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Someday, solar panels may be light and cheap enough that they could be hung on a clothesline, thanks to a synthetic mineral called perovskite. Physicist Sam Stranks explains the solar-powered science and the challenges that stand in its way.
Solar power is key to our energy future. But the solar industry is butting up against one hard problem: Silicon cells are not very efficient at converting sunlight into electricity — at best, about 29 percent efficient. You may wonder, Why does efficiency even matter, when sunlight is free? The answer: because low efficiency means you need to install a whole lot of solar panels — which can be large, heavy and expensive to manufacture — to generate enough energy to make a dent in your needs.
But that could change thanks to a mineral called perovskite, according to Cambridge University physicist (and TED Fellow) Sam Stranks. He and his colleagues at Swift Solar are working to develop perovskite-based solar panels that could break the energy-efficiency upper limit.
What in the world is perovskite? The term “perovskite” refers to two substances: a calcium titanium oxide mineral composed of calcium titanate, and also the class of compounds that share the mineral’s unique crystal structure. The perovskites that hold such promising photovoltaic (PV), or solar energy-generating, properties are a group of human-made versions discovered in 2009 by Japanese scientist Tsutomu Miyasaka and colleagues. (Miyasaka was talked about in 2018 as a potential Nobel Prize recipient.) “These perovskites can absorb sunlight better than silicon,” says Stranks. “We can absorb almost all of the sunlight with a perovskite film that is at least a hundred times thinner than silicon.”
Scientists synthesize perovskites by mixing two inexpensive salts, lead halides and organic halides. This solution forms an ink, which can be applied in an ultrafine, uniform layer by using inkjet printing or spin coating. “The film deposited is very thin — around 500 nanometers or about 1/100th the thickness of a human hair — and it is enough to absorb a large fraction of the sunlight needed to generate electricity,” says Stranks.
The upshot: A little perovskite can generate a lot of power. “The state of California requires 50 gigawatts of power, for example,” says Stranks, “and to make enough solar panels, you’d only need half an Olympic swimming pool’s worth of perovskite ink.”
Another plus: A perovskite cell factory could be a lot less expensive than a silicon factory. While a silicon factory costs roughly $300 million to $400 million to build, a perovskite factory could cost less than $100 million. “The difference in expense is partly because making highly crystalline silicon requires heating it to a very high temperature to get rid of defects,” says Stranks. “Perovskite films, on the other hand, only need gentle heating to be defect-free, and they can be rolled out rapidly on big printers, which is more cost-effective.”
While perovskite probably won’t replace silicon cells right away (to learn why, read on), the two compounds can work together. “It’s not an either/or proposition with silicon, but both/and,” says Stranks. Perovskite cells can be layered over existing silicon solar cells — in a “tandem” cell — to raise their efficiency. Boosting silicon with perovskite could make each PV panel 20 percent more efficient than today’s PV panels, contends Stranks. The increase in efficiency has effects that could ripple out through the solar-energy process. He explains, “If you’re installing a house that would’ve previously needed five panels, you now only need four. That changes things a lot: the panels for a solar farm would suddenly be 20 percent less expensive, as well as other cost savings, and so on.”
Here’s how a tandem cell works. The job of a solar cell is to harvest the various wavelengths of light — which are perceived as different colors — in the visible spectrum and convert them into energy. “When you layer a perovskite cell on top of a silicon cell, the perovskite layer harvests the bluer light, which is the highest-energy visible light, and converts it into voltage,” says Stranks. “The rest of the light then travels through to the silicon cell below, which absorbs the redder, lower-energy rays and converts those into power. The idea is that, with both layers, you’re harvesting almost the entire spectrum of light, but you’re doing it sequentially to maximize the amount of power produced.”
Why not get rid of silicon altogether and just use perovskite? That’s the goal, says Stranks. Perovskite-perovskite tandem cells — a concept first demonstrated by his cofounders Giles Eperon and Tomas Leijtens — are a technology being developed by the team at Swift Solar. Two different types of perovskite cells are placed on top of each other, and just as tandem perovskite-silicon cells harvest different frequencies of light, so do tandem perovskite-perovskite cells. These could potentially push the efficiency up to 35 percent or higher.
