December 21, 2009
By: Admin
Category: Solar Cells
Glitter-sized Solar Photovoltaics Produce Competitive Results
Adventures in microsolar supported by microelectronics and MEMS techniques
Representative thin crystalline-silicon photovoltaic cells – these are from 14 to 20 micrometers thick and 0.25 to 1 millimeter across.
Sandia National Laboratories scientists have developed tiny glitter-sized photovoltaic cells that could revolutionize the way solar energy is collected and used.
The tiny cells could turn a person into a walking solar battery charger if they were fastened to flexible substrates molded around unusual shapes, such as clothing.
The solar particles, fabricated of crystalline silicon, hold the potential for a variety of new applications. They are expected eventually to be less expensive and have greater efficiencies than current photovoltaic collectors that are pieced together with 6-inch- square solar wafers.
The cells are fabricated using microelectronic and microelectromechanical systems (MEMS) techniques common to today’s electronic foundries.
Sandia lead investigator Greg Nielson said the research team has identified more than 20 benefits of scale for its microphotovoltaic cells. These include new applications, improved performance, potential for reduced costs and higher efficiencies.
“Eventually units could be mass-produced and wrapped around unusual shapes for building-integrated solar, tents and maybe even clothing,” he said. This would make it possible for hunters, hikers or military personnel in the field to recharge batteries for phones, cameras and other electronic devices as they walk or rest.
Sandia project lead Greg Nielson holds a solar cell test prototype with a microscale lens array fastened above it. Together, the cell and lens help create a concentrated photovoltaic unit.
Even better, such microengineered panels could have circuits imprinted that would help perform other functions customarily left to large-scale construction with its attendant need for field construction design and permits.
Said Sandia field engineer Vipin Gupta, “Photovoltaic modules made from these microsized cells for the rooftops of homes and warehouses could have intelligent controls, inverters and even storage built in at the chip level. Such an integrated module could greatly simplify the cumbersome design, bid, permit and grid integration process that our solar technical assistance teams see in the field all the time.”
For large-scale power generation, said Sandia researcher Murat Okandan, “One of the biggest scale benefits is a significant reduction in manufacturing and installation costs compared with current PV techniques.”
Part of the potential cost reduction comes about because microcells require relatively little material to form well-controlled and highly efficient devices.
From 14 to 20 micrometers thick (a human hair is approximately 70 micrometers thick), they are 10 times thinner than conventional 6-inch-by-6-inch brick-sized cells, yet perform at about the same efficiency.
100 times less silicon generates same amount of electricity
“So they use 100 times less silicon to generate the same amount of electricity,” said Okandan. “Since they are much smaller and have fewer mechanical deformations for a given environment than the conventional cells, they may also be more reliable over the long term.”
Another manufacturing convenience is that the cells, because they are only hundreds of micrometers in diameter, can be fabricated from commercial wafers of any size, including today’s 300-millimeter (12-inch) diameter wafers and future 450-millimeter (18-inch) wafers. Further, if one cell proves defective in manufacture, the rest still can be harvested, while if a brick-sized unit goes bad, the entire wafer may be unusable. Also, brick-sized units fabricated larger than the conventional 6-inch-by-6-inch cross section to take advantage of larger wafer size would require thicker power lines to harvest the increased power, creating more cost and possibly shading the wafer. That problem does not exist with the small-cell approach and its individualized wiring.
From left to right, Sandia researchers Murat OKandan, Greg Nielson, and Jose Luis Cruz-Campa, hold samples containing arrays of microsolar cells.
Other unique features are available because the cells are so small. “The shade tolerance of our units to overhead obstructions is better than conventional PV panels,” said Nielson, “because portions of our units not in shade will keep sending out electricity where a partially shaded conventional panel may turn off entirely.”
Because flexible substrates can be easily fabricated, high-efficiency PV for ubiquitous solar power becomes more feasible, said Okandan.
A commercial move to microscale PV cells would be a dramatic change from conventional silicon PV modules composed of arrays of 6-inch-by-6-inch wafers. However, by bringing in techniques normally used in MEMS, electronics and the light-emitting diode (LED) industries (for additional work involving gallium arsenide instead of silicon), the change to small cells should be relatively straightforward, Gupta said.
Each cell is formed on silicon wafers, etched and then released inexpensively in hexagonal shapes, with electrical contacts prefabricated on each piece, by borrowing techniques from integrated circuits and MEMS.
Offering a run for their money to conventional large wafers of crystalline silicon, electricity presently can be harvested from the Sandia-created cells with 14.9 percent efficiency. Off-the-shelf commercial modules range from 13 to 20 percent efficient.
A widely used commercial tool called a pick-and-place machine — the current standard for the mass assembly of electronics — can place up to 130,000 pieces of glitter per hour at electrical contact points preestablished on the substrate; the placement takes place at cooler temperatures. The cost is approximately one-tenth of a cent per piece with the number of cells per module determined by the level of optical concentration and the size of the die, likely to be in the 10,000 to 50,000 cell per square meter range. An alternate technology, still at the lab-bench stage, involves self-assembly of the parts at even lower costs.
Solar concentrators — low-cost, prefabricated, optically efficient microlens arrays — can be placed directly over each glitter-sized cell to increase the number of photons arriving to be converted via the photovoltaic effect into electrons. The small cell size means that cheaper and more efficient short focal length microlens arrays can be fabricated for this purpose.
