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Silicon is commonly used to make solar cells due to its special chemical properties. A silicon atom has 14 electrons that are arranged in three different shells.

The first two shells which have two and eight electrons each are completely full. However, the outer shell is only half full as it only has four electrons. Thus a silicon atom is always on a look out for ways to fill up its last shell.

In order to do this, it will have to share electrons with four nearby atoms to gain stability. It is just as if each atom has joined four hands to four neighbors. This is what forms the crystalline structure, leading to the formation of a PV cell.

However, pure crystalline silicon has the issue of being a poor conductor of electricity as it does not have any free electrons that can move about, as in the case of more optimum conductors like copper.

To solve this problem, the silicon in a solar cell has impurities added, which alters its working.

When pure silicon is supplied some energy, for example in the form of heat, the energy can be used by a few electrons to break free of their bonds and leave their atoms. This leaves a hole behind in each case. The free electrons, called free carriers, then roam around freely around the crystalline lattice looking for another hole to fall into and carrying an electrical current. But their small number in pure silicon don’t make them much useful.

However, when pure silicon is mixed with phosphorous atoms, it takes much less energy to loosen the “extra” phosphorous electrons as they aren’t tied up in a bond with any neighboring atoms. As a result, most of these electrons do break free, and we have a lot more free carriers than we would have in pure silicon.

This adding of impurities is called doping, and when doped with phosphorous, the resulting silicon is called N-type (“n” for negative) because of the prevalence of free electrons. The N-type silicon is a better conductor as compared to pure silicon.

Another part of a typical solar cell is doped with the element boron, which has only three electrons in its outer shell instead of four, in order to form the P-type silicon.A P-type (“p” for positive) has free openings and carries the opposite (positive) charge.

The interaction of the both enables the easy flow of electricity, enabling sunlight to be transformed into electric energy.

Technorati Tags: Silicon,Solar,Cell,atom,conductor,energy,crystalline

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Silicon is commonly used to make solar cells due to its special chemical properties. A silicon atom has 14 electrons that are arranged in three different shells.

The first two shells which have two and eight electrons each are completely full. However, the outer shell is only half full as it only has four electrons. Thus a silicon atom is always on a look out for ways to fill up its last shell.

In order to do this, it will have to share electrons with four nearby atoms to gain stability. It is just as if each atom has joined four hands to four neighbors. This is what forms the crystalline structure, leading to the formation of a PV cell.

However, pure crystalline silicon has the issue of being a poor conductor of electricity as it does not have any free electrons that can move about, as in the case of more optimum conductors like copper.

To solve this problem, the silicon in a solar cell has impurities added, which alters its working.

When pure silicon is supplied some energy, for example in the form of heat, the energy can be used by a few electrons to break free of their bonds and leave their atoms. This leaves a hole behind in each case. The free electrons, called free carriers, then roam around freely around the crystalline lattice looking for another hole to fall into and carrying an electrical current. But their small number in pure silicon don’t make them much useful.

However, when pure silicon is mixed with phosphorous atoms, it takes much less energy to loosen the “extra” phosphorous electrons as they aren’t tied up in a bond with any neighboring atoms. As a result, most of these electrons do break free, and we have a lot more free carriers than we would have in pure silicon.

This adding of impurities is called doping, and when doped with phosphorous, the resulting silicon is called N-type (“n” for negative) because of the prevalence of free electrons. The N-type silicon is a better conductor as compared to pure silicon.

Another part of a typical solar cell is doped with the element boron, which has only three electrons in its outer shell instead of four, in order to form the P-type silicon.A P-type (“p” for positive) has free openings and carries the opposite (positive) charge.

The interaction of the both enables the easy flow of electricity, enabling sunlight to be transformed into electric energy.

Technorati Tags: Silicon,Solar,Cell,atom,conductor,energy,crystalline

People who liked this Post also read

• Anatomy of a Solar Cell
• What Are Solar Panels?
• Function of Photovoltaic Cells
• How Solar Does And What it Does?
• Solar Towers- Get Power In the Dark
• 7 Simple Ways To Utilize Solar Energy in a Pre-Existing Home
• Using Solar Electricity In Your Garden
• Solar Power Goes Underground
• Energy Story: What Is Electricity?
• What Are Solar Power Plants?