Why silicon still matters: We don’t know how long a perovskite cell lasts. “Silicon cells last 25 years, while perovskite cells have yet to be sufficiently proven under such environmental stressors as moisture and heat,” says Stranks. (Remember, the material was only discovered in 2009.) Why this matters: If you’re installing an expensive solar array on your house, you want it to last for a while. Stranks is optimistic that perovskite cells can be made durable, perhaps by optimizing the compositions and the cell designs. Meanwhile, tandem perovskite cells can start to be used in devices like drones that don’t require long-term durability.
Perovskites could bring power to new customers in new forms. Stranks envisions perovskite cells providing power someday in rural areas in developing countries. While silicon panels are already being installed and used in all kinds of settings, they can be heavy and bulky. “My idea would be to roll off these cheap solar sheets, fill a truck with them to be used in remote communities. The sheets could be hung on a clothesline, installed on the roof of a shelter, and so on,” he explains. “A typical sheet, deployed with a storage battery, could power a mobile phone charger, lamps or a small refrigerator.” According to Stranks’s best guess, it may take up to a decade before perovskites reaches consumers’ lives. “We’ve still got work to do, and it will take a global push to realize the full potential of perovskites,” he says. “But given the price of cheap, clean energy, the future is bright.”
I was revolted by a picture I saw on Facebook. A father holding a baby and both were
horribly scarred by a machete. The baby had a terrible scar on its face which broke my
heart and all I could think of was what cold blooded human maniacs could perpetrate
such atrocities? I understand how this is a Holiday season in Europe and North America
but to allow this sort of cruelty to exist in Africa and precisely in the Democratic Republic of the
Congo, or D.R.C., is a crime against humanity and degrades all of us as human beings!
I ask the United Nations to create an armed peace force and to send it to the D.R.C. to help
put an end to this ongoing atrocity.
I ask all peace loving governments on this planet not to turn their backs on innocent men
and women and children who are victims of cold blooded killers.
Thanks for reading.
Nelson Joseph Raglione.
NASA Astronaut, Crewmates Return to Earth After 197-Day Mission in Space
Expedition 57 crew members Sergey Prokopyev of the Russian space agency Roscosmos, Serena Auñón-Chancellor of NASA, and Alexander Gerst of ESA (European Space Agency) emerge one at a time from the Soyuz MS-09 that carried them home from the International Space Station Dec. 20, 2018, after a 197-day mission. The spacecraft touched down in Kazakhstan at 12:02 a.m. EST, marking the end of a voyage that took them around the globe 3,152 times, covering 83.3 million miles.
Credits: NASA Television
Three members of the International Space Station’s Expedition 57 crew, including NASA astronaut Serena Auñón-Chancellor, returned to Earth Thursday, safely landing at 12:02 a.m. EST (11:02 a.m. local time) in Kazakhstan.
Auñón-Chancellor and her crewmates, Expedition 57 Commander Alexander Gerst of ESA (European Space Agency) and Soyuz Commander Sergey Prokopyev, launched June 6 and arrived at the space station two days later to begin their mission. Over 197 days, they circled the globe 3,152 times, covering 83.3 million miles.
For the last 16 days of her mission, Auñón-Chancellor was joined by fellow NASA astronaut Anne McClain, marking the first time in which the only two U.S. astronauts on a mission both were women.
Serena Auñón-Chancellor of NASA rests in a chair after she, Alexander Gerst of the European Space Agency, and Sergey Prokopyev of Roscosmo, landed in their Soyuz MS-09 capsule in a remote area near the town of Zhezkazgan, Kazakhstan on Dec. 20, 2018. Auñón-Chancellor, Gerst, and Prokopyev are returning after 197 days in space where they served as members of the Expedition 56 and 57 crews onboard the International Space Station.
Credits: NASA/Bill Ingalls
The Expedition 57 crew contributed to hundreds of experiments in biology, biotechnology, physical science and Earth science aboard the world-class orbiting laboratory. Highlights included investigations into new cancer treatment methods and algae growth in space. The crew also installed a new Life Sciences Glovebox, a sealed work area for life science and technology investigations that can accommodate two astronauts.
