Alternative energy community amazed by Aidan Dwyer, 13, who came up with notion of arranging solar panels in shape of tree branches to maximize sunlight collection

Nimrod Avraham

Published:
01.16.12, 09:25 / Israel Environment

Aidan Dwyer, a 13-year-old boy from New York, has become the toast of the alternative energy community, after coming up with an inspirational way to enhance solar panels’ reception – arranging them in the shape of tree branches.

According to the Wall Street Journal, Dwyer came up with the idea of arranging solar panels in the shape of trees. After studying the mathematical relationship of the arrangement of leaves and branches on trees and the Fibonacci Sequence – which starts with the numbers 0 and 1, followed by the sum of the prior two numbers in the sequence – he realized that Fibonacci numbers can be found in many plants and flowers in nature. 

He then conducted several photovoltaic array experiments comparing his design to standard solar panel arrays, and found it was 20%-30% more efficient in collecting sunlight.

According to the report, the design “used the greatest number of PV panels within the least amount of physical space, making his concept a truly practical and efficient design.”

Innovation aside, Dwyer’s calculation were disproved after experts reviewed them more carefully and discovered he measured volts instead of the watts, but that has not stopped the alternative energy community from hailing his original thought process and experiments.

He was also awarded the 2011 Young Naturalist Award by the American Museum of Natural History in New York, and has filed a provisional patent application for his research on collecting solar energy.

‘Born-again Zionist’ revolutionizing solar energy field

Professor David Faiman of Israel’s National Solar Energy Center is dedicated to ensuring the country’s ‘energy independence’.

By David Sheen, October 7, 2011

A scientist who immigrated from the U.K. and became one of Israel’s top solar-power researchers is spearheading efforts to push the country into a new age. Prof. David Faiman, the director of Israel’s National Solar Energy Center at Sde Boker, says the government must immediately invest in major solar energy infrastructure projects, coupled with a public relations push to convince the populace of their necessity.
Faiman moved to Israel right before the Yom Kippur war and says the subsequent Arab oil boycotts convinced him the country must embrace alternative energy, specifically that drawn from the sun, which he has spent the last decades of his career working to harness.
Faiman believes Israel is far from reaching its goal of 10 percent energy from renewable sources by 2020, and called the recent inauguration of a five megaWatt solar field at Kibbutz Ketura a drop in the bucket compared to the country’s swiftly developing energy needs.

A professor of physics at Ben-Gurion University’s Blaustein Institutes for Desert Research and chair of the Department of Solar Energy and Environmental Physics, Faiman has one solution, curved solar panels that minimize the economic and environmental cost of producing solar power, one of the biggest barriers to the field’s development.
Recently, Kvutzat Yavneh, a kibbutz east of Ashdod, adopted a new solar technology inspired by Faiman’s ideas. This year, the technology was exported to South Korea, and next year there are plans to ship the panels to Italy and China. The improved panels promise higher energy yields, reduced land use, lower per-unit costs and less environmental damage.

Faiman was born in Amersham, a small town outside of London, as German bombs were being dropped on British cities during World War II. He says he always wanted to be a successful physicist and attained physics degrees in the U.K. and the U.S., crowned by a post-doctorate at Oxford University. But at the same time, Faiman, who grew up in a Zionist home, says he kept looking toward Israel.
"I feel extremely privileged to have been born at a time and in a place that have enabled me to be part of a Jewish nation with a state of its own," he said.
Although Faiman had long pondered immigrating, it was his star-cross’d encounter with an Israeli actress performing a run in England with the Royal Shakespeare Company that sealed the deal for him.
That woman, Ofra, became his wife, and Faiman accompanied her back to Israel, just shy of 30, on the eve of the Yom Kippur War. Ofra went on to act and direct in Israel, while raising the couple’s three children.

Faiman specialized in nuclear physics and worked for CERN – the European Organization for Nuclear Research, before immigrating to Israel to work with the Weizmann Institute.

But the Arab oil embargo that followed the Yom Kippur War jolted Faiman into rethinking his research in light of national needs.

