How Do Solar Panels Give Electricity To A House?

Solar panels, also known as photovoltaic (PV) panels, are devices that convert sunlight into electricity. They are made up of solar cells, which are semiconductor materials that can generate electricity when exposed to sunlight. The sunlight excites the electrons in the solar cells, causing them to flow and generate a DC electric current. This process is called the photovoltaic effect.

In a typical home PV system, solar panels are installed on the roof and connected together to form an array. The solar array is then connected to an inverter, which converts the DC electricity from the panels into AC electricity that can power home appliances and be fed back into the electrical grid. The number of solar panels needed depends on how much electricity the home uses.

Solar panels provide a renewable, sustainable way to generate electricity for homes and businesses. Once installed, they require very little maintenance and can significantly reduce or even eliminate conventional grid electricity usage.

PV Solar Cell Basics

Photovoltaic (PV) solar cells are semiconductor devices that convert sunlight directly into electricity. When sunlight hits the solar cell, photons from the light are absorbed by the semiconductor material, causing electrons to be dislodged from the atoms. This generates an electric current as the electrons flow through the material to the metal contacts on the solar cell. The photovoltaic effect causes this conversion of light to electricity.

PV cells are typically made of silicon with trace amounts of boron and phosphorus added. The addition of these elements creates an electric field across the cell, with boron giving the silicon a positive charge and phosphorus giving it a negative charge. When sunlight hits the solar cell, the electric field helps pull electrons freed by the photons in a particular direction, allowing them to flow through the cell and produce electricity.

The key components of a basic PV solar cell are the semiconductor layer, metal contacts, antireflective coating, and encapsulant. The semiconductor absorbs light and generates electricity. The metal contacts transfer the current. Antireflective coating reduces reflective loss. Encapsulant protects solar cell from environment.

Solar Panel Design

Solar panels consist of solar cells, which are made of semiconductor materials like silicon. The most common type of solar panels have 60 or 72 solar cells connected together and encapsulated within a glass and plastic casing to protect the cells.

The top surface of a solar panel is covered with tempered glass, usually 3mm thick for durability. Underneath are the solar cells aligned closely together. On the back is a plastic casing, typically made of polymers like tedlar or polyvinyl fluoride. The plastic backsheet protects the cells from the environment and insulates them.

Solar cells contain one or two layers of semiconducting material, usually silicon. When sunlight hits the cell, electrons are knocked loose from the silicon atoms. Metal conductive plates on the cell collect the electrons and channel them as electric current. The electrons flow into metal ribbons that combine the current from multiple cells into a panel.

Busbars run along the top and bottom of the cells, interconnecting them. They carry the current to the junction box on the back of the panel. From there, wires connect the solar panels together into an array. By connecting cells in this way, solar panels can generate higher voltages and power levels than a single cell could on its own.

The cells in a solar panel are encapsulated between the glass top and plastic backsheet using ethylene vinyl acetate, a transparent adhesive. The EVA seals and insulates the solar cells. Many manufacturers also add a tedlar or polymer film as the rear layer facing the sun, improving light transmission to the silicon cells.

Inverters

The direct current (DC) electricity generated by solar panels must be converted into alternating current (AC) electricity before it can be used to power home appliances and equipment. This is the job of inverters. Inverters play a critical role in solar energy systems by transforming the DC output into usable AC power.

Inverters connect to the DC electrical output from the solar panels and convert it into AC power at the correct voltage and frequency. This allows the solar-generated electricity to integrate seamlessly into a home’s electrical system and power AC devices. Most inverters also provide important safety features and monitoring capabilities.

There are two main types of inverters used in home solar systems: string inverters and microinverters. String inverters are typically more affordable and convert the combined output of multiple panels into AC power. Microinverters convert the DC output at each panel into AC and allow for more modular systems. Inverter technology has improved in efficiency, reliability and intelligence over the years.

Quality inverters that are properly sized are key to getting the most out of a home solar electric system. They ensure the DC electricity produced is effectively converted into useful AC power for running lighting, appliances and other electrical loads.

Wiring the System

Once the solar panels are installed, they need to be connected together and wired to integrate with the home’s electrical system. The solar panels will be wired in series to boost the voltage to the proper level for the inverter. The panels will use MC4 connectors that allow them to be plugged together in a daisy chain configuration. 12AWG copper wires are typically used to connect panels together due to their durability and ability to handle high amperages.

The wiring from the solar array will run through exterior electrical conduit on the roof and side of the house. It will enter an interior space where the inverter and other equipment will be located, like a garage or utility room. From the inverter, wiring will connect to a circuit breaker in the main electrical panel reserved for the solar system. This allows the solar electricity to run through the homes existing electrical wiring and provide power just like the utility grid would.

Properly sizing the wiring for expected solar output is important. Voltage drop can occur if small wires are used over long distances. The solar installer will determine the right wire gauge and conduit paths to integrate the system safely and efficiently.