This was the first flight for Auñón-Chancellor and Prokopyev and the second for Gerst, who – with a total of 362 days in orbit – now holds the flight duration record among ESA astronauts.
Prokopyev completed two spacewalks totaling 15 hours and 31 minutes. During a 7 hour, 45 minute spacewalk Dec. 11, he and Oleg Kononenko of Roscosmos retrieved patch samples and took digital images of a repair made to the habitation module of the Soyuz MS-09 in which the Expedition 57 trio rode home. The space station crew located and, within hours of its detection, repaired a small hole inside the Soyuz in August. The spacecraft was thoroughly checked and deemed safe for return to Earth.
When the Soyuz undocked at 8:40 p.m. Dec. 19, Expedition 58 began aboard the station, with McClain, David Saint-Jacques of the Canadian Space Agency, and Kononenko comprising a three-person crew. The next residents on the space station – Nick Hague and Christina Koch of NASA and Alexey Ovchinin of Roscosmos – will launch Feb. 28 from the Baikonur Cosmodrome in Kazakhstan to join their crewmates, marking the start of Expedition 59.
For more than 18 years, humans have lived and worked continuously aboard the station, advancing scientific knowledge and demonstrating new technologies, making research breakthroughs not possible on Earth that will enable long-duration human and robotic exploration into deep space. A global endeavor, more than 230 people from 18 countries have visited the unique microgravity laboratory that has hosted more than 2,400 research investigations from researchers in more than 103 countries.
Keep up with the International Space Station, its research and crews at:
I am keenly aware of the tremendous personal honor involved in my having been chosen to be a member of the Army Special Attack Corps, which is considered to be the most elite attack force in the service of our glorious fatherland.
My thoughts about all these things derive from a logical standpoint which is more or less the fruit of my long career as a student and, perhaps, what some others might call a liberal. But I believe that the ultimate triumph of liberty is altogether obvious. As the Italian philosopher Benedetto Croce has proclaimed, “liberty is so quintessential to human nature that it is absolutely impossible to destroy it. “I believe along with him that this is a simple fact, a fact so certain that liberty must of necessity continue its underground life even when it appears, on the surface, to be suppressed—it will always win through in the end.
It is equally inevitable that an authoritarian and totalitarian nation, however much it may flourish temporarily, will eventually be defeated. In the present war we can see how this latter truth is borne out in the Axis Powers themselves. What more needs to be said about Fascist Italy? Nazi Germany too has already been defeated, and we see that all the authoritarian nations are now falling down one by one, exactly like buildings with faulty foundations. All these developments only serve to reveal all over again the universality of the truth that history has so often proven in the past: men’s great love of liberty will live on into the future and into eternity itself.
Although there are aspects to all this which constitute something the fatherland has reason to feel apprehensive about, it is still a truly wonderful thing to feel that one’s own personal beliefs have been validated. On every front, I believe that ideologies are at the bottom of all the fighting that is going on nowadays. Still further, I am firmly convinced that the outcome of each and every conflict is predictable on the bases of the ideologies held by the opposing sides.
My ambitious hope was to have lived to see my beloved fatherland—Japan—develop into a great empire like Great Britain in the past, but that hope has already been dashed. If those people who truly loved their country had been given a fair hearing, I do not believe that Japan would be in its present perilous position. This was my ideal and what I dreamt about: that the people of Japan might walk proudly anywhere in the world.
In a real sense it is certainly true that a pilot in our special aerial attack force is, as a friend of mine has said, nothing more than a piece of the machine. He is nothing more than that part of the machine which holds the plane’s controls—endowed with no personal qualities, no emotions, certainly with no rationality—simply just an iron filament tucked inside a magnet itself designed to be sucked into an enemy air-craft carrier. The whole business would, within any context of rational behavior, appear to be unthinkable, and would seem to have no appeal whatsoever except to someone with a suicidal disposition. I suppose this entire range of phenomena is best seen as something peculiar to Japan, a nation of spirituality. So then we who are nothing more than pieces of machinery may have no right to say anything, but we only wish, ask, and hope for one thing: that all the Japanese people might combine to make our beloved country the greatest nation possible.