"I did a lot of soul-searching as to what would be the most useful way I could use my scientific training. The subsequent oil crisis and Ben-Gurion University’s decision to establish the Blaustein Institute helped me crystallize my scientific future," says Faiman. "At Sde Boker, I became a born-again ‘Ziontist’."

Today, Faiman is at the forefront of developing the next generation of renewable energy systems, certain that Israel must turn to solar solutions. "I like to think that our grandchildren will find it hard to believe that we lived in a world in which electricity was not generated mainly from solar energy," says Faiman. "Just as my own grandfather, who was born in Russia in 1872, once expressed amazement to me that most people no longer know how to ride a horse."

Faiman is concerned about the effects that the country’s consumption and population growth rates will have on Israel’s energy requirements and its announced target of ten per cent renewables by 2020. "This straight line that has been rising for last 20 years at a rate close to two billion kiloWatt hours per year, reached 60 billion last year. What that means is, ten years from now, in the year 2020, we are going to be at close to 80 billion," says Faiman.
The ten per cent goal, out of a projected total of 80 billion, is eight billion, and with ten years to arrive at that figure, that would mean mandating an annual increase of 0.8 billion kiloWatt hours produced per year. "0.8 every year means something like 400 megaWatts of installed capacity. Nobody ever built a 400 megaWatt photovoltaic plant anywhere in the world. Nobody ever built even a 100 megawatt plant! So we actually have to build photovoltaic plants every year at four to five times the largest plant that’s ever been built," says Faiman. "That’s the meaning of ten per cent renewables."
The main reason that solar technologies have not yet been adopted en masse, in Israel and around the world, is that up until now the cost of producing electricity using solar panels has exceeded the cost of producing electricity by burning fossil fuels. Faiman and his colleagues hit upon a novel method for reducing panel production costs: separating the two functions of collecting energy and converting energy.

Although collection surfaces must be large, in order to catch as many solar rays as possible, Faiman realized that the "wafers" which convert these solar rays into electricity needn’t be. By bending the panel into a parabolic dish and re-focusing all the sun’s rays onto a small receiver only one-thousandth the size of the dish, Faiman’s model minimizes the size of the most economically and ecologically expensive component of the panel.
Ordinarily, focusing so much solar energy onto a such a small area would burn the solar converter, rendering it useless. But Faiman hit upon another idea to turn that liability into an advantage. By running water or some other liquid over the solar converter, the radiated surfaces are cooled down to manageable levels. The heat energy absorbed by that liquid is then transferred to water stored in large tanks, making it unnecessary to use electricity or burn fossil fuels to heat running water.
At the program’s pilot project at Kvutzat Yavneh, water pumped from the panels into a 5000 gallon storage system actually exceeds 80 degrees Celsius and needs to be cooled significantly before it can even be pumped into kibbutz members’ homes for domestic comsumption.
Since 2009, Israeli company Zenith Solar has been making Faiman’s ideas a physical reality, assembling the solar panel kits in a Kiryat Gat factory. Company co-founder and CEO Roy Segev says that by using the CHP technology – which stands for ‘combined heat and power’ – the panels are able to reach efficiencies of over 70%, as opposed to conventional PV panels, which record efficiencies of only between 10 and 15 per cent.
In addition to harvesting much more energy from a smaller space, which preserves precious land resources, Segev says that far less landfill is produced from their waste.
"The majority of the materials here are mirrors, plastic, metals, etc," says Segev. "They are 99% recyclable." Most importantly for most people, the CHP panels will soon be able to produce energy at parity with conventional energy sources, says Segev. "If we get these machines at mass production – not millions of machines, but rather at a rate of 500 to 1000 units a month – they would generate energy at less than 10 cents U.S. per kiloWatt hour."
Despite the impressive performance of Zenith’s panels and the contracts they’ve signed with buyers abroad, the Israeli government has yet to invest in a large-scale solar power production plant, using CHP or any other technology. "It would be very nice if we were to back a local industry, rather than imported industry," says Faiman, but he stresses that Israel’s solar energy needs are so great that there is plenty of business to go around. "I don’t want to put the importers out of business. On the contrary, I want to give them so much business, they’ll have money coming out of their ears."
In the current economic climate, it may prove difficult to convince government officials to invest in long term renewable energy infrastructure for the country. It may take a public education campaign to create a shift in consciousness and a groundswell of support for Faiman’s plan. "We pay taxes, and out of our taxes, things which are perceived as being the common good are paid for, such as roads and schools and defense, you name it, all of the things that enable life to be tolerable," says Faiman. "If energy independence were to be considered a public good or a national strategic priority, then it could be paid for with our taxes."

