How To Convert Solar Energy Into Electricity?

Solar energy is the radiant energy emitted from the sun. It is a renewable energy source that can be harnessed in various ways, including through solar panels that convert sunlight into electricity.^[1] With concerns about climate change and fossil fuel dependence, solar power has become an increasingly important source of clean energy. Today, solar accounts for nearly 3% of total U.S. electricity generation.^[2]

Generating electricity from solar energy involves converting the photons in sunlight into an electric current. This is generally done using photovoltaic solar panels, which consist of solar cells made from materials that exhibit the photovoltaic effect. When sunlight hits these cells, the absorbed photons knock electrons loose, allowing electron flow and generating direct current electricity. This electricity must then be converted into alternating current and fed into the electrical grid for everyday use.

This article provides an overview of how photovoltaic solar panels convert solar energy into usable electricity, from solar cell technologies to system components and connections.

Solar Cell Basics

Solar cells convert sunlight into electricity using the photovoltaic effect. When sunlight hits the solar cell, the energy from the photons in the sunlight is transferred to the semiconductor material in the cell (1). This excites the electrons in the semiconductor and causes them to flow in one direction, producing an electric current.

Solar cells are made of semiconductor materials like silicon that have been treated to form a p-n junction. The p-n junction separates the positive (p) and negative (n) charged regions of the semiconductor, setting up an electric field. When a photon hits the cell, its energy frees an electron in the p-type layer to move into the n-type layer, creating a voltage difference and current (2). The voltage difference causes the electrons to flow in one direction, from the n-type side to the p-type side, generating electricity.

The performance of a solar cell depends on its ability to absorb sunlight and convert it efficiently into current. Semiconductors with proper band gaps, crystal structure, and electrical properties are best suited for absorbing photons and generating electricity.

Types of Solar Cells

There are several different types of solar cells that convert sunlight into electricity. The main types include:

Monocrystalline Silicon Solar Cells

Monocrystalline silicon solar cells are made from very pure silicon crystals that have a uniform shape and size. These solar cells tend to have the highest efficiency rates, usually around 15-20%, but are more expensive to produce than other types (https://www.energy.gov/eere/solar/solar-photovoltaic-cell-basics). Monocrystalline panels have a distinct black color.

Polycrystalline Silicon Solar Cells

Polycrystalline silicon solar cells are made from melted silicon that is poured into molds to form square wafers. The crystallized silicon has a more random structure, which reduces efficiency to around 13-16%. But polycrystalline cells are easier and less expensive to manufacture than monocrystalline cells (https://www.renewableenergyhub.co.uk/main/solar-panels/types-of-solar-cell). Polycrystalline panels have a speckled blue color.

Thin Film Solar Cells

Thin film solar cells are made by depositing one or more thin layers of photovoltaic material onto a substrate like glass or plastic. Common thin film materials are cadmium telluride (CdTe), copper indium gallium selenide (CIGS), and amorphous silicon (a-Si). Thin film solar cells have lower efficiency of 7-13% but their flexibility makes them useful for many applications (https://www.homeowner.com/solar/solar-cells-guide).

Solar Panel Components

Solar panels consist of a few key components that allow them to absorb sunlight and convert it into electricity. The main components are:

Solar cells – These are made from semiconductor materials like silicon that are treated to form an electric field. When sunlight hits the solar cells, it knocks electrons free, allowing them to flow and produce electricity. Solar cells are wired together and encapsulated between the glass, plastic, and backing.

Sources:

What Are Solar Panels Made Of and How Are They Made? | EnergySage

Glass casing – The solar cells are protected from weather and impact by a clear tempered glass cover. This allows sunlight to pass through to the solar cells underneath.

Aluminum frame – The strong aluminum frame provides structural support and rigidity to the solar panel. It also allows for easy mounting and installation.

Junction box – The junction box on the back of the solar panel contains connectors that allow the solar cells to be linked together and output electricity. Wires then connect the junction box to the rest of the system.

By connecting together the right combination of these components, solar panel manufacturers can produce efficient and durable units optimized for absorbing sunlight and generating renewable power.

Connecting Solar Panels

Solar panels are connected together into an array to produce more power. The solar cells in a panel are connected in series to increase the voltage, while the panels themselves are connected in parallel to increase the current. This allows the system to produce more wattage and power larger loads.

To connect multiple solar panels together, you use solar panel wiring to link the positive and negative terminals of each panel. The positive terminal on one panel is connected to the negative terminal on the adjoining panel using copper wire rated for solar use. This daisy chains the panels together into a series circuit.

Parallel connections are then made between the positive and negative ends of each string of panels to combine the currents. Bypass diodes are also wired across each panel to prevent damage from shading.

Proper solar panel wiring requires following electrical codes and safety standards. The system wiring diagram specifies the layout and connections needed based on the panels, inverter, batteries, and other components used. Understanding solar panel wiring basics helps ensure the array functions properly. [1]

Inverters

An inverter is a critical component of a solar energy system. Its job is to convert the direct current (DC) electricity generated by the solar panels into alternating current (AC) electricity that can be used to power home appliances and fed back into the electrical grid.

