Un sistema fotovoltaico , también sistema fotovoltaico o sistema de energía solar , es un sistema de energía diseñado para suministrar energía solar utilizable por medio de energía fotovoltaica . Consiste en una disposición de varios componentes, incluidos paneles solares para absorber y convertir la luz solar en electricidad, un inversor solar para convertir la salida de corriente directa a alterna , así como montaje , cableado y otros accesorios eléctricos para configurar un sistema de trabajo. . También puede utilizar un sistema de seguimiento solar.para mejorar el rendimiento general del sistema e incluir una solución de batería integrada , ya que se espera que bajen los precios de los dispositivos de almacenamiento. Estrictamente hablando, una matriz solar solo abarca el conjunto de paneles solares, la parte visible del sistema fotovoltaico, y no incluye todo el resto del hardware, a menudo resumido como equilibrio del sistema (BOS). Dado que los sistemas fotovoltaicos convierten la luz directamente en electricidad, no deben confundirse con otras tecnologías solares, como la energía solar concentrada o la energía solar térmica , que se utilizan para calefacción y refrigeración.
Sistemas y componentes de energía fotovoltaica: Top: solar de la secuencia de inversores y otros BOS componentes · Arsenal solar en la azotea en Hong Kong, China · integración arquitectónica en el balcón en Helsinki, Finlandia |
Los sistemas fotovoltaicos van desde sistemas pequeños, montados en techos o integrados en edificios con capacidades desde unas pocas hasta varias decenas de kilovatios, hasta grandes centrales eléctricas a gran escala de cientos de megavatios. Hoy en día, la mayoría de los sistemas fotovoltaicos están conectados a la red , mientras que los sistemas autónomos o fuera de la red representan una pequeña parte del mercado.
Operando silenciosamente y sin partes móviles o emisiones ambientales , los sistemas fotovoltaicos han pasado de ser aplicaciones de nicho de mercado a una tecnología madura utilizada para la generación de electricidad convencional. Un sistema de techo recupera la energía invertida para su fabricación e instalación en un plazo de 0,7 a 2 años y produce aproximadamente el 95 por ciento de la energía renovable limpia neta durante una vida útil de 30 años. [1] : 30 [2] [3]
Debido al crecimiento de la energía fotovoltaica , los precios de los sistemas fotovoltaicos han disminuido rápidamente desde su introducción. Sin embargo, varían según el mercado y el tamaño del sistema. En 2014, los precios de los sistemas residenciales de 5 kilovatios en los Estados Unidos rondaban los 3,29 dólares por vatio, [4] mientras que en el mercado alemán altamente penetrado , los precios de los sistemas de techo de hasta 100 kW descendieron a 1,24 euros por vatio. [5] Hoy en día, los módulos solares fotovoltaicos representan menos de la mitad del costo total del sistema, [6] dejando el resto a los componentes BOS restantes y a los costos indirectos, que incluyen la adquisición de clientes, permisos, inspección e interconexión, mano de obra de instalación y costos de financiamiento. [7] : 14
Sistema moderno
Descripción general
Un sistema fotovoltaico convierte la radiación solar , en forma de luz, en electricidad utilizable . Comprende la matriz solar y el equilibrio de los componentes del sistema. Los sistemas fotovoltaicos se pueden clasificar según varios aspectos, como sistemas conectados a la red frente a sistemas independientes , sistemas integrados en el edificio frente a sistemas montados en bastidores, sistemas residenciales frente a sistemas de servicios públicos, sistemas distribuidos frente a centralizados, sistemas de techo frente a sistemas montados en el suelo , sistemas de seguimiento frente a sistemas de inclinación fija, y sistemas de nueva construcción frente a sistemas modernizados . Otras distinciones pueden incluir sistemas con microinversores frente a inversor central, sistemas que utilizan silicio cristalino frente a tecnología de película delgada y sistemas con módulos de fabricantes chinos frente a europeos y estadounidenses.
Aproximadamente el 99 por ciento de todos los sistemas de energía solar europeos y el 90 por ciento de todos los de EE. UU. Están conectados a la red eléctrica , mientras que los sistemas fuera de la red son algo más comunes en Australia y Corea del Sur. [8] : 14 Los sistemas fotovoltaicos rara vez utilizan almacenamiento en batería. Esto puede cambiar, a medida que se implementen incentivos gubernamentales para el almacenamiento distribuido de energía y las inversiones en soluciones de almacenamiento se vuelvan económicamente viables para los sistemas pequeños. [9] [10] Un panel solar residencial típico se monta en un bastidor en el techo, en lugar de integrarse en el techo o la fachada del edificio, lo cual es significativamente más caro. Las estaciones de energía solar a escala de servicios públicos están montadas en el suelo, con paneles solares inclinados fijos en lugar de utilizar costosos dispositivos de seguimiento. El silicio cristalino es el material predominante utilizado en el 90 por ciento de los módulos solares producidos en todo el mundo, mientras que su rival de película delgada ha perdido participación de mercado. [1] : 17–20 Alrededor del 70 por ciento de todas las células y módulos solares se producen en China y Taiwán, y sólo el 5 por ciento por fabricantes europeos y estadounidenses . [1] : 11–12 La capacidad instalada tanto para los pequeños sistemas de azotea como para las grandes estaciones de energía solar está creciendo rápidamente y en partes iguales, aunque hay una tendencia notable hacia los sistemas a gran escala, ya que el enfoque en las nuevas instalaciones se está alejando desde Europa a regiones más soleadas, como Sunbelt en los EE. UU., que se oponen menos a las granjas solares montadas en el suelo y los inversores hacen más hincapié en la rentabilidad. [8] : 43
Impulsado por los avances en la tecnología y los aumentos en la escala de fabricación y la sofisticación, el costo de la energía fotovoltaica está disminuyendo continuamente. [3] Hay varios millones de sistemas fotovoltaicos distribuidos en todo el mundo, principalmente en Europa, con 1,4 millones de sistemas solo en Alemania [1] : 5 - así como en América del Norte con 440.000 sistemas en los Estados Unidos. [11] La eficiencia de conversión de energía de un módulo solar convencional aumentó del 15 al 20 por ciento desde 2004 [1] : 17 y un sistema fotovoltaico recupera la energía necesaria para su fabricación en aproximadamente 2 años. En lugares excepcionalmente irradiados, o cuando se usa tecnología de película delgada, el llamado tiempo de recuperación de energía disminuye a un año o menos. [1] : 30–33 La medición neta y los incentivos financieros, como las tarifas de alimentación preferenciales para la electricidad generada por energía solar, también han respaldado enormemente las instalaciones de sistemas fotovoltaicos en muchos países. [12] El costo nivelado de la electricidad de los sistemas fotovoltaicos a gran escala se ha vuelto competitivo con las fuentes de electricidad convencionales en una lista cada vez mayor de regiones geográficas, y se ha logrado la paridad de red en unos 30 países diferentes. [13] [14] [15]
