Demand for the use of energy from renewable sources is constantly growing all over the world, its volumes and areas of application are increasing. But in solar energy, in addition to simple and familiar words, there are terms that few people know about and that can be confusing. To correctly use the benefits of alternative energy, to understand the dynamics of the development of this sector, you need to know the meanings of various specific terms.

In this article, we will help organize the information and explain some of the solar vocabulary to make it easier for you to get information about the solar energy industry.

Alternative Energy/Renewable Energy Sources

The term is used to refer to energy that comes from sources that do not harm the environment or their harm is minimal. The sources for this type of energy are usually natural and renewable (RES). It can be the energy of the sun, wind, biomass, geothermal energy, hydroelectric power. The use of various alternative sources helps to reduce the use of energy from limited sources such as fossil fuels (oil, gas, coal).

solar energy

Solar energy is electricity generated by using the energy of the sun. Energy is generated directly by solar panels, which collect energy from the sun and convert it into electricity.

Electrical/utility networks

An electrical or utility grid is a series of interconnected networks that help deliver electricity to the end consumer from generators.

The network consists of various components such as:

  • power plants that produce electricity;
  • electrical substations responsible for increasing the voltage for transmission or decreasing it for distribution;
  • high-voltage transmission lines that transmit energy from their sources to demand centers;
  • distribution lines to connect individual customers.

solar insolation

Solar insolation is a concept used in solar energy. It means the amount of sunlight entering 1 m 2 of a surface located perpendicular to the sun’s rays in one light day in a certain area.


Visible sunlight is only a fraction of the sun’s radiation. Ultraviolet radiation is an invisible part of solar energy and also affects the operation of solar panels. Ultraviolet is understood as electromagnetic radiation in the wavelength range from 5 to 400 nm.

Quantum Efficiency (QE)

The ratio of the number of charge carriers collected by a photovoltaic cell to the number of photons of a given energy emitted per cell. Quantum efficiency refers to the response of a solar cell to different wavelengths in the spectrum of light incident on the cell. QE is given depending on the wavelength or energy. Optimally, a solar cell should generate a significant electrical current for the wavelengths most common in sunlight.

Photoelectric (photovoltaic, photovoltaic PV)

This term comes from the words: “phos” (from Greek, light) and “volt” (from the name of the famous Italian physicist Volta, after whom the unit of electrical voltage is named). In physics, the word “photovoltaic” refers to anything that produces electricity when exposed to light or other radiant energy. In solar energy, the term “photovoltaic” refers to a technology that helps convert sunlight into electrical energy using semiconductor materials that absorb electrons from the sun. A photovoltaic system uses solar panels to produce solar energy. Solar cells and solar panels are often referred to as photovoltaic cells and photovoltaic panels to show how electricity is produced with them. Each solar module/panel consists of several solar cells that are responsible for generating electricity. Photovoltaic installations can be installed on the ground, on walls, on rooftops or be mobile.

Photoelectric (photovoltaic, photovoltaic, PV) effect

The phenomenon when, under the influence of light and as a result of a chemical / physical reaction, voltage and electric current appear in a substance.

Photovoltaic (PV) system

A complete set of components for converting sunlight into electricity through the photovoltaic process, including an array of panels and a Balance of System Components (BOS).

Solar cell (photovoltaic cell)

Technical term for solar panel elements. It is a special semiconductor-based device designed to convert solar energy into electrical energy. A solar cell, also known as a photovoltaic cell, is the main component of a solar panel. When sunlight hits the surface of a cell, the electrons in the cell are knocked out and electricity is generated. Each solar cell is usually made from a thin crystallized silicon wafer. A standard solar cell can generate about 1 or 2 watts of power. Some solar cells can generate 3 to 4.5 watts.

Solar panel/battery/module

These are several photocells combined into one block. The device is a collection of solar cells connected to each other in parallel, series or series-parallel. Usually solar cells are connected together to generate more power. A typical solar panel consists of 36-40 solar cells. To achieve the desired current and voltage, the solar panels are connected together to form an array. In each case, a different number of solar panels is required, which depends on the energy needs. However, the amount of energy also depends on the efficiency level of the solar panels.

Frame solar module

Solar module , placed in a frame made of aluminum or other material to give it tightness and greater rigidity.

Frameless solar module

Solar module that does not have a frame. Designed for operation in more gentle conditions than frame modules. Its front side is covered with PET or EVA film, the back side is covered with fiberglass or the same PET film.

Kilowatt hour (kWh)

This unit of measurement is an important term in the solar dictionary, denoting a standard unit of measure for electrical power.

