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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June 25, 2009
By: Admin
Category: Solar Cells
Solar Electric Power Systems
Solar system has a mechanical and electrical components that can convert and store electrical energy that can be used to run your home. Start the calculation that you want to do is an energy audit. You need to evaluate the amount of power that will be needed per day preferably in kilowatts / hour. So the need to consider is the location of your home. That will determine the type of solar system you need is a factor such as climate, number of days of peak sunlight per day, average rainfall and number of days of peak sunlight per year. This calculation can be done by companies that make solar electricity system, and they will guide you in choosing solar electric power systems that are appropriate for your home.
Solar electric power system consists of several components. Some of the components that you will find in the solar electric power system is a primary collector, an inverter, a circuit breaker, battery, charge controller, for collectors and mount the display panel. Collector is a component that collects the sun’s energy. In normal cases, is a solar panel collectors. Collectors on the roof is still using the cushion. Location of solar panels is very important and must be in place where the sun will fall in the maximum on it. Is the ideal place solar panels on the north-south as it will ensure that even if the sun from east to west, the panel get the sun for longer duration.
Inverter is the component that will convert the 12 volt DC power to AC power. Based on the location of the power inverter can convert the 110 volt DC to 220 volt. One of the most important component is the circuit breaker or fuse box. This component has a switch and fuse is important to set the transfer energy from the solar panel to the battery or directly to the outlets. Circuit Breakers control the amount of power that will flow to the outlet and will act as security devices for the application.
If you want to have the storage, then you need to buy one or more batteries depending on your needs. If you have then you need a battery charge controller. This component will ensure you are not over or less in charging battery that will reduce the ability of the battery.
Article You May Be Interested In Reading: Solar Hot Water
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May 18, 2009
By: Admin
Category: Solar Heater
The Benefits Of A Solar Heater: Harnessing The Sun
Executive Summary about Solar Heater by Michelle Bery
A solar heater literally harnesses the energy of the sun. The sun’s core holds enormous energy in the form of radiation; the energy that reaches the earth is considered solar energy.
In the case of a solar heater, we literally “collect” the solar energy that makes its way to earth. Flat plate collectors are thin panels that trap, store, and convert solar energy. When the sun hits the flat plate collector the solar energy is contained inside and used to heat coils within the collector. Those larger structures that are using solar energy find this type of solar heater far more effective for their purposes.
Solar Water Heaters
Executive Summary about Solar Heater by Shweta Rai
Solar water heaters are extremely useful household appliance. These heaters provide ample warm water. Unlike other water heaters, these do not harm the environment. Researches too have proved that these water heaters are quite beneficial. Due to these advantages, solar water heaters are recommended every where.
How solar water heater works?:
These heaters come with storage tank and solar collector. The water is passed through the storage tank and it is heated due to sunlight. There are two pipes, which connect the solar water tank to water heater inside the house. Outlet pipe carries warm water from solar heater to standard heater. The second pipe carries the water in opposite direction. The water heater is painted black, to absorb a lot of light.
How to install these heaters?:
Consult the buyer before buying these water heaters. Make sure that these heaters are placed facing the sun.
What can be approximate cost of these heaters?
Solar water heater cost vary to a large extent.
What are major benefits of these water heaters?
These Water heaters have a number of advantages. They are environment friendly and do not cause any pollution. Secondly, they reduce your electricity expenditure to a large extent
Check out my other guide on Garden Lights
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