More on this topic

• Jews make strong showing among 2011 Nobel Prize winners

This story is by:
• David Sheen

David R. Baker, Chronicle Staff Writer

Saturday, June 25, 2011

A lot of sunlight hits tall office buildings, only to go to waste.

Their relatively small roofs don’t offer much space for solar panels. A solar array crammed onto the top of a typical office tower could produce, at best, a tiny fraction of the electricity the building and its tenants need.

But what if the building’s windows could serve as solar panels?

Pythagoras Solar in San Mateo has developed a window laced with solar cells, a window that generates and saves electricity at the same time.

Thin horizontal rows of silicon cells embedded between dual panes of glass catch light from above. And through a trick of optics, the window blocks direct sunlight from entering the building, cutting the amount of power needed for air conditioning.

"Instead of heating the room, the light generates clean solar power," said Gonen Fink, chief executive officer of Pythagoras. "It’s relatively simple and straightforward optics. The challenge is making everything work together."

The window works well enough that earlier this week, Pythagoras won an award from the "GE ecomagination Challenge," an effort by General Electric Co. and several venture capital firms to find and fund promising technologies. Pythagoras was one of five companies given an "innovation award," which comes with a $100,000 grant.

Not a lot of money, to be sure. For Fink, the award’s true value lies in the recognition from GE, a company deeply familiar with all manner of energy technologies. Pythagoras has raised $11 million in capital from investors, including Evergreen Venture Partners.

"Mostly for us it’s a validation of three things – that (the window) is unique, that it’s feasible and it could have a big impact," he said.

The Pythagoras window belongs to a class of solar equipment known as BIPV – building-integrated photovoltaics. Other companies have marketed solar window awnings and photovoltaic roofing tiles.

"If you look at all the different parts of the building, from the pavement to the panels that make up the exterior to the windows – everything that receives sunlight is a potential solar collector," said Joel Makower, chairman of the GreenBiz Group, a media company focused on sustainable businesses. "And there’s a tremendous amount of work, some of it in the lab and a little bit in the market, that’s trying to tap into this."

Makower argues that the technologies for buildings, energy, data and vehicles are starting to blend together, a phenomenon GreenBiz calls "Verge." Buildings won’t simply be consumers of energy – they’ll be producers as well.

"We’re definitely looking at buildings as net generators of electricity, at least during some parts of the day," he said.

Other companies are designing their own versions of solar windows. New Energy Technologies Inc., for example, is testing a way to generate electricity using a transparent chemical coating sprayed on glass.

The solar cells Pythagoras uses aren’t transparent. Instead, they look like open venetian blinds. They capture about 14 percent of the sunlight’s energy.

Fink won’t reveal the system’s cost per watt. But the company estimates that for a typical customer, the windows will pay for themselves within three to five years. Pythagoras already installed some of the windows at Chicago’s Willis Tower, formerly known as the Sears Tower.

"The most important thing for us is the impact this could have," Fink said. "This could change the way buildings are being built."

E-mail David R. Baker at dbaker@sfchronicle.com.

http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2011/06/25/BUHP1K2FGD.DTL

This article appeared on page D – 1 of the San Francisco Chronicle

under News June 6th, 2011 by IFandP Newsroom

Arava Power unveiled Israel’s first commercial solar power plant on Sunday.

