Common Terms In The Photovoltaic Industry

The full name is photovoltaic effect, which is the phenomenon that an object generates electromotive force due to the absorption of photons. When an object is exposed to light, the charge distribution state inside the object changes, generating an electromotive force and current.

The power generation technology that uses the photovoltaic effect to directly convert solar energy into electrical energy.

Watt (W), kilowatt (kW), megawatt (MW), gigawatt (GW), terawatt (TW)

1TW=1000GW=1000000MW=1000000000kW=1000000000000W.

Kilowatt-hour (kWh), that is, 1kWh of electricity is 1 kilowatt-hour.

One of the key devices in the solar photovoltaic power generation system, its function is to convert the direct current generated by the solar cell into alternating current that meets the power quality requirements of the power grid.

The string inverter performs separate maximum power peak tracking for several groups (usually 1-4 groups) of photovoltaic strings, and then connects them to the AC power grid after inversion. A string inverter can have multiple maximum power peak tracking modules, with relatively small power, mainly used in distributed power generation systems and centralized photovoltaic power generation systems.

Solar cells can be packaged and protected in series to form a large area of ​​solar cell modules, and then combined with power controllers and other components to form a photovoltaic power generation device. The power generated by this device is the installed capacity.

The ratio of the component capacity of a photovoltaic power station to the inverter capacity (capacity ratio = photovoltaic system installed capacity/photovoltaic system rated capacity). Properly increasing the capacity ratio within a certain range can improve the utilization rate of other equipment, dilute the investment cost, reduce the construction cost and power generation cost, and make the output smoother and improve grid friendliness.

Automatic generation control (AGC), that is, active power control system, responds to the remote adjustment instructions issued by the dispatch, and optimizes the calculation through the AGC module total strategy to make the operating data meet the dispatching and grid-connected requirements.

Automatic voltage control (AVC), that is, reactive voltage regulation, responds quickly to the dispatching instructions according to the grid voltage curve, and automatically adjusts the reactive power, reactive compensation device and other control strategies and response time to achieve the voltage regulation target and reduce network losses.

It means that when the voltage at the photovoltaic power station grid-connected point fluctuates due to grid failure or disturbance, the photovoltaic power station can be connected to the grid uninterruptedly within a certain range.

An indicator that measures the ability of solar cells to convert light energy into electrical energy. The ratio of the optimal output power of a solar cell to the power of the solar radiation incident on its surface.

Abbreviated as cost per kilowatt-hour. The cost and power generation in the life cycle of the project are first leveled, and then the power generation cost is calculated, that is, the present value of the cost in the life cycle/the present value of the power generation in the life cycle.

Includes two meanings: power generation side parity and user side parity. Power generation side parity means that photovoltaic power generation can achieve reasonable profits even if it is purchased according to the grid-connected power price of traditional energy (without subsidies): user side parity means that the cost of photovoltaic power generation is lower than the power selling price. According to the type of user and its power purchase cost, it can be divided into industrial and commercial and residential user side parity.

The National Development and Reform Commission formulates the purchase price (tax included) of the power grid company for the grid-connected power generation of centralized photovoltaic power stations.

The number of operating hours of the average power generation equipment capacity in a region under full load operation conditions in a certain period of time, that is, the ratio of power generation to average installed capacity, reflects the utilization rate of power generation equipment in the region. The formula is: utilization hours = power generation/installed capacity.

The average full-load operating time of the generator set in one year: the proportion of the utilization hours of the power generation equipment in the 8760 hours per year, also known as the "equipment utilization rate".

Distributed power access points are equipped with switchgear dedicated to distributed power, such as direct access of distributed power to substations, switch stations, distribution room busbars, or ring network cabinets.

In a photovoltaic power generation system with decentralized inversion and centralized grid connection, the DC and AC transmission lines that combine the power output of each photovoltaic module string to the inverter through the combiner box and collect it to the power generation busbar through the inverter output end are called collector lines. The collector line can be sent out by overhead, direct burial or bridge laying.

It can be divided into DC combiner box and AC combiner box. The DC combiner box is a wiring device that ensures the orderly connection and convergence function of photovoltaic modules; the AC combiner box is to combine the output current of multiple inverters, while protecting the inverter from the harm from the AC grid-connected side/load, as the inverter output disconnection point, improving the safety of the system and protecting the safety of installation and maintenance personnel.

Generally, 400kW and below can be connected to the grid at low voltage of 380V. Between 400kW and 2MW, multiple grid connection points can be used for low voltage grid connection. If the power exceeds 2MW, 10kV grid connection is required. If the power exceeds 6MW, 35kV grid connection is required (refer to the requirements or suggestions of the local power grid company for details).

The power supply is divided into AC and DC, so it is divided into AC cables and DC cables. AC cables are used to connect AC power cables: DC cables are used for cables in DC transmission and distribution systems.

