Solar panels or photovoltaic (PV) panels are designed to convert sunlight directly into electricity. They're composed of multiple smaller units, photovoltaic cells, made of semiconductor materials like silicon.
The cells are interconnected and encapsulated in a protective casing of glass, zinc and aluminum for durability. Silicon is the most valuable material in solar panels due to its semi-conductive properties.
The most significant innovation in robotics and automation is robots using solar energy photovoltaic technology. This makes the robots self-generating; they create their own energy.
Solar power is erratic, one drawback in sun-driven robotics. It currently requires use of big panels to generate small amounts of energy.
Background
Discovery of the photovoltaic effect and invention of the first solar cell are both by 19-year-old Alexandre-Edmond Becquerel (1820 - 1891) in 1839. He's later the father of Henri Becquerel, who discovers radioactivity in 1896.
Edmond's discoveries come into use in the 1950s. At first, solar panels power remote pieces of electrical equipment, and satellites in space.
Vanguard 1 (above), created by NASA, is the world's first solar-powered satellite. It's launched on St. Patrick's Day, March 17 1958. It's the fourth satellite ever sent into space.
By the 1980s, solar power is accessible to the public. Federal legislation offers incentives and tax credits for the installation of renewable energy in residences. In 1983, solar cell sales surpass $250 million.
In 2023 the global solar cell market is valued at USD 127.51 billion. It's projected to reach USD 730.74 billion by 2034.
The Photovoltaic Effect: How Solar Panels Work
The principle behind solar panel operation is the photovoltaic effect, the phenomenon discovered by Becquerel. The process follows several steps.
Sunlight Absorption: Sunlight is a stream of photons or light particles. As it hits the solar panel, the photons are absorbed by the semiconductor material, usually silicon. Silicon makes up 95% of the market share for solar cell semiconductor materials. Cadmium telluride is the rest.
A coating of zinc oxide protects the panels from too much UV radiation. Zinc oxide's distinct characteristics, including superior electron mobility, also improve efficiency of the solar cells.
Electron Excitation: The absorption of energy dislodges electrons from their atoms within the silicon, freeing them to move around.
Creating an Electric Field: To guide the movement of the newly freed electrons and create a useful electrical current, the silicon is treated with impurities through doping. It creates two distinct layers in each cell:
N-type silicon: Doped with elements like phosphorus, which have extra electrons. This layer has a surplus of negatively charged electrons.
P-type silicon: Doped with elements like boron, which create electron "holes," or vacancies where electrons should be. This layer has a surplus of positively charged holes.
The junction between these two layers creates an electric field (diagram below). This becomes a one-way path for electrons. P-type and N-type semiconductors are needed for functioning of electronic devices.
Electron Flow & Current Generation: When sunlight dislodges electrons, the electric field at the junction pushes the electrons towards the N-type layer and pushes the "holes" towards the P-type layer. It creates a flow of electrons, essentially an electric current.
Extracting Electricity: Metal contacts are located on top and bottom of the solar cell. They collect the generated electrons and conduct them through wires to form an electrical circuit.
This direct current (DC) electricity can be used to power devices. Otherwise it can be converted into alternating current (AC) using an inverter, making it compatible with the standard electrical grid.
Inverter: Converts the DC electricity generated by the panels into AC electricity for use in homes and businesses or for feeding into the grid.
In solar energy systems, inverters transform the DC electricity produced by solar panels into AC electricity. This is needed by most household appliances and devices.
Different types of inverters exist, like string inverters and microinverters, each designed for certain configurations. Microinverters enhance performance in systems where the panels are shaded.
Other Solar Panel Parts
Mounting System: Secures the panels to a roof or ground-based structure, ensuring optimal exposure to sunlight.
Wiring and Connectors: Connect the panels to the inverter and the rest of the electrical system.
Monitoring System: Tracks the system's performance, providing data on energy production and potential issues.
Battery Storage: Stores excess energy generated during the day for later use.
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