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76

Jokes / 10 Song Lyrics That Were Definitely Written About Teaching

« on: April 22, 2017, 02:17:10 AM »

1. “Can’t keep my hands to myself! I mean, I could but why would I want to?”
Those students, usually boys, that seriously just cannot keep their hands off of their classmates, class materials, desks, doors, anything really.

2. “I woke up like this.”
No seriously, I snoozed my alarm like 5 times this morning, I don’t even know how I made it here before the morning bell rang.

3. “Nah nah honey, I’m good; I could have another but I probably should not.”
Faculty breakfast, already 3 donuts deep. No Mrs. Johnson I do NOT need another one of your homemade blueberry cake donuts!!

4. “I know that I can’t take no more, it ain’t no lie. I want to see you out that door, baby, BYE BYE BYE.”
When you finally kick out that student that has been a monster since they walked in the door this morning.

5. “Pour up, drank, head shot, drank. Sit down, drank, stand up, drank. Pass out, drank, wake up, drank. Faded, drank, faded, drank.”
It’s the summer and we don’t have to be at work tomorrow! Or it’s just the weekend… or a Wednesday. Whatever, we need a drink.

6. “Y’all gon’ make me act a FOOL. Up in here, up in here.”
The dismissal bell is about to ring. If you make me write a referral in the last 5 minutes of class SO HELP ME GOD.

7. “Why you gotta be so rude? Don’t you know I’m human too?”
The answer was no, you can’t go to the bathroom for the 3rd time this period. Please, don’t tell me you’re going to piss on the floor then.

8. “This girl is on FIYAHHH!”
Just rocked that formal observation, WUDDUP. (..sorry male teachers.)

9. “Is it too late now to say I’m sorry?”
Yes, I know grades close today. No, you can’t make up the 20 assignments you neglected to do all semester.

10. “I don’t have money on my mind, I do it for the love.”
But at the end of the day, we all know this could not be more true about teaching. And if you don’t know this Sam Smith song, look it up right now.

77

EEE / Mid-Atlantic Grid Can Lose Coal and Nuclear, and Remain Reliable With NG

« on: April 22, 2017, 02:04:04 AM »

Mid-Atlantic grid operator PJM has modeled a future with more wind and solar power, cheap natural gas, and retiring nuclear and coal power plants -- integrated under projected peak conditions and in hypothetical heat waves and cold snaps -- and found that this increasingly diverse generation mix doesn’t threaten grid reliability, at least in the near term.

The model sets an upper bound of about 20 percent on how much renewable energy -- wind, namely -- that the 13-state transmission grid operator can take, before reliability issues start to arise.

PJM’s analysis of reliability and fuel diversity (PDF), released Thursday, is among many across the country tackling the challenge of integrating intermittent renewable resources into the grid. In PJM’s case, however, it was triggered mainly by the growth of natural gas as a primary generation fuel, raising the question of whether that resource is reliable enough to replace retiring coal-fired and nuclear power plants.

PJM’s resource mix has changed rapidly over the past decade. In 2005, coal and nuclear resources generated 91 percent of its electricity. But over the past six years, those figures have dropped to 33 percent for coal and 18 percent for nuclear, while natural gas has grown to represent 33 percent of the power mix.

Meanwhile, renewables including hydro made up 6 percent of PJM’s 2016 generation mix. Demand response, which had accounted for roughly the same amount of capacity as renewables as recently as 2015, has shrunk a bit in the past two years after PJM implemented new capacity performance rules.

78

EEE / Smart Circuit Breakers: The Next Frontier of the Grid Edge?

« on: April 22, 2017, 02:01:59 AM »

Go down to the basement of your office building or apartment complex, or the garage of your home, and you’ll find a ubiquitous piece of electrical equipment that could be the next frontier for smart, connected energy management -- the circuit breaker.

Circuit breakers are a multibillion-dollar market. Projections show a global market of between $13 billion and $19 billion by decade's end, dominated by giants such as Siemens, ABB, Schneider Electric, Eaton, Toshiba, Mitsubishi, and GE’s Alstom.

Most of the circuit breakers out there are fairly simple, electromechanical devices that sit idle the vast majority of the time. But the latest versions are coming with features like wireless connectivity and computing power that are meant to turn them into something more like a smart meter or a smartphone.

That, in turn, could allow utilities and building owners to start tracking the interplay of grid-supplied power and on-site distributed energy resources (DERs) like solar, batteries and plug-in electric vehicles, or demand response. As more and more buildings start to get these smart, networked circuit breakers, they could augment -- or even replace -- a lot of other equipment used for this purpose today.

Eaton and EPRI test smart circuit breakers as virtual meters, load controllers

That’s the idea behind the field trial of Eaton’s energy management circuit breaker (EMCB). Last year, the electrical equipment giant started deploying its smart circuit breakers at about 500 homes with 12 U.S. utilities, including Duke Energy, Southern Company, CenterPoint, ComEd and Pepco. Over the next year, it will be working with the Electric Power Research Institute (EPRI) to see if they’re capable of collecting and sharing data accurately, receiving and sending controls to other smart equipment like thermostats or water heaters, and even shifting homes on and off of grid power during emergencies.

