December 4, 2013 | Leave a Comment
A Max Planck Institute for Solid State Research in Stuttgart, Germany has a group that can claim high efficiency thermionic conversion of heat energy. The heat source could be light from the sun, heat from burned fossil fuels, nuclear or any of the fuel sources that yield energy with heat.
Because of its thermionic energy’s promise, researchers have been trying for more than half a century to develop a practical generator, with little progress. The progress might leap forward thanks to a new design called a “thermoelectronic” generator. The new design has been described in AIP Publishing’s Journal of Renewable and Sustainable Energy.
Thermionic generators use the temperature difference between a hot and a cold metallic plate to create electricity.
Jochen Mannhart, an experimental solid-state physicist and the lead author of the JRSE paper, explains, “Electrons are evaporated or kicked out by light from the hot plate, then driven to the cold plate, where they condense.” The resulting charge difference between the two plates yields a voltage that, in turn, drives an electric current, “without moving mechanical parts,” he said.
Previous models of thermionic generators have proven ineffectual because of what is known as the “space-charge problem,” in which the negative charges of the cloud of electrons leaving the hot plate repel other electrons from leaving it too, effectively killing the current.
Mannhart, along with his former students Stefan Meir and Cyril Stephanos, and colleague Theodore Geballe of Stanford University, circumvented this problem using an electric field to pull the charge cloud away from the hot plate, which allowed electrons to fly to the cold plate.
Now for the encouragement, Mannhart explains, “Practical thermionic generators have reached efficiencies of about 10%. The theoretical predictions for our thermoelectronic generators reach about 40%, although this is theory only. We would be much surprised if there was a commercial application in the marketplace within the next five years, but if companies that are hungry for power recognize the potential of the generators, the development might be faster.”
Mannhart might be a little glum with his commercial prediction. With the developed countries economies in such doldrums and the willingness to invest in new ideas very slow, he could be right.
On the other hand the race to 40% efficiency would be a serious game changer. Depending on the economics of working units at industrial scale production – 40% is very competitive indeed. Used as a secondary recovery after a primary use the efficiency gains and fuel savings would be very impressive.
Your humble writer would encourage the Mannhart and Max Planck team to stay the course; the results could be very useful and beneficial across the entire world economy.
December 3, 2013 | Leave a Comment
University of Oregon (UO) scientists developed a new method called “dual-electrode photoelectrochemistry” to gain a new insight into the chemistry of splitting water. Their first result is an important and overlooked parameter, the ion-permeability of electrocatalysts used in water-splitting devices.
Shannon W. Boettcher, professor of chemistry and head of the Solar Materials and Electrochemistry Laboratory in the UO’s Materials Science Institute explained the discovery could help replace a trial-and-error approach to paring electrocatalysts with semiconductors with an efficient method for using sunlight to separate hydrogen and oxygen from water to generate renewable energy.
Solar water-splitting cells, which mimics photosynthesis, requires at least two different types of materials: a semiconductor that absorbs sunlight and generates excited electrons and an electrocatalyst, typically a very thin film of a metal oxide that contains elements such as nickel, iron and oxygen, which serves to accelerate the rate at which electrons move on and off water molecules that are getting split into hydrogen and oxygen.
Boettcher continues, “We developed a new way to study the flow of electrons at the interface between semiconductors and electrocatalysts. We fabricated devices which have separate metal contacts to the semiconductor and electrocatalyst.”
Here’s where the development really gets interesting. Lead paper author Fuding Lin, a postdoctoral researcher, developed the new method by electrically contacting a single-crystal of semiconducting titanium dioxide and coated it with various electrocatalyst films. A film of gold only 10 nanometers thick was used to electrically contact the top of the electrocatalysts. Both contacts were used as probes to independently monitor and control the voltage and current at semiconductor-electrocatalyst junctions with a device known as a bipotentiostat. Lin focused on oxygen-evolution reaction – the most difficult and inefficient step in the water-splitting process.
“This experiment allowed us to watch charge accumulate in the catalyst and change the catalyst’s voltage,” Boettcher said.
Lin explained that a thin layer of ion-porous electrocatalyst material works best, because the properties of the interface with the semiconductor adapt during operation as the charges excited by sunlight flow from the semiconductor onto the catalyst.
