A solar panel is a device that converts sunlight into electricity by using multiple solar modules that consist of 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 electricity, which can be used to power various devices or be stored in batteries. Solar panels can be known as solar cell panels, or solar electric panels. Solar panels are usually arranged in groups called arrays or systems. A photovoltaic system consists of one or more solar panels, an inverter that converts direct current electricity to alternating current where it is necessary, and sometimes other components such as charge controllers, meters, or solar trackers to maximize direct sunlight. Most panels are in solar farms or rooftop solar panels, which supply the electricity grid. Solar panels use a renewable and clean source of energy, and reduce greenhouse gas emissions compared to hydrocarbon-sourced energy. However, 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 space, often together with batteries.
History
Early developments In 1839, the ability of some materials to create an electrical charge from light exposure was first observed by the French physicist Edmond Becquerel. Though these initial solar cells were too inefficient for even simple electric devices, they were used as an instrument to measure light. 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. In 1881, the American inventor Charles Fritts created the first commercial solar cell, which was reported by Fritts as "continuous, constant and of considerable force not only by exposure to sunlight but also to dim, diffused daylight". However, these solar cells were still very inefficient for practical power production, especially compared to coal-fired power plants. In 1939, Russell Ohl created the solar cell design that is used in many modern solar panels. He patented his design in 1941. In 1954, this design was first used by Bell Labs to create the first commercially viable silicon solar cell.
Exponential growth
Falling costs have been the biggest factor in the recent exponential growth of Solar energy. Since 2010, the cost of solar photovoltaic electricity has fallen 85%. Solar panel installers saw significant growth between 2008 and 2013. Due to that growth, many solar-roof installations were not "ideal" to work with - they had to find solutions to shaded roofs and orientation difficulties. This challenge was initially addressed by the re-popularization of micro-inverters and later the invention of power optimizers. Solar panel manufacturers partnered with micro-inverter companies to create alternating current modules and power optimizer companies partnered with module manufacturers to create smart modules. In 2013 many solar panel manufacturers announced and began shipping their smart module solutions. Between 1992 and 2023, the worldwide usage of photovoltaics (PV) increased exponentially. During this period, it evolved from a niche market of small-scale applications to a mainstream electricity source. From 2016 to 2022, PV has seen an annual capacity and production growth rate of around 26%, doubling approximately every three years. By the end of 2022, the global cumulative installed PV capacity reached about 1,185 gigawatts (GW), supplying over 6% of global electricity demand, up from about 3% in 2019. The decreasing cost of solar panels is driving an increase in solar energy use in the Global South. Many countries in the Global South rely on expensive fossil fuel imports. Many homes and businesses are switching to solar energy to save money
Theory and construction
Photovoltaic modules consist of a large number of solar cells and use light energy from the Sun to generate electricity through the photovoltaic effect. Most modules use wafer-based crystalline silicon cells or thin-film cells. The structural (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. The cells and modules are usually connected electrically in series, one to another to increase the desired voltage output, and then in parallel to increase current output to create the solar panel. Most panels are rigid, but semi-flexible ones based on thin-film cells are also available. The power (in watts) of the solar panel is the voltage (in volts) multiplied by the current (in amperes), and depends both on the amount of light and on the electrical load connected to the panel. 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. 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 connectors to facilitate easy weatherproof connections to the rest of the system. A USB power interface can also be used. Solar panels also use metal frames consisting of racking components, brackets, reflector shapes, and troughs to better support the panel structure.
Cell connection techniques Solar cells need to be connected together by electrodes to form a module, with front electrodes blocking the solar cell front optical surface area slightly. To improve solar cell efficiency manufacturers maximize frontal surface area available for sunlight and improve sunlight absorption using chronologically adopted, varying rear electrode solar cell connection techniques:
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