Solar Energy
The mystery of the missing energy solved in solar cells
The efficiency of solar cells can be increased by exploiting a phenomenon known as singlet fission. However, unexplained energy losses during the reaction have until now been a major problem. A research group led by scientists at Linkoping University, Sweden, has discovered what happens during singlet fission and where the lost energy goes. The results have been published in the journal Cell Reports Physical Science.
Solar energy is one of the most important fossil-free and eco-friendly sustainable sources of electricity. The silicon-based solar cells currently in use can at most use approximately 33% of the energy in sunlight and convert it to electricity. This is because the packets of light, or photons, in the sun’s beams have an energy that is either too low to be absorbed by the solar cell, or too high, so that part of the energy is dissipated to waste heat. This maximum theoretical efficiency is known as the Shockley-Queisser limit. In practice, the efficiency of modern solar cells is 20-25%.
However, a phenomenon in molecular photophysics known as singlet fission can allow photons with higher energy to be used and converted to electricity without heat loss. In recent years, singlet fission has attracted increasing attention from scientists, and intense activity is under way to develop the optimal material. However, unexplained energy losses during singlet fission have until now made it difficult to design such a material. Researchers have not been able to agree on the origin of these energy losses.
Now, researchers at Linkoping University, together with colleagues in Cambridge, Oxford, Donostia and Barcelona, have discovered where the energy goes during singlet fission.
“Singlet fission takes place in less than a nanosecond, and this makes it extremely difficult to measure. Our discovery allows us to open the black box and see where the energy goes during the reaction. In this way we will eventually be able to optimise the material to increase the efficiency of solar cells”, says Yuttapoom Puttisong, senior lecturer in the Department of Physics, Chemistry and Biology at Linkoping University.
Part of the energy disappears in the form of an intermediate bright state, and this is a problem that must be solved to achieve efficient singlet fission. The discovery of where the energy goes is a major step on the way to significantly higher solar cell efficiency – from the current 33% to over 40%.
The researchers used a refined magneto-optical transient method to identify the location of energy loss. This technique has unique advantages in that it can examine the ‘fingerprint’ of the singlet fission reaction at a nanosecond timescale. A monoclinic crystal of a polyene, diphenyl hexatriene (DPH), was used in this study.
However, this new technique can be used to study singlet fission in a broader material library. Yuqing Huang is a former doctoral student in the Department of Physics, Chemistry and Biology at Linkoping University, and first author of the article now published in a newly established journal, Cell Reports Physical Science:
“The actual singlet fission process takes place in the crystalline material. If we can optimise this material to retain as much as possible of the energy from the singlet fission, we will be significantly closer to application in practice. In addition, the singlet fission material is solution processable, which makes it cheap to manufacture and suitable for integration with existing solar cell technology”, says Yuqing Huang.
India mandates local-only solar energy components from 2026
by AFP Staff Writers
New Delhi (AFP) Dec 10, 2024
Indian clean energy companies will only be able to use solar modules built locally from June 2026, according to a government order apparently aimed at reducing Chinese imports.
Clean energy sector leaders in India, including ventures by conglomerates Reliance Enterprises and Tata Power, rely on Chinese vendors as their major suppliers.
As much as 70 percent of India’s solar power generation capacity is powered by Chinese equipment, according to industry estimates.
Indian companies are already required by law to use locally made solar panels in government projects.
The new rule mandates that only modules made from locally built photovoltaic cells, which convert light energy into electricity, can be used in projects with a bid deadline after Monday’s order.
“This condition will have to be followed irrespective of the date of commissioning,” said the order, issued by India’s renewable energy ministry.
The government is yet to issue the list of approved manufacturers of solar cells because “the installed capacity of solar cells in the country was lower than demand”.
But “with installed capacity of solar cells in the country expected to increase substantially in next year”, a list of approved manufacturers will now be released, the order said.
India’s solar equipment manufacturing space has made rapid strides in recent years.
A report by Bengaluru-based consulting firm Mercom India said the country’s solar panel production was expected to reach 95 gigawatts by the end of 2025.
India added 13.3 gigawatts of solar equipment manufacturing capacity in the first half of 2024, according to the same report.
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Stellantis, Chinese firm CATL plan $4bn battery plant in Spain
By Valentin Bontemps with Frederique Pris in Paris
Madrid (AFP) Dec 10, 2024
Car giant Stellantis and Chinese manufacturer CATL said Tuesday they would build a $4.3-billion factory to make electric vehicle batteries in Spain, the latest bid to boost Europe’s troubled EV drive.
They said they aim to start production by the end of 2026 at the site in the northern city of Zaragoza.
It “could reach up to 50 GWh capacity, subject to the evolution of the electrical market in Europe and continued support from authorities in Spain and the European Union”, the companies said in a statement.
The two firms signed an agreement in 2023 to produce battery parts for the manufacture of electric vehicles in Europe.
CATL, which has received robust financial support from Beijing, has launched two other European factories, in Germany and Hungary.
Its chief executive Robin Zeng met late on Monday with Spain’s Prime Minister Pedro Sanchez, ahead of the announcement of the 4.1-billion-euro deal.
In a message on X, the Socialist premier thanked the presidents of the two firms for their “firm commitment” to Spain, adding he was “very pleased”.
During a visit to China in September, Sanchez urged the European Union to “reconsider” a plan to impose tariffs on Chinese electric cars, calling for a “compromise” between the economic powerhouses.
Spanish Economy Minister Carlos Cuerpo called the announcement “excellent news for industry and employment in our country”.
