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Cells | Green and Alternative Energy Information

Efficient, inexpensive plastic solar cells coming soon

ScienceDaily (Oct. 11, 2010)  Physicists at Rutgers University have discovered new properties in a material that could result in efficient and inexpensive plastic solar cells for pollution-free electricity production.

The discovery, posted online and slated for publication in an upcoming issue of the journal Nature Materials, reveals that energy-carrying particles generated by packets of light can travel on the order of a thousand times farther in organic (carbon-based) semiconductors than scientists previously observed. This boosts scientists’ hopes that solar cells based on this budding technology may one day overtake silicon solar cells in cost and performance, thereby increasing the practicality of solar-generated electricity as an alternate energy source to fossil fuels.

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Building-integrated photovoltaics

Building-integrated photovoltaics (BIPV) are by definition photovoltaic materials that are used to replace conventional building materials. What this means is that photovoltaic materials actually become an integral part of the building, and in most cases they are planned together with the object as its integral part though they can be also built later on.

The global interest in the building integration of photovoltaics is constantly growing, and in the last couple of years BIPV are being increasingly incorporated into the construction of new buildings as a principal or ancillary source of electrical power. Some energy experts even argue that BIPV is currently the fastest growing segment of the photovoltaic industry.

A Building Integrated Photovoltaics (BIPV) system’s main concept consists of integrating photovoltaics modules into the building envelope such as the roof, skylights, or facades. This means that BIPV not only serve as power generator but also as building envelope material, which in the end results in both savings in materials as well as reduced electricity costs.

A complete BIPV system consists of photovoltaic modules, a charge controller, a power storage system, inverter and other power conversion equipment, backup power supply, and different supporting equipment.

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Large photovoltaic solar station to be built in Washington State, U.S.

Via: Renewbl.com

A 75-MW photovoltaic solar Project is to be built in Washington State by Teanaway Solar Reserve (TSR) The permit was issued with a majority vote.

The facility will be located 90 miles east of Seattle, in Kittitas County. “With this decision, Kittitas County is in the forefront of the nation’s new renewable energy industry,” says Howard Trott, TSR’s Managing Director. “TSR’s vision to generate green jobs and energy is now a reality, and it marks the start of a new future for Kittitas County and Washington state.”

Besides generating clean energy, TSR says it will bring more than 200 construction jobs and 35 permanent jobs to an economically depressed community The project will also produce a revenue stream of more than $97 million in purchases of goods and services during construction, and more than $1.5 million annually in property tax revenues to support local schools, roads and hospitals.

Source: Solar Daily

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Graphene: Solar Cells of the Future?

A southern California University team has come up with what could be the alternative new breed of economical and flexible solar cells. For some decades now, organic photovoltaic cells (OPV) have been acclaimed as the new solar cell prototypes and extolled for their light weight, flexible substrates, low cost and easy manufacturability. Research is now being done on them.

Features of OPV cell:
The most unique aspect of the OPV cell devise is the transparent conductive electrode. This allows the light to react with the active materials inside and create the electricity. Now graphene/polymer sheets are used to create thick arrays of flexible OPV cells and they are used to convert solar radiation into electricity providing cheap solar power.

New OPV design:
Now a research team under the guidance of Chongwu Zhou, Professor of Electrical Engineering, USC Viterbi School of Engineering has put forward the theory that the graphene – in its form as atom-thick carbon atom sheets and then attached to very flexible polymer sheets with thermo-plastic layer protection will be incorporated into the OPV cells. By chemical vapour deposition, quality graphene can now be produced in sufficient quantities also.

Differences between silicon cells and graphene OPV cells:
The traditional silicon solar cells are more efficient as 14 watts of power will be generated from 1000 watts of sunlight where as only 1.3 watts of power can be generated from a graphene OPV cell. But these OPV cells more than compensate by having more advantages like physical flexibility and costing less.

More economical in the long run:
According to Gomez De Arco, a team member, it may be one day possible to run printing presses with these economically priced OPVs covering extensive areas very much like printing newspapers. In Gomez’ words

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Breakthrough in Thin-Film Solar Cells

Scientists at Johannes Gutenberg University Mainz (JGU) have come out with positive news about increased efficiency of thin-film solar cells. As we know that scientists are trying to increase the efficiency of the solar cells so that they can be considered as serious alternative to the fossil fuels. Researchers at Johannes Gutenberg University Mainz (JGU) too are working at this angle. They opted for the computer simulations to probe deeper into the indium/gallium combination to increase the efficiency of Copper indium gallium (di)selenide (CIGS) thin-film solar cells. Till now CIGS has shown only about 20% efficiency though theoretically they can attain the efficiency levels of 30%.

