Solar Energy

Polarized photovoltaic properties emerge

Published

3 years ago

April 4, 2021

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Polarized photovoltaic properties emerge

For the first time, researchers have discovered a way to obtain polarity and photovoltaic behavior from certain nonphotovoltaic, atomically flat (2D) materials. The key lies in the special way in which the materials are arranged. The resulting effect is different from, and potentially superior to, the photovoltaic effect commonly found in solar cells.

Solar power is considered a key technology in the move away from fossil fuels. Researchers continually innovate more efficient means to generate solar energy. And many of these innovations come from the world of materials research.

Research Associate Toshiya Ideue from the University of Tokyo’s Department of Applied Physics and his team are interested in the photovoltaic properties of 2D materials and their interfaces where these materials meet.

“Quite often, interfaces of multiple 2D materials exhibit different properties to the individual crystals alone,” said Ideue. “We have discovered that two specific materials which ordinarily exhibit no photovoltaic effect do so when stacked in a very particular way.”

The two materials are tungsten selenide (WSe2) and black phosphorus (BP), both of which have different crystal structures. Originally, both materials are nonpolar (do not have a preferred direction of conduction) and do not generate a photocurrent under light.

However, Ideue and his team found that by stacking sheets of WSe2 and BP together in the right way, the sample exhibited polarization, and when a light was cast on the material, it generated a current. The effect takes place even if the area of illumination is far from the electrodes at either end of the sample; this is different from how the ordinary photovoltaic effect works.

Key to this behavior is the way the WSe2 and BP are aligned. The crystalline structure of BP has reflective, or mirror, symmetry in one plane, whereas WSe2 has three lines of mirror symmetry. When the symmetry lines of the materials align, the sample gains polarity. This kind of layer stacking is delicate work, but it also reveals to researchers new properties and functions that could not be predicted just by looking at the ordinary form of the materials.

“The biggest challenge for us will be to find a good combination of 2D materials with higher electric-generation efficiency and also to study the effect of changing the angles of the stacks,” said Ideue.

“But it’s so rewarding to discover never-before-seen emergent properties of materials. Hopefully, one day this research could improve solar panels. We would like to explore more unprecedented properties and functionalities in nanomaterials.”

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Solar Energy

Salt battery enhances osmotic energy capture from river-sea convergence

Published

4 hours ago

April 26, 2024

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Salt battery enhances osmotic energy capture from river-sea convergence

by Simon Mansfield

Sydney, Australia (SPX) Apr 26, 2024

Estuaries, where freshwater rivers meet the sea, are not only ideal for birdwatching and kayaking but also serve as potential sources of renewable, “blue” osmotic energy. A recent study published in ACS Energy Letters highlights a breakthrough in this field, involving a semipermeable membrane designed to harvest osmotic energy from the salt gradients between these waters, effectively converting it into electrical power. The novel membrane demonstrated more than double the output power density compared to conventional commercial membranes in laboratory tests.

Osmotic energy harnessing, feasible anywhere salt gradients exist, has seen various technological approaches. A notable method utilizes a series of reverse electrodialysis (RED) membranes, described as a “salt battery,” which generates electricity from the pressure disparities induced by the salt gradients. This process involves positively charged ions like sodium from seawater moving into freshwater, thus increasing membrane pressure. Optimizing this transfer and reducing internal electrical resistance are critical for enhancing energy capture.

Building on previous research, Dongdong Ye, Xingzhen Qin, and their colleagues developed a new semipermeable membrane using eco-friendly materials aimed at reducing internal resistance and maximizing energy output. Their approach involved creating decoupled channels within the membrane-one for ion transport made of negatively charged cellulose hydrogel, and another for electron transport consisting of an electrically conductive polymer, polyaniline.

Testing in a controlled environment simulating an estuary, the prototype achieved an output power density that was 2.34 times higher than that of a standard commercial RED membrane, with consistent performance over 16 days. Furthermore, when arranged into an array of 20 membranes, this setup successfully powered devices like a calculator, LED light, and stopwatch independently.

The researchers believe their innovative design opens new possibilities for using ecological materials in RED membranes and enhancing the efficiency of osmotic energy systems for practical applications.

Research Report:Decoupled Ionic and Electronic Pathways for Enhanced Osmotic Energy Harvesting

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Solar Energy

Survey reveals broad support for solar projects among nearby residents

Published

5 hours ago

April 26, 2024

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Survey reveals broad support for solar projects among nearby residents

by Clarence Oxford

Los Angeles CA (SPX) Apr 26, 2024

A national survey conducted by Lawrence Berkeley National Laboratory, Michigan State University, and the University of Michigan reveals that Americans living close to large-scale solar (LSS) farms generally view them favorably. The survey, which queried nearly 1,000 residents within three miles of LSS installations, indicated that positive attitudes towards these projects are nearly three times more prevalent than negative ones.

