Solar Energy

Twisting, flexible crystals key to solar energy production

Published

4 years ago

March 17, 2021

sarosh

Twisting, flexible crystals key to solar energy production

Researchers at Duke University have revealed long-hidden molecular dynamics that provide desirable properties for solar energy and heat energy applications to an exciting class of materials called halide perovskites.

A key contributor to how these materials create and transport electricity literally hinges on the way their atomic lattice twists and turns in a hinge-like fashion. The results will help materials scientists in their quest to tailor the chemical recipes of these materials for a wide range of applications in an environmentally friendly way.

The results appear online March 15 in the journal Nature Materials.

“There is a broad interest in halide perovskites for energy applications like photovoltaics, thermoelectrics, optoelectronic radiation detection and emission – the entire field is incredibly active,” said Olivier Delaire, associate professor of mechanical engineering and materials science at Duke. “While we understand that the softness of these materials is important to their electronic properties, nobody really knew how the atomic motions we’ve uncovered underpin these features.”

Perovskites are a class of materials that – with the right combination of elements – are grown into a crystalline structure that makes them particularly well-suited for energy applications. Their ability to absorb light and transfer its energy efficiently makes them a common target for researchers developing new types of solar cells, for example. They’re also soft, sort of like how solid gold can be easily dented, which gives them the ability to tolerate defects and avoid cracking when made into a thin film.

One size, however, does not fit all, as there is a wide range of potential recipes that can form a perovskite. Many of the simplest and most studied recipes include a halogen–such as chlorine, fluorine or bromine – giving them the name halide perovskites. In the crystalline structure of perovskites, these halides are the joints that tether adjoining octahedral crystal motifs together.

While researchers have known these pivot points are essential to creating a perovskite’s properties, nobody has been able to look at the way they allow the structures around them to dynamically twist, turn and bend without breaking, like a Jell-O mold being vigorously shaken.

“These structural motions are notoriously difficult to pin down experimentally. The technique of choice is neutron scattering, which comes with immense instrument and data analysis effort, and very few groups have the command over the technique that Olivier and his colleagues do,” said Volker Blum, professor of mechanical engineering and material science at Duke who does theoretical modeling of perovskites, but was not involved with this study. “This means that they are in a position to reveal the underpinnings of the materials properties in basic perovskites that are otherwise unreachable.”

In the study, Delaire and colleagues from Argonne National Laboratory, Oak Ridge National Laboratory, the National Institute of Science and Technology, and Northwestern University, reveal important molecular dynamics of the structurally simple, commonly researched halide perovskite (CsPbBr3) for the first time.

The researchers started with a large, centimeter-scale, single crystal of the halide perovskite, which is notoriously difficult to grow to such sizes – a major reason why this sort of dynamic study has not been achieved before now. They then barraged the crystal with neutrons at Oak Ridge National Laboratory and X-rays at Argonne National Laboratory. By measuring how the neutrons and X-rays bounced off the crystals over many angles and at different time intervals, the researchers teased out how its constituent atoms moved over time.

After confirming their interpretation of the measurements with computer simulations, the researchers discovered just how active the crystalline network actually is. Eight-sided octahedral motifs attached to one another through bromine atoms were caught twisting collectively in plate-like domains and constantly bending back and forth in a very fluid-like manner.

“Because of the way the atoms are arranged with octahedral motifs sharing bromine atoms as joints, they’re free to have these rotations and bends,” said Delaire. “But we discovered that these halide perovskites in particular are much more ‘floppy’ than some other recipes. Rather than immediately springing back into shape, they return very slowly, almost more like Jell-O or a liquid than a conventional solid crystal.”

Delaire explained that this free-spirited molecular dancing is important to understand many of the desirable properties of halide perovskites. Their ‘floppiness’ stops electrons from recombining into the holes the incoming photons knocked them out of, which helps them make a lot of electricity from sunlight. And it likely also makes it difficult for heat energy to travel across the crystalline structure, which allows them to create electricity from heat by having one side of the material be much hotter than the other.