“We’re trying to understand the functionality and potential value propositions for each device, working on utility-owned use cases,” Tom Reddoch, the EPRI senior technical executive in charge of the project, said in a recent interview. “This is a powerful device to control solar; it’s powerful to control storage; it’s powerful as a [measurement and verification] device.” They’re also particularly useful for electric vehicle applications, because they’re able to serve all the requirements of 240-volt EV charging equipment. "The charging infrastructure is being integrated into the breakers,” Reddoch said.

Eaton and EPRI will have devices in the field through 2017, and by next year, they "should have sufficient field data to answer questions about the functional features,” he added. That will also provide feedback about potential modifications that Eaton may want to include in each device, he said.

That’s valuable insight for Eaton, which is looking at ways to embed the technology across its product lines. "We’ve been in the circuit protection device business for years; it's in a nice place in the distribution ecosystem," Ron Thompson, Eaton's director of business development for emerging markets and new technologies, said in a recent interview.

Each year, Eaton manufactures about 50 million poles -- individual 1-inch breakers -- for the circuit breakers it embeds in power distribution equipment like switchboards and panel boards, and "a percentage of those could eventually become smart breakers. Any time a building is built or retrofitted, that becomes part of the real estate of our products -- and if the breakers are intelligent, I don’t have to put a meter in or a relay for the circuit -- I don’t have to do a lot of things."

As EMCBs become standard equipment, they could start to serve as energy billing settlement and load control devices, similar to how smart meters function today, but down to individual circuits in homes and buildings, Thompson said. “The breaker has Wi-Fi communication built in, to connect to the Wi-Fi in the home,” he said. “In real time, if a utility is experiencing an under-voltage or under-frequency condition, we can measure it and respond,” he said.
Solid state technology -- the next step in smart circuit breakers?

There are challenges in bringing new technologies to such an entrenched market, however. “The circuit breaker world has been one of the trickiest in terms of customer acceptance,” said John DeBoer, new product introduction manager for Siemens, in an interview last month. “It’s a classic industry that’s been really grounded in safety and reliable distribution of power. Their job is to sit there for a long time, and wait for that one moment when something unsafe happens in the electrical system. They’re trying to protect that wire.”

Even so, Siemens is looking far ahead for the next generation of smart circuit breakers, including the latest in solid-state power electronics. In February, the German industrial giant invested in Charlotte, N.C.-based startup Atom Power, which has designed a solid-state circuit breaker that replaces the electromechanical features of a traditional device with digital power control.

Solid-state circuit breakers have actually been around since the 1970s. "But the technology wasn’t ready, and the customers definitely weren't going to pay for them," DeBoer said.

But advances in solid-state power electronics have increased the capability and lowered the price of devices like these, he said. In terms of design, “the biggest thing that Atom Power has done well is they’ve gotten the solid-state device fully in series. It is sitting entirely within the conduction path,” he said.

That makes Atom Power’s devices faster, and thus safer, than classic electromechanical systems, which take a few milliseconds to move, he said. “A solid-state device can move at the speed of a computer,” improving the device’s kilo-amperes interrupting capacity, or KAIC, a key measure of a circuit breaker’s ability to perform its core function of keeping electrical equipment safe from surges, arcs and other hazards.

Beyond that, Atom Power’s integrated switches and panels can serve all the smart functions of an inverter or smart meter, he said. “The market for the metering of energy is absolutely exploding right now -- and it’s metering at all levels. I would say it has more than doubled in the past year or year and a half. The big trend is metering in buildings for multiple purposes at the same time. With the complexity of energy these days, and the growth in smart meters, it’s made energy more complicated and more confusing.”

The drawback is that solid-state power electronics are still expensive. “These things are still five to 10 times more expensive than a traditional circuit breaker,” DeBoer said. “The incremental value, though, is that we’re seeing healthy year-over-year cost reductions, like you’re seeing in the semiconductor world.”

79

EEE / Modern alchemy creates luminescent iron molecules

« on: April 22, 2017, 01:55:18 AM »

A group of researchers at Lund University in Sweden have made the first iron-based molecule capable of emitting light. This could contribute to the development of affordable and environmentally friendly materials for e.g. solar cells, light sources and displays.

For over 50 years, chemists have developed metal-based dye molecules for a wide range of different applications, such as displays and solar cells. This would ideally involve common and environmentally friendly metals like iron, but despite a number of attempts no one has been able to develop an iron-based dye molecule that can emit light until now. Researchers around the world have therefore instead largerly had to resort to various rare and precious metals, such as ruthenium, which have more easily provided the desired properties.

Through advanced molecular design, the Lund researchers have now successfully manipulated the electronic properties of iron-based molecules so that they much better resemble the ruthenium-based substances.

By doing so, they have, for the first time, created an iron-based dye molecule which is able to not only capture light, but also subsequently emit light of a different colour. The latter is significantly more difficult to achieve, which contributes to why the researchers' accomplishment in showing that the new iron molecule emits orange light is so important.

"Medieval alchemists tried to produce gold from other substances, but failed. You could say that we have succeeded in performing modern alchemy by giving the iron properties which resemble those of ruthenium," says Kenneth Wärnmark, Professor of Chemistry at the Faculty of Science at Lund University.