Solar Panel Efficiency / Solar Panel Efficiency

One of the main characteristics of solar panels. This is a value that shows how much solar energy that hits the surface of a solar panel will be converted into useful electricity. Basically, it is the percentage of sunlight that the panels convert into electricity from the amount of sunlight they receive. The efficiency of most solar panels on the market today ranges from 15% to 24%. The efficiency is affected by the type and quality of the semiconductor used in the panels, as well as the manufacturing technology. Monocrystalline solar panels have the highest efficiency (on average, 19–24%), polycrystalline panels with an indicator of approximately 15–19% are considered slightly less efficient, and thin-film panels made of amorphous silicon close the top three most common panels (their efficiency depends on the semiconductor used, the value ranges from 8 to 16%). A lot of research in the field of RES (renewable energy sources) is aimed at increasing the efficiency of panels, making solar energy more competitive compared to traditional energy.

Peak demand / load

The maximum energy demand in a certain time interval.

Crystalline silicon (C-Si)

It is a material/substance that is the various crystalline forms of silicon used to produce the most common types of solar panels that are made from silicon (poly and monocrystalline).

Polycrystalline silicon (multi-silicon)

Material (silicon), which is obtained using the method of directional crystallization. Outwardly, it looks like rectangular blocks. It is a high-purity material used to make photovoltaic cells, which are made up of many small silicon crystals (crystallites) and obtained by industrial purification.

Polycrystalline panels

Panels made on the basis of polycrystalline silicon. This is one of the most common and popular types of panels. Such solar panels are highly efficient and durable.

Monocrystalline silicon

Material (silicon), which is obtained mainly by the Czochralski method. Outwardly, it looks like cylindrical ingots.

Monocrystalline panels

One of the most commonly used types of solar panels. Made from silicon, these crystalline panels are long lasting, the most efficient on the market, and have an aesthetically pleasing design. They are a single crystal of silicon, and their high cost is due to the laborious and painstaking process of their manufacture.

amorphous semiconductor

A substance in an amorphous (shapeless) state, a non-crystalline semiconductor material that has a number of properties characteristic of crystalline semiconductors.

Amorphous silicon

Amorphous silicon (a-Si) is a non-crystalline form of silicon that is used in the production of solar cells ( thin-film panels ), thin-film transistors in LCDs. This material is obtained by sputtering onto a substrate using the evaporation technique and then protected with a special coating.

Thin film

A layer of semiconductor material (copper-indium diselenide, gallium arsenide, etc.) a few microns or less thick, used to make solar cells.

Thin Film Solar Module

Solar module , the structure of which consists of successive layers (thin films) of semiconductor materials.


It is any substance/material capable of conducting current under certain conditions. Some semiconductors are uniquely suited to the photovoltaic power conversion process. Among them, silicon, copper-indium diselenide, gallium arsenide, cadmium telluride, etc.).


A material through which electricity is transmitted, such as an electrical wire, transmission or distribution line.

Conduction band

This term refers to the energy band in a semiconductor where electrons in a solid can move freely, creating a net charge transfer.


A term that refers to one complete discharge and recharge of a battery.

Battery life

The period of time during which the battery will operate at the specified efficiency in accordance with the manufacturer’s instructions. Read more…

Ground solar panels

This is a set of solar panels that are installed on the ground, an alternative to installing panels on the roof. This method of mounting solar panels is designed for large solar projects (municipal, agricultural, industrial). These include large power plants that generate solar energy for a large number of households and businesses. The ground array is usually located on racks next to the buildings, structures for which they provide electricity.

Peak hours of solar radiation

Not to be confused with hourly day. Peak hours refer to the quality of sunlight that solar panels absorb, not the amount of time the panels are exposed to daylight. These are the hours of the day, the intensity of sunlight which is 1000 watts per square meter. Peak sunshine hours, measured in kilowatt-hours per square meter (kWh/m 2 ), depend on time of day, season, presence of clouds, and geographic location. Even if solar panels can receive partial sunlight for eight hours on a given day, on average this can only be 3 or 4 peak solar hours.

Balance System (BOS)

The solar system consists not only of solar panels – it includes many different elements and equipment. The term BOS ( balance of system or system balance) just refers to all other components of the solar system, except for the panels. These include wiring, inverters, monitoring system and all equipment.

Back sheet or backing

This is the “back side” of the solar panel. Protects the internal parts of the panel from influences that, over time, can reduce the effectiveness of the panel – moisture and ultraviolet radiation. High quality back sheets are important to ensure that panels last at least 25 years.

Mounting system

This is what physically holds the solar panels in place. This includes shelving/stands, front skirts, air vents, rails, top clamps and more. The fixing system is an important part, as it affects the condition of both panels and installation sites, including the appearance of the building facade, roof, etc.

Autonomous solar system

Stand-alone or hybrid photovoltaic system not connected to the grid.


A device that can convert energy into different forms: from chemical to electrical and vice versa, and accumulate it. Reactions in the process of energy transformation are almost completely reversible. When the battery is discharged, chemical energy is converted into electrical energy and consumed in an external circuit or device.

battery element

The simplest productive block in the battery. It consists of: one or more positive electrodes or plates, one or more negative electrodes or plates, an electrolyte that provides ionic conductivity, separators between the plates with opposite polarity and a container for all of the above.

