What Is The Power Generation Done By Using A Series Of Photovoltaic Cells?

Photovoltaic (PV) cells, also known as solar cells, are devices that convert sunlight directly into electricity. PV cells work through the photovoltaic effect, where photons from sunlight knock electrons into a higher state of energy, creating electricity. The photovoltaic effect was first discovered in 1839 by French physicist Edmond Becquerel. The first functional solar cells made of selenium were built in the 1880s. Modern silicon solar cells, which are much more efficient, were developed starting in the 1950s.

PV cells are made up of one or more layers of semiconducting material, usually silicon. When sunlight hits the cell, photons transfer their energy to electrons in the semiconducting material. This frees the electrons to flow through the material and produce an electric current. The current generated can be used to power electrical loads directly, stored in a battery, or fed into the electric grid. PV cells do not need direct sunlight to work, they can still generate electricity on cloudy days. However, more sunlight means more electricity generation.

Types of PV Cells

There are three main types of photovoltaic cells used today: crystalline silicon, thin-film, and emerging technologies.

Crystalline Silicon

Crystalline silicon PV cells are the most common type, accounting for over 90% of the market. They are made from silicon ingots that are sliced into wafers and then processed into cells. Crystalline silicon comes in two main types:

• Mono-crystalline silicon – Made from single crystal ingots resulting in high efficiencies of 15-20%. However, they are more expensive to produce than multi-crystalline silicon.
• Multi-crystalline silicon – Made from cast square ingots that are sliced into wafers. They have slightly lower efficiencies of 13-16% but are cheaper to manufacture.

Thin-Film

Thin-film PV cells are made by depositing extremely thin layers of photosensitive materials onto substrates like glass, stainless steel or plastics. Thin-film modules have efficiencies typically ranging from 7-13%. Types of thin-film PV include:

• Amorphous silicon
• Cadmium telluride
• Copper indium gallium selenide

Emerging Technologies

Some emerging PV technologies that are still in early R&D or pilot stages include:

• Perovskites
• Organic PV
• Quantum dots
• Dye-sensitized solar cells

These new PV technologies aim to improve efficiency, lower costs, or provide more flexibility compared to traditional silicon cells. However, most are still far from commercial viability.

PV Cell Efficiency

The efficiency of a photovoltaic (PV) cell is a measure of how much of the sun’s energy striking the cell is converted into usable electricity. Typical efficiencies for commercially available PV cells range from 15% to 22%.

Several factors affect the efficiency of a PV cell:

• PV material – Different semiconductor materials have different conversion efficiencies, with more advanced materials like gallium arsenide being more efficient than silicon.
• Cell technology – The cell structure and manufacturing process impacts efficiency, with monocrystalline cells typically being more efficient than polycrystalline.
• Temperature – PV efficiency decreases as temperature increases. Cooler climates enable higher efficiencies.
• Solar spectrum – The spectrum of light energy affects cell efficiency, with certain materials performing better under different spectra.
• Sun orientation – The orientation and tilt angle of the PV panels impact the intensity of light reaching the cells.

Research continues on developing higher efficiency PV cells and improving manufacturing processes to increase commercial cell efficiencies.

PV Arrays and Systems

Photovoltaic cells are connected together to form larger units called modules, also known as solar panels. Modules consist of dozens of interconnected PV cells sealed together behind a glass sheet. The cells within a module are wired together to reach the desired output voltage and power rating.

Modules are then connected together to form PV arrays. The number of modules in an array depends on the desired power output. Modules in an array are connected in series and/or parallel to obtain the electrical characteristics required for the system. Series connections allow the voltages of the individual modules to add together, while parallel connections allow the current from each module to add together.

The DC electricity generated by PV arrays then needs to be converted into usable AC power for distribution. This is done using inverters, which convert the DC output into 240V AC electricity fed into the electrical grid or used to power a building directly. Additional components like chargers, transformers, and regulators may also be part of a PV system.

PV arrays can range from a few kW mounted on rooftops to massive MW-scale solar farms covering acres of land. Large utility-scale PV systems feed power directly into the grid whereas distributed rooftop systems provide energy for individual buildings and homes.

Applications of PV Power

Photovoltaic solar power has a wide variety of applications, from small residential systems to large utility-scale solar farms. Some of the main applications include:

Residential PV Systems

Rooftop solar panels on homes are one of the most common uses of PV systems. Typical residential systems range from 2-10 kilowatts and can provide a portion or all of a home’s electricity needs. Any unused solar power is fed back into the grid. Residential PV systems allow homeowners to reduce their reliance on the grid and lower their electricity bills.

Commercial PV Systems

Businesses, warehouses, offices and other commercial buildings also commonly install rooftop solar systems. These are usually larger systems, often 10-100 kilowatts or more. The solar power generated is used to supplement a building’s electricity needs during business hours. Commercial PV systems provide both environmental and economic benefits.

Utility-Scale PV Systems

Large ground-mounted PV systems can range from hundreds of kilowatts up to hundreds of megawatts. Also known as solar farms or power plants, these systems feed solar electricity directly into the utility grid on a large scale. Many solar farms now rival traditional power plants in size. As solar panel costs have fallen, utility-scale systems have become an increasingly cost-effective way to generate renewable electricity.

Growth of PV Power

The global installed capacity of photovoltaic (PV) power has seen rapid growth over the past two decades. From 2000 to 2012, global PV capacity increased at an average annual rate of over 40%. In 2016, new PV installations reached over 75 gigawatts worldwide. Total global PV capacity now exceeds 300 gigawatts as of 2018.