The new study, which is now published in Nature, describes an iron complex with a record-breaking life span in its light-absorbing and luminescent state: 100 picoseconds, which is less than a billionth of a second. But despite the seemingly inconceivably short time interval, it is quite sufficient.

"In the world of chemistry, this is enough time for the molecules to emit light," says Villy Sundström, Professor of Chemistry at Lund University.

These results provide an important step towards possible future applications as a luminescent material, such as for lighting and displays, as well as light absorbers in solar cells and photocatalysts for producing solar fuel. In order to reach this goal, a continued development of new, and even better molecules is necessary.

"We expect that the next step to develop the actual molecules that are suitable for commercial applications could take another five years," says Petter Persson, chemistry researcher at Lund University.

In addition to the researchers from Lund, the study has included researchers from the Ångström Laboratory in Uppsala and from Copenhagen.

80

EEE / Bio-inspired energy storage: A new light for solar power

« on: April 22, 2017, 01:54:26 AM »

Inspired by an American fern, researchers have developed a groundbreaking prototype that could be the answer to the storage challenge still holding solar back as a total energy solution.

The new type of electrode created by researchers from RMIT University in Melbourne, Australia, could boost the capacity of existing integrable storage technologies by 3000 per cent.

But the graphene-based prototype also opens a new path to the development of flexible thin film all-in-one solar capture and storage, bringing us one step closer to self-powering smart phones, laptops, cars and buildings.

The new electrode is designed to work with supercapacitors, which can charge and discharge power much faster than conventional batteries. Supercapacitors have been combined with solar, but their wider use as a storage solution is restricted because of their limited capacity.

RMIT's Professor Min Gu said the new design drew on nature's own genius solution to the challenge of filling a space in the most efficient way possible -- through intricate self-repeating patterns known as "fractals."

"The leaves of the western swordfern are densely crammed with veins, making them extremely efficient for storing energy and transporting water around the plant," said Gu, Leader of the Laboratory of Artificial Intelligence Nanophotonics and Associate Deputy Vice-Chancellor for Research Innovation and Entrepreneurship at RMIT.

"Our electrode is based on these fractal shapes -- which are self-replicating, like the mini structures within snowflakes -- and we've used this naturally-efficient design to improve solar energy storage at a nano level.

"The immediate application is combining this electrode with supercapacitors, as our experiments have shown our prototype can radically increase their storage capacity -- 30 times more than current capacity limits.

"Capacity-boosted supercapacitors would offer both long-term reliability and quick-burst energy release -- for when someone wants to use solar energy on a cloudy day for example -- making them ideal alternatives for solar power storage."

Combined with supercapacitors, the fractal-enabled laser-reduced graphene electrodes can hold the stored charge for longer, with minimal leakage. The fractal design reflected the self-repeating shape of the veins of the western swordfern, Polystichum munitum, native to western North America.

Lead author, PhD researcher Litty Thekkekara, said because the prototype was based on flexible thin film technology, its potential applications were countless.

"The most exciting possibility is using this electrode with a solar cell, to provide a total on-chip energy harvesting and storage solution," Thekkekara said.

"We can do that now with existing solar cells but these are bulky and rigid. The real future lies in integrating the prototype with flexible thin film solar -- technology that is still in its infancy.

"Flexible thin film solar could be used almost anywhere you can imagine, from building windows to car panels, smart phones to smart watches. We would no longer need batteries to charge our phones or charging stations for our hybrid cars.

"With this flexible electrode prototype we've solved the storage part of the challenge, as well as shown how they can work with solar cells without affecting performance. Now the focus needs to be on flexible solar energy, so we can work towards achieving our vision of fully solar-reliant, self-powering electronics."

81

EEE / Americans used more clean energy in 2016

« on: April 22, 2017, 01:53:34 AM »

Americans used more renewable energy in 2016 compared to the previous year, according to the most recent energy flow charts released by Lawrence Livermore National Laboratory. Overall, energy consumption was nearly flat.

Each year, the Laboratory releases energy flow charts that illustrate the nation's consumption and use of energy. Americans used 0.1 quads (quadrillion BTU), more in 2016 than in 2015. A BTU, or British Thermal Unit, is a unit of measurement for energy; 3,400 BTU is equivalent to about 1 kilowatt-hour.

Prices for photovoltaic panels have fallen dramatically over the past decade, contributing to solar energy's rapid growth, which rose by 0.15 quads or 38 percent in 2016, with significant additions in the electricity, commercial and residential sectors. "Two thirds of that increase was in the electric sector," said A.J. Simon, group leader for LLNL's energy program. "These are large installations of thousands of solar panels, usually in the desert." Installations on the roofs of homes and warehouses account for the rest of the additions.

Likewise, more wind power is contributing to the nation's utility grid. Use of wind power rose by 19 percent or 0.33 quads. "Generous incentives for renewable energy, combined with improved 'know-how' in siting and building wind farms, has led to a favorable environment for growth in this sector," Simon said.

Coal use decreased by 9 percent to 14.2 quads, mostly due to decreased coal supply to the electricity sector. That supply has been replaced by wind, solar and natural gas. Overall, natural gas use rose by 1 percent to 28.5 quads.

Energy use in the residential, commercial and industrial sectors all declined slightly, while consumption of fossil fuels in the transportation sector rose by 0.5 quads or 2 percent.

