View source for Solar panel

{{Short description|Assembly of photovoltaic cells used to generate electricity}}
{{For|solar thermal panels|solar thermal collector|solar thermal energy}}
{{Use dmy dates|date=July 2022}}
[[File:Dji fly 20230602 13826 PM 27 1719032149374 photo optimized.jpg|thumb|Greencap Energy solar array mounted on brewery in [[Worthing]], [[England]]]]
[[File:Photovoltaik Dachanlage Hannover - Schwarze Heide - 1 MW.jpg|thumb|Solar array mounted on a rooftop]]

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. These electrons flow through a circuit and produce [[direct current]] (DC) electricity, which can be used to power various devices or be stored in [[battery (electricity)|batteries]]. Solar panels are also known as '''solar cell panels''', '''solar electric panels''', or '''PV modules'''.<ref>{{Cite book |last=Green |first=Martin A. |title=Solar cells: operating principles, technology and system applications |date=1998 |publisher=Univ. of New South Wales |isbn=978-0-85823-580-9 |edition=Repr. [der Ausg.] Englewood Cliffs, NJ 1982 |location=Kensington, NSW}}</ref>

Solar panels are usually arranged in groups called '''arrays''' or '''systems'''. A [[photovoltaic system]] consists of one or more solar panels, an [[solar inverter|inverter]] that converts DC electricity to [[alternating current]] (AC) electricity, and sometimes other components such as [[charge controller|controllers]], [[Measuring instrument|meters]], and [[solar tracker|trackers]]. Most panels are in [[solar farms]] or [[Rooftop solar power|rooftop solar panels]] which  [[grid-connected photovoltaic system|supply the electricity grid]].

Some advantages of solar panels are that they use a renewable and clean source of energy, reduce [[greenhouse gas emissions]], and lower electricity bills. Some disadvantages are that they depend on the availability and intensity of sunlight, require cleaning, and have high initial costs. Solar panels are widely used for residential, commercial, and industrial purposes, as well as in [[solar power satellite|space]], often together with [[Home energy storage|batteries]].

== History ==
{{See also|Solar cell#History|Timeline of solar cells}}

In 1839, the ability of some materials to create an electrical charge from light exposure was first observed by the French physicist [[Edmond Becquerel]].<ref name=":0">{{cite journal|date=April 2009|title=April 25, 1954: Bell Labs Demonstrates the First Practical Silicon Solar Cell|url=http://www.aps.org/publications/apsnews/200904/physicshistory.cfm|journal=APS News|publisher=American Physical Society|volume=18|issue=4}}</ref> Though these initial solar panels were too inefficient for even simple electric devices, they were used as an instrument to measure light.<ref>{{cite web|last1=Christian|first1=M|title=The history of the invention of the solar panel summary.|url=https://www.energymatters.com.au/panels-modules/|access-date=25 January 2019|website=Engergymatters.com|publisher=Energymatters.com}}</ref>

The observation by Becquerel was not replicated again until 1873, when the English electrical engineer [[Willoughby Smith]] discovered that the charge could be caused by light hitting [[selenium]]. After this discovery, [[William Grylls Adams]] and Richard Evans Day published "The action of light on selenium" in 1876, describing the experiment they used to replicate Smith's results.<ref name=":0" /><ref>{{cite journal|last1=Adams|first1=William Grylls|last2=Day|first2=R. E.|date=1 January 1877|title=IX. The action of light on selenium|journal=Philosophical Transactions of the Royal Society of London|language=en|volume=167|pages=313–316|doi=10.1098/rstl.1877.0009|issn=0261-0523|doi-access=}}</ref>

In 1881, the American inventor [[Charles Fritts]] created the first commercial solar panel, which was reported by Fritts as "continuous, constant and of considerable force not only by exposure to sunlight but also to dim, diffused daylight".<ref>{{cite news |last1=Meyers |first1=Glenn |date=31 December 2014 |title=Photovoltaic Dreaming 1875--1905: First Attempts At Commercializing PV |url=https://cleantechnica.com/2014/12/31/photovoltaic-dreaming-first-attempts-commercializing-pv/ |access-date=7 September 2018 |work=cleantechnica.com |publisher=Sustainable Enterprises Media Inc. |agency=CleanTechnica}}</ref><ref>{{cite magazine |title=A Brief History of Solar Panels |first1=Elizabeth |last1=Chu |first2=D. Lawrence |last2=Tarazano |magazine=Smithsonian Magazine |url=https://www.smithsonianmag.com/sponsored/brief-history-solar-panels-180972006/ |date=2019-04-22}} </ref>{{clarification needed|reason=The two sources differ on the date, 1881 or 1883. If Willoughby Smith's work on the photosensitivity of selenium was 1872 (cleantechnic) could Fritts selenium coated cell have been 1881? Also was this panel commercial? |date=March 2025}}
However, these solar panels were very inefficient, especially compared to [[coal-fired power plant]]s.

In 1939, [[Russell Ohl]] created the solar cell design that is used in many modern solar panels. He patented his design in 1941.<ref>{{cite web|last1=Ohl|first1=Russell|date=27 May 1941|title=Light-sensitive electric device|url=https://patents.google.com/patent/US2402662|access-date=7 September 2018}}</ref> In 1954, this design was first used by [[Bell Labs]] to create the first commercially viable [[silicon]] solar cell.<ref name=":0" />

Solar panel installers saw significant growth between 2008 and 2013.<ref>{{cite web |date= |title=Solar Industry Data |url=http://www.seia.org/research-resources/solar-industry-data |access-date=2014-01-13 |publisher=SEIA}}</ref> Due to that growth many installers had projects that were not "ideal" solar roof tops to work with and had to find solutions to shaded roofs and orientation difficulties.<ref>{{cite web |date=September 2007 |title=California Rooftop Photovoltaic (PV) Resource Assessment and Growth Potential by County |url=https://www.energy.ca.gov/2007publications/CEC-500-2007-048/CEC-500-2007-048.PDF |url-status=dead |archive-url=https://web.archive.org/web/20131213194550/https://www.energy.ca.gov/2007publications/CEC-500-2007-048/CEC-500-2007-048.PDF |archive-date=December 13, 2013 |access-date=September 28, 2022 |website=[[California Energy Commission]]}}</ref> This challenge was initially addressed by the re-popularization of [[micro-inverter]]s and later the invention of power optimizers.

Solar panel manufacturers partnered with micro-inverter companies to create AC modules and power optimizer companies partnered with module manufacturers to create smart modules.<ref>{{cite web |date=2012-10-23 |title=Solar Module OEMs Seeking Advantage With Inverter Electronics |url=http://www.greentechmedia.com/articles/read/Solar-Module-OEMs-Seeking-Advantage-with-Inverter-Electronics |access-date=2014-01-13 |publisher=Greentech Media}}</ref> In 2013 many solar panel manufacturers announced and began shipping their smart module solutions.<ref>{{cite web |date=2012-02-28 |title=Leading Solar Module OEMs To Display Next-generation Tigo Energy Technology During PV Expo Japan |url=http://www.tigoenergy.com/press-releases/leading-solar-module-oems-display-next-generation-tigo-energy-technology-during-pv |access-date=2014-01-13 |publisher=Tigo Energy |archive-date=12 August 2012 |archive-url=https://web.archive.org/web/20120812095050/http://www.tigoenergy.com/press-releases/leading-solar-module-oems-display-next-generation-tigo-energy-technology-during-pv |url-status=dead }}</ref>

== Theory and construction ==
{{See also|Solar cell}}
[[File:From a solar cell to a PV system.svg|thumb|upright=1.25|From a [[solar cell]] to a [[PV system]]]]

[[Photovoltaic]] modules consist of a large number of solar cells and use light energy ([[photon]]s) from the Sun to generate electricity through the [[photovoltaic effect]]. Most modules use [[Wafer (electronics)|wafer]]-based [[crystalline silicon]] cells or [[Thin film solar cell|thin-film cells]]. The structural ([[Dead and live loads|load carrying]]) member of a module can be either the top layer or the back layer. Cells must be protected from mechanical damage and moisture. Most modules are rigid, but semi-flexible ones based on thin-film cells are also available. The cells are usually connected electrically in [[Series and parallel circuits|series]], one to another to the desired voltage, and then in parallel to increase current. The [[Electric power|power]] (in [[watt]]s) of the module is the [[voltage]] (in [[volt]]s) multiplied by the [[electric current|current]] (in [[ampere]]s), and depends both on the amount of light and on the [[electrical load]] connected to the module. The manufacturing specifications on solar panels are obtained under standard conditions, which are usually not the true operating conditions the solar panels are exposed to on the installation site.<ref>{{Cite journal|last1=  Kifilideen|first1= Osanyinpeju|last2=Adewole|first2=  Aderinlewo|first3=Olayide|last3= Adetunji|last4= Emmanuel|first4= Ajisegiri|title=Performance Evaluation of Mono-Crystalline Photovoltaic Panels in Funaab, Alabata, Ogun State, Nigeria Weather Condition|journal=International Journal of Innovations in Engineering Research and Technology|volume=5|issue=2|pages=8–20|year=2018}}</ref>

A PV [[junction box]] is attached to the back of the solar panel and functions as its output interface. External connections for most photovoltaic modules use [[MC4 connector]]s to facilitate easy weatherproof connections to the rest of the system. A [[USB power|USB power interface]] can also be used.<ref>{{cite web | last=Kinsella | first=Pat | title=Are solar chargers worth it: a useful tool or a flash in the pan gimmick? | website=advnture.com | date=2021-06-03 | url=https://www.advnture.com/features/should-i-buy-a-portable-solar-power-charger | access-date=2022-02-16}}</ref> Solar panels also use metal frames consisting of racking components, brackets, reflector shapes, and troughs to better support the panel structure.<ref>{{Cite web |last=U.S. Department of Energy |date=2024-12-03 |title=Solar Energy Supply Chain Review Report |url=https://www.energy.gov/sites/default/files/2024-12/Solar%2520Energy%2520Supply%2520Chain%2520Report%2520-%2520Final%5B1%5D.pdf |access-date=2025-05-30 |website=energy.gov |quote=Mounting structures typically consist of low-cost steel components that provide mechanical support and can be configured as fixed-tilt or tracking systems, depending on application.}}</ref>

