GT/ Progress in alternative battery technology
Energy & green technology biweekly vol.48, 18th April — 2nd May
TL;DR
- It is not easy to make batteries cheap, efficient, durable, safe and environmentally friendly at the same time. Researchers have now succeeded in uniting all of these characteristics in zinc metal batteries.
- Ensuring the supply of food to the constantly growing world population and protecting the environment at the same time are often conflicting objectives. Now researchers have successfully developed a method for the synthetic manufacture of a nutritional protein using a type of artificial photosynthesis. The animal feed industry is the primary driver of high demand for large volumes of this nutritional protein L-alanine, which is also suitable for use in meat substitute products.
- Perovskite solar cells (PSCs) are considered a promising candidate for next-generation photovoltaic technology with high efficiency and low production cost, potentially revolutionizing the renewable energy industry. However, the existing layer-by-layer manufacturing process presents challenges that have hindered the commercialization of this technology. Recently, researchers have developed an innovative one-step solution-coating approach that simplifies the manufacturing process and lowers the commercialization barriers for PSCs.
- Researchers have created environmentally-friendly, high-efficiency photovoltaic cells that harness ambient light to power internet of Things (IoT) devices.
- Organic solar cells have a photoactive layer that is made from polymers and small molecules. The cells are very thin, can be flexible, and are easy to make. However, the efficiency of these cells is still much below that of conventional silicon-based ones. Applied physicists have now fabricated an organic solar cell with an efficiency of over 17 percent, which is in the top range for this type of material. It has the advantage of using an unusual device structure that is produced using a scalable technique.
- Researchers have developed a new mining technique which uses microbes to recover metals and store carbon in the waste produced by mining. Adopting this technique of reusing mining waste, called tailings, could transform the mining industry and create a greener and more sustainable future.
- Polymer chemists have been finding ways to tackle the environmental problems humans have created with plastics waste. Now, a team has come up with fundamental new chemistry that seeds a creative solution to the challenge of recycling mixed-use plastics.
- Global experts on solar power strongly urge a commitment to the continued growth of photovoltaic (PV) manufacturing and deployment to power the planet, arguing that lowballing projections for PV growth while waiting for a consensus on other energy pathways or the emergence of technological last-minute miracles ‘is no longer an option.’
- Scientists have now revealed an important reason why organic solar cells rapidly degrade under operation. This new insight will drive the design of more stale materials for organic semiconductor-based photovoltaics, thus enabling cheap and renewable electricity generation.
- Researchers have developed a chemical process that can disassemble the epoxy composite of wind turbine blades and simultaneously extract intact glass fibers as well as one of the epoxy resin’s original building blocks in a high quality. The recovered materials could potentially be used in the production of new blades.
- And more!
Green Technology Market
Green technology is an applicable combination of advanced tools and solutions to conserve natural resources and environment, minimize or mitigate negative impacts from human activities on the environment, and ensure sustainability development. Green technology is also referred to as clean technology or environmental technology which includes technologies, such as IoT, AI, analytics, blockchain, digital twin, security, and cloud, which collect, integrate, and analyze data from various real-time data sources, such as sensors, cameras, and Global Positioning System (GPS).
Green technology, also known as sustainable technology, protects the environment by using various forms of sustainable energy. Some of the best examples of green technologies include solar panels, LED lighting, wind energy, electric vehicles, vertical farming, and composting.
The global Green Technology and Sustainability market size to grow from USD 11.2 billion in 2020 to USD 36.6 billion by 2025, at a Compound Annual Growth Rate (CAGR) of 26.6% during the forecast period. The growing consumer and industrial interest for the use of clean energy resources to conserve environment and increasing use of Radio Frequency Identification sensors across industries are driving the adoption of green technology and sustainability solutions and services in the market.
The blockchain segment is estimated to grow at the highest CAGR: Energy-intensive cryptocurrency mining has caused a spike in carbon emission, and hence blockchain is capable of driving innovation in the field of green technology.
