Solar Energy

Engineers apply physics-informed machine learning to solar cell production

Published

3 years ago

June 10, 2021

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Engineers apply physics-informed machine learning to solar cell production

Today, solar energy provides 2% of U.S. power. However, by 2050, renewables are predicted to be the most used energy source (surpassing petroleum and other liquids, natural gas, and coal) and solar will overtake wind as the leading source of renewable power. To reach that point, and to make solar power more affordable, solar technologies still require a number of breakthroughs. One is the ability to more efficiently transform photons of light from the Sun into useable energy.

Organic photovoltaics max out at 15% to 20% efficiency – substantial, but a limit on solar energy’s potential. Lehigh University engineer Ganesh Balasubramanian, like many others, wondered if there were ways to improve the design of solar cells to make them more efficient?

Balasubramanian, an associate professor of Mechanical Engineering and Mechanics, studies the basic physics of the materials at the heart of solar energy conversion – the organic polymers passing electrons from molecule to molecule so they can be stored and harnessed – as well as the manufacturing processes that produce commercial solar cells.

Using the Frontera supercomputer at the Texas Advanced Computing Center (TACC) – one of the most powerful on the planet – Balasubramanian and his graduate student Joydeep Munshi have been running molecular models of organic solar cell production processes, and designing a framework to determine the optimal engineering choices. They described the computational effort and associated findings in the May issue of IEEE Computing in Science and Engineering.

“When engineers make solar cells, they mix two organic molecules in a solvent and evaporate the solvent to create a mixture which helps with the exciton conversion and electron transport,” Balasubramanian said. “We mimicked how these cells are created, in particular the bulk heterojunction – the absorption layer of a solar cell. Basically, we’re trying to understand how structure changes correlate with the efficiency of the solar conversion?”

Balasubramanian uses what he calls ‘physics-informed machine learning’. His research combines coarse-grained simulation – using approximate molecular models that represent the organic materials – and machine learning. Balasubramanian believes the combination helps prevent artificial intelligence from coming up with unrealistic solutions.

“A lot of research uses machine learning on raw data,” Balasubramanian said. “But more and more, there’s an interest in using physics-educated machine learning. That’s where I think lies the most benefit. Machine learning per se is simply mathematics. There’s not a lot of real physics involved in it.”

Writing in Computational Materials Science in February 2021, Balasubramanian and Munshi along with Wei Chen (Northwestern University), and TeYu Chien (University of Wyoming) described results from a set of virtual experiments on Frontera testing the effects of various design changes. These included altering the proportion of donor and receptor molecules in the bulk heterojunctions, and the temperature and amount of time spent in annealing – a cooling and hardening process that contributes to the stability of the product.

They harnessed the data to train a class of machine learning algorithms known as support vector machines to identify parameters in the materials and production process that would generate the most energy conversion efficiency, while maintaining structural strength and stability. Coupling these methods together, Balasubramanian’s team was able to reduce the time required to reach an optimal process by 40%.

“At the end of the day, molecular dynamics is the physical engine. That’s what captures the fundamental physics,” he said. “Machine learning looks at numbers and patterns, and evolutionary algorithms facilitate the simulations.”

Trade-Offs and Limitations

Like many industrial processes, there are trade-offs involved in tweaking any facet of the manufacturing process. Faster cooling may help increase power efficiency, but it may make the material brittle and prone-to-break, for instance. Balasubramanian and his team employed a multi-objective optimization algorithm that balances the benefits and drawbacks of each change to derive the overall optimal manufacturing process.

“When you try to optimize one particular variable, you are looking at the problem linearly,” he said. “But most of these efforts have multi-pronged challenges that you’re trying to solve simultaneously. There are trade-offs that you need to make, and synergistic roles that you must capture, to come to the right design.”

Balasubramanian’s simulations matched experimental results. They determined that the make-up of the heterojunction and the annealing temperature/timing have the largest effects on overall efficiency. They also found what proportion of the materials in the heterojunction is best for efficiency.

“There are certain conditions identified in literature which people claim are the best conditions for efficiency for those select molecules and processing behavior,” he said. “Our simulation were able to validate those and show that other possible criteria would not give you the same performance. We were able to realize the truth, but from the virtual world.”

With an award of more time on Frontera in 2021-22, Balasubramanian will add further layers to the machine learning system to make it more robust. He plans to add experimental data, as well as other modalities of computer models, such as electronic structure calculations.

“Heterogeneity in the data will improve the results,” he said. “We plan to do first principle simulations of materials and then feed that data into the machine learning model, as well as data from coarse-grained simulations.”

Balasubramanian believes that current organic photovoltaics may be reaching the limits of their efficiency. “There’s a wall that’s hard to penetrate and that’s the material,” he said. “These molecules we’ve used can only go so far. The next thing to try is to use our framework with other molecules and advanced materials.”