A partir de 2015, el mercado fotovoltaico mundial de rápido crecimiento se está acercando rápidamente a la marca de 200 GW, aproximadamente 40 veces la capacidad instalada en 2006. [16] Estos sistemas actualmente contribuyen alrededor del 1 por ciento a la generación de electricidad en todo el mundo. Los principales instaladores de sistemas fotovoltaicos en términos de capacidad son actualmente China, Japón y Estados Unidos, mientras que la mitad de la capacidad mundial está instalada en Europa, mientras que Alemania e Italia suministran entre el 7% y el 8% de sus respectivos consumos domésticos de electricidad con energía solar fotovoltaica. [17] La Agencia Internacional de Energía espera que la energía solar se convierta en la mayor fuente de electricidad del mundo para 2050, y que la energía solar fotovoltaica y la energía solar térmica concentrada contribuyan con un 16% y un 11% a la demanda mundial, respectivamente. [7]
Conexión a la red solar
Un sistema conectado a la red está conectado a una red independiente más grande (normalmente la red eléctrica pública) y alimenta energía directamente a la red. Esta energía puede ser compartida por un edificio residencial o comercial antes o después del punto de medición de ingresos, dependiendo de si la producción de energía acreditada se calcula independientemente del consumo de energía del cliente ( tarifa de alimentación ) o solo en la diferencia de energía ( medición neta ). Estos sistemas varían en tamaño, desde residenciales (2–10 kW p ) hasta estaciones de energía solar (hasta 10 s de MW p ). Esta es una forma de generación de electricidad descentralizada . La alimentación de electricidad a la red requiere la transformación de CC en CA mediante un inversor especial sincronizado con conexión a la red . En instalaciones del tamaño de kilovatios, el voltaje del sistema del lado de CC es tan alto como se permite (generalmente 1000 V, excepto los 600 V residenciales de EE. UU.) Para limitar las pérdidas óhmicas. La mayoría de los módulos (60 o 72 celdas de silicio cristalino) generan de 160 W a 300 W a 36 voltios. A veces es necesario o deseable conectar los módulos parcialmente en paralelo en lugar de todos en serie. Un conjunto individual de módulos conectados en serie se conoce como "cadena". [18]
Escala del sistema
Los sistemas fotovoltaicos generalmente se clasifican en tres segmentos de mercado distintos: techos residenciales, techos comerciales y sistemas a escala de servicios públicos montados en el suelo. Sus capacidades van desde unos pocos kilovatios hasta cientos de megavatios. Un sistema residencial típico es de alrededor de 10 kilovatios y está montado en un techo inclinado, mientras que los sistemas comerciales pueden alcanzar una escala de megavatios y generalmente se instalan en techos de poca pendiente o incluso planos. Aunque los sistemas montados en la azotea son pequeños y tienen un costo por vatio más alto que las grandes instalaciones a escala de servicios públicos, representan la mayor participación en el mercado. Sin embargo, existe una tendencia creciente hacia plantas de energía a gran escala, especialmente en la región del "cinturón solar" del planeta. [8] : 43 [19]
- Escala de utilidad
- Los grandes parques o granjas solares a escala de servicios públicos son centrales eléctricas y pueden proporcionar un suministro de energía a un gran número de consumidores. La electricidad generada se alimenta a la red de transmisión alimentada por plantas de generación central (planta conectada a la red o conectada a la red), o se combina con uno o varios generadores de electricidad domésticos para alimentar una pequeña red eléctrica (planta híbrida). En raras ocasiones, la electricidad generada se almacena o utiliza directamente en una planta independiente o en una isla. [20] [21] Los sistemas fotovoltaicos se diseñan generalmente para garantizar el mayor rendimiento energético para una inversión determinada. Algunas grandes centrales fotovoltaicas como Solar Star , Waldpolenz Solar Park y Topaz Solar Farm cubren decenas o cientos de hectáreas y tienen potencias de hasta cientos de megavatios .
- Azotea, móvil y portátil
- Un pequeño sistema fotovoltaico es capaz de proporcionar suficiente electricidad CA para alimentar una sola casa, o un dispositivo aislado en forma de CA o CC. Los satélites militares y civiles de observación de la Tierra , las luces de las calles , las señales de construcción y tráfico, los automóviles eléctricos , las tiendas de campaña que funcionan con energía solar [22] y las aeronaves eléctricas pueden contener sistemas fotovoltaicos integrados para proporcionar una fuente de energía primaria o auxiliar en forma de energía de CA o CC. , dependiendo del diseño y las demandas de potencia. En 2013, los sistemas de azotea representaron el 60 por ciento de las instalaciones en todo el mundo. Sin embargo, existe una tendencia a alejarse de las azoteas y hacia sistemas fotovoltaicos a escala de servicios públicos, ya que el enfoque de las nuevas instalaciones fotovoltaicas también se está desplazando de Europa a países en la región del cinturón solar del planeta donde la oposición a las granjas solares montadas en el suelo es menos acentuada. [8] : 43 Los sistemas fotovoltaicos portátiles y móviles proporcionan energía eléctrica independientemente de las conexiones de los servicios públicos, para un funcionamiento "fuera de la red". Estos sistemas se utilizan con tanta frecuencia en vehículos de recreo y embarcaciones que existen minoristas especializados en estas aplicaciones [23] y productos destinados específicamente a ellos. [24] [25] Dado que los vehículos recreativos (RV) normalmente llevan baterías y operan la iluminación y otros sistemas con una potencia nominal de CC de 12 voltios, los sistemas de RV normalmente funcionan en un rango de voltaje que puede cargar baterías de 12 voltios directamente, por lo que la adición de un El sistema fotovoltaico solo requiere paneles, un controlador de carga y cableado. Los sistemas solares de los vehículos recreativos suelen estar limitados en vataje por el tamaño físico del espacio del techo del RV. [26]
- Integrado en el edificio
- En áreas urbanas y suburbanas, las matrices fotovoltaicas se utilizan a menudo en los tejados para complementar el uso de energía; a menudo, el edificio tendrá una conexión a la red eléctrica , en cuyo caso la energía producida por la matriz fotovoltaica se puede vender de nuevo a la empresa de servicios públicos en algún tipo de acuerdo de medición neta . Algunas empresas de servicios públicos utilizan los tejados de clientes comerciales y postes telefónicos para respaldar el uso de paneles fotovoltaicos. [27] Los árboles solares son conjuntos que, como su nombre lo indica, imitan el aspecto de los árboles, proporcionan sombra y por la noche pueden funcionar como farolas .
