Photovoltaic system
A solar array in Canterbury, New Hampshire, United States, stands as a fixed tilt structure of crystalline silicon panels. This physical arrangement represents the visible portion of a photovoltaic system known simply as the solar array. The array does not include all other hardware required for operation. Engineers group these remaining components under the term balance of system or BOS. BOS includes power-conditioning equipment like inverters that convert direct current to alternating current. It also encompasses mounting structures such as racks that support the panels on roofs or ground. Electrical wiring and interconnections form another critical part of this balance. A typical residential system might use modules rated at 150 watts each. These modules are wired together in series to form strings. Multiple strings then connect in parallel to create an array capable of powering a home. Inverter technology has evolved significantly since early installations. Modern state-of-the-art converters reached over 98 percent efficiency by 2019. String inverters dominate the residential market while central inverters handle large commercial projects. Micro-inverters remain a niche option with less than 1 percent market share. Safety features like circuit breakers appear on both AC and DC sides to allow maintenance. Grid-tied systems must synchronize their output frequency with the public grid. Anti-islanding protection shuts down the inverter immediately if the main grid fails. This prevents dangerous conditions where utility workers might assume lines are dead while they still carry power.
Conventional crystalline silicon cells normally wire in series inside a protective laminate. The Fraunhofer Institute for Solar Energy Systems created a cell reaching 44.7 percent efficiency using 297 suns. Most commercially available panels achieve up to 27 percent efficiency as of 2012. Thin-film technologies have lost significant market share despite lower production costs. Crystalline silicon remains the predominant material used in 90 percent of worldwide produced solar modules. Module output degrades faster at increased temperatures. Allowing ambient air to flow over and behind PV modules reduces this problem. Wind interaction can sometimes increase energy losses following fluid mechanics theory. Effective module lives typically extend 25 years or more. The payback period for an investment varies greatly depending on incentives. A typical residential system recoups its energy cost in about two years. In exceptionally irradiated locations, that time decreases to one year or less. Soiling from dust or snow can reduce output by 3 to 4 percent globally. Cleaning flat mounted panels after 15 months in Ontario increased their output by almost 100 percent. Shading even a small portion of a cell causes dramatic output falls due to internal short-circuiting. Bypass diodes minimize these effects but still incur some power loss. Spectral effects play a role in optimal material selection for different environments. Albedo from surrounding surfaces significantly impacts output in northern latitudes.
Germany alone hosts 1.4 million photovoltaic systems while North America contains 440,000 units. Prices below $1.00 per watt became common by 2012 for large-scale installations. A price decrease of 50 percent had been achieved in Europe from 2006 to 2011. About 70 percent of all solar cells and modules are produced in China and Taiwan. European and US manufacturers account for only 5 percent of global production. The installed capacity for both small rooftop systems and large solar power stations is growing rapidly. Utility-scale projects now dominate new installations as focus shifts away from Europe. Sunbelt regions like the United States offer less opposition to ground-mounted farms. Grid parity has been achieved in about 30 countries where costs match conventional sources. Levelized cost of electricity reduces its value by 32.6 percent for every doubling of capacity. Solar PV modules currently account for less than half of the system's overall cost. Soft costs including customer acquisition and installation labor make up the remainder. Top installers include China, Japan, and the United States. Half of the world's capacity sits within Europe with Germany and Italy supplying 7 to 8 percent of domestic consumption. International Energy Agency expects solar power to become the largest source of electricity by 2050. Global solar tracker shipments hit a record 14.5 gigawatts in 2017 representing 32 percent growth.
Queensland Australia recorded more than 30 percent of households with rooftop PV by end of 2017. The famous Californian 2020 duck curve appears frequently for many communities since 2015. Electricity networks traditionally lack design features for two-way energy transfer. Over-voltage issues emerge when local generation exceeds consumption and flows back to the network. Grid operators must now provide storage alongside transmission lines and generation capacity. Hydro-storage remains common but other means are increasingly used. Inverter technology allows regulation of power factor to manage voltage levels. New voltage and energy control equipment at distributor level offers solutions. Re-conducting electricity wires addresses capacity constraints in dense residential areas. Demand side management strategies help balance supply and load requirements. Value of solar calculations show grid-tied utility customers often receive under-compensation. Net metering rates sometimes fail to reflect true value of distributed generation. Some jurisdictions require frequency and voltage monitors for installations over 30 kWp. These systems automatically shut down if load becomes inadequate or cannot be exported. Islanding inverters produce regulated voltages without synchronization needs for off-grid applications. Three-phase inverters offer unique options for supplying reactive power matching load requirements. Monitoring tools allow remote detection of breakdowns and optimization of operation.
International Electrotechnical Commission compiles standards applying to efficiency durability and safety. National regulations vary significantly across different countries and regions. United Kingdom considers PV installations generally permitted development requiring no planning permission. Listed properties or designated areas like National Parks still need formal approval. Building Regulations 2010 govern both domestic and commercial rooftop installations ensuring fire risks remain low. Article 690 of the National Electric Code provides guidelines for US installations. Local laws may supersede these general rules before work begins. Authority Having Jurisdiction reviews designs and issues permits for lawful construction. Spain issued a solar tax in 2013 accounting for debt created by government investment. Those not connecting to the grid faced fines up to 30 million euros until measures withdrew by 2018. New legislation banned any taxes on renewable energy self-consumption. Grid operators historically provided transmission lines but now must also provide storage capacity. Safety codes regulate grounding earthing and lightning protection for electric shock prevention. Electrical installation practices must comply with standards set forth within national codes. Equipment tested certified listed and labeled by Nationally Recognized Testing Laboratories ensures compliance. International standards cover plug connectors cables mounting systems and overall inverter efficiency.
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Common questions
What is a photovoltaic system and what components does it include?
A photovoltaic system is a power system designed to supply usable electric power from solar energy. It includes the visible solar array of crystalline silicon panels plus balance of system hardware such as inverters, mounting structures, and electrical wiring.
How efficient are modern photovoltaic systems and when was this achieved?
Modern state-of-the-art converters reached over 98 percent efficiency by 2019. The Fraunhofer Institute for Solar Energy Systems created a cell reaching 44.7 percent efficiency using 297 suns while most commercially available panels achieve up to 27 percent efficiency as of 2012.
Where are photovoltaic systems installed globally and which countries lead production?
Germany alone hosts 1.4 million photovoltaic systems while North America contains 440,000 units. About 70 percent of all solar cells and modules are produced in China and Taiwan with top installers including China, Japan, and the United States.
When do photovoltaic systems recoup their investment costs and how long do they last?
A typical residential system recoups its energy cost in about two years while exceptionally irradiated locations see that time decrease to one year or less. Effective module lives typically extend 25 years or more despite output degradation at increased temperatures.
What regulations govern photovoltaic installations in the United Kingdom and United States?
United Kingdom considers PV installations generally permitted development requiring no planning permission except for listed properties or designated areas like National Parks. Article 690 of the National Electric Code provides guidelines for US installations while Authority Having Jurisdiction reviews designs and issues permits for lawful construction.