His team mined the literature to understand the features that increase solar efficiency and then trained a machine learning model to identify potential new molecules with ideal charge transport behaviors. They published their research in the Journal of Chemical Information and Modeling. Future work on Frontera will use Balasubramanian’s framework to explore and computationally test these alternative materials, assuming they can be produced.

“Once established, we can take realistic molecules that are made in the lab and put them in the framework we’ve created,” he said. “If we discover new materials that perform well, it will reduce the cost of solar power generation devices and help Mother Earth.”

Balasubramanian’s research harnesses the two things that computer simulations are critical for, he says. “One is to understand the science that we cannot study with the tools that we have in the real world. And the other is to expedite the science – streamline what we really have to do, which reduces our cost and time to make things and physically test them.”

Research paper

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Solar Energy

Buck the Duck Curve: California’s Bold Leap Towards Solar Empowerment

Published

2 days ago

April 23, 2024

sarosh

Buck the Duck Curve: California’s Bold Leap Towards Solar Empowerment

by Bradley Bartz, President/Founder, ABC Solar

Los Angeles CA (SPX) Apr 23, 2024

In the sun-drenched state of California, solar power has been both a beacon of hope and a point of contention. At the heart of this debate lies the infamous “Solar Duck Curve”-a phenomenon critics have used to demonize the impact of solar power on the energy grid. This curve, which charts the mismatch between peak solar production and peak demand, has been portrayed as a nightmare for grid management. However, much like the visionary approach of Hong Kong’s free phone service in the past, California has the potential to transform this perceived problem into a profitable solution.

The Buck Load Initiative: A Call to Action

Governor Gavin Newsom has a golden opportunity to rewrite the narrative. Just as Hong Kong revolutionized communication by offering free phone service, making long distance calls economically accessible and turning a high-cost luxury into a distributed wealth generator, California can harness the currently curtailed solar power to fuel new economic frontiers.

Today, the reality is that the production of solar energy often exceeds demand during daylight hours, leading to what is known as ‘curtailment’. This means valuable, clean energy-energy that could power homes, businesses, and innovative technologies-is wasted. It’s akin to collecting rainwater in a drought-stricken land but pouring it down the drain just when it’s needed most.

Why The Buck Load?

The Buck Load is more than just a concept; it’s a directive for progress. This initiative proposes using surplus solar energy to power high-demand facilities and projects, such as high-speed wind tunnels for wildfire research or new industrial complexes, creating jobs and fostering innovation. It’s a win-win scenario where excess energy meets peak ingenuity, fostering a robust, sustainable economy.

Imagine this: instead of shutting down solar panels, we channel excess energy into research facilities, manufacturing plants, and even cryptocurrency mining operations-anywhere that can use high amounts of electricity outside of peak hours. We could turn every ray of sunshine into a thread in the fabric of a new economic miracle.

A Vision for the Future

As the President and Founder of ABC Solar, I’ve seen firsthand the capabilities and the limitations of our current energy practices. It’s time for a bold step forward. The Buck Load isn’t just about energy; it’s about setting a precedent for how we value and utilize our natural resources. It’s about ensuring that every Californian has the power they need, not just to survive, but to thrive.

Governor Newsom, the California Public Utilities Commission, and all stakeholders in our energy future are at a crossroads. We can continue down a path of restrictions and limitations, or we can choose a path of innovation and abundance. The Buck Load is the key to unlocking a future where California continues to lead the world in environmental consciousness and economic innovation.

Let us not be the Mr. Burns of our own narrative, shading the world from the potential of solar power. Let’s be the pioneers who used the sun to light up not just our homes, but our economy. Let’s make The Buck Load initiative a reality and show the world what California can do.

The time is now. Let’s not wait for tomorrow to solve the problems we can solve today. Let’s harness the full potential of the sun, and in doing so, fund our future-a future as bright as the California sun.

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Solar Energy

Efficient DC power converter enhances microgrid sustainability

Published

2 days ago

April 23, 2024

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Efficient DC power converter enhances microgrid sustainability

by Riko Seibo

Tokyo, Japan (SPX) Apr 22, 2024

A novel DC-DC power converter developed by Kobe University promises enhanced energy storage and conversion efficiency, marking a key step in advancing microgrid technologies. This new converter, designed to integrate seamlessly with various DC energy sources, improves system stability and simplicity with an unprecedented operational efficiency.

Electric power is classified into two types: AC (alternating current) and DC (direct current). Despite AC being the chosen standard for national power grids, the reliance on DC power by solar panels, batteries, electric vehicles, and computers necessitates a conversion, often with significant energy loss. The adoption of DC microgrids could mitigate this by directly linking renewable energy sources and storage units to consumers, eliminating the need for conversion and allowing for voltage flexibility essential for diverse applications.

Researchers from Kobe University and National Chung Hsing University, including MISHIMA Tomokazu and LAI Ching-Ming, have spearheaded the development of this technology. “Our interdisciplinary approach and advanced facilities have underpinned our success in developing a prototype that demonstrates significant advantages over existing systems,” explained LIU Shiqiang, a student team member at Kobe University.