Actuación
Las incertidumbres en los ingresos a lo largo del tiempo se relacionan principalmente con la evaluación del recurso solar y con el rendimiento del sistema en sí. En el mejor de los casos, las incertidumbres suelen ser del 4% para la variabilidad climática de un año a otro, del 5% para la estimación del recurso solar (en un plano horizontal), del 3% para la estimación de la irradiación en el plano de la matriz, del 3% para la potencia calificación de los módulos, 2% por pérdidas por suciedad y suciedad , 1,5% por pérdidas por nieve y 5% por otras fuentes de error. Identificar y reaccionar ante pérdidas manejables es fundamental para los ingresos y la eficiencia de O&M. El monitoreo del desempeño de la matriz puede ser parte de acuerdos contractuales entre el propietario de la matriz, el constructor y la empresa de servicios públicos que compra la energía producida. [ cita requerida ] Un método para crear "días sintéticos" utilizando datos meteorológicos fácilmente disponibles y la verificación mediante el campo de prueba Open Solar Outdoors hace posible predecir el rendimiento de los sistemas fotovoltaicos con altos grados de precisión. [28] Este método se puede utilizar para determinar los mecanismos de pérdida a escala local, como los de la nieve [29] [30] o los efectos de los revestimientos superficiales (por ejemplo, hidrófobos o hidrófilos ) sobre la suciedad o las pérdidas de nieve. [31] (Aunque en entornos de nieve intensa con graves interferencias en el suelo pueden producirse pérdidas anuales por nieve del 30%. [32] ) El acceso a Internet ha permitido una mejora adicional en el control de la energía y las comunicaciones. Los sistemas dedicados están disponibles de varios proveedores. Para los sistemas fotovoltaicos solares que utilizan microinversores (conversión de CC a CA a nivel de panel), los datos de potencia del módulo se proporcionan automáticamente. Algunos sistemas permiten configurar alertas de rendimiento que activan advertencias por teléfono / correo electrónico / mensaje de texto cuando se alcanzan los límites. Estas soluciones proporcionan datos para el propietario del sistema y el instalador. Los instaladores pueden monitorear de forma remota múltiples instalaciones y ver de un vistazo el estado de toda su base instalada. [ cita requerida ]
Componentes
Un sistema fotovoltaico para el suministro de energía residencial, comercial o industrial consta de la matriz solar y una serie de componentes que a menudo se resumen como el equilibrio del sistema (BOS). Este término es sinónimo de " Equilibrio de la planta " qv Los componentes BOS incluyen equipos de acondicionamiento de energía y estructuras para el montaje, generalmente uno o más convertidores de energía CC a CA , también conocidos como inversores , un dispositivo de almacenamiento de energía, un sistema de estanterías que soporta el paneles solares, cableado eléctrico e interconexiones, y montaje para otros componentes.
Opcionalmente, un equilibrio del sistema puede incluir cualquiera o todos los siguientes: medidor de grado de ingresos de crédito de energía renovable , rastreador de punto de máxima potencia (MPPT), sistema de batería y cargador , rastreador solar GPS , software de gestión de energía , sensores de irradiancia solar , anemómetro , o accesorios para tareas específicas diseñados para cumplir con los requisitos especializados del propietario de un sistema. Además, un sistema CPV requiere lentes o espejos ópticos y, a veces, un sistema de refrigeración.
Los términos "panel solar" y "sistema fotovoltaico" a menudo se utilizan incorrectamente de manera intercambiable, a pesar de que el panel solar no abarca todo el sistema. Además, "panel solar" se utiliza a menudo como sinónimo de "módulo solar", aunque un panel consta de una cadena de varios módulos. El término " sistema solar " también es un nombre inapropiado que se usa a menudo para un sistema fotovoltaico.
Panel solar
Los componentes básicos de un sistema fotovoltaico son las células solares. Una célula solar es el dispositivo eléctrico que puede convertir directamente la energía de los fotones en electricidad. Hay tres generaciones tecnológicas de células solares: la primera generación (1G) de células de silicio cristalino (c-Si), la segunda generación (2G) de células de película fina (como CdTe , CIGS , silicio amorfo y GaAs ), y la tercera generación (3G) de células orgánicas , sensibilizadas con colorante , perovskita y multifuncionales . [33] [34]
Las células solares convencionales de c-Si , normalmente cableadas en serie, están encapsuladas en un módulo solar para protegerlas de la intemperie. El módulo consta de un vidrio templado como cubierta, un encapsulante suave y flexible , una lámina trasera de un material resistente a la intemperie y al fuego y un marco de aluminio alrededor del borde exterior. Conectados eléctricamente y montados en una estructura de soporte, los módulos solares construyen una serie de módulos, a menudo llamados paneles solares. Una matriz solar consta de uno o varios paneles de este tipo. [35] Una matriz fotovoltaica, o matriz solar, es una colección vinculada de módulos solares. La potencia que puede producir un módulo rara vez es suficiente para cumplir con los requisitos de un hogar o una empresa, por lo que los módulos están conectados entre sí para formar una matriz. La mayoría de las matrices fotovoltaicas utilizan un inversor para convertir la potencia de CC producida por los módulos en corriente alterna que puede alimentar luces , motores y otras cargas. Los módulos en un campo fotovoltaico generalmente se conectan primero en serie para obtener el voltaje deseado ; Luego, las cadenas individuales se conectan en paralelo para permitir que el sistema produzca más corriente . Los paneles solares se miden normalmente en STC (condiciones de prueba estándar) o PTC (condiciones de prueba de PVUSA), en vatios . [36] Las clasificaciones típicas de los paneles van desde menos de 100 vatios hasta más de 400 vatios. [37] La clasificación de la matriz consiste en una suma de las clasificaciones del panel, en vatios, kilovatios o megavatios.
Módulo y eficiencia
Un módulo fotovoltaico típico de 150 vatios tiene aproximadamente un metro cuadrado de tamaño. Se puede esperar que dicho módulo produzca 0,75 kilovatios-hora (kWh) todos los días, en promedio, después de tener en cuenta el clima y la latitud, para una insolación de 5 horas de sol / día. Salida y vida útil del módulo degradadas por el aumento de temperatura. Permitir que el aire ambiente fluya hacia arriba y, si es posible, hacia atrás, los módulos fotovoltaicos reduce este problema. La vida útil efectiva de los módulos suele ser de 25 años o más. [38] El período de recuperación de la inversión en una instalación solar fotovoltaica varía mucho y, por lo general, es menos útil que un cálculo del rendimiento de la inversión . [39] Aunque normalmente se calcula entre 10 y 20 años, el período de recuperación financiera puede ser mucho más corto con incentivos. [40]
El efecto de la temperatura sobre los módulos fotovoltaicos se suele cuantificar mediante unos coeficientes que relacionan las variaciones de la tensión en circuito abierto, de la corriente de cortocircuito y de la potencia máxima a los cambios de temperatura. En este trabajo, guías experimentales integrales para estimar los coeficientes de temperatura. [41]
Debido al bajo voltaje de una celda solar individual (típicamente alrededor de 0.5V), varias celdas están cableadas (ver también el cobre usado en sistemas fotovoltaicos ) en serie en la fabricación de un "laminado". El laminado se ensambla en una carcasa protectora resistente a la intemperie, creando así un módulo fotovoltaico o un panel solar . Luego, los módulos se pueden unir en una matriz fotovoltaica. En 2012, los paneles solares disponibles para los consumidores tienen una eficiencia de hasta aproximadamente el 17%, [42] mientras que los paneles disponibles comercialmente pueden llegar hasta el 27%. Se ha registrado que un grupo del Instituto Fraunhofer de Sistemas de Energía Solar ha creado una celda que puede alcanzar una eficiencia del 44,7%, lo que hace que las esperanzas de los científicos de alcanzar el umbral de eficiencia del 50% sean mucho más factibles. [43] [44] [45] [46]
Sombreado y suciedad
La salida eléctrica de la célula fotovoltaica es extremadamente sensible a las sombras ("efecto de luz navideña"). [47] [48] [49] Cuando incluso una pequeña parte de una celda, módulo o matriz está sombreada, y el resto está a la luz del sol, la salida cae drásticamente debido a un "cortocircuito" interno (los electrones invierten el curso a través de la parte sombreada de la unión pn ). Si la corriente extraída de la cadena de celdas en serie no es mayor que la corriente que puede producir la celda sombreada, la corriente (y por lo tanto la potencia) desarrollada por la cadena es limitada. Si hay suficiente voltaje disponible de las otras celdas en una cadena, la corriente se forzará a través de la celda rompiendo la unión en la parte sombreada. Este voltaje de ruptura en celdas comunes está entre 10 y 30 voltios. En lugar de aumentar la energía producida por el panel, la celda sombreada absorbe energía y la convierte en calor. Dado que el voltaje inverso de una celda sombreada es mucho mayor que el voltaje directo de una celda iluminada, una celda sombreada puede absorber la energía de muchas otras celdas en la cadena, afectando desproporcionadamente la salida del panel. Por ejemplo, una celda sombreada puede caer 8 voltios, en lugar de agregar 0.5 voltios, a un nivel de corriente particular, absorbiendo así la energía producida por otras 16 celdas. [50] Por tanto, es importante que una instalación fotovoltaica no esté a la sombra de árboles u otras obstrucciones.
