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 01, 2009
By: Admin
Category: Solar Light
Outdoor Solar Lights Explained
Outdoor solar lights uses the identical action to generate power as the solar panels on your ceiling (or that you could set up on your ceiling, if you selected to). Essentially, it applies photovoltaic (PV) cells, which accumulate and switch solar energy into electrical energy. The PV cells apply semiconducting materials to engage the sun’s light, which interacts with the silicon and another components to produce electrical energy. The electrical energy runs over cables which power the battery, which in go powers the light. This is an highly simple explanation, but it will present you the common idea of how solar cells play. They can only make electrical energy from direct sunshine, which is why solar lighting wants a battery in order to be able to light up the dark.
So that the batteries to keep a constant charge, the solar light fixture should be in a position that meets full sunshine for almost of the daylight. If it just gets partial sunlight, because it’s barred by trees or other construction, or because your area has much of cloudy conditions, the batteries will run out earlier, and your fixture will supply light for a lower amount of time. Most outdoor solar lights fixtures own a backup power system which applies rechargeable batteries. Solar lights fixtures which apply a small amount of electrical energy frequently apply small AA Ni-Cad or NiMh batteries. But more strong solar lights fixtures (like head lights) apply a covered lead acid battery.
Photo detectors that automatically evaluate light degrees (like the kind that tells your photographic camera when to apply its flash) are constructed into the solar lights fixtures. They monitor light degrees and turn the fixture off at morning and on at nightfall. But get sure there are no artificial light sources (like a street lights or head light) that may contribute a wrong reading and forbid the light from turning on.
Outdoor solar lights usually utilizes LED bulbs. They apply less power than incandescent bulbs and, with a lifetime of around 20 years, are much longer-lasting. Until lately, solar lights overall has not been as bright as lighting powered straight by direct current electrical energy. But the earliest super bright LEDs can at present illuminate as well as halogen bulbs.
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May 30, 2009
By: Admin
Category: Solar Electricity
Home Solar Electricity – What to Know Before Purchasing Anything
Executive Summary about Solar Electricity by Melanie Crouse
There are even tax rebates available in many states for families that are converting to home solar electricity. If you’ve been thinking of using PV (photovoltaic) panels for your home solar power, but are finding that it is too expensive, there are other options. There are many green energy suppliers that provide power from various renewable resources, such as solar electricity, wind power and hydroelectricity. If you’ve decided that solar power is the way you want to go, you will need to determine your actual power needs first.
The first thing you need to determine is how much electricity you need your home solar electricity system to generate. Do you want a grid-tied system where you are still connected to the grid, using a combination of your own solar power and the power supplied by the utility company? Or you can combine your own home solar electricity system with the grid, selling back any excess power that you don’t use to the power
Designing Solar Electricity Systems For Your Home
Executive Summary about Solar Electricity by Gary Ashby
Are you interested in designing solar electricity systems for your home? Before you build your homemade solar electricity systems, you must first consider the electrical requirements of your household as well as how much energy you wish to generate with the solar panel system.
1. Are You Comfortable Working On The Roof?
2. Is There Enough Space On Your Roof For Solar Panel Installation?
Your roof needs to have enough space for you to build sufficient solar panels on it.
3. What Happens When You Are Able To Generate More Electricity Than The Amount That Your House Requires?
4. How Exactly Do You Put a Solar Electricity System In Your Home?
Thousands of people have already eliminated their own home electricity bills with this free solar energy system that they learned how to build with a step-by-step guide online.
Article You May Be Interested In Reading: Solar Battery
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May 18, 2009
By: Admin
Category: Solar Battery
Solar Batteries – Deep Cycle
Executive Summary about Solar Battery by Michael Motley
Batteries are separated into two categories, by application (what the battery is used for) and construction (how the battery is built). Deep-Cycle batteries are the battery of choice for most installations because of the way they are made. Deep-cycle batteries are made to be run completely down relatively fast, and recharged just as fast, constantly. The major applications for deep-cycle batteries are solar electric (PV), backup power source, and boat/RV batteries.
There are 3 main construction types at this time:
Flooded batteries are what most people think of when thinking of batteries of this size.
Gelled Batteries or Gel Cells are sealed, and some are valve regulated. They contain gelled acid that was gelled by adding silica gel, making like a battery acid jelly.
AGM (Absorbed Glass Mat) batteries are similar to the gelled batteries but they also have fiberglass mat between the plates of the batter, which is then filled with gel. These batteries are the premier choice if you have any concerns about spilling of battery acid.
The main difference in deep-cycle batteries is thicker plates. The thicker plates allow the deep-cycle battery to be discharged down as much as 80% over and over again. The battery with the thickest plates will last the longest
A battery cycle is one complete discharge and recharge cycle. How deep a battery is discharged directly affects its life span.
Battery Life
There are many variables to deep-cycle battery life. The standard flooded battery 1-6 years. In the deep-cycle family of batteries, the AGM has one advantage over the other two types in it’s class. There is a myth that you shouldn’t store batteries on concrete floors.
Battery Quick Facts
* Almost all batteries have to be cycled 10-20 times before being able to reach full capacity.
* Always keep vent caps on your flooded batteries when charging.
* Lead-Acid batteries do not have a memory. Use only clean water to clean the outside of batteries.
Solar Battery Technology
Executive Summary about Solar Battery by Anne Clarke
People are realizing that they can easily change the way that power is created. For two centuries the world has relied upon fossil fuel, mostly coal and oil, for almost every form of power. It lights our homes, powers our appliances and drives our cars. Unfortunately fossil fuels rely on combustion to release their power. Solar power is an effective way to harness the power of the sun, something plants have been doing for millions of years. It can produce more power during the day than the average home uses. Most houses will use less power during the day, and much less in the summer which is the peak power producing time for solar panels. To be effective this power must be stored somehow.
One popular way of storing solar power is by connecting the solar panels to the existing electrical grid, effectively turning it into a massive solar battery. At night power is taken from the grid as usual. Any power outages can still affect these solar panel set-ups, but no rechargeable batteries have to be used.
Rechargeable batteries are notoriously short lived and expensive. They either have low power flows for a long time with a good capacity, or they have high power flows for short times with poor capacity. Typical batteries, especially lithium ion, have high capacity for storing power, but deliver a weak output and recharge slowly. The ideal solar battery would be able to charge quickly, have a high density for storing power and be able to emit as much of that power as is needed.
Check out my other guide on Solar Light
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