Spain has been playing a growing role in European vehicle production, assembling 1.87 million cars in 2023 — the second-biggest producer in the continent after Germany, according to the European Automobile Manufacturers’ Association.
– Bumpy patch for carmakers –
The announcement comes at a turbulent time in the car industry as countries seek to switch to low-carbon electric vehicles to curb the climate crisis.
Sweden’s financially strained electric car battery maker Northvolt last month announced the resignation of its chief executive Peter Carlsson.
That came hours after the company sought bankruptcy protection in the United States.
The company said in September it was slashing 1,600 jobs — a quarter of its staff — and suspending the expansion of its site as it struggled with strained finances and a slowdown in demand.
The company had been seen as a cornerstone of European attempts to catch up with China and the United States in the production of battery cells, a crucial component of lower-emission cars.
Stellantis’s former chief executive Carlos Tavares also resigned on December 1, with the company signalling differences over how to save the group’s slumping profits.
Like other auto groups, Stellantis has blamed competition from China and the difficult transition to electric cars for much of its troubles.
It announced on November 26 that it was closing a factory at Luton in England with the loss of 1,100 jobs.
– ‘High-quality’ EVs –
Founded in 2011 in Ningde, eastern China, CATL produces more than a third of the electric vehicle batteries sold in the world.
Italian-US-French company Stellantis produces 14 brands including Fiat, Peugeot-Citroen, Opel, Maserati, Chrysler, Ram and Jeep.
The Zaragoza plant will make lithium iron phosphate (LFP) batteries, which are cheaper to produce but less powerful compared with nickel manganese cobalt (NMC) ones, the other current mainstream technology.
The companies said the factory, which will be designed to be completely carbon neutral, would enable Stellantis “to offer more high-quality, durable and affordable battery-electric passenger cars, crossovers and SUVs”.
Stellantis chairman John Elkann said in the statement that the venture “will bring innovative battery production to a manufacturing site that is already a leader in clean and renewable energy”.
Zeng said CATL’s goal was “to make zero-carbon technology accessible across the globe”.
The deal is expected to be closed in 2025, subject to regulation.
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Existing EV batteries may last significantly longer under real-world conditions
by Clarence Oxford
Los Angeles CA (SPX) Dec 10, 2024
Electric vehicle (EV) batteries subjected to typical real-world driving scenarios-such as heavy traffic, urban commutes, and long highway trips-could last up to 40% longer than previously projected, according to new research from the SLAC-Stanford Battery Center, a collaboration between Stanford University’s Precourt Institute for Energy and SLAC National Accelerator Laboratory. This finding suggests EV owners may delay the costly replacement of battery packs or the purchase of new vehicles for several more years than expected.
Traditionally, battery scientists have tested EV batteries in labs using a constant charge-discharge cycle. While effective for quick evaluations of new designs, this method does not accurately reflect the varied usage patterns of everyday drivers, the study published in *Nature Energy* on Dec. 9 reveals.
Although battery costs have fallen by approximately 90% over the past 15 years, they still represent about one-third of an EV’s price. This research could provide reassurance to current and prospective EV owners about the longevity of their vehicle’s batteries.
“We’ve not been testing EV batteries the right way,” said Simona Onori, the study’s senior author and an associate professor at Stanford’s Doerr School of Sustainability. “To our surprise, real driving with frequent acceleration, braking, stopping for errands, and extended rest periods helps batteries last longer than previously thought based on industry-standard tests.”
Real-World Driving Profiles Improve Battery Lifespan
The researchers developed four distinct EV discharge profiles, ranging from constant discharge to dynamic patterns based on actual driving data. Testing 92 commercial lithium-ion batteries over two years, they found that batteries subjected to realistic driving scenarios demonstrated significantly improved longevity.
Machine learning algorithms were crucial in analyzing the extensive data, revealing that certain driving behaviors, like sharp accelerations, slowed battery degradation. This contradicted prior assumptions that acceleration peaks harm EV batteries. “Pressing the pedal hard does not speed up aging. If anything, it slows it down,” explained Alexis Geslin, one of the study’s lead authors and a PhD candidate in materials science and computer science at Stanford.
Aging from Use vs. Time
The study differentiated between battery aging caused by charge-discharge cycles and aging from time alone. While frequent cycling dominates battery aging for commercial vehicles like buses or delivery vans, time-induced aging becomes a larger factor for personal EVs, which are often parked and idle.
“We battery engineers have assumed that cycle aging is much more important than time-induced aging,” said Geslin. “For consumers using their EVs for daily errands but leaving them unused most of the time, time becomes the predominant aging factor.”
The researchers identified an optimal discharge rate balancing both time and cycle aging for the batteries tested, which aligns with typical consumer driving habits. Manufacturers could update battery management software to incorporate these findings, potentially extending battery lifespan under normal conditions.
Implications for the Future
Evaluating new battery chemistries and designs under realistic conditions is critical for future advancements, said Le Xu, a postdoctoral scholar in energy science and engineering. “Researchers can now revisit presumed aging mechanisms at the chemistry, materials, and cell levels to deepen their understanding,” Xu added.
The study’s principles could apply beyond EV batteries to other energy storage systems, plastics, solar cells, and biomaterials where aging is a key concern. “This work highlights the power of integrating multiple areas of expertise-from materials science and modeling to machine learning-to drive innovation,” Onori concluded.
Research Report:Dynamic cycling enhances battery lifetime
Related Links
SLAC-Stanford Battery
Powering The World in the 21st Century at Energy-Daily.com
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