=== Cell connection techniques ===
Solar modular cells need to be connected together to form the module, with front electrodes blocking the solar cell front optical surface area slightly. To maximize frontal surface area available for sunlight and improve solar cell efficiency, manufacturers use varying rear electrode solar cell connection techniques:

* Passivated emitter rear contact (PERC) uses aluminum rear contact face and adds a polymer film to capture light<ref>{{Cite web |title=TOPCon Solar Cells: The New PV Module Technology in the Solar Industry |url=https://solarmagazine.com/solar-panels/topcon-solar-cells/ |access-date=2025-02-21 |website=Solar Magazine |language=en-US}}</ref>
* Tunnel oxide passivated contact (TOPCon) uses increasingly smaller silver rear bus bars and adds an oxidation layer to the PERC film to capture more light<ref>{{Cite web |last=Chan |first=Keng Siew |date=2019-11-21 |title=What is a TOPCON solar cell? - |url=https://www.kschan.com/what-is-a-topcon-solar-cell/ |access-date=2022-11-11 |language=en-US}}</ref><ref>{{Cite web |title=TOPCon Solar Cells: The New PV Module Technology in the Solar Industry |url=https://solarmagazine.com/solar-panels/topcon-solar-cells/ |access-date=2025-02-21 |website=Solar Magazine |language=en-US}}</ref><ref>{{Cite patent|number=US11824136B2|title=Solar cell, manufacturing method thereof, and photovoltaic module|gdate=2023-11-21|invent1=Yu|invent2=Liu|invent3=Zhang|inventor1-first=Kun|inventor2-first=Changming|inventor3-first=Xinyu|url=https://patents.google.com/patent/US11824136B2/en}}</ref>
* Interdigitated back contact (IBC)<ref>{{Cite web |title=Solar Cell Technology BSF PERC TOPCON HJT IBC - Knowledge |url=https://www.dsneg.com/info/solar-cell-technology-bsf-perc-topcon-hjt-ibc-59069656.html |access-date=2022-11-11 |website=DS New Energy |language=en}}</ref>

=== Arrays of PV modules ===
A single solar module can produce only a limited amount of power; most installations contain multiple modules adding their voltages or currents. A photovoltaic system typically includes an array of photovoltaic modules, an [[Power inverter|inverter]], a [[battery pack]] for energy storage, a charge controller, interconnection wiring, circuit breakers, fuses, disconnect switches, voltage meters, and optionally a [[solar tracking]] mechanism. Equipment is carefully selected to optimize energy output and storage, reduce power transmission losses, and convert from direct current to alternating current.

=== Smart solar modules ===
[[File:Smart Module.png|thumb|Smart module]]
Smart modules are different from traditional solar panels because the power electronics embedded in the module offers enhanced functionality such as panel-level [[maximum power point tracking]], monitoring, and enhanced safety.<ref>{{Cite web |last=EITCI |title=Smart PV Modules |url=https://www.eitci.org/technology-certification/sesg/smart-pv |access-date=2025-05-30 |website=EITCI – European Information Technologies Certification Institute |date=4 June 2021 |quote=Smart PV modules contain integrated power electronics, enabling features such as module-level maximum power point tracking (MPPT), real-time monitoring and fault detection, and enhanced fire safety through rapid shutdown capabilities.}}</ref> Power electronics attached to the frame of a solar module, or connected to the photovoltaic circuit through a connector, are not properly considered smart modules.<ref>{{cite web |date=2012-08-23 |title=Solar Electronics, Panel Integration and the Bankability Challenge |url=http://www.greentechmedia.com/articles/read/solar-electronics-panel-integration-and-the-bankability-challenge |access-date=2014-01-13 |publisher=Greentech Media}}</ref>

Several companies have begun incorporating into each PV module various embedded power electronics such as:

* [[Maximum power point tracking]] (MPPT) [[power optimizer]]s, a DC-to-DC converter technology developed to maximize the power harvest from solar photovoltaic systems by compensating for shading effects, wherein a shadow falling on a section of a module causes the electrical output of one or more strings of cells in the module to fall to near zero, but not having the output of the entire module fall to zero.<ref>{{Cite web |date=2021-10-15 |title=Do Solar Panels Work In The Shade? A Complete Guide To Solar Panel Shading, Its Effect, And Its Solutions {{!}} RenewableWise |url=https://www.renewablewise.com/do-solar-panels-work-in-the-shade/ |access-date=2022-11-11 |website=www.renewablewise.com |language=en-us}}</ref>
* [[Solar performance monitor]]s for data and fault detection

=== Technology ===
{{Main article|Crystalline silicon|Thin-film solar cell}}
[[File:Global photovoltaics market share by technology 1980-2021.svg|thumb|upright=1.25|Market-share of PV technologies since 1980]]

Most solar modules are currently produced from crystalline silicon (c-Si) [[solar cells]] made of [[polycrystalline silicon|polycrystalline]] or [[monocrystalline silicon]]. In 2021, crystalline silicon accounted for 95% of worldwide PV production,<ref>{{Cite web |title=PHOTOVOLTAICS REPORT |url=https://www.ise.fraunhofer.de/content/dam/ise/de/documents/publications/studies/Photovoltaics-Report.pdf}}</ref><ref>{{Cite journal |last1=Teixeira |first1=Bernardo |last2=Centeno Brito |first2=Miguel |last3=Mateus |first3=Antonio |date=2024 |title=Raw materials for the Portuguese decarbonization roadmap: The case of solar photovoltaics and wind energy |journal=Resources Policy |language=en |volume=90 |issue=104839 |doi=10.1016/j.resourpol.2024.104839|doi-access=free |bibcode=2024RePol..9004839T }}</ref> while the rest of the overall market is made up of thin-film technologies using [[Cadmium telluride photovoltaics|cadmium telluride]] (CdTe), [[Copper indium gallium selenide solar cell|copper indium gallium selenide]] (CIGS) and [[amorphous silicon]] {{nowrap|(a-Si)}}.<ref>{{cite web|url=http://www.ise.fraunhofer.de/en/downloads-englisch/pdf-files-englisch/photovoltaics-report-slides.pdf|title=Photovoltaics Report|website=Fraunhofer ISE|date=28 July 2014|pages= 18, 19}}</ref>

Emerging, [[Third-generation photovoltaic cell|third-generation solar technologies]] use advanced thin-film cells. They produce a relatively high-efficiency conversion for a lower cost compared with other solar technologies. Also, high-cost, high-efficiency, and close-packed rectangular [[multi-junction solar cell|multi-junction (MJ) cell]]s are usually used in [[solar panels on spacecraft]], as they offer the highest ratio of generated power per kilogram lifted into space. MJ-cells are [[compound semiconductor]]s and made of [[gallium arsenide]] (GaAs) and other semiconductor materials. Another emerging PV technology using MJ-cells is [[concentrator photovoltaics]] (CPV).

==== Thin film ====
{{Excerpt|Thin-film solar cell}}

=== Concentrator ===
Some special solar PV modules include [[Concentrator photovoltaics|concentrators]] in which light is focused by [[lens (optics)|lenses]] or mirrors onto smaller cells. This enables the cost-effective use of highly efficient, but expensive cells (such as [[gallium arsenide]]) with the trade-off of using a higher solar exposure area.<ref>{{Cite web |last1=Horowitz |first1=Kurt |last2=Woodhouse |first2=Michael |date=2015-10-01 |title=Current Status of Concentrator Photovoltaic (CPV) Technology |url=https://www.nrel.gov/docs/fy16osti/65130.pdf |access-date=2025-05-27 |website=National Renewable Energy Laboratory (NREL) |quote=Some special solar PV modules include concentrators in which light is focused by lenses or mirrors onto smaller cells.}}</ref> Concentrating the sunlight can also raise the efficiency to around 45%.<ref>{{cite journal |last1=Paul Marks |title=Space solar: The global race to tap the sun's energy from orbit |journal=New Scientist |date=Feb 13, 2016 |url=https://www.newscientist.com/article/2076599-space-solar-the-global-race-to-tap-the-suns-energy-from-orbit/}}</ref>

===Light capture===

The amount of light absorbed by a solar cell depends on the [[Angle of incidence (optics)|angle of incidence]] of whatever direct sunlight hits it. This is partly because the amount falling on the panel is proportional to the [[cosine]] of the angle of incidence, and partly because at high angle of incidence more light is reflected. To maximize total energy output, modules are often oriented to face south (in the Northern Hemisphere) or north (in the Southern Hemisphere) and tilted to allow for the latitude. [[Solar tracking]] can be used to keep the angle of incidence small.

Solar panels are often coated with an [[anti-reflective coating]], which is one or more thin layers of substances with refractive indices intermediate between that of silicon and that of air. This causes [[destructive interference]] in the reflected light, diminishing the amount. Photovoltaic manufacturers have been working to decrease reflectance with improved anti-reflective coatings or with textured glass.<ref>{{cite journal |last1=Rajinder Sharma |title=Effect of obliquity of incident light on the performance of silicon solar cells |journal=Heliyon |date=Jul 2019 |volume=5 |issue=7 |pages=e01965 |doi=10.1016/j.heliyon.2019.e01965 |doi-access=free |pmid=31317080 |pmc=6611928|bibcode=2019Heliy...501965S }}</ref><ref>{{cite thesis |last=Janakeeraman|first=Suryanarayana Vasantha |date=May 2013 |title=Angle of Incidence And Power Degradation Analysis of Photovoltaic Modules |url=https://core.ac.uk/download/pdf/79566658.pdf |type=MSt |chapter= |publisher=Arizona State University |docket= |oclc= |access-date=May 1, 2023}}</ref>

===Power curve===
[[File:Solar-Cell-IV-curve-with-MPP.png|thumb|A typical voltage/current curve for individual unshadowed solar panels. Maximum power point tracking ensures that as much power as possible is collected.]]
{{Main|Solar inverter}}
In general with individual solar panels, if not enough current is taken, then power isn't maximised. If too much current is taken then the voltage collapses. The optimum current draw is roughly proportional to the amount of sunlight striking the panel. Solar panel capacity is specified by the MPP (maximum power point) value of solar panels in full sunlight.

===Inverters===
[[Solar inverter]]s convert the DC power provided by panels to [[Alternating current|AC]] power.

