Solar panel

Solar panels absorb the sunlight as a source of energy to generate electricity or heat .

A photovoltaic (PV) module is a packaged, connect assembly of typically 6×10 photovoltaic solar cells . Photovoltaic modules constitute the photovoltaic array of a photovoltaic system that supplies solar electricity in commercial and residential applications. Each module is rated by its DC output power under standard test conditions (STC), and typically ranges from 100 to 365 Watts (W) . The efficiency of a module determines the area of ​​a module given the same rated output – an 8% efficient 230 W module will have the area of ​​a 16% efficient 230 W module. There are a few commercially available solar modules that exceed efficiency of 22%[1] and reportedly also exceeding 24%. [2] [3] A single solar module can only produce a limited amount of power; most installations contain multiple modules. A photovoltaic system typically includes an array of photovoltaic modules, an inverter , abattery pack for storage, an interconnection wiring, and optionally a solar tracking mechanism.

The most common application of solar panels is solar water heating systems. [4]

The price of solar power has been reduced to that of ordinary fossil fuel electricity from the grid (there is ” grid parity “). [5]

Theory and construction

Photovoltaic modules use light energy ( photons ) from the Sun to generate electricity through the photovoltaic effect . The majority of modules use wafer -based crystalline silicon cells or thin-film cells . The structural ( load carrying ) member of a module can be the top layer or the back layer. Cells must also be protected from mechanical damage and moisture. Most modules are rigid, but semi-flexible ones are available, based on thin-film cells. The cells must be connected electrically in series, one to another. Externally, most of photovoltaic modules use MC4 connectors type to facilitate easy weatherproof connections to the rest of the system.

Modules electrical connections are made in series to achieve achievement has gold Desired voltage output in parallel to Provide a Desired current capability. The conducting wires may take the form of a non-magnetic conductive transition metals. Bypass diodes can be used externally, in case of partial module shading, to maximize the output of modules still illuminated sections.

Some special solar PV modules include concentrators in which light is focused by lenses or mirrors onto smaller cells. This enables the use of cells with a high cost per unit area (such as gallium arsenide ) in a cost-effective way.

Efficiencies

Depending on construction, photovoltaic modules can produce electricity from a range of frequencies of light , but usually does not cover the entire solar range (specifically, ultraviolet , infrared and low light diffused light). Hence, much of the sunlight energy incident is wasted by solar modules, and they can give far greater efficiencies if illuminated with monochromatic light. Therefore, another design concept is to split the light into different wavelength ranges. citation needed ] This has been projected to be able of raising efficiency by 50%. Scientists from Spectrolab, a subsidiary ofBoeing , Reported-have development of multi-junction solar cells with an efficiency of more than 40%, a new world record for solar photovoltaic cells. [6] The Spectrolab scientists could predict that solar cells could be more efficient than 45% or even 50% in the future, with their efficiencies being about 58% in cells with more than three junctions.

Currently, the best achieves sunlight conversion rate (solar module efficiency) is around 21.5% in new commercial products [7] typically less than the efficiencies of their cells in isolation. The most efficient mass-produced solar modules disputed – discuss ] have power density of up to 175 W / m 2 (16.22 W / ft 2 ). [8] Research by Imperial College, London has shown that the efficiency of a solar panel can be improved by receiving the light-receiving semiconductor surface with aluminum nanocylinders similar to the ridges on Lego blocks . Teascattered light then travels along a path in which the photons can be absorbed and converted into current. ALTHOUGH thesis nanocylinders-have-been Previously used (aluminum Was Preceded by gold and silver), the light scattering occurred in the near infrared region and visible light was absorbed strongly. Aluminum has been found to be absorbed by the ultraviolet part of the spectrum, while the aluminum surface has been exposed to aluminum. This, the research argued, could be more cost effective and more efficient than aluminum and silver. The research also noted that the increase in current makes thinner film solar panels technically feasible without “compromising power conversion efficiencies, thus reducing material consumption”. [9]

  • Efficiencies of solar panel can be calculated by MPP (maximum power point) value of solar panels
  • Solar inverters convert the DC power to AC power by performing MPPT process: solar power inverter the power output (IV curve) from the solar cell and the proper resistance (load) to solar cells to obtain maximum power.
  • MPP (Maximum power point) of the solar panel consists of MPP voltage (V mpp) and MPP current (I mpp): it is a capacity of the solar panel and the higher value can make higher MPP.

