Photovoltaic (PV) is a method of generating electrical power by converting solar radiation into direct current electricity using semiconductors that exhibit the photovoltaic effect. Photovoltaic power generation employs solar panels composed of a number of solar cells containing a photovoltaic material.Assemblies of photovoltaic cells are used to make solar modules which generate electrical power from sunlight. Multiple cells in an integrated group, all oriented in one plane, constitute a solar photovoltaic panel or "solar photovoltaic module," as distinguished from a "solar thermal module" or "solar hot water panel." The electrical energy generated from solar modules, colloquially referred to as solar power, is an example of solar energy.
A group of connected solar modules is called an "array." A photovoltaic system typically includes a panel or an array of solar modules, an inverter, and sometimes a battery and/or solar tracker and interconnection wiring. What is the construction of a solar cell/module and how does it work? Solar modules use light energy (photons) from the sun to generate electricity through the photovoltaic effect. The majority of modules use wafer-based crystalline silicon cells or thin-film cells based on cadmium telluride or silicon. The structural (load carrying) member of a module can either be the top layer or the back layer. Cells must also be protected from mechanical damage and moisture. Most solar modules are rigid, but semi-flexible ones are available, based on thin-film cells. Electrical connections are made in series to achieve a desired output voltage and/or in parallel to provide a desired current capability. The conducting wires that take the current off the modules may contain silver, copper or other non-magnetic conductive transition metals. The cells must be connected electrically to one another and to the rest of the system. Externally, popular terrestrial usage photovoltaic modules use MC3 (older) or MC4 connectors to facilitate easy weather proof connections to the rest of the system. Each solar module is rated by its DC output power under standard test conditions (STC), and typically ranges from 100 to 320 watts. The efficiency of a module determines the area of a module given the same rated output - an 8% efficient 230 watt module will have twice the area of a 16% efficient 230 watt module. A single solar module can produce only a limited amount of power; most installations contain multiple modules. Most solar modules are currently produced from silicon photovoltaic cells. What are silicon photovoltaic cells? A solar cell (also called a photovoltaic cell) is an electrical device that converts the energy of light directly into electricity by the photovoltaic effect. It is a form of photoelectric cell, defined as a device whose electrical characteristics—e.g. current, voltage, or resistance—vary when exposed to light. Cells can be described as photovoltaic even when the light source is not necessarily sunlight (lamplight, artificial light, etc.) Photovoltaic cells are used as a photodetector (for example infrared detectors), detecting light or other electromagnetic radiation near the visible range, or measuring light intensity.
The operation of a photovoltaic (PV) cell requires 3 basic attributes:
- The absorption of light, generating either electron-hole pairs or excitons.
- The separation of charge carriers of opposite types.
- The separate extraction of those carriers to an external circuit.
In contrast, a solar thermal collector supplies heat by absorbing sunlight, for the purpose of either direct heating or indirect electrical power generation from heat. A "photoelectrolytic cell" (photoelectrochemical cell), on the other hand, refers either to a type of photovoltaic cell (like that developed by Edmond Becquerel and modern dye-sensitized solar cells), or to a device that splits water directly into hydrogen and oxygen using only solar illumination. These silicon photovoltaic cells are typically categorized as mono crystalline or polycrystalline modules.
What is a monocrystalline module?
Single crystal or monocrystalline solid is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries. The absence of the defects associated with grain boundaries can give monocrystals unique properties, particularly mechanical, optical and electrical, which can also be anisotropic, depending on the type of crystallographic structure. These properties, in addition to making them precious in some gems, are industrially used in technological applications, especially in optics and electronics.
What is a polycrystalline module?
Polycrystalline materials are solids that are composed of many crystallites of varying size and orientation. The variation in direction can be random (called random texture) or directed, possibly due to growth and processing conditions. Fibre texture is an example of the latter. Polycrystalline is the structure of a solid material that, when cooled, forms crystallite grains at different points within it. The areas where these crystallite grains meet are known as grain boundaries.
How is the efficiency of a solar panel calculated?
Efficiencies of solar panels can be calculated by MPP (Maximum power point) value of solar panels A Solar inverter converts the DC power to AC power by performing MPPT processes: Solar inverters sample the output Power (I-V curve) from the solar cell and apply the proper resistance (load) to solar cells to obtain maximum power. MPP (Maximum power point) of a Solar panel consists of MPP voltage (V mpp) and MPP current (I mpp): it is a capacity of the solar panel and the higher value can make higher MPP. Many costs are proportional to the panel area or land area involved. A higher efficiency cell may reduce the required space and so reduce the total plant cost, even if individual cells are more costly. To be useful in evaluating solar costs, they must be evaluated under realistic conditions. Consumer installation costs have reduced only slowly, because of its reliance on human labour. Concentrated solar power offers greater economies of scale, given its much larger size. Solar modules must withstand rain, hail, and cycles of heat and cold for many years. Many crystalline silicon module manufacturers offer a warranty that guarantees electrical production for 10 years at 90% of rated power output and 25 years at 80%. Most parts of a solar module can be recycled including up to 97% of certain semiconductor materials or the glass as well as large amounts of ferrous and non-ferrous metals. Some private companies and non-profit organizations are currently engaged in take-back and recycling operations for end-of-life modules. Recycling possibilities depend on the kind of technology used in the modules.
Now you know all about solar panels and how they work!
Read further on how a photovoltaic system or PV system works.