The ILS100m (US$30m) plant is located in the agricultural community of Kibbutz Keturah and its 4.95MW capacity will be linked to the national grid in the next few weeks.

In addition, the company announced plans to build about 50 other solar array fields, which could represent an investment of up to US$2bn. “Arava plans to build nearly 50 solar fields for well over 400 megawatts, an investment cost of roughly $2 billion,” David Rosenblatt, the company’s vice chairman, told Reuters. The arrays will be build throughout the Negev desert and come online by the end of 2014.

The venture will be backed up by Germany’s Siemens and Arava is confident about the funding. Siemens Israel President Eliezer Tokman said Siemens “certainly sees Israel as a country with high potential for solar energy”. He said the business model was attractive because of the relatively secure income, which will come from the state-owned Israel Electric Corp (IEC). IEC will pay ILS1.52 (US$0.45)/kWh over 20 years although when the large units are brought onstream, this price could drop to ILS1.08. 

While agreements with communities and Bedouin families in the Negev have been signed, the company still needs the government to increase its official quota on solar fields. While the Infrastructure Ministry has given the go-ahead, the Finance Ministry requires a few more details to be clarified. However, a senior official at the Infrastructure Ministry expects the issue to be resolved soon while Arava envisages the quota to be raised by the end of the month.

Source: Industrial Fuels and Power

by Energy Matters, December 27, 2010

Israeli Prime Minister Benjamin Netanyahu has delivered a welcome end of year gift to his nation’s solar industry: cutting through bureaucratic red tape hampering the construction of solar farms.
The commitment will help the Holy Land achieve its stated goal of generating 10 percent of electricity from renewable energy sources by 2020.

Although committing to the 10 percent target in 2009, and with a five percent midway target by 2014, Israel has been slow to make real progress on the solar front – so far less than half of one percent of its total energy supply comes from renewables, despite possessing some of the most promising solar real estate in the form of sun-drenched hills and desert landscape.
Prime Minister Netanyahu said that under the solar plan, permits would be issued allowing solar panel arrays to be placed on the roofs and sides of buildings and other designated structures. The plan also allows for the preparation of detailed plans for the construction of photovoltaic units on areas of up to 750 dunams (a Middle-East measurement: roughly 40 paces in length and breadth) in size. 
The plan would also allow for solar farms to be built on and around sensitive cultural areas and heritage sites, including the Gaza strip, as well as on limited agricultural lands. For a nation with limited resources like Israel, which relies on nuclear for much of its energy needs, solar makes sense according to Netanyahu.

"Ours is a sun-drenched country,” he said. “Europe has snowstorms and we have sun. Similarly, ours is a technology-rich country, including in solar technology . . . the paradox is that when we try to join our technology with the sun, we cannot make progress due to our bureaucracy. Today’s decision simplifies this bureaucracy so that we will be able to enjoy our relative advantage, without harming the environment."

Press Release, Tel Aviv University,  April 21, 2010

TAU demonstrates that UV light can zap unwanted "life" in your drinking water and save taxpayer dollars

Does your drinking water smell foul, or are you worried that chemicals might be damaging your family’s health? Water treatment facilities currently use chlorine that produces carcinogenic by-products to keep your tapwater clean, but Tel Aviv University scientists have determined that ultra-violet (UV) light might be a better solution.

Dr. Hadas Mamane of Tel Aviv University‘s Porter School of Environmental Science and Faculty of Engineering, Prof. Eliora Ron of TAU’s George S. Wise Faculty of Life Sciences and their doctoral student Anat Lakretz of TAU’s School of Mechanical Engineering have recently determined the optimal UV wavelength for keeping water clean of microorganisms. Their approach could be used by water treatment plants as well as large-scale desalination facilities to destroy health-threatening microorganisms and make these facilities more efficient.

"UV light irradiation is being increasingly applied as a primary process for water disinfection," says Lakretz. "In our recent study, we’ve shown how this treatment can be optimized to kill free-swimming bacteria in the water — the kinds that also stick inside water distribution pipes and clog filters in desalination plants by producing bacterial biofilms."

