What Does Pv Mean In Solar?

PV stands for “photovoltaic,” which refers to the process of converting light (photo) into electricity (voltage). PV cells, also known as solar cells, are the building blocks of photovoltaic solar panels that are used to convert energy from the sun into usable electricity.

The word photovoltaic comes from “photo,” meaning light, and “voltaic,” meaning electricity. So photovoltaic cells produce voltage when exposed to light. This makes them different from solar thermal technologies that produce heat from sunlight.

PV cells are made up of one or more layers of semiconducting material, most commonly silicon. When sunlight hits the cell, the energy knocks electrons loose in the semiconductor material, allowing them to flow freely and produce an electric current. This conversion of light (photons) to electricity (voltage) gives photovoltaics their name.

PV stands for photovoltaic. PV cells, also known as solar cells, are devices that convert sunlight into electricity using the photovoltaic effect.

How PV Cells Work

PV cells are made up of one or two layers of a semiconducting material, usually silicon. When sunlight hits the cell, photons from the sunlight are absorbed by the semiconducting material, causing electrons to break free from their atoms. This generates electron-hole pairs, which result in an electric field across the cell. The movement of these electrons in the electric field generates an electric current, which can then be used to power electrical devices.

The most common PV cell material is crystalline silicon, though other materials like cadmium telluride and copper indium gallium selenide are also used. The semiconducting materials have a crystal structure with electrons that are dislodged easily when sunlight strikes them. When dislodged, the electrons flow in one direction while the holes they leave behind flow in the opposite direction, generating an electrical current.

PV cells have one or more electric fields that act to drive the electrons freed by the photons. The buildup of charge creates a voltage, and when the PV cell is connected in a circuit, electrons can flow through this voltage to power electrical components. So in essence, PV cells can directly convert sunlight into electricity through semiconductor materials with unique electrical properties.

Types of PV Cells

There are three main types of photovoltaic (PV) cells used in solar panels: monocrystalline, polycrystalline, and thin film.

Monocrystalline PV Cells

Monocrystalline PV cells are made from silicon ingots, which are cylindrical blocks formed by melting pure silicon. Single crystal silicon cells have the highest efficiency rates since they are made from uniform silicon crystals.

Polycrystalline PV Cells

Polycrystalline PV cells are made from fragments of silicon ingots that are melted and poured into molds to form square wafers. They have lower silicon purity and are less efficient than monocrystalline cells.

Thin Film PV Cells

Thin film PV cells are made by depositing layers of photosensitive materials onto substrates like glass, plastic or metal. They are less efficient but cheaper to manufacture than crystalline silicon cells.

PV Cell Efficiency

Efficiency is a key metric used to evaluate PV cells. It measures the percentage of sunlight that is converted into electricity by the cell. The higher the efficiency, the more electricity that can be produced from the same sized cell.

Efficiency ranges vary based on PV cell type:

• Monocrystalline cells typically range from 15-22% efficiency.
• Polycrystalline cells are slightly less efficient, ranging from 13-17%.
• Amorphous silicon cells have lower efficiency around 6-9%.
• Emerging PV technologies like perovskites and organic cells have achieved over 20% efficiency in lab settings, but are not mass produced yet.

Why does efficiency matter? Higher efficiency means you can produce the same amount of electricity with a smaller PV system. This reduces installation costs per watt. However, the most efficient cells are not necessarily the best economic choice overall, as production costs also play a role.

PV Cell Durability

The lifespan and degradation rate of PV cells depends on several factors. Most solar panels come with a warranty of 25-30 years, during which time the panels are expected to maintain at least 80% of their original power output. However, many panels continue generating electricity at acceptable levels beyond the warranty period.

There are a few key factors that affect the durability and lifespan of PV cells:

• Quality of manufacturing – Higher quality manufacturing results in more durable panels.
• Type of PV material – Some materials like monocrystalline silicon deteriorate slower than others.
• Climate conditions – Extreme weather like high temperatures, humidity, and hail can accelerate degradation.
• UV exposure – Long-term exposure to sunlight causes slow degradation of the panels.
• Mechanical factors – Factors like wind, dirt buildup, and thermal cycles strain the panels over time.

Regular cleaning and maintenance of the panels can help minimize degradation by reducing dirt buildup and mechanical stress. PV panels are typically designed and tested to withstand up to 25 years of climatic factors and UV radiation. With proper care, many panels continue functioning beyond their warranty period, often producing 70-80% of original power even after 30 years.

