Photovoltaic mounting system
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
Orientation and inclination
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]
Mounting
Roof
The solar array of a
Ground
Ground-mounted
Ground-based mounting supports include:
- Pole mounts, which are driven directly into the ground or embedded in concrete.
- Foundation mounts, such as concrete slabs or poured footings
- Ballasted footing mounts, such as concrete or steel bases that use weight to secure the solar module system in position and do not require ground penetration. This type of mounting system is well suited for sites where excavation is not possible such as capped landfills and simplifies decommissioning or relocation of solar module systems.
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]
Canopy
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.
Tracking
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 (
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
Building-integrated photovoltaics (BIPV) are
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]
Shade
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:
- Simplified array access for maintenance.
- Module wiring may be concealed to maintain the aesthetics of the shading structure.
- Growing vines around the structure must be avoided as they may come in contact with the wiring.[9][10]
PV Fencing
Sound barriers
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]
See also
- Building-integrated photovoltaics
- Solar tracker
- MPPT
- Rooftop photovoltaic power station
- Grid-connected photovoltaic power system
References
- ^ "Photovoltaic Racking Systems". solattach.com. 16 May 2016. Retrieved 2016-05-16.
- ^ "What difference is there between thermal solar energy and Photovoltaic solar energy?". epia.org. Archived from the original on 2011-07-12. Retrieved 2011-07-26.
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- ^ Grafman, Lonny; Pearce, Joshua (2021-01-01). "To Catch the Sun". To Catch the Sun.
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- ^ B.T. Wittbrodt & J.M. Pearce. Total U.S. cost evaluation of low-weight tension-based photovoltaic flat-roof-mounted racking.Solar Energy 117 (2015), 89–98.open access
- ^ a b "A GUIDE TO PHOTOVOLTAIC (PV) SYSTEM DESIGN AND INSTALLATION". ecodiy.org. Retrieved 2011-07-26.
- ^ a b "PROCEDURES FOR SOLAR ELECTRIC (PHOTOVOLTAIC abbreviated as PV) SYSTEM DESIGN AND INSTALLATIO" (PDF). thebii.org. Archived from the original (PDF) on 2007-05-08. Retrieved 2011-07-26.
- ^ SolarProfessional.com Ground-Mount PV Racking Systems March 2013
- ^ Massachusetts Department of Energy Resources Ground-Mounted Solar Photovoltaic Systems, December 2012
- ^ Matasci, Sara (2022-06-12). "Ground-Mounted Solar: Top 3 Things You Should Know | EnergySage". EnergySage Blog. Retrieved 2023-02-27.
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- ^ "Lumber PRICE Today | Lumber Spot Price Chart | Live Price of Lumber per Ounce | Markets Insider". markets.businessinsider.com. 2023-11-30. Retrieved 2023-12-20.
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- ^ Blok, Andrew. "Solar Parking Lots Are a Win-Win Energy Idea. Why Aren't They the Norm?". CNET. Retrieved 2023-02-16.
- ^ "Why Putting Solar Canopies on Parking Lots Is a Smart Green Move". Yale E360. Retrieved 2023-02-16.
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- ^ "Why your community's next solar panel project should be above a parking lot". Popular Science. 2023-02-24. Retrieved 2023-02-28.
- ^ Mossalgue, Jennifer (2022-11-08). "France to require all large parking lots to be covered by solar panels". Electrek. Retrieved 2023-02-28.
- ^ Shingleton, J. "One-Axis Trackers – Improved Reliability, Durability, Performance, and Cost Reduction" (PDF). National Renewable Energy Laboratory. Retrieved 2012-12-30.
- ^ Mousazadeh, Hossain; et al. "A review of principle and sun-tracking methods for maximizing" (PDF). Renewable and Sustainable Energy Reviews 13 (2009) 1800–1818. Elsevier. Retrieved 2012-12-30.
- ^ "Optimum Tilt of Solar Panels". MACS Lab. Retrieved 2014-10-19.
- ^ Perry, Keith (28 July 2014). "Most solar panels are facing the wrong direction, say scientists". The Daily Telegraph. Archived from the original on 11 January 2022. Retrieved 9 September 2018.
- ^ "Building Integrated Photovoltaics (BIPV)". wbdg.org. Retrieved 2011-07-26.
- ^ Reilly, Claire. "These Solar Windows Are an Invisible Alternative to Solar Panels". CNET. Retrieved 2023-02-28.
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- ^ Zito, Barbara (2023-01-04). "The Only Solar Shingles Buying Guide You Need". Forbes Home. Retrieved 2023-02-28.
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- ^ T., Nordmann; A., Froelich; L., Clavadetscher (2002). "Three integrated photovoltaic/sound barrier power plants. Construction and operational experience" (in German).
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