This undesired "stickiness" of bacteria to surfaces is called "bio-fouling," which costs taxpayers and governments billions of dollars each year. "No one should be drinking microorganisms in their water. In addition, when microorganisms get stuck in the pores of the membranes of filters, they create serious problems," says Lakretz.

Not all UV light is created equal

Dr. Hadas Mamane

Irradiation could be used as a pre-treatment to inactivate suspended microorganisms in water, with the secondary goal of preventing bio-fouling. In their study, reported in the journal Biofouling, the researchers looked at targeted UV light wavelengths on the bacteria Pseudomonas aeruginosa, commonly found in drinking water.

The TAU researchers investigated UV wavelengths within between the 220-280 nanometre (nm) scale, and found that any wavelength between 254 and 270 nm effectively cleaned the water. Those in the same region were also best for keeping membranes clear of bacterial build-up in desalination plants, they reported. Special lamps that emit a multi-wavelength UV spectrum — more advanced than the single-wavelength UV lamps found in home water systems — were used.

The UV "zap" also prevented bacterial re-growth in the water after UV inactivation. "The best way to control and kill these micro-organisms was to damage their DNA," says Lakretz. "The damage that the UV light causes has no known negative effect on the water," she adds.

In addition, the prevention of biofilm formation by bacteria was UV dose-dependent. The researchers reported less bio-fouling when a bigger dose of UV light was applied to the water around the film.

A light to save lives

Anat Lakretz

The approach is even more helpful against parasites that aren’t adversely affected by chlorine treatment, such as Giarrdia and Cryptosporidium, two harmful parasites that cause severe diarrhea and can lead to death. Children, the elderly and those in developing nations are particularly vulnerable. "Sewage leakage into water supplies poses a big problem in terms of bacterial contamination, and is something UV light could remediate," says Lakretz.

Small amounts of chorine or other oxidants will still be necessary to make sure that residual bacteria don’t enter the water further along the distribution pipeline. But Lakretz says this new approach to disinfecting water while controlling biofouling can also reduce the amount of carcinogenic by-products that chlorine produces.

The Tel Aviv University team is part of the MAGNET consortium, an Israeli research-oriented project aimed at researching and commercializing “clean” technologies.

Merging science and Jewish thought

By Abigail Klein Leichman, Israel 21C 
April 21, 2010

He may be an impressive innovator in solar energy, and a captain of industry, but Arnold Goldman is also a thinker whose unusual goal is to bring science together with philosophy.

Builder of Jerusalem – solar energy leader Arnold Goldman.

Serious philosophers rarely make good businessmen. But solar energy innovator Arnold J. Goldman is no navel-gazer. Goldman heads Jerusalem-based BrightSource Industries and its California-based parent, BrightSource Energy, which is contracted to deliver more than 2,600 megawatts of solar electricity in California using new technology demonstrated at Goldman’s Solar Energy Development Center in the Negev, the largest solar energy facility in the Middle East.

Goldman, 67, was named a "Builder of Jerusalem" by Jerusalem-based educational institution Aish Hatorah, which also acknowledged his early role in founding solar energy pioneer Luz International; subsidiary Luz Industries Israel; and Electric Fuel Corporation, a vehicle battery developer.

Ever since the Rhode Island native was 16 and living in the San Fernando Valley he has been seeking higher truths in the beauty of mathematics, he tells ISRAEL21c. Later, Goldman’s search broadened to embrace Jewish thought.

"From the age of 14 I had worked at an assortment of odd jobs when I had time, including stretching springs across couches," Goldman remembers. "The summer I was 16, I was selling mops. I woke up one night feeling miserable and came to the conclusion that if I had to work most of my life, at least I wanted it to be valuable."

Meshing knowledge with real-world achievements

His future wife, Karen Fried, urged him to channel his intellectual curiosity away from academics into what he now defines as "Jewish thinking" – meshing pure knowledge with measurable real-world achievements. After earning a bachelor’s degree at the University of California-Los Angeles in engineering with a minor in philosophy and economics, and a master’s in computer science at the University of Southern California, Goldman went into business.