Latest Research
Creating water-in-salt-like environment using coordinating anions in non-concentrated aqueous electrolytes for efficient Zn batteries
by Dario Gomez Vazquez, Travis P. Pollard, Julian Mars, Ji Mun Yoo, Hans-Georg Steinrück, Sharon E. Bone, Olga V. Safonova, Michael F. Toney, Oleg Borodin, Maria R. Lukatskaya in Energy & Environmental Science
The world needs cheap and powerful batteries that can store sustainably produced electricity from wind or sunlight so that we can use it whenever we need it, even when it’s dark outside or there’s no wind blowing. Most common batteries that power our smartphones and electric cars are lithium-ion batteries. These are quite expensive because worldwide demand for lithium is soaring, and these batteries are also highly flammable.
Water-based Zinc batteries offer a promising alternative to these lithium-ion batteries. An international team of researchers led by ETH Zurich has now devised a strategy that brings key advances to the development of such zinc batteries, making them more powerful, safer and more environmentally friendly.
There is a number of advantages to Zinc batteries: Zinc is abundant, cheap and has mature recycling infrastructure. Furthermore, zinc batteries can store a lot of electricity. Most importantly, zinc batteries don’t necessarily require the use of highly flammable organic solvents as the electrolyte fluid, as they can also be made using water-based electrolytes instead.
If only there weren’t challenges that engineers must face with when developing these batteries: when zinc batteries are charged at high voltage, the water in electrolyte fluid reacts on one of the electrodes to form hydrogen gas. When this happens, the electrolyte fluid dwindles and battery performance decreases. Furthermore, this reaction causes excess pressure to build up in the battery that can be dangerous. Another issue is formation of spikey deposits of Zinc during charging of the battery, known as dendrites, that can pierce through the battery and in the worst case even cause short circuit and render the battery unusable.
In recent years, engineers have pursued the strategy of enriching the aqueous liquid electrolyte with salts in order to keep the water content as low as possible. But there are also disadvantages to this: It makes the electrolyte fluid viscous, which slows down the charging and discharging processes considerably. In addition, many of the salts used contain fluorine, making them toxic and harmful to the environment. Maria Lukatskaya, Professor of Electrochemical Energy Systems at ETH Zurich, has now joined forces with colleagues from several research institutions in the United States and Switzerland to systematically search for the ideal salt concentration for water-based zinc-ion batteries. Using experiments supported by computer simulations, the researchers were able to reveal that the ideal salt concentration is not, as was previously assumed, the highest one possible, but a relatively low one: five to ten water molecules per salt’s positive ion.
What’s more, the researchers didn’t use any environmentally harmful salts for their improvements, opting instead for environmentally friendly salts of acetic acid, called acetates.
“With an ideal concentration of acetates, we were able to minimise electrolyte depletion and prevent Zinc dendrites just as well as other scientists previously did with high concentrations of toxic salts,” says Dario Gomez Vazquez, a doctoral student in Lukatskaya’s group and lead author of the study. “Moreover, with our approach, the batteries can be charged and discharged much faster.”
So far, the ETH researchers have tested their new battery strategy on a relatively small laboratory scale. The next step will be to scale up the approach and see if it can also be translated for large batteries. Ideally, these might one day be used as storage units in the power grid to compensate for fluctuations, say, or in the basements of single-family homes to allow solar power produced during the day to be used in the evening.
There are still some challenges to overcome before zinc batteries will be ready for the market, as ETH Professor Lukatskaya explains: batteries consist of two electrodes — the anode and the cathode — and the electrolyte fluid between them.
“We showed that by tuning electrolyte composition efficient charging of Zinc anodes can be enabled,” she says. “Going forward, however, performance cathode materials will have to be optimised as well to realize durable and efficient zinc batteries.”
Cell-free enzymatic L-alanine synthesis from green methanol
by Vivian Pascal Willers, Manuel Döring, Barbara Beer, Volker Sieber in Chem Catalysis
Ensuring the supply of food to the constantly growing world population and protecting the environment at the same time are often conflicting objectives. Now researchers at the Technical University of Munich (TUM) have successfully developed a method for the synthetic manufacture of nutritional protein using a type of artificial photosynthesis. The animal feed industry is the primary driver of high demand for large volumes of nutritional protein, which is also suitable for use in meat substitute products.