The new design, featured in the journal IEEE Transactions on Power Electronics, optimizes voltage ratio and inductor current balance, improving performance for electric vehicle-centric applications. “The asymmetrical duty limit control is particularly beneficial for electric vehicle-connected DC microgrids,” Liu added.

The prototype’s effectiveness, showing efficiencies up to 98.3%, underscores its potential for real-world application and sets the stage for further enhancements and commercialization efforts by UPE-Japan, a startup emerging from Kobe University. “Our aim is to foster the shift towards more reliable and sustainable energy solutions, especially for electric vehicles and renewable energy systems,” Liu stated.

Research Report:Over 98% Efficiency SiC-MOSFET based Four-Phase Interleaved Bidirectional DC-DC Converter Featuring Wide-Range Voltage Ratio

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Solar Energy

‘Ancient Roman’ solar roof tiles power Pompeii villa

Published

3 days ago

April 22, 2024

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‘Ancient Roman’ solar roof tiles power Pompeii villa

By Ella IDE

Pompeii, Italy (AFP) April 19, 2024

Pompeii is shining a light on mysterious rites of ancient Rome thanks to terracotta-style solar roof tiles installed on one of its most famous villas.

The traditional-looking tiles have solar photovoltaic cells inside, allowing the UNESCO World Heritage Site to preserve its aesthetics while generating clean energy to illuminate its frescoes.

And though the project is in its early stages, experts say the tiles could one day help historic city centres across Italy turn green.

The tiles look “exactly the same as the ancient (Roman) ones”, found in archaeological sites and cities across the Mediterranean, Pompeii director Gabriel Zuchtriegel told AFP.

But while “Pompeii is a unique site due to its vast size and complexity … I hope this will not be a unique project,” said Zuchtriegel, who wants the site near Naples to be a “real-life lab for sustainability”.

The scheme weds emerging technologies with an extraordinary mural unearthed in 1909 under deep layers of volcanic ash at the Villa of the Mysteries, which was buried along with the rest of the city when Vesuvius erupted nearly 2,000 years ago.

The mural depicts female devotees of Dionysus — the god of wine and revelry — engaged in mysterious rites.

They have intrigued scholars for decades, with some historians suggesting they are evidence that the lady of the villa was a priestess whose slaves took part in cult rituals.

– Terracotta varnishes –

The fresco, which covers three walls and is one of the best preserved in Pompeii, is illuminated by special LED lights designed to bring the deep red, purple and gold images to life, while not damaging the painted surfaces.

The lights are powered by electricity generated by the solar panels, which were installed in October.

Ahlux, the Italian company behind the lights, patented the system in 2022 and produces both curved and flat panels varnished in terracotta tones.

The solar panels on the villa’s roof are flat and lie between traditional ceramic curved tiles.

They cover 70 square metres (750 square feet) of roof, produce a maximum of 13 kilowatt-hours and are linked to an ecologically-friendly sodium battery, according to project manager Alberto Bruni.

Pompeii, which gets over 15 hours sunlight a day in peak summer, intends to extend their use to other villas in the archaeological site, he said.

Augusto Grillo, the founder of Ahlux, said the tiles are about five percent less efficient than a traditional solar panel.

“This nominal loss is compensated however by the fact that our panels heat up less in summer,” while traditional ones are covered by glass, and can lose efficiency on very hot days, he said.

“The performance ends up being very similar,” he said.

– Red-tiled cities –

Various institutions have expressed interest in the tiles, from Rome’s MAXXI modern art museum to the 17th century Pinoteca Ambrosiana museum in Milan, Grillo said.

“The problem is finding the funds,” he said, adding that many of Italy’s famous historic buildings are public or owned by Catholic institutions.

The cost is a bit more than the price of a new roof and traditional panels put together — though the solar tiles, which last between 20 to 25 years, serve double duty, because they function as a roof too, Grillo said.

Project manager Bruni said the cost of the panels “is coming down”, meaning they may be able to play a part in the wider ecological transition.

Italy is under pressure to make red-roofed cities such as Florence or Bologna greener as part of efforts to combat climate change.

The European Union aims to reduce carbon emissions by 55 percent compared with 1990 levels by 2030, and will have to upgrade existing buildings to do so.

That is a mammoth challenge for Italy, where some 60 percent of buildings are in the worst two energy categories, compared to 17 percent in France and six percent in Germany, according to Italian Constructors’ Association ANCE.

“There needs to be some national and perhaps European co-investment to make sure that the very, very ambitious timelines have a chance of being respected,” Angelica Donati, president of the youth constructors’ association ANCE Giovani, told AFP.

“We have the most beautiful cities in the world, which means we need much more thoughtful interventions, and quickly. There’s a lot to be done”.

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