"I was trying to get into lines of work that I thought would expand my knowledge base so that I could gain a big enough comprehension of how reality worked," Goldman recounts. "I decided that computers and communications were a focal point for integrating thoughts into places where they could be processed. I wanted to start a business and learn how to put together groups of people."

Goldman first spent five years in computer development in the military industry. He was an innovator in the use of integrated circuits on projects such as the Minuteman rocket system (the Minuteman is a land-based intercontinental ballistic missile designed to attack ground targets), and then moved to defense contractor Litton Industries, where he tackled assignments for its subsidiary, Royal Typewriter.

Gathering a group of scientists from the California Institute of Technology and Xerox, in 1972 he started Lexitron, the United States’ first word processing company. "I felt if you could make electronics simple, people would do it," Goldman tells ISRAEL21c.

Through it all, the thinker kept attending philosophy classes and began writing a book, A Working Paper on Project Luz, which provided the philosophical basis for Luz International.

An irresistible coincidence

At a night class in 1976, a Catholic priest recommended the works of Jewish medieval scholar-physician-philosopher Maimonides. Two weeks later, an aunt Goldman hadn’t seen for 20 years sent him a brochure about a class on Maimonides being offered at LA’s University of Judaism. It proved to be an irresistible coincidence.

"Karen and I went, and it was the first time I found a philosopher in whose stream I belonged," says Goldman. "I found out I had been doing ‘Jewish thinking’ all along."

As his book-in-progress assumed a Jewish flavor, the family relocated to Israel, planning to stay for two years so that Goldman could finish it there. They never left. The concept of Luz – the biblical locale of Jacob’s dream ladder connecting heaven and earth – fuelled Goldman’s "need to create an environment to integrate science and consciousness." And that environment was a community that used solar energy.

The community didn’t pan out as well as its solar energy aspect did, "But I discovered that the company itself was a community," Goldman recounts. Luz Industries grew to employ 500 people in Israel and thousands in California, where between 1984 and 1990 it installed nine solar power stations in the Mojave Desert, accounting for 90 percent of the world’s solar energy generation.

However, because of the large land mass required for equipment that captures the sun’s heat and turns it into electricity-generating steam, Luz’s coffers ran dry when its property-tax exemption expired in California.

Goldman poured his energies into a new book, Moving Jewish Thought to the Center of Modern Science, and founded several small companies to explore how linguistic dynamics integrate consciousness into physics. "I was interested in the play between speech, thought and language, and quantifying their impact on that which is created."

Israelis can "bury their ego in the objective"

The effects of the 1997 Kyoto Protocols on clean energy combined with rising fossil-fuel prices provided the opportunity for Goldman to resurrect Luz. "Utility companies and investment bankers in California were willing to talk to me, so we were able to deal with very creative ideas for a next-generation system," explains Goldman, who holds numerous patents and is the recipient of international prizes such as the International Solar Energy Society Achievement through Action Award. "No big system in the world had ever before produced more energy than it consumed."

Luz II, a wholly owned subsidiary of BrightSource, handles research, development, logistics and project engineering for the advanced solar-thermal technology of BrightSource plants in Europe and the US. Though it may seem illogical to base his business in Israel, Goldman says he could not have accomplished what he did elsewhere.

"I was trying to do something broad and complex, and it’s hard for people to get their mind around all the elements. Israelis are intellectually curious and have experience in so many areas and that allowed us to put in place a big multidisciplinary conversation and build a learning model based on my specifications in something like six months. It would have taken three or four years in the States. Israelis show incredible dedication and are able to bury their ego in the objective," he says.

Goldman, the father of five and grandfather of 10, takes a serious interest not only in Aish HaTorah – whose founder, Rabbi Noach Weinberg, was a fan of his writings – but also in the Jerusalem College of Technology, where he is a member of the international board of governors. ‘I am looking into doing ecological education within a Jewishly rich curriculum," he declares. "I want to put together Jewish thought and science."