The research was designed to understand how maximum energy might be extracted from excited electrons in a semiconductor when the electrons enter the catalyst, where a chemical reaction separates oxygen and hydrogen. To date, Lin said, researchers have been experimenting with materials for creating efficient and cost-effective devices, but minimizing the energy loss associated with the catalyst-semiconductor interface has been a major hurdle.
In the study, Lin compared the movement of electrons between semiconductors coated with porous nickel oxyhydroxide – a film previously shown by Boettcher’s lab to yield excellent electrocatalytic efficiency for separating oxygen from water – with semiconductors modified with non-permeable films of iridium oxide.
“The ion porous material allows water and ions to permeate the catalyst material,” Lin said. “When these catalysts are in solution the catalyst’s energy can move up and down as its oxidation state changes.”
Catalysts with non-porous structures in semiconductor-catalytic junctions don’t show this behavior and typically don’t work as well, said Boettcher.
Converting sunlight into energy and storing it for later use in an economically viable way is a major challenge in the quest to replace fossil fuels with renewable energy. Traditional solar photovoltaic cells absorb sunlight to form excited electrons that are funneled into wires as electricity but storing energy as electricity, for example in batteries, is expensive.
Details about how excited electrons move from semiconductors to catalysts have been poorly understood, Boettcher said. “This lack of understanding makes improving water-splitting devices difficult, as researchers have been relying on trial-and-error instead of rational design.”
The system used in the study, Boettcher added, was not efficient. “That wasn’t our goal,” he said. “We wanted to understand what’s happening at a basic level with well-defined materials. This will facilitate the design of systems that are more efficient using other materials.”
Kimberly Andrews Espy, vice president for research and innovation and dean of the UO Graduate School added a bit of global view to the press release saying, “This important discovery by Dr. Boettcher and his team could lead to more efficient systems that help foster a sustainable future. Researchers at the University of Oregon are reengineering the science, manufacturing and business processes related to critical products.”
Espy might not grasp the full implications that Boettcher and Lin have revealed. Back up a few paragraphs where it’s noted, “-minimizing the energy loss associated with the catalyst-semiconductor interface has been a major hurdle-“. The UO researchers have developed something much further reaching in the field of catalysts that will over time have impressive results beyond water splitting going on to fuel cells and very likely other applications.
Andrea Rossi, founder, leader, and technology driver at Leonardo Corporation has opened the ECAT LENR device’s web site where pre-orders can be made. For those concerned about the risks, there isn’t a provision for funding, entering personal financial details or entering other revealing personal details. One simply gets a place on the list. Its kind of like “take a number” at a retail establishment.
For now the pre-order will only move to an order on the process heat 1 mega watt unit. That would be due to the commercial nature, the ability to control liability, involve more high temperature experienced personnel, and get rolling sooner. The home sized unit is some ways off, more in a moment.
The 1 MW unit contains 106 smaller ECAT units mounted in a shipping container. A valve for topping off the hydrogen is on the front of each unit, together with an electrical connection to the immersion heater used to start the reaction. Each ECAT 1 MW unit is constructed inside an international standardized 20 foot container that can easily be moved using different modes of transportation as with ships, air cargo, trains and trucks.
Each 1 MW unit consists of small parallel modules. Each reactor module contains three cores and consumes small amounts of treated nickel powder and hydrogen gas running under a pressure of approximately 15 bar. The plant is to be recharged by specially trained and certified personnel.
Of note, Mr. Rossi is still being quite careful. Potential customers must comply with several criteria set by Leonardo Corporation in order to qualify for a purchase of an ECAT 1MW plant. Don’t think you’ll be sneaking up on anything either, as pre-orders will be subjected to a routine due-diligence process.
The ECAT for homes is also a heat unit, not an electrical supplier. An ECAT would provide hot water and space heating plus other heat needs like swimming pools, hot tubs and even driveway clearing. More uses are sure to come up when heat gets really low cost.
The home sized model is being rigidly tested for certification and regulation procedures. Just where that process began and where it might lead and finally end is very much an unknown. Cold Fusion, or LENR or ECAT: all are new and for many a frightening idea. One can be certain that every bureaucracy at every level is going to bedevil the progress.
