Photovoltaic (PV) Module and Its Lifespan

Photovoltaic (PV) cells are transistors or integrated circuits on steroids. Most people have seen the latest microcomputer chip used in PCs. It's a silicon wafer about the size of your thumbnail that holds several millions transistors and other electronic parts. PV cells start out the same way circuits, but they are kept in the oven until they are much larger, approximately 10 cm in diameter. The baked silicon rods are sliced into wafers which are polished and assembled with interconnecting electrical wires. A grouping of PV cells which are arranged in a frame is called module.

Almost all photovoltaic module manufacturers provide a written guarantee for 20 to 25 years or more. The manufacturers are obviously quite sure that their products will stand the test of time. The reason for this certainty is the same one that explains why old transistor radios last so long. The semiconductor technology of the cell wafer results in very little wear and degradation.

The standard warranty term from siemens states that any module that loses more than 10 % power output within 10 years or 20 % within 25 years will be repaired or replaced. (This is known as a limited liability warranty, more commonly known as the fine print; be sure to read this detail carefully to ensure you understand the warranty terms.) Cell technology and quality of workmanship are very high in the industry, so be sure to purchase cells with the best possible warranty for your money.

The cells themselves are quite fragile. To protect them from damage and weather, the cells are bonded to a special tempered-glass surface and sealed using a strong plastic backing material. (Laminated or flexible "roof shingle" systems replace the glass surface with a tough, flexible polymer). The entire module is inserted into an aluminum, non-corroding housing to form the finished assembly. Once a grouping of modules, called an array, is mounted to a roof or to a fixed or tracking rack, it should stay put forever.

Elieser Tarigan is an expert on solar energy technology. He has written several articles on solar thermal, solar electricity technologies, and other green energy. To learn more about him, visit his site: http://netfinest.com

Solar Technology and Photovoltaic Cells

Concentrating photovoltaic's (CPV) uses lenses and mirrors to focus the sun's energy. This technology includes both a low-concentration approach, which increases the sun's magnification by between 2 and 100 times, and a high concentration approach, which can increase the magnification by hundreds of suns when the PV efficiency exceeds 40%. CPV uses less photovoltaic material and increases performance, hopefully enough to offset any additional costs.

Concentrating Photovoltaics and Thermal (CPVT) is another technology; this produces both electricity and thermal heat in the same module. Thermal energy itself is a benefit from the sun, and other plants have a design of a solar power tower in which the mirrors focus sunlight on a heat receiver at the top that collects the heat and transfers it to piping inside the tower where is it circulated and used to make electricity. The design minimizes the field of piping to the vertical tower height to a few hundred meters and can reach temperatures in excess of 1000 degrees.While currently there are very few commercially operating tower installations, based on announcements, this technology may grow rapidly.

The Solar Two tower in California is an example of this technology and has the capability to produce 10 megawatts of power. Because of its success, Solar Tres is being built in Spain; this will be three times larger than the Solar Two plant and have a capacity of 17 megawatts. As it is, Solar Two's tower has been removed in 2009 to make way for a larger solar project. Another solar thermal technology is the parabolic trough. The SEGS plants in California utilize this technology and have a capacity of 33 megawatts each. Nevada Solar One is another very large CSP project with a capacity of 64 megawatts, using Flabeg AG troughs made in Germany.

When we look into photovoltaic cell technology and the materials used, throughout the world crystalline silicon has been used as the light-absorbing semiconductor in most solar cells, even though it is a relatively poor absorber of light and requires a considerable thickness of material. Nevertheless, it has proved convenient because it yields stable solar cells with good efficiencies. There are two types of crystalline silicon are used in the industry. The first is mono crystalline, produced by slicing wafers from a high-purity single crystal. The second is multi crystalline silicon, made by sawing a cast block of silicon first into bars and then wafers. Most efficient production cells use mono crystalline c-Si with laser grooved, buried grid contacts for maximum light absorption and current collection. The main trend in crystalline silicon cell manufacture is toward multicrystalline technology. And for both mono- and multicrystalline Si, a semiconductor homo junction is formed by diffusing phosphorus into the top surface of the boron doped (p-type) Si wafer. Screen-printed contacts are applied to the front and rear of the cell, with the front contact pattern specially designed to allow maximum light exposure of the Si material with minimum electrical (resistive) losses in the cell. Crystalline silicon cell technology forms about 90% of solar cell demand. The balance comes from thin film technologies. Approximately 45% of the cost of a silicon cell solar module is driven by the cost of the silicon wafer, a further 35% is driven by the materials required to assemble the solar module.

Deevan Solar Panel Hot Water Heating.

Concentrated Solar Power California.

How to build solar panels

The basic components of photovoltaic solar modules are not building a simple process; in fact, making effective solar cells from scratch it is practically impossible without the use of high-tech tools. You can put together easily enough solar panels once you have cells, but the production of solar cells themselves is a very complex process. (By the way, the word "photovoltaic" is a fancy word for the process by which sunlight is converted directly into electricity).

A cell is born

The same is the photovoltaic cell that converts sunlight into electricity. It has many other uses as well; can be used in surveillance equipment that allow law enforcement to "see" through walls by detecting infrared radiation, as well as other types of electromagnetic radiation. It can also be used to measure the intensity of the light and thus help photographers calibrate their cameras and to measure some chemical reactions in laboratory conditions.

The first step in creating a solar panel is to get semiconductora. Usually, this is pure silicon, which is produced by Quartz. The Silicon is melted and combined with traces of boron or phosphorus, then allowed to cool in a block. This block is then cut into thin wafers and the surfaces are carefully engraved and clean.

The next step is to put these wafers in what is known as a diffusion furnace. This exposes the wafer to very high temperatures, which cause the formation of a semiconductortype n. The "N" in this case stands for "Negative"; This heat treatment creates an abundance of negative electrons, that is what helps produce current when direct sunlight hits the surface.

But wait-we are not finished yet! The surface of the wafer must be painted with an anti-reflective coating. After all, we want our photovoltaic cell to absorb sunlight, bouncing back into space! Once this happens, the electrical contacts are imprinted on top.

What is missing? Ah, Yes ... the type p or positively charged surface. This is created on the bottom or on the back of the photovoltaic cell, using a form of aluminum.

Put together

Once the cell has been tested, is connected with other cells to make photovoltaic solar panels. Now you can appreciate why these little devils are so expensive to produce. The good news is that new technologies – particularly nanotech, or the use of microscopic machines built at the molecular level-dramatically is lowering the cost of this process.

Wayne Hemrick writes about- solar panels.