Source: Israel 21C

enlarge

This is a schematic diagram of the light-trapping elements used to optimize absorption within a polymer-embedded silicon wire array. (Credit: Caltech/Michael Kelzenberg)

ScienceDaily (Feb. 17, 2010) — Using arrays of long, thin silicon wires embedded in a polymer substrate, a team of scientists from the California Institute of Technology (Caltech) has created a new type of flexible solar cell that enhances the absorption of sunlight and efficiently converts its photons into electrons. The solar cell does all this using only a fraction of the expensive semiconductor materials required by conventional solar cells.

“These solar cells have, for the first time, surpassed the conventional light-trapping limit for absorbing materials,” says Harry Atwater, Howard Hughes Professor, professor of applied physics and materials science, and director of Caltech’s Resnick Institute, which focuses on sustainability research.

The light-trapping limit of a material refers to how much sunlight it is able to absorb. The silicon-wire arrays absorb up to 96 percent of incident sunlight at a single wavelength and 85 percent of total collectible sunlight. “We’ve surpassed previous optical microstructures developed to trap light,” he says.

Atwater and his colleagues — including Nathan Lewis, the George L. Argyros Professor and professor of chemistry at Caltech, and graduate student Michael Kelzenberg — assessed the performance of these arrays in a paper appearing in the February 14 advance online edition of the journal Nature Materials.

Atwater notes that the solar cells’ enhanced absorption is “useful absorption.”

“Many materials can absorb light quite well but not generate electricity — like, for instance, black paint,” he explains. “What’s most important in a solar cell is whether that absorption leads to the creation of charge carriers.”

The silicon wire arrays created by Atwater and his colleagues are able to convert between 90 and 100 percent of the photons they absorb into electrons — in technical terms, the wires have a near-perfect internal quantum efficiency. “High absorption plus good conversion makes for a high-quality solar cell,” says Atwater. “It’s an important advance.”

The key to the success of these solar cells is their silicon wires, each of which, says Atwater, “is independently a high-efficiency, high-quality solar cell.” When brought together in an array, however, they’re even more effective, because they interact to increase the cell’s ability to absorb light.

“Light comes into each wire, and a portion is absorbed and another portion scatters. The collective scattering interactions between the wires makes the array very absorbing,” he says.

This effect occurs despite the sparseness of the wires in the array — they cover only between 2 and 10 percent of the cell’s surface area.

“When we first considered silicon wire-array solar cells, we assumed that sunlight would be wasted on the space between wires,” explains Kelzenberg. “So our initial plan was to grow the wires as close together as possible. But when we started quantifying their absorption, we realized that more light could be absorbed than predicted by the wire-packing fraction alone. By developing light-trapping techniques for relatively sparse wire arrays, not only did we achieve suitable absorption, we also demonstrated effective optical concentration — an exciting prospect for further enhancing the efficiency of silicon-wire-array solar cells.”

Each wire measures between 30 and 100 microns in length and only 1 micron in diameter. “The entire thickness of the array is the length of the wire,” notes Atwater. “But in terms of area or volume, just 2 percent of it is silicon, and 98 percent is polymer.”

In other words, while these arrays have the thickness of a conventional crystalline solar cell, their volume is equivalent to that of a two-micron-thick film.

Since the silicon material is an expensive component of a conventional solar cell, a cell that requires just one-fiftieth of the amount of this semiconductor will be much cheaper to produce.

The composite nature of these solar cells, Atwater adds, means that they are also flexible. “Having these be complete flexible sheets of material ends up being important,” he says, “because flexible thin films can be manufactured in a roll-to-roll process, an inherently lower-cost process than one that involves brittle wafers, like those used to make conventional solar cells.”

Atwater, Lewis, and their colleagues had earlier demonstrated that it was possible to create these innovative solar cells. “They were visually striking,” says Atwater. “But it wasn’t until now that we could show that they are both highly efficient at carrier collection and highly absorbing.”