On the plus side Mr. Rossi has set up an inquiry field on the home unit page that will load your contact information. Interestingly, the first entry is a choice of buyer, investment, reseller, online affiliate, technology license, third party application, press and other. There is a lot of room here, perhaps even some career opportunity.
The first impression of your humble writer is Mr. Rossi has raised his level of professionalism for the market. No money allowed, it looks as if both sides of a deal will get full assurances and an opportunity for due diligence. Before long one would expect one or more running units for inspections. For all the miss steps early in the public domain, Andrea Rossi has admirably stepped up his game. Congratulations on that are in order with a bit of thanks as well.
That makes for quite a Thanksgiving Day. Should all the barriers to come in regulations, permitting and government interference be overcome, and Mr. Rossi make a commitment to start at an achievable price point both for the company’s growth as well as mass consumer acceptance this week is a historical milestone.
For now the conclusive “It Works!” hasn’t been heard, and that cry may not be an ‘event’ in the coming months. So for today let’s give thanks for the ingenuity of mankind, the foresight and persistence of one and the promise of great hope for an energized future available to almost everyone.
Your humble writer thanks you and everyone else who stopped by over the past year.
Have a great day today.
Releasing hydrogen from water via solar energy into storable fuel remains one of the greatest challenges of modern chemistry. One of the ways chemists have tried to capture the energy of the sun is through water splitting, in which the atoms of H2O are broken apart so the hydrogen may be collected and used as fuel. Plants do this naturally through photosynthesis, and for half a century, scientists have tried to recreate that process by tinkering with chemical catalysts powered by sunlight.
For example indium tin oxide (ITO) is one material scientists have commonly tried to use. Researchers prefer it for its transparency – which allows sunlight to pass through and trigger the water-splitting reactions – and its ability to conduct electricity. But ITO is far from an ideal material.
Ben Wiley, assistant professor of chemistry at Duke University explains, “Indium is not very abundant. It is similar in abundance to silver in the earth’s crust.” As a result, solar fuel cells using ITO will likely remain expensive and uncompetitive with conventional energy sources like coal and natural gas, he said.
Wiley’s lab has created something they hope can replace ITO: copper nanowires fused in a see-through film. The team – including two postdoctoral researchers, a graduate student, and a former graduate student from Duke – published their new approach last month in the chemistry journal Angewandte Chemie.
Copper is 1000 times more plentiful and 100 times less expensive than indium. Copper nanowire catalysts also cost less to produce than their ITO counterparts because they can be “printed” on pieces of glass or plastic in a liquid ink form, using a machine that functions much like a printing press. ITO production, by contrast, requires large, sequential chambers of pumps and vacuums that deposit a thin layer of indium atoms at a far slower rate.
The copper nanowire films consist of networks of microscopic metal rods, the properties and applications of which Wiley’s lab has studied for years. The nanowires provide a high surface area for catalyzing chemistry, and Wiley’s team experimented with coating them in either cobalt or nickel – metals that serve as the actual chemical catalyst. Even with a coat of cobalt or nickel, the nanowire films allow nearly seven times more sunlight to pass through than ITO. The films are also flexible, leading Wiley to imagine the completed fuel production cells one day being attached to backpacks or cars.
In the meantime, engineering and chemistry challenges remain. The nanowire films carry out only one half of the water-splitting equation, a process called water oxidation. The other half of the reaction involves using the electrons obtained from water oxidation to reduce water to hydrogen. Wiley’s team expects to publish their work on this process in the coming year.
Wiley said, “A lot of groups are working on putting together complete devices to generate fuels from sunlight, but the efficiencies and costs of these systems have to be improved for them to get to commercial [production].”
Wiley noted that solar energy production is just one application of the copper nanowire films they study. The nanowires also show promise for use in flexible touch screens, organic LED (or OLED) lights and smart glass.
This is progress. The copper nanowire has been an item of interest for three or four years with no commercial applications making news. The applications for the copper nanowire are very wide indeed and the potential beyond harvesting sunlight to make fuel extends into the tools and devices we use. Copper nanowire is an extremely high potential field and it’s gratifying to see the field widen further.
Now for a commercial application that has a big impact – it can’t be far off now.