Advantages of CIGS:
CIGS cells are cheaper than their counterpart silicon cells due to lower material and fabrication costs resulting in lowered manufacturing costs. CIGS has direct band-gap material therefore they exhibit a very strong light absorption tendency, and only 1-2 micrometers of CIGS is enough to absorb most of the sunlight. Conventional silicon photovoltaic cells are rigid but CIGS cells are flexible. Thin-film solar cells are slowly topping the popularity chart of solar market.

Working on the Efficiency of CIGS: Currently CIGS cells are showing efficiency of around 20%. These cells absorb sunlight through a thin layer made of copper, indium, gallium, selenium, and sulphur. The scientists at Mainz University headed by Professor Dr Claudia Felser are exploiting the computer simulations to find out the properties of CIGS. This research is a part of the comCIGS project. This project is financed by the Federal German Ministry for the Environment, Nature Conservation, and Nuclear Safety (BMU). The researchers are concentrating on the optimum proportion of indium/gallium puzzle. What ratio of indium/gallium would be ideal to increase the efficiency of CIGS? It was discovered earlier that the desired ratio should be 30:70, in practice; the highest efficiency level has been obtained with the exactly opposite ratio of 70:30.

Christian Ludwig who is the member of the Professor Felser’s team worked on the calculations using a hybrid method. This hybrid method included a combination of density functional calculations and Monte Carlo simulations. Dr Thomas Gruhn is the head of the theory group in the Prof. Felser’s team. He says, “Density functional calculations make it possible to assess the energies of local structures from the quantum mechanical point of view. The results can be used to determine temperature effects over wide length scale ranges with the help of Monte-Carlo simulations.”

Homogeneity of the material is the key to high efficiency:
Scientists find out that the indium and gallium atoms are not distributed evenly in the CIGS material; there is a phase when indium and gallium are completely separate. This separation happens at just below room temperature. Researchers also tried out various combinations of temperatures and discovered that the higher the temperature, the more homogeneous the material becomes. The more the lack of homogeneity of the gallium-rich material the lower the efficiency levels of gallium-rich CIGS cells. This phenomenon is discovered for the first time by Prof Felser’s team. The team also discovered a better way to manufacture CIGS solar cells. The research team says if gallium rich material is produced at higher temperatures, the material is notably more homogeneous. For maintaining the homogeneity, the gallium rich material should be cooled down rapidly.

Glass is used as substrate for solar cells. Glass has always restricted process temperatures. But Schott AG has been successful in inventing a special glass with which the process temperature can be increased. Naturally the cells would be more homogeneous. This would lead to the production of cells with a much greater efficiency level. Gruhn says, “We are currently working on large-format solar cells which should outperform conventional cells in terms of efficiency. The prospects look promising.”

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Hybrid Organic Solar Cells Now More Efficient

hybrid organic solar cell Success greets the research team of National Research Council’s National Institute for Nanotechnology (NINT) and the University of Alberta. The plastic solar cells have now an operating life of 8 months instead of mere hours. And they are low-cost, environmentally efficient, unsealed plastic dollar cells – a green energy source. Developing economically viable plastic solar panels and to produce them in large scale has been the long time goal for the scientists as the cost of ultra high-purity silicon used in the traditionally manufactured solar cells is quite prohibitive. These are the solar cells of future – to be available to common man easily. A University of Alberta-NINT team has been focusing on this for quite some time.

Prototype solar cell:
A multi-disciplinary team has been successful in developing a prototype solar panel. It was operating at high capacity for about 10 hours. After that, problems developed within which reduced the efficiency of solar cells. They found that electrode’s chemical coating was the root cause of the problem. For past few months, work has been going on to correct this problem.

Role of electrode:
Producing power from solar cells is the key responsibility of electrodes and the research team found that the unstable chemical coating started leaking around the circuitry of the solar cell and reduced production capacity. They developed a new coating which solved this problem.

New polymer coating:
The team led by David Rider, consisting of Michael J. Brett, Jillian Buriak from U of A-NINT has been successful in developing a durable and longer lasting coating of polymer for the electrode which stopped the chemical leaking that reduced the production capacity. This new polymer coated electrode makes the solar cell work at high capacity continuously.

Success story:
At the time David Rider and colleagues presented their research paper in Advanced Functional Materials on June 22, 2010, the solar prototype cell had performed already for 500 hours at high capacity. In the highly competitive field of plastic solar-cell technology, this research by U of A-NINT team is considered to be a great achievement. And the cell continued to work for 8 months altogether before being damaged in transit between laboratories.

Future:
The future looks bright for hybrid organic solar cells. In Rider’s words “Inexpensive, lightweight plastic solar-cell products, like a blanket or sheet that can be rolled up, will change the solar energy industry”.

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