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PV Applications & Types

Sunlight is abundant and it is everywhere. More and more emphasis on the use of this abundant energy source has led to the maximum development in this field. The solar energy can be utilized through various means form building concentrating solar power systems, photovoltaic, solar heating systems , solar cars, solar batteries, solar satellite systems , solar updraft power houses and solar lighting systems. Concentrate solar power systems use mirrors and lenses to store light and heat carrying photons. Photovoltaic effect can be used by deploying solar cells. Solar lighting system can be used by designing the architecture to support day lighting procedure. Solar lighting reduces the load and dependence on electric lighting systems. Solar cars contain e solar panels installed on the roof top of the car. These solar panels convert the sunlight into electric charge and furthermore it can be stored into battery to be used later on. Solar updraft power plants are another addition in the application of the solar energy. These power houses are designed to support the heating of air through sunrays. This hot air rises to the tower and then it runs the turbines to support electricity generation. Solar power satellite is an expensive way to produce electricity form unhindered sunlight day and night.

Solar Power Systems

Depending upon your needs and where you live, there are a variety of solar power systems that could work for you.

Solar Power System

Solar Power Systems – Grid-Tied (On Grid)

Most people install grid-tied solar power systems -most often in cities, suburbs and industrial areas where access to utility-generated power is available. You can supplement your solar powered electricity with utility-generated energy if you use more electricity than the solar power system supplies.

When your solar power system produces more electricity you need, you can sell the excess to the PG&E, who delivers the clean, renewable energy to other customers. Consequently, the good you do for the environment doesn’t stop at your home or office. Even neighbors without solar power can draw upon the renewable energy of the sun – while you bank credit to offset the utility-generated power you use at night.

Grid Tied Solar Power System

Solar Power Systems – Grid-Tied with Battery Backup

Solar energy panels combined with batteries and generators for grid-tie applications couple the clean, power supplied by solar panels with the assurance that you will have electricity even during power outages that last for extended periods. During the day, the solar panels generate electricity as needed and charges batteries. If more power is required, or the batteries begin to run low, the natural gas or propane generator kicks in to recharge the batteries. It automatically shuts off when the batteries are fully charged.

Grid Connected with Battery Bank

Solar Power Systems – Off-Grid

Standalone, or off-grid, solar power systems consist of solar panels and a battery bank. They are typically used in rural areas and regions where there is no access to the utility grid. They may also be appropriate where the grid is somewhat close to the site, but expensive to bring in – for example, across a neighbor’s property. We have installed a number of systems with battery back-up where the grid is available but where the homeowner has experienced unreliable power in the past or believes that he/she will be subject to power outages in the future. We have seen a number of property owners install battery back-up system just for philosophical reasons, for the desire to be independent of the grid and the “gaming” to which utility companies and their power suppliers have subjected customers in the past.

It may cost you as high as $50 per foot to bring utility power to your property, after which you’ll continue to pay for power forever. It’s often less expensive to add a solar energy system from the start and be your own power company. You can add the solar power system cost to your mortgage, reducing the combined costs of mortgage and utility bills.

Off Grid System

When your off-grid solar power system produces excess electricity during the day, it is used to charge the batteries. When the sun’s not shining, electricity is drawn from the batteries to power the home or business. The advantage is greater independence for you. The disadvantage is greater complexity and cost.

Solar Power System – Direct DC

Simple, direct DC solar power systems produce energy where and when it’s needed. Common uses include powering water pumps and fans. There is no complex wiring, so storage and control systems aren’t required. Small systems are easy to transport and install.

Solar Power Solutions (DC System)

Hybrid Power Systems

Hybrid power systems combine various sources of electrical generation, and are well suited for electrification. Solar and wind technologies are modular, and seasonal variations of sun and wind often complement each other.

Hybrid System    

Solar Cell & Photovoltaic Modules

Photovoltaic (PV) Power

PV is emerging as a major power resource, steadily becoming more affordable and proving to be more reliable than utilities. Photovoltaic power promises a brighter, cleaner future for our children.