Zuobin Wang of Changchun University of Science and Technology (China), Jin Zhang of Xi’an Technological University (China) and colleagues at Cardiff University (UK), who are partners of the EU FP7 LaserNaMi project, have devised an approach to lithography, the process used to “print” microelectronic circuits, that allows them to add a pattern to the surface of a solar cell.
There are two obvious problems with photovoltaic solar panels. First, they are very shiny and so a lot of the incident sunlight is simply reflected back into the sky rather than being converted into electricity. Secondly, they get dirty with dust and debris caught from the wind and residues left behind by dust, smoke, soot, rain and birds.
Most owners of solar panels must wash them frequently, a chore many hadn’t considered at purchase.
The new process suggests that high-power, self-cleaning solar panels might be coming to market soon.
The features of the lithographed pattern are so small that individual parts are shorter than the wavelength of light. That means the incident sunlight becomes trapped rather than reflected thus passing on more of its energy to electricity-generation process that takes place within the panel.
The same pattern also makes the surface of the solar cell behave like the surface of a lotus leaf, a natural material that is known to be very water repellant, or hydrophobic, so that particles and liquids that land on it do not become stuck as there is no surface to which the droplets can grip. When it rains any deposits are sloughed away and the rainwater runs off efficiently leaving the panel clean and dry after the downpour.
The team’s work indicates that a patterned layer on top of the active part of the panel can avoid the energy losses due to reflection from the surface. It directly boosts absorption of sunlight in the visible spectrum and into the near-infrared part of the spectrum, all of which contributes to a boost to the overall electrical efficiency of the panel.
The team suggests that printing the surface of the photovoltaic cell so that it is covered with nanoscopic cones would provide the optimal combination of making the panel non-reflective and hydrophobic and so self-cleaning.
It all sounds quite good. The effort in some locations to keep the panels clean and working up to rated efficiency is a considerable effort. There remains the need for the occasional downpour, but a rinse would be much easier and less costly than a full detergent clean and rinse procedure.
One assumes that most folks and policy makers and bureaucrats and have little if any or simply no experience in solar panel operations. Its commonly assumed that the systems are mount and forget, which could be the case in an ever-reducing efficiency kind of way.
The facts are quite different making the news of the improved surfaces a very welcome innovation indeed. Lets hope the scale up to industrial production goes smoothly and quickly.
The work might be quite interesting to manufactures as there are no graphics to be found showing the details of the concept – or – these schools haven’t caught on to the public relations effect that good news and information work can aid in gathering the best students, faculty and funding as well as commercial interest.
For now wizened buyers might want to add the efforts and costs of cleaning and the added efficiency in the calculations for having a solar panel set installed. We might never hear of any progress until a manufacturer touts the improvement on a new product introduction.
November 21, 2013 | Leave a Comment
Dr. Armin Wedel, head of division at the Fraunhofer Institute for Applied Polymer Research (IAP) in Potsdam-Golm believes time is slowly running out for bulky television sets, boxy neon signs and the square-edged backlit displays we all know from shops and airports.
It won’t be long before families gathering together to watch television at home will be calling out: “Unroll the screen, dear, the film’s about to start!” And members of the public may soon encounter screens everywhere they go, as almost any surface can be made into a display.
Wedel has good grounds for the expectation. The first curved screens were on display at this year’s consumer electronics trade show (IFA) in Berlin. The technology behind it all is flexible organic light emitting diodes (OLEDs). “These may just be ideas at the moment, but they have every chance of becoming reality,” Wedel said.
What’re coming are flickering façades, curved monitors, flashing clothing, fluorescent wallpaper, flexible solar cells – and all printable. This is no make-believe vision of the future; it will soon be possible using a new printing process for organic light-emitting diodes.
According to Wedel the potential offered by this technology extends beyond screens and displays for consumer electronics, according. He believes OLEDs are also ideally suited for all kinds of lighting and for digital signage applications – that is to say, advertising and information systems such as electronic posters, advertisements, large image projections, road signs and traffic management systems.
The Fraunhofer scientists worked together with mechanical engineering company MBRAUN to develop a production facility able to create OLEDs as well as organic solar cells on an industrial scale. The innovative part is that it is now possible to print OLEDs and solar cells from solutions containing luminescent organic molecules and absorptive molecules respectively, which makes printing them onto a carrier film very straightforward. Usually, printing them involves vaporizing small molecules in a high vacuum, making it a very expensive process.