The Martin Next Generation Solar Center represents a breakthrough in solar-natural gas relations, or at least a way to make a brown fossil fuel plant a bit greener. Florida Power and Light (FPL), a utility already known for its advancements in wind, solar power and energy efficiency, is building the 75-megawatt concentrating solar thermal plant adjacent to an existing natural gas plant.

The Martin Solar Center will be the first hybrid facility to attach solar thermal power to a combined-cycle power plant, says FPL. It will also be the second-largest solar facility in the world and the the largest solar power plant of any kind outside of California.

The solar thermal arm will consist of 180,000 mirrors reflecting solar radiation onto a receiver. The receiver contains liquid that will be heated to create steam, directly displacing the fossil fuel energy otherwise needed during the day. The hybrid effort by FPL is an attempt to bring the cost of solar energy down by sharing plant infrastructure.

The solar thermal plant will produce 75 megawatts of solar electricity at peak output. So, during the day under that bright Florida sunshine, the solar system will create enough energy to power 11,000 homes, or 26,000 people. It is expected to reduce statewide greenhouse gas emissions by 2.75 million tons over 30 years.

While environmentalists would like to see renewable energy create baseload power, the possibility of which is a definite point of contention within and without the green energy movement, hybrid power plants have been suggested as a way to bridge that gap while making solar power more competitive with its fossil-fueled rivals.

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Welcome to the suction cup era of solar lighting. Just last month, we discovered the PowerPlus Spider Solar Light that uses a triad of suction cups to stick to a south-facing window, providing solar-powered LED lighting at night. Turns out that was only the diminutive preamble, as this week we find the Saint Clair Lamp, a much more modern and less portable design (not for camping trips) from French architect and designer, Stephane Maupin.

The Saint Clair was a winning entry for the VIA Project Assistance Grant that seeks out young design talent and connects them with manufacturers and producers. It looks something like a thin desk lamp with a go-go-gadget neck and a rectangular LED fixture for a head. The advantage of this spindly design — the lamp is just over three feet long — is that the light can be left hanging on a window after dark and still cast direct light on a sofa, table, piece of wall art or just into the room proper.

The Saint Clair lamp comes equipped with a set of photovoltaic solar cells that collect solar energy through the window during the day. At night, it can either remain on that or some other window in the house, or, when fully charged, stand just fine on a desk or table. It is super-sleek modern white with a 12-inch-round, flying-saucer-shaped base.

The lamp runs for 45 euros (about $62), which is a hefty handful of change — more than the $8 PowerPlus Spider lamp, but I suppose you’re paying for (much) higher quality design and, I expect, better materials and components.

Story & Photos Via designboom

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The Arizona Solar Power Society (http://www.arizonasolarsociety.com) reports that the residential solar market in Arizona is creating a gold mine of solar revenue. In the past 18 months, more than 275 residential solar installation companies have opened shop, hired thousands of employees and created one of the most promising industries seen in a decade in Arizona, a state with more sunshine to harvest than anywhere in North America.

Suniva Inc. this week received the 2010 Green Transaction of the Year award from the Export-Import Bank of the United States (Ex-Im Bank) at the Bank’s annual conference in Washington D.C. Suniva used a US $2 million Ex-Im Bank short-term multi-buyer insurance policy to offer a $500,000 credit line to a customer in India to buy its solar equipment, and has a number of other potential export deals in the pipeline. The company plans to expand its U.S. facilities and add U.S. jobs to meet growing demand.

Four democratic senators have introduced an initiative urging the Obama administration to suspend a U.S. Treasury grant program formed under the Recovery Act. The program enables renewable energy producers to receive grants in lieu of Investment Tax Credit payments, essentially providing valuable financing up-front rather than over a number of tax years. That program has spawned a revival in investments for clean energy projects in the wake of the worst economic crisis since the Great Depression, and is widely lauded by RE industry members.