A group led by Prof. Volker Sieber at the TUM Campus Straubing for Biotechnology and Sustainability (TUMCS) has succeeded in producing the amino acid L-alanine, an essential building block in proteins, from the environmentally harmful gas CO2. Their indirect biotechnological process involves methanol as an intermediate. Until now, protein for animal feed has been typically produced in the southern hemisphere with large-scale agricultural space requirements and negative consequences for biodiversity.
The CO2, which is removed from the atmosphere, is first turned into methanol using green electricity and hydrogen. The new method converts this intermediate into L-alanine in a multi-stage process using synthetic enzymes; the method is extremely effective and generates very high yields. L-alanine is one of the most important components of protein, which is essential to the nutrition of both humans and animals.
Prof. Sieber, of the TUM Professorship for Chemistry of Biogenic Resources, explains: “Compared to growing plants, this method requires far less space to create the same amount of L-alanine, when the energy used comes from solar or wind power sources. The more efficient use of space means a kind of artificial photosynthesis can be used to produce the same amount of foodstuffs on significantly fewer acres. This paves the way for a smaller ecological footprint in agriculture.”
The manufacture of L-alanine is only the first step for the scientists. “We also want to produce other amino acids from CO2 using renewable energy and to further increase efficiency in the realization process,” says co-author Vivian Willers, who developed the process as a doctoral candidate at the TUM Campus Straubing. The researchers add that the project is a good example of how bioeconomy and hydrogen economy in combination can make it possible to achieve more sustainability.
Co-deposition of hole-selective contact and absorber for improving the processability of perovskite solar cells
by Xiaopeng Zheng, Zhen Li, Yi Zhang, Min Chen, et al in Nature Energy
Perovskite solar cells (PSCs) are considered a promising candidate for next-generation photovoltaic technology with high efficiency and low production cost, potentially revolutionizing the renewable energy industry. However, the existing layer-by-layer manufacturing process presents challenges that have hindered the commercialisation of this technology. Recently, researchers from City University of Hong Kong (CityU) and the National Renewable Energy Laboratory (NREL) in the US jointly developed an innovative one-step solution-coating approach that simplifies the manufacturing process and lowers the commercialisation barriers for PSCs.
“Reducing the number of device-processing steps without sacrificing device efficiency will help reduce the process complexity and manufacturing cost, which will enhance the manufacturability of PSCs,” explained Dr Zhu Zonglong, a co-leader of the research and an assistant professor in the Department of Chemistry at CityU.
“We addressed the manufacturing issue with a novel approach to co-process the hole-selective contact and perovskite layer in a single step, resulting in state-of-the-art efficiency of 24.5% and exceptional stability for inverted perovskite solar cells. This helps bring the commercialisation of the technology one step closer,” he said.
Typically, PSCs are fabricated using a layer-by-layer process, which involves sequentially depositing different layers of the solar cell on top of each other. While this approach has been successful in producing high-performance perovskite solar cells, it causes issues that may hinder their commercialisation, such as increased fabrication cost, unsatisfactory uniformity and reproducibility.
To improve the manufacturability of PSCs, Dr Zhu collaborated with Dr Joseph M. Luther, from NREL, to jointly invent a new approach for fabricating efficient inverted perovskite solar cells in which the hole-selective contact and perovskite light absorber can spontaneously form in a single solution-coating procedure.
They found that if specific phosphonic or carboxylic acids are added to perovskite precursor solutions, the solution will self-assemble on the indium tin oxide substrate during perovskite film processing. They form a robust self-assembled monolayer as an excellent hole-selective contact while the perovskite crystallizes. This single solution-coating procedure not only solves wettability issues, but also simplifies device fabrication by creating both the hole-selective contact and the perovskite light absorber simultaneously, instead of the traditional layer-by-layer process.
