Molly Ayala
Photovoltaic electricity, also known as solar PV, is a form of decentralized electricity generation that converts light into electricity using semiconducting materials. The term photovoltaic comes from the Greek word phōs, meaning light, and volt, the unit of electromotive force. Photovoltaic systems are designed to supply usable solar power and consist of solar panels that absorb and convert sunlight into electricity, a solar inverter to convert the electric current from direct to alternating, and other electrical accessories. PV cells are commonly called solar cells and are often made from silicon, which conducts electricity more than an insulator but less than a metal. These cells are incredibly thin and can be flexible and lightweight, making them ideal for portable applications. PV systems are carbon-negative over their lifespan and help mitigate climate change by emitting much less carbon dioxide than fossil fuels.
| Characteristics | Values |
|---|---|
| Definition | Conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect |
| Process | Light (photons) is converted to electricity (voltage) |
| First working solar cell | Created in 1954 by scientists at Bell Laboratories |
| Composition | Solar cells are strung together to form a photovoltaic module |
| Solar cell material | Semiconductor material, typically silicon |
| Solar cell thickness | About the thickness of four human hairs |
| Solar cell power | 1-2 Watts |
| Solar cell efficiency | 12-21% for silicon-based PVs; 12% for organic PVs |
| Solar cell applications | Powering satellites, UAVs, calculators, watches, residential/commercial buildings, etc. |
| PV system components | Solar panels, solar inverter, mounting, cabling, electrical accessories |
| PV system sizes | Residential (2-10 kWp) to solar power stations (up to tens of MWp) |
| PV system installations | Ground-mounted, rooftop-mounted, wall-mounted, floating |
| PV system advantages | Carbon-negative, no pollution/emissions, scalable, silicon availability |
| PV market growth | Fast-growing, approaching 200 GW in 2015; expected to be world's largest electricity source by 2050 |
| PV cost | Continuously declining due to technological advances and manufacturing scale |
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What You'll Learn
Photovoltaic systems
A photovoltaic system consists of multiple components, including solar panels, a solar inverter, mounting equipment, cabling, and other electrical accessories. Solar panels absorb and convert sunlight into electricity, while the solar inverter changes the electric current from direct to alternating. The mounting equipment and cabling are necessary for setting up a functional system.
The basic building block of a photovoltaic system is the PV cell, commonly known as a solar cell. These cells are typically made of semiconductor materials, such as silicon, and they can be as thin as four human hairs. When photons from sunlight strike the PV cell, they can be reflected, pass through, or absorbed by the semiconductor material. The absorption of photons by the semiconductor material generates electricity by dislodging electrons from the material's atoms. These free electrons move towards the front surface of the PV cell, creating an electrical charge imbalance, which results in a voltage potential similar to that of a battery's terminals.
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Solar photovoltaic cells
Photovoltaic (PV) cells, commonly known as solar cells, are non-mechanical devices that convert sunlight directly into electricity. PV cells are composed of semiconductor materials, such as silicon, which can conduct electricity better than insulators but not as well as good conductors like metals. When light shines on a PV cell, it may be reflected, absorbed, or pass through the cell. When the semiconductor material absorbs enough sunlight, it absorbs the light's energy and transfers it to negatively charged particles called electrons, which flow through the material as an electrical current. This current can then be extracted through conductive metal contacts and used to power homes or other electrical devices.
The first practical PV cell was developed in 1954 by Bell Telephone researchers and was used to power U.S. space satellites beginning in the late 1950s. Since then, technological advances, lower costs, and government policies have greatly expanded PV use. PV cells are now used in a variety of applications, including residential, commercial, and utility-scale electricity generation, as well as in agricultural and healthcare settings.
PV cells are typically assembled together to form solar photovoltaic panels or modules, which are then grouped into arrays of different sizes. These arrays can be mounted on the ground, rooftops, walls, or even floating bodies of water. The efficiency of PV cells has also improved significantly over time, with commercially available PV panels averaging around 15% efficiency in 2015 and approaching 25% more recently.
There are several types of PV materials and technologies used in solar cells, each with its own advantages and disadvantages. Silicon is the most common semiconductor material, offering high efficiency, low cost, and long lifetime. Other materials such as CdTe, CIGS, and perovskite are also used in thin-film solar cells, which can be more cost-effective but may have lower efficiencies. Additionally, concentration PV (CPV) focuses sunlight onto a small area using mirrors or lenses, increasing efficiency but requiring more expensive materials and manufacturing techniques.
Overall, solar photovoltaic cells play a crucial role in harnessing solar energy and converting it into a usable form of electricity, offering a clean and scalable source of power that contributes to mitigating climate change.
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Photovoltaic effect
Photovoltaic (PV) systems employ solar modules, each comprising multiple solar cells, to generate electrical power. PV systems convert light directly into electricity, and the term "photovoltaic" refers to this conversion of light (photons) to electricity (voltage), known as the photovoltaic effect.