China, Japan and the United States have led PV capacity growth and are the top three countries for total installed PV capacity. In 2016, China had over 77 gigawatts of total installed PV capacity, accounting for almost half of the global market share. Japan ranked second with over 42 gigawatts, while the U.S. had 40 gigawatts of operational PV capacity. Other leading countries for PV installations include Germany, Italy and India.

The growth of PV power generation is expected to accelerate in the coming decades. According to the International Energy Agency (IEA), global PV capacity could reach over 4500 gigawatts by 2050 under their accelerated case scenario. Falling costs and favorable policies are key drivers enabling increased adoption of solar PV systems around the world.

Cost of PV Power

The cost of photovoltaic solar power systems has declined steadily over the past few decades. In the early 2000s, a typical residential PV system cost around $10 per watt. By 2019, costs had dropped to around $2.70 per watt. Inverter prices have also fallen from around 50 cents per watt in 2005 to 20 cents per watt in 2014.

Several factors have driven down PV system prices over time:

• Improved manufacturing processes and scale – Larger factories and automated production has reduced manufacturing costs per module.
• Declining polysilicon prices – Polysilicon is the raw material for silicon PV cells and prices have dropped 90% since 2008 as production processes improved.
• Increased module efficiency – More efficient solar cells mean less area is needed for the same power output, reducing balance of system costs.
• Reduced soft costs – Installation labor, permitting, financing and supply chain costs have decreased.
• Economies of scale – Larger deployment leads to lower prices across the value chain.

The levelized cost of energy (LCOE) from solar PV is now competitive with conventional power generation technologies in many regions. However, installed prices can vary significantly depending on system size, location, equipment, installation labor and soft costs.

Environmental Impact of Photovoltaic Power

The environmental impact of photovoltaic solar power has both advantages and disadvantages compared to other forms of electricity generation. On the positive side, solar PV generates electricity without emitting greenhouse gases or toxic pollutants. Solar cells also have low lifecycle emissions associated with raw material extraction, manufacturing, and recycling. However, there are some concerns around the use of toxic materials in solar panel production and challenges around recycling old solar panels.

One of the biggest advantages of solar PV is that it generates electricity without emitting carbon dioxide or other greenhouse gases during operation. This makes it a clean renewable energy source that can help mitigate climate change. Solar PV emits only about 0.07 pounds of carbon dioxide equivalent per kilowatt hour, which is over 90% less than natural gas and coal power plants. As solar expands its share of electricity generation, it can displace fossil fuel power and significantly reduce overall carbon emissions from the energy sector.

Solar PV also avoids many of the air and water pollutants emitted from fossil fuel power plants, such as sulfur dioxide, nitrous oxides, particulates, and mercury. This provides environmental and public health benefits, especially in areas where solar replaces dirty coal plants. Solar power generates electricity without any noise or fuel transport pollution.

However, the PV cell manufacturing process does use some hazardous materials, including hydrochloric acid, sulfuric acid, nitric acid, hydrogen fluoride, and solvents. There are also small amounts of toxic heavy metals like cadmium and lead in solar panels. This has raised concerns about potential leakage and contamination, especially if old solar panels are improperly disposed of. Very little recycling currently occurs, though new recycling processes are being developed.

Overall, the lifecycle emissions and impacts of solar PV are quite low, especially compared to fossil fuels. But the solar industry must continue innovating to reduce toxicity and enhance recycling. If these challenges can be met, solar photovoltaics can provide very clean and sustainable electricity over the coming decades.

Challenges for PV Power

While solar PV power has seen tremendous growth, there are still some key challenges that need to be addressed for it to reach its full potential.

Intermittency

One major challenge with solar PV is intermittency. Solar panels only produce power when the sun is shining. This means that solar PV output can fluctuate throughout the day and is sensitive to weather and seasonal changes. Areas with less sunshine will generate less solar power. Battery storage solutions can help mitigate intermittency, but add additional costs.

Transmission Infrastructure

Many prime solar resources are located far from population centers that need the power. New transmission lines are needed to connect solar farms to the grid. Upgrading transmission infrastructure is expensive and faces siting and permitting challenges.

Storage Solutions

To provide power when the sun isn’t shining, large scale energy storage solutions are needed. Battery technology is improving, but costs are still high. Other solutions like pumped hydro require specific terrain. More R&D is needed to improve energy storage options for solar PV.

Low capacity factors, the need for storage, and transmission challenges make solar PV more expensive compared to always-on power sources. But with continued innovation and scalining, costs are expected to come down further.

Future of PV Power

As solar photovoltaic technology continues to improve and costs keep declining, the future looks bright for PV power generation around the world. Here are some key things to watch for in the coming years:

Projections: Most analysts project strong continued growth for solar PV, with some estimates showing the total global installed capacity doubling within the next 5 years. Many countries have set ambitious solar targets as part of their clean energy goals. If these targets are met and costs continue to fall, solar PV could potentially meet over 20% of global electricity demand by 2030.

Emerging technologies: Researchers are working to improve solar cell efficiency and flexibility. Some emerging PV technologies to watch include perovskite solar cells, organic PV, multi-junction cells, and solar paints/coatings. If commercialized, these technologies could enable solar applications on more surfaces and further reduce costs.

Role in clean energy: As solar PV scales up and integrates well with battery storage, it is positioned to play a major role in clean energy transitions around the world. PV offers a clean, renewable way to help meet electricity demand without carbon emissions. Combining solar PV with other renewables can enable high penetrations of clean energy on grids.

With its falling costs, low environmental impact, and versatility, solar PV seems poised to enjoy strong global growth for decades to come. Ongoing R&D and policy support for solar will help maximize its future role in clean energy systems worldwide.