Inverters accomplish this DC-to-AC conversion using power electronics to rapidly switch the DC input back and forth. The resulting output has the alternating waveform of AC electricity with the standard voltage and frequency. According to the U.S. Department of Energy, “Fundamentally, an inverter accomplishes the DC-to-AC conversion by switching the direction of a DC input back and forth very rapidly” [1].

Most inverters used in grid-tied solar systems are able to synchronize with the frequency and voltage of the utility grid. This allows seamless transferring of solar power to the grid when not being used onsite. The inverter monitors the AC waveform from the grid and outputs a voltage to match it. This synchronization is a key inverter function that allows solar panels to feed usable AC electricity back into the grid.

Mounting and Tracking Solar Panels

Mounting solar panels is an important consideration when installing a solar system. Panels can be mounted on rooftops or on the ground, and each option has pros and cons.

Rooftop mounting is common for residential solar installations. Panels are usually mounted parallel to the roof using mounting rails attached with roof anchors. This can be done with or without roof penetrations. Key factors for rooftop mounting include roof type, age, orientation, shading, and local building codes [1].

Ground-mount systems are often used for larger solar arrays and allow for more flexibility in orientation and tilt angle. However, ground-mounting requires adequate unshaded land and is usually more expensive due to the racking materials and foundation requirements. Zoning laws may also restrict ground-mounted solar [2].

Tracking systems orient panels to follow the sun throughout the day, maximizing energy production. Single-axis trackers tilt panels along one axis, while dual-axis trackers tilt along two axes. Trackers can increase energy yield up to 30%, but have higher costs and maintenance requirements [3]. They are more common for large commercial and utility-scale systems.

Batteries and Storage

Batteries are one of the most common and effective ways to store solar energy for use when solar panels are not actively generating electricity. This allows solar power to be used around the clock, even when the sun is not shining. Battery banks store the electricity generated by solar panels during the daytime so that it can be used at night or on cloudy days. The most popular batteries for solar storage are lead-acid and lithium-ion batteries https://aurorasolar.com/blog/storing-solar-energy-everything-you-need-to-know/.

Battery banks are comprised of multiple batteries wired together to increase the storage capacity. The batteries are charged by the solar panels when the sun is shining. Then when solar generation decreases, the stored energy in the batteries is used. Sophisticated charge controllers regulate the charging and discharging processes to protect battery life. Battery banks provide solar systems with several hours worth of stored power, ensuring electricity is available overnight or during inclement weather.

Properly sized battery banks allow solar panel systems to operate off-grid, independent from utility connections. On-grid solar systems also utilize batteries to offset peak energy usage times and provide backup power. Lithium-ion batteries in particular have become more affordable in recent years, making solar energy storage more accessible. With energy storage, solar power can truly provide 24/7 renewable energy.

Maintenance

Regular maintenance is crucial to ensure solar panels operate efficiently and safely for their lifespan of 25-30 years. The most important maintenance task is cleaning the panels to remove any dirt, dust, bird droppings, leaves, snow etc. According to the Solar Panel Maintenance Guide by CNET, solar companies recommend cleaning panels at least twice per year. Use plain water and a soft cloth or brush to gently wipe the panels. Avoid abrasive cleaners or brushes that could scratch the glass. Hire a solar professional for difficult to reach rooftop panels.

It’s also crucial to routinely check electrical connections and wiring for any damage or loose connections according to Solar Reviews. Inspect the inverter, batteries, and mounting equipment for signs of wear or issues. Check that mounting equipment is securely fastened.

Monitoring system performance is key to identifying issues early. Look at energy production data over time to spot underperforming panels. According to CI Services, call a solar technician if production drops more than 15% from usual levels. They can troubleshoot and identify any maintenance needs.

Future Prospects

The future of solar energy is extremely promising. Research from MIT shows that solar energy has great potential in the future as technologies improve The Future of Solar Energy – MIT Energy Initiative. Solar costs have dropped dramatically in the past decade, with solar panel prices declining 89% since 2009 according to the Solar Energy Industries Association. Experts predict solar will continue getting more efficient and less expensive.

Advancements in solar cell technology are leading to more efficient conversion of sunlight into electricity. Emerging techniques like perovskite solar cells and organic photovoltaics can absorb more sunlight due to enhanced light-harvesting properties. Conventional silicon solar panels are also improving, with typical efficiencies rising from 15% to over 20% in the past 10 years.

With increased efficiency and lowered costs, solar energy generation is forecasted to expand substantially. The National Renewable Energy Lab estimates solar could supply up to 14% of U.S. electricity demand by 2050, up from only 3% today. As solar electricity costs fall below competing sources like coal and natural gas, adoption rates are expected to surge globally. With roughly 100,000 MW of solar capacity installed worldwide by the end of 2021, we’ve only just begun to tap solar’s immense potential.