This article's lead section may be too short to adequately summarize the key points.(September 2022) |
Photovoltaic mounting systems (also called solar module racking) are used to fix solar panels on surfaces like roofs, building facades, or the ground. [1] These mounting systems generally enable retrofitting of solar panels on roofs or as part of the structure of the building (called BIPV). [2] As the relative costs of solar photovoltaic (PV) modules has dropped, [3] the costs of the racks have become more important and for small PV systems can be the most expensive material cost. [4] This has caused an interest in small users deploying a DIY approach. [5] Due to these trends, there has been an explosion of new racking trends. These include non-optimal orientations and tilt angles, new types of roof-mounts, ground mounts, canopies, building integrated, shading, vertical mounted and fencing systems.
A solar cell performs the best (most energy per unit time) when its surface is perpendicular to the sun's rays, which change continuously over the course of the day and season (see: Sun path). It is a common practice to tilt a fixed PV module (without solar tracker) at the same angle as the latitude of array's location to maximize the annual energy yield of module. For example, rooftop PV module at the tropics provides highest annual energy yield when inclination of panel surface is close to horizontal direction. A study in the tropics showed that the orientation of low-slope rooftop PV has negligible impact on annual energy yield, but in the case of PV external sunshade applications, east façade and panel slope of 30–40° are the most suitable location and inclination. [6] Recent studies have shown non-optimal orientations such as east–west facing bifacial PV systems have some advantages. [7]
The solar array of a PV system can be mounted on rooftops, generally with a few inches gap and parallel to the surface of the roof. If the rooftop is horizontal, the array is mounted with each panel aligned at an angle. If the panels are planned to be mounted before the construction of the roof, the roof can be designed accordingly by installing support brackets for the panels before the materials for the roof are installed. The installation of the solar panels can be undertaken by the crew responsible for installing the roof. If the roof is already constructed, it is relatively easy to retrofit panels directly on top of existing roofing structures. For a small minority of roofs (often not built to code) that are designed so that it is capable of bearing only the weight of the roof, installing solar panels demands that the roof structure must be strengthened beforehand. In all cases of retrofits particular consideration to weather sealing is necessary There are many low-weight designs for PV systems that can be used on either sloped or flat roofs (e.g. plastic wedges or the PV-pod), most however, rely on a type of extruded aluminum rails (e.g. Unirac). Recently, tension-based PV racking solutions have been tested successfully that reduce weight and cost. [8] In some cases, converting to composition shingles, the weight of the removed roof materials can compensate the additional weight of the panels structure. The general practice for installation of roof-mounted solar panels include having a support bracket per hundred watts of panels. [9] [10]
Ground-mounted PV systems are usually large, utility-scale photovoltaic power stations. The PV array consist of solar modules held in place by racks or frames that are attached to ground-based mounting supports. [11] [12] In general, ground mounted PV systems can be at the optimal tilt angle and orientation (as compared to roof mounted systems that can be non-optimal particularly for retrofits).
Ground-based mounting supports include:
Ground mounts are normally consist of steel held in concrete with aluminum rails holding up aluminum modules. There are ground mounts at the residential and commercial levels, but the systems are simply smaller and the number of PV modules per column may be less (e.g. 3). [13] In some regions like North America there is evidence that wood-based ground mounted PV racking (both fixed tilt, [4] raised fixed tilt for trellis-based PV [14] and variable tilt [15] angles) can be less expensive than conventional metal racks. This is not true globally, as for example in Togo, metal racks still cost less per installed unit power even with a lower tilt angle allowing for smaller wood beams. [4] The relative price of wood to metal radically shifts the optimal PV racking material throughout the world. [16] This can change as wood prices have been very volatile. [17]
Solar panels can be mounted on elevated racking so they can share space with other land uses, such as parking lots. These can provide shade for cars and reduce additional land use, but considerably more expensive than conventional ground-mounted systems due to the more extensive steel posts, footings and racks, as well as additional labor costs. [18] [19] [20] This can be reduced somewhat by using lower cost building materials like wood. [21] PV canopies over parking lots can be used to provide electricity for charging electric vehicles. [22] There is substantial potential area for PV on parking lots. As for example, there is a potential 3.1 MW for PV and 100 EV charging stations per U.S. Walmart Supercenter. [23] Popular Science reports that solar canopies built above parking lots are an increasingly common sight around the U.S.— installed at university campuses, airports, and lots near commercial office buildings. [24] France, however, is requiring all large parking lots to be covered by solar panels. [25]
Different canopy structures can also be used for agrivoltaics.
