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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October 05, 2009
By: Admin
Category: Solar Home
What To Expect From Solar Power Home?
Many people, especially those who are beginners in solar technology may wonder how solar panels work. But first, what is the home solar panels? This is a solar-powered gadget that collect and use the energy from the sun through its rays and convert it into power.
Some people use solar panels home gadgets to act as an alternative source of energy for their small household, effectively complements the consumption of electricity from local utilities.
There are still homeowners who invest in residential solar panels are fully able to provide power to the house, run all appliances, water heaters and swimming pool. However, the cost is very expensive if you intend to own and install your own home solar panels that will work as the only source of daily strength. A solar panel unit actually has a very high price from a few thousand dollars.
How solar panels work can be answered simply. He has a photovoltaic cell in a panel that primarily works by collecting energy from sunlight that falls on them, then solar energy is converted into electrical energy for use at home.
You may very well consider this gadget as an investment, because you need to shell out large enough amount of money to buy and install them as your resource. It is a serious investment even if you only need to spend the money early, the amount needed is really great. After purchase you do not have to worry about this as the sun runs his own gadgets, making endless supply of electricity to your residence with the help, of course, the sun.
Many supporters of a clean environment and recommended the use of green house solar panels, if only because the energy that collects and converts power from the sun. Therefore, the power generated is clean and not harmful to the environment of the world. Likewise, you do not have to worry about running out of the sun’s energy for endless supply. Solar energy is a clean renewable energy, and is considered the best alternative energy is there.
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June 03, 2009
By: Admin
Category: General
New Solar Technology Trends Around the World
Executive Summary about Solar Technology by Philip Richards
In the business of solar energy, the U.S. has not been the biggest buyer of solar power. While the U.S. does quite well exporting solar panels and solar technology, there are many Americans who still find the cost of panels very prohibitive. As the price of solar energy decreases, Europe has had a much higher demand for solar power than anywhere else in the world. Many European universities and campuses have rebuilt their dorms to run off solar energy. Most water heaters in Europe are solar-powered, even if the home doesn’t have a full solar panel system.
In Europe, it’s not just small residential power systems that are leading the way in solar energy dependence. Specifically, Italy, Greece and the Czech Republic are the newest customers of solar power systems. These countries have begun to purchase so much solar energy that their borders have seen changes in tariffs for solar panels. Japan, who’s also been at the forefront of solar panel imports, has picked up solar panel buying as the cost of gas and electricity rises. There are entire neighborhoods in Japan outfitted with residential solar power panels. For example, the neighborhood of Iwaki New Town has about 46 homes outfitted with full private solar power panels. Japan also uses solar energy in surprising places. Japan is the only country to power most of its vending machines with solar energy. Sharp, one of the largest solar panel producing companies in Japan estimates that by 2010, Japan will produce 4.8 million kWh of solar energy.
The Race For New Solar Technology Is On
Executive Summary about Solar Technology by Winifred Churchill
Companies around the world are beginning to seriously consider the POWER of solar power.
- In Mexico a solar dish is being tested. The expanding and contracting hydrogen gas drives pistons which power a generator which creates electricity.
- A new thin-film technology is being used on the windows of high-rise apartment buildings and skyscrapers to collect the sun’s power for use in the buildings. It is attractive and not nearly as expensive as regular solar panels.
- Thin-film is attracting major manufacturers around the world.
- New solar technology is using crystalline silicon cells for solar power panels.
One criticism of solar energy is that it cannot be relied upon for a steady supply of energy, but there are projects underway which are addressing that issue. In short, solar technology is going the way of the computer industry or cell phones. Now you get the same functionality available in personal computers on tiny cell phones. The new silicon cells for solar panels may bring a similar revolution to solar power making it a reliable, clean source of energy.
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