Monitoring System Output

Once the solar panels are installed and connected to your home’s electrical system, you’ll want to monitor how much electricity the system is producing. There are a few main ways to do this:

Meters

Many solar installations will have a meter specifically for monitoring solar production. This is separate from your home’s main utility meter. The solar production meter tracks how many kilowatt-hours are being generated by the solar panels. Tracking this over time will show how much the system is offsetting from the utility grid.

Monitoring Software

Many solar inverters and optimizers come with monitoring software that tracks real-time solar production data. This software can be accessed on a computer or mobile device to see how the system is performing. Some things the software monitors includes:

• Current power production
• Daily, monthly and lifetime energy production
• Performance of individual solar panels
• Alerts for any system issues

The monitoring software provides detailed insights into system performance and ensures the solar panels are operating efficiently.

Factors Affecting Output

The amount of electricity generated by solar panels depends on several factors related to their placement and exposure to the sun. Optimizing these factors is key to maximizing solar production.

Orientation

Solar panels produce the most electricity when oriented to face true south. Facing even 20 degrees off south can reduce output by over 10%. Panels should be oriented towards the equator, so northern hemisphere installations face south and southern hemisphere systems face north.

Shading

Shading is very detrimental to solar production, as even a small amount of shading can drastically cut output. Solar arrays should be placed with no obstructions and full exposure to sunlight, especially during peak daylight hours. Nearby trees, chimneys, and buildings can potentially cause problematic shading.

Weather

Overcast and cloudy days significantly reduce the solar electricity generated. Seasonal weather patterns and locations prone to storms and overcast skies will produce less total solar energy. However, solar panels can still generate electricity even on cloudy days.

Angle of the Sun

The angle of the sun impacts the intensity of sunlight reaching the panels. When the sun is directly overhead, solar radiation is most intense. As the angle increases, radiation spreads over a larger area reducing intensity. In the northern hemisphere, solar production peaks in the summer as the days are longer and the sun higher in the sky.

Sizing a Solar System

When considering solar panels, it’s important to properly size the system to meet your home’s energy needs. The size of the solar system is primarily determined by calculating your average daily electricity usage and the amount of sun exposure at your location.

To determine how much electricity you use, review your last 12 months of utility bills and calculate your average daily kWh usage for each month. Identify the month with the highest electricity usage, as that will determine the minimum size solar system you need. Also account for any major energy uses you may add in the future, like an electric vehicle or heat pump.

Next, use a solar calculator to determine how many solar panels you need to produce that amount of electricity in your area. Input your average daily energy use, local electricity rates, your address, and average annual sun hours for your location. The calculator will recommend the number of solar panels and the size inverter you need.

Focus on getting the right panel capacity and inverter size to produce enough power daily even in the winter months. Oversizing can waste money while undersizing leaves your home short on power. Work with solar professionals to get proper solar sizing based on your energy use and sun exposure.

Batteries for Storage

Many homeowners with solar panels choose to install batteries to store electricity for use when the sun isn’t shining. There are two main battery options for solar energy systems:

Lead-acid batteries

These are the most common and time-tested battery type used for solar storage. Lead-acid batteries are relatively inexpensive, but they are large, heavy and have a shorter lifespan than some newer battery technologies.

Lithium-ion batteries

Li-ion batteries are lighter, smaller, have a longer lifespan and higher performance than lead-acid. However, they are more expensive. Popular brands for solar storage include Tesla Powerwall and LG Chem.

Batteries allow solar panel systems to operate off-grid, meaning completely independent from the utility grid. For grid-tied systems, batteries provide backup power when the grid goes down and allow solar energy to be stored for use at night. The batteries recharge from excess solar electricity during the day.

Homeowners should carefully weigh the pros and cons of adding solar batteries. While they provide energy independence and backup power, the added cost may not make sense depending on utility rates and incentives.

Costs and Savings

The cost of a solar PV system has dropped dramatically over the past decade, making it an affordable option for more homeowners. The average cost for a residential solar system in 2022 was around $18,000 before incentives, according to the Solar Energy Industries Association.

The main costs include the solar panels, inverters, racking equipment, wiring, and labor for installation. The system size, type of panels and inverters, and complexity of the installation will impact overall costs. Premier solar brands usually cost more but come with better warranties. Economies of scale also allow installers to offer discounts on multiple panel purchases.

Many homeowners finance solar systems through loans, power-purchase agreements, or leases rather than paying cash upfront. Federal and local incentives like the Solar Investment Tax Credit (ITC) and rebates can reduce out-of-pocket costs significantly. The ITC offers a 26% tax credit for systems installed in 2022-2023 and 22% after 2023. Some states also allow net metering, which provides bill credits for excess power sent back to the grid.

While solar requires an upfront investment, it can provide decades of free electricity from the sun once installed. The SEIA estimates a typical system in the U.S. pays for itself within 6-7 years when accounting for utility savings and incentives. After the payback period, homeowners benefit from another 13-20+ years of free power before panels may need replacing. With electricity rates constantly rising, going solar shields homeowners from future rate hikes.