In 1839, Edmund Becquerel discovered the process of using sunlight to produce an electric current in a solid material, but it wasn’t until a century later that scientists eventually learned that the photovoltaic effect caused certain materials to convert light energy into electrical energy.

The photovoltaic effect is the basic principal process by which a PV cell converts sunlight into electricity. When light shines on a PV cell, it may be reflected, absorbed, or pass right through. The absorbed light generates electricity.

In the early 1950s, photovoltaic (PV) cells were developed as a spin-off of transistor technology. Very thin layers of pure silicon are impregnated with tiny amounts of other elements. When exposed to sunlight, small amounts of electricity are produced. Originally this technology was a costly source of power for satellites but it has steadily come down in price making it affordable to power homes and businesses.

  • Cells Semiconductor device that converts sunlight into direct current (DC) electricity
  • Modules PV modules consist of PV cell circuits sealed in an environmentally protective laminate and are the fundamental building block of PV systems
  • Panels PV panels include one or more PV modules assembled as a pre-wired, field-installable unit
  • Array A PV array is the complete power-generating unit, consisting of any number of PV modules and panels

Photovoltaic Cell

A single PV cell is a thin semiconductor wafer made of two layers generally made of highly purified silicon (PV cells can be made of many different semiconductors but crystalline silicon is the most widely used). The layers have been doped with boron on one side and phosphorous on the other side, producing surplus of electrons on one side and a deficit of electrons on the other side.

When the wafer is bombarded by sunlight, photons in the sunlight knock off some of excess electrons, this makes a voltage difference between the two sides as the excess electrons try to move to the deficit side. In silicon this voltage is 0.5 volt

Metallic contacts are made to both sides of the semiconductor. With an external circuit attached to the contacts, the electrons can get back to where they came from and a current flows through the circuit. This PV cell has no storage capacity, it simply acts as an electron pump.

The amount of current is determined by the number of electrons that the solar photons knock off. Bigger cells, more efficient cells, or cells exposed to more intense sunlight will deliver more electrons.

Photovoltaic Modules

A PV module consists of many PV cells wired in parallel to increase current and in series to produce a higher voltage. 36 cell modules are the industry standard for large power production.

The module is encapsulated with tempered glass (or some other transparent material) on the front surface, and with a protective and waterproof material on the back surface. The edges are sealed for weatherproofing, and there is often an aluminum frame holding everything together in a mountable unit. In the back of the module there is a junction box, or wire leads, providing electrical connections.

Types of PV Modules

Monocrystalline Silicon Panels: Monocrystalline (or single-crystal) silicon solar panels have a return electricity rate of anywhere from 14% to 18%. These panels are made from one continuous sheet of silicon that has pieces of metal nailed to the edges to increase the conductivity and to excite the electrons.

Monocrystalline panels are more expensive than some of the other types of solar panels that you can buy but they are also more effective, so in the long run you’re better off buying these panels if you can afford the up front cost.

Polycrystalline Silicon Panels: Polycrystalline (or multi-crystal) silicon panes have an electricity return rate of about 12%-14% so they are less efficient than monocrystalline silicon solar panels. These panels are made up of lots of individual PV cells that have metal conducting materials nailed to the sides that will help excite the electrons and also connect the cells together.

Polycrystalline silicon panels are the cheapest solar panels to produce so they are usually the cheapest for consumers to buy. The maintenance costs of polycrystalline silicon panels is lower than the maintenance cost of monocrystalline solar panels because if one of the cells on a polycrystalline panel is damaged you can have the individual cell replaced without having to replace the entire panel.

String Ribbon Silicon Panels:  String ribbon silicon panels are made in a similar way to the polycrystalline silicon panels and have about the same electricity return rate. The difference between string ribbon silicon panels and polycrystalline silicon panels is that the PV cells in a string ribbon panel are made of strips of silicon attached to metal bars that connect the strips to form a cell. Using strips of silicon to form the cell instead of using one solid square of silicon make the production cost of string ribbon silicon panels a bit lower than the production cost of polycrystalline silicon panels.