All energy use results in some losses, shown on the charts as rejected energy. This energy most often takes the form of waste heat, such as the warm exhaust from automobiles and furnaces. The efficiency of the nation's cars, lightbulbs and factories determines how much waste heat is produced, and how much of fuel and electricity can be put to productive use.

This year marks two changes to the energy flow chart. The Energy Information Administration has changed the way it analyzes and reports renewable energy use, and those changes are reflected in the 2016 chart as well as a revision to the 2015 analysis. Additionally, the estimate of efficiency of the industrial sector has been reduced from 80 percent to 49 percent to align with recent analysis at the DOE's Advanced Manufacturing Office. LLNL reports all year-over-year changes on a basis consistent with the new methodology.

82

EEE / New class of optoelectronic materials developed

« on: April 22, 2017, 01:52:43 AM »

Semiconductors are used for myriad optoelectronic devices. However, as devices get smaller and smaller and more demanding, new materials are needed to ensure that devices work with greater efficiency. Now, researchers at the USC Viterbi School of Engineering have pioneered a new class of semiconductor materials that might enhance the functionality of optoelectronic devices and solar panels -- perhaps even using one hundred times less material than the commonly used silicon.

Researchers at USC Viterbi, led by Jayakanth Ravichandran, an assistant professor in the Mork Family Department of Chemical Engineering and Material Sciences and including Shanyuan Niu, Huaixun Huyan, Yang Liu, Matthew Yeung, Kevin Ye, Louis Blankemeier, Thomas Orvis, Debarghya Sarkar, Assistant Professor of Electrical Engineering Rehan Kapadia, and David J. Singh, a professor of physics from University of Missouri, have developed a new class of materials that are superior in performance and have reduced toxicity. Their process, documented in "Bandgap Control via Structural and Chemical Tuning of Transition Metal Perovskite Chalcogenide," is published in Advanced Materials.

Ravichandran, the lead on this research, is a materials scientist, who has always been interested in understanding the flow of electrons and heat through materials, as well as the how electrons interact within materials. This deep knowledge of how material composition affects electron movement was critical to Ravichandran's and his colleagues' most recent innovation.

Computers and electronics have been getting better, but according to Jayakanth Ravichandran, the principal investigator of this study, "the performance of the most basic device -- the transistors -- are not getting better." There is a plateau in terms of performance, as noted by what is considered the "end of Moore's law." Similar to electronics, there is a lot of interest to develop high performance semiconductors for opto-electronics. The collaborative team of material scientists and electrical engineers wanted to develop new materials which could showcase the ideal optical and electrical properties for a variety of applications such as displays, light detectors and emitters, as well as solar cells.

The researchers developed a class of semiconductors called "transition metal perovskite chalcogenides." Currently, the most useful semiconductors don't hold enough carriers for a given volume of material (a property which is referred to as "density of states") but they transport electrons fast and thus are known to have high mobility. The real challenge for scientists has been to increase this density of states in materials, while maintaining high mobility. The proposed material is predicted to possess these conflicting properties.

As a first step to show its potential applications, the researchers studied its ability absorb and emit light. "There is a saying," says Ravichandran of the dialogue among those in the optics and photonics fields, "that a very good LED is also a very good solar cell." Since the materials Ravichandran and his colleagues developed absorb and emit light effectively, solar cells are a possible application.

Solar cells absorb light and convert it into electricity. However, solar panels are made of silicon, which comes from sand via a highly energy intensive extraction process. If solar cells could be made of a new, alternative semiconductor material such as the one created by the USC Viterbi researchers -- a material that could fit more electrons for a given volume (and reducing the thickness of the panels), solar cells could be more efficient -- perhaps using one hundred times less material to generate the same amount of energy. This new material, if applied in the solar energy industry, could make solar energy less expensive.

While it is a long road to bring such a class of materials to market, the next step is to recreate this material in an ultra-thin film form to make solar cells and test their performance. "The key contribution of this work," says Ravichandran, "is our new synthesis method, which is a drastic improvement from earlier studies. Also, our demonstration of wide tunability in optical properties (especially band gap) is promising for developing new optoelectronic devices with tunable optical properties."

83

EEE / Mechanism behind the electric charges generated by photosynthesis

« on: April 22, 2017, 01:49:49 AM »

Photosynthesis requires a mechanism to produce large amounts of chemical energy without losing the oxidative power needed to break down water. A Japanese research team has clarified part of this mechanism, marking another step towards the potential development of artificial photosynthesis. The findings were published on February 27 in the online edition of The Journal of Physical Chemistry Letters.

The team was led by Professor KOBORI Yasuhiro (Kobe University Molecular Photoscience Research Center) and PhD student HASEGAWA Masashi (Graduate School of Science) with Associate Professor MINO Hiroyuki (Nagoya University Graduate School of Science).

During the water-splitting reaction in photosynthesis, plants produce oxygen by converting solar energy into chemical energy, providing the energy source necessary for their survival. This reaction is carried out by a protein complex in chloroplasts (located in leaves) called the photosystem II complex.

