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Sofia Gilcrease
A WWS electricity system handles changes in demand far differently. To start with, WWS technologies generally suffer less downtime than do current electric power technologies. However, they face inherently more variability; the maximum solar or wind power available at a single location varies over minutes, hours, and days, and this variation generally does not match the demand pattern over the same timescales.
Now scientists at the Beijing Institute of Nanoenergy and Nanosystems and the Georgia Institute of Technology have developed a flat device that can harvest energy from both the sun and wind at the same time. Instead of relying on wind to spin a rotor, the device instead makes use of the triboelectric effect, the same effect behind everyday static electricity. When two different materials repeatedly touch and then separate, the surface of one material can steal electrons from the surface of the other, building up charge.
The researchers coupled a triboelectric nanogenerator with silicon-based solar cells. The triboelectric nanogenerator consists of thin sheets of plastic and Teflon separated by air. When wind blows on the hybrid device, the plastic film vibrates toward and away from the Teflon, generating triboelectricity.
The device the researchers created is about 120 millimeters long and 22 mm wide, making it about as long and wide as a candy bar. However, at 4 mm deep, it is only about as thick as a windowpane. "The device could be extensively installed on the roofs of city buildings," says study co-author Ya Yang at the Beijing Institute of Nanoenergy and Nanosystems.
In experiments, the generator could deliver up to about 8 milliwatts of solar power and up to 26 mw of power from the wind. It could charge a lithium-ion battery from 0.2 to 2.1 volts in 10 minutes, and could also power the kind of temperature and humidity sensors one might find in a smart house, the researchers say.
In the Australian blackout, for example, when a wind turbine tripped off, all synchronous and virtual synchronous machines would have responded to the drop and boosted power output to balance the shortfall. At the same time, VSM-enabled devices on the demand side would have autonomously decreased their power consumption to balance the shortage. Not only would the drop have been reduced, but the number of loads that tripped offline would likely have been smaller.
To beat the cost of the natural gas plants that today back up wind and solar, storing energy would have to cost around $10 per kilowatt-hour. Both startups say their Joule heating systems will meet that price. Lithium-ion batteries, meanwhile, are now at approximately $140/kWH, according to a recent study by MIT economists, and could drop to as low as $20/kWH, although only in 2030 or thereafter.
The situation is unlikely to get better anytime soon, for three reasons. First, as countries everywhere move to decarbonize, the electrification of transportation, heating, and other sectors will cause electricity demand to soar. Second, conventional coal and nuclear plants are being retired for economic and policy reasons, removing stable sources from the grid. And third, while wind and solar-photovoltaic systems are great for the climate and are the fastest-growing sources of electric generation, the variability of their output begets new challenges for balancing the grid.
Recognizing this similarity, we developed a technology called packetized energy management (PEM) to coordinate the energy usage of flexible devices. Coauthor Hines has a longstanding interest in power-system reliability and had been researching how transmission-line failures can lead to cascading outages and systemic blackouts. Meanwhile, Frolik, whose background is in communication systems, had been working on algorithms to dynamically coordinate data communications from wireless sensors in a way that used very little energy. Through a chance discussion, we realized our intersecting interests and began working to see how these algorithms might be applied to the problem of EV charging.
The story was written by an NREL team that leads the international AEG effort. The authors first introduce the Basalt Vista neighborhood, where AEG algorithms are now optimizing community energy resources like electric vehicles, home batteries, water heaters, and rooftop solar. These algorithms originated from ARPA-E innovations at the frontier of distributed control.
Smart grid technology is enabling the effective management and distribution of renewable energy sources such as solar, wind, and hydrogen. The smart grid connects a variety of distributed energy resource assets to the power grid. By leveraging the Internet of Things (IoT) to collect data on the smart grid, utilities are able to quickly detect and resolve service issues through continuous self-assessments. Because utilities no longer have to depend on customers to report outages, this self-healing capability is vital component of the smart grid.
To understand exactly what the problems are, and how they might be addressed, it's helpful to know a little something about how photovoltaic panels are made. While solar energy can be generated using a variety of technologies, the vast majority of solar cells today start as quartz, the most common form of silica (silicon dioxide), which is refined into elemental silicon. There's the first problem: The quartz is extracted from mines, putting the miners at risk of one of civilization's oldest occupational hazards, the lung disease silicosis.
After the publication of the Washington Post story, solar companies' stock prices fell. Investors feared the revelations would undermine an industry that relies so much on its green credentials. After all, that's what attracts most customers and draws public support for policies that foster the adoption of solar energy, such as the Residential Renewable Energy Tax Credit in the United States. Those who purchase residential solar systems can subtract 30 percent of the cost from their tax bills until the incentive expires in 2016.
Toxicity isn't the only concern. Making solar cells requires a lot of energy. Fortunately, because these cells generate electricity, they pay back the original investment of energy; most do so after just two years of operation, and some companies report payback times as short as six months. This energy payback" time is not the same as the time needed to recoup a consumers financial investment in solar panels; it measures investments and payback times in terms of kilowatt-hours, not in terms of money.