Solar trackers increase the energy produced per module at the cost of mechanical complexity and increased need for maintenance. They sense the direction of the Sun and tilt or rotate the modules as needed for maximum exposure to the light. [26] [27]
Alternatively, fixed racks can hold modules stationary throughout the day at a given tilt (zenith angle) and facing a given direction (azimuth angle). Tilt angles equivalent to an installation's latitude are common. Some systems may also adjust the tilt angle based on the time of year. [28]
On the other hand, east- and west-facing arrays (covering an east–west facing roof, for example) are commonly deployed. Even though such installations will not produce the maximum possible average power from the individual solar panels, the cost of the panels is now usually cheaper than the tracking mechanism and they can provided more economically valuable power during morning and evening peak demands than north or south facing systems. [29]
Building-integrated photovoltaics (BIPV) are photovoltaic materials that are used to replace conventional building materials in parts of the building envelope such as the roof (tiles), skylights, or facades. They are increasingly being incorporated into the construction of new buildings as a principal or ancillary source of electrical power, although existing buildings may be retrofitted with BIPV modules as well. The advantage of integrated photovoltaics over more common non-integrated systems is that the initial cost can be offset by reducing the amount spent on building materials and labor that would normally be used to construct the part of the building that the BIPV modules replace. [30]
Building-adapted photovoltaics (BAPV) uses solar modules to create solar PV windows [31] and this way, also to retrofit existing building. There are several BIPV products (e.g. PV shingles) [32] [33] were PV make up all of the roof material and there are methods to convert conventional modules to roof slates. [34]
Solar panels can also be mounted as shade structures where the solar panels can provide shade instead of patio covers. The cost of such shading systems are generally different from standard patio covers, especially in cases where the entire shade required is provided by the panels. The support structure for the shading systems can be normal systems as the weight of a standard PV array is between 3 and 5 pounds/ft2. If the panels are mounted at an angle steeper than normal patio covers, the support structures may require additional strengthening. Other issues that are considered include:
Bifacial PV modules can be installed vertically and operated as a fence. For example, bifacial PV worked as an outer fence of the global loop in the EXPO 2005 Aichi, Japan. [35] PV systems can also be used for snow fences. [36] Monofacial PV can be metal zip-tied to existing fencing to make a very low cost PV rack. A study cataloged the types of fences and wind load calculations to determine the viability of fence-based racking throughout the U.S. and found fences could have at least one PV module between uprights for agricultural fences (sheep, goats, pigs, cows, and alpaca). [37] For fences microinverters had better performance when the cross-over fence length is under 30 m or when the system was designed with less than seven solar PV modules (e.g. gardens), whereas string inverters were a better selection for longer fences (e.g. farms). [38]
PV can also be mounted on or be part of sound barriers/ noise barriers. PV on noise barriers and has been around for since 1989 in Switzerland. There has been considerable not only on the PV module technology, but also in the construction of photovoltaic noise barriers (PVNB). [39] The installed capacity of PVNBs deployed on noise barriers in a single state is comparable to the installed capacities of the largest solar farms in the U.S. and yet due to the unique mounting of PVNB, such systems provide better land utilization ratios for energy production than conventional solar PV farms. [40] Because of reduced racking costs PVNB is one of the cheapest ways to implement large scale grid-connected PV installations. [41] There is now ample evidence that a wide range of PVNB systems work. [42]
Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially used for electricity generation and as photosensors.
A solar cell or photovoltaic cell is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect. It is a form of photoelectric cell, a device whose electrical characteristics vary when it is exposed to light. Individual solar cell devices are often the electrical building blocks of photovoltaic modules, known colloquially as "solar panels". Almost all commercial PV cells consist of crystalline silicon, with a market share of 95%. Cadmium telluride thin-film solar cells account for the remainder. The common single-junction silicon solar cell can produce a maximum open-circuit voltage of approximately 0.5 to 0.6 volts.
A solar panel is a device that converts sunlight into electricity by using photovoltaic (PV) cells. PV cells are made of materials that produce excited electrons when exposed to light. The electrons flow through a circuit and produce direct current (DC) electricity, which can be used to power various devices or be stored in batteries. Solar panels are also known as solar cell panels, solar electric panels, or PV modules.
A solar tracker is a device that orients a payload toward the Sun. Payloads are usually solar panels, parabolic troughs, Fresnel reflectors, lenses, or the mirrors of a heliostat.
Solar shingles, also called photovoltaic shingles, are solar panels designed to look like and function as conventional roofing materials, such as asphalt shingle or slate, while also producing electricity. Solar shingles are a type of solar energy solution known as building-integrated photovoltaics (BIPV).
Building-integrated photovoltaics (BIPV) are photovoltaic materials that are used to replace conventional building materials in parts of the building envelope such as the roof, skylights, or façades. They are increasingly being incorporated into the construction of new buildings as a principal or ancillary source of electrical power, although existing buildings may be retrofitted with similar technology. The advantage of integrated photovoltaics over more common non-integrated systems is that the initial cost can be offset by reducing the amount spent on building materials and labor that would normally be used to construct the part of the building that the BIPV modules replace. In addition, BIPV allows for more widespread solar adoption when the building's aesthetics matter and traditional rack-mounted solar panels would disrupt the intended look of the building.