Because the perovskite used in the study – CsPbBr3 – has one of the simplest recipes, yet already contains the structural features common to the broad family of these compounds, Delaire believes that these findings likely apply to a large range of halide perovskites. For example, he cites hybrid organic-inorganic perovskites (HOIPs), which have much more complicated recipes, as well as lead-free double-perovskite variants that are more environmentally friendly.

“This study shows why this perovskite framework is special even in the simplest of cases,” said Delaire. “These findings very likely extend to much more complicated recipes, which many scientists throughout the world are currently researching. As they screen enormous computational databases, the dynamics we’ve uncovered could help decide which perovskites to pursue.”

Source link

Solar Energy

The ZEUS Project to harness solar energy in space with nanowire technology

Published

34 mins ago

October 10, 2024

sarosh

The ZEUS Project to harness solar energy in space with nanowire technology

by Hugo Ritmico

Madrid, Spain (SPXR) Oct 10, 2024

The University of Malaga (UMA) is collaborating in an international consortium to advance the collection and transmission of solar energy in space through the ‘ZEUS’ project, part of the Horizon EIC Pathfinder Challenges. This European project, coordinated by Lund University in Sweden, has been awarded nearly euro 4 million to develop innovative nanowire solar cells designed to operate in the harsh conditions of space.

The ZEUS project, or Zero-loss Energy harvesting Using nanowire solar cells in Space, focuses on creating radiation-resistant photovoltaic cells that can efficiently absorb solar energy. Nanowires, which are needle-shaped structures just 200 nanometers in diameter-much thinner than a human hair-allow for high resistance to radiation and optimal light absorption.

“Covering approximately 10 percent of a surface with active material is all that is needed to absorb as much light as a thin layer covering the entire surface of the same material would do,” explained Enrique Barrigon, professor of Applied Physics I at UMA and the project lead at the university.

Currently, nanowire solar cells used in space achieve around 15% efficiency. ZEUS aims to boost this significantly, potentially reaching up to 47% efficiency by utilizing advanced III-V semiconductor materials. The project also explores transferring these solar cells to flexible, lightweight substrates, which could be used to create large deployable photovoltaic panels for space applications.

In addition to its focus on technical innovation, the ZEUS project emphasizes environmental sustainability, including decarbonization and the efficient use of critical raw materials. Professor Barrigon highlighted that the project not only seeks to demonstrate the commercial viability of nanowire solar cells but also to assess their environmental impact, particularly for space-based power generation systems. One potential application is increasing the power output of communications satellites.

The University of Malaga will play a key role in characterizing these advanced solar cells and conducting the tests required to ensure their durability in the space environment.

The Horizon EIC Pathfinder Challenges program supports pioneering technologies like ZEUS that could shape the future by enabling the development of revolutionary technologies. The University of Malaga is also involved in other projects under this program, including ‘BioRobot-MiniHeart’ and ‘SONICOM,’ furthering its contributions to cutting-edge innovation.

Research Project:Zero-loss Energy harvesting Using nanowire solar cells in Space (ZEUS)

Source link

Solar Energy

Photovoltaic upgrade in Jiaxing, China significantly boosts power output

Published

22 hours ago

October 9, 2024

sarosh

Photovoltaic upgrade in Jiaxing, China significantly boosts power output

by Simon Mansfield

Sydney, Australia (SPX) Oct 09, 2024

The distributed photovoltaic “trade-in” project at the administrative center in Haining city, Jiaxing, Zhejiang province, has significantly increased power generation capacity without expanding space. Launched on Sept 9, the project marks the first of its kind in Zhejiang, following the release of the “Implementation Plan for Large-scale Equipment Renewal in Key Energy Fields” by the National Development and Reform Commission and National Energy Administration on Aug 21.

As China’s installed photovoltaic capacity grows, the issue of recycling aging photovoltaic panels is becoming increasingly important. The “Plan” emphasizes the need to renew and recycle photovoltaic equipment, enhance grid-forming capabilities, and boost power generation efficiency using advanced digital and power electronics technologies.