In 2015 Professor Kobori's research team succeeded in analyzing the electronic interactions and 3-dimensional placement of the initial charge separation produced directly after photoreaction in the photosynthetic reaction center of purple bacteria, which do not cause the oxidation potential for water-splitting. However, in the photosystem II complex for higher plants, the configuration of the initial charge separation state was unclear, and it was a mystery as to how it led to an effective water-splitting reaction while retaining the high oxidative power.

The scientists extracted thylakoid membranes (where the photoreaction takes place in photosynthesis) from spinach, added a reducing agent, and irradiated the samples. This enabled them to detect microwave signals from the initial charge separation state to a degree of accuracy of a 10 millionth of a second. They developed a method of analyzing the microwave signals using spin polarization imaging. For the first time it was possible to carry out 3D view analysis of the configuration of the electric charge produced directly after exposure to light as a reactive intermediate. This was done with an accuracy to within 10 millionth of a second, as consecutive photography. Based on this visualization, they also quantified the electronic interaction that occurs when electron orbits overlap for molecules with electric charges.

The initial electric charge separation structure clarified by this analysis was not very different from the structure before the reaction, but the imaging analysis showed that the positive electric charge that occurred in the pigment as a reactive intermediate existed disproportionately in chlorophyll single molecules. It suggests that there is strong stabilization caused by electrostatic interaction between the charges.

It has been revealed that the return of the negative charge is suppressed, since the overlap between electron orbits is greatly limited by the insulating effect of the vinyl group terminus. This means that it becomes possible to use the high oxidizing powers of the positive charge in chlorophyll (PD1) for the subsequent oxidative decomposition of water.

Based on these findings, researchers have unlocked part of the mechanism to effectively produce high amounts of chemical energy without loss of the oxidative power needed to split water in photosynthesis. These findings could help to design an "artificial photosynthesis system" that can provide a clean energy source by efficiently converting solar energy into large amounts of electricity and hydrogen. The application of this principle could contribute to solving issues with energy, the environment and food shortages.

84

EEE / New perovskite ink opens window for quality cells

« on: April 22, 2017, 01:49:15 AM »

Scientists at the U.S. Department of Energy's (DOE) National Renewable Energy Laboratory (NREL) developed a new perovskite ink with a long processing window that allows the scalable production of perovskite thin films for high-efficiency solar cells.

Proven highly efficient at converting sunlight into electricity, perovskite solar cells have yet to move beyond the laboratory. The crystalline structure of perovskites must be carefully grown upon a substrate, which is normally done by laboratory-scale spin coating -- a technology that can't be scaled to large-scale manufacturing. The best devices fabricated using scalable deposition methods, which are suitable for future module production, still lag behind state-of-the-art spin-coated devices.

How the NREL scientists overcame this obstacle is spelled out in a new paper published in Nature Energy, Perovskite ink with wide processing window for scalable high-efficiency solar cells. Kai Zhu, a senior scientist in NREL's Chemistry and Nanoscience Center, is lead author. The co-authors are Mengjin Yang, Zhen Li, Matthew Reese, Obadiah Reid, Dong Hoe Kim, Sebastian Siol, Talysa Klein, Joseph Berry, and Michael van Hest from NREL, and Yanfa Yan from the University of Toledo.

To create a perovskite film, a coating of chemicals is deposited on a substrate and heated to fully crystalize the material. The various steps involved often overlap with each other and complicate the process. One extremely critical stage requires the addition of an antisolvent that extracts the precursor chemicals, and thus create crystals of good quality. The window for this step opens and closes within seconds, which is detrimental for manufacturing due to the precision required to make this time window.

NREL researchers were able to keep that window open as long as 8 minutes.

The formula for the precursor perovskite ink included a chlorine-containing methylammonium lead iodide precursor along with solvent tuning, coupled with an antisolvent, which could be deposited onto the substrate by either spin-coating or blade-coating methods. Both methods were tested and produced indistinguishable film morphology and device performance. Blade-coating is more attractive to manufacturers because it can easily be scaled up.

The researchers tested one precursor ink containing excess methylammonium iodide (MAI) and a second containing added methylammonium chloride (MACI). The MACI proved most effective in reducing the length of heat treatment the perovskites require, cutting the time to about a minute compared to 10 minutes for the MAI solution. The shorter time also should make the process more attractive to manufacturers.

Using blade-coated absorbers, NREL scientists made a four-cell perovskite module measuring about 12.6-square centimeters. Of that, 11.1-square centimeters were active in converting sunlight to energy and did so with a stabilized efficiency of 13.3 percent.

85

EEE / New world record for solar hydrogen production

« on: April 22, 2017, 01:48:33 AM »

Scientists at the U.S. Department of Energy's (DOE) National Renewable Energy Laboratory (NREL) recaptured the record for highest efficiency in solar hydrogen production via a photoelectrochemical (PEC) water-splitting process.

The new solar-to-hydrogen (STH) efficiency record is 16.2 percent, topping a reported14 percent efficiency in 2015 by an international team made up of researchers from Helmholtz-Zentrum Berlin, TU Ilmenau, Fraunhofer ISE and the California Institute of Technology. A paper in Nature Energy titled Direct Solar-to-hydrogen Conversion via Inverted Metamorphic Multijunction Semiconductor Architectures outlines how NREL's new record was achieved. The authors are James Young, Myles Steiner, Ryan France, John Turner, and Todd Deutsch, all from NREL, and Henning Döscher of Philipps-Universität Marburg in Germany. Döscher has an affiliation with NREL.