[[File:UP-curve of partially shaded solar generator.png|thumb|Power/Voltage-curve of a partially shaded PV module, with marked local and global MPP]]
MPP (Maximum power point) of the solar panel consists of MPP voltage (V{{sub|mpp}}) and MPP current (I{{sub|mpp}}). Performing [[maximum power point tracking]] (MPPT), a solar inverter samples the output (I-V curve) from the solar cell and applies the proper electrical load to obtain maximum power.

An AC ([[Alternating Current|alternating current]]) solar panel has a small DC to AC [[microinverter]] on the back and produces [[AC power]] with no external [[DC connector]]. AC modules are defined by [[Underwriters Laboratories]] as the smallest and most complete system for harvesting solar energy.<ref>UL1741 pp 17, Section 2.2</ref><ref>{{Cite web |date=2016 |title=Alternative Energy Equipment and Systems Marking Guide |url=https://www.ul.com/sites/default/files/2019-05/AlternativeEnergy_EquipmentandSystemsMarking_AG_2016.pdf |access-date=2025-05-27 |website=UL (Underwriters Laboratories)}}</ref>

Micro-inverters work independently to enable each panel to contribute its maximum possible output for a given amount of sunlight, but can be more expensive.<ref>{{cite web |title=Micro Inverters for Residential Solar Arrays |url=https://www.expertsure.com/uk/home/micro-inverters-for-residential-solar-arrays/ |access-date=2017-05-10}}</ref>

=== Module interconnection ===
[[File:Photovoltaic Diode Connections.png|thumb|A connection example, a blocking diode is placed in series with each module string, whereas bypass diodes are placed in parallel with modules.]]
Module electrical connections are made with conducting wires that take the current off the modules and are sized according to the current rating and fault conditions, and sometimes include in-line fuses.

Panels are typically connected [[Series circuits|in series]] of one or more panels to form strings to achieve a desired output voltage, and strings can be connected [[Parallel circuits|in parallel]] to provide the desired current capability (amperes) of the PV system.

In string connections the voltages of the modules add, but the current is determined by the lowest performing panel. This is known as the "Christmas light effect". In parallel connections the voltages will be the same, but the currents add. Arrays are connected up to meet the voltage requirements of the inverters and to not greatly exceed the current limits.

Blocking and bypass [[diode]]s may be incorporated within the module or used externally to deal with partial array shading, in order to maximize output. For series connections, bypass diodes are placed in parallel with modules to allow current to bypass shaded modules which would otherwise severely limit the current. For paralleled connections, a blocking diode may be placed in series with each module's string to prevent current flowing backwards through shaded strings thus short-circuiting other strings. If three or more strings are connected in parallel, fuses are generally included on each string to eliminate the possibility of diode failures overloading the panels and wiring and causing fires.

===Connectors===
Outdoor solar panels usually include [[MC4 connector]]s, automotive solar panels may include an [[Automobile auxiliary power outlet|auxiliary power outlet]] and/or [[USB]] adapter and indoor panels may have a [[microinverter]].

{{Anchor|Efficiencies}}

== Efficiency ==
{{See also|Solar cell efficiency}}

[[File:NREL PV Module Record Efficiency Chart.png|thumb|upright=1.25|Reported timeline of champion solar module energy conversion efficiencies since 1988 ([[National Renewable Energy Laboratory]])<ref>{{cite web |url=https://www.nrel.gov/pv/assets/pdfs/champion-module-efficiencies-rev220401.pdf |title= Champion Photovoltaic Module Efficiency Plot |last=NREL |date=1 April 2022 |website=[[National Renewable Energy Laboratory]] |access-date=6 April 2022 }}</ref> ]]

Each module is rated by its [[Direct current|DC]] output power under standard test conditions (STC) and hence the on field output power might vary. Power typically ranges from 100 to 365 [[Watt]]s (W). The efficiency of a module determines the area of a module given the same rated output{{snd}} an 8% efficient 230 W module will have twice the area of a 16% efficient 230 W module. Some commercially available solar modules exceed 24% efficiency.<ref>{{cite web |url=https://mashable.com/2015/10/02/elon-musk-solarcity-new-solar-panel/ |title=Elon Musk and SolarCity unveil 'world's most efficient' solar panel |last=Ulanoff |first=Lance |date=2 October 2015 |website=[[Mashable]] |access-date=9 September 2018 }}</ref><ref>{{cite web |url=https://www.sciencedaily.com/releases/2016/05/160517121811.htm|title=Milestone in solar cell efficiency achieved |last=da Silva |first=Wilson |date= 17 May 2016|website=[[ScienceDaily]] |access-date=9 September 2018 |quote=A new solar cell configuration developed by engineers at the University of New South Wales has pushed sunlight-to-electricity conversion efficiency to 34.5% -- establishing a new world record for unfocused sunlight and nudging closer to the theoretical limits for such a device.}}</ref> As of 2025,<ref>{{Cite web |last=National Renewable Energy Laboratory |date=2024-04-12 |title=Photovoltaic Module Efficiency Records |url=https://www.nrel.gov/pv/module-efficiency |access-date=2025-05-27 |website=National Renewable Energy Laboratory (NREL) |quote=These efficiencies have been verified by independent and internationally recognized testing laboratories such as NREL, AIST, JRC-ESTI, and Fraunhofer ISE.}}</ref> the best achieved sunlight conversion rate (solar module efficiency) is around 24.5% in new commercial products<ref>{{cite web|date=25 July 2014|title=SunPower e20 Module|url=http://us.sunpower.com/homes/products-services/solar-panels/e-series/|access-date=6 June 2014|archive-date=1 July 2014|archive-url=https://web.archive.org/web/20140701144231/http://us.sunpower.com/homes/products-services/solar-panels/e-series/|url-status=dead}}</ref> typically lower than the efficiencies of their cells in isolation. The most efficient mass-produced solar modules have power density values of up to 175 W/m<sup>2</sup> (16.22 W/ft<sup>2</sup>).<ref>{{cite web|title=HIT Photovoltaic Module|url=http://www.panasonic.com/business/pesna/includes/pdf/eco-construction-solution/HIT_Power_220A_Datasheet.pdf|access-date=25 November 2016|publisher=Sanyo / Panasonic}}</ref>

The current versus voltage curve of a module provides useful information about its electrical performance.<ref>{{cite journal|url=https://doi.org/10.1002/pip.1073| title=Experimental system for current–voltage curve measurement of photovoltaic modules under outdoor conditions|year=2011|last1=Piliougine|first1=M.|last2=Carretero|first2=J.
|last3=Mora-López|first3=L.|last4=Sidrach-de-Cardona|first4=M.| journal=Progress in Photovoltaics: Research and Applications|publisher=Progress in Photovoltaics | volume=19| issue=5| pages=591–602| doi=10.1002/pip.1073| s2cid=96904811|url-access=subscription}}</ref> Manufacturing processes often cause differences in the electrical parameters of different modules photovoltaic, even in cells of the same type. Therefore, only the experimental measurement of the I–V curve allows us to accurately establish the electrical parameters of a photovoltaic device. This measurement provides highly relevant information for the design, installation and maintenance of photovoltaic systems. Generally, the electrical parameters of photovoltaic modules are measured by indoor tests. However, outdoor testing has important advantages such as no expensive artificial light source required, no sample size limitation, and more homogeneous sample illumination.

[[Capacity factor#Photovoltaic power station|Capacity factor]] of solar panels is limited primarily by geographic [[latitude]] and varies significantly depending on cloud cover, dust, day length and other factors. In the [[United Kingdom]], seasonal capacity factor ranges from 2% (December) to 20% (July), with average annual capacity factor of 10–11%, while in [[Spain]] the value reaches 18%.<ref>{{Cite web|last=Mearns|first=Euan|date=2015-10-20|title=UK Solar PV Vital Statistics|url=http://euanmearns.com/uk-solar-pv-vital-statistics/|access-date=2021-07-14|website=Energy Matters|language=en-US}}</ref> 
Globally, capacity factor for utility-scale PV farms was 16.1% in 2019.<ref>{{Cite web|title=Solar PV capacity factor globally 2020|url=https://www.statista.com/statistics/799330/global-solar-pv-installation-cost-per-kilowatt/|access-date=2021-07-14|website=Statista|language=en}}</ref>{{Unreliable source?|date=January 2024}}

Overheating is the most important factor for the efficiency of the solar panel.<ref>{{Cite journal |last1=Elqady |first1=Hesham I. |last2=El-Shazly |first2=A. H. |last3=Elkady |first3=M. F. |date=2022-10-31 |title=Parametric study for optimizing double-layer microchannel heat sink for solar panel thermal management |journal=Scientific Reports |language=en |volume=12 |issue=1 |pages=18278 |doi=10.1038/s41598-022-23061-8 |issn=2045-2322 |pmc=9622875 |pmid=36316376|bibcode=2022NatSR..1218278E }}</ref>

=== Radiation-dependent efficiency ===
Depending on construction, photovoltaic modules can produce electricity from a range of [[Electromagnetic spectrum|frequencies of light]], but usually cannot cover the entire solar radiation range (specifically, [[ultraviolet]], [[infrared]] and low or diffused light). Hence, much of the incident [[sunlight]] energy is wasted by solar modules, and they can give far higher efficiencies if illuminated with [[monochromatic]] light. Therefore, another design concept is to split the light into six to eight different wavelength ranges that will produce a different color of light, and direct the beams onto different cells tuned to those ranges.<ref>{{Cite news|url=https://www.technologyreview.com/s/513671/ultra-efficient-solar-power/|archive-url=https://wayback.archive-it.org/all/20160220173016/https://www.technologyreview.com/s/513671/ultra-efficient-solar-power/|url-status=dead|archive-date=20 February 2016|title=Managing Light To Increase Solar Efficiency|last=Orcutt|first=Mike|work=MIT Technology Review|access-date=2018-03-14|language=en}}</ref>

== Performance and degradation ==
[[File:Actual output in volts, amps, and wattage from a 100 Watt Solar module in August.jpg|thumb|upright=1.25]]
[[File:Variability of Solar Energy.jpg|thumb|upright=1.25|This chart illustrates the effect of clouds on solar energy production.]]

