How Solar Energy Works?

How solar energy works?

Solar energy is the energy from the sun that is converted into thermal or electrical energy. Solar energy, also known as photovoltaics (PV), has been utilized for thousands of years, but has seen tremendous growth recently as costs have declined and efficiency has improved. The solar PV market has grown at an average annual rate of over 40% since 2000 [1]. As of 2020, solar accounted for approximately 3% of total electricity generation worldwide, but that number is expected to grow to 20% by 2040 [2]. The growth of solar energy is driven by several key factors including policy support, decreasing costs, and increasing awareness of sustainability. Solar energy has enormous potential as an abundant, renewable source of power with minimal environmental impact.

How Solar Panels Work

Solar panels work through the photovoltaic effect, which is a process that generates voltage or electric current when sunlight hits the panels. Solar panels are made up of solar cells, which contain silicon atoms. When sunlight hits the solar cells, the photons from the sunlight knock electrons free from the silicon atoms. This causes the electrons to flow and generate an electric current. The solar cells are wired together to form a solar panel and allow the current to be collected and used as electricity.

Solar cells contain two layers of semiconducting material, usually silicon. One layer has an excess of electrons (n-type layer) while the other is deficient in electrons (p-type layer). When sunlight strikes the solar cell, the photons energize the electrons in the n-type layer. The electric field at the junction between the two layers causes the electrons to flow from the n-type side to the p-type side, generating an electric current. The greater the intensity of sunlight striking the panel, the greater the electric current produced.

Solar panels are modular, which means multiple panels can be wired together to produce more electricity. The panels are mounted on racks that allow them to track the movement of the sun across the sky, maximizing solar exposure and energy production throughout the day. The racks also elevate the panels to avoid shadows and enable air circulation to keep the panels cool.


Types of Solar Panels

There are two main types of solar panels: crystalline silicon and thin film. Crystalline silicon panels are the most common, making up over 90% of the solar panel market. Thin film panels are less efficient but cheaper to produce.

Crystalline silicon panels are made from silicon wafers. There are two types: monocrystalline and polycrystalline. Monocrystalline panels are made from a single cylindrical silicon crystal, giving them a distinct look with uniform black coloring. They typically have efficiencies around 15-20%. Polycrystalline panels are made from multiple silicon crystal fragments melted together, giving them a speckled blue appearance. They are slightly less efficient at around 13-16%.

Thin film panels use cadmium telluride (CdTe) or copper indium gallium selenide (CIGS) instead of silicon. They are only 1-2 microns thick versus 150-200 microns for crystalline silicon. This allows flexible thin film panels to be rolled or curved. However, thin film efficiencies are generally 6-12%, much lower than crystalline silicon.

In terms of efficiency, monocrystalline panels are the most efficient, followed by polycrystalline and then thin film. However, thin film panels can be a good option when space is limited due to their flexibility. Overall, crystalline silicon dominates the solar market due to higher efficiencies and proven reliability.

Solar Panel Installation

The solar panel installation process typically takes 1-2 days to complete depending on the size of the system (Solar Panel Installation Process, 2022). The key steps involve mounting, wiring, connecting the inverter, and connecting to the electric meter.

Solar panels are mounted on the roof or ground using racking systems secured with lag bolts. Wiring connects the solar panels to combiner boxes, which aggregate the power from multiple panels before sending it to the inverter. The inverter converts the solar DC power to usable AC power for the home. Finally, the system is connected to the utility meter to allow any excess solar power to flow back to the grid (The Solar Panel Installation Process, 2022).

A licensed electrician handles the complex wiring and electrical connections. Solar installers also obtain permits, configure equipment settings, and activate monitoring systems. Homeowners do not need to be present during the 1-2 days of active installation work.

Factors Affecting Solar Output

There are several key factors that affect how much energy solar panels are able to produce, including orientation, tilt angle, shading, weather, and climate.

Orientation refers to the direction solar panels face. For maximum production, solar panels should face true south in the northern hemisphere and true north in the southern hemisphere. Facing solar panels west will decrease electricity production in the morning while facing east will decrease output in the afternoon and evening. According to EnergySage, facing solar panels perfectly south generally yields around 10-15% more power than a western or eastern orientation.

Tilt angle also affects how much sunlight hits the solar panels. The optimal tilt angle equals your latitude. However, tilt angles between 30-45 degrees are suitable for most regions. Steeper tilt angles enhance winter performance while flatter tilt angles optimize summer production. Adjusting tilt angle throughout the year can increase solar panel output by around 5%, as noted by Intermountain Wind & Solar.

Shading can significantly reduce how much sunlight reaches solar panels, decreasing electricity generation. Even a small amount of shading can have an outsized impact. Solar panels should be located in an open area without obstructions from buildings, trees, or other objects. If shading exists, optimize placement to minimize its effects.

Weather and climate also influence solar panel productivity. More sunshine and fewer cloudy days increase solar output. Cooler climates see solar panel production decline in winter months while hotter climates experience decreased summertime output. Locations like the sunny southwest United States tend to be ideal for solar panels.