Several methods have been developed to determine shading losses from trees to PV systems over both large regions using LiDAR,[51] but also at an individual system level using sketchup.[52] Most modules have bypass diodes between each cell or string of cells that minimize the effects of shading and only lose the power of the shaded portion of the array. The main job of the bypass diode is to eliminate hot spots that form on cells that can cause further damage to the array, and cause fires.
Sunlight can be absorbed by dust, snow, or other impurities at the surface of the module (collectively referred to as soiling). Soiling reduces the light that strikes the cells, which in turn reduces the power output of the PV system. Soiling losses aggregate over time, and can become large without adequate cleaning. In 2018, the global annual energy loss due to soiling was estimated to at least 3 % - 4 %.[53] However, soiling losses varies largely from region to region, and within regions.[54][55][56][57] Maintaining a clean module surface will increase output performance over the life of the PV system. In one study performed in a snow-rich area (Ontario), cleaning flat mounted solar panels after 15 months increased their output by almost 100%. However, 5° tilted arrays were adequately cleaned by rainwater.[30][58] In many cases, especially in arid regions, or in locations in close proximity to deserts, roads, industry, or agriculture, regular cleaning of the solar panels is cost-effective. In 2018, the estimated soiling-induced revenue loss was estimated to between 5 and 7 billion euros.[53]
The long‐term reliability of photovoltaic modules is crucial to ensure the technical and economic viability of PV as a successful energy source. The analysis of degradation mechanisms of PV modules is key to ensure current lifetimes exceeding 25 years.[59]
Insolation and energy
Solar insolation is made up of direct, diffuse, and reflected radiation. The absorption factor of a PV cell is defined as the fraction of incident solar irradiance that is absorbed by the cell.[60] At high noon on a cloudless day at the equator, the power of the sun is about 1 kW/m2,[61] on the Earth's surface, to a plane that is perpendicular to the sun's rays. As such, PV arrays can track the sun through each day to greatly enhance energy collection. However, tracking devices add cost, and require maintenance, so it is more common for PV arrays to have fixed mounts that tilt the array and face solar noon (approximately due south in the Northern Hemisphere or due north in the Southern Hemisphere). The tilt angle, from horizontal, can be varied for season,[62] but if fixed, should be set to give optimal array output during the peak electrical demand portion of a typical year for a stand-alone system. This optimal module tilt angle is not necessarily identical to the tilt angle for maximum annual array energy output.[63] The optimization of the photovoltaic system for a specific environment can be complicated as issues of solar flux, soiling, and snow losses should be taken into effect. In addition, later work has shown that spectral effects can play a role in optimal photovoltaic material selection. For example, the spectral albedo can play a significant role in output depending on the surface around the photovoltaic system[64] and the type of solar cell material.[65] For the weather and latitudes of the United States and Europe, typical insolation ranges from 4 kWh/m2/day in northern climes to 6.5 kWh/m2/day in the sunniest regions. A photovoltaic installation in the northern latitudes of Europe or the United States may expect to produce 1 kWh/m2/day. A typical 1 kW photovoltaic installation in Australia or the southern latitudes of Europe or United States, may produce 3.5–5 kWh per day, dependent on location, orientation, tilt, insolation and other factors. In the Sahara desert, with less cloud cover and a better solar angle, one could ideally obtain closer to 8.3 kWh/m2/day provided the nearly ever present wind would not blow sand onto the units. The area of the Sahara desert is over 9 million km2. 90,600 km2, or about 1%, could generate as much electricity as all of the world's power plants combined.[66]
Mounting
Modules are assembled into arrays on some kind of mounting system, which may be classified as ground mount, roof mount or pole mount. For solar parks a large rack is mounted on the ground, and the modules mounted on the rack. For buildings, many different racks have been devised for pitched roofs. For flat roofs, racks, bins and building integrated solutions are used.[citation needed] Solar panel racks mounted on top of poles can be stationary or moving, see Trackers below. Side-of-pole mounts are suitable for situations where a pole has something else mounted at its top, such as a light fixture or an antenna. Pole mounting raises what would otherwise be a ground mounted array above weed shadows and livestock, and may satisfy electrical code requirements regarding inaccessibility of exposed wiring. Pole mounted panels are open to more cooling air on their underside, which increases performance. A multiplicity of pole top racks can be formed into a parking carport or other shade structure. A rack which does not follow the sun from left to right may allow seasonal adjustment up or down.
Cabling
Due to their outdoor usage, solar cables are designed to be resistant against UV radiation and extremely high temperature fluctuations and are generally unaffected by the weather. Standards specifying the usage of electrical wiring in PV systems include the IEC 60364 by the International Electrotechnical Commission, in section 712 "Solar photovoltaic (PV) power supply systems", the British Standard BS 7671, incorporating regulations relating to microgeneration and photovoltaic systems, and the US UL4703 standard, in subject 4703 "Photovoltaic Wire".
Tracker
A solar tracking system tilts a solar panel throughout the day. Depending on the type of tracking system, the panel is either aimed directly at the sun or the brightest area of a partly clouded sky. Trackers greatly enhance early morning and late afternoon performance, increasing the total amount of power produced by a system by about 20–25% for a single axis tracker and about 30% or more for a dual axis tracker, depending on latitude.[67][68] Trackers are effective in regions that receive a large portion of sunlight directly. In diffuse light (i.e. under cloud or fog), tracking has little or no value. Because most concentrated photovoltaics systems are very sensitive to the sunlight's angle, tracking systems allow them to produce useful power for more than a brief period each day.[69] Tracking systems improve performance for two main reasons. First, when a solar panel is perpendicular to the sunlight, it receives more light on its surface than if it were angled. Second, direct light is used more efficiently than angled light.[70] Special Anti-reflective coatings can improve solar panel efficiency for direct and angled light, somewhat reducing the benefit of tracking.[71]
Trackers and sensors to optimise the performance are often seen as optional, but they can increase viable output by up to 45%.[72] Arrays that approach or exceed one megawatt often use solar trackers. Considering clouds, and the fact that most of the world is not on the equator, and that the sun sets in the evening, the correct measure of solar power is insolation – the average number of kilowatt-hours per square meter per day. For the weather and latitudes of the United States and Europe, typical insolation ranges from 2.26 kWh/m2/day in northern climes to 5.61 kWh/m2/day in the sunniest regions.[73][74]
For large systems, the energy gained by using tracking systems can outweigh the added complexity. For very large systems, the added maintenance of tracking is a substantial detriment.[75] Tracking is not required for flat panel and low-concentration photovoltaic systems. For high-concentration photovoltaic systems, dual axis tracking is a necessity.[76] Pricing trends affect the balance between adding more stationary solar panels versus having fewer panels that track.
