What Are Called Solar Panels?

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What Are Solar Panels?

Solar panels, also known as photovoltaic (PV) panels, are devices that convert sunlight into electricity. They are made up of solar cells, which are assembled together into modules or panels. The solar cells contain a photovoltaic material, commonly silicon, that absorbs photons from sunlight and generates direct current (DC) electricity (Wikipedia, 2023).

When sunlight hits the solar panel, photons are absorbed by the solar cells. This causes electrons to be freed from the atoms in the photovoltaic material, creating electron-hole pairs. The electrons then flow from the solar cell into an external circuit, generating electricity. The DC current generated can then be fed into an inverter to convert it into alternating current (AC), which is the type of electricity used in homes and businesses (Britannica, 2024).

Solar panels provide a clean, renewable way of generating electricity from sunlight. They have no moving parts, require little maintenance, and have a long lifespan. Solar power systems with panels can be installed on rooftops or ground-mounted to provide electricity locally, or utility-scale solar farms can generate electricity to feed into the grid.

History of Solar Pannels

The first functional solar cell was inventede
in 1883 by Charles Fritts, who coated semiconductor selenium with an extremely thin layer of gold to form the junctions. However, this early solar cell was only about 1% efficient in converting sunlight into electricity.

The modern era of solar power technology arrived in 1954 when researchers at Bell Laboratories accidently discovered that silicon could produce a steady current of electricity when exposed to sunlight. This led to the production of the first practical photovoltaic cell, with a sunlight conversion efficiency of around 6%.

Over time, research led to improvements in manufacturing and efficiency. In the 1970s, Exxon and ARCO invested in solar technology and helped drive down costs. In 1977, the photovoltaic market began to expand with small-scale applications like powering watches and calculators.

In the 1980s and 1990s, photovoltaics gained recognition as a power source for remote locations without access to an electric grid. In 2000, Germany introduced a feed-in tariff policy to incentivize renewable energy generation at residential and commercial sites. This helped grow the global solar PV market significantly.

Today, continued improvements in solar cell efficiency along with large-scale manufacturing have helped drive down costs. Solar panels are now a mainstream technology around the world for both small-scale distributed generation and large utility-scale solar farms.

Types of Solar Panels

There are three main types of solar panels: monocrystalline, polycrystalline, and thin film. Each has its own advantages and disadvantages.

Monocrystalline solar panels are made from a single crystal of silicon and tend to be the most efficient, with average efficiencies around 15-20% (1). They have a distinct black color and uniform look. The high silicon purity makes them better at converting sunlight into electricity. However, monocrystalline panels tend to be more expensive than other types.

Polycrystalline solar panels are made from fragments of silicon crystals melted together. They have a speckled blue color and lower silicon purity, which results in slightly lower efficiency around 13-16% (2). The manufacturing process is simpler and cheaper, making polycrystalline panels less expensive than monocrystalline overall.

Thin film solar panels use ultra-thin layers of photovoltaic material on glass or stainless steel. They have the lowest efficiency, around 7-13%, but can be easier to install and are potentially flexible (3). Thin film is significantly less expensive but requires more physical space to capture the same energy as monocrystalline or polycrystalline panels.

(1) https://www.energysage.com/solar/types-of-solar-panels/

(2) https://www.thisoldhouse.com/solar-alternative-energy/reviews/types-of-solar-panels

(3) https://aurorasolar.com/blog/solar-panel-types-guide/

How Solar Panels Work

Solar panels generate electricity through the photovoltaic effect. When photons from sunlight hit the solar cell, they transmit their energy to the electrons in the atoms of the semiconductor material, knocking some of the electrons free. When electrons are knocked free, they are able to flow through the material to produce an electric current.

Specifically, solar panels are made of photovoltaic cells, which each contain two layers of a semi-conducting material, typically silicon. On the top layer, each photon knocks an electron free, creating a hole where the electron used to be. Since holes have positive charge and free electrons have negative charge, an electric field forms across the layers. Conducting plates on the sides of the cell collect the electrons from the bottom layer and transfer them to wires to produce electricity (1).

Solar cells are wired together to form solar photovoltaic modules, or solar panels. The more light (photons) that hit the cells, the more electricity that is produced. Solar panels tilt toward the sun to maximize the number of photons that strike the cells. Tracking systems can further maximize solar exposure over the course of a day. The photovoltaic process requires no moving parts and solar panels can produce electricity for decades with little maintenance or intervention after initial installation (2).

(1) https://www.iop.org/explore-physics/physics-around-you/sustainable-building/solar-panels

(2) https://pickmysolar.com/how-solar-panels-work/

Solar Panel Efficiency

Solar panel efficiency refers to the percentage of sunlight that hits the solar panel and gets converted into electricity. Most solar panels on the residential market today have efficiencies between 15-22% (1). However, some more advanced panels can reach up to 25% efficiency or more (2). Some key factors affect solar panel efficiency:

Type of solar panel – Panels made with monocrystalline silicon tend to be the most efficient, followed by polycrystalline silicon and then thin-film panels (3). Monocrystalline panels can reach 25% efficiency, polycrystalline 17-20%, and thin-film around 15%.

Temperature – Solar panels become less efficient as temperatures increase. In very hot weather, efficiency can drop 10-25% depending on the panel (1). Proper airflow and cooling is important for maintaining efficiency.

Shading – Even small shaded spots on a solar panel can disproportionately reduce output since the cells are connected in series. Full sun exposure is ideal for maximum efficiency.

Age – Solar panel efficiency degrades slowly over time, typically 0.5-1% per year (4). Proper maintenance can help minimize degradation. Most panels maintain around 80% of original efficiency after 25-years.