Module performance is generally rated under standard test conditions (STC): [[irradiance]] of 1,000 [[W/m2|W/m<sup>2</sup>]], solar [[spectrum]] of [[Airmass|AM]] 1.5 and module temperature at 25&nbsp;°C.<ref>{{Cite book|last=Dunlop|first=James P.|url=https://www.worldcat.org/oclc/828685287|title=Photovoltaic systems|date=2012|publisher=American Technical Publishers, Inc|others=National Joint Apprenticeship and Training Committee for the Electrical Industry|isbn=978-1-935941-05-7|edition=3rd|location=Orland Park, IL|oclc=828685287}}</ref> The actual voltage and current output of the module changes as lighting, temperature and load conditions change, so there is never one specific voltage at which the module operates. Performance varies depending on geographic location, time of day, the day of the year, amount of [[solar irradiance]], direction and tilt of modules, cloud cover, shading, [[soiling (solar energy)|soiling]], state of charge, and temperature. Performance of a module or panel can be measured at different time intervals with a DC clamp meter or shunt and logged, graphed, or charted with a chart recorder or data logger.

For optimum performance, a solar panel needs to be made of similar modules oriented in the same direction perpendicular to direct sunlight. Bypass diodes are used to circumvent broken or shaded panels and optimize output. These bypass diodes are usually placed along groups of solar cells to create a continuous flow.<ref>{{cite web |last1=Bowden |first1=Stuart |last2=Honsberg |first2=Christiana |title=Bypass Diodes |url=https://www.pveducation.org/pvcdrom/modules-and-arrays/bypass-diodes |website=Photovoltaic Education |access-date=29 June 2021}}</ref>

Electrical characteristics include nominal power (P<sub>MAX</sub>, measured in [[watt|W]]), [[open-circuit voltage]] (V<sub>OC</sub>), [[short-circuit current]] (I<sub>SC</sub>, measured in [[ampere]]s), maximum power voltage (V<sub>MPP</sub>), maximum power current (I<sub>MPP</sub>), peak power, ([[watt-peak]], W<sub>p</sub>), and module efficiency (%).

[[Open-circuit voltage]] or V<sub>OC</sub> is the maximum voltage the module can produce when not connected to an electrical circuit or system.<ref>{{cite web |title=Open-Circuit Voltage (Battery) |url=https://electricalschool.org/open-circuitvoltagebattery/ |website=Electrical School |date=13 June 2018 |access-date=30 June 2021}}</ref> V<sub>OC</sub> can be measured with a [[voltmeter]] directly on an illuminated module's terminals or on its disconnected cable.

The peak power rating, W<sub>p</sub>, is the maximum output under standard test conditions (not the maximum possible output). Typical modules, which could measure approximately {{convert|1|x|2|m|ft|sigfig=1}}, will be rated from as low as 75 W to as high as 600 W, depending on their efficiency. At the time of testing, the test modules are binned according to their test results, and a typical manufacturer might rate their modules in 5 W increments, and either rate them at +/- 3%, +/-5%, +3/-0% or +5/-0%.<ref>{{cite web|title=REC Alpha Black Series Factsheet|url=https://commercialsolaraustralia.com.au/wp-content/uploads/2020/08/DS-REC-Alpha-Black-Series-Rev-D-IEC-PRINT-EN.pdf}}</ref><ref>{{cite web |url=http://www.trinasolar.com/images/PDF/datasheets/us/TSM-PA14_US.pdf |title=TSM PC/PM14 Datasheet |access-date=2012-06-04 |archive-url=https://web.archive.org/web/20131029200512/http://www.trinasolar.com/images/PDF/datasheets/us/TSM-PA14_US.pdf |archive-date=29 October 2013 |url-status=dead }}</ref><ref>{{cite web |url=https://www.lubisolar.com/wp-content/uploads/2018/03/Poly-260-275W.pdf |title=LBS Poly 260 275 Data sheet |access-date=2018-01-09 |archive-date=9 January 2019 |archive-url=https://web.archive.org/web/20190109155544/https://www.lubisolar.com/wp-content/uploads/2018/03/Poly-260-275W.pdf |url-status=dead }}</ref>

=== Influence of temperature ===

The performance of a photovoltaic (PV) module depends on the environmental conditions, mainly on the global incident irradiance G in the plane of the module. However, the temperature T of the p–n junction also influences the main electrical parameters: the short circuit current I<sub>SC</sub>, the open circuit voltage V<sub>OC</sub> and the maximum power P<sub>max</sub>. In general, it is known that V<sub>OC</sub> shows a significant inverse correlation with T, while for I<sub>SC</sub> this correlation is direct, but weaker, so that this increase does not compensate for the decrease in V<sub>OC</sub>. As a consequence, P<sub>max</sub> decreases when T increases. This correlation between the power output of a solar cell and the working temperature of its junction depends on the semiconductor material, and is due to the influence of T on the concentration, lifetime, and mobility of the intrinsic carriers, i.e., electrons and gaps. inside the photovoltaic cell.

Temperature sensitivity is usually described by temperature coefficients, each of which expresses the derivative of the parameter to which it refers with respect to the junction temperature. The values of these parameters can be found in any data sheet of the photovoltaic module; are the following:

- β: V<sub>OC</sub> variation coefficient with respect to T, given by ∂V<sub>OC</sub>/∂T.

- α: Coefficient of variation of I<sub>SC</sub> with respect to T, given by ∂I<sub>SC</sub>/∂T.

- δ: Coefficient of variation of P<sub>max</sub> with respect to T, given by ∂P<sub>max</sub>/∂T.

Techniques for estimating these coefficients from experimental data can be found in the literature<ref>{{cite journal|url=https://doi.org/10.1002/pip.3396|doi=10.1002/pip.3396|title =Temperature coefficients of degraded crystalline silicon photovoltaic modules at outdoor conditions|year=2021|last1=Piliougine|first1=M.|last2=Oukaja|first2=A.|last3=Sidrach-de-Cardona|first3=M.|last4= Spagnuolo|first4=G.|journal=Progress in Photovoltaics: Research and Applications |publisher=Progress in Photovoltaics |volume=29 |issue=5 |pages=558–570 |s2cid=233976803 |url-access=subscription}}</ref>

Studies have shown that while high temperatures negatively impact efficiency, colder temperatures can improve solar panel performance due to reduced electrical resistance within the cells. However, winter conditions introduce additional challenges such as snow accumulation and reduced daylight hours, which can offset the efficiency benefits of lower temperatures. Solar panels are still capable of generating power in winter, but overall output may be lower due to limited sunlight exposure and potential obstructions.<ref>{{Citation |last1=Chitturi |first1=Sri Rama Phanindra |title=2018 IEEE International Energy Conference (ENERGYCON) |date=2018-09-19 |arxiv=1810.06692 |last2=Sharma |first2=Ekanki |last3=Elmenreich |first3=Wilfried|chapter=Efficiency of photovoltaic systems in mountainous areas |pages=1–6 |doi=10.1109/ENERGYCON.2018.8398766 |isbn=978-1-5386-3669-5 }}</ref>

===Degradation===

The ability of solar modules to withstand damage by rain, [[hail]], heavy snow load, and cycles of heat and cold varies by manufacturer, although most solar panels on the U.S. market are UL listed, meaning they have gone through testing to withstand hail.<ref>{{Cite news|url=http://energyinformative.org/solar-panels-weather/|title=Are Solar Panels Affected by Weather? |work=Energy Informative|access-date=2018-03-14|language=en-US}}</ref>

[[Potential-induced degradation]] (also called PID) is a potential-induced performance degradation in crystalline photovoltaic modules, caused by so-called stray currents.<ref>{{Cite web|url=https://www.solarplaza.com/channels/asset-management/11674/potential-induced-degradation-combatting-phantom-menace/|title=Solarplaza Potential Induced Degradation: Combatting a Phantom Menace|website=solarplaza.com|language=en|access-date=2017-09-04}}</ref> This effect may cause power loss of up to 30%.<ref>{{Cite web|url=https://eicero.com/what-is-pid|title=What is PID? – eicero|last=(www.inspire.cz)|first=INSPIRE CZ s.r.o.|website=eicero.com|language=en|access-date=2017-09-04|archive-date=4 September 2017|archive-url=https://web.archive.org/web/20170904105326/https://eicero.com/what-is-pid|url-status=dead}}</ref>

Advancements in photovoltaic technologies have brought about the process of "doping" the silicon substrate to lower the activation energy thereby making the panel more efficient in converting photons to retrievable electrons.<ref>{{cite web |title=How Solar Cells Work |url=http://science.howstuffworks.com/environmental/energy/solar-cell2.htm |website=HowStuffWorks |date=April 2000 |access-date=2015-12-09}}</ref>

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.<ref>{{cite web |title=Bonding in Metals and Semiconductors |url=http://2012books.lardbucket.org/books/principles-of-general-chemistry-v1.0/s16-06-bonding-in-metals-and-semicond.html |website=2012books.lardbucket.org|access-date=2015-12-09}}</ref> In doing so, the addition of boron impurity allows the activation energy to decrease twenty-fold from 1.12&nbsp;eV to 0.05&nbsp;eV. Since the potential difference (E<sub>B</sub>) is so low, the boron is able to thermally ionize at room temperatures. This allows for free energy carriers in the conduction and valence bands thereby allowing greater conversion of photons to electrons.