The photovoltaic effect is a phenomenon studied across physics, photochemistry, and electrochemistry. The effect was first exploited in 1954 by scientists at Bell Laboratories, who created a working solar cell made of silicon that generated an electric current when exposed to sunlight. These solar cells soon found applications in calculators, watches, and satellites.
The photovoltaic effect occurs when photons strike a PV cell and are either reflected, pass through, or are absorbed by the semiconductor material. Only the photons that are absorbed provide energy to generate electricity. This absorption of light by the semiconductor material transfers energy to negatively charged particles, or electrons, dislodging them from the atoms of the material. The movement of these electrons creates an imbalance of electrical charge between the front and back surfaces of the PV cell, resulting in a voltage potential similar to the negative and positive terminals of a battery.
When the front surface of the PV cell becomes enriched with electrons, electrical conductors on the cell absorb them. Connecting these conductors to an electrical circuit with an external load, such as a battery, allows electricity to flow through the circuit.
PV cells are typically assembled into larger modules, or panels, that can be installed on the roofs of buildings or ground-mounted. These panels are then connected to form a solar system, with the solar array referring specifically to the collection of panels. PV systems can be ground-mounted, rooftop-mounted, wall-mounted, or floating, and they may be fixed or use a solar tracker to follow the sun's path to optimise electricity generation.
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Photovoltaic materials
Photovoltaic (PV) materials are semiconductor materials that convert light into electricity. This is known as the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. PV materials are used in solar modules, which are composed of solar cells that generate electrical power.
The most common PV material is silicon, which is found in around 95% of modules sold today. Silicon PV systems are made by processing mined quartz into polysilicon, which is then melted down with small amounts of boron, a group III element, to make a p-type semiconductor rich in electron holes. An ingot of this solution is grown from the liquid polycrystalline and wafers of the semiconductor material are cut from the bulk material.
Other PV materials include cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS), which are thin-film PV semiconductors. CdTe is the second-most common PV material and can be manufactured using low-cost processes, but its efficiency is lower than that of silicon. CIGS cells have optimal properties for a PV material and high efficiencies in lab settings, but the complexity of combining four elements makes large-scale manufacturing challenging. Both CdTe and CIGS require more protection than silicon to enable long-lasting outdoor operation.
Another type of PV material is organic solar cells, which use molecules to absorb photons and convert them into electric charges without the need for intermolecular transport or electronic excitation. This imposes stringent demands on the optical and electronic properties of the semiconductor, such as its band gap and band position, as well as charge-carrier mobility and the recombination time of photogenerated charges.
The development of new semiconductors is expected to reduce production costs significantly. To improve the efficiency of PV systems, manufacturers can simply add more photovoltaic components, taking advantage of economies of scale.
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Photovoltaic applications
Photovoltaic (PV) cells, commonly called solar cells, are non-mechanical devices that convert sunlight directly into electricity. PV cells are made of semiconductor material. When photons from the sun strike the cell, they are either reflected, pass through, or are absorbed by the semiconductor material. When the semiconductor absorbs enough sunlight, electrons are dislodged from the material's atoms, generating electricity.
PV cells are electrically connected in a packaged, weather-tight PV panel (sometimes called a module). PV panels can be grouped into arrays of different sizes to power water pumps, power individual homes, or provide utility-scale electricity generation. PV installations may be ground-mounted, rooftop-mounted, wall-mounted, or floating. PV material can be integrated into a building's structure as windows, roof tiles, or cladding to serve a dual purpose.
PV technology has a wide range of applications. In rural areas, PV can be used to power homes, villages in developing nations, lighthouses, offshore oil platforms, desalination plants, and remote health clinics. In urban areas, PV can power stand-alone devices such as parking meters, temporary traffic signs, emergency phones, and radio transmitters. PV can also be used for power generation at various scales, from municipal to regional grids.
PV has been a primary power source for Earth-orbiting satellites and has supplied power for ventures such as the International Space Station and surface rovers on the Moon and Mars. Lightweight, flexible thin-film PV can be used in defence applications, such as charging electronic equipment in the field or at remote bases. PV can also provide auxiliary power for vehicles, such as cars and boats.
Indoor PV has the potential to supply power to the Internet of Things, such as smart sensors and communication devices, providing a solution to battery limitations. Ambient indoor lighting, such as LEDs and fluorescent lights, emits enough radiation to power small electronic devices or devices with low-power demand.
In developing countries, PV is increasingly being used to provide solar-powered lighting to replace kerosene lamps. Solar-powered 3D printers are another example of off-grid solar energy use.
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Frequently asked questions
Photovoltaic electricity, also known as solar PV, is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect. This effect was first exploited in 1954 by scientists at Bell Laboratories, who created a working solar cell made of silicon.
Photovoltaic systems consist of solar panels that absorb and convert sunlight into electricity. The panels are made of solar cells, which are the individual semiconducting units that convert light into electricity. The more solar cells a panel has, the more electricity it can generate.
Photovoltaic electricity is used for power generation at various scales, from powering small devices like calculators and watches to powering homes, farms, and even countries. PV systems are also used in attempts to integrate solar power into public infrastructure.
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