PV Cell Costs

The cost of PV cells varies significantly depending on the type of cell and its efficiency. Some key factors that influence PV cell costs include:

• Manufacturing costs – Cells that are more complex or difficult to manufacture tend to have higher costs. For example, monocrystalline silicon cells require a more intensive purification and crystal growth process compared to other types.
• Raw materials – Silicon cells require high purity silicon, which increases costs. Thin film cells can use alternative semiconductor materials that may be cheaper.
• Efficiency – More efficient cells generate more electricity for the same surface area, spreading out upfront costs.
• Supply and demand – Mass manufacturing and technology improvements have substantially reduced PV cell costs over time. But shortages can drive up prices.

Monocrystalline silicon cells are the most efficient but also the most expensive, currently ranging from $0.37 – $0.50 per Watt. Polycrystalline silicon cells are cheaper at around $0.25 – $0.30 per Watt due to simpler manufacturing. Thin film cells using cadmium telluride are among the cheapest at around $0.22 per Watt, but have lower efficiency.

Over the last 10 years, average PV module costs have declined from around $2 per Watt in 2010 to under $0.40 per Watt today. Further cost reductions are expected with economies of scale and new production techniques lowering manufacturing expenses.

PV Cell Applications

PV cells have three major application areas – utility-scale solar farms, residential rooftop solar, and commercial/industrial solar installations.

Utility-Scale Solar Farms
Utility-scale solar farms, also known as solar power plants, involve installing large ground-mounted PV systems to generate electricity. These are usually in the multi-megawatt range, supplying power directly to the electricity grid. The solar farm may cover hundreds of acres and contain thousands of PV panels. These large-scale solar installations help utilities diversify their energy mix and provide renewable power to the grid.

Residential Rooftop Solar

Rooftop solar panels on homes allow homeowners to generate their own electricity. Excess power can be fed back to the grid. Rooftop residential systems are usually in the 3-10 kilowatt range. With net metering, any excess electricity sent back to the grid results in a credit that homeowners can use when their solar panels are not producing enough, such as at night. This allows households to reduce their overall electricity bills while also going green.

Commercial/Industrial Solar Installations
Businesses, factories, warehouses and other commercial facilities are also adding rooftop and ground-mounted solar systems to offset their energy usage. These systems can range from 10 kilowatts up to the megawatt scale. Solar helps reduce electric bills for commercial and industrial customers. It also helps them achieve sustainability goals. Some companies install solar to power their operations directly, while others do it to sell excess power back to the grid.

PV Cell Manufacturing

Photovoltaic cells are made from semiconducting materials like silicon that convert sunlight into electricity. The manufacturing process for PV cells generally consists of the following steps:

Purification of raw silicon – Metallurgical grade silicon is purified into solar grade silicon using processes like the Siemens method.

Ingot formation – The purified silicon is melted and cast into ingots or blocks.

Wafer slicing – The ingots are sliced into thin wafers using diamond wire saws or other wafer slicing techniques.

Cell fabrication – The silicon wafers undergo texturing, doping, deposition of anti-reflective coatings and metal contacts to form the PV cell.

Module assembly – The PV cells are connected and encapsulated into protective casings to form modules or panels.

The key players in PV cell manufacturing include large companies like JinkoSolar, JA Solar, Trina Solar, and LONGi from China. Other major manufacturers are based in South Korea, Malaysia, Taiwan and the United States.

Automation and quality control at all stages are critical for high performance and cost-effective PV cell and module production.

Future of PV

The future looks bright for photovoltaic technology. Scientists are working to improve the efficiency and lower the costs of PV cells through advances in materials and manufacturing techniques.

One area of focus is developing new materials that can absorb more of the sun’s light spectrum, generating more electricity from the same surface area. Perovskites are one emerging material showing potential to boost efficiency beyond silicon cells.

Researchers are also exploring techniques like stacking multiple ultra-thin layers of materials to absorb more light. Nanotechnology and quantum dot solar cells are other innovations that could dramatically increase efficiency in the future.

On the manufacturing side, companies are finding ways to produce PV films through printing press-style processes. This has the potential to lower material waste while scaling up production volume and driving down costs.

Startups are also innovating with new solar cell shapes, flexible PV materials, and solar windows that turn buildings into generators. With so many bright minds focused on solar, we can expect continuing advances that make PV a more accessible and competitive energy source worldwide.

Conclusion

In summary, photovoltaic (PV) cells play a critical role in renewable energy by converting sunlight into electricity. As solar power continues to expand globally, PV cell technology will remain at the heart of this growth. Ongoing advances in PV cell efficiency, durability, and cost-effectiveness have enabled solar to become cost-competitive with conventional power sources. With supportive policies and continued technology improvements, PV-generated solar electricity has immense potential to supply a substantial share of the world’s energy needs in a clean and sustainable manner. The unique ability of PV to produce power from an abundant renewable resource – the sun – means it will have a vital part to play in building a low-carbon future.