The newly created PSC device has a power conversion efficiency of 24.5% and can retain more than 90% of its initial efficiency even after 1,200 hours of operating at the maximum power point under continuous illumination. Its efficiency is comparable to that of similar PSCs in the market.
The collaborative team also showed that the new approach is compatible with various self-assembled monolayer molecular systems, perovskite compositions, solvents and scalable processing methods, such as spin-coating and blade-coating techniques. And the PSC fabricated with the new approach have comparable performance with those produced from other methods.
“By introducing this innovative approach, we hope to contribute to the perovskite research community by proposing a more straightforward method for manufacturing high-performance perovskite solar cells and potentially accelerating the process of bring them to market,” said Dr Zhu.
The research team plans to further explore the relationship between self-assembled monolayer molecule structures and perovskite precursors to identify an optimal group of self-assembled monolayer molecules for this technique, thereby enhancing the overall performance of the PSCs.
Emerging indoor photovoltaics for self-powered and self-aware IoT towards sustainable energy management
by Hannes Michaels, Michael Rinderle, Iacopo Benesperi, Richard Freitag, Alessio Gagliardi, Marina Freitag in Chemical Science
Newcastle University researchers have created environmentally-friendly, high-efficiency photovoltaic cells that harness ambient light to power internet of Things (IoT) devices.
Led by Dr Marina Freitag, the research group from the from School of Natural and Environmental Sciences (SNES) created dye-sensitized photovoltaic cells based on a copper(II/I) electrolyte, achieving an unprecedented power conversion efficiency of 38% and 1.0V open-circuit voltage at 1,000 lux (fluorescent lamp). The cells are non-toxic and environmentally friendly, setting a new standard for sustainable energy sources in ambient environments.
The research has the potential to revolutionise the way IoT devices are powered, making them more sustainable and efficient, and opening up new opportunities in industries such as healthcare, manufacturing, and smart city development.
Dr Marina Freitag, Principal Investigator at SNES, Newcastle University, said: “Our research marks an important step towards making IoT devices more sustainable and energy-efficient. By combining innovative photovoltaic cells with intelligent energy management techniques, we are paving the way for a multitude of new device implementations that will have far-reaching applications in various industries.”
The team also introduced a pioneering energy management technique, employing long short-term memory (LSTM) artificial neural networks to predict changing deployment environments and adapt the computational load of IoT sensors accordingly. This dynamic energy management system enables the energy-harvesting circuit to operate at optimal efficiency, minimizing power losses or brownouts.
This breakthrough study demonstrates how the synergy of artificial intelligence and ambient light as a power source can enable the next generation of IoT devices. The energy-efficient IoT sensors, powered by high-efficiency ambient photovoltaic cells, can dynamically adapt their energy usage based on LSTM predictions, resulting in significant energy savings and reduced network communication requirements.
Outstanding Fill Factor in Inverted Organic Solar Cells with SnO 2 by Atomic Layer Deposition
by Lorenzo Di Mario, David Garcia Romero, Han Wang, Eelco K. Tekelenburg, Sander Meems, Teodor Zaharia, Giuseppe Portale, Maria A. Loi in Advanced Materials
Organic solar cells have a photoactive layer that is made from polymers and small molecules. The cells are very thin, can be flexible, and are easy to make. However, the efficiency of these cells is still much below that of conventional silicon-based ones. Applied physicists from the University of Groningen have now fabricated an organic solar cell with an efficiency of over 17 percent, which is in the top range for this type of material. It has the advantage of using an unusual device structure that is produced using a scalable technique. The design involves a conductive layer of tin oxide that is grown by atomic layer deposition. The scientists also have several ideas to further improve the efficiency and stability of the cell.
In organic solar cells, polymers and small molecules convert light into charges that are collected at the electrodes. These cells are made as thin films of different layers — each with its own properties — that are stacked onto a substrate. Most important is the photoactive layer, which converts light into charges and separates the electrons from the holes, and the transport and blocking layer, which selectively directs the electrons towards the electrode.