Haining city, as part of its ambitious new energy development strategy, has set a goal of installing 300,000 kilowatts of photovoltaic capacity annually, aiming for 350,000 kilowatts. By 2026, the city expects to exceed 2 million kilowatts of installed photovoltaic capacity, with an annual green electricity output surpassing 2 billion kilowatt-hours. A key part of this plan involves upgrading older photovoltaic systems to improve both capacity and efficiency.

In 2023, State Grid Zhejiang Electric Power began mapping and assessing installed photovoltaic systems across Haining, from residential rooftops to commercial buildings. The goal was to develop a trade-in program for these systems. The project on the administrative center’s roof is the first pilot under this initiative. It involves replacing 888 P-type 270-watt modules with 731 N-type 590-watt modules, increasing capacity from 237.6 kilowatts to 431.29 kilowatts.

“This helps improve the power generation efficiency and energy utilization efficiency of photovoltaic power stations,” said Chen Huajie, the project leader. The upgraded system is expected to generate 470,000 kilowatt-hours of electricity annually, enough to meet the needs of 100 households in the region. Over its remaining lifespan, it will produce 4.5 million kilowatt-hours of new green electricity, significantly reducing carbon dioxide and sulfur dioxide emissions.

Zhong Jiewen of State Grid Zhejiang Electric Power commented that this pilot project would serve as a model for future initiatives, promoting sustainable economic and environmental development in the region.

Source link

Solar Energy

Solar-powered desalination system requires no extra batteries

Published

23 hours ago

October 9, 2024

sarosh

Solar-powered desalination system requires no extra batteries

by Jennifer Chu | MIT News

Boston MA (SPX) Oct 09, 2024

MIT engineers have built a new desalination system that runs with the rhythms of the sun.

The solar-powered system removes salt from water at a pace that closely follows changes in solar energy. As sunlight increases through the day, the system ramps up its desalting process and automatically adjusts to any sudden variation in sunlight, for example by dialing down in response to a passing cloud or revving up as the skies clear.

Because the system can quickly react to subtle changes in sunlight, it maximizes the utility of solar energy, producing large quantities of clean water despite variations in sunlight throughout the day. In contrast to other solar-driven desalination designs, the MIT system requires no extra batteries for energy storage, nor a supplemental power supply, such as from the grid.

The engineers tested a community-scale prototype on groundwater wells in New Mexico over six months, working in variable weather conditions and water types. The system harnessed on average over 94 percent of the electrical energy generated from the system’s solar panels to produce up to 5,000 liters of water per day despite large swings in weather and available sunlight.

“Conventional desalination technologies require steady power and need battery storage to smooth out a variable power source like solar. By continually varying power consumption in sync with the sun, our technology directly and efficiently uses solar power to make water,” says Amos Winter, the Germeshausen Professor of Mechanical Engineering and director of the K. Lisa Yang Global Engineering and Research (GEAR) Center at MIT. “Being able to make drinking water with renewables, without requiring battery storage, is a massive grand challenge. And we’ve done it.”

The system is geared toward desalinating brackish groundwater – a salty source of water that is found in underground reservoirs and is more prevalent than fresh groundwater resources. The researchers see brackish groundwater as a huge untapped source of potential drinking water, particularly as reserves of fresh water are stressed in parts of the world. They envision that the new renewable, battery-free system could provide much-needed drinking water at low costs, especially for inland communities where access to seawater and grid power are limited.

“The majority of the population actually lives far enough from the coast, that seawater desalination could never reach them. They consequently rely heavily on groundwater, especially in remote, low-income regions. And unfortunately, this groundwater is becoming more and more saline due to climate change,” says Jonathan Bessette, MIT PhD student in mechanical engineering. “This technology could bring sustainable, affordable clean water to underreached places around the world.”

The researchers report details the new system in a paper appearing in Nature Water. The study’s co-authors are Bessette, Winter, and staff engineer Shane Pratt.

Pump and flow

The new system builds on a previous design, which Winter and his colleagues, including former MIT postdoc Wei He, reported earlier this year. That system aimed to desalinate water through “flexible batch electrodialysis.”

