The Solar Cells

The purpose of the contemporary human is to achieve a personal comfort increasingly high. In terms of contemporary art, to increase comfort, fall back on exaggerated growth of energy consumption. At the current rate, approximately 400 years after the beginnings of industrialization, the world will consume almost entirely fossil fuels accumulated in 400 million years. Burning fossil fuels in this huge reservoir, besides obtaining energy supply and continue to be issued in a large quantity of toxic gas that will transform the atmosphere in the state in which it was millions of years ago. To keep the remaining fossil resources on a while longer and for the preservation and restoration of conditions of human life on earth should we target the use of renewable energy sources.

History of Photovoltaics

The first conventional photovoltaic cells were produced in the late 1950s, and throughout the 1960s were principally used to provide electrical power for earth-orbiting satellites. In the 1970s, improvements in manufacturing, performance and quality of PV modules helped to reduce costs and opened up a number of opportunities for powering remote terrestrial applications, including battery charging for navigational aids, signals, telecommunications equipment and other critical, low power needs.

In the 1980s, photovoltaics became a popular power source for consumer electronic devices, including calculators, watches, radios, lanterns and other small battery charging applications. Following the energy crises of the 1970s, significant efforts also began to develop PV power systems for residential and commercial uses both for stand-alone, remote power as well as for utility-connected applications. During the same period, international applications for PV systems to power rural health clinics, refrigeration, water pumping, telecommunications, and off-grid households increased dramatically, and remain a major portion of the present world market for PV products. Today, the industry’s production of PV modules is growing at approximately 25 percent annually, and major programs in the U.S., Japan and Europe are rapidly accelerating the implementation of PV systems on buildings and interconnection to utility networks.

Photovoltaics (PV) or solar cells as they are often referred to, are semiconductor devices that convert sunlight into direct current (DC) electricity. Groups of PV cells are electrically configured into modules and arrays, which can be used to charge batteries, operate motors, and to power any number of electrical loads. With the appropriate power conversion equipment, PV systems can produce alternating current (AC) compatible with any conventional appliances, and operate in parallel with and interconnected to the utility grid.

Solar panels used to produce electricity

The solar panels used to produce electricity, are really interesting, because generating electricity free. On the basis of this process is photovoltaic cell. In short, in contact with the sun, it produces electricity. Fotons of sunlight (such small particles produced especially by the Stars, moving with light speed) "bombe" atoms in the material which is made photovoltaic cell. Under this, they undergo transformation releasing electrons (thus forming electricity).

Photovoltaic cells are grouped into matrices, which in turn make up the solar panels.

The advantages and disadvantages of solar panels

The advantages of using these systems are obvious: renewable energy and free, which can be used to supply permanent dwelling citizens. It is true that the cost of an WATT through solar panels is 6-7 times higher than the cost of producing its thermal, but the investment depreciated over time. In addition, do not forget: solar panels are organic. And how natural resources are already in danger of exhaustion would be little time to think about our future and our children right now. May be clearly said that the purchase price of the entire equipment is still high (but the price is constantly declining, and in addition it is paid only once in principle, following the much to pay in a number of years a maintenance fee installations and equipment are depreciated in a number of years, even after they become profitable, while cleaner technologies of the future come down, they might drop their price even if now would be produced in industrial quantities much higher, produced by modern technology (resulting from advanced scientific research, which must attend mandatory collective multidisciplinary), for these reasons the production and their use should be compulsory controlled by governments through agencies and government departments of energy, environment, creation of new technologies, industrial and scientific, all governments are called upon to subsidized the purchase price of equipment at least for a period of 20-40 years, that is, as long as the equipment is still in an experimental stage and technology manufacturing cost which is reflected even in their purchase price.

The efficiency of solar panel very much depends on the angle under which falls on the solar radius, which implies the need for mounting such a system of energy production by specialists. To cover energy needs of the whole case will be a need for solar panels many tens of square meters because the equipment needed to cover the entire home and family concerned and the old contracts for the supply of electricity to end total in this way is truly unloaded the national energeticaly system, is an economy of electricity produced classic, and an decrease of indirect losses of transport networks. Because yes, it is possible that a dwelling to work exclusively with solar energy in ideal conditions.

The production of electricity with solar panels are reliable, can hold up to 25 years. Their performances have raised increasingly in recent years, and the price of assembly and made decreased. It is estimated that the price of electricity generation by panels with photovoltaic cells will equal that of polluting energy (produced by thermal power). To top solar panels are ideal for the supply of electricity to isolated housing, the research points or satellites (they used for the first time this type of energy).