Of course, if you manufacture photovoltaic panels with low-carbon electricity (for example, in a solar-powered factory) and install them in a high-carbon-intensity country, the greenhouse-gas-payback time will be lower than the energy-payback time. So perhaps someday, powering photovoltaic-panel manufacturing with wind, solar, and geothermal energy will end concerns about the carbon footprint of photovoltaics.
Smart inverters are poised to fill a big need in the fast-evolving electric-utility industry. As more and more homeowners put PV panels on their roofs, the power they are supplying is reducing the need for big, centralized generating plants. The upshot is that increasing numbers of these traditional power plants are getting retired, and grid operators are scrambling for ways to keep their networks running with the same high level of reliability that their customers have long taken for granted. The combination of smart inverters and new control methods will be essential to helping utilities transition to the grid of the future, in which vast amounts of wind- and solar-generated electricity will be the norm.
The world emits 51 billion tonnes of greenhouse gases into the atmosphere every year. To solve the climate crisis, we need to cut this in half by 2030, and get to zero by 2050. For electricity generation, this means the United States alone needs to increase renewable-energy capacities by 10 times over the next 12 years, which roughly translates to a mind-boggling 400,000 more wind turbines and 2.5 billion more solar panels. To accelerate this progress, Congress has recently passed the Inflation Reduction Act, which includes billions of dollars for clean-energy projects. We will need a lot of workforce to install and maintain these facilities at the front lines, which are not always well suited to humans.
The renewable-energy sector is a great place to search for climate robotics opportunities. Energy sources like solar and wind are already cost competitive compared with fossil fuel. Robots can help eliminate the bottlenecks that limit their expansion.
Starting from the source of the renewable-energy value chain, robots can help remove the labor bottleneck for installing solar and wind farms. For example, one of the most time-consuming and dangerous tasks in building solar farms is heavy lifting. AES, an energy giant, has developed an automated solar farm construction robot to solve this problem. The robot can automatically install solar panels on pre-installed foundations to free workers from lifting. It is also three times as fast as a human, and the new solar layout can generate twice as much solar energy within the same footprint. This is a great example of how outdoor autonomous navigation and robot manipulator control speeds up the renewable-energy transition.
Renewable-energy facilities need routine maintenance to stay efficient. With their rapid expansion over the past decade, there has been a shortage of skilled maintenance technicians. For example, inspecting and repairing onshore wind turbines involves hanging a person 150 meters above the ground, which can be done only by well-trained rope-access technicians. Many wind-farm operators have to hire technicians from out of state at a high cost, which pushes up the overall cost of wind energy.
ANGUS ROCKETTis a Professor in the Department of Materials Science and Engineering at the University of Illinois. He was President in 2011 of and is a Fellow of the American Vacuum Society. He was the 2012 Program Chair and is the 2016 General Chair of the IEEE Photovoltaic Specialists Conference. He has held numerous other offices in the management of this and other international conferences. He was a rotating Research Program Administrator at the Office of Basic Energy Sciences at the U.S. Department of Energy in 2000. He holds a Sc.B. in Physics from Brown University (1980) and a Ph.D. in Materials Science from the University of Illinois (1986). He has won numerous awards for teaching and advising from the College of Engineering at the University of Illinois. His teaching has ranged from introductions to materials engineering for business and engineering students to senior and graduate courses on electronic materials (including a recent book The Materials Science of Semiconductors). His research has concerned ion-assisted growth of semiconductors and fundamental science of growth of materials by molecular beam epitaxy. This was extended to theoretical treatments of the same subject by lattice Monte Carlo and density functional theory methods. At the same time he worked on sputtered hard coatings deposited by reactive magnetron sputtering. He has studied the basic science of solar cell materials and the operation of solar cell devices for 28 years using virtually all of the common materials microchemical and microstructural analysis techniques from SIMS and TEM to STM and photoluminescence. He has also worked on self-assembled nanostructures, MEMS devices, silicide reactions for VLSI contacts, Si-Ge oxidation kinetics for gate dielectrics, superconducting cavity resonators as temperature probes, and optical spectroscopic analysis of combustion. He is an AVS Short Course Instructor for the Photovoltaics and Sputter Deposition of Thin Films short courses. He has also given short courses on thin film deposition processes and fundamentals of thin film solar cells at the IEEE Photovoltaic Specialists Conference, on characterization of photovoltaic materials at the Materials Research Society, and has given short courses on sputter depostion, thin films and photovoltaics in China, Mexico, Sweden, Israel, Brazil, Argentina, and elsewhere. He has published over 190 papers and has given many invited and plenary talks on subjects related to his research. Angus is also a program evaluator for the Accrediation Board for Engineering and Technology (ABET) and an associate editor of the Journal of Photovoltaics.
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