This survey is notable as it represents the first nationwide, representative assessment of public perceptions towards solar developments. Among those surveyed, 42% supported further solar developments in their communities, while only 18% opposed more projects. Interestingly, over 80% of participants were initially unaware of the solar projects prior to their construction, and a third remained unaware until they participated in the survey.

Doug Bessette, an associate professor in the Department of Community Sustainability at Michigan State University, highlighted the generally positive feedback but noted challenges with larger projects and those located very close to residences. “The responses from residents were generally positive, which is good to see considering the amount of solar that is likely to be developed in the coming years,” Bessette said. “At the same time, we saw more negative attitudes associated with larger projects and somewhat less support amongst neighbors living really close, within a quarter mile of projects, so there’s a lot of work to be done.”

Residents showed a clear preference for using disturbed sites like landfills for future projects over farmland and expressed a strong desire for more community involvement in the planning process. Local hiring and ownership were also preferred. For accurate information on potential impacts, residents trust fellow community members, local organizations, and university staff the most.

Jake White, a doctoral student involved in the study, emphasized the importance of community engagement. “Our findings show that LSS neighbors want to be engaged more, with respondents strongly supporting increased opportunities for participation in planning processes,” White explained. “This demonstrates a big opportunity for improvement in LSS planning processes – hopefully leading to better outcomes for all.”

The survey also suggests that while there is substantial support for solar energy, significant efforts in community engagement and communication are necessary to enhance public acceptance and address equity concerns within future LSS projects.

“We were happy to see this last one,” Bessette noted.

Research Report:Perceptions of Large-Scale Solar Project Neighbors: Results From a National Survey

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Solar Energy

Super grids could stabilize Caribbean power during hurricanes, study finds

Published

6 hours ago

April 26, 2024

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Super grids could stabilize Caribbean power during hurricanes, study finds

by Clarence Oxford

Los Angeles CA (SPX) Apr 26, 2024

The potential for “super grids” to stabilize energy supply during hurricanes is being explored by researchers at the Department of Energy’s Oak Ridge National Laboratory.

The Caribbean islands, traditionally reliant on expensive imported fossil fuels, are transitioning to harnessing local solar and wind resources. However, the prevalence of hurricanes poses significant challenges to solar power generation. Oak Ridge researchers have developed a detailed modeling method to anticipate the decrease in solar power output during stormy conditions and examined how interconnected grids could help mitigate these energy losses.

Rodney Itiki, the lead researcher, emphasizes the importance of such infrastructure planning to ensure consistent electricity access across the Caribbean, including 12 island nations and U.S. territories like Puerto Rico and the U.S. Virgin Islands. “The loss of the sun’s energy during hurricanes is likely to become increasingly important on islands like Puerto Rico, which declared a goal of converting to all-renewable energy by 2050,” said Itiki.

The team’s research involved simulating how various configurations of interconnected grids would sustain electricity availability during hurricanes. They analyzed scenarios where large hurricanes could disrupt power from solar plants while assessing potential solutions like laying high-voltage undersea cables.

“This is one of the major contributions of the research, because when we design the power system, we need to do it considering all possible cases – most of all, the worst-case scenario,” said Itiki, a postdoctoral research associate with ORNL’s Power Systems Resilience group.

Their simulations showed that a super grid connecting the U.S., Caribbean islands, and South America could enhance regional energy reliability. The most effective configuration was found to be a combined U.S.-Caribbean grid, whereas a standalone Caribbean grid was less effective due to the alignment of hurricanes with the islands.

Itiki’s inspiration for studying grid interconnectivity came from observing successful subsea electrical links like those between the United Kingdom and Germany. Following Hurricane Maria’s devastating impact on Puerto Rico in 2017, which resulted in prolonged power outages, he focused on the potential of connecting Puerto Rico’s grid with Florida’s.

Originally concentrating on wind energy, Itiki shifted to include solar power dynamics after improvements in turbine technology. His upcoming projects aim to merge his models of solar and wind energy to evaluate how super grids might broadly improve energy reliability in both the Caribbean and mainland U.S.

Itiki also underlined the need for more studies to explore the environmental and economic feasibility of installing undersea cables, though his current models offer valuable insights for planning and managing energy systems during severe weather.

Research Report:Method for Spatiotemporal Solar Power Profile Estimation for a Proposed U.S.-Caribbean-South America Super Grid under Hurricanes