Previously scientists used various printing technologies to design components on a laboratory scale. They can now produce larger sample series – and this is particularly advantageous for the applications that the IAP has in mind, as large illuminated surfaces and information systems require tailored solutions produced in relatively small numbers. “We’re now able to produce organic components under close-to-real-life manufacturing conditions with relative ease. Now for the first time it will be possible to translate new ideas into commercial products,” Wedel says.
At the heart of the pilot plant is a robot that controls different printers that basically act like an inkjet printing system. OLEDs are applied to the carrier material one layer at a time using a variety of starting materials. This produces a very homogenous surface that creates a perfect lighting layer. “We’re able to service upscale niche markets by offering tailored solutions, as we can apply the organic electronic system to customers’ specifications, just like in digital printing,” explains Wedel.
Industry experts estimate that printed OLEDs pose the promise of becoming a billion-dollar market. “The focus in Germany and Europe is on OLED lighting because this is the home market for large companies such as Osram and Philips,” explains Wedel. “The manufacturing facility will help secure competitive advantages in this particular segment of the market. It strengthens the German research community, and also demonstrates the capabilities of German plant engineering,” says Dr. Martin Reinelt, CEO of MBRAUN in Garching.
OLEDs have several advantages over conventional display technologies. Unlike liquid crystal displays they do not require backlighting, which means they consume less energy. Because the diodes themselves emit colored light, contrast and color reproduction are better. The electroluminescent displays also offer a large viewing angle of almost 180 degrees. And because they require no backlighting, they can be very thin, making it possible to create entirely new shapes.
There are still several challenges to be met before OLEDs become firmly established on the market. “The main hurdle, as far as I’m concerned, is the high level of investment required to set up manufacturing,” says Wedel. This is why, at least where lighting is concerned, he expects OLEDs to complement rather than replace conventional lighting devices. His view of where OLED production technology could head is less modest: “My vision is that the day will come when all we need do is switch ink cartridges in our printers in order to print out our own lighting devices.”
Wedel is probably right that the technology is coming, and likely faster and soon that he might think. There is no reason to think that the Japanese, Chinese and other Asian tiger economies are not working at the technology too. Research activity in the U.S hasn’t completely stopped.
Perhaps the German companies can get a head start, and that others will vigorously pursue their lead.
Stanford University and Department of Energy Researchers have made the first battery electrode that heals itself, opening a new and potentially commercially viable path for making the next generation of lithium ion batteries. The development is a stretchy polymer that coats the electrode, binds it together and spontaneously heals tiny cracks that develop during battery operation.
Stanford Professor Zhenan Bao, whose lab is where the development took place, said, “We found that silicon electrodes lasted 10 times longer when coated with the self-healing polymer, which repaired any cracks within just a few hours.”
Chao Wang, a postdoctoral researcher at Stanford and one of two principal authors of the paper explains, “Self-healing is very important for the survival and long lifetimes of animals and plants. We want to incorporate this feature into lithium ion batteries so they will have a long lifetime as well.”
Professor Bao’s group has been working on flexible electronic skin for use in robots, sensors, prosthetic limbs and other applications. For the battery project Chao added tiny nanoparticles of carbon to the polymer so it would conduct electricity.
Yi Cui, an associate professor at SLAC and Stanford who led the research with Bao reported the electrodes worked for about 100 charge-discharge cycles without significantly losing their energy storage capacity. “That’s still quite a way from the goal of about 500 cycles for cell phones and 3,000 cycles for an electric vehicle,” Cui said, “but the promise is there, and from all our data it looks like it’s working. Their capacity for storing energy is in the practical range now, but we would certainly like to push that.”
Researchers worldwide are racing to find ways to store more energy in the negative electrodes of lithium ion batteries to achieve higher performance while reducing weight. One of the most promising electrode materials is silicon; it has a high capacity for soaking up lithium ions from the battery fluid during charging and then releasing them when the battery is put to work.
But this high capacity comes at a price: Silicon electrodes swell to three times normal size and shrink back down again each time the battery charges and discharges, and the brittle material soon cracks and falls apart, degrading battery performance. This is a problem for all electrodes in high-capacity batteries, said Hui Wu, a former Stanford postdoc who is now a faculty member at Tsinghua University in Beijing, the other principal author of the paper.
