University of Surrey engineers’ innovative analysis of two-dimensional (2D) materials could boost the development of next-generation solar cells and LEDs.

Three-dimensional perovskites have proved themselves remarkably successful materials for LED devices and solar panels in the past decade. One key issue with these materials, however, is their stability, with device performance decreasing quicker than other state-of-the-art materials. The engineering community believes the 2D variant of perovskites could provide answers to these performance issues.

In a study published in The Journal of Physical Chemistry Letters, researchers from Surrey’s Advanced Technology Institute (ATI) detail how to improve the physical properties of 2D perovskite called Ruddlesden-Popper.

2D perovskites graphical image. Image Credit: University of Surrey Advanced Technology Institute. Click image for the largest view.

The study analyzed the effects of combining lead with tin inside the Ruddlesden-Popper structure to reduce the toxic lead quantity. This also allows for the tuning of key properties such as the wavelengths of light that the material can absorb or emit at the device level – improving the performance of photovoltaics and light-emitting diodes.

Cameron Underwood, lead author of the research and postdoctoral researcher at the ATI, said, “There is rightly much excitement about the potential of 2D perovskites, as they could inspire a sustainability revolution in many industries. We believe our analysis of strengthening the performance of perovskite can play a role in improving the stability of low-cost solar energy and LEDs.”

Professor Ravi Silva, corresponding author of the research and Director of the ATI, said, “As we wean ourselves away from fossil energy sources to more sustainable alternatives, we are starting to see innovative and ground-breaking uses of materials such as perovskites. The Advanced Technology Institute is dedicated to being a strong voice in shaping a greener and more sustainable future in electronics – and our new analysis is part of this continuing discussion.”

Perovskites have a big research effort underway worldwide. Perhaps this research is the key that unlocks some consumer products for the market. Holding down the lead level is a major improvement. If the longevity holds up and the manufacturing costs for 2D materials comes in low, we just might get another level of energy saving goods to market.

University of Warwick researchers propose densifying ceramics using flash sintering reducing energy use and may be used to improve the viability of manufacturing complex ceramic structures such as those required for solid state batteries by lowering the temperatures and shortening the duration of the heat treatment.

Flash sintering is a ceramic processing technique which uses electric current to intensively heat the ceramic sample internally rather than using only external furnace heating. The process can lower ceramic processing temperatures and durations significantly, enabling ceramics to be co-processed with metals or other materials, and reducing energy use.

However, the flash sintering process can result in low quality ceramics due to weaknesses caused by inhomogeneities in the microstructure.

Causes and Effects of thermal and microstructural gradients in flash sintered ceramics. Image Credit: WMG, University of Warwick. Click image for the largest view.

The origins of these inhomogeneities caused by thermal gradients in the material during flash sintering have been studied by researchers based at WMG, University of Warwick and academic and industrial collaborators. The procedures to mitigate the effects of these gradients are now outlined.

Adopting these modified flash sintering processes will enable the wider use of flash sintering in ceramic processing, enabling lower energy production of many useful ceramic products including solid-state batteries.

Densifying ceramics using flash sintering reduces energy use and may be used to improve the viability of manufacturing complex ceramic structures such as those required for solid state batteries by lowering the temperatures and shortening the duration of the heat treatment.

Working in collaboration with academic and industrial partners, researchers from WMG, University of Warwick have published a review of the state of the art of flash sintering focusing on the formation of inhomogeneous regions within the ceramics which currently limit the scale-up potential of flash sintering. The review finds that thermal gradients are responsible for microstructural inhomogeneities and suggests procedures to eliminate or reduce these effects.

The reduction of energy use in the ceramic manufacturing industry is a key step in meeting global emissions reduction targets, as conventional processes require long firing treatments at very high temperatures. Several low-energy processes have been developed over the past decade, with flash sintering emerging as a particularly promising route for densification of materials for use in applications including solid state batteries, thermal barrier coatings, and ceramic joints.