Amorphous Silicon Panels:  Amorphous silicon panels have the lowest electricity return rate of any type of solar panels. Traditionally amorphous silicon solar panels have an electricity return rate of between 5%-6%. That’s because these panels aren’t made with crystalline silicon. They are composed of a piece of semi conductive metal, like copper, with a thin silicon film over the top that is attached to some metal pieces.

These panels are very cheap to produce but when you’re buying solar panels for home use you need to consider the long term efficiency of the type of panel that you’re buying. Unfortunately, though cheap to begin with they do not produce much energy, therefore amorphous silicon panels are not going to be cost effective in the long run.

Photovoltaic Panels

PV panels include one or more PV modules assembled as a pre-wired, field-installable unit. The modular design of PV panels allows systems to grow as needs change. Modules of different manufacture can be intermixed without any problem, as long as all the modules have rated voltage output within 1.0 volt difference.

Solar panels generate free power from the sun by converting sunlight to electricity with no moving parts, zero emissions, and no maintenance. The solar panel, the first component of a electric solar energy system, is a collection of individual silicon cells that generate electricity from sunlight. The photons (light particles) produce an electrical current as they strike the surface of the thin silicon wafers. A single solar cell produces only about 1/2 (.5) of a volt. However, a typical 12 volt panel about 25 inches by 54 inches will contain 36 cells wired in series to produce about 17 volts peak output. If the solar panel can be configured for 24 volt output, there will be 72 cells so the two 12 volt groups of 36 each can be wired in series, usually with a jumper, allowing the solar panel to output 24 volts. When under load (charging batteries for example), this voltage drops to 12 to 14 volts (for a 12 volt configuration) resulting in 75 to 100 watts for a panel of this size.

Multiple solar panels can be wired in parallel to increase current capacity (more power) and wired in series to increase voltage for 24, 48, or even higher voltage systems. The advantage of using a higher voltage output at the solar panels is that smaller wire sizes can be used to transfer the electric power from the solar panel array to the charge controller & batteries. Since copper has gone up considerably in the last few years, purchasing large copper wiring and cables is quite expensive.

Solar Panels

Photovoltaic Array

A PV Array consists of a number of individual PV modules or panels that have been wired together in a series and/or parallel to deliver the voltage and amperage a particular system requires. An array can be as small as a single pair of modules, or large enough to cover acres.

12 volt module is the industry standard for battery charging. Systems processing up to about 2000 watt-hours should be fine at 12 volts. Systems processing 2000 – 7000 watt-hours will function better at 24 volt. Systems running more than 7000 watt-hours should probably be running at 48 volts.

Photovoltaic Module Performance

The performance of PV modules and arrays are generally rated according to their maximum DC power output (watts) under Standard Test Conditions (STC). Standard Test Conditions are defined by a module (cell) operating temperature of 25o C (77 F), and incident solar irradiant level of 1000 W/m2 and under Air Mass 1.5 spectral distribution. Since these conditions are not always typical of how PV modules and arrays operate in the field, actual performance is usually 85 to 90 percent of the STC rating.

Today’s photovoltaic modules are extremely safe and reliable products, with minimal failure rates and projected service lifetimes of 20 to 30 years. Most major manufacturers offer warranties of twenty or more years for maintaining a high percentage of initial rated power output. When selecting PV modules, look for the product listing (UL), qualification testing and warranty information in the module manufacturer’s specifications.

Solar Power System

Solar Photovoltaic Technology

A photovoltaic cell (PV cell) is a specialized semiconductor diode that converts visible light into direct current (DC). Some PV cells can also convert infrared (IR) or ultraviolet (UV) radiation into DC electricity. Photovoltaic cells are an integral part of solar-electric energy systems, which are becoming increasingly important as alternative sources of utility power. The first PV cells were made of silicon combined, or doped, with other elements to affect the behavior of electrons or holes (electron absences within atoms). Other materials, such as copper indium diselenide (CIS), cadmium telluride (CdTe), and gallium arsenide (GaAs), have been developed for use in PV cells. There are two basic types of semiconductor material, called positive (or P type) and negative (or N type). In a PV cell, flat pieces of these materials are placed together, and the physical boundary between them is called the P-N junction. The device is constructed in such a way that the junction can be exposed to visible light, IR, or UV. When such radiation strikes the P-N junction, a voltage difference is produced between the P type and N type materials. Electrodes connected to the semiconductor layers allow current to be drawn from the device.