As pricing, reliability and performance of single-axis trackers have improved, the systems have been installed in an increasing percentage of utility-scale projects. According to data from WoodMackenzie/GTM Research, global solar tracker shipments hit a record 14.5 gigawatts in 2017. This represents growth of 32 percent year-over-year, with similar or greater growth projected as large-scale solar deployment accelerates.[77]
Inverter
Systems designed to deliver alternating current (AC), such as grid-connected applications need an inverter to convert the direct current (DC) from the solar modules to AC. Grid connected inverters must supply AC electricity in sinusoidal form, synchronized to the grid frequency, limit feed in voltage to no higher than the grid voltage and disconnect from the grid if the grid voltage is turned off.[78] Islanding inverters need only produce regulated voltages and frequencies in a sinusoidal waveshape as no synchronisation or co-ordination with grid supplies is required.
A solar inverter may connect to a string of solar panels. In some installations a solar micro-inverter is connected at each solar panel.[79] For safety reasons a circuit breaker is provided both on the AC and DC side to enable maintenance. AC output may be connected through an electricity meter into the public grid.[80] The number of modules in the system determines the total DC watts capable of being generated by the solar array; however, the inverter ultimately governs the amount of AC watts that can be distributed for consumption. For example, a PV system comprising 11 kilowatts DC (kWDC) worth of PV modules, paired with one 10-kilowatt AC (kWAC) inverter, will be limited to the inverter's output of 10 kW. As of 2019, conversion efficiency for state-of-the-art converters reached more than 98 percent. While string inverters are used in residential to medium-sized commercial PV systems, central inverters cover the large commercial and utility-scale market. Market-share for central and string inverters are about 44 percent and 52 percent, respectively, with less than 1 percent for micro-inverters.[81]
Maximum power point tracking (MPPT) is a technique that grid connected inverters use to get the maximum possible power from the photovoltaic array. In order to do so, the inverter's MPPT system digitally samples the solar array's ever changing power output and applies the proper resistance to find the optimal maximum power point.[82]
Anti-islanding is a protection mechanism to immediately shut down the inverter, preventing it from generating AC power when the connection to the load no longer exists. This happens, for example, in the case of a blackout. Without this protection, the supply line would become an "island" with power surrounded by a "sea" of unpowered lines, as the solar array continues to deliver DC power during the power outage. Islanding is a hazard to utility workers, who may not realize that an AC circuit is still powered, and it may prevent automatic re-connection of devices.[83] Anti-Islanding feature is not required for complete Off-Grid Systems.
Type | Power | Efficiency(a) | Market Share(b) | Remarks |
---|---|---|---|---|
String inverter | up to 150 kWp(c) | 98% | 61.6% | Cost(b) €0.05-0.17 per watt-peak. Easy to replace. |
Central inverter | above 80 kWp | 98.5% | 36.7% | €0.04 per watt-peak. High reliability. Often sold along with a service contract. |
Micro-inverter | module power range | 90%–97% | 1.7% | €0.29 per watt-peak. Ease-of-replacement concerns. |
DC/DC converter (Power optimizer) | module power range | 99.5% | 5.1% | €0.08 per watt-peak. Ease-of-replacement concerns. Inverter is still needed. |
Source: data by IHS Markit 2020, remarks by Fraunhofer ISE 2020, from: Photovoltaics Report 2020, p. 39, PDF[81] Notes: (a)best efficiencies displayed, (b)market-share and cost per watt are estimated, (c)kWp = kilowatt-peak, (d) Total Market Share is greater than 100% because DC/DC converters are required to be paired with string inverters |
Battery
Although still expensive, PV systems increasingly use rechargeable batteries to store a surplus to be later used at night. Batteries used for grid-storage also stabilize the electrical grid by leveling out peak loads, and play an important role in a smart grid, as they can charge during periods of low demand and feed their stored energy into the grid when demand is high.
Common battery technologies used in today's PV systems include the valve regulated lead-acid battery– a modified version of the conventional lead–acid battery, nickel–cadmium and lithium-ion batteries. Compared to the other types, lead-acid batteries have a shorter lifetime and lower energy density. However, due to their high reliability, low self discharge as well as low investment and maintenance costs, they are currently the predominant technology used in small-scale, residential PV systems, as lithium-ion batteries are still being developed and about 3.5 times as expensive as lead-acid batteries. Furthermore, as storage devices for PV systems are stationary, the lower energy and power density and therefore higher weight of lead-acid batteries are not as critical as, for example, in electric transportation[9]:4,9 Other rechargeable batteries considered for distributed PV systems include sodium–sulfur and vanadium redox batteries, two prominent types of a molten salt and a flow battery, respectively.[9]:4 In 2015, Tesla Motors launched the Powerwall, a rechargeable lithium-ion battery with the aim to revolutionize energy consumption.[84]
PV systems with an integrated battery solution also need a charge controller, as the varying voltage and current from the solar array requires constant adjustment to prevent damage from overcharging.[85] Basic charge controllers may simply turn the PV panels on and off, or may meter out pulses of energy as needed, a strategy called PWM or pulse-width modulation. More advanced charge controllers will incorporate MPPT logic into their battery charging algorithms. Charge controllers may also divert energy to some purpose other than battery charging. Rather than simply shut off the free PV energy when not needed, a user may choose to heat air or water once the battery is full.
Monitoring and metering
The metering must be able to accumulate energy units in both directions, or two meters must be used. Many meters accumulate bidirectionally, some systems use two meters, but a unidirectional meter (with detent) will not accumulate energy from any resultant feed into the grid.[86] In some countries, for installations over 30 kWp a frequency and a voltage monitor with disconnection of all phases is required. This is done where more solar power is being generated than can be accommodated by the utility, and the excess can not either be exported or stored. Grid operators historically have needed to provide transmission lines and generation capacity. Now they need to also provide storage. This is normally hydro-storage, but other means of storage are used. Initially storage was used so that baseload generators could operate at full output. With variable renewable energy, storage is needed to allow power generation whenever it is available, and consumption whenever needed.
The two variables a grid operator have are storing electricity for when it is needed, or transmitting it to where it is needed. If both of those fail, installations over 30kWp can automatically shut down, although in practice all inverters maintain voltage regulation and stop supplying power if the load is inadequate. Grid operators have the option of curtailing excess generation from large systems, although this is more commonly done with wind power than solar power, and results in a substantial loss of revenue.[87] Three-phase inverters have the unique option of supplying reactive power which can be advantageous in matching load requirements.[88]
Photovoltaic systems need to be monitored to detect breakdown and optimize operation. There are several photovoltaic monitoring strategies depending on the output of the installation and its nature. Monitoring can be performed on site or remotely. It can measure production only, retrieve all the data from the inverter or retrieve all of the data from the communicating equipment (probes, meters, etc.). Monitoring tools can be dedicated to supervision only or offer additional functions. Individual inverters and battery charge controllers may include monitoring using manufacturer specific protocols and software.[89] Energy metering of an inverter may be of limited accuracy and not suitable for revenue metering purposes. A third-party data acquisition system can monitor multiple inverters, using the inverter manufacturer's protocols, and also acquire weather-related information. Independent smart meters may measure the total energy production of a PV array system. Separate measures such as satellite image analysis or a solar radiation meter (a pyranometer) can be used to estimate total insolation for comparison.[90] Data collected from a monitoring system can be displayed remotely over the World Wide Web, such as OSOTF.[91][92][93][94]
Otros sistemas
This section includes systems that are either highly specialized and uncommon or still an emerging new technology with limited significance. However, standalone or off-grid systems take a special place. They were the most common type of systems during the 1980s and 1990s, when PV technology was still very expensive and a pure niche market of small scale applications. Only in places where no electrical grid was available, they were economically viable. Although new stand-alone systems are still being deployed all around the world, their contribution to the overall installed photovoltaic capacity is decreasing. In Europe, off-grid systems account for 1 percent of installed capacity. In the United States, they account for about 10 percent. Off-grid systems are still common in Australia and South Korea, and in many developing countries.[8]:14
CPV
Concentrator photovoltaics (CPV) and high concentrator photovoltaic (HCPV) systems use optical lenses or curved mirrors to concentrate sunlight onto small but highly efficient solar cells. Besides concentrating optics, CPV systems sometime use solar trackers and cooling systems and are more expensive.
