What Are Solar Panels Made Of Wikipedia?

Table of Contents

Introduction

Solar panels are devices that convert sunlight into electricity using photovoltaic (PV) cells made of semi-conducting materials. By capturing photons from the sun and converting them into an electric current, solar panels provide a renewable and clean source of energy. In this article, we will examine the different components that make up a typical solar panel and the materials used in their construction.

Photovoltaic Cells

A photovoltaic cell, or solar cell, is the basic component of a solar panel that converts sunlight into electricity. The photovoltaic effect causes the solar cell to absorb photons from sunlight and generate an electric current. Solar cells are made from semiconductor materials such as silicon, gallium arsenide, and cadmium telluride. When sunlight hits the cell, electrons are knocked loose from the atoms in the semiconductor material, allowing them to flow through the material and produce electricity. The photovoltaic cell has one or two layers of a negatively charged semiconductor material and a positively charged semiconductor material to create an electric field. When sunlight hits the cell, electrons are freed and flow from the negative layer to the positive layer, producing a DC current (Energy.gov, 2022).

Silicon is the most common material used in solar cells, representing approximately 95% of the photovoltaic market. It is an abundant, non-toxic semiconductor well-suited for capturing and converting sunlight into electricity. Gallium arsenide and cadmium telluride are also used for specialized solar cells (Wikipedia, 2023). The role of the photovoltaic cell in a solar panel is to absorb photons from sunlight and convert that light energy into electricity through the photovoltaic effect.

Glass Covering

The glass covering serves as a protective shield for the solar cells underneath. It helps protect the cells from impact damage and environmental wear. The most common types of glass used in solar panels are tempered glass and low iron glass.

Tempered glass is treated with heat or chemicals to increase its strength. This makes it more durable and resistant to breakage. Tempered glass is often used on the front of solar panels because it can withstand hail and physical impact.

Low iron glass has optimized solar transmission since it contains less iron impurities than regular glass. The iron content in normal glass can absorb and reflect some of the incoming sunlight. Using low iron glass allows more sunlight to pass through to the solar cells. This boosts the panel’s efficiency and power output.

Some solar panel manufacturers are also using anti-reflective coatings on the glass to increase light transmission. Other specialty glass includes textured glass to reduce glare, and transparent photovoltaic glass that can directly generate electricity from the sun.

Sources:
https://www.technicalwindowfilms.co.uk/solar-power-film-turning-windows-into-solar-panels/
https://www.onyxsolar.com/

Frame

The frame of a solar panel provides structure, rigidity, and protection for the solar cells and other internal components. Most solar panel frames are made from aluminum, though other metals or plastics may also be used. Anodized aluminum is a popular choice as it is lightweight, strong, durable, and resists corrosion (See: https://aluminumsolarframe.com/what-material-is-used-in-frame-of-solar-panel/).

The frame surrounds the exterior of the solar panel, holding together the glass, backsheet, junction box, and internal components. It provides mounting points to install the panels on racks or rooftops. The frame design also allows for connecting multiple panels together into an array. Additionally, the frame protects the inner workings of the solar panel from weather, impacts, and other environmental factors.

Junction Box

The junction box is an enclosure on the back of the solar panel where the wiring from the individual solar cells gets connected and routed out of the panel. Junction boxes are usually made of plastic or metal to protect the electrical connections from weather and other environmental factors.

The main purpose of the junction box is to combine the current from the individual solar cells into a single output cable. Inside the junction box, the thin wires coming from each cell or group of cells are electrically connected and attached to thicker output cables. These output cables are fed through a port on the junction box and have MC4 connectors or other attachments to connect multiple panels together.

By combining all the wiring into one output, the junction box allows the full power output of the solar panel to be carried through a single cable safely. It also provides a protective housing for those electrical connections (Source: https://sinovoltaics.com/learning-center/materials/pv-junction-box-purpose-and-connection/). The junction box is an essential component of every solar panel.