In the study paper, ‘Promoting microstructural homogeneity during flash sintering of ceramics through thermal management’ published as part of a special issue of the MRS Bulletin, Gareth Jones and Dr Claire Dancer from WMG, University of Warwick worked with collaborators from the University of Trento, Wuhan University of Technology, Normandie Université, and Lucideon Ltd to review the origins of microstructural variations in different regions of ceramic materials undergoing flash sintering.

Differences in microstructural development originate from thermal gradients within the material during processing, and these can be reduced by careful thermal management during the flash sintering process. These include:

· Altering the method for applying electrodes
· Improving thermal homogeneity through insulation
· Tailoring the frequency of the AC current
· Developing contactless methods for applying the electric current – which are currently limited to consolidation of thermal barrier coatings.

The findings of this review provide a roadmap for further research on thermal management in flash sintering, which will accelerate the development of the process for industrial implementation.

Dr Claire Dancer, leader of the Ceramics Group within the Materials and Sustainability Directorate at WMG, University of Warwick commented, “Lowering ceramic processing temperatures by using techniques such as flash sintering is an essential step for manufacturing complex multi-material structures such as those needed for solid-state batteries, and for lowering overall energy use in the ceramic industry. However, the process must produce robust homogenous ceramic materials to be of widespread use. Our paper explains why flash sintering can result in inhomogeneous properties in ceramics and suggests a number of routes to mitigate these effects.”

There are lots of applications where ceramics could be used but are not – due to cost. One can hope that industrialization of the new procedure suggestions get tested, adapted and put to work for better products.

 

A new research study from KU Leuven and VUB on sensitive geopolitical conflict around the Ethiopian mega-dam shows that several disagreements between Ethiopia, Sudan and Egypt around Africa’s largest hydropower plant, the new Grand Ethiopian Renaissance Dam (GERD), could be alleviated by massively expanding solar and wind power across the region.

Sebastian Sterl, energy planning expert at Vrije Universiteit Brussel (VUB) and KU Leuven in Belgium and lead author of the study, published in Nature Energy said, “Our results call for integrated hydro-solar-wind planning to be taken up in the GERD negotiations.”

The mega-dam is located in Ethiopia, near the border with Sudan. It is Africa’s largest hydropower plant. | © Google. Click image for the largest view.

For several years, political tensions between Egypt, Sudan and Ethiopia have been escalating in a conflict surrounding Africa’s largest hydropower plant: the nearly complete Grand Ethiopian Renaissance Dam (GERD) on the Blue Nile.

Ethiopia, which started filling GERD’s massive reservoir in 2020, says it needs GERD’s electricity to lift millions of its citizens out of poverty. But Egypt is deeply concerned by the mega-dam’s consequences for the Nile river, since its agriculture depends completely on Nile water -Egypt raised this issue to the UN Security Council earlier in 2020.

Sudan, meanwhile, appears caught between both sides. Ongoing African Union-led mediation talks to agree on long-term operation of the dam have so far yielded little fruit. Certain tongues have even invoked the looming threat of a “water war” between Cairo and Addis Ababa.

Sterl, an energy planning expert at VUB and KU Leuven and lead author of the study, explained, “The Blue Nile is a highly seasonal river. The GERD’s reservoir is so large that it can store the river’s full peak flow and deliver hydropower at a stable rate throughout the year, removing the flow seasonality. This makes a lot of sense from the Ethiopian perspective, but it overhauls the natural timing of the water reaching Sudan and Egypt. Behind many disagreements around GERD lies the question of who, if anyone, should be allowed to exert such control over the Nile river.

A group of researchers based in Belgium and Germany, led by Sterl, have now identified a surprising method that could solve multiple disagreements around the dam at once and benefit all three countries. The idea boils down to massively deploying modern, clean solar and wind power to serve as a complement to GERD’s hydropower. More concretely: the researchers propose that Ethiopia and its neighbors deploy large-scale solar and wind farms, work towards a regionally integrated power grid, and then agree on Ethiopia operating GERD in synergy with solar and wind power.