The power output of a photovoltaic (PV) device decreases over time. This decrease is due to its exposure to solar radiation as well as other external conditions. The degradation index, which is defined as the annual percentage of output power loss, is a key factor in determining the long-term production of a photovoltaic plant. To estimate this degradation, the percentage of decrease associated with each of the electrical parameters. The individual degradation of a photovoltaic module can significantly influence the performance of a complete string. Furthermore, not all modules in the same installation decrease their performance at exactly the same rate. Given a set of modules exposed to long-term outdoor conditions, the individual degradation of the main electrical parameters and the increase in their dispersion must be considered. As each module tends to degrade differently, the behavior of the modules will be increasingly different over time, negatively affecting the overall performance of the plant.<ref>{{Cite web |last1=Jordan |first1=Dirk C. |last2=Kurtz |first2=Sarah R. |date=2012-11-01 |title=Photovoltaic Degradation Rates — An Analytical Review |url=https://www.nrel.gov/docs/fy12osti/51664.pdf |access-date=2025-05-27 |website=National Renewable Energy Laboratory (NREL)}}</ref>

There are several studies dealing with the power degradation analysis of modules based on different photovoltaic technologies available in the literature. According to a recent study,<ref>{{cite journal|url=https://doi.org/10.1002/pip.3409|title=Analysis of the degradation of single-crystalline silicon modules after 21 years of operation|year=2021| last1=Piliougine|first1=M.|last2=Oukaja|first2=A.|last3=Sánchez-Friera|first3=P.|last4=Petrone|first4=G.|last5=Sánchez-Pacheco|first5=J.F.|last6= Spagnuolo|first6=G.|last7=Sidrach-de-Cardona|first7=M.|journal=Progress in Photovoltaics: Research and Applications |publisher=Progress in Photovoltaics |volume=29 |issue=8 |pages=907–919 |doi=10.1002/pip.3409 |s2cid=234831264 |hdl=10630/29057|hdl-access=free}}</ref> the degradation of crystalline silicon modules is very regular, oscillating between 0.8% and 1.0% per year.

On the other hand, if we analyze the performance of thin-film photovoltaic modules, an initial period of strong degradation is observed (which can last several months and even up to 2 years), followed by a later stage in which the degradation stabilizes, being then comparable to that of crystalline silicon.<ref>{{cite journal|url= https://doi.org/10.1002/pip.3567|title=Analysis of the degradation of amorphous silicon-based modules after 11 years of exposure by means of IEC60891:2021 procedure 3|year=2022|last1=Piliougine|first1=M.|last2=Oukaja|first2=A.|last3=Sidrach-de-Cardona|first3=M.|last4=Spagnuolo|first4 =G.|journal=Progress in Photovoltaics: Research and Applications |publisher=Progress in Photovoltaics |volume=30 |issue=10 |pages=1176–1187 |doi=10.1002/pip.3567 |hdl=10630/24064 |s2cid=248487635 |hdl-access=free}}</ref> Strong seasonal variations are also observed in such thin-film technologies because the influence of the solar spectrum is much greater. For example, for modules of amorphous silicon, micromorphic silicon or cadmium telluride, we are talking about annual degradation rates for the first years of between 3% and 4%.<ref>{{cite journal|doi=10.1016/j.renene.2022.05.063|title=New model to study the outdoor degradation of thin-film photovoltaic modules|year=2022|last1=Piliougine|first1=M.|last2=Sánchez-Friera|first2 =P.|last3=Petrone|first3=G.|last4=Sánchez-Pacheco|first4=J.F.|last5=Spagnuolo|first5=G.|last6=Sidrach-de-Cardona|first6=M.|journal=Renewable Energy|volume=193 |pages=857–869 |bibcode=2022REne..193..857P |s2cid=248926054 |hdl=10630/29061|hdl-access=free}}</ref> However, other technologies, such as CIGS, show much lower degradation rates, even in those early years.

== Mounting and tracking==
{{main article|Photovoltaic mounting system|Solar tracker}}
[[File:EarthRangersCentre-ImageEnhancement.jpg|thumb|Solar modules mounted on [[solar tracker]]s]]
[[File:Children of the Sun Solar Initiative (48132850231).jpg|thumb|Workers install residential rooftop solar panels]]

===Ground===
Large utility-scale [[solar power plant]]s frequently use ground-mounted photovoltaic systems. Their solar modules are held in place by racks or frames that are attached to ground-based mounting supports.<ref>{{cite web|website=SolarProfessional.com|url=http://solarprofessional.com/articles/products-equipment/racking/ground-mount-pv-racking-systems|title=Ground-Mount PV Racking Systems|date=March 2013|access-date=19 October 2014|archive-date=15 May 2013|archive-url=https://web.archive.org/web/20130515164621/http://solarprofessional.com/articles/products-equipment/racking/ground-mount-pv-racking-systems|url-status=dead}}</ref><ref>{{cite web|website=Massachusetts Department of Energy Resources | url=http://www.mass.gov/eea/docs/doer/renewables/solar/solar-pv-guide.pdf|title=Ground-Mounted Solar Photovoltaic Systems|date=December 2012}}</ref> 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.

{{multiple image
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====Vertical bifacial solar array====
[[File:Agrivoltaic installation Foulum.jpg|thumb|[[Agrivoltaics|Agrivoltaic]] vertical [[Bifacial solar cells|bifacial]] solar panels]]
[[File:Vertical Bifacial vs South facing solar array.webp|thumb|Vertical [[Bifacial solar cells|Bifacial]] vs south facing solar array power output
{{legend-line|#00A2FF solid 3px|Vertical [[Bifacial solar cells|Bifacial]]}}
{{legend-line|#EE220C solid 3px|South facing solar array}}
]]
Vertical [[bifacial solar cells]] are oriented towards east and west to catch the sun's [[irradiance]] more efficiently in the morning and evening. Applications include [[agrivoltaics]], solar fencing, highway and railroad noise dampeners and [[barricade]]s.<ref>{{cite web | url=https://undecidedmf.com/have-we-been-doing-solar-wrong-all-along/ | title=Have we been doing Solar wrong all along? - Undecided with Matt Ferrell | date=6 February 2024 }}</ref>

===Roof===
{{main|Rooftop solar power}}
Roof-mounted solar power systems consist of solar modules held in place by racks or frames attached to roof-based mounting supports.<ref name=eco>{{cite web |url=http://www.ecodiy.org/california%20PV/californian%20photovoltaic%20best.htm |title=A Guide To Photovoltaic System Design And Installation |date=4 September 2001 |publisher=ecodiy.org |access-date=2011-07-26}}</ref> Roof-based mounting supports include:
* Rail 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 bases that use weight to secure the panel system in position and do not require through penetration. This mounting method allows 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 run in a conduit appropriate for the climate conditions

====Solar canopy====
{{main|Solar canopy}}
[[File:Parking under Solar Canopy (52937580768).jpg|thumb|[[Solar canopy]] parking lot in [[New Haven, Connecticut|New Haven]] at Hotel Marcel.  There are EV [[Charging station#SAE|level 2]] chargers underneath the canopy and a 12-stall [[Tesla Supercharger]] behind.]]

Solar canopies are [[solar array]]s which are installed on top of a traditional [[Canopy (architecture)|canopy]]. These canopies could be a parking lot canopy, [[carport]], [[gazebo]], [[Pergola]], or [[patio cover]].

There are many benefits, which include maximizing the space available in urban areas while also providing shade for cars. The energy produced can be used to create electric vehicle (EV) charging stations.<ref>{{Cite web |title=Why Putting Solar Canopies on Parking Lots Is a Smart Green Move |url=https://e360.yale.edu/features/putting-solar-panels-atop-parking-lots-a-green-energy-solution |access-date=2024-09-29 |website=Yale E360 |language=en-US}}</ref>

===Portable=== 
Portable solar panels can ensure electric current, enough to charge devices (mobile, radio, ...) via USB-port or to charge a powerbank f.e. 
 
Special features of the panels include high flexibility, high durability & waterproof characteristics. They are good for travel or camping.
 
[[File:Portable solar panel2.jpg|thumb|A 5 V, 2 A, 10 W solar panel with USB port]]

===Tracking===
[[Solar tracker]]s 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.<ref name=NREL_tracker>{{cite web |last=Shingleton |first=J |title=One-Axis Trackers – Improved Reliability, Durability, Performance, and Cost Reduction |url=http://www.nrel.gov/docs/fy08osti/42769.pdf |publisher=National Renewable Energy Laboratory |access-date=2012-12-30}}</ref><ref>{{cite web |last=Mousazadeh |first=Hossain |title=A review of principle and sun-tracking methods for maximizing |url=http://xa.yimg.com/kq/groups/22199541/1797755549/name/A%252Breview%252Bof%252Bprinciple%252Band%252Bsun-tracking%252Bmethods%252Bfor%252Bmaximizing.pdf |work=Renewable and Sustainable Energy Reviews 13 (2009) 1800–1818 |publisher=Elsevier |access-date=2012-12-30 |display-authors=etal}}</ref>

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.<ref name=mounting_tilt>{{cite web |title=Optimum Tilt of Solar Panels |url=http://www.solarpaneltilt.com/ |publisher=MACS Lab |access-date=2014-10-19}}</ref>

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 provide more economically valuable power during morning and evening peak demands than north or south facing systems.<ref>{{cite news |url=https://www.telegraph.co.uk/news/earth/energy/solarpower/10996273/Most-solar-panels-are-facing-the-wrong-direction-say-scientists.html |archive-url=https://ghostarchive.org/archive/20220111/https://www.telegraph.co.uk/news/earth/energy/solarpower/10996273/Most-solar-panels-are-facing-the-wrong-direction-say-scientists.html |archive-date=11 January 2022 |url-access=subscription |url-status=live |title= Most solar panels are facing the wrong direction, say scientists|last=Perry |first=Keith |date= 28 July 2014|work= [[The Daily Telegraph]]|access-date=9 September 2018 }}{{cbignore}}</ref>

== Maintenance ==
[[File:Cleaning solar panel.jpg|thumb|General cleaning of ground-based solar panels at the Shanta Gold mine in Tanzania]]
[[File:Googleplex Solar panels.jpg|thumb|Deeper level of cleaning with pressure washing of the car port solar panels at Googleplex, Mountain View, California]]
Solar panel conversion efficiency, typically in the 20% range, is reduced by the accumulation of dust, grime, pollen, and other particulates on the solar panels, collectively referred to as [[soiling (solar energy)|soiling]]. "A dirty solar panel can reduce its power capabilities by up to 30% in high dust/pollen or desert areas", says Seamus Curran, associate professor of physics at the University of Houston and director of the Institute for NanoEnergy, which specializes in the design, engineering, and assembly of nanostructures.<ref>{{cite web |url=https://www.asme.org/engineering-topics/articles/energy/self-cleaning-solar-panels-maximize-efficiency |title=Self-Cleaning Solar Panels Maximize Efficiency |date=October 2012 |access-date=15 September 2014 |website=The American Society of Mechanical Engineers |publisher=ASME |last=Crawford |first=Mike}}</ref>
The average soiling loss in the world in 2018 is estimated to be at least 3% – 4%.<ref name="Ilse">{{cite journal |last1=Ilse |first1=Klemens |last2=Micheli |first2=Leonardo |last3=Figgis |first3=Benjamin W. |last4=Lange |first4=Katja |last5=Dassler |first5=David |last6=Hanifi |first6=Hamed |last7=Wolfertstetter |first7=Fabian |last8=Naumann |first8=Volker |last9=Hagendorf |first9=Christian |last10=Gottschalg |first10=Ralph |last11=Bagdahn |first11=Jörg |year=2019 |title=Techno-Economic Assessment of Soiling Losses and Mitigation Strategies for Solar Power Generation |journal=Joule |volume=3 |issue=10 |pages=2303–2321 |doi=10.1016/j.joule.2019.08.019 | name-list-style=vanc |doi-access=free |bibcode=2019Joule...3.2303I |hdl=11573/1625631 |hdl-access=free }}</ref>