A photovoltaic system, also called a PV system or solar power system, is an electric power system designed to supply usable solar power by means of photovoltaics. It consists of an arrangement of several components, including solar panels to absorb and convert sunlight into electricity, a solar inverter to convert the output from direct to alternating current, as well as mounting, cabling, and other electrical accessories to set up a working system. Many utility-scale PV systems use tracking systems that follow the sun's daily path across the sky to generate more electricity than fixed-mounted systems.
Thin-film solar cells are a type of solar cell made by depositing one or more thin layers of photovoltaic material onto a substrate, such as glass, plastic or metal. Thin-film solar cells are typically a few nanometers (nm) to a few microns (μm) thick–much thinner than the wafers used in conventional crystalline silicon (c-Si) based solar cells, which can be up to 200 μm thick. Thin-film solar cells are commercially used in several technologies, including cadmium telluride (CdTe), copper indium gallium diselenide (CIGS), and amorphous thin-film silicon.
Photovoltaic thermal collectors, typically abbreviated as PVT collectors and also known as hybrid solar collectors, photovoltaic thermal solar collectors, PV/T collectors or solar cogeneration systems, are power generation technologies that convert solar radiation into usable thermal and electrical energy. PVT collectors combine photovoltaic solar cells, which convert sunlight into electricity, with a solar thermal collector, which transfers the otherwise unused waste heat from the PV module to a heat transfer fluid. By combining electricity and heat generation within the same component, these technologies can reach a higher overall efficiency than solar photovoltaic (PV) or solar thermal (T) alone.
The Blue Wing Solar Project is a 16.6 MWp (14.4 MWAC) solar photovoltaic (PV) power plant in San Antonio, Texas. It was one of the largest PV facilities in Texas when it came online in late 2010 and is owned by a Duke Energy Subsidiary.
A rooftop solar power system, or rooftop PV system, is a photovoltaic (PV) system that has its electricity-generating solar panels mounted on the rooftop of a residential or commercial building or structure. The various components of such a system include photovoltaic modules, mounting systems, cables, solar inverters battery storage systems, charge controllers, monitoring systems, racking and mounting systems, energy management systems, net metering systems, disconnect switches, grounding equipment, protective devices, combiner boxes, weatherproof enclosures and other electrical accessories.
A photovoltaic power station, also known as a solar park, solar farm, or solar power plant, is a large-scale grid-connected photovoltaic power system designed for the supply of merchant power. They are different from most building-mounted and other decentralized solar power because they supply power at the utility level, rather than to a local user or users. Utility-scale solar is sometimes used to describe this type of project.
The Open Solar Outdoors Test Field (OSOTF) is a project organized under open-source principles, which is a fully grid-connected test system that continuously monitors the output of many solar photovoltaic modules and correlates their performance to a long list of highly accurate meteorological readings.
Joshua M. Pearce is an academic engineer at Western University known for his work on protocrystallinity, photovoltaic technology, agrivoltaics, open-source-appropriate technology, and open-source hardware including RepRap 3D printers and recyclebots.
Agrivoltaics is the dual use of land for solar energy production and agriculture. The technique was first conceived by Adolf Goetzberger and Armin Zastrow in 1981.
Floating solar or floating photovoltaics (FPV), sometimes called floatovoltaics, are solar panels mounted on a structure that floats on a body of water, typically a reservoir or a lake such as drinking water reservoirs, quarry lakes, irrigation canals or remediation and tailing ponds.
There are many practical applications for solar panels or photovoltaics. From the fields of the agricultural industry as a power source for irrigation to its usage in remote health care facilities to refrigerate medical supplies. Other applications include power generation at various scales and attempts to integrate them into homes and public infrastructure. PV modules are used in photovoltaic systems and include a large variety of electrical devices.
A bifacial solar cell (BSC) is any photovoltaic solar cell that can produce electrical energy when illuminated on either of its surfaces, front or rear. In contrast, monofacial solar cells produce electrical energy only when photons impinge on their front side. Bifacial solar cells can make use of albedo radiation, which is useful for applications where a lot of light is reflected on surfaces such as roofs. The concept was introduced as a means of increasing the energy output in solar cells. Efficiency of solar cells, defined as the ratio of incident luminous power to generated electrical power under one or several suns (1 sun = 1000W/m2 ), is measured independently for the front and rear surfaces for bifacial solar cells. The bifaciality factor (%) is defined as the ratio of rear efficiency in relation to the front efficiency subject to the same irradiance.
Soiling is the accumulation of material on light-collecting surfaces in solar power systems. The accumulated material blocks or scatters incident light, which leads to a loss in power output. Typical soiling materials include mineral dust, bird droppings, fungi, lichen, pollen, engine exhaust, and agricultural emissions. Soiling affects conventional photovoltaic systems, concentrated photovoltaics, and concentrated solar (thermal) power. However, the consequences of soiling are higher for concentrating systems than for non-concentrating systems. Note that soiling refers to both the process of accumulation and the accumulated material itself.
Solar canopies are solar arrays installed on canopies, which could be a parking lot canopy, carport, gazebo, Pergola, or patio cover.
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