The next steps, Atwater says, are to increase the operating voltage and the overall size of the solar cell. “The structures we’ve made are square centimeters in size,” he explains. “We’re now scaling up to make cells that will be hundreds of square centimeters — the size of a normal cell.”

Atwater says that the team is already “on its way” to showing that large-area cells work just as well as these smaller versions.

Their research was supported by BP and the Energy Frontier Research Center program of the Department of Energy, and made use of facilities supported by the Center for Science and Engineering of Materials, a National Science Foundation Materials Research Science and Engineering Center at Caltech. In addition, Boettcher received fellowship support from the Kavli Neuroscience Institute at Caltech.

Adapted from materials provided by California Institute of Technology.

1. Kelzenberg et al. Enhanced absorption and carrier collection in Si wire arrays for photovoltaic applications. Nature Materials, 2010; DOI: 10.1038/nmat2635

TAU’s nanosized “forest of peptides” can be used as the basis for self-cleaning windows and more efficient batteries.

ScienceDaily (Dec. 4, 2009) — A coating on windows or solar panels that repels grime and dirt? Expanded battery storage capacities for the next electric car? New Tel Aviv University research, just published in Nature Nanotechnology, details a breakthrough in assembling peptides at the nano-scale level that could make these futuristic visions come true in just a few years.

Operating in the range of 100 nanometers (roughly one-billionth of a meter) and even smaller, graduate student Lihi Adler-Abramovich and a team working under Prof. Ehud Gazit in TAU’s Department of Molecular Microbiology and Biotechnology have found a novel way to control the atoms and molecules of peptides so that they “grow” to resemble small forests of grass. These “peptide forests” repel dust and water — a perfect self-cleaning coating for windows or solar panels which, when dirty, become far less efficient.

“This is beautiful and protean research,” says Adler-Abramovich, a Ph.D. candidate. “It began as an attempt to find a new cure for Alzheimer’s disease. To our surprise, it also had implications for electric cars, solar energy and construction.”

As cheap as the sweetener in your soda

A world leader in nanotechnology research, Prof. Gazit has been developing arrays of self-assembling peptides made from proteins for the past six years. His lab, in collaboration with a group led by Prof. Gil Rosenman of TAU’s Faculty of Engineering, has been working on new applications for this basic science for the last two years.

Using a variety of peptides, which are as simple and inexpensive to produce as the artificial sweetener aspartame, the researchers create their “self-assembled nano-tubules” in a vacuum under high temperatures. These nano-tubules can withstand extreme heat and are resistant to water.

“We are not manufacturing the actual material but developing a basic-science technology that could lead to self-cleaning windows and more efficient energy storage devices in just a few years,” says Adler-Abramovich. “As scientists, we focus on pure research. Thanks to Prof. Gazit’s work on beta amyloid proteins, we were able to develop a technique that enables short peptides to ‘self-assemble,’ forming an entirely new kind of coating which is also a super-capacitor.”

As a capacitor with unusually high energy density, the nano-tech material could give existing electric batteries a boost — necessary to start an electric car, go up a hill, or pass other cars and trucks on the highway. One of the limitations of the electric car is thrust, and the team thinks their research could lead to a solution to this difficult problem.

“Our technology may lead to a storage material with a high density,” says Adler-Abramovich. “This is important when you need to generate a lot of energy in a short period of time. It could also be incorporated into today’s lithium batteries,” she adds.

Window Cleaner a thing of the past?

Coated with the new material, the sealed outer windows of skyscrapers may never need to be washed again — the TAU lab’s material can repel rainwater, as well as the dust and dirt it carries. The efficiency of solar energy panels could be improved as well, as a rain shower would pull away any dust that might have accumulated on the panels. It means saving money on maintenance and cleaning, which is especially a problem in dusty deserts, where most solar farms are installed today.

The lab has already been approached to develop its coating technology commercially. And Prof. Gazit has a contract with drug mega-developer Merck to continue his work on short peptides for the treatment of Alzheimer’s disease — as he had originally foreseen.

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Adapted from materials provided by American Friends of Tel Aviv University.