‘In most organic solar cells, the electron transport layer is made of zinc oxide, a highly transparent and conductive material that lays below the active layer,’ says David Garcia Romero, a PhD student in the Photophysics and Optoelectronics group at the Zernike Institute for Advanced Materials at the University of Groningen, led by Professor Maria Antonietta Loi. Garcia Romero and Lorenzo Di Mario, a postdoctoral researcher in the same group, worked on the idea of using tin oxide as the transport layer. ‘Zinc oxide is more photoreactive than tin oxide and, therefore, the latter should lead to a higher device stability,’ he explains.
Although tin oxide had shown promising results in previous studies, the best way to grow it into a suitable transport layer for an organic solar cell had not yet been found.
‘We used atomic layer deposition, a technique that had not been used in the field of organic photovoltaics for a long time,’ says Garcia Romero. However, it has some important advantages: ‘This method can grow layers of exceptional quality and it is scalable to industrial processes, for example in roll-to-roll processing.
The organic solar cells that were made with tin oxide deposited by atomic layer deposition on top show a very good performance. ‘We achieved a champion efficiency of 17.26 percent,’ says Garcia Romero. The fill factor, an important parameter of solar cell quality, showed values up to 79 percent, in agreement with the record values for this type of structure. Furthermore, the optical and structural characteristics of the tin oxide layer could be tuned by varying the temperature at which the material is deposited. A maximum power conversion was reached in cells with a transport layer that was deposited at 140 degrees Celsius. This same result was demonstrated for two different active layers, meaning that the tin oxide improved efficiency in a generic way.
‘Our aim was to make organic solar cells more efficient and to use methods that are scalable,’ says Garcia Romero. The efficiency is close to the current record for organic solar cells, which stands around 19 percent. ‘And we haven’t optimized the other layers yet. So, we need to push our structure a bit further.’ Garcia Romero and his co-author Lorenzo di Mario are also keen to try making larger area cells. These are typically less efficient but are needed to step towards real-world applications and panels.
The new solar cell with an impressively high fill factor is a good starting point for further development. Garcia Romero: ‘It may be a bit early for industrial partners to take this on; we need to do some more research first. And we hope that our use of atomic layer deposition will inspire others in the field.’ ‘We always strive to understand what is happening in a material and in a device structure,’ adds Professor Loi. ‘Here, we think that there might be room for improvement. In that process, our tin oxide transport layer is a great initial step.’ This class of solar cells may make an important extra contribution to the energy transition because of their mechanical properties and their transparency.
‘We expect that they will be used in a totally different way than silicon panels,’ says Loi. ‘We need to think broader and out of the box at the moment.’
Microbially mediated carbon dioxide removal for sustainable mining
by Jenine McCutcheon, Ian M. Power in PLOS Biology
Researchers have developed a new mining technique which uses microbes to recover metals and store carbon in the waste produced by mining. Adopting this technique of reusing mining waste, called tailings, could transform the mining industry and create a greener and more sustainable future.
Tailings are a by-product of mining. They are the fine-grained waste materials left after extracting the target ore mineral, which are then stacked and stored. This method is called dry-stack tailing. Over time, mining practices have evolved and become more efficient. But the climate crisis and rising demand for critical minerals require the development of new ore removal and processing technologies.
Old tailings contain higher amounts of critical minerals that can be extracted with the help of microbes through a process called bioleaching. The microbes help break down the ore, releasing any valuable metals that weren’t fully recovered in an eco-friendly way that is much faster than natural biogeochemical weathering processes.
“We can take tailings that were produced in the past and recover more resources from those waste materials and, in doing so, also reduce the risk of residual metals entering into local waterways or groundwater,” said Dr. Jenine McCutcheon, an assistant professor in the Department of Earth and Environmental Sciences.
In addition to improving resource recovery, the microbes capture carbon dioxide from the air and store it within the mine tailings as new minerals. This process aids in offsetting some of the emissions released while the mine was active and helps stabilize the tailings. Microbial mineral carbonation could offset more than 30 per cent of a mine sites annual greenhouse gas emissions if applied to an entire mine. In addition, this microbial-driven technique gives value to historical mine tailings that are otherwise considered industrial waste.