The record-setting PEC cell represents a significant change from the concept device Turner developed at NREL in the 1990s.

Both the old and new PEC processes employ stacks of light-absorbing tandem semiconductors that are immersed in an acid/water solution (electrolyte) where the water-splitting reaction occurs to form hydrogen and oxygen gases. But unlike the original device made of gallium indium phosphide (GaInP2) grown on top of gallium arsenide (GaAs), the new PEC cell is grown upside-down, from top to bottom, resulting in a so-called inverted metamorphic multijunction (IMM) device.

This IMM advancement allowed the NREL researchers to substitute indium gallium arsenide (InGaAs) for the conventional GaAs layers, improving the device efficiency considerably. A second key distinguishing feature of the new advancement was depositing a very thin aluminum indium phosphide (AlInP) "window layer" on top of the device, followed by a second thin layer of GaInP2. These extra layers served both to eliminate defects at the surface that otherwise reduce efficiency and to partially protect the critical underlying layers from the corrosive electrolyte solution that degrades the semiconductor material and limits the lifespan of the PEC cell.

Turner's initial breakthrough created an interesting new way to efficiently split water using sunlight as the only energy input to make renewable hydrogen. Other methods that use sunlight entail additional loss-generating steps. For example: Electricity generated by commercial solar cells can be sent through power conversion systems to an electrolyzer to decompose water into hydrogen and oxygen at an approximate STH efficiency of 12 percent. Turner's direct method set a long-unmatched STH efficiency record of 12.4 percent, which has been surpassed by NREL's new PEC cell.

Before the PEC technology can be commercially viable, the cost of hydrogen production needs to come down to meet DOE's target of less than $2 per kilogram of hydrogen. Continued improvements in cell efficiency and lifetime are needed to meet this target. Further enhanced efficiency would increase the hydrogen production rate per unit area, which decreases hydrogen cost by reducing balance-of-system expenditures. In conjunction with efficiency improvements, durability of the current cell configuration needs to be significantly extended beyond its several hours of operational life to dramatically bring down costs. NREL researchers are actively pursuing methods of increasing the lifespan of the PEC device in addition to further efficiency gains.

While an alternative configuration where the device isn't submerged in acidic electrolyte and instead is wired to an external electrolyzer would solve the durability challenge, a techno-economic analysis commissioned by DOE has shown that submerged devices have the potential to produce hydrogen at a lower cost.

86

EEE / Researchers capture excess photon energy to produce solar fuels

« on: April 22, 2017, 01:47:44 AM »

Scientists at the U.S. Department of Energy's National Renewable Energy Laboratory (NREL) have developed a proof-of-principle photoelectrochemical cell capable of capturing excess photon energy normally lost to generating heat.

Using quantum dots (QD) and a process called Multiple Exciton Generation (MEG), the NREL researchers were able to push the peak external quantum efficiency for hydrogen generation to 114 percent. The advancement could significantly boost the production of hydrogen from sunlight by using the cell to split water at a higher efficiency and lower cost than current photoelectrochemical approaches.

Details of the research are outlined in the Nature Energy paper Multiple exciton generation for photoelectrochemical hydrogen evolution reactions with quantum yields exceeding 100%, co-authored by Matthew Beard, Yong Yan, Ryan Crisp, Jing Gu, Boris Chernomordik, Gregory Pach, Ashley Marshall, and John Turner. All are from NREL; Crisp also is affiliated with the Colorado School of Mines, and Pach and Marshall are affiliated with the University of Colorado, Boulder.

Beard and other NREL scientists in 2011 published a paper in Science that showed for the first time how MEG allowed a solar cell to exceed 100 percent quantum efficiency by producing more electrons in the electrical current than the amount of photons entering the solar cell.

"The major difference here is that we captured that MEG enhancement in a chemical bond rather than just in the electrical current," Beard said. "We demonstrated that the same process that produces extra current in a solar cell can also be applied to produce extra chemical reactions or stored energy in chemical bonds."

The maximum theoretical efficiency of a solar cell is limited by how much photon energy can be converted into usable electrical energy, with photon energy in excess of the semiconductor absorption bandedge lost to heat. The MEG process takes advantages of the additional photon energy to generate more electrons and thus additional chemical or electrical potential, rather than generating heat. QDs, which are spherical semiconductor nanocrystals (2-10 nm in diameter), enhance the MEG process.

In current report, the multiple electrons, or charge carriers, that are generated through the MEG process within the QDs are captured and stored within the chemical bonds of a H2 molecule.

NREL researchers devised a cell based upon a lead sulfide (PbS) QD photoanode. The photoanode involves a layer of PbS quantum dots deposited on top of a titanium dioxide/fluorine-doped tin oxide dielectric stack. The chemical reaction driven by the extra electrons demonstrated a new direction in exploring high-efficiency approaches for solar fuels.

87

EEE / The perfect pattern to trap light

« on: April 22, 2017, 01:47:05 AM »

Superimposing two lattices of similar periods creates structures that researchers can design to control and localize light.

Brighter LEDs and more efficient solar cells are two potential applications for Singapore's Agency for Science, Technology and Research (A*STAR)'s research into lattice structures that can slow or trap light.