Micro-inverted solar panels are wired in parallel , which produces more output than normal panels which are wired in series with the output of the series determined by the lowest performing panel (this is known as the “Christmas light effect”). Micro-inverters work independently of each other’s contribution to the maximum possible output given the available sunlight. [10]

Technology

Most solar modules are currently produced from crystalline silicon (c-Si) solar cells made from multicrystalline and monocrystalline silicon . In 2013, crystalline silicon Accounted for more than 90 percent of worldwide PV production while the rest of the overall market is made up of thin film technologies using cadmium telluride , CIGS and amorphous silicon [11] Emerging, third generation solar technology uses advanced thin-film cells. They produce a relatively high-efficiency conversion for the low cost compared to other solar technologies. Also, high-cost, high-efficiency, and close-packed rectangularmulti-junction (MJ) cells are preferably used in solar panels on spacecraft , as they offer the highest ratio of generated power per kilogram lifted into space. MJ-cells are compound semiconductors and gallium arsenide (GaAs) and other semiconductor materials. Another emerging PV technology using MJ-cells is concentrator photovoltaics (CPV).

Thin movie

In rigid thin-film modules , the cell and the module are manufactured in the same production line. The cell is created on a glass substrate or superstrate, and the electrical connections are created in situ , so-called “monolithic integration”. The substrate is usually laminated with an encapsulant to a front or back sheet , usually another sheet of glass. The main cell technologies in this category are CdTe , or a-Si , or a-Si + uc-Si tandem , or CIGS (or variant). Amorphous silicon has a sunlight conversion rate of 6-12%

Flexible thin film cells and modules are provided on the same production line by the photoactive layer and other necessary layers on a flexible substrate . If the substrate is an insulator (eg polyester or polyimide film) then monolithic integration can be used. If it is a conductor then another technique for electrical connection must be used. The cells are assembled by laminating them to a transparent colored fluoropolymer on the front side (typically ETFE or FEP ) and a polymer suitable for bonding to the final substrate on the other side.

Smart solar modules

Main items: Smart module and Solar micro-inverter

Several companies have begun embedding electronics into PV modules. This facility performs maximum power tracking (MPPT) for each module individually, and the measurement of performance data for monitoring and fault detection at module level. Some of these solutions make use of power optimizers , a DC-to-DC converter technology developed to maximize the power of solar photovoltaic systems. As of about 2010, such electronics can also compensate for shading the effects of a module. entire module fall to zero.

Performance and degradation

STC: irradiance of 1,000 W / m 2 , solar spectrum of AM 1.5 and temperature modulus at 25 ° C.

Electrical characteristics include nominal power (P MAX , measured in W ), open circuit voltage (V OC ), short circuit current (I SC , measured in amperes ), maximum power voltage (V MPP ), maximum power current (I MPP ), peak power, ( watt-peak , W p ), and module efficiency (%).

Nominal voltage [12] refers to the voltage of the battery that the module is best suited to charge; This module was only used when solar modules were only used to charge batteries. The actual voltage output of the module changes as lighting, temperature and load conditions change, so it is never a specific voltage. Nominal voltage allows users, at a glance, to make sure the module is compatible with a given system.

Open circuit voltage or V OC is the maximum voltage that the module can produce when not connected to an electrical circuit or system. V OC can be measured with a voltmeter directly on an illuminated module’s terminals or on its disconnected cable.

The peak power rating, W p , is the maximum output under standard test conditions (not the maximum possible output). Typical modules, which could measure approximately 1 m × 2 m or 3 ft 3 in × 6 ft 7 in, will be rated as low as 75 W to as high as 350 W, depending on their efficiency. At the time of testing, the test modules are tested in the following manner, and at a rate of at least 3%, +/- 5%, + 3%. -0% gold + 5 / -0%. [13] [14] [15] [16]

The Ability of solar modules to Withstand damage by rain, hail , heavy snow load, and cycles of heat and cold varies by manufacturer. Many crystalline silicon manufacturers offer a limited warranty of 10 years at 90% of rated power output and 25 years at 80%. [17] Installations intended to withstand extreme environments like large hail or heavy snow will require extra protection in the form of steep facilities, sturdy framing and stronger glazing. [18]

Potential induced degradation (also called PID) is a potential induced performance degradation in crystalline photovoltaic modules, caused by so-called stray currents. [19] This effect can cause power loss of up to 30%. [20]