Paying to have solar panels cleaned is a good investment in many regions, as of 2019.<ref name="Ilse"/> However, in some regions, cleaning is not cost-effective. In California as of 2013 soiling-induced financial losses were rarely enough to warrant the cost of washing the panels. On average, panels in California lost a little less than 0.05% of their overall efficiency per day.<ref>{{cite web |url= http://ucsdnews.ucsd.edu/pressrelease/cleaning_solar_panels_often_not_worth_the_cost_engineers_at_uc_san_diego_fi |title=Cleaning Solar Panels Often Not Worth the Cost, Engineers at UC San Diego Find |date=August 2013 |access-date=31 May 2015 |website=UC San Diego News Center |last=Patringenaru |first=Ioana}}</ref>

There are also [[occupational hazards of solar panel installation|occupational hazards with solar panel installation]] and maintenance. A 2015–2018 study in the UK investigated 80 PV-related incidents of fire, with over 20 "serious fires" directly caused by PV installation, including 37 domestic buildings and 6 solar farms. In {{frac|1|3}} of the incidents a root cause was not established and in a majority of others was caused by poor installation, faulty product or design issues. The most frequent single element causing fires was the DC isolators.<ref>{{Cite web |title=Fire incidents involving solar panels |url=https://www.gov.uk/government/publications/fire-incidents-involving-solar-panels |access-date=2021-06-22 |website=GOV.UK |date=19 March 2019 |language=en}}</ref>

A 2021 study by kWh Analytics determined median annual degradation of PV systems at 1.09% for residential and 0.8% for non-residential ones, almost twice that previously assumed.<ref>{{Cite web |date=2021-06-08 |title=Built solar assets are 'chronically underperforming' and modules degrading faster than expected, research finds |url=https://www.pv-tech.org/built-solar-assets-are-chronically-underperforming-and-modules-degrading-faster-than-expected-research-finds/ |access-date=2021-06-22 |website=PV Tech |language=en-US}}</ref> A 2021 module reliability study found an increasing trend in solar module failure rates with 30% of manufacturers experiencing safety failures related to junction boxes (growth from 20%) and 26% bill-of-materials failures (growth from 20%).<ref>{{Cite web |date=2021-05-26 |title=Solar module failure rates continue to rise as record number of manufacturers recognised in PVEL Module Reliability Scorecard |url=https://www.pv-tech.org/solar-module-failure-rates-continue-to-rise-as-record-number-of-manufacturers-recognised-in-pvel-module-reliability-scorecard/ |access-date=2021-06-22 |website=PV Tech |language=en-US}}</ref>

=== Cleaning ===
Cleaning methods for solar panels can be divided into 5 groups: manual tools, mechanized tools (such as tractor mounted brushes), installed hydraulic systems (such as sprinklers), installed robotic systems, and deployable robots. Manual cleaning tools are by far the most prevalent method of cleaning, most likely because of the low purchase cost. However, in a Saudi Arabian study done in 2014, it was found that "installed robotic systems, mechanized systems, and installed hydraulic systems are likely the three most promising technologies for use in cleaning solar panels".<ref>{{Cite book |last1=Alshehri |first1=Ali |last2=Parrott |first2=Brian |last3=Outa |first3=Ali |last4=Amer |first4=Ayman |last5=Abdellatif |first5=Fadl |last6=Trigui |first6=Hassane |last7=Carrasco |first7=Pablo |last8=Patel |first8=Sahejad |last9=Taie |first9=Ihsan |title=2014 Saudi Arabia Smart Grid Conference (SASG) |chapter=Dust mitigation in the desert: Cleaning mechanisms for solar panels in arid regions |date=December 2014 |chapter-url=https://ieeexplore.ieee.org/document/7274289 |pages=1–6 |doi=10.1109/SASG.2014.7274289 |isbn=978-1-4799-6158-0 |s2cid=23216963}}</ref>

Novel self-cleaning mechanisms for solar panels are being developed. For instance, in 2019 via [[Etching (microfabrication)#Wet etching|wet-chemically etched]][[Nanowire|nanowires]] and a hydrophobic coating on the surface water droplets could remove 98% of dust particles, which may be especially relevant for applications in the desert.<ref name="phys-20191209">{{cite news |author=American Associates, Ben-Gurion University of the Negev |date=9 December 2019 |title=Researchers develop new method to remove dust on solar panels |url=https://phys.org/news/2019-12-method-solar-panels.html |access-date=3 January 2020 |work=[[Ben-Gurion University of the Negev]]}}</ref><ref>{{cite journal |last1=Heckenthaler |first1=Tabea |last2=Sadhujan |first2=Sumesh |last3=Morgenstern |first3=Yakov |last4=Natarajan |first4=Prakash |last5=Bashouti |first5=Muhammad |last6=Kaufman |first6=Yair |date=3 December 2019 |title=Self-Cleaning Mechanism: Why Nanotexture and Hydrophobicity Matter |journal=Langmuir |volume=35 |issue=48 |pages=15526–15534 |doi=10.1021/acs.langmuir.9b01874 |issn=0743-7463 |pmid=31469282 |s2cid=201673096}}</ref>

In March 2022, [[Massachusetts Institute of Technology|MIT]] researchers announced the development of a waterless cleaning system for solar panels and mirrors to address the issue of dust accumulation, which can reduce solar output by up to 30 percent in one month. This system utilizes [[electrostatic repulsion]] to detach dust particles from the panel's surface, eliminating the need for water or brushes. An electrical charge imparted to the dust particles by passing a simple electrode over the panel causes them to be repelled by a charge applied to the panel itself. The system can be automated using a basic electric motor and guide rails.<ref>{{Cite web |date=2022-03-11 |title=How to clean solar panels without water |url=https://news.mit.edu/2022/solar-panels-dust-magnets-0311 |access-date=2024-02-18 |website=MIT News {{!}} Massachusetts Institute of Technology |language=en}}</ref>

== Waste and recycling ==
There were 30 thousand tonnes of PV waste in 2021, and the annual amount was estimated by Bloomberg NEF to rise to more than 1 million tons by 2035 and more than 10 million by 2050.<ref>{{Cite news |last=Holger |first=Dieter |date=2022-05-05 |title=The Solar Boom Will Create Millions of Tons of Junk Panels |language=en-US |work=[[The Wall Street Journal]] |url=https://www.wsj.com/articles/the-solar-boom-will-create-millions-of-tons-of-junk-panels-11651658402 |access-date=2022-10-14 |issn=0099-9660}}</ref> For comparison, 750 million tons of [[fly ash]] waste was produced by coal power in 2022.<ref>{{Cite web |title=Eco-efficient cement could pave the way to a greener future: Rice U. scientists 'flash' toxic heavy metals out of fly ash, make stronger concrete |url=https://www.sciencedaily.com/releases/2023/03/230328145425.htm |access-date=2023-05-17 |website=ScienceDaily |language=en}}</ref> In the United States, around 90% of decommissioned solar panels end up in landfills as of 2023.<ref>{{Cite web |title=As Millions of Solar Panels Age Out, Recyclers Hope to Cash In |url=https://e360.yale.edu/features/solar-energy-panels-recycling |access-date=2023-05-07 |website=Yale E360 |language=en-US}}</ref> Most parts of a solar module can be recycled including up to 95% of certain semiconductor materials or the glass as well as large amounts of ferrous and non-ferrous metals.<ref>{{cite web|first=Lisa|last=Krueger |title=Overview of First Solar's Module Collection and Recycling Program|url=http://www.bnl.gov/pv/files/PRS_Agenda/2_Krueger_IEEE-Presentation-Final.pdf |access-date=2017-03-17|publisher=[[Brookhaven National Laboratory]]|page=23}}</ref> Some private companies and non-profit organizations take-back and recycle end-of-life modules.<ref name="Wambach">{{cite web|last=Wambach|first=K |title=A Voluntary Take Back Scheme and Industrial Recycling of Photovoltaic Modules|url=http://www.bnl.gov/pv/files/PRS_Agenda/3_4_PV-Module-RecyclingWambach.pdf |access-date=2017-03-17|publisher=[[Brookhaven National Laboratory]]|page=37}}</ref> EU law requires manufacturers to ensure their solar panels are recycled properly. Similar legislation is underway in [[Japan]], [[India]], and [[Australia]].<ref>{{cite magazine|last=Stone|first=Maddie |date=22 August 2020|title=Solar Panels Are Starting to Die, Leaving Behind Toxic Trash|magazine=Wired|url=https://www.wired.com/story/solar-panels-are-starting-to-die-leaving-behind-toxic-trash/ |access-date=2 September 2020}}</ref> A 2023 Australian report said that there is a market for quality used panels and made recommendations for increasing reuse,<ref>{{Cite web |title=Reclaimed PV Panels Market Assessment Industry Report |url=https://www.circularpv.com.au/_files/ugd/10e921_d7a4fbb30adb4fd585b5d4784ccdc24b.pdf}}</ref>{{Rp|page=33}} but rules have not been implemented.<ref>{{cite web |last1=Mathur |first1=Deepika |last2=Gregory |first2=Robin |title=A solar panel recycling scheme would help reduce waste, but please repair and reuse first |url=https://theconversation.com/a-solar-panel-recycling-scheme-would-help-reduce-waste-but-please-repair-and-reuse-first-258806 |publisher=[[The Conversation (website)|The Conversation]] |date=15 June 2025}}</ref>