Harnessing wave energy by localizing it and suppressing its propagation through a medium is a powerful technique. Now, Alagappin Gandhi and Png Ching Eng Jason from the A*STAR Institute of High Performance Computing have calculated a design that localizes light in tiny loops, within a two-dimensional structure created by merging two lattices of slightly differing periodicities.

The new technique is not limited to light, and may enable the design of systems that can precisely control wave energy in any realm and at any scale -- sound, thermal, water, or even matter waves such as in Bose-Einstein condensates.

For light-based devices the new insights could be used to build more efficient photonic components, said Gandhi.

"If you pattern the surface of an LED with merged lattices it will assist with getting the light out efficiently," said Gandhi. "For a solar cell, however merged lattices will help light to enter better so that more energy can be harvested."

The ability to create resonators in which light is localized on the surface of a device also has applications in quantum computing components based on light, such as defects in diamond.

Gandhi and Png designed the structures by superimposing lattices of small circular dielectric materials with periods in a simple ratio R:R-1 -- for example one lattice is merged with another whose spacing is 4/3 as big, or 5/4, 6/5 etc.

"It creates a two-dimensional effect similar to beats between two waves of very close frequency," Gandhi said. "Where there are antinodes the light is localized in the form of a closed path."

Gandhi said the creation of a regular array of localized loops of light contrasted with Anderson Localization, which arises from randomness in a structure. "This is a systematic way of creating a large number of loops," Gandhi said.

Gandhi and Png ran numerical simulations of the propagation of light in a range of wavelengths slightly below that of the lattice spacing, and calculated the energy band structure. They found that as R increased, there emerged a large number of energy bands whose light had a group velocity of zero, the signature of light localized within the crystal.

Gandhi said merged lattices would also provide a way for researchers to explore topological properties, such as protected edge modes.

The A*STAR-affiliated researchers contributing to this research are from the Institute of High Performance Computing.

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EEE / Adjusting solar panel angles a few times a year makes them more efficient

« on: April 22, 2017, 01:46:20 AM »

With Earth Day approaching, new research from Binghamton University-State of New York could help U.S. residents save more energy, regardless of location, if they adjust the angles of solar panels four to five times a year.

"Regardless of the perks of renewable [energy] resources, there are problems with cost and performance. Solar energy provided by photovoltaic (PV) panels is no exception. One of the solutions is to increase the efficiency of energy generation by tracking the sun," said Shahrokh Akhlaghi, a PhD candidate in the Electrical and Computer Engineering Department at Binghamton University and the co-author of "Study of Sufficient Number of Optimal Tilt Angle Adjustment to Maximize Residential Solar Panels Yield."

Morteza Sarailoo and Hossein Sangrody are both co-authors of the paper and also PhD candidates in the Electrical and Computer Engineering Department. Mandana Rezaeiahari, a PhD candidate in industrial engineering, is also a co-author.

"Adjustments do not coincide with seasonal changes," said Sarailoo. "Our new study shows that four adjustments at optimally divided intervals can provide around 25 kW/m2 more power than adjusting the tilt angle four times a year based on the seasons."

Some residential solar setups increase efficiency with an automated tracking system that constantly adjusts the angle of panels. However, the mechanization adds another layer of cost on an already expensive installation process. If residents want to save a little bit, they can adjust their panels four to five times throughout the year according to the research, which was based on data from the National Renewable Energy Laboratory (NREL) website about nine different locations in the United States. The intervals and angles of the adjustments depend on the geographic location of the panel.

"We were surprised to conclude such a small number of intervals can result in such high performance. We had expected a number 3-4 times larger," Sangrody said.

"The need for only 4-5 adjustments shows that not only is manual adjustment practically possible, but also economical," added Akhlaghi.

The findings were presented at the 2017 Power and Energy Conference at Illinois (PECI).

89

EEE / Remittances to developing countries decline for second straight year: World Bank

« on: April 22, 2017, 01:29:38 AM »

Remittances to developing countries fell for a second consecutive year in 2016, a trend not seen in three decades, according to a report by the World Bank.

Remittances to developing countries fell by 2.4 percent between 2015 and 2016, from $440 billion to $429 billion, according to the latest Migration and Development Brief which was presented at the World Bank’s Spring Meetings on Friday.

Bangladesh, a major receiver of remittances, saw a decline of 11.1 percent in that period, while the South Asian region as a whole saw a 6.4 percent decrease.

The report cites low oil prices and weak growth in Europe, the Russian Federation and the Gulf Cooperation Countries (GCC) as the primary factors responsible for the dip in remittance flows.

Bangladesh’s remittance flows were likely affected by the low oil prices and fiscal tightening in GCC countries, the global lender said.

India, which retained its position as the largest recipient of remittances, saw an 8.9 percent decline, from $68.9 billion in 2015 to $62.7 billion in 2016.

Nepal also saw a contraction of 6.7 percent, but Pakistan saw a modest growth of 2.8 percent.

“Remittances are an important source of income for millions of families in developing countries. As such, a weakening of remittance flows can have a serious impact on the ability of families to get health care, education or proper nutrition,” said Rita Ramalho, Acting Director of the World Bank’s Global Indicators Group.