The largest challenge for photovoltaic technology is to produce electricity, new materials and manufacturing techniques to improve performance. The problem resides in the enormous activation energy that must be overcome for a photon to excite an electron for harvesting purposes. Advancements in photovoltaic technologies have brought about the process of “doping” the silicon substrate to the activation of energy, making the panel more efficient in converting photons to retrievable electrons. [21] Chemicals Such As Boron (p-type) are applied into the semiconductor crystal in order to create donor and acceptor energy levels Substantially closer to the valence and conductor bands .[22] In doing so, the addition of Boron impurity enables the activation of energy to decrease from 1.12 eV to 0.05 eV. Since the potential difference (E B ) is so low, the Boron is able to thermally ionize at room temperatures. This allows for free energy in the conduction and valence bands, and allows for greater conversion of photons to electrons.

Solar power allows for greater efficiency than heat, such as the generation of energy in heat engines. The drawback with heat is what is most of the heat created is lost to the surroundings. Thermal efficiency is as defined:

{\ displaystyle \ eta _ {th} \ equiv {\ frac {W_ {out}} {Q_ {in}}} = 1 – {\ frac {Q_ {out}} {Q_ {in}}}}

Due to the inherent irreversibility of heat production, the efficiency levels are decreased. On the other hand, with solar panels is not a requirement to retain any heat, and there are no drawbacks such as friction.

Maintenance

Solar panel conversion efficiency, typically in the 20% range, is reduced by dust, grime, pollen, and other particles that accumulate on the solar panel. “Seamus Curran, associate professor of physics at the University of Houston and director of the Institute for NanoEnergy, who specializes in the design, engineering, and assembly of nanostructures. [23]

Paying to have solar panels is often not a good investment; found that had not been cleaned, or lost, in California, lost only 7.4% of their efficiency. Overall, for a typical residential solar system of 5 kW, washing panels halfway through the summer would translate into a $ 20 gain in electricity production until the summer drought ends-in about 2 ½ months. For larger commercial rooftop systems, the financial losses are bigger but still less expensive than the cost of washing the panels. On average, panels lost a little less than 0.05% of their overall efficiency per day. [24]

Recycling

Most parts of a solar module can be recycled to up to 95% of certain types of ferrous metals and non-ferrous metals. [25] Some private companies and non-profit organizations are involved in take-back and recycling operations for end-of-life modules. [26]

Recycling possibilities depend on the type of technology used in the modules:

  • Silicon based modules: Aluminum frames and junction boxes are dismantled manually at the beginning of the process. The module is then crushed in a mill and the different fractions are separated – glass, plastics and metals. [27] It is possible to recover more than 80% of the incoming weight. [28] This process can be performed by flat glass recyclers and the use of plastics in the building and automotive industry. The recovered glass for example.
  • Non-silicon based modules: they require specific recycling technologies such as the use of chemical baths in different materials. [29] For cadmium telluride modules, the recycling process begins by crushing the module and subsequently separating the different fractions. This recycling process is designed to recover to 90% of the glass and 95% of the semiconductor materials contained. [30] Some commercial-scale recycling facilities have been created in recent years by private companies. [31]

Since 2010, there is an annual European meeting of manufacturers, recyclers and researchers to look at the future of PV module recycling. [32] [33]

Production

See also: List of photovoltaics companies
Top Module Producer Shipments in 2014 ( MW )
Yingli 3,200
Trina Solar 2,580
Sharp Solar 2,100
Canadian Solar 1,894
Jinko Solar 1,765
ReneSola 1,728
First Solar 1,600
Hanwha SolarOne 1,280
Kyocera 1,200
JA Solar 1,173

In 2010, 15.9 GW of solar PV systems were completed, with solar PV pricing survey and market research company PVinsights reporting growth of 117.8% in solar PV installation on a year-on-year basis.