Sizing a Solar System

Properly sizing a solar system ensures it will meet your energy needs efficiently. The key factors in sizing a solar system are:

  • Calculating energy usage – Estimate your total daily and monthly electricity consumption based on utility bills and lifestyle.
  • Solar panel specs – Select solar panels based on output wattage, physical size, efficiency, warranty, etc.
  • Inverter specs – Choose an inverter capable of handling the total watts of your solar array.
  • Site factors – Consider available roof space, sun exposure, shading, local weather and latitude.

To calculate the system size you need, take your average daily energy use in kWh and divide it by the peak sun hours for your location. This gives you the kW size solar array you need. Then divide the kW by the wattage of the panels you plan to use to get the number of panels. Always oversize slightly to account for future energy increases and losses. Installers use detailed solar sizing tools and site visits to refine system sizing.

According to this source, “To figure out how to size your solar system, take your daily kWh energy requirement and divide it by your peak sun hours to get the kW output.” Proper sizing ensures your solar system will meet your unique energy needs.

Cost of Solar Panels

The cost of solar panels can vary greatly depending on the size of the system, type of panels, location, available incentives, and installation costs. However, a typical home system with premium solar panels now costs around $2.50 to $3.50 per watt on average for the solar equipment and installation in the U.S., according to Forbes.1 This means a typical 6 kW system would cost $15,000 to $21,000 before incentives.

The main costs for a solar PV system include:

  • Solar panels – This makes up around 30% of the total cost. Premium panels range from $0.55 to $0.70 per watt.
  • Inverters – Around 10% of the cost. Inverters convert the DC electricity from panels to AC for household use.
  • Rackings and wiring – Around 15% of cost for materials and labor.
  • Permits, inspection, interconnection fees – Around 5% of costs.
  • Installation labor – Around 25% of the cost is installation.

There are also various incentives, tax credits, rebates, and net metering savings that can offset around 25% to over 50% of the overall costs. The federal investment tax credit (ITC) offers a 26% tax credit for systems installed through 2022, which will decrease annually after. Many states and utilities also offer additional rebates and incentives that can save homeowners money.

Payback Period

The payback period refers to the amount of time it takes for the savings from solar panels to cover the upfront costs of installation. On average, the payback period for residential solar panels in the U.S. is between 6-10 years [1]. However, this can vary significantly based on factors like sunlight availability, electricity rates, incentives, and financing options.

Solar panels generate electricity from sunlight, reducing or even eliminating monthly electric bills. The more electricity the solar panels produce, the greater the savings. In sunny states like California and Arizona, payback periods tend to be shorter, often around 6-8 years [2]. In less sunny areas, payback periods might extend to 10-12 years.

Financing options can impact payback period as well. Solar loans allow homeowners to pay for a system over time while immediately benefiting from lower electric bills. This stretches out costs but leads to a faster payback compared to purchasing the system outright. Some homeowners choose to lease solar panels, which involves lower upfront costs but less long-term savings.

For most homeowners, solar panels represent a good long-term investment. Panels typically last 25-30 years, so they continue generating electricity and savings for many years after the payback period ends. Going solar insulates homeowners from rising utility rates, and may increase home value. With incentives and favorable financing, solar systems can yield exceptional returns on investment over the system lifetime.

Environmental Benefits

Solar energy provides significant environmental benefits compared to fossil fuel-based energy sources like coal, natural gas and oil (for example source). Unlike fossil fuels, the use of solar energy technologies and solar power plants produces zero air pollution or greenhouse gas emissions during operation. Widespread implementation of solar power would lead to notable reductions in greenhouse gas emissions and improved public health through better air quality.

According to the U.S. Department of Energy, generating electricity from solar energy rather than fossil fuels offers a climate-friendly way to meet growing energy needs while cutting emissions of greenhouse gases and other pollutants (source). Solar energy could play an integral role in reducing the impacts of climate change. Since solar panels generate electricity without emitting greenhouse gases, they can significantly lower a home, business, or utility’s carbon footprint.

Solar power represents a sustainable energy source given that sunlight is naturally replenished. Solar technologies require less water for electricity generation compared to many other sources. Solar power helps conserve finite natural resources and reduces dependence on fossil fuels. Based on current solar technology efficiency, the amount of sunlight striking the earth’s surface in one hour could meet the world’s energy demands for an entire year, underscoring the vast promise of solar power (source).

Future of Solar Energy

Solar energy is expected to continue growing in the future as technology improves and costs decline. According to research from the MIT Energy Initiative, solar photovoltaic systems could provide up to 69% of electricity generation by 2050 if new technologies raise their efficiency. Key areas of research for improving solar efficiency include developing solar cells from new materials like perovskites, stacking multiple solar cells together, and using nanotechnology.

Growth projections for solar vary, but most experts predict strong continued growth. The International Energy Agency (IEA) projects that solar PV capacity could grow from 760 gigawatts today to over 8,500 gigawatts by 2050 under their net zero scenario (IEA). This is over 10 times current capacity. In the United States, the Department of Energy Solar Futures Study found that solar energy could provide up to 40% of the country’s electricity by 2035 and 45% by 2050 with supportive policies.

New solar installations reached a record 207 gigawatts worldwide in 2021, and the IEA expects over 260 gigawatts to be added in 2022. As costs continue to fall due to technology improvements, economies of scale, and supportive policies, solar is becoming increasingly competitive with fossil fuels for power generation around the world. This ongoing cost decline will enable continued rapid growth in the coming decades.

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