Especially HCPV systems are best suited in location with high solar irradiance, concentrating sunlight up to 400 times or more, with efficiencies of 24–28 percent, exceeding those of regular systems. Various designs of systems are commercially available but not very common. However, ongoing research and development is taking place.[1]:26
CPV is often confused with CSP (concentrated solar power) that does not use photovoltaics. Both technologies favor locations that receive much sunlight and are directly competing with each other.
Hybrid
A hybrid system combines PV with other forms of generation, usually a diesel generator. Biogas is also used. The other form of generation may be a type able to modulate power output as a function of demand. However more than one renewable form of energy may be used e.g. wind. The photovoltaic power generation serves to reduce the consumption of non renewable fuel. Hybrid systems are most often found on islands. Pellworm island in Germany and Kythnos island in Greece are notable examples (both are combined with wind).[95][96] The Kythnos plant has reduced diesel consumption by 11.2%.[97]
In 2015, a case-study conducted in seven countries concluded that in all cases generating costs can be reduced by hybridising mini-grids and isolated grids. However, financing costs for such hybrids are crucial and largely depend on the ownership structure of the power plant. While cost reductions for state-owned utilities can be significant, the study also identified economic benefits to be insignificant or even negative for non-public utilities, such as independent power producers.[98][99]
There has also been work showing that the PV penetration limit can be increased by deploying a distributed network of PV+CHP hybrid systems in the U.S.[100] The temporal distribution of solar flux, electrical and heating requirements for representative U.S. single family residences were analyzed and the results clearly show that hybridizing CHP with PV can enable additional PV deployment above what is possible with a conventional centralized electric generation system. This theory was reconfirmed with numerical simulations using per second solar flux data to determine that the necessary battery backup to provide for such a hybrid system is possible with relatively small and inexpensive battery systems.[101] In addition, large PV+CHP systems are possible for institutional buildings, which again provide back up for intermittent PV and reduce CHP runtime.[102]
- PVT system (hybrid PV/T), also known as photovoltaic thermal hybrid solar collectors convert solar radiation into thermal and electrical energy. Such a system combines a solar (PV) module with a solar thermal collector in a complementary way.
- CPVT system. A concentrated photovoltaic thermal hybrid (CPVT) system is similar to a PVT system. It uses concentrated photovoltaics (CPV) instead of conventional PV technology, and combines it with a solar thermal collector.
- CPV/CSP system. A novel solar CPV/CSP hybrid system has been proposed, combining concentrator photovoltaics with the non-PV technology of concentrated solar power (CSP), or also known as concentrated solar thermal.[103]
- PV diesel system. It combines a photovoltaic system with a diesel generator.[104] Combinations with other renewables are possible and include wind turbines.[105]
Floating solar arrays
Floating solar arrays are PV systems that float on the surface of drinking water reservoirs, quarry lakes, irrigation canals or remediation and tailing ponds. These systems are called "floatovoltaics" when used only for electrical production or "aquavoltaics" when such systems are used to synergistically enhance aquaculture.[106] A small number of such systems exist in France, India, Japan, South Korea, the United Kingdom, Singapore and the United States.[107][108][109][110][111]
The systems are said to have advantages over photovoltaics on land. The cost of land is more expensive, and there are fewer rules and regulations for structures built on bodies of water not used for recreation. Unlike most land-based solar plants, floating arrays can be unobtrusive because they are hidden from public view. They achieve higher efficiencies than PV panels on land, because water cools the panels. The panels have a special coating to prevent rust or corrosion.[112]
In May 2008, the Far Niente Winery in Oakville, California, pioneered the world's first floatovoltaic system by installing 994 solar PV modules with a total capacity of 477 kW onto 130 pontoons and floating them on the winery's irrigation pond.[113] The primary benefit of such a system is that it avoids the need to sacrifice valuable land area that could be used for another purpose. In the case of the Far Niente Winery, it saved 0.75 acres (0.30 ha) that would have been required for a land-based system.[114] Another benefit of a floatovoltaic system is that the panels are kept at a cooler temperature than they would be on land, leading to a higher efficiency of solar energy conversion. The floating PV array also reduces the amount of water lost through evaporation and inhibits the growth of algae.[115]
Utility-scale floating PV farms are starting to be built. The multinational electronics and ceramics manufacturer Kyocera will develop the world's largest, a 13.4 MW farm on the reservoir above Yamakura Dam in Chiba Prefecture[116] using 50,000 solar panels.[117][118] Salt-water resistant floating farms are also being considered for ocean use, with experiments in Thailand.[119] The largest so far announced floatovoltaic project is a 350 MW power station in the Amazon region of Brazil.[120]
Direct current grid
DC grids are found in electric powered transport: railways trams and trolleybuses. A few pilot plants for such applications have been built, such as the tram depots in Hannover Leinhausen, using photovoltaic contributors[121] and Geneva (Bachet de Pesay).[122] The 150 kWp Geneva site feeds 600 V DC directly into the tram/trolleybus electricity network whereas before it provided about 15% of the electricity at its opening in 1999.
Standalone
A stand-alone or off-grid system is not connected to the electrical grid. Standalone systems vary widely in size and application from wristwatches or calculators to remote buildings or spacecraft. If the load is to be supplied independently of solar insolation, the generated power is stored and buffered with a battery.[123] In non-portable applications where weight is not an issue, such as in buildings, lead acid batteries are most commonly used for their low cost and tolerance for abuse.
A charge controller may be incorporated in the system to avoid battery damage by excessive charging or discharging. It may also help to optimize production from the solar array using a maximum power point tracking technique (MPPT). However, in simple PV systems where the PV module voltage is matched to the battery voltage, the use of MPPT electronics is generally considered unnecessary, since the battery voltage is stable enough to provide near-maximum power collection from the PV module. In small devices (e.g. calculators, parking meters) only direct current (DC) is consumed. In larger systems (e.g. buildings, remote water pumps) AC is usually required. To convert the DC from the modules or batteries into AC, an inverter is used.
In agricultural settings, the array may be used to directly power DC pumps, without the need for an inverter. In remote settings such as mountainous areas, islands, or other places where a power grid is unavailable, solar arrays can be used as the sole source of electricity, usually by charging a storage battery. Stand-alone systems closely relate to microgeneration and distributed generation.