“This technique makes better use of current and past mine sites,” McCutcheon said. “Rethinking how future mine sites are designed in order to integrate this process could result in mines that are carbon neutral from the get-go rather than thinking about carbon storage as an add-on at the end.
“This technology is a potential game-changer in the fight against climate change, and the mining industry has a unique opportunity to play a significant role in the future of green energy.”
McCutcheon further believes that the microbial-driven processes could help the industry move towards carbon-neutral or carbon-negative mining, but industry engagement is critical to move this technology towards large-scale deployment.
Dynamic crosslinking compatibilizes immiscible mixed plastics
by Ryan W. Clarke, Tobias Sandmeier, Kevin A. Franklin, Dominik Reich, Xiao Zhang, Nayan Vengallur, Tarak K. Patra, Robert J. Tannenbaum, Sabin Adhikari, Sanat K. Kumar, Tomislav Rovis, Eugene Y.-X. Chen in Nature
Plastics are everywhere in our daily lives, but not all plastics are created equal — far from it. Take, for instance, polyethylene terephthalate, a plastic used to make soda bottles and clothing fibers. Then there’s high-density polyethylene, from which shampoo bottles, milk jugs and cutting boards are derived. Don’t forget polystyrene for packaging, or low-density polyethylene, which gives us cling wrap and grocery bags.
All of these are plastics, which are the most widely used types of polymers — macromolecules made of repeating units of small molecules called monomers. Post-consumer plastics are almost always collected as a mixed stream of waste, and products are often manufactured from two or more types of plastics. The bad news is that these items, though all “plastics,” are chemically and physically incompatible, and there’s no good industrial method for reusing or re-processing them into other useful products. That’s why most of those “recyclables” you’re throwing into bins every week are going to a landfill. Even after careful sorting and separation into individual plastics, mechanical recycling usually yields inferior products, termed down-cycling.
Polymer chemists at Colorado State University have long been leaders in finding ways to tackle the environmental problems humans have created with plastics waste. Now, they’ve come up with fundamental new chemistry that seeds a creative solution to the challenge of recycling mixed-use plastics. Led by University Distinguished Professor Eugene Chen in the Department of Chemistry, and Tomislav Rovis and Sanat Kumar, professors at Columbia University (Rovis was formerly a faculty member at CSU), the team has devised a new chemical strategy that delivers specifically designed small molecules called universal dynamic crosslinkers into mixed plastic streams. These crosslinkers transform a former muck of unmixable materials into a viable new set of polymers, which can be turned into new, higher-value, re-processable materials, a process known as upcycling.
When heated and processed together with the dynamic crosslinkers added in small amounts, the mixed plastics are made compatible with each other through in-situ formation of a new material, called a multiblock copolymer. Kumar likened the block copolymers to soap molecules, which make water compatible with oily dirt molecules. “In a similar way, these new types of dynamically formed ‘soaps,’ i.e. the block copolymers, compatibilize mixed plastics and make them usable as a new kind of material with useful properties.” This new method of upcycling, which does not involve deconstructing or reconstructing any of the original polymers, introduces a potential solution for recapturing materials and energy endowed in post-consumer mixed plastics that typically end up in landfills.
The team designed their crosslinkers and tested them on a variety of plastics, including samples of mixed polyethylene Ziploc bags and polylactide cups without prior purification or removal of additives or dyes, which are typically present in post-consumer plastic products. They combined their experiments with modeling studies to verify that the crosslinkers induce the formation of new multiblock copolymers.
“The system is so efficient, it compatibilizes three different polymers into a single new material,” Rovis said.
The researchers posit that their new strategy could help achieve the ultimate goal of reusing mixed plastic waste over multiple use cycles, Chen said.
“A key barrier is cost; we are talking about millions of tons of plastic waste, and you have to consider how many of these dynamic crosslinkers you need, although we currently need only less than 5% of the weight of the plastics in our upcycling process. Like many fundamental discoveries made in history, practical obstacles exist at the very beginning, but we are very excited about future potential.”