To make the self-healing coating, scientists deliberately weakened some of the chemical bonds within polymers – long, chain-like molecules with many identical units. The resulting material breaks easily, but the broken ends are chemically drawn to each other and quickly link up again, mimicking the process that allows biological molecules such as DNA to assemble, rearrange and break down.
Researchers in Cui’s lab and elsewhere have tested a number of ways to keep silicon electrodes intact and improve their performance. Some are being explored for commercial uses, but many involve exotic materials and fabrication techniques that are challenging to scale up for production.
The self-healing electrode, which is made from silicon microparticles that are widely used in the semiconductor and solar cell industry, is the first solution that seems to offer a practical road forward, Cui said. The researchers said they think this approach could work for other electrode materials as well, and they will continue to refine the technique to improve the silicon electrode’s performance and longevity.
The development is quite promising. The silicon electrode has a
potential that has tantalized battery researchers for years. It’s quite interesting that the first generation of the coating is at 100 charging cycles, an impressive feat all on its own.
The genius of the idea is now out where others can apply their innovations on a now proven concept. Lithium ion batteries are now certain to greatly improve.
November 19, 2013 | Leave a Comment
Researchers at the Cambridge Cavendish Laboratory and Mons have investigated a process in which the initial photonic electronic excitation can split into a pair of half-energy excitations. The phenomenon can happen in certain organic molecules when the quantum mechanical effect of electron spin sets the initial spin ‘singlet’ state to be double the energy of the alternative spin ‘triplet’ arrangement.
When a photon is absorbed it creates a single electronic excitation that is then separated into an electron and a positively charged hole, irrespective of the light energy. One way to improve efficiency is to split energy available from visible photons into two, a kind of fission that leads to a doubling of the current in the solar cell.
Solar cells offer the opportunity to harvest abundant, renewable energy. Although the highest energy light occurs in the ultraviolet and visible spectrum, most solar energy is in the infrared. There is a trade-off in harvesting this light, so that solar cells are efficient in the infrared but waste much of the energy available from the more energetic photons in the visible part of the spectrum.
The group’s study paper has been published in the journal Nature Chemistry where the team reports that the process of singlet fission to pairs of triplets depends very sensitively on the interactions between molecules. By studying this process when the molecules are in solution it is possible to control when this process is switched on.
When the active material in the solution is very dilute, the distance between molecules is large and singlet fission does not occur. When the solution is concentrated, collisions between molecules become more frequent. The researchers found that the fission process happens as soon as just two of these molecules are in contact, and remarkably, that singlet fission is then completely efficient – so that every photon produces two triplets.
This fundamental study provides new insights into the process of singlet fission and demonstrates that the use of singlet fission is a very promising route to improved solar cells. Chemists will be able to use the results to make new materials, said the team from Cambridge’s Cavendish Laboratory, who are currently working on ways to use these solutions in devices.
Dr. Brian Walker, a research fellow in the Cavendish Lab’s Optoelectronics group, who led the study explained saying, “We began by going back to fundamentals; looking at the solar energy challenge from a blue skies perspective. Singlet fission offers a route to boosting solar cell efficiency using low-cost materials. We are only beginning to understand how this process works, and as we learn more we expect improvements in the technology to follow.”
The team used a combination of laser experiments, which measure timings with extreme accuracy, with chemical methods used to study reaction mechanisms. This dual approach allowed the researchers to slow down the fission and observe a key intermediate step never before seen.
“Very few other groups in the world have laser apparatus as versatile as ours in Cambridge,” added Andrew Musser, a researcher who collaborated in the study. “This enabled us to get a step closer to working out exactly how singlet fission occurs.”
The news suggests a new breakthrough in solar energy harvesting, but may be a furthering of the electron spin research that may well be the basis for this new development. So far the research is in the lab using lasers. We’ll keep an eye out for a cell built to work in the sunlight.
The Brit’s idea could be a means to circumvent the Shockley–Queisser limit in single-junction solar cells. The main problem for now is the conversion of the energy in the collector to an electrical output. It will be interesting to see just how efficient the new cell can be in the sunshine.