- Pico PV systems
- The smallest, often portable photovoltaic systems are called pico solar PV systems, or pico solar. They mostly combine a rechargeable battery and charge controller, with a very small PV panel. The panel's nominal capacity is just a few watt-peak (1–10 W p) and its area less than 0.1 square metres (1 sq ft) in size. A large range of different applications can be solar powered such as music players, fans, portable lamps, security lights, solar lighting kits, solar lanterns and street light (see below), phone chargers, radios, or even small, seven-inch LCD televisions, that run on less than ten watts. As it is the case for power generation from pico hydro, pico PV systems are useful in small, rural communities that require only a small amount of electricity. Since the efficiency of many appliances have improved considerably, in particular due to the usage of LED lights and efficient rechargeable batteries, pico solar has become an affordable alternative, especially in the developing world. [124] The metric prefix pico- stands for a trillionth to indicate the smallness of the system's electric power.
- Solar street lights
- Solar street lights raised light sources which are powered by photovoltaic panels generally mounted on the lighting structure. The solar array of such off-grid PV system charges a rechargeable battery, which powers a fluorescent or LED lamp during the night. Solar street lights are stand-alone power systems, and have the advantage of savings on trenching, landscaping, and maintenance costs, as well as on the electric bills, despite their higher initial cost compared to conventional street lighting. They are designed with sufficiently large batteries to ensure operation for at least a week and even in the worst situation, they are expected to dim only slightly.
- Telecommunication and signaling
- Solar PV power is ideally suited for telecommunication applications such as local telephone exchange, radio and TV broadcasting, microwave and other forms of electronic communication links. In most telecommunication application, storage batteries are already in use and the electrical system is basically DC. In hilly and mountainous terrain, radio and TV signals may not reach as they get blocked or reflected back due to undulating terrain. At these locations, low power transmitters are installed to receive and retransmit the signal for local population. [125]
- Solar vehicles
- Solar vehicle, whether ground, water, air or space vehicles may obtain some or all of the energy required for their operation from the sun. Surface vehicles generally require higher power levels than can be sustained by a practically sized solar array, so a battery assists in meeting peak power demand, and the solar array recharges it. Space vehicles have successfully used solar photovoltaic systems for years of operation, eliminating the weight of fuel or primary batteries.
- Solar pumps
- One of the most cost effective solar applications is a solar powered pump, as it is far cheaper to purchase a solar panel than it is to run power lines. [126][127][128] They often meet a need for water beyond the reach of power lines, taking the place of a windmill or windpump. One common application is the filling of livestock watering tanks, so that grazing cattle may drink. Another is the refilling of drinking water storage tanks on remote or self-sufficient homes.
- Spacecraft
- Solar panels on spacecraft have been one of the first applications of photovoltaics since the launch of Vanguard 1 in 1958, the first satellite to use solar cells. Contrary to Sputnik, the first artificial satellite to orbit the planet, that ran out of batteries within 21 days due to the lack of solar-power, most modern communications satellites and space probes in the inner solar system rely on the use of solar panels to derive electricity from sunlight. [129][130]
- Do it yourself community
- With agrowing interest in environmentally friendly green energy, hobbyists in the DIY-community have endeavored to build their own solar PV systems from kits [131] or partly DIY. [132] Usually, the DIY-community uses inexpensive [133] or high efficiency systems [134] (such as those with solar tracking) to generate their own power. As a result, the DIY-systems often end up cheaper than their commercial counterparts. [135] Often the system is also connected to the regular power grid, using net metering instead of a battery for backup. These systems usually generate power amount of ~2 kW or less. Through the internet, the community is now able to obtain plans to (partly) construct the system and there is a growing trend toward building them for domestic requirements.
- Gallery of standalone systems
Profile picture of a mobile solar powered generator
Solar panels on a small yacht to charge 12 volt batteries up to 9 amps
A mobile charging station for electric vehicles in France
Artist's concept of the Juno spacecraft orbiting Jupiter - furthest spacecraft to be powered by solar cells
A lateral mark, Otago Harbour, NZ
Solar powered electric fence, in Harwood Northumberland, UK.
Solar sailor boat, Darling Harbour, Sydney, Australia.
Powering a Yurt in Mongolia
A solar calculator
A solar navigation light
Solar pathway lighting in winter (Steamboat Springs, US).
Solar powered lighthouse in Scotland
A small solar water pump system
Solar car. The Japanese winner of 2009 World Solar Challenge in Australia.
A solar cell phone charger
A solar-powered fan
Solar powered watch
A solar-powered trash compactor, Jersey City, U.S.
A solar sewage treatment plant in Santuari de Lluc, Spain
Solar Impulse, an electric aircraft
Rental station for shared bicycles, Budapest, Hungary
Costos y economía
in Japan, Germany and the United States ($/W)
The cost of producing photovotaic cells has dropped because of economies of scale in production and technological advances in manufacturing. For large-scale installations, prices below $1.00 per watt were common by 2012.[138] A price decrease of 50% had been achieved in Europe from 2006 to 2011 and there is a potential to lower the generation cost by 50% by 2020.[139] Crystal silicon solar cells have largely been replaced by less expensive multicrystalline silicon solar cells, and thin film silicon solar cells have also been developed at lower costs of production. Although they are reduced in energy conversion efficiency from single crystalline "siwafers", they are also much easier to produce at comparably lower costs.[140]
The table below shows the total (average) cost in US cents per kWh of electricity generated by a photovoltaic system.[141][142] The row headings on the left show the total cost, per peak kilowatt (kWp), of a photovoltaic installation. Photovoltaic system costs have been declining and in Germany, for example, were reported to have fallen to USD 1389/kWp by the end of 2014.[143] The column headings across the top refer to the annual energy output in kWh expected from each installed kWp. This varies by geographic region because the average insolation depends on the average cloudiness and the thickness of atmosphere traversed by the sunlight. It also depends on the path of the sun relative to the panel and the horizon. Panels are usually mounted at an angle based on latitude, and often they are adjusted seasonally to meet the changing solar declination. Solar tracking can also be utilized to access even more perpendicular sunlight, thereby raising the total energy output.