However, senators Charles Schumer (D-N.Y.), Bob Casey (D-Penn.), Sherrod Brown (D-Ohio) and Jon Tester (D-Mont.) are concerned that components for these projects are coming from foreign companies. In other words, they believe funds intended to boost the U.S. economy should be doing just that, not bolstering economies overseas. I absolutely agree with the notion that U.S. dollars should not be spent overseas, but the problem goes deeper than a Recovery Act grant program and ends with one gaping hole in American clean energy policy: a national renewable electricity standard (RES).

The grants-in-lieu-of-credits program has been wildly successful, and its removal could be detrimental to green energy investing and deployment, as recently argued by wind industry representatives before Congress. The Recovery Act stipulates that all stimulus funding must be spent within the United States, and industry executives argue that it is…to the highest possible degree. The problem is that key components of a wind or solar installation may not be available in this country.

Now that manufacturing credits are in place, that sector of the RE industry is picking up. Those same wind power industrialists noted that several new manufacturing plants have opened up in the last year, but that the U.S. still does not have a complete supply chain in place. They also posit that had a national RES been in place at the time of the Recovery Act’s passage, even more manufacturing jobs would have been created. I agree. Foreign and domestic investors still see energy policy in the U.S. as unstable; and rightly so. Anyone with even a marginal interest in national politics can see how unstable, inefficient and unproductive Congress has been on every front over the last few years.

We need some sort of national policy for — which would act as a national statement on — renewable energy. There are a lot of pleasant pieces, mostly found within the Recovery Act, but the glue that holds everything together is missing, resulting in a fractured and frenetic political environment in which legislation succumbs to the will of one belligerent senator or corporate lobby. Even loud-mouthed pundits and talk show hosts seem to have more power than elected officials.

The best way to quiet this storm, to move forward rather than stumble and swear, is to enact that national policy. I’ve argued before for increasing import tariffs long sacrificed to free trade and corporate globalization. A national feed-in tariff the likes of which propelled Germany to the front of the global solar stage would be another vital step. But these and other steps, including grants and tax credits, will only be as strong as the renewable electricity standard backing them. Our lack of any unifying RES is stunting the U.S. renewable energy industry. We’re grasping at straws instead of bailing hay.

One need only look at states with aggressive RES to see their effectiveness. Arizona enacted its first RES in 2006 and (if sudden turbulence within that state subsides) will be home to the first American manufacturing plant of Chinese solar giant Suntech Power Holdings. Oregon instituted both an RPS and state-level manufacturing tax credits and is now home to German giant SolarWorld’s North American headquarters that includes a 550-megawatt manufacturing facility. California needs no introduction.

To really advance renewable power, we must have a national RES. I’d prefer it were accompanied by a national FIT and a strong carbon tax, but the standard is step-one in bringing everybody in line. It will give foreign investors the confidence to invest in power plants on U.S. soil. Nobody wants to pay the oft-exorbitant shipping costs involved in overseas transport, but investors don’t like risk — something the Recovery Act grant program has helped diminish, a decrease that a national RES would all but guarantee.

Another benefit of national RE policy would be the actual and permanent creation of all these high-quality green jobs so proudly touted in renewable rhetoric. We must bring manufacturing to our shores. Grants have and are bringing some, a reason why repealing that program is not the solution, but an RES would bring more. Too many jobs in renewable energy (i.e. power plant construction) are temporary.

We often hear how this or that incentive will add so many thousands of green jobs per year, leading us to believe that employment will steadily rise by 3,000 each year. Hooray! But in reality, most of those jobs are temporary and the same 3,000 workers who manned new jobs one year will man the same “new” jobs the next year. Solar and wind power plants require relatively little maintenance or manpower for operation. A sizable power plant might require only a dozen or two permanent employees.

So where in the world is our national RES?