Photovoltaics at multi-terawatt scale: Waiting is not an option
by Nancy M. Haegel, Pierre Verlinden, Marta Victoria, Pietro Altermatt, et al in Science
Global experts on solar power strongly urge a commitment to the continued growth of photovoltaic (PV) manufacturing and deployment to power the planet, arguing that lowballing projections for PV growth while waiting for a consensus on other energy pathways or the emergence of technological last-minute miracles “is no longer an option.”
The consensus reached by participants in the 3rd Terawatt Workshop last year follows increasingly large projections from multiple groups around the world on the need for large-scale PV to drive electrification and greenhouse gas reduction. The increasing acceptance of PV technology has prompted the experts to suggest that about 75 terawatts or more of globally deployed PV will be needed by 2050 to meet decarbonization goals.
The workshop, led by representatives from the National Renewable Energy Laboratory (NREL), the Fraunhofer Institute for Solar Energy in Germany, and the National Institute of Advanced Industrial Science and Technology in Japan, gathered leaders from around the world in PV, grid integration, analysis, and energy storage, from research institutions, academia, and industry. The first meeting, in 2016, addressed the challenge of reaching at least 3 terawatts by 2030.
The 2018 meeting moved the target even higher, to about 10 TW by 2030, and to three times that amount by 2050. The participants in that workshop also successfully predicted the global generation of electricity from PV would reach 1 TW within the next five years. That threshold was crossed last year.
“We have made great progress, but the targets will require continued work and acceleration,” said Nancy Haegel, director of the National Center for Photovoltaics at NREL. Haegel is lead author of the new article. The coauthors represent 41 institutions from 15 countries.
“Time is of the essence, so it’s important that we set ambitious and achievable goals that have significant impact,” said Martin Keller, director of NREL. “There has been so much progress in the realm of photovoltaic solar energy, and I know we can accomplish even more as we continue to innovate and act with urgency.”
Incident solar radiation can easily provide more than enough energy to meet the Earth’s energy needs, but only a small percentage is actually put to use. The amount of electricity supplied globally by PV significantly increased from a negligible amount in 2010 to 4–5% in 2022.
The report from the workshop noted the “window is increasingly closing to take action at scale to cut greenhouse gas emissions while meeting global energy needs for the future.” PV stands out as one of very few options that can be immediately used to replace fossil fuels. “A major risk for the next decade would be to make poor assumptions or mistakes in modeling the required growth in the PV industry, and then realize too late that we were wrong on the low side and need to ramp up manufacturing and deployment to unrealistic or unsustainable levels.”
Reaching the 75-terawatt target, the authors predicted, will place significant demands on both PV manufacturers and the scientific community. For example:
- Makers of silicon solar panels must reduce the amount of silver used in order for the technology to be sustainable at a multi-terawatt scale.
- The PV industry must continue to grow at a rate of about 25% per year over the next critical years.
- The industry must continuously innovate to improve material sustainability and reduce its environmental footprint.
Workshop participants also said solar technology must be redesigned for ecodesign and circularity, although recycling materials is not an economically viable solution at present for material demands given the relatively low installations to date compared to the demands of the next two decades. As the report noted, the target of 75 terawatts of installed PV “is both a major challenge and an available path forward. Recent history and the current trajectory suggest that it can be achieved.”
The critical role of the donor polymer in the stability of high-performance non-fullerene acceptor organic solar cells
by Yiwen Wang, Joel Luke, Alberto Privitera, Nicolas Rolland, Chiara Labanti, et al in Joule
Due to the recent improvements in the efficiency with which solar cells made from organic (carbon-based) semiconductors can convert sunlight into electricity, improving the long-term stability of these photovoltaic devices is becoming an increasingly important topic. Real-world applications of the technology demand that the efficiency of the photovoltaic device be maintained for many years. To address this key problem, researchers have studied the degradation mechanisms for the two components used in the light-absorbing layer of organic solar cells: the ‘electron donor’ and ‘electron acceptor’ materials. These two components are needed to split the bound electron-hole pair formed after the absorption of a photon into the free electrons and holes that constitute electrical current.