Electrodialysis and reverse osmosis are two of the main methods used to desalinate brackish groundwater. With reverse osmosis, pressure is used to pump salty water through a membrane and filter out salts. Electrodialysis uses an electric field to draw out salt ions as water is pumped through a stack of ion-exchange membranes.

Scientists have looked to power both methods with renewable sources. But this has been especially challenging for reverse osmosis systems, which traditionally run at a steady power level that’s incompatible with naturally variable energy sources such as the sun.

Winter, He, and their colleagues focused on electrodialysis, seeking ways to make a more flexible, “time-variant” system that would be responsive to variations in renewable, solar power.

In their previous design, the team built an electrodialysis system consisting of water pumps, an ion-exchange membrane stack, and a solar panel array. The innovation in this system was a model-based control system that used sensor readings from every part of the system to predict the optimal rate at which to pump water through the stack and the voltage that should be applied to the stack to maximize the amount of salt drawn out of the water.

When the team tested this system in the field, it was able to vary its water production with the sun’s natural variations. On average, the system directly used 77 percent of the available electrical energy produced by the solar panels, which the team estimated was 91 percent more than traditionally designed solar-powered electrodialysis systems.

Still, the researchers felt they could do better.

“We could only calculate every three minutes, and in that time, a cloud could literally come by and block the sun,” Winter says. “The system could be saying, ‘I need to run at this high power.’ But some of that power has suddenly dropped because there’s now less sunlight. So, we had to make up that power with extra batteries.”

Solar commands

In their latest work, the researchers looked to eliminate the need for batteries, by shaving the system’s response time to a fraction of a second. The new system is able to update its desalination rate, three to five times per second. The faster response time enables the system to adjust to changes in sunlight throughout the day, without having to make up any lag in power with additional power supplies.

The key to the nimbler desalting is a simpler control strategy, devised by Bessette and Pratt. The new strategy is one of “flow-commanded current control,” in which the system first senses the amount of solar power that is being produced by the system’s solar panels. If the panels are generating more power than the system is using, the controller automatically “commands” the system to dial up its pumping, pushing more water through the electrodialysis stacks. Simultaneously, the system diverts some of the additional solar power by increasing the electrical current delivered to the stack, to drive more salt out of the faster-flowing water.

“Let’s say the sun is rising every few seconds,” Winter explains. “So, three times a second, we’re looking at the solar panels and saying, ‘Oh, we have more power – let’s bump up our flow rate and current a little bit.’ When we look again and see there’s still more excess power, we’ll up it again. As we do that, we’re able to closely match our consumed power with available solar power really accurately, throughout the day. And the quicker we loop this, the less battery buffering we need.”

The engineers incorporated the new control strategy into a fully automated system that they sized to desalinate brackish groundwater at a daily volume that would be enough to supply a small community of about 3,000 people. They operated the system for six months on several wells at the Brackish Groundwater National Research Facility in Alamogordo, New Mexico. Throughout the trial, the prototype operated under a wide range of solar conditions, harnessing over 94 percent of the solar panel’s electrical energy, on average, to directly power desalination.

“Compared to how you would traditionally design a solar desal system, we cut our required battery capacity by almost 100 percent,” Winter says.

The engineers plan to further test and scale up the system in hopes of supplying larger communities, and even whole municipalities, with low-cost, fully sun-driven drinking water.

“While this is a major step forward, we’re still working diligently to continue developing lower cost, more sustainable desalination methods,” Bessette says.

“Our focus now is on testing, maximizing reliability, and building out a product line that can provide desalinated water using renewables to multiple markets around the world,” Pratt adds.

The team will be launching a company based on their technology in the coming months.

This research was supported in part by the National Science Foundation, the Julia Burke Foundation, and the MIT Morningside Academy of Design. This work was additionally supported in-kind by Veolia Water Technologies and Solutions and Xylem Goulds.

Research Report:Direct-drive photovoltaic electrodialysis via flow-commanded current control

Research Report:Flexible batch electrodialysis for low-cost solar-powered brackish water desalination