Terminology and nomenclature
Solar cell – the smallest component of a PV module, a standard 4-7 inch (or other) silicon, poly- or monocrystalline tile, connected to other cells to form a cell string. Also known as a photovoltaic cell.
Cell string – a series of photovoltaic cells, a component of poly- or monocrystalline PV modules, which – after lamination – form the main part of a PV module.
Solar panel – in planners’ nomenclature, it is the name of the PV module without an external frame. The panel/panel application without the frame is often used as an element of façade or roofing constituting an esthetic element of architecture.
PV module – a basic unit of the PV power system – usually in an aluminum frame. Equipped with cable outlets or a socket to which remaining components may be connected. PV modules may be rigid or flexible.
PV inverter – a voltage inverter allowing for the compatibility of PV systems operating in a direct current environment with devices or a power grid operating in an alternating voltage environment (230 V). In systems connected to the grid (PV Ongrid), inverters forward the current in a single or three-phase mode. The efficiency of high-quality inverters reaches up to 97-98 %. Besides PV modules, inverters are a very important element of a PV system and have a significant impact on its long-lasting and problem-free operation.
Charge controller – a device controlling the process of battery charging (12/24V) in mobile or offgrid PV systems. The device controls the voltage level of the charged battery and turns the voltage off after the battery is charged. The controller protects the battery or a group of batteries against overcharging or damage.
Charge monitor – a device allowing for the monitoring of the battery voltage level and power production by the PV system. The device is usually equipped with a display of the status of the system (charging power) and informs on the charging level of the battery.
Theory of photovoltaic (PV) systems
Do you know, that:
PV is an international abbreviation for the photovoltaic effect (PV = PhotoVoltaic), a technology of power production based on solar energy. Like most breakthrough solutions, the PV technology originated from military technologies.
Theory of photovoltaic (PV) systems
Several forms and technologies may be distinguished among solar systems. EBORX concentrates on two main systems: photovoltaic (PV) – which produces electric power, and thermal which produces thermal energy.
Solar systems may be divided into subgroups depending on their purpose and application (international nomenclature):
PV Ongrid – solar power plant systems, sales of electricity
(On Grid = connected to grid)
PV Offgrid – autonomous and island PV systems
(Off Grid = disconnected from grid)
PV Automotive – PV power for electric vehicles
PV Mobile – mobile PV power systems for mobile devices
PV – technology of electric power production
Do you know, that:
In 1957, Sputnik 3 – a satellite of the Russian Military Agency (then USSR) was the first spacecraft powered by a PV system.
Values and parameters of PV systems
CRITICAL VALUES AND PARAMETERS OF PHOTOVOLTAIC SYSTEMS
Solar radiation (kWh/m2)
In Poland, the yearly solar radiation power per one square meter (!) assumes a mean value of 1000 kWh, which corresponds to the energy of 100 l of fuel oil or 100 m3 of natural gas. For comparison, 1000 kWh is a yearly electric power demand of a single person’s household. A four-person family (2+2) has a yearly demand of approximately 2000 kWh (yearly consumption of electric power excluding heating).
Solar power is processed to electric or thermal energy by means of thermal conversion or PV technology and the conversion level expressed as a percentage determines the efficiency of a PV module or a solar collector.
THE INSOLATION TABLES MAY BE DOWNLOADED FROM THE WEBSITE (http://re.jrc.ec.europa.eu/pvgis/countries/countries-europe.htm)
System efficiencies (%, Wh)
The level of conversion of solar energy into electric or thermal energy is measured as a percentage.
PV – the efficiency of PV modules expressed as a percentage informs of the level of solar energy reaching the PV module that will be processed into electric energy. As an example, a PV module with an efficiency of 15 % and a surface of 1 m2 will produce 150 Wh of electric energy (>> in line with STC*). On days with a smaller insolation, the production of electric power will decrease. Various PV technologies (mono and poly-crystalline, amorphous) are characterized by varying efficiency.
*STC (» Standard Test Conditions): perpendicular solar radiation with a power of 1000 W per 1 m2 at a temperature of 25°C. AM=1,5 spectrum (Air Mass).
Power, current (Wp, mA):
Watt (W) power unit is used for all solar systems. The Watt unit that is provided is specified as Watt Peak, that is, the peak power, calculated in line with the international STC standard (definition above). In case of smaller PV modules, also the current is provided – expressed as milliamperes (mA) – which often constitutes a part of a PV symbol, e.g. Sunsei SE-1200 (1200mA) or » CL-600 (600mA).
The module power given in the name of the PV, e.g. 190W or 220W specifies the peak power (Wp) of power production and does not relate to the efficiency of the module. This means that the efficiency of a PV module characterized by 190 Wp power is similar or close to similar of the 220 Wp module’s efficiency. The 220 W module’s surface is, however, larger (usually it is equipped with an additional string of cells (60 cells) in relation to a 190 W module equipped with 50 cells, or the cells have a larger surface). The technological efficiency of the 190 and 220 Wp modules is, however, similar.
Often the modules offered by a manufacturer will be characterized by varying nominal power despite a single size (gross frame size). For example, 210, 220 and 230 Wp modules have the same frame size and the same aperture size. The differences in their nominal power result from technological efficiency of the PV cells used in the module structure. Before the process of module installation, the cells are tested/flashed and sorted into several classes depending on their efficiency (see the “Manufacturing PV Cells, test/flash, sorting” video on our blog >> PV Video). Using such graded cells, modules of one size and different nominal powers may be manufactured. The diversified efficiency of cells of the same size (surface) may depend on several factors, but the main reason is the thickness of silicone ingot cutting, which, although very precise technologies are employed, may vary from cell to cell.
Do you know, that:
Currently, the mass production of PV systems results in their application in a wide range of power feed systems as a wearable device, special technical equipment, element of architecture, in industrial and personal power systems.
PV systems
Intended use:
In ongrid PV systems (DC/AC 230 V environment) the production of power proceeds as power feed from the PV system to local power grid and sales of the produced power. The price and the form of purchase is statutory-regulated in most of the EU member states. This system has a basic advantage over the other PV systems as it is oriented on the yearly production of power which is constant and known for a given latitude of the power plant. The system is independent from daily weather conditions and acts as a money box/meter which produces and sells a given amount of electric power in a year. Any deviation from the forecasted yearly production by 10 % would indicate a system malfunction or extraordinary weather changes. These occur, yet are profitable for solar power plants and the profitability of the ongrid PV systems is largely dependent on the power purchase prices.
In offgrid PV systems (DC 12/24/48 V environment), the power production proceeds by storing electric energy in batteries or the power is directly consumed in the place and at the time of production. The system is used for autonomous and island systems and requires precise determination of all significant system parameters and components: the exposure to solar radiation in the system location, daily consumption of power, selection of appropriate battery and PV system power, storing temperature and possible levels of discharge and self discharge of a battery. The above parameters vary significantly within a year – especially the sun exposure and the ambient temperature of the battery. The greatest challenge, as far as the offgrid systems are concerned, is the power storage, that is, the battery. Such a system, e.g. in combination with modern lighting technologies and power-saving devices, is a perfect solution wherever using power from the grid is not profitable or impossible.
Do you know, that:
The PV technology allows for autonomous production of electricity at zero CO2 emissions in locations with no local power grid. The PV systems produce power also on cloudy days.
PV modules which are a basic unit of a PV system are characterized by estimated life of 30 years and the system operates as maintenance-free for nearly the entire period of its life.