Wiring

The wiring connects the individual solar cells within a PV module and transports the electricity generated. The wiring is often made of copper and coated with a weatherproof insulating material like polyethylene or ethylene vinyl acetate (EVA). Thin wires, called tabbing ribbons, connect adjacent solar cells in series or parallel configurations to produce the desired voltage and current output for the module. Slightly thicker wires then aggregate the output of each string of cells and transport it to the junction box on the back of the panel.

Proper wiring design is important to minimize electrical resistance losses and prevent shading effects. Overheating due to inadequate wiring can damage panels over time. The wiring layout must balance optimizing sunshine exposure for each cell with routing accessibility to aggregate strings of cells. Advanced solar panels integrate intelligent electronics to optimize wiring configurations for changing conditions. High quality junction boxes, connectors, and outlet cables ensure safe, reliable transmission of the direct current output.

Source: https://www.e-education.psu.edu/ae868/node/875

Backsheet

The backsheet is a protective layer on the back of the solar panel that protects the panel components from outdoor weather conditions. It is commonly made from materials like tedlar and polyvinyl fluoride (PVF). The backsheet helps protect the panel from UV radiation, moisture, and high temperatures.

Tedlar is a brand name for polyvinyl fluoride (PVF) film created by DuPont. It is well known for its durability and weather resistant properties. Tedlar backsheets have been a popular choice for solar panels and can last up to 25 years.[1]

The backsheet is an important component because without proper protection on the back, moisture and UV light could penetrate the panel and degrade components like the encapsulant and solar cells over time. The multi-layer construction of the backsheet creates a weatherproof barrier to protect the inside of the panel for decades of outdoor exposure.

Encapsulant

The encapsulant is a key component in solar panels that serves to protect and adhere the solar cells and wiring. It is commonly made from ethylene-vinyl acetate (EVA), with other materials like polyolefin elastomer (POE) also being used. The main purposes of the encapsulant are:

To provide adhesion between the solar cells, wiring, top glass surface and rear backsheet of the module.
To act as an electrical insulator between the solar cells.
To protect the solar cells and wiring from moisture, UV rays, and corrosion over the 25+ year lifetime of a solar panel.

Quality encapsulant materials like EVA from manufacturers such as 3M are engineered to be long-lasting and stable when exposed to decades of UV rays and heat. They help ensure the solar cells can continue generating electricity safely and efficiently over the full lifetime of the solar panel.

Adhesives

Adhesives play a critical role in the construction of solar panels by laminating layers together and providing durability against environmental factors. Common adhesives used include silicones, polyurethanes, and acrylics.^[1] Silicone adhesives like Dow Corning’s PV6100 series provide strong adhesion, flexibility and weather resistance. Polyurethane adhesives such as Epic Resins’ S7459 offer superior adhesion and impact resistance. Acrylic adhesives like Henkel’s Loctite AA 3972 exhibit strong shear strength and UV stability.

These adhesives must maintain performance through temperature fluctuations, humidity, and UV exposure. They enable lamination of layers like the encapsulant, backsheet, and junction box to the panel frame.^[2] Choosing the optimal adhesive chemistry improves panel efficiency and lifetime in outdoor conditions.

^[1] https://www.epicresins.com/SolarEnergyBondingPottingEncapsulants/AdhesivesSealants

^[2] https://www.henkel-adhesives.com/us/en/industries/power-generation-and-conversion/solar-energy.html

Conclusion

Solar panels are comprised of various components that each serve an important function. The photovoltaic cells, typically made of monocrystalline silicon or polycrystalline silicon, are responsible for converting sunlight into electricity. These cells are encased within an encapsulant material and sandwiched between a glass covering and a plastic backsheet. The glass protects the cells while allowing sunlight to pass through, while the backsheet provides insulation and weatherproofing. Solar panels also contain a junction box with wiring to transport the generated electricity, as well as aluminum frames and various adhesives to hold all the components in place. The different materials and components work together to absorb sunlight and convert it into usable electricity through the photovoltaic effect.