The calculated values in the table reflect the total (average) cost in cents per kWh produced. They assume a 10% total capital cost (for instance 4% interest rate, 1% operating and maintenance cost,[144] and depreciation of the capital outlay over 20 years). Normally, photovoltaic modules have a 25-year warranty.[145][146]
Cost of generated kilowatt-hour by a PV-System (US¢/kWh) depending on solar radiation and installation cost during 20 years of operation | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Installation cost in $ per watt | Insolation annually generated kilowatt-hours per installed kW-capacity (kWh/(kWp•y)) | ||||||||||||
2400 | 2200 | 2000 | 1800 | 1600 | 1400 | 1200 | 1000 | 800 | |||||
$0.20 | 0.8 | 0.9 | 1.0 | 1.1 | 1.3 | 1.4 | 1.7 | 2.0 | 2.5 | ||||
$0.60 | 2.5 | 2.7 | 3.0 | 3.3 | 3.8 | 4.3 | 5.0 | 6.0 | 7.5 | ||||
$1.00 | 4.2 | 4.5 | 5.0 | 5.6 | 6.3 | 7.1 | 8.3 | 10.0 | 12.5 | ||||
$1.40 | 5.8 | 6.4 | 7.0 | 7.8 | 8.8 | 10.0 | 11.7 | 14.0 | 17.5 | ||||
$1.80 | 7.5 | 8.2 | 9.0 | 10.0 | 11.3 | 12.9 | 15.0 | 18.0 | 22.5 | ||||
$2.20 | 9.2 | 10.0 | 11.0 | 12.2 | 13.8 | 15.7 | 18.3 | 22.0 | 27.5 | ||||
$2.60 | 10.8 | 11.8 | 13.0 | 14.4 | 16.3 | 18.6 | 21.7 | 26.0 | 32.5 | ||||
$3.00 | 12.5 | 13.6 | 15.0 | 16.7 | 18.8 | 21.4 | 25.0 | 30.0 | 37.5 | ||||
$3.40 | 14.2 | 15.5 | 17.0 | 18.9 | 21.3 | 24.3 | 28.3 | 34.0 | 42.5 | ||||
$3.80 | 15.8 | 17.3 | 19.0 | 21.1 | 23.8 | 27.1 | 31.7 | 38.0 | 47.5 | ||||
$4.20 | 17.5 | 19.1 | 21.0 | 23.3 | 26.3 | 30.0 | 35.0 | 42.0 | 52.5 | ||||
$4.60 | 19.2 | 20.9 | 23.0 | 25.6 | 28.8 | 32.9 | 38.3 | 46.0 | 57.5 | ||||
$5.00 | 20.8 | 22.7 | 25.0 | 27.8 | 31.3 | 35.7 | 41.7 | 50.0 | 62.5 | ||||
Notes:
|
System cost 2013
In its 2014 edition of the "Technology Roadmap: Solar Photovoltaic Energy" report, the International Energy Agency (IEA) published prices in US$ per watt for residential, commercial and utility-scale PV systems for eight major markets in 2013.[7]
USD/W | Australia | China | France | Germany | Italy | Japan | United Kingdom | United States |
---|---|---|---|---|---|---|---|---|
Residential | 1.8 | 1.5 | 4.1 | 2.4 | 2.8 | 4.2 | 2.8 | 4.9 |
Commercial | 1.7 | 1.4 | 2.7 | 1.8 | 1.9 | 3.6 | 2.4 | 4.5 |
Utility-scale | 2.0 | 1.4 | 2.2 | 1.4 | 1.5 | 2.9 | 1.9 | 3.3 |
Source: IEA – Technology Roadmap: Solar Photovoltaic Energy report[7]:15 |
Learning curve
Photovoltaic systems demonstrate a learning curve in terms of levelized cost of electricity (LCOE), reducing its cost per kWh by 32.6% for every doubling of capacity.[148][149][150] From the data of LCOE and cumulative installed capacity from International Renewable Energy Agency (IRENA) from 2010 to 2017,[149][150] the learning curve equation for photovoltaic systems is given as[148]
- LCOE : levelized cost of electricity (in USD/kWh)
- Capacity : cumulative installed capacity of photovoltaic systems (in MW)
Regulación
Standardization
Increasing use of photovoltaic systems and integration of photovoltaic power into existing structures and techniques of supply and distribution increases the need for general standards and definitions for photovoltaic components and systems.[citation needed] The standards are compiled at the International Electrotechnical Commission (IEC) and apply to efficiency, durability and safety of cells, modules, simulation programs, plug connectors and cables, mounting systems, overall efficiency of inverters etc.[151]
National regulations
- United Kingdom
In the UK, PV installations are generally considered permitted development and don't require planning permission. If the property is listed or in a designated area (National Park, Area of Outstanding Natural Beauty, Site of Special Scientific Interest or Norfolk Broads) then planning permission is required.[152]
- United States
In the United States, article 690 of the National Electric Code provides general guidelines for the installation of photovoltaic systems; these may be superseded by local laws and regulations. Often a permit is required necessitating plan submissions and structural calculations before work may begin. Additionally, many locales require the work to be performed under the guidance of a licensed electrician.
In the United States, the Authority Having Jurisdiction (AHJ) will review designs and issue permits, before construction can lawfully begin. Electrical installation practices must comply with standards set forth within the National Electrical Code (NEC) and be inspected by the AHJ to ensure compliance with building code, electrical code, and fire safety code. Jurisdictions may require that equipment has been tested, certified, listed, and labeled by at least one of the Nationally Recognized Testing Laboratories (NRTL). .[153] In the US, many localities require a permit to install a photovoltaic system. A grid-tied system normally requires a licensed electrician to connect between the system and the grid-connected wiring of the building.[154] Installers who meet these qualifications are located in almost every state.[153] Several states prohibit homeowners' associations from restricting solar devices.[155][156][157]
- Spain
Although Spain generates around 40% of its electricity via photovoltaic and other renewable energy sources, and cities such as Huelva and Seville boast nearly 3,000 hours of sunshine per year, in 2013 Spain issued a solar tax to account for the debt created by the investment done by the Spanish government. Those who do not connect to the grid can face up to a fine of 30 million euros (US$40 million).[158][159] Such measures were finally withdrawn by 2018, when new legislation was introduced banning any taxes on renewable energy self-consumption.[160]
Limitaciones
Pollution and energy in PV production
PV has been a well-known method of generating clean, emission free electricity. PV systems are often made of PV modules and inverter (changing DC to AC). PV modules are mainly made of PV cells, which has no fundamental difference to the material for making computer chips. The process of producing PV cells (computer chips) is energy intensive and involves highly poisonous and environmental toxic chemicals. There are few PV manufacturing plants around the world producing PV modules with energy produced from PV. This measure greatly reduces the carbon footprint during the manufacturing process. Managing the chemicals used in the manufacturing process is subject to the factories' local laws and regulations.
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, 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, there have been more than 30% of households with rooftop PV by the end of 2017. The famous Californian 2020 duck curve appears very often for a lot of communities from 2015 onwards. An over-voltage issue may come out as the electricity flows back to the network.[161] There are solutions to manage the over voltage issue, such as regulating PV inverter power factor, new voltage and energy control equipment at electricity distributor level, re-conductor the electricity wires, demand side management, etc. There are often limitations and costs related to these solutions.
Implication onto electricity bill management and energy investment
Customers have different specific situations, e.g. different comfort/convenience needs, different electricity tariffs, or different usage patterns. An electricity tariff may have a few elements, such as daily access and metering charge, energy charge (based on kWh, MWh) or peak demand charge (e.g. a price for the highest 30min energy consumption in a month). PV is a promising option for reducing energy charge when electricity price is reasonably high and continuously increasing, such as in Australia and Germany. However, for sites with peak demand charge in place, PV may be less attractive if peak demands mostly occur in the late afternoon to early evening, for example residential communities. Overall, energy investment is largely an economic decision and investment decisions are based on systematical evaluation of options in operational improvement, energy efficiency, onsite generation and energy storage.[162][163]
Ver también
- Energy demand management
- List of photovoltaic power stations
- List of rooftop photovoltaic installations
- Photovoltaic power stations
- Renewable energy
- Rooftop photovoltaic power station
- Solar energy
- Solar vehicle
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enlaces externos
- Photovoltaic Energy Factsheet by the University of Michigan's Center for Sustainable Systems
- Home Power Magazine http://www.homepower.com/
- Solar project management
- Photovoltaic Systems Engineering
- Best Practices for Siting Solar Photovoltaics on Municipal Solid Waste Landfills: A Study Prepared in Partnership with the Environmental Protection Agency for the RE-Powering America's Land Initiative: Siting Renewable Energy on Potentially Contaminated Land and Mine Sites National Renewable Energy Laboratory