Solar cell technology has been around for over 60 years. Solar modules, commonly called photovoltaic panels, have been used to generate electricity from light since the silicon-based semiconductor was invented. No longer a laboratory curiosity, solar cells are an industry unto themselves and are just as common in power generation as conventional methods of power generation, such as steam turbine-driven generators and power plants. nuclear. There are many methods of collecting solar energy in use and available today. We will investigate the most common electricity-producing solar energy devices: photovoltaic cells and photovoltaic modules.

How does a photovoltaic module generate electricity from light?

Solar cell

Solar cells are made of materials that are electrically activated when light falls on their surfaces. This unit, a solar cell, works with no moving parts and never wears out! Add many cells together and you have a solar array or photovoltaic module. The more cells, the greater the power that is possible to generate from the modules.

cell layers

The top layer of the solar cell or wafer contains a layer of silicon that has free electrons that are negatively charged particles. A boron-enhanced bottom shell contains gaps or holes that allow electrons to move into the open spaces. The manufacturing process creates this imbalance of electrons between the two layers within this semiconductor material. This imbalance is responsible for the operation of the solar cell that creates the electrical current and voltage.

The sun hits the solar cell

Photons from the sun strike the outside of the photovoltaic cell. This activity excites the free electrons in both silicon layers. Some electrons in the bottom shell travel to the silicon layer at the top of the cell. The flow of electrons moves across metal contacts located on the front and back of the solar cell, generating electricity. Electrons flow in a closed loop or electrical circuit. Combining multiple solar cells has an additive effect on voltage and current depending on how they are “tied together”. Think of each cell like a battery. Placing the cells in series (from negative to positive) will add voltage and keep the amperage the same as for one cell. Placing the cells in parallel will keep the voltage the same as for one cell, but will add the amperage of the cells.

solar powered power

Solar panels generate electrical current that is transmitted to an inverter. The inverter changes direct current into alternating current that matches the electricity your power company provides. Electrical appliances and equipment run on alternating current. In the United States, power is generated at 60 hertz, while in Europe, 50 hertz is the norm.

Solar electric power feeds the wiring of a home, business, or power station and the electrical grid of the utility company. An independently operated power system can also act as its own utility company. This “off-grid” system requires batteries to store power when the solar panels produce more power than the load needs and discharges when the solar modules cannot capture enough energy from the sun to offset the electrical loads of the home or business.

Conversion of silicon wafers into photovoltaic cells

The computer chip industry has made low-cost production of the solar cell possible. Advances in performance, processing, and quality have made the manufacturing process for photovoltaic cells scalable and state-of-the-art. While the process is mature for the production of silicon wafers, the techniques are time consuming and important to achieve the desired performance results. The silicon wafer starts out as an ingot of silicone material and is then sawn into the characteristically round wafers seen on a solar module.

recordinga wafer

The part of the solar cell process that requires a clean room incorporates chemical and thermal treatments that turn grayish silicon wafers into living blue cells. A chemical etch removes a small layer of silicon. Beneath this layer, a crystal structure reveals a pyramid-shaped surface that absorbs more light.

broadcasting

Silicon wafers are placed in ovens where the phosphor diffuses into the wafer surface. This step deposits a molecular-sized deposit as the wafer surface is exposed to high-temperature phosphor gas. This step gives the surface a potential negative electrical charge. This layer and the boron-doped layer below the surface create a positive-negative, or P/N, junction, which is the basis of a photovoltaic cell. This is also how a semiconductor chip is made.

color and print

The cells are placed in vacuum chambers where silicon nitride is deposited on the side of the wafer that will be exposed to sunlight. The silicon nitride coating is designed to reduce light reflection. This process gives the cell its dark blue color. The cell is ready to produce electricity, but it still needs a means to collect and send the energy to the load. Metal strips are printed on both sides of the cell so electrical charge collection and landing areas for wires can be added to the wafer. When this step is complete, the cell is ready to produce power.

Placement of cells in solar panels

The cells are arranged to create the voltage and amperage profile of the complete solar panel. If you look at the various brands of solar panels on the market, you’ll notice that cell arrangement dictates these attributes of home solar panels and commercial-type solar panels. Consequently, the physical size of the PV module frame is set by the arrangement of the solar cells.

Welding

The cells are soldered together in series strings, which involves electrically bonding the wafers together to form a module. Several strings are connected to form a rectangular array of cells. Each cell array is laminated to glass using a strong adhesive system that ensures the entire panel will survive normal environmental loads.

Framed

The outer frame of the solar module provides protection against weather and impact loads and also includes the electrical connection which could be a junction box or a standard electrical cable connector. These are commonly used in other electrical devices.

Rent, Rent, Rent

The location of the solar module array requires the opportunity to collect as much sunlight as possible during the seasonal variation in sun intensity.

Roof systems provide a ready platform as the surface often slopes towards the sun and the surface cannot be used for most other devices.

Floor mounted systems are good options when ceilings are not available or have too small an area. The modules are mounted in racks that are anchored to the ground and accessible for service or adding additional solar modules.

Canopy systems work well in shed roof applications such as parking areas.

Utility scale systems are typically large scale power generating units that are sized for utility grade use and are generally not limited in land area.

Tracking systems optimize power output by moving solar modules according to the path of the sun.

Summary

Solar modules are a union of solar cells and the technology that makes computer chips cheaper than just a decade ago. The inherent reliability of solar modules used for home solar panels is due to the lack of moving parts and the highly reliable parts and processes that make the solar module a reality. There are virtually no limits to the types of solar electric systems that can be designed and very few limitations on location, as long as there is abundant sunlight.