Researchers are continually improving solar cell materials and designs to increase efficiency. Real world systems rarely operate at max efficiency due to variable conditions. Proper solar panel selection, siting, and maintenance are key to optimizing efficiency.

Sources:

(1) https://www.energy.gov/eere/solar/solar-performance-and-efficiency

(2) https://corporate.enelx.com/en/question-and-answers/are-solar-panels-energy-efficient

(3) https://css.umich.edu/publications/factsheets/energy/photovoltaic-energy-factsheet

(4) https://www.aurorasolar.com/blog/solar-panel-degradation/

Cost of Solar Panels

Typical prices to purchase and install solar panels range from $10,000 to $30,000 for a home system, with most homeowners paying around $18,000 for an average-sized installation of 6 kilowatts (Source). However, costs vary considerably based on factors like your location, system size, and the type of solar panels installed.

Solar panels are priced according to how many watts they can generate, with costs typically between $2.50 and $4 per watt according to industry estimates (Source). So a 6 kW system at $3 per watt would cost around $18,000 before incentives. The watt price of solar has fallen dramatically over the past decade, making solar power much more affordable for homeowners.

The total installed cost is affected by your roof type, electric bills, electricity rates in your area, and applicable rebates and tax credits. Local installation costs also impact overall pricing. While solar panel equipment is fairly standardized, labor and permitting costs can vary across different markets.

Sizing a Solar Panel System

Determining the number of solar panels needed for a home or business requires calculating the energy needs and available sunlight. The general steps are:

First, calculate the average monthly electricity usage in kilowatt-hours (kWh) based on utility bills. This provides the energy needs.

Next, determine the solar potential of the location. The peak sunlight hours per day depends on factors like latitude and typical weather patterns. This source provides peak sun hour maps for reference.

Then, divide the average daily kWh usage by the peak daily sun hours. This gives the kilowatt capacity needed from the solar array. For example, if the average usage is 30 kWh per day and there are 4 peak sun hours, 30/4 = 7.5 kW system size needed.

Finally, determine how many solar panels will provide that capacity. Panel wattages typically range from 250-400 watts. With 300W panels, a 7.5 kW system would need around 25 panels (7,500W / 300W per panel = 25 panels).

When sizing a system, it’s best to overestimate needs rather than underestimate. Sizing up front for future energy increases or electric vehicle charging helps ensure the system meets long-term needs.

Installation and Maintenance

Installing solar panels requires careful planning and execution. The solar panels need to be mounted securely, wired properly, and integrated with the existing electrical system (Homeowner’s Guide to Going Solar). There are several mounting options:

Roof mounting – Panels are attached to the roof using racking systems. This is the most common residential installation method.
Ground mounting – Panels are mounted on frames anchored in the ground. This requires sufficient yard space.

Pole mounting – Panels are attached to poles fixed into the ground or concrete. This raises panels above obstructions.

Proper maintenance is crucial for solar panels to operate efficiently for their 25+ year lifespan (How to Install Solar Panels). Maintenance tasks include:

Inspecting panels and connections for damage

Cleaning panels regularly to remove dirt and debris
Checking inverter and wiring connections
Trimming vegetation blocking sunlight

Monitoring production to catch underperformance

With proper installation and maintenance, solar panels can provide clean, renewable energy for decades.

Net Metering and Feeding the Grid

Net metering is a billing mechanism that credits solar energy system owners for the electricity they add to the grid. For example, if a residential customer has a solar panel system on their roof, it may generate more electricity than the home is using during the day. The excess electricity is fed back into the local utility grid. The home’s electric meter runs backwards to provide the customer a credit for that excess electricity. This helps offset electricity drawn from the grid at night or other times when the solar system isn’t producing energy. Thus, the customer only pays for their “net” energy usage (Rosenstein).

One of the main benefits of feeding excess electricity back into the grid is that it reduces the amount of electricity that needs to be generated from fossil fuel power plants. Solar power fed into the grid displaces those sources and reduces carbon emissions and other pollution. Utilities also benefit from reduced peak demand on hot, sunny days when solar is producing a lot of energy. Overall, net metering provides a simple, intuitive way for customers with solar panels to be compensated for excess generation that benefits the grid (UCSUSA).

Sources:

Rosenstein, Jenny. “Solar Net Metering Explained (2024).” MarketWatch, 28 Dec. 2022, www.marketwatch.com/guides/solar/solar-net-metering/. Accessed 15 Feb. 2023.

UCSUSA. “Net Metering: What You Need To Know.” Union of Concerned Scientists, 23 Mar. 2023, www.ucsusa.org/resources/net-metering. Accessed 15 Feb. 2023.

Environmental Benefits

Solar energy has significant environmental benefits compared to fossil fuels. By generating electricity from the sun rather than coal, natural gas, or other fossil fuels, solar energy reduces air and water pollution that harms public health (Source). Fossil fuel power plants emit air pollutants such as sulfur dioxide, nitrogen oxides, particulate matter, and heavy metals that have been linked to acid rain, smog, respiratory illness, and cardiovascular disease. Burning fossil fuels also emits carbon dioxide, the primary greenhouse gas driving climate change.

Solar panels produce electricity without any air or water emissions. According to the U.S. Energy Information Administration, the average U.S. household solar PV system can reduce greenhouse gas emissions by over 4 tons per year (Source). Widespread adoption of solar energy and other renewables is critical for reducing greenhouse gas emissions from the electricity sector in order to mitigate climate change risks. With solar technology steadily improving and costs declining, solar energy has the potential to play a major role in creating a clean energy economy.