This would mean running less water through turbines on sunny and windy days, and more water during cloudy, windless spells and at nighttime, to “firm up” the always-fluctuating solar and wind power.

The researchers realized that sunshine and wind in many regions of Ethiopia, Sudan and their eastern African neighbors have opposite seasonal profiles to the Blue Nile flow. In these places, the sun shines brightest and the winds blow strongest during the dry season. This “seasonal synergy” between water, sun and wind lies at the heart of the researchers’ findings.

The study found that, if GERD were operated to back up solar and wind power throughout the year – both hourly and seasonally – this would automatically mean producing less hydropower during the dry season, and more during the wet season, without negatively affecting GERD’s yearly average power output. The water flowing out of the dam would then have a seasonality somewhat resembling the natural river flow, with a clear peak in the wet season.

According to Sterl, if GERD were operated in this way, “Essentially, Ethiopia would have all the expected benefits of a big dam – but for Sudan and Egypt, it would look as if the Ethiopians only built a modest, relatively small reservoir. There are many such reservoirs already on the Nile, so no country downstream of Ethiopia could really object to this.”

By reconciling parties around common energy and water objectives, the researchers identified at least five concrete benefits of such integrated hydro-solar-wind planning.

First, Ethiopia could become Africa’s largest power exporter while reducing its dependence on hydropower and lowering its electricity generation costs for the long term.

Second, consumption of polluting fossil fuels in Sudan and other eastern African countries could be displaced by solar and wind power, backed up by GERD.

Third, thanks to the proposed operation scheme of GERD, Egypt could receive more water during dry years than before and would not need to change the operation of its own High Aswan Dam.

Fourth, Ethiopia would make more efficient use of its mega-dam’s more than a dozen turbines by frequently producing at peak power whenever solar and wind would be unavailable.

And fifth, Nile river ecology across Sudan would be less affected by the new dam, as flow seasonality is an important component of rivers’ ecological sustainability.

According to the authors, the entire eastern African region stands to contribute. “Ethiopia could theoretically go alone, using GERD to back up its own solar and wind power,” said Sterl. “But it would work much better if, say, Sudan were to join in – it has better solar and wind resources than Ethiopia, allowing for better hydro-solar-wind synergies and reducing the overall costs of renewable power generation. Egypt has great solar and wind resources too, as do Djibouti, South Sudan and other eastern African countries. Regional cooperation in a common, Eastern African Power Pool could be key.”

The results of the study suggest that integrated hydro-solar-wind planning could be a highly interesting option to discuss in the ongoing GERD negotiations between Ethiopia, Sudan and Egypt. “You could call it a win-win situation,” said professor Wim Thiery, climate researcher at VUB and co-author of the study. “The entire region would benefit.”

The researchers obtained their results by using a dedicated, highly detailed computer model (REVUB) conceived to simulate the operation of hydropower dams alongside other renewables, like solar and wind power. The model was originally created by the same VUB-researchers in 2019 to study renewable electricity scenarios for West Africa. Later, as the GERD negotiations became more and more present in the media, the researchers realized they could directly apply the same tool to study solar and wind power as potential solutions to the GERD conflict.

This idea with the modeling done, looks to be very hopeful in reducing the conflict potential. The ‘jury’ is just getting the data, but the dam is closed and the downstream water flow interrupted. This might turn out to be too late, and that would be tragic. Huge power potential and a water reservoir kind of battery offers immense multinational economic potential.

Hopefully politics will move fast enough and finding the money will occur to avert a tragedy.

Gwangju Institute of Science and Technology (GIST) scientists have discovered a new catalyst material’s ability to significantly improve lithium-sulfur battery life, opening doors to their near-future practical commercial realization.

Cobalt Oxalate an electrochemical catalyst at the anode interface of a lithium-sulfur battery. Image Credit: Gwangju Institute of Science and Technology. Click image for the largest view.

