Solar resource terms
Acronym | Full Name | Units | Description |
|---|---|---|---|
ALB | Ground surface albedo | - | The fraction of solar irradiance reflected by the surface is calculated as the ratio of upwelling to downwelling radiative fluxes at the surface. |
D2G | Ratio of diffuse to global irradiation | - | Ratio of diffuse horizontal irradiation (DIF) to global horizontal irradiation (GHI). |
DIF | Diffuse horizontal irradiation | kWh/m² | The radiative flux integrated over a period of time from the sun scattered by the atmosphere falling on a horizontal plane surface. |
DNI | Direct normal irradiation | kWh/m² | The radiative flux integrated over a period of time from the sun falling on a plane surface at 90° to the beam while scattered light from the sky is excluded. |
DNI season | DNI seasonality | - | The ratio of maximum to minimum monthly averages of direct normal irradiation, indicating seasonal variability. |
GHI | Global horizontal irradiation | kWh/m² | AThe radiative flux integrated over a period of time from the sun falling on a horizontal plane surface. |
GHI season | GHI seasonality | - | The ratio of maximum to minimum monthly averages of global horizontal irradiation, indicating seasonal variability. |
GTI opta | Global tilted irradiation at the optimum angle | kWh/m² | AThe radiative flux integrated over a period of time from the sun falling on a tilted plane of PV modules mounted at the optimum angle. |
Solar resource | Solar resource | - | Encompasses information on the availability and intensity of solar radiation at a specific location, used to assess solar energy generation potential. |
Solar spectrum | Solar spectrum | - | The total distribution of electromagnetic radiation emitted by the sun. |
Meteorological resource terms
Acronym | Full Name | Units | Description |
|---|---|---|---|
CDD | Cooling degree days | degree days | Measures energy demand needed to cool a building by quantifying how much and for how long outside air temperature exceeds a base temperature (18°C)2. |
HDD | Heating degree days | degree days | Measures energy demand needed to heat a building by quantifying how much and for how long outside air temperature is below a base temperature (18°C). |
PREC | Precipitation (rainfall) | mm | Average yearly and monthly sums of precipitation. |
PWAT | Precipitable water | kg/m² | Depth of water vapor in the atmosphere if precipitated as rain, indicating atmospheric moisture. |
RH | Relative humidity | % | Average yearly or monthly relative humidity at 2 m above ground. |
TEMP | Air temperature | °C, °F | Average yearly, monthly, and daily air temperature at 2 m above ground. |
TD | Dew point temperature | °C, °F | The temperature at which air becomes saturated with moisture and dew begins to form. It is used to assess the risk of condensation, accelerated corrosion, and degradation of PV components. |
WBT | Wet bulb temperature | °C, °F | The lowest temperature to which air can be cooled by the evaporation of water at constant pressure. It is an indicator of thermal comfort and is used to assess the cooling efficiency of PV modules in humid environments. |
WS | Wind speed | m/s | Average yearly, monthly, and daily wind speed at 10 m above ground. |
Environmental resource terms
Acronym | Full Name | Units | Description |
|---|---|---|---|
Horizontal shading | Horizontal shading | - | Refers to distant objects blocking sunlight and creating shading on solar panels or surfaces. |
SDWE | Snow depth water equivalent | cm, inch | Measures liquid water content in a snowpack if melted. |
SNOWD | Snow days | days | Days with snow water depth equivalent to or higher than 5 mm. |
Electrical and technical terms
Acronym | Full Name | Units | Description |
|---|---|---|---|
AC | Alternating Current | V (Volts) | An electric current that periodically reverses direction, typically at a frequency of 50 or 60 Hz. |
A | Current | A (Amperes) | The unit for electric current; the flow of electrons. One ampere is 1 coulomb passing in one second. |
Array | Photovoltaic Array | - | An interconnected system of PV modules that function as a single electricity-producing unit. |
Azimuth | Azimuth Angle | Degrees | The angle between the north direction and the projection of the surface normal into the horizontal plane; measured clockwise from north. |
Backtracking | Backtracking Strategy | - | A control strategy that adjusts the tilt angle of modules to minimize shading between rows, maximizing overall energy production. |
Cell | Photovoltaic Cell | - | The smallest semiconductor element within a PV module that converts light into electrical energy (DC voltage and current). |
DC | Direct Current | A (Amperes) | Electric current in which electrons flow in one direction only. |
DC/AC ratio | DC/AC Ratio | - | Also known as the inverter loading ratio (ILR), it is the ratio of the total DC power output of a PV system's solar panels to the AC power rating of the system's inverter. |
Distributed systems | Distributed Systems | - | Systems installed at or near the location where electricity is used, as opposed to central systems that supply electricity to grids. |
Effective tilt | Effective tilt | degrees | An optimized angle at which solar panels are positioned to achieve maximum energy production accounting for specific conditions such as shading, snow accumulation, or seasonal variations in sunlight. |
Electrical Grid | Electrical Grid | - | An integrated system of electricity distribution, usually covering a large area. |
Fractional table | Fractional Table | - | A mounting structure designed to hold a specific fraction of the total number of PV modules in a string, allowing for modular and flexible array configurations. |
Grid Connection | Grid Connection | - | A