Solar Energy

So you want to build a solar or wind farm? Here’s how to decide where

Published

2 months ago

December 8, 2024

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So you want to build a solar or wind farm? Here’s how to decide where

by David L. Chandler | MIT News

Boston MA (SPX) Dec 08, 2024

Deciding where to build new solar or wind installations is often left up to individual developers or utilities, with limited overall coordination. But a new study shows that regional-level planning using fine-grained weather data, information about energy use, and energy system modeling can make a big difference in the design of such renewable power installations. This also leads to more efficient and economically viable operations.

The findings show the benefits of coordinating the siting of solar farms, wind farms, and storage systems, taking into account local and temporal variations in wind, sunlight, and energy demand to maximize the utilization of renewable resources. This approach can reduce the need for sizable investments in storage, and thus the total system cost, while maximizing availability of clean power when it’s needed, the researchers found.

The study, appearing in the journal Cell Reports Sustainability, was co-authored by Liying Qiu and Rahman Khorramfar, postdocs in MIT’s Department of Civil and Environmental Engineering, and professors Saurabh Amin and Michael Howland.

Qiu, the lead author, says that with the team’s new approach, “we can harness the resource complementarity, which means that renewable resources of different types, such as wind and solar, or different locations can compensate for each other in time and space. This potential for spatial complementarity to improve system design has not been emphasized and quantified in existing large-scale planning.”

Such complementarity will become ever more important as variable renewable energy sources account for a greater proportion of power entering the grid, she says. By coordinating the peaks and valleys of production and demand more smoothly, she says, “we are actually trying to use the natural variability itself to address the variability.”

Typically, in planning large-scale renewable energy installations, Qiu says, “some work on a country level, for example saying that 30 percent of energy should be wind and 20 percent solar. That’s very general.” For this study, the team looked at both weather data and energy system planning modeling on a scale of less than 10-kilometer (about 6-mile) resolution. “It’s a way of determining where should we, exactly, build each renewable energy plant, rather than just saying this city should have this many wind or solar farms,” she explains.

To compile their data and enable high-resolution planning, the researchers relied on a variety of sources that had not previously been integrated. They used high-resolution meteorological data from the National Renewable Energy Laboratory, which is publicly available at 2-kilometer resolution but rarely used in a planning model at such a fine scale. These data were combined with an energy system model they developed to optimize siting at a sub-10-kilometer resolution. To get a sense of how the fine-scale data and model made a difference in different regions, they focused on three U.S. regions – New England, Texas, and California – analyzing up to 138,271 possible siting locations simultaneously for a single region.

By comparing the results of siting based on a typical method vs. their high-resolution approach, the team showed that “resource complementarity really helps us reduce the system cost by aligning renewable power generation with demand,” which should translate directly to real-world decision-making, Qiu says. “If an individual developer wants to build a wind or solar farm and just goes to where there is the most wind or solar resource on average, it may not necessarily guarantee the best fit into a decarbonized energy system.”

That’s because of the complex interactions between production and demand for electricity, as both vary hour by hour, and month by month as seasons change. “What we are trying to do is minimize the difference between the energy supply and demand rather than simply supplying as much renewable energy as possible,” Qiu says. “Sometimes your generation cannot be utilized by the system, while at other times, you don’t have enough to match the demand.”

In New England, for example, the new analysis shows there should be more wind farms in locations where there is a strong wind resource during the night, when solar energy is unavailable. Some locations tend to be windier at night, while others tend to have more wind during the day.

These insights were revealed through the integration of high-resolution weather data and energy system optimization used by the researchers. When planning with lower resolution weather data, which was generated at a 30-kilometer resolution globally and is more commonly used in energy system planning, there was much less complementarity among renewable power plants. Consequently, the total system cost was much higher. The complementarity between wind and solar farms was enhanced by the high-resolution modeling due to improved representation of renewable resource variability.

The researchers say their framework is very flexible and can be easily adapted to any region to account for the local geophysical and other conditions. In Texas, for example, peak winds in the west occur in the morning, while along the south coast they occur in the afternoon, so the two naturally complement each other.

Khorramfar says that this work “highlights the importance of data-driven decision making in energy planning.” The work shows that using such high-resolution data coupled with carefully formulated energy planning model “can drive the system cost down, and ultimately offer more cost-effective pathways for energy transition.”

One thing that was surprising about the findings, says Amin, who is a principal investigator in the MIT Laboratory of Information and Data Systems, is how significant the gains were from analyzing relatively short-term variations in inputs and outputs that take place in a 24-hour period. “The kind of cost-saving potential by trying to harness complementarity within a day was not something that one would have expected before this study,” he says.

In addition, Amin says, it was also surprising how much this kind of modeling could reduce the need for storage as part of these energy systems. “This study shows that there is actually a hidden cost-saving potential in exploiting local patterns in weather, that can result in a monetary reduction in storage cost.”