High-voltage output is possible directly from the modules because of the large number of cells in the array. This should reduce costs associated with wiring, due to reduced resistive losses at higher voltages.
Other possible applications for the technology include satellites and remote sensing.
The project combines expertise from Sandia’s Microsystems Center; Photovoltaics and Grid Integration Group; the Materials, Devices, and Energy Technologies Group; and the National Renewable Energy Lab’s Concentrating Photovoltaics Group.
Involved in the process, in addition to Nielson, Okandan and Gupta, are Jose Luis Cruz-Campa, Paul Resnick, Tammy Pluym, Peggy Clews, Carlos Sanchez, Bill Sweatt, Tony Lentine, Anton Filatov, Mike Sinclair, Mark Overberg, Jeff Nelson, Jennifer Granata, Craig Carmignani, Rick Kemp, Connie Stewart, Jonathan Wierer,
George Wang, Jerry Simmons, Jason Strauch, Judith Lavin and Mark Wanlass (NREL).
The work is supported by DOE’s Solar Energy Technology Program and Sandia’s Laboratory Directed Research & Development program, and has been presented at four technical conferences this year.
The ability of light to produce electrons, and thus electricity, has been known for more than a hundred years.
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December 04, 2009
By: Admin
Category: Solar Power
First Solar Inc. and Ordos City signing MoU in Construction of 2 GW Solar Electricity Generator
Solar electricity generator with a capacity of 2 GW may be far from our imagination, but not in China. First Solar Inc., A solar power company from the United States, will build the solar electricity generator in Ordos city, in the province of Inner Mongol. This project is the development of the world’s largest solar electricity generator. The signing between them have been done at September 8, 2009 at the headquarters of First Solar Inc. in Tempe, Arizona, witnessed by Wu Bangguo, Chairman of the Standing Committee of the National People’s Congress.
“We are proud of the signing of this MoU” said Mike Ahearn, chief executive of First Solar Inc. was quoted as saying by APP.
Government of the United States and China can work together to reduce the cost of electricity from solar electricity generator connected to the network which will be competitive with electricity from traditional energy sources and create a blueprint for accelerating large-scale development of solar energy utilization of the world to prevent / reduce the impact of climate change, he added.
The MOU underscores a long-term partnership between First Solar Inc. and Ordos City, which First Solar Inc. will also consider making investments in the Ordos solar cells.
“We are very pleased to partner with one of the major players in industry of solar electricity generator technology in the project that will impact on low-carbon production in the Ordos.” said Cao Zhichen, deputy mayor of Ordos. For this project the Government of Ordos city will provide 65 square kilometers of land.
“Discussions with First Solar Inc. on the construction of the factory in China is a demonstration for investors in China that they can be confident of investing in high technology fields,” he said further.
China actively increasing the production capacity of electricity cheaper than solar energy sources as part of its national goal to achieve 10 percent energy supply from renewable energy sources by 2010 and 15 percent in the year 2020 including the energy source of wind, hydro, biomass and solar.
Currently, the installed capacity of solar electricity generator in China around 90 MW. Government of China plans to boost the utilization of solar energy from the initial target of just 1.8 GW in 2020 to 2 GW by 2011 and 10 to 20 GW by 2020 as announced in a press conference of the MoU signing.
The first phase of Ordos city solar electricity generator is building 30 MW of project demonstration is planned to begin in June 2010. The next phase, respectively built solar electricity generator with a capacity of 100 MW and 870 MW is expected to be completed by the end of 2014. While the last phase of 1000 MW will be completed by the end of 2019.
Based on the MoU, during the initial phase of implementation, First Solar Inc. will actively study the possibility of development module and manufacturing suppliers in the Ordos. First Solar Inc. also plans to expand its supply chain for the production of thin-film photovoltaic modules and used module recycling.
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November 17, 2009
By: Admin
Category: Solar Battery
The Basic Facts Of Solar Battery
Solar power is an effective way to harness the power of the sun, the plants have been doing this for millions of years. Solar energy is cheap, reliable and can produce tremendous power, but only in the daytime. This is the main problem of solar energy utilization. The average home will use less power during the day, and much smaller in the summer which is the peak power (fastest time) for solar panels to generate energy. To be effective this power should be stored.
One popular way to store solar power is to connect the solar panels to the electrical grid, which effectively turn it into a battery. This allows excess energy to be sent back to the electric company, actually make the electric meter run backwards. At night, the power drawn from the grid as usual. This is only as reliable as the existing grid. Each power outages could still affect these solar panels, but no rechargeable batteries should be used.
Rechargeable batteries are known for having a short age, and expensive. They also have low power flow for a long time with good capacity, or they have a high power electrical short time with the poor capacity. Typical batteries, especially lithium ion, has a high capacity to store power, but provides a weak output and recharge slowly. An ideal solar battery will be able to charge quickly, has a high density to save power and can emit as much power as needed. This ideal combination is something that no battery has been able to do until now. It can only be done through the study of nanotechnology.
Researchers at the University of Maryland have developed a way to create a very powerful battery, the dense refill using nanotechnology. Individual parts, which looks surprisingly like a photovoltaic panel is only a thousand times smaller, is assembling his own, self-replication, and aligning itself too. There is no mechanical process can achieve anything similar small, which also contributes to their relatively low cost. They are still in the testing stage and court, but should look widely and production operations in a year. Able to store the power created from sun and wind will soon make fossil fuels obsolete and mysterious.
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