But, the report says, if global economic forecasts hold true, remittances to developing nations should rise by an estimated 3.3 percent in 2017, with a modest 2 percent increase for the South Asia region.

90

EEE / লেবু পানির গেলাসে বরফ মর্গের নয়তো!

« on: April 20, 2017, 03:31:56 PM »

    মর্গে হয়তো ডাই করে রাখা ছিল এই বরফের চাঁই। কিংবা হিমঘর থেকে কোনও দোকানি কিনে এনেছেন কম দামে। তারপর! রাস্তার ধারে দাঁড়িয়ে রোজ যে পুদিনার সরবতের গেলাসে তৃপ্তির চুমুক দিচ্ছেন, তা তো এই বরফের সৌজন্যেই।  মৃতদেহ সংরক্ষণ, মাছ-সবজির সংরক্ষণে ব্যবহৃত ‘ইন্ডাস্ট্রিয়াল আইস’  শহরজুড়ে৷ ফ্রুট জুস থেকে লেবু পানি হয়ে সেই অপরিশোধিত ক্ষতিকারক পানিই প্রতিদিন ঢুকছে শহরবাসীর শরীরে! কাটাফলের রমরমা রুখতে অভিযানে নেমে এ ছবি দেখে তো কপালে চোখ ওঠার জোগাড় কলকাতা পৌসভার স্বাস্থ্য কর্মকর্তাদের।

যদিও এটাই প্রথমবার নয়। এর আগেও বহুবার পৌরসভার অভিযানে এ ছবি ধরা পড়েছে। সরবত বিক্রেতাদের সতর্কও করা হয়েছিল। কিন্তু সে কথা কে আর কানে তুলেছে! মুখের কথায় যে কাজ হবে না তা বেশ বুঝেছেন স্বাস্থ্য কর্মকর্তারা। তাই এবার আইনের পথে হাঁটতে চান তারা। সরাসরি মামলা ঠুকে এই বরফ ব্যবহার বন্ধ করার বিষয়ে তোড়জোড় শুরু করল কলকাতা পৌরসভা৷

পৌরসভায় স্বাস্থ্যকর্তা বুধবারই বলেছেন, “এর আগে একাধিক দোকানদারকে এই ইন্ডাস্ট্রিয়াল বরফ না ব্যবহার করার জন্য বলা হয়েছিল৷ কিন্তু এদের সিংহভাগই পৌরসভার সেই সতর্কবার্তাকে অবহেলা করেছেন৷ এবার তাই আইনানুগ ব্যবস্থা নেওয়ার কথা ভাবা হচ্ছে৷” বুধবার প্রায় ১২টি দোকানকে শনাক্ত করেছেন পৌরসভার ভেজাল রোধ বিভাগের কর্তারা৷ নষ্ট করা হয়েছে কয়েক টন ইন্ডাস্ট্রিয়াল বরফ৷ তবে ফুটপাথের দোকানদারদের মধ্যে সন্তোষজনক সাড়া মিলেছে বলেই দাবি করেছেন স্বাস্থ্যকর্তারা৷
পৌরসভা সূত্রে খবর, বুধবার নিউমার্কেট চত্বরে একাধিক ফলের রস, আখের রসসহ একাধিক দোকানে অভিযান চালানো হয়৷ ফুটপাতের দোকানও ছিল অভিযানের মধ্যে৷ কিন্তু অভিযান শেষে দেখা গেছে, যাদের দোকান রয়েছে বা যারা ট্রেড লাইসেন্স নিয়ে ব্যবসা করছেন তারাই মূলত এই সস্তার ইন্ডাস্ট্রিয়াল বরফ ব্যবহার করছেন৷ অথচ এর আগে অভিযান চালিয়ে একাধিকবার সতর্ক করে বলা হয়েছে বিশুদ্ধ পানি দিয়ে তৈরি ‘আইস কিউব’ ব্যবহার করতে হবে৷

অভিযান চলাকালীন এক আখের রস বিক্রেতা স্বাস্থ্যকর্তাদের কাছে অভিযোগ করেন, শুধু দোকানদারদের বলে কী হবে? যারা বিক্রি করছে তারা যদি আমাদের এই বরফ দেয় তো কী করব৷

কারা এই বরফ সরবরাহ করছে এদিন তাও খুঁজে বের করেছেন পৌরকর্তারা। হানা দিয়েছেন নিউমার্কেট বাজার, ধর্মতলা ও ময়দান চত্বর এলাকার ইন্ডাস্ট্রিয়াল আইস সরবরাহকারীর ডেরায়। রাস্তার উপরের নোঙরা পরিবেশে থরে থরে সাজানো বরফের চাঁই। সেই চাঁই বস্তায় করে ছড়িয়ে পড়ে গোটা এলাকায়। এদিন বিপুল পরিমাণ বরফ বাজেয়াপ্ত করা হয়েছে।

যেহেতু এই ইন্ডাস্ট্রিয়াল বরফ তৈরিই হয় অপরিশোধিত পানি দিয়ে৷ ফলে এই বরফের পানি থেকে টাইফয়েড, জন্ডিস, পাচনক্রিয়ায় ব্যাঘাত ঘটানোর মতো অসুখ ছড়িয়ে পড়তে পারে৷