhouses and biologists think it can be replanted.

“We’re very confident that the mine and Tiehm’s buckwheat can coexist,” Rowe said.

– ‘Greenwashing’ –

Donnelly counters that Ioneer is “basically greenwashing extinction.”

“They’re saying. ‘We’re going to save this plant,’ when actually they are going to send it to its doom,” he said.

Under the company’s plans, the strip mine will use hundreds of trucks, which Donnelly says will raise clouds of dust that will affect photosynthesis and harm the insects that pollinate the plants.

Ioneer says it has already planned mitigation methods, like dust curtains, and keeping the roads wet.

Still, Donnelly says, why not just move the mine? But Rowe counters that it’s not as simple as just digging somewhere else.

Ioneer has invested $170 million since 2016 to demonstrate the feasibility of this site, which it believes is one of the best around.

“Many of these other deposits haven’t had that amount of work, so they’re not viable alternatives to a project like this,” he said.

The US Department of Energy has offered Ioneer a $700 million loan for the project, if the Bureau of Land Management signs off on an operating permit.

Donnelly insists the issue is not just the future of one obscure wildflower, but rather just one example of large-scale biodiversity loss that is threatening millions of plants and animals.

“If we solve the climate crisis, but we drive everything extinct while we do it, we’re still going to lose our world,” he said.

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Tesla breaks ground on huge Shanghai battery plant




Tesla breaks ground on huge Shanghai battery plant

Tesla breaks ground on huge Shanghai battery plant

by AFP Staff Writers

Shanghai (AFP) May 23, 2024

Tesla broke ground on a massive battery factory in Shanghai on Thursday, Chinese state media reported, making it the US electric car giant’s second plant in the financial hub.

The project was announced last April after boss Elon Musk presented a vague but ambitious plan to investors to turbocharge growth.

However, the company last month reported a 55 percent drop in quarterly earnings, reflecting a decline in EV sales in an intensively competitive market.

The new Shanghai factory should make 10,000 units per year of Tesla’s Megapack batteries, state news agency Xinhua said.

Tesla says Megapacks are intended to store energy and stabilise supply for power grids, with each unit able to store more than three megawatt-hours of power.

The factory is expected to start mass production in 2025, state media said in May.

“I believe the new plant is a milestone for both Shanghai and Tesla,” the company’s vice president Tao Lin told Xinhua.

“In a more open environment, we can… supply the global market with large-scale energy-storage batteries manufactured in China.”

Musk has extensive business interests in China and is a fairly frequent visitor.

In April, he met Chinese Premier Li Qiang, and received a key security clearance for Tesla’s locally produced EVs.

Musk’s interests in China have long raised eyebrows in Washington — President Joe Biden has said in the past that his links to foreign countries were “worthy” of scrutiny.

The battery plant will be Tesla’s second in the Chinese city after its enormous Shanghai Gigafactory, which broke ground in 2019.

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