Lithium-sulfur batteries, given their light weight and theoretical high capacities, are a promising alternative to conventional lithium-ion batteries for large-scale energy storage systems, drones, electric vehicles, etc. But at present, they suffer from poor battery life, limiting their applicability.

At the heart of most electronics today are rechargeable lithium-ion batteries (LIBs). But their energy storage capacities are not enough for large-scale energy storage systems (ESSs). Lithium-sulfur batteries (LSBs) could be useful in such a scenario due to their higher theoretical energy storage capacity. They could even replace LIBs in other applications like drones, given their light weight and lower cost.

But the same mechanism that is giving them all this power is keeping them becoming a widespread practical reality. Unlike LIBs, the reaction pathway in LSBs leads to an accumulation of solid lithium sulfide (Li2S6) and liquid lithium polysulfide (LiPS), causing a loss of active material from the sulfur cathode (positively charged electrode) and corrosion of the lithium anode (negatively charged electrode). To improve battery life, scientists have been looking for catalysts that can make this degradation efficiently reversible during use.

In a new study published in ChemSusChem, scientists from GIST, Korea, report their breakthrough in this endeavor. “While looking for a new electrocatalyst for the LSBs, we recalled a previous study we had performed with cobalt oxalate (CoC2O4) in which we had found that negatively charged ions can easily adsorb on this material’s surface during electrolysis. This motivated us to hypothesize that CoC2O4 would exhibit a similar behavior with sulfur in LSBs as well,” explained Prof. Jaeyoung Lee from GIST, who led the study.

To test their hypothesis, the scientists constructed an LSB by adding a layer of CoC2O4 on the sulfur cathode.

Sure enough, observations and analyses revealed that CoC2O4‘s ability to adsorb sulfur allowed the reduction and dissociation of Li2S6 and LiPS. Further, it suppressed the diffusion of LiPS into the electrolyte by adsorbing LiPS on its surface, preventing it from reaching the lithium anode and triggering a self-discharge reaction. These actions together improved sulfur utilization and reduced anode degradation, thereby enhancing the longevity, performance, and energy storage capacity of the battery.

Impressed by these findings, Prof. Lee envisions an electronic future governed by LSBs, which LIBs cannot realize. “LSBs can enable efficient electric transportation such as in unmanned aircrafts, electric buses, trucks and locomotives, in addition to large-scale energy storage devices,” he observes. “We hope that our findings can get LSBs one step closer to commercialization for these purposes.”

A higher capacity, lower weight, less expensive battery would certainly be very welcomed by consumers. It does seem that these scientists have gotten this battery chemistry a fresh start. While it is still very early in the lithium sulfur story, it now looks like the story is going to continue. With lithium at a high price, perhaps the economic incentive alone is enough to get more progress underway.

A Nanyang Technological University, Singapore (NTU Singapore) team of 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 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 directly via the end of the fiber cable.

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.

Design of the ‘smart’ device to harvest daylight. Image Credit: NTU Singapore. Click image for the largest view.

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 study paper has been published in the peer-reviewed scientific journal Solar Energy.

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.

Shifting of focused light spot under the ball, in accordance with sun’s position in the sky. Image Credit: NTU Singapore. Click image for the largest view.

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.

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.

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 fiber 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 fiber 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 fiber 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 fiber 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 fiber cable, will automatically light up. This ensures that the device can illuminate underground spaces throughout the day without interruption.

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 customize 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 specializing in lighting, and the industry collaborator of the research study said, “It is our privilege and honor to take this innovation journey with NTU. While we have the commercial and application knowledge, NTU in-depth know-how 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.

This is quite the interesting innovation! It looks and seems to be simple and economically feasible. Some design effort and commercial engineering could very well bring consumers a very useful and low cost to operate means to bring in more natural light.

This device will be welcome indeed, and doesn’t need a pitch black room to be very useful. Lets hope commercial development gets underway soon.


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