Recycling possibilities depend on the kind 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.<ref>{{Cite news|url=https://www.betterworldsolutions.eu/solar-panels-can-be-recycled/ |title=Solar Panels can be recycled – BetterWorldSolutions – The Netherlands|last=Cynthia|first=Latunussa |date=2015-10-09|work=BetterWorldSolutions – The Netherlands|access-date=2018-04-29|language=en-US}}</ref> It is possible to recover more than 80% of the incoming weight.<ref>{{cite journal |last1=Latunussa |first1=Cynthia E.L. |last2=Ardente |first2=Fulvio |last3=Blengini |first3=Gian Andrea |last4=Mancini |first4=Lucia |title=Life Cycle Assessment of an innovative recycling process for crystalline silicon photovoltaic panels |journal=Solar Energy Materials and Solar Cells |volume=156 |year=2016 |pages=101–11 |doi=10.1016/j.solmat.2016.03.020 |doi-access=free |bibcode=2016SEMSC.156..101L }}</ref> This process can be performed by flat glass recyclers, since the shape and composition of a PV module is similar to flat glass used in the building and automotive industry. The recovered glass, for example, is readily accepted by the glass foam and glass insulation industry.
* Non-silicon based modules: they require specific recycling technologies such as the use of chemical baths in order to separate the different semiconductor materials.<ref>Wambach. 1999. p. 17</ref> 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 up to 90% of the glass and 95% of the semiconductor materials contained.<ref>Krueger. 1999. p. 23</ref> Some commercial-scale recycling facilities have been created in recent years by private companies.<ref>Wambach. 1999. p. 23</ref>

Since 2010, there is an annual European conference bringing together manufacturers, recyclers and researchers to look at the future of PV module recycling.<ref>{{cite web |title=First Breakthrough in Solar Photovoltaic Module Recycling, Experts Say |publisher=[[European Photovoltaic Industry Association]] |url=http://www.unendlich-viel-energie.de/en/details/browse/11/article/253/first-breakthrough-in-solar-photovoltaic-module-recycling-experts-say.html |access-date=1 January 2011 |url-status=dead |archive-url=https://web.archive.org/web/20130512230542/http://www.unendlich-viel-energie.de/en/details/browse/11/article/253/first-breakthrough-in-solar-photovoltaic-module-recycling-experts-say.html |archive-date=12 May 2013 }}</ref><ref>{{cite web |title=3rd International Conference on PV Module Recycling |publisher=PV CYCLE |url=http://www.pvcycle.org/3rd-international-conference-on-pv-module-recycling/ |access-date=1 October 2012 |url-status=dead |archive-url= https://web.archive.org/web/20121210042052/http://www.pvcycle.org/3rd-international-conference-on-pv-module-recycling/ |archive-date=10 December 2012 }}</ref>

== Production ==
{{see also|List of photovoltaics companies}} 
{| class="wikitable sortable floatright" style="text-align:right; margin-left:1.4em;"
|+ Top producers of PV systems, by shipped capacity in gigawatts
|-
!scope="col"| Module producer
!scope="col"| Shipments<br/> in 2019<br/> ([[Gigawatt|GW]])<ref>{{Cite web|date=2020-08-05|title=LONGi: Who Are They And Why Do We Use Them|url=https://pulsesolar.com.au/longi-who-are-they-and-why-do-we-use-them/|website=Pulse Solar|language=en-GB|access-date=5 August 2020|archive-date=5 March 2021|archive-url=https://web.archive.org/web/20210305031224/https://pulsesolar.com.au/longi-who-are-they-and-why-do-we-use-them/|url-status=dead}}</ref>
|-
!scope="row"| [[Jinko Solar]]
| 14.2
|-
!scope="row"| [[JA Solar]]
| 10.3
|-
!scope="row"| [[Trina Solar]]
| 9.7
|-
!scope="row"|  [[LONGi Green Energy Technology|LONGi Solar]]
| 9.0
|-
!scope="row"| [[Canadian Solar]]
| 8.5
|-
!scope="row"|  [[Hanwha Q Cells]]
| 7.3
|-
!scope="row"| Risen Energy

| 7.0
|-
!scope="row"| [[First Solar]]
| 5.5
|-
!scope="row"|  [[GCL System Integration Technology|GCL System]]
| 4.8
|-
!scope="row"|  [[Shunfeng Photovoltaic]]
| 4.0
|}

The production of PV systems has followed a classic [[learning curve]] effect, with significant cost reduction occurring alongside large rises in efficiency and production output.<ref>{{Cite news|url=https://www.bbc.com/news/business-49344595|title=Can solar power shake up the energy market?|last=Harford|first=Tim|date=2019-09-11|access-date=2019-10-24|language=en-GB}}</ref>

With over 100% year-on-year growth in PV system installation, PV module makers dramatically increased their shipments of solar modules in 2019. They actively expanded their capacity and turned themselves into gigawatt [[GigaWatt|GW]] players.<ref>{{Cite web|url=https://www.helicalpower.com/|title=Solar PV Project Report {{pipe}} Helical Power|website=www.helicalpower.com|access-date=12 August 2022|archive-date=6 August 2019|archive-url=https://web.archive.org/web/20190806121659/https://www.helicalpower.com/|url-status=dead}}</ref> According to Pulse Solar, five of the top ten PV module companies in 2019 have experienced a rise in solar panel production by at least 25% compared to 2019.<ref name="pvmarketresearch1">{{cite web |title=LONGi: Who Are They And Why Do We Use Them |url=https://pulsesolar.com.au/longi-who-are-they-and-why-do-we-use-them |access-date=2020-06-18 |website=Pulse Solar |archive-date=5 March 2021 |archive-url=https://web.archive.org/web/20210305031224/https://pulsesolar.com.au/longi-who-are-they-and-why-do-we-use-them |url-status=dead }}</ref>

The basis of producing most solar panels is mostly on the use of silicon cells. These silicon cells are typically 10–20% efficient<ref>{{cite web|url=http://www.engineeringchallenges.org/cms/8996/9082.aspx|title=Grand Challenges Make Solar Energy Economical|website=engineeringchallenges.org}}</ref> at converting sunlight into electricity, with newer production models exceeding 22%.<ref>{{Cite web |url=http://www.solarcity.com/newsroom/press/solarcity-unveils-world%E2%80%99s-most-efficient-rooftop-solar-panel-be-made-america |title=SolarCity Press Release |date=2015-10-02 |access-date=2017-04-20 |archive-date=2 October 2015 |archive-url=https://web.archive.org/web/20151002211024/http://www.solarcity.com/newsroom/press/solarcity-unveils-world%E2%80%99s-most-efficient-rooftop-solar-panel-be-made-america |url-status=dead }}</ref>

In 2018, the world's top five solar module producers in terms of shipped capacity during the calendar year of 2018 were [[Jinko Solar]], [[JA Solar Holdings|JA Solar]], [[Trina Solar]], [[Longi solar]], and [[Canadian Solar]].<ref>{{Cite web|url=https://www.pv-tech.org/editors-blog/top-10-solar-module-suppliers-in-2018|title=Top 10 solar module suppliers in 2018|website=PV Tech|date=23 January 2019|language=en|access-date=2019-10-24}}</ref>
{{clear}}

== Price ==
[[File:1975 – Price of solar panels as a function of cumulative installed capacity.svg|thumb |upright=1.25 |[[Swanson's law]]–stating that solar module prices have dropped about 20% for each doubling of installed capacity—defines the "[[Experience curve effects|learning rate]]" of [[photovoltaics|solar photovoltaics]].<ref name=SolarPVlearningCurve>{{cite web |title=Solar (photovoltaic) panel prices vs. cumulative capacity |url=https://ourworldindata.org/grapher/solar-pv-prices-vs-cumulative-capacity |website=OurWorldInData.org |archive-url=https://archive.today/20250124235542/https://ourworldindata.org/grapher/solar-pv-prices-vs-cumulative-capacity |archive-date=24 January 2025 |date=2024 |url-status=live }} OWID credits source data to: Nemet (2009); Farmer & Lafond (2016); International Renewable Energy Agency (IRENA, 2024).</ref><ref>{{cite web |url=http://www.greentechmedia.com/articles/read/Is-there-really-a-Swansons-Law |title=Swanson's Law and Making US Solar Scale Like Germany |work=Greentech Media |date=2014-11-24}}</ref>]]
{{See also|Grid parity}}

The price of solar electrical power has continued to fall so that in many countries it has become cheaper than [[fossil fuel]] electricity from [[Mains electricity|the electricity grid]] since 2012, a phenomenon known as [[grid parity]].<ref name=UN-Energy-2012/> With the rise of global awareness, institutions such as the [[Internal Revenue Service|IRS]] have adopted a tax credit format, refunding a portion of any solar panel array for private use.<ref>{{Cite web |title=Home Energy Tax Credits {{!}} Internal Revenue Service |url=https://www.irs.gov/credits-deductions/home-energy-tax-credits |access-date=2023-12-04 |website=www.irs.gov |language=en}}</ref> The price of a solar array only continues to fall.

