Solar Energy

Renewable energy sources: On the way towards large-scale thermal storage systems

Published

4 years ago

May 4, 2021

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Renewable energy sources: On the way towards large-scale thermal storage systems

High-temperature technologies enable electrothermal storage systems for large amounts of energy from renewable sources. Karlsruhe Institute of Technology (KIT), the German Aerospace Center (DLR), and the industry partner KSB have now launched the LIMELISA project to develop the necessary basis. Research is funded with EUR 3.8 million by the Federal Ministry for Economic Affairs and Energy.

Every year, wind parks and solar facilities in Germany produce thousands of gigawatt hours of power that cannot be used directly and therefore remain unused. At other times, lacking capacities are compensated by energy from fossil sources. Large-scale electrothermal storage systems may solve this problem and additionally enhance grid stability. The idea is to convert power into heat, to buffer this heat in comparably inexpensive storage systems, and to reconvert it into power, if necessary.

“When using media, such as salt melts and liquid metals, for storage and heat transfer, very high temperatures can be reached,” says Professor Thomas Wetzel, who conducts research at KIT’s Institute for Thermal Energy Technology and Safety (ITES) and Institute of Thermal Process Engineering. “This opens up new applications for thermal storage systems in industry and creates ecologically and economically sustainable options for the climate-friendly transformation of energy supply.”

Thermal storage systems are already used on the industrial scale. Concentrating solarthermal facilities store heat in salt melts. Steam power plants convert the heat into power. Under the LIMELISA (stands for Liquid Metal and Liquid Salt Heat Storage System) project, scientists of KIT support the development of next-generation thermal storage systems, which are specifically designed for the power-heat-power process.

Work concentrates on liquid metal technologies, whereas DLR focuses on salt melts. Research is coordinated and complemented by KSB, an internationally operating manufacturer of pumps and fittings that started to work with liquid-metal circuits in the 1960s.

Materials and Components for Highly Efficient Energy Storage Systems

Conventional electrothermal storage systems are operated on the basis of e.g. nitrate salt. Due to the materials and components (pumps, valves) used, however, they have only been operated at temperatures of up to 560C so far. “For reconversion of heat into power by conventional steam power plants, much higher temperatures are required,” says project head Dr. Klarissa Niedermeier, ITES.

“At KIT, we will test key components in a lead cycle of up to 700C.” Due to direct contact with the liquid metal, special materials are required, which are also developed and tested at KIT. At the Institute for Pulsed Power and Microwave Technology, Dr. Alfons Weisenburger studies these special steel mixtures. “Conventional corrosion protection methods are no longer sufficient at such temperatures,” he explains. “Among others, we use aluminum oxide as a type of shield to protect pumps and fittings.”

Various Applications in Industry

Thermal storage systems can be applied in many areas, including sector coupling. Apart from the power-heat-power process studied by LIMELISA, the technologies developed can also be used to supply heat networks with renewable power. Such technologies can efficiently supply the high-temperature process heat required by chemical or construction industries or for metal processing.

“Presently, this high-temperature heat demand is mainly met by fossil energy sources,” says Dr. Walter Tromm, Head of ITES. “High-temperature thermal storage systems would be an elegant option to use regenerative energy for key industrial processes and to solve the problem of volatile availability of regenerative energy sources.”

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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

1 day 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.