With over 100% year-on-year growth in PV system installation, the PV module makers dramatically increased their shipments of solar modules in 2010. They actively expanded their capacity and turned themselves into gigawatt GW players. [34] According to PVinsights, five of the top ten PV modules companies in 2010 are GW players. Suntech, Solar First, Sharp, Yingli and Trina Solar are GW producers now, and most of them doubled their shipments in 2010. [35]

The basis of producing solar panels revolves around the use of silicon cells. [36] These silicon cells are typically 10-20% efficient [37] and up to 22%. [38]

In order to solar panels to become more efficient, researchers across the world have tried to develop new technologies to make solar panels. [39]

In 2014, the world’s top ten solar module manufacturers were Trina Solar , Yingli , Sharp Solar and Canadian Solar . [40]

Price

Average price information divides in three pricing categories: those buying small quantities (average price of each year in the kilowatt range), mid-range buyers (typically up to 10 MWpannually), and large quantity buyers (self-explanatory and access) to the lowest prices). Over the long term there is clearly a reduction in the price of cells and modules. For example, in 2012 it was estimated that US $ 0.60, which was 250 times less than the cost in 1970 of US $ 150. [42] [43] A 2015 study shows price / kWh dropping by 10% per year since 1980, and predicted that it could contribute 20% of total electricity consumption by 2030, compared to the International Energy Agency predicts 16% by 2050.[44]

Real world energy production costs depend on a great deal on local weather conditions. In a cloudy country such as the United Kingdom, the cost per produced kWh is higher than in Spain.

Following to RMI , Balance-of-System (BoS) elements, this is, non-module cost of non- microinverter solar modules (as wiring, converters, racking systems and various components) make up about half of the total costs of installations.

For merchant solar power stations, where the electricity is being sold into the electricity transmission network, the cost of solar energy will need to match the wholesale electricity price. This point is sometimes called ‘wholesale grid parity’ or ‘busbar parity’. [5]

Some photovoltaic systems, such as rooftop installations, can supply power directly to an electricity user. In these cases, the installation can be competitive when the output costs the country at which the user pays for his electricity consumption. This situation is sometimes called ‘retail grid parity’, ‘socket parity’ or ‘dynamic grid parity’. [45] Research the carried out by UN-Energy in 2012 Suggests areas of sunny countries with high electricity prices, Such As Italy, Spain and Australia, and areas using diesel generators, atteint-have retail grid parity. [5]

Mounting and tracking

Ground mounted photovoltaic system are usually large, utility-scale solar power plants . Their solar modules are held in place by racks or frames. [46] [47] Ground based mounting supports include:

  • Pole mounts, which are driven directly into the ground or embedded in concrete.
  • Foundation mounts, such as slabs or poured jogging
  • Ballasted footing mounts, such as concrete or steel This type of mounting is more likely to be used when decommissioning or releasing solar module systems.

Roof-mounted solar power systems consist of solar modules held in place by racks or frames attached to roof-based mounting brackets. [48] Roof-based mounting supports include:

  • Pole mounts, which are attached directly to the roof structure and may use additional rails for attaching the module racking or frames.
  • Ballasted footing mounts, such as concrete or steel This method is suitable for decommissioning or relocation of solar panel systems with no adverse effect on the roof structure.
  • All wiring connecting adjacent solar modules to the energy harvesting equipment must be installed according to local electrical codes and should be

Solar trackers increase the amount of energy produced per module at a cost of mechanical complexity and need for maintenance. They sense the direction of the Sun and tilt or rotate the modules as needed for maximum exposure to the light. [49] [50] Alternatively, fixed racks hold stationary modules as the sun moves across the sky. The fixed rack sets the angle at which the module is held. Tilt angles equivalent to an installation’s latitude are common. Most of these fixed racks are set on poles above ground. [51] Panels that face West or East may provide a lower level of energy. [52]

Standards

Standards generally used in photovoltaic modules:

  • IEC 61215 ( crystalline silicon performance), 61646 ( thin film performance) and 61730 (all modules, safety)
  • ISO 9488 Solar energy-Vocabulary.
  • UL 1703 from Underwriters Laboratories
  • UL 1741 from Underwriters Laboratories
  • UL 2703 from Underwriters Laboratories
  • CE mark
  • Electrical Safety Tester (EST) Series (EST-460, EST-22V, EST-22H, EST-110).

Applications

There are many practical applications for the use of solar panels or photovoltaics. It can be used in agriculture as a source of irrigation. In health care solar panels can be used to refrigerate medical supplies. It can also be used for infrastructure. PV modules are used in photovoltaic systems and include a large variety of electric devices :

  • Photovoltaic power stations
  • Rooftop solar PV systems
  • Standalone PV systems
  • Solar hybrid power systems
  • Concentrated photovoltaics
  • Solar planes
  • Solar-pumped lasers
  • Solar vehicles
  • Solar panels on spacecraft and space stations

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