Installing your solar photovoltaic (PV) system means that you can generate your electricity from the free and inexhaustible energy from the sun. A photovoltaic system never needs refuelling, emits no pollution, and can be expected to operate for over 30 years while requiring minimal maintenance. A typical PV system on a house roof could prevent over 34 tonnes of greenhouse gas emissions during its lifetime.

Today photovoltaic systems are recognized by governments, environmental organizations and commercial organizations as a technology with the potential to supply a significant part of the worlds energy needs in a sustainable and renewable manner. Organizations such as Shell and BP have set up large photovoltaic manufacturing plants and environmental organizations such as Greenpeace strongly support the use of solar energy.

Installing a photovoltaic system is one of the ways householders and other building owners can contribute towards a sustainable future for everyone.

With global climate change threatening all our futures, we need to switch to clean, renewable forms of energy and electricity production. Solar electric panels can generate electricity that is free from pollution, fuelled by the natural resource of the sun, which is free, abundant and inexhaustible.

The key benefits of a solar roof are: - Your clean power source that helps reduce global warming - Reduces your electricity bills, since daylight is free - Increases the value of your property - Extremely low maintenance, with a long functional lifetime of 30 years or more - Silent in operation - Increases your awareness of electricity use and encourages more energy efficient behaviour

Photovoltaic means electricity from light. Photovoltaic systems use daylight to power ordinary electrical equipment, for example, household appliances, computers and lighting. The photovoltaic (PV) process converts free solar energy - the most abundant energy source on the planet - directly into electricity. Note that this is not the familiar solar thermal technology used for heating and hot water.

A PV cell consists of two or more thin layers of semi-conducting material, most commonly silicon. When the silicon is exposed to light, electrical charges are generated and this can be conducted away by metal contacts as direct current (DC). The electrical output from a single cell is small, so multiple cells are connected together and encapsulated (usually behind glass) to form a module (sometimes referred to as a "panel"). The PV module is the principle building block of a PV system and any number of modules can be connected together to give the desired electrical output.

PV equipment has no moving parts and as a result requires minimal maintenance. It generates electricity without producing emissions of greenhouse or any other gases, and its operation is virtually silent.

PV systems supply electricity to many applications, ranging from systems supplying power to city buildings (which are also connected to the normal local electricity network) to systems supplying power to garden lights or to remote telecom relay stations.

The main area of interest today is grid connect PV systems. These systems are connected to the local electricity network. This means that during the day, the electricity generated by the PV system can either be used immediately (which is normal for systems installed on offices and other commercial buildings), or can be sold to one of the electricity supply companies (which is more common for domestic systems where the occupier may be out during the day). In the evening, when the solar system is unable to provide the electricity required, power can be bought back from the network. In effect, the grid is acting as an energy storage system, which means the PV system does not need to include battery storage.

Grid connect PV systems are often integrated into buildings. PV technology is ideally suited to use on buildings, providing pollution and noise-free electricity without using extra space.

PV systems can be incorporated into buildings in various ways. Sloping rooftops are an ideal site, where modules can simply be mounted using frames. Photovoltaic systems can also be incorporated into the actual building fabric, for example PV roof tiles are now available which can be fitted as would standard tiles. In addition, PV can also be incorporated as building facades, canopies and sky lights amongst many other applications.

Types of PV Cell: Monocrystalline Silicon Cells: Made using cells saw-cut from a single cylindrical crystal of silicon, this is the most efficient of the photovoltaic (PV) technologies. The principle advantage of monocrystalline cells are their high efficiencies, typically around 15%, although the manufacturing process required to produce monocrystalline silicon is complicated, resulting in slightly higher costs than other technologies.

Multicrystalline Silicon Cells: Made from cells cut from an ingot of melted and recrystallised silicon. In the manufacturing process, molten silicon is cast into ingots of polycrystalline silicon, these ingots are then saw-cut into very thin wafers and assembled into complete cells. Multicrystalline cells are cheaper to produce than monocrystalline ones, due to the simpler manufacturing process. However, they tend to be slightly less efficient, with average efficiencies of around 12%., creating a granular texture.

Thick-film Silicon: Another multicrystalline technology where the silicon is deposited in a continuous process onto a base material giving a fine grained, sparkling appearance. Like all crystalline PV, this is encapsulated in a transparent insulating polymer with a tempered glass cover and usually bound into a strong aluminium frame.