In this new study, an international team of researchers led by the Cavendish Laboratory, University of Cambridge, have for the first time considered the degradation pathways of both the electron donor and electron acceptor materials. The detailed investigation of the electron donor material sets the current research work apart from the previous studies and provides important new insights for the field. Specifically, the identification of an ultrafast deactivation process unique to the electron donor material has not been observed before and provides a new angle to consider material degradation in organic solar cells.
To understand how these materials degraded, the Cavendish researchers worked as part of an international team with scientists in the UK, Belgium, and Italy. Together, they combined photovoltaic device stability studies, where the operational solar cell is subject to intense light that closely matches sunlight, with ultrafast laser spectroscopy performed in Cambridge. Through this laser technique, they have been able to identify a new degradation mechanism in the electron donor material involving twisting in the polymer chain. As a result, when the twisted polymer absorbs a photon, it undergoes an extremely rapid deactivation pathway on femtosecond timescales (a millionth billionth of a second). This undesirable process is fast enough to outcompete the generation of free electrons and holes from a photon, which the scientists were able to correlate with the reduced efficiency of the organic solar cell after it had been exposed to simulated sunlight.
“It was interesting to find that something as seemingly minor as the twisting of a polymer chain could have such a large effect on the solar cell efficiency,” said Dr. Alex Gillett, the lead author of the paper. “In the future, we plan to build on our findings by collaborating with chemistry groups to design new electron donor materials with more rigid polymer backbones. We hope that this will reduce the propensity of the polymer to twist and thus improve the stability of the organic solar cell device.”
Due to their unique properties, organic solar cells can be used in a wide range of applications for which traditional silicon photovoltaics aren’t suitable. This could include electricity generating windows for greenhouses that transmit the colours of light required for photosynthesis, or even photovoltaics that could be rolled up for easy transportation and mobile electricity generation. Thus, by identifying the degradation mechanism that needs to be solved, the current research directly brings the next generation of photovoltaic materials and applications closer to reality.
Catalytic disconnection of C–O bonds in epoxy resins and composites
by Alexander Ahrens, Andreas Bonde, Hongwei Sun, Nina Kølln Wittig, Hans Christian D. Hammershøj, Gabriel Martins Ferreira Batista, Andreas Sommerfeldt, Simon Frølich, Henrik Birkedal, Troels Skrydstrup in Nature
The new chemical process is not limited to wind turbine blades but works on many different so-called fibre-reinforced epoxy composites, including some materials that are reinforced with especially costly carbon fibres.
Thus, the process can contribute to establishing a potential circular economy in the wind turbine, aerospace, automotive and space industries, where these reinforced composites, due to their light weight and long durability, are used for load-bearing structures.
Being designed to last, the durability of the blades poses an environmental challenge. Wind turbine blades mostly end up at waste landfills when they are decommissioned, because they are extremely difficult to break down. If no solution is found, we will have accumulated 43 million tonnes of wind turbine blade waste globally by 2050.
The newly discovered process is a proof-of-concept of a recycling strategy that can be applied to the vast majority of both existing wind turbine blades and those presently in production, as well as other epoxy-based materials. The results have filed a patent application for the process. Specifically, the researchers have shown that by using a ruthenium-based catalyst and the solvents isopropanol and toluene, they can separate the epoxy matrix and release one of the epoxy polymer’s original building blocks, bisphenol A (BPA), and fully intact glass fibres in a single process.
However, the method is not immediately scalable yet, as the catalytic system is not efficient enough for industrial implementation — and ruthenium is a rare and expensive metal. Therefore, the scientists from Aarhus University are continuing their work on improving this methodology.
“Nevertheless, we see it as a significant breakthrough for the development of durable technologies that can create a circular economy for epoxy-based materials. This is the first publication of a chemical process that can selectively disassemble an epoxy composite and isolate one of the most important building blocks of the epoxy polymer as well as the glass or carbon fibres without damaging the latter in the process,” says Troels Skrydstrup, one of the lead authors of the study.