Accumulator battery

Energy storage using electrochemical batteries. Among their main tasks, in addition to the energy reserve, load balancing at substations and peak load reduction.

Rated battery capacity

A term used by battery manufacturers to refer to the maximum amount of energy that can be drawn from a battery at a given/specified battery discharge rate and temperature.

solar battery

A device or system of interconnected high-capacity batteries that helps store excess energy produced by solar panels. Batteries guarantee the supply of energy to the consumer even in the absence of sunlight, for example, when it gets dark.

Battery capacity

The maximum electrical charge that a battery can deliver under certain conditions. Expressed in ampere-hours.


A solar inverter is a device that converts the direct current received from solar panels into alternating current. Without an inverter, it is not possible to easily use the energy of solar panels, since the DC energy produced by the solar panel must be converted to AC electricity in order to be used in household appliances. In addition, inverters provide many levels of monitoring, long-term savings and system efficiency. There are three main types of inverters:

  • microinverters are installed in separate solar panels and are ideal for small solar power systems.
  • string inverters ideal for large residential or small commercial establishments.
  • central inverters are ideal for large scale systems such as solar power plants.


Unlike a conventional inverter that converts the DC current of multiple solar panels to AC, the micro-inverter does the same but only for one solar module.

Inverter efficiency

How well the inverter converts DC to AC with minimal loss.

charge controller

The controller is a key part of the system, ensuring highly efficient operation of the solar panels. It is a component of a photovoltaic system that helps maintain the correct “output” voltage, thereby controlling the flow of current to and from the battery to avoid overcharging/discharging the battery. It monitors the battery level and turns it off when it reaches the maximum.

Absorber (absorber)

In a photovoltaic device, this is a material that easily absorbs light particles (photons), while generating charge carriers – free electrons or holes (the place where an electron is usually located in a solid body; in relation to solar energy, a hole behaves like a positively charged particle).

Anti-reflection coating of solar cells

A thin coating of material applied to the surface of a solar cell that reduces light reflection and increases the transmission capacity of the solar cell.

Rack / rack

This term refers to the fixture on which solar panels are mounted when they are placed on the roof or on the ground. The studs are bolted to the roof or base on the ground, and the panels are connected to the studs. Depending on the installation location, the design features of the panels themselves and other factors, different types of racks and different distances between them can be used.

Junction box

The term refers to the structure, which is a casing on the module that protects against atmospheric influences. This is, in fact, the transition from the solar panel to the wires coming from the controller.


This is a design with optical components, such as Fresnel lenses, that focus, direct and concentrate sunlight, which helps to increase the efficiency of the panels. The arrays of concentrators must be directly facing the Sun, so they can increase the power flow of sunlight hundreds of times.


A device for converting AC to DC.


A device for preventing batteries from being overcharged by managing charge cycles, which is usually adjusted to suit the specific needs of the battery.


A chemical reaction that eliminates the harmful effects of electrically reactive atoms on the surface of a solar cell.


The movement of a free electron back into a hole (the place where an electron would normally reside in a solid; when applied to solar energy, a hole behaves like a positively charged particle). Recombination processes are usually radiative (recombination energy leads to the emission of a photon) or non-radiative (recombination energy is given to a second electron, which then relaxes back to its original energy, releasing photons). Recombination can occur both in the bulk of a semiconductor and on its surfaces, in the junction region, on defects, or between interfaces.

Integrated photovoltaics (BIPV)

This term refers to solar panels that are integrated into buildings. BIPV modules typically replace other traditional building materials while also acting as power generators. They can be built into building facades, roofs and awnings, and some solar cells can even replace certain types of glass and windows.

Reserve power

The amount of generated power supported by the central grid to meet peak loads.

Standard Test Conditions (STC)

Conditions under which solar panels are tested in the laboratory.

solar power plant

A solar power plant is an extensive solar array or array of interconnected solar panels whose purpose is to produce solar energy for large commercial, industrial, agricultural, or municipal use.

Cleaning solar panels

The process of collecting dust and debris that accumulates on solar panels and prevents sunlight from entering (dirt, snow, leaves, tree branches, animal and bird traces, etc.). Natural cleaning, such as rain, can clean solar panels to some extent, but in most cases this must be done manually by yourself or with the help of specialists. Timely and regular cleaning of the panels is a guarantee that they will not lose their effectiveness.

Green tariff

This scheme enables solar energy consumers to earn revenues for electricity returned to the general flow of the national energy system due to the formation of surpluses. Today, in many countries of the world there is a special preferential tariff for individuals and legal entities that have installed solar panels. These are special conditions under which the state, at a somewhat inflated price, undertakes to buy out the entire volume of excess electricity supplied to the public grid and generated from renewable energy sources.

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