The system-level analysis and planning suggested by this study, Howland says, “changes how we think about where we site renewable power plants and how we design those renewable plants, so that they maximally serve the energy grid. It has to go beyond just driving down the cost of energy of individual wind or solar farms. And these new insights can only be realized if we continue collaborating across traditional research boundaries, by integrating expertise in fluid dynamics, atmospheric science, and energy engineering.”

Research Report:Decarbonized energy system planning with high-resolution spatial representation of renewables lowers cost

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Solar Energy

Advancing safer lithium energy storage

Published

1 day ago

February 4, 2025

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Advancing safer lithium energy storage

by Erica Marchand

Paris, France (SPX) Feb 04, 2025

Charging our phones has become so routine that we rarely reflect on the breakthrough that made it possible. Rechargeable lithium-ion batteries, introduced commercially in the 1990s, propelled a technological revolution that earned their creators the 2019 Nobel Prize in Chemistry. This key innovation underpins the functionality of today’s smartphones, wireless headphones, and electric vehicles, making them both financially and environmentally practical.

As our devices grow more advanced, the demand for batteries that pack more power while remaining safe continues to rise. Yet engineering such power sources is far from simple. One promising design is the lithium metal battery, which could deliver more stored energy than standard battery types. Unfortunately, its potential is curtailed by a persistent issue: the emergence of tiny threads, or dendrites, that accumulate with each charge. When dendrites build up, they can form metallic connections that degrade battery functionality and pose a serious fire hazard. Until recently, researchers had limited approaches to probe and understand dendrite formation. In a new study led by Dr. Ayan Maity in the lab of Prof. Michal Leskes at the Weizmann Institute of Science’s Molecular Chemistry and Materials Science Department, scientists developed a novel method to identify the factors that spark dendrite growth, as well as to rapidly evaluate various battery components for improved safety and performance.

Rechargeable batteries function by allowing positively charged ions to migrate between the anode (negative electrode) and the cathode (positive electrode) through an electrolyte. Charging forces the ions back into the anode, counter to the usual flow in a typical chemical reaction, thus preparing the battery for another cycle of use. Lithium metal batteries take a different approach by employing a pure lithium metal anode, enabling higher energy storage. However, lithium metal is chemically reactive and quickly forms dendrites when it interacts with the electrolyte. Over time, enough dendrites can short-circuit the battery and raise the likelihood of combustion.

One way to avoid fire risks is to replace the volatile liquid electrolyte with a solid, nonflammable one, often comprising a polymer-ceramic composite. While altering the ratio of polymer to ceramic can influence dendrite growth, finding the ideal formulation remains a challenge for extending battery life.

To investigate, the team employed nuclear magnetic resonance (NMR) spectroscopy, a standard tool for pinpointing chemical structures, and tracked both dendrite formation and the chemical interplay within the electrolyte. “When we examined the dendrites in batteries with differing ratios of polymer and ceramic, we found a kind of ‘golden ratio’: Electrolytes that are composed of 40 percent ceramic had the longest lives,” Leskes explains. “When we went above 40 percent ceramic, we encountered structural and functional problems that impeded battery performance, while less than 40 percent led to reduced battery life.” Intriguingly, batteries with that optimal ratio displayed more dendrites overall, but those dendrites were effectively confined in a way that prevented destructive bridging.

These insights prompted a larger question: what halts the extension of the dendrites? The team hypothesized that a thin covering on the surface of dendrites, called the solid electrolyte interphase (SEI), might be crucial. This layer, formed when dendrites interact with the electrolyte, can affect how lithium ions travel through the battery, and it can also either prevent or accelerate the movement of harmful substances between electrodes. Both of these factors, in turn, can stifle or foster further dendrite development.

Probing the chemical composition of such thin SEI films is inherently difficult, since they measure only a few dozen nanometers thick. The researchers tackled this problem by enhancing the signals in their NMR data using dynamic nuclear polarization. This specialized technique leverages the strong spin of polarized lithium electrons, bolstering signals from the atomic nuclei in the SEI and exposing its chemical makeup. Through this refined lens, the researchers discovered precisely how lithium metal interacts with polymer or ceramic materials, revealing that certain SEI layers can simultaneously improve ion transport and block hazardous substances.

Their findings pave the way to design sturdier, safer, and more powerful batteries that will store greater energy for a longer duration with reduced environmental and economic costs. Such next-generation batteries could power larger devices without having to increase the physical size of the battery itself, while also extending the battery’s life cycle.

“One of the things I love most about this study is that, without a profound scientific understanding of fundamental physics, we would not have been able to understand what happens inside a battery. Our process was very typical of the work here at the Weizmann Institute. We started with a purely scientific question that had nothing to do with dendrites, and this led us to a study with practical applications that could improve everybody’s life,” Leskes says.