Solar Cell

Solar Cell Working

Photovoltaic Technology Solar cells, also called photovoltaic (PV) cells by scientists, convert sunlight directly into electricity. PV gets its name from the process of converting light (photons) to electricity (voltage), which is called the PV effect. The PV effect was discovered in 1954, when scientists at Bell Telephone discovered that silicon (an element found in sand) created an electric charge when exposed to sunlight. Soon solar cells were being used to power space satellites and smaller items like calculators and watches. Today, thousands of people power their homes and businesses with individual solar PV systems. Utility companies are also using PV technology for large power stations. Solar panels used to power homes and businesses are typically made from solar cells combined into modules that hold about 40 cells. A typical home will use about 10 to 20 solar panels to power the home. The panels are mounted at a fixed angle facing south, or they can be mounted on a tracking device that follows the sun, allowing them to capture the most sunlight. Many solar panels combined together to create one system is called a solar array. For large electric utility or industrial applications, hundreds of solar arrays are interconnected to form a large utility-scale PV system. Traditional solar cells are made from silicon, are usually flat-plate, and generally are the most efficient. Second-generation solar cells are called thin-film solar cells because they are made from amorphous silicon or nonsilicon materials such as cadmium telluride. Thin film solar cells use layers of semiconductor materials only a few micrometers thick. Because of their flexibility, thin film solar cells can double as rooftop shingles and tiles, building facades, or the glazing for skylights. Third-generation solar cells are being made from variety of new materials besides silicon, including solar inks using conventional printing press technologies, solar dyes, and conductive plastics. Some new solar cells use plastic lenses or mirrors to concentrate sunlight onto a very small piece of high efficiency PV material. The PV material is more expensive, but because so little is needed, these systems are becoming cost effective for use by utilities and industry. However, because the lenses must be pointed at the sun, the use of concentrating collectors is limited to the sunniest parts of the country. How do Photovoltaics Work? Photovoltaics is the direct conversion of light into electricity at the atomic level. Some materials exhibit a property known as the photoelectric effect that causes them to absorb photons of light and release electrons. When these free electrons are captured, an electric current results that can be used as electricity. The photoelectric effect was first noted by a French physicist, Edmund Bequerel, in 1839, who found that certain materials would produce small amounts of electric current when exposed to light. In 1905, Albert Einstein described the nature of light and the photoelectric effect on which photovoltaic technology is based, for which he later won a Nobel prize in physics. The first photovoltaic module was built by Bell Laboratories in 1954. It was billed as a solar battery and was mostly just a curiosity as it was too expensive to gain widespread use. In the 1960s, the space industry began to make the first serious use of the technology to provide power aboard spacecraft. Through the space programs, the technology advanced, its reliability was established, and the cost began to decline. During the energy crisis in the 1970s, photovoltaic technology gained recognition as a source of power for non-space applications.

Operation of Photovoltaics

The diagram above illustrates the operation of a basic photovoltaic cell, also called a solar cell. Solar cells are made of the same kinds of semiconductor materials, such as silicon, used in the microelectronics industry. For solar cells, a thin semiconductor wafer is specially treated to form an electric field, positive on one side and negative on the other. When light energy strikes the solar cell, electrons are knocked loose from the atoms in the semiconductor material. If electrical conductors are attached to the positive and negative sides, forming an electrical circuit, the electrons can be captured in the form of an electric current — that is, electricity. This electricity can then be used to power a load, such as a light or a tool. [youtube]http://www.youtube.com/watch?v=2mCTSV2f36A&feature=player_embedded[/youtube] Continue reading Solar Photovoltaic Technology