It’s in Germany, Spain, France and – gulp – China. Along with our jobs and prosperity and clean energy economy. The world is on the cusp of truly transitioning into a 21st-century energy economy, one dominated by wind and solar and geothermal rather than coal and gas and oil. Right now, the United States is stuck on the edge, bickering amongst ourselves while the rest of the world passes us by.

As Leonard Cohen once famously rhymed about America, “It’s there they’ve got the range and the machinery for change.” Well, let’s get those machines (and our congresspersons) fired up. Let’s have our national renewable electricity standard and be a positive leader and force for change at home and abroad.

Sincerely, D. Harding

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With an ambitious goal of being 100-percent renewable-powered, Wal-Mart wants to be a green company — but apparently on its own terms. The company has been fighting for more than two years against a pair of lawsuits that demanded that two planned stores get greener. The Center for Biological Diversity and a handful of other groups filed lawsuits against the California cities of Yucca Valley and Perris, contending that two Wal-Mart Supercenters, if built as planned and approved by the cities, would violate California’s greenhouse gas emissions standards under the California Environmental Quality Act.

After years of litigation, Wal-Mart finally decided to bury the hatchet by settling. And the settlement bodes well for environmentalists. In order to set things right, the infamous supermarket chain must add three rooftop solar power systems at least 250 kilowatts in size, install efficient heating and cooling systems, as well as LED lighting at the two new stores, and donate $120,000 to the Mojave Desert Land Trust — a group trying to expand Joshua Tree National Park.

Wal-Mart is happy that the mess is over, while the environmentalists are happy that a major retailer will, like it or lump it, set the example that a “big box” store can be built efficiently using renewable power. So, Wal-Mart has been testing new store designs and renewable energy systems that would make their “boxes” more energy efficient and hopefully totally renewable-powered. Several solar arrays have already been installed on California stores, generating 20-30 percent of each store’s power needs, says Wal-Mart. The company plans to add up to 20 new systems in the next year.

All that said, it seems weird that the company would go two years without settling lawsuits that simply wanted Wal-Mart stores to meet GHG standards already in place, of which Wal-Mart must have been aware of, considering the slew of other stores in California. Whatever the reasons for the holdout, be they financial or bureaucratic, the result will benefit both Perris and Yucca Valley, as well as Joshua Tree National Park — one of the most beautiful and fun parks I’ve ever visited.

Sources:  The Press-Enterprise & Environmental Leader

Photo Credit: Box Turtle Bulletin & Blue Oak Energy

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We have all seen calculators with solar cells, that enable the device to work without any batteries, and can be used for unlimited time period as long as there’s enough light.

These solar cells that are present in calculators and many other devices are also called photovoltaic (PV) cells. As the name depicts, these cells have the capability of converting sunlight directly into electricity.

A group of cells can also be connected together electrically, fitted into a frame to form a solar panel. Moreover, these solar panels can be combined together to form larger solar arrays, similar to the ones operating at Nellis Air Force Base in Nevada.

Photovoltaic cells are made up of special material called semiconductors such as silicon, which is currently used most commonly.

When light falls on to the cell, a certain amount of the light is absorbed by the semiconductor material. The energy of the absorbed light is then transferred to the semiconductor. The energy is used to loosen up the electrons, allowing them to flow freely, and thus create electricity.

PV cells also have one or more electric fields that force electrons freed by light absorption to flow in a certain direction making a current. Thus by inserting metal contacts on the top and bottom of the PV cell, we can direct the current for some external use. This current, combined together with the cell’s voltage due to the built-in electric fields, defines the power that the solar cell can produce.

This is the basic process through which photovoltaic cells work, but clearly there’s much more to it, which will be explained in the proceeding articles.

Technorati Tags: Photovoltaic,panel,cell,energy,voltage,Cells,batteries,panels,semiconductor,electrons

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Nanoscience is quite fascinated with the process of photosynthesis. They want to duplicate this process exhibited by green plants and utilize the solar power for energy use. Till now power generating solar panels are not in a position to replace the fossil fuels. They produce little amount of energy and quite expensive also. Generation [...]
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