Research Report:Tracking dendrites and solid electrolyte interphase formation with dynamic nuclear polarization-NMR spectroscopy

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Solar Energy

Role of barrier films in maintaining the stability of perovskite solar cells

Published

2 days ago

February 3, 2025

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Role of barrier films in maintaining the stability of perovskite solar cells

by Riko Seibo

Tokyo, Japan (SPX) Jan 31, 2025

Perovskite solar cells (PSCs) offer a promising advancement in renewable energy due to their high efficiency, lightweight, and flexible properties. However, their commercial viability is challenged by their vulnerability to environmental conditions, particularly heat and humidity.

To tackle this issue, a research team led by Professor Takashi Minemoto, a Fellow at the Ritsumeikan Advanced Research Academy, alongside Dr. Abdurashid Mavlonov from Ritsumeikan University’s Research Organization of Science and Technology and Dr. Akinobu Hayakawa from Sekisui Chemical Co., Ltd., conducted an in-depth study on the durability of PSC modules under harsh environmental conditions. Their research, published in Volume 286 of *Solar Energy* on January 15, 2025, was first made available online on December 17, 2024.

Discussing the study’s motivation, Prof. Minemoto stated, “Perovskite solar cells stand out as particularly promising due to their low-temperature wet-coating process and compatibility with flexible substrates, offering unique opportunities for the solar industry. However, the stability of perovskite is weak compared with conventional material, which can be improved by fabrication processes such as encapsulation with barrier films.”

For this research, the team analyzed the durability of flexible PSC modules made from methylammonium lead iodide (MAPbI3) and encapsulated them using polyethylene terephthalate (PET) substrates with barrier films of varying water vapor transmission rates (WVTR). These modules were subjected to a damp heat test at 85 C and 85% relative humidity to replicate long-term outdoor conditions.

After 2,000 hours of exposure, researchers measured photovoltaic (PV) performance and assessed module degradation using current-voltage characteristics, spectral reflectance, and electroluminescence imaging. The findings confirmed that high humidity caused the MAPbI3 layer to break down into lead iodide, obstructing charge transport and significantly reducing the efficiency of the PSC modules.

Moreover, the study demonstrated the critical role of barrier films in maintaining module stability. Notably, the module with the lowest WVTR barrier retained 84% of its initial power conversion efficiency, whereas modules with higher WVTR deteriorated rapidly, ceasing to function after just 1,000 hours.

“Our study is the first to report the durability of encapsulated flexible MAPbI3-based PSC modules. When considering solar energy applications for walls and rooftops with weight limits or for mobile platforms, flexible PSCs are a great alternative to the traditional silicon panels. Insights from our study could help industries optimize these modules for highly stable and durable constructs,” explained Prof. Minemoto.

This research underscores the essential role of barrier films in ensuring the long-term viability of flexible PSC modules, which could reshape the photovoltaic industry. By enabling energy generation in a variety of locations, these advancements help alleviate pressure on power grids. Additionally, enhancing the durability of PSCs expands their usability across different environments, further accelerating the global transition to cleaner and more sustainable energy solutions.

Research Report:Perovskite solar cell modules: Understanding the device degradation via damp heat testing

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Solar Energy

Enhancing Durability and Efficiency in Tin-based Perovskite Solar Cells

Published

2 days ago

February 3, 2025

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Enhancing Durability and Efficiency in Tin-based Perovskite Solar Cells

by Riko Seibo

Tokyo, Japan (SPX) Jan 30, 2025

Tin-based perovskite solar cells are being hailed as a promising alternative for next-generation solar energy solutions due to their high efficiency, flexibility, and the potential for low-cost printing. However, replacing lead with tin to avoid environmental issues linked to lead toxicity presents its own challenges. Tin’s propensity to oxidize quickly results in reduced performance and durability compared to lead-based counterparts.

Researchers have developed a method to enhance the stability of tin-based perovskite by incorporating large organic cations into the perovskite structure. This results in a unique two-dimensional layered configuration known as Ruddlesden-Popper (RP) tin-based perovskites. Despite its potential, the precise internal structure and the mechanism through which this configuration improves performance have remained unclear.

In this study, researchers employed electron spin resonance (ESR) to analyze the internal behavior of the RP perovskite solar cell during operation at a microscopic level. Their findings revealed two key insights about the interaction of the materials under different conditions.

First, when the RP perovskite solar cell was not exposed to light, the holes in the hole transport layer diffused into the RP perovskite. This movement created an energy barrier at the interface between the hole transport layer and the RP tin perovskite, preventing electron backflow and leading to better performance.

Second, when exposed to sunlight, the high-energy electrons produced by short-wavelength light (such as ultraviolet rays) moved from the RP tin perovskite to the hole transport layer. This transfer further elevated the energy barrier, thereby enhancing the device’s efficiency.

Understanding the mechanisms behind these performance improvements is crucial for developing tin-based perovskite solar cells with greater efficiency and longer lifespans. These findings could provide important insights for future advancements in the field of solar energy.

Research Report:Operando spin observation elucidating performance-improvement mechanisms during operation of Ruddlesden-Popper Sn-based perovskite solar cells