PV module electricity generating capacity increases with the number of cells in the module or in the surface area of the module. PV modules can be connected in groups to form a PV array. A PV array can be composed of two or hundreds of PV modules. The number of PV modules connected in a PV array determines the total amount of electricity the array can generate.
Photovoltaic cells generate direct current DC electricity. This DC electricity can be used to charge batteries that, in turn, power devices that use direct current electricity. Nearly all electricity is supplied as alternating current AC in electricity transmission and distribution systems.
PV cells and modules will produce the largest amount of electricity when they are directly facing the sun. PV modules and arrays can use tracking systems that move the modules to constantly face the sun, but these systems are expensive. Most PV systems have modules in a fixed position with the modules facing directly south in the northern hemisphere—directly north in the southern hemisphere and at an angle that optimizes the physical and economic performance of the system. Solar photovoltaic cells are grouped in panels modules , and panels can be grouped into arrays of different sizes to produce small to large amounts of electricity, such as for powering water pumps for livestock water, for providing electricity for homes, or for utility-scale electricity generation.
The smallest photovoltaic systems power calculators and wristwatches. Larger systems can provide electricity to pump water, to power communications equipment, to supply electricity for a single home or business, or to form large arrays that supply electricity to thousands of electricity consumers. The first practical PV cell was developed in by Bell Telephone researchers.
Beginning in the late s, PV cells were used to power U. By the late s, PV panels were providing electricity in remote, or off-grid , locations that did not have electric power lines. Technological advances, lower costs for PV systems, and various financial incentives and government policies have helped to greatly expand PV use since the mids. Hundreds of thousands of grid-connected PV systems are now installed in the United States. The U. Energy Information Administration EIA estimates that solar electricity generation at utility-scale PV power plants increased from 76 million kilowatthours kWh in to about 88 billion kWh in EIA estimates that about 42 billion kWh were generated by small-scale grid-connected PV systems in , up from 11 billion kWh in Utility-scale power plants have at least 1, kilowatts or one megawatt MW of electricity generation capacity and small-scale systems have less than one MW generation capacity.
Most small-scale PV systems are located on buildings and are sometimes called rooftop PV systems. Solar explained Photovoltaics and electricity. What is energy? Units and calculators. Use of energy. When the sun shines onto a solar panel, energy from the sunlight is absorbed by the PV cells in the panel.
This energy creates electrical charges that move in response to an internal electrical field in the cell, causing electricity to flow. Concentrating solar-thermal power CSP systems use mirrors to reflect and concentrate sunlight onto receivers that collect solar energy and convert it to heat, which can then be used to produce electricity or stored for later use.
It is used primarily in very large power plants. These solar energy systems must be integrated into homes, businesses, and existing electrical grids with varying mixtures of traditional and other renewable energy sources. A number of non-hardware costs, known as soft costs, also impact the cost of solar energy.
These costs include permitting, financing, and installing solar, as well as the expenses solar companies incur to acquire new customers, pay suppliers, and cover their bottom line. For rooftop solar energy systems, soft costs represent the largest share of total costs. Solar energy can help to reduce the cost of electricity, contribute to a resilient electrical grid, create jobs and spur economic growth, generate back-up power for nighttime and outages when paired with storage, and operate at similar efficiency on both small and large scales.
Solar energy systems come in all shapes and sizes. Residential systems are found on rooftops across the United States, and businesses are also opting to install solar panels.
During the energy crisis in the s, photovoltaic technology gained recognition as a source of power for non-space applications. The diagram above illustrates the operation of a basic photovoltaic cell, also called a solar cell. Solar cells are made of the same kinds of semiconductor materials, such as silicon, used in the microelectronics industry.
For solar cells, a thin semiconductor wafer is specially treated to form an electric field, positive on one side and negative on the other. When light energy strikes the solar cell, electrons are knocked loose from the atoms in the semiconductor material. If electrical conductors are attached to the positive and negative sides, forming an electrical circuit, the electrons can be captured in the form of an electric current -- that is, electricity. This electricity can then be used to power a load, such as a light or a tool.
A number of solar cells electrically connected to each other and mounted in a support structure or frame is called a photovoltaic module. Modules are designed to supply electricity at a certain voltage, such as a common 12 volts system. The current produced is directly dependent on how much light strikes the module.
Multiple modules can be wired together to form an array. In general, the larger the area of a module or array, the more electricity that will be produced.
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