Were I to face the battles that lie ahead in this sort of emotional state, my death would be rendered meaningless. This is the reason then, as I have already stated, that I intend to concentrate on the honor involved in being designated a member of the Special Attack Corps.
When I am in a plane perhaps I am nothing more than just a piece of the machine, but as soon as I am on the ground again I find that I am a complete human being after all, complete with human emotions—and passions too. when the sweetheart whom I loved so much passed away, I experienced a kind of spiritual death myself. Death in itself is nothing when you look upon it, as I do, as merely a pass to the heaven where I will see her once again, the one who is waiting there for me.
Tomorrow we attack. It may be that my genuine feelings are extreme—and extremely private! But I have put them down as honestly as I can. Please forgive me for writing so loosely and without much logical order. Tomorrow one believer in liberty and liberalism will leave this world behind. His withdrawing figure may have a lonely look about it, but I assure you that his heart is filled with contentment.
I have said everything I wanted to say in the way I wanted to say it. Please accept my apologies for any breach of etiquette. Well,then.
—Captain Ryoji Uehara
Uehara was killed during an attack on the US Fleet at the Battle of Okinawa, May 11th, 1945. He was 22 years old. Among his personal effects was a book on philosophy by Benedetto Croce, in the cover of which he had written,
“Goodbye, my beloved Kyoko-chan. I loved you so much;but even then you were already engaged, so it was very painful for me.Thinking only of your happiness,I suppressed the urge to whisper into your ear. That I loved you. I love you still.”
Apollo 11 was the spaceflight that landed the first two people on the Moon. Commander Neil Armstrong and Lunar Module Pilot Buzz Aldrin, both American, landed the lunar module Eagle on July 20, 1969, at 20:17 UTC. Armstrong became the first person to step onto the lunar surface six hours after landing on July 21 at 02:56:15 UTC; Aldrin joined him about 20 minutes later. They spent about two and a quarter hours together outside the spacecraft, and collected 47.5 pounds (21.5 kg) of lunar material to bring back to Earth. Command Module Pilot Michael Collins piloted the command module Columbia alone in lunar orbit while they were on the Moon's surface. Armstrong and Aldrin spent 21.5 hours on the lunar surface before rejoining Columbia in lunar orbit. Apollo 11 was launched by a Saturn V rocket from Kennedy Space Center on Merritt Island, Florida, on July 16 at 13:32 UTC, and was the fifth crewed mission of NASA's Apollo program. The Apollo spacecraft had three parts: a command module (CM) with a cabin for the three astronauts, and the only part that returned to Earth; a service module (SM), which supported the command module with propulsion, electrical power, oxygen, and water; and a lunar module (LM) that had two stages – a descent stage for landing on the Moon, and an ascent stage to place the astronauts back into lunar orbit. After being sent to the Moon by the Saturn V's third stage, the astronauts separated the spacecraft from it and traveled for three days until they entered lunar orbit. Armstrong and Aldrin then moved into Eagle and landed in the Sea of Tranquillity. The astronauts used Eagle's ascent stage to lift off from the lunar surface and rejoin Collins in the command module. They jettisoned Eagle before they performed the maneuvers that blasted them out of lunar orbit on a trajectory back to Earth. They returned to Earth and splashed down in the Pacific Ocean on July 24 after more than eight days in space. Armstrong's first step onto the lunar surface was broadcast on live TV to a worldwide audience. He described the event as "one small step for [a] man, one giant leap for mankind." Apollo 11 effectively ended the Space Race and fulfilled a national goal proposed in 1961 by President John F. Kennedy: "before this decade is out, of landing a man on the Moon and returning him safely to the Earth." mewe.com/i/francemichaud_knapp
https://www.youtube.com/watch?v=VckmK-ZCpAU Grouch Marx at his best! Gut wrenching funny! There is only one problem and that is you need to be at least Seventy Plus to understand all the subtle jokes and sexual innuendos.