Average pricing information divides in three pricing categories: those buying small quantities (modules of all sizes in the kilowatt range annually), mid-range buyers (typically up to 10 [[MWp]] annually), and large quantity buyers (self-explanatory—and with access to the lowest prices). Over the long term there is clearly a systematic reduction in the price of cells and modules. For example, in 2012 it was estimated that the quantity cost per watt was about US$0.60, which was 250 times lower than the cost in 1970 of US$150.<ref>{{cite web |author=ENF Ltd. |url=http://www.enfsolar.com/news/Small-Chinese-Solar-Manufacturers-Decimated-in-2012 |title=Small Chinese Solar Manufacturers Decimated in 2012 {{pipe}} Solar PV Business News {{pipe}} ENF Company Directory |publisher=Enfsolar.com |date=2013-01-08 |access-date=2013-08-29}}</ref><ref>{{cite book |url=http://www.nap.edu/catalog.php?record_id=5954 |title=Harnessing Light |publisher=National Research Council |year=1997 |page=162|doi=10.17226/5954 |isbn=978-0-309-05991-6 }}</ref> A 2015 study shows price/kWh dropping by 10% per year since 1980, and predicts that solar could contribute 20% of total electricity consumption by 2030, whereas the [[International Energy Agency]] predicts 16% by 2050.<ref>{{cite journal |doi=10.1016/j.respol.2015.11.001 |title=How predictable is technological progress? |journal=Research Policy |volume=45 |issue=3 |pages=647–65 |year=2016 |last1=Farmer |first1=J. Doyne |last2=Lafond |first2=François |arxiv=1502.05274 |s2cid=154564641 }}</ref>

Real-world energy production costs depend 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 sunnier countries like Spain.
[[File:Energy pricing.png|thumb|upright=1.25|Short term normalized cost comparisons demonstrating value of various electric generation technologies<ref name="MacDonald">{{cite journal|doi=10.1038/nclimate2921 |title=Future cost-competitive electricity systems and their impact on US {{CO2}} emissions |year=2016 |last1=MacDonald |first1=Alexander E. |last2=Clack |first2=Christopher T. M. |last3=Alexander |first3=Anneliese |last4=Dunbar |first4=Adam |last5=Wilczak |first5=James |last6=Xie |first6=Yuanfu |journal=Nature Climate Change |volume=6 |issue=5 |pages=526–531 |bibcode=2016NatCC...6..526M }}</ref>|alt=]]
[[File:Energy pricing longterm.png|thumb|upright=1.25|Long term normalized cost comparisons demonstrating value of various electric generation technologies<ref name="MacDonald" />|alt=]]

Following to [[Rocky Mountain Institute|RMI]], [[balance of system|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'.<ref name=UN-Energy-2012>{{cite report |url=http://www.un-energy.org/stories/2498-re-considering-the-economics-of-photovoltaic-power |archive-url=http://arquivo.pt/wayback/20160516014242/http://www.un-energy.org/stories/2498-re-considering-the-economics-of-photovoltaic-power |url-status=dead |archive-date=2016-05-16 |title=Re-considering the economics of photovoltaic power |author=Morgan Baziliana |work=UN-Energy |publisher=United Nations |date=2012-05-17 |access-date=2012-11-20 |display-authors=etal }}</ref>

== Standards ==
Standards generally used in photovoltaic modules:
* [[International Electrotechnical Commission|IEC]] 61215 ([[crystalline silicon]] performance), 61646 ([[thin film]] performance) and 61730 (all modules, safety), 61853 (Photovoltaic module performance testing & energy rating)
* 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 ==
{{Main|Applications of photovoltaics}}
{{See also|List of solar-powered products}}

There are many practical applications for the use of solar panels or photovoltaics. It can first be used in agriculture as a power source for 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 system]]s and include a [[Photovoltaic system#Other systems|large variety of electric devices]]:
* [[Agrivoltaics]]
* [[Solar canal]]s
* [[Photovoltaic power station]]s
* [[Rooftop solar PV]] systems
* [[PV system#Standalone|Standalone PV systems]]
* [[Solar hybrid power systems]]
* [[Concentrated photovoltaics]]
* [[Floating solar]]; water-borne solar panels
* [[Solar plane]]s
* Solar-powered [[water purification]]
* [[Solar-pumped laser]]s
* [[Solar vehicle]]s
* [[Solar water heating]]
* [[Solar panels on spacecraft]] and [[space station]]s
* [[Solar landfill]]

== Limitations ==

=== Impact on electricity network ===
With the increasing levels of rooftop photovoltaic systems, the energy flow becomes 2-way. When there is more local generation than consumption, electricity is exported to the grid. However, an electricity network traditionally is not designed to deal with the 2- way energy transfer. Therefore, some technical issues may occur. For example, in Queensland Australia, more than 30% of households used rooftop PV by the end of 2017. The [[duck curve]] appeared often for a lot of communities from 2015 onwards. An over-voltage issue may result as the electricity flows from PV households back to the network.<ref>{{cite journal |last1=Miller |first1=Wendy |last2=Liu |first2=Aaron |last3=Amin |first3=Zakaria |last4=Wagner |first4=Andreas |title=Power Quality and Rooftop-Photovoltaic Households: An Examination of Measured Data at Point of Customer Connection |journal=Sustainability |volume=10 |issue=4 |year=2018 |pages=1224 |doi=10.3390/su10041224 |url=https://publikationen.bibliothek.kit.edu/1000082198/7829299 |doi-access=free |bibcode=2018Sust...10.1224M }}</ref> There are solutions to manage the over voltage issue, such as regulating PV inverter power factor, new voltage and energy control equipment at the electricity distributor level, re-conducting the electricity wires, demand side management, etc. There are often limitations and costs related to these solutions.

For [[Rooftop solar power|rooftop solar]] to be able to provide enough backup power during a power cut a [[Home energy storage|battery]] is often also required.<ref>{{Cite web |last1=Paulos |first1=Bentham |last2=Barbose |first2=Galen |last3=Gorman |first3=Will |date=2022-09-28 |title=Could solar and batteries power your home when the electricity grid goes out? |url=http://theconversation.com/could-solar-and-batteries-power-your-home-when-the-electricity-grid-goes-out-191157 |access-date=2023-09-16 |website=The Conversation |language=en}}</ref>

== Quality assurance ==

Solar module quality assurance involves testing and evaluating [[solar cells]] and Solar Panels to ensure the quality requirements of them are met. Solar modules (or panels) are expected to have a long service life between 20 and 40 years.<ref>{{cite book|last=Dickie |first=P.M. |year=1999 |title=Regional Workshop on Solar Power Generation Using Photovoltaic Technology |publisher=DIANE publishing |page=120 |isbn=9780788182648 |url=https://books.google.com/books?id=LsuwPTFHh8gC&dq=the+life+of+solar+panels&pg=PA120}}</ref> They should continually and reliably convey and deliver the power anticipated.  Solar modules can be tested through a combination of [[Physical property|physical]] tests, [[laboratory]] studies, and [[numerical analysis|numerical]] [[analyses]].<ref>{{cite book|last= Hough |first=T.P. |year=2006 |title=Trends in solar energy research |publisher=Nova |page=98 |isbn=9781594548666 |url=https://books.google.com/books?id=gpD-M_ZYMVMC&dq=how+to+test+solar+panel&pg=PA98}}</ref> Furthermore, solar modules need to be assessed throughout the different stages of their [[:wikt:life cycle|life cycle]]. Various companies such as Southern Research Energy & Environment, SGS Consumer Testing Services, [[TÜV Rheinland]], Sinovoltaics, Clean Energy Associates (CEA), [[CSA Solar]] International and Enertis provide services in solar module quality assurance."The implementation of consistent traceable and stable manufacturing processes becomes mandatory to safeguard and ensure the quality of the PV Modules" <ref>{{Cite journal|first1=Vicente |last1=Parra |first2=Ruperto |last2=Gómez|date=September 2018|title=Implementing risk mitigation strategies through module factory and production inspections|url=https://www.pv-tech.org/technical-papers/implementing-risk-mitigation-strategies-through-module-factory-and-producti|journal=PV Tech|volume=16|pages=25–28}}</ref>

=== Stages of testing ===
{{Unreferenced section|date=March 2022}}
{{see also|Photovoltaic module analysis techniques}}
The lifecycle stages of testing solar modules can include: the conceptual phase, [[manufacturing]] phase, [[transportation]] and installation, [[Project commissioning|commissioning]] phase, and the in-service phase. Depending on the test phase, different test principles may apply.

==== Conceptual phase ====
The first stage can involve '''design verification''' where the expected output of the module is tested through [[computer simulation]]. Further, the modules ability to withstand natural environment conditions such as [[temperature]], [[rain]], [[hail]],
[[snow]], [[corrosion]], [[dust]], [[lightning]], [[horizon]] and near-shadow effects is tested. The layout for [[design]] and [[construction]] of the module and the quality of components and installation can also be tested at this stage.

==== Manufacturing phase ====
Inspecting manufacturers of components is carried through visitation. The inspection can include assembly checks, material testing supervision and Non Destructive Testing (NDT). Certification is carried out according to ANSI/UL1703, IEC 17025, IEC 61215, IEC 61646, IEC 61701 and IEC 61730-1/-2.

== See also ==
{{subject bar|auto=y|d=y|Renewable energy|Energy}}
* [[Daisy chain (electrical engineering)]]
* [[Digital modeling and fabrication]]
* [[Domestic energy consumption]]
* [[Grid-tied electrical system]]
* [[Growth of photovoltaics]]
* [[Solar charger]]
* [[Solar cooker]]
* [[Solar still]]

== References ==
{{Reflist}}
==Further reading==
{{refbegin|30em}}
*{{cite book |last1=Smets |first1=Arno H. M. |last2=Jäger |first2=Klaus |last3=Isabella |first3=Olindo |last4=van Swaaij |first4=René A. C. M. M. |last5=Zeman |first5=Miro |title=Solar Energy: The Physics and Engineering of Photovoltaic Conversion, Technologies and Systems |publisher=UIT Cambridge Ltd. |location=Cambridge, England |date=2016 |isbn=9781906860325}}
*{{cite book |last=Boxwell |first=Michael |title=Solar Electricity Handbook: A Simple, Practical Guide to Solar Energy: How to Design and Install Photovoltaic Solar Electric Systems |edition=2023 |publisher=Greenstream Publishing |location=Birmingham, United Kingdom |date=2023 |isbn=97819076708007|oclc=1372392885}}
*{{cite book |last=Kalogirou |first=Soteris A. |title=Solar Energy Engineering: Processes and Systems |edition=3rd |publisher=Elsevier Science & Technology |location=San Diego |date=2023 |url=https://public.ebookcentral.proquest.com/choice/PublicFullRecord.aspx?p=30983366 |access-date=2025-06-24 |isbn=9780323993517|oclc=1412622415}}
*{{cite book |last=Mayfield |first=Ryan |title=Photovoltaic Design and Installation for Dummies |publisher=For Dummies |date=2022 |isbn=9781119544357}}
* {{cite book |last=Walker |first=Andy |title=Solar Energy: Technologies and Project Delivery for Buildings |publisher=Wiley |date=2023 |isbn=9781119618614|oclc=823861049}}
{{refend}}

{{Photovoltaics}}
{{Roofs}}

{{DEFAULTSORT:Solar Panel}}
[[Category:Photovoltaics]]
[[Category:Solar-powered devices|Panel]]
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