Based on high-quality monocrystalline silicon materials and processing technology, a type of solar cell is generally developed using technologies such as surface texturing, emitter passivation, and partition doping.

Using solar-grade polycrystalline silicon materials, the manufacturing process is similar to that of monocrystalline silicon solar cells. The current photoelectric conversion efficiency and production cost are slightly lower than those of monocrystalline solar cells.

Shingled modules are advanced technology modules designed with overlapping and close-packed design after the cells are cut and bonded with conductive glue. Replace the welding strip of traditional technology to increase the effective power generation area of ​​the cells.

Modules that can use the light incident on both the front and back sides to generate light energy. Usually, the back power of bifacial modules is more than 60% of the front power.

Modules made of bifacial cells and double-sided glass.

Special function brackets used to install, support and fix photovoltaic modules in photovoltaic power generation systems, including tracking brackets and fixed brackets.

Equipment that adjusts the spatial angle of the plane of the solar module relative to the incident sunlight in real time through the combined action of mechanical, electrical, electronic circuits and programs to increase the amount of sunlight projected on the module and increase the power generation.

The attenuation of the output power of cells and modules caused by long-term illumination.

Potential-induced degradation, that is, the long-term high voltage of the module causes leakage current between the glass and the packaging material, and a large amount of charge accumulates on the surface of the cell, which deteriorates the passivation effect of the cell surface and makes the module performance lower than the design standard.

Standard Test Conditions, mainly used in laboratories, refers to the ambient temperature of 25°C, air quality AM1.5, wind speed = 0m/s, 1000W/m².

Normal Operating Cell Temperature, the NOCT of normal modules is 45℃℃±2°℃. It refers to the temperature reached when the solar module or battery is in an open circuit state and (battery surface light intensity = 800W/m, ambient temperature = 20℃℃, wind speed = 1m/s).

Building Integrated Photovoltaic (photovoltaic building integration), photovoltaic materials used in photovoltaic buildings are embodied in the form of building materials, so photovoltaic building materials not only bear the function of power generation but also play a building function. Solar cells are compounded with building materials and directly applied to building roofs and walls and other enclosures.

Building Attached Photovoltaic (building attached photovoltaic). It is defined in contrast to BIPV. It mainly refers to solar photovoltaic power generation systems installed on existing buildings, also known as "installed" solar photovoltaic buildings. The main function of BAPV is to generate electricity, which does not conflict with the function of the building and does not destroy or weaken the function of the original building.

Emitter passivation and back contact cell. PERC cells have a market share of about 90% and are the most mainstream cell type in the current market.

Tunneling oxide passivation contact cell, N-type cell technology, high theoretical efficiency limit, and process similar to PECR.

Heterojunction cells with amorphous layers use different semiconductor materials to form heterojunctions. They have high theoretical efficiency and few processing steps, but they require extremely high process requirements.

Interdigitated back contact cells.

Mainly uses large-scale solar cell arrays to directly convert solar energy into direct current, connects to the power grid through AC distribution cabinets, step-up transformers and high-voltage switchgear, transmits photovoltaic power to the power grid, and the power grid uniformly allocates power to users.

Refers to photovoltaic power generation projects located near users, where the generated energy is used locally, connected to the power grid at a voltage level lower than 35kV or lower, and the total installed capacity of a single grid connection point generally does not exceed 6MW.

Refers to the deep integration of new generation information technologies such as 5G, Internet, big data, and artificial intelligence in the application of photovoltaics, so that photovoltaic power stations can maximize the value of power station owners and operators through the help of digital technology in all aspects from construction to operation.

This photovoltaic system mode is the most common mode, and generally distributed photovoltaic power generation systems mainly adopt this mode. The power generated by the photovoltaic system can first meet its own load use, and the excess power can be sold to the power grid to avoid waste: if the power generated by the photovoltaic system is insufficient for load use, it will be supplemented by power supply from the power grid. In this mode, the grid installs a two-way smart meter to measure the power generation of the photovoltaic power station and the power consumption of the user, and pays or collects electricity fees according to policies and negotiated electricity prices.

The salient feature of the self-generation and self-use grid-connected mode is "grid-connected but not connected to the grid". The access point of this mode is at the lower end of the grid meter, which is the private side of the complete property boundary. This photovoltaic system mode is generally used when the power load on the user side is large and the power load is continuous. The user is fully capable of using up the power generated by the photovoltaic power plant without causing waste.

This grid-connected mode is to directly connect the AC output of the photovoltaic system to the low-voltage side or high-voltage side of the grid, that is, the grid side of the property boundary. In this way, the power generated by the system is directly sold to the grid, and the sales price usually adopts the local average grid-connected power price, while the user's power price remains unchanged, the so-called "two lines of income and expenditure, each calculating its own account". This model of selling electricity directly to the grid is also the mainstream of photovoltaic applications; because its financial model is simple and relatively reliable, it is easy to be favored by investors.