Amorphous Silicon: Amorphous silicon cells are composed of silicon atoms in a thin homogenous layer rather than a crystal structure. Amorphous silicon absorbs light more effectively than crystalline silicon, so the cells can be thinner. For this reason, amorphous silicon is also known as a "thin film" PV technology. Amorphous silicon can be deposited on a wide range of substrates, both rigid and flexible, which makes it ideal for curved surfaces and "fold-away" modules. Amorphous cells are, however, less efficient than crystalline based cells, with typical efficiencies of around 6%, but they are easier and therefore cheaper to produce. Their low cost makes them ideally suited for many applications where high efficiency is not required and low cost is important.

Other Thin Films: A number of other promising materials such as cadmium telluride (CdTe) and copper indium diselenide (CIS) are now being used for PV modules. The attraction of these technologies is that they can be manufactured by relatively inexpensive industrial processes, certainly in comparison to crystalline silicon technologies, yet they typically offer higher module efficiencies than amorphous silicon. New technologies based on the photosynthesis process are not yet on the market.

Why photovoltaic directly connected to the network?

The most appropriate would be to use photovoltaic panels directly connected to the network. The advantages of photovoltaic power connected to the network are generated by the lack of these battery systems. In this case is to store energy in the electricity it produces, which plays a battery of storage "infinite".

Essential components of photovoltaic power connected to the network are the following:

* Photovoltaic modules * Cables and Connectors * Synchronous Inverters

The advantages of the system "racordat network" in comparison with autonomous systems are the following:

* Operation of the entire energy supplied by photovoltaic panels, storage capacity is infinite network; * About the economy. 40% of investment (lack of batteries) * Minimum maintenance (batteries are those that require the greatest attention) * Life extension of the system * Pure energy due to the elimination recycling batteries

Today, we need to consider solutions of tomorrow ("for tomorrow it to be, because he does not belong to us but to the children, our grandchildren and great-grandchildren!").

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Science Technology Atomic Aircraft Trains

Solar energy Solar panels generate electricity by converting photons (packets of light energy) into an electric current. Strano's nanotube antenna boosts the number of photons that can be captured and transforms the light into energy that can be funneled into a solar cell. The antenna consists of a fibrous rope about 10 micrometers (millionths of a meter) long and four micrometers thick, containing about 30 million carbon nanotubes. Strano's team built, for the first time, a fiber made of two layers of nanotubes with different electrical properties -- specifically, different bandgaps. In any material, electrons can exist at different energy levels. When a photon strikes the surface, it excites an electron to a higher energy level, which is specific to the material. The interaction between the energized electron and the hole it leaves behind is called an exciton, and the difference in energy levels between the hole and the electron is known as the bandgap. The inner layer of the antenna contains nanotubes with a small bandgap, and nanotubes in the outer layer have a higher bandgap. That's important because excitons like to flow from high to low energy. In this case, that means the excitons in the outer layer flow to the inner layer, where they can exist in a lower (but still excited) energy state. Therefore, when light energy strikes the material, all of the excitons flow to the center of the fiber, where they are concentrated. Strano and his team have not yet built a photovoltaic device using the antenna, but they plan to. In such a device, the antenna would concentrate photons before the photovoltaic cell converts them to an electrical current. This could be done by constructing the antenna around a core of semiconducting material. The interface between the semiconductor and the nanotubes would separate the electron from the hole, with electrons being collected at one electrode touching the inner semiconductor, and holes collected at an electrode touching the nanotubes. This system would then generate electric current. The efficiency of such a solar cell would depend on the materials used for the electrode, according to the researchers. Strano's team is the first to construct nanotube fibers in which they can control the properties of different layers, an achievement made possible by recent advances in separating nanotubes with different properties. While the cost of carbon nanotubes was once prohibitive, it has been coming down in recent years as chemical companies build up their manufacturing capacity. "At some point in the near future, carbon nanotubes will likely be sold for pennies per pound, as polymers are sold," says Strano. "With this cost, the addition to a solar cell might be negligible compared to the fabrication and raw material cost of the cell itself, just as coatings and polymer components are small parts of the cost of a photovoltaic cell." Strano's team is now working on ways to minimize the energy lost as excitons flow through the fiber, and on ways to generate more than one exciton per photon. The nanotube bundles described in the Nature Materials paper lose about 13 percent of the energy they absorb, but the team is working on new antennas that would lose only 1 percent. [Massachusetts Institute of Technology (2010, September 13). Funneling solar energy: Antenna made of carbon nanotubes could make photovoltaic cells more efficient. ScienceDaily. Retrieved September 21, 2010, from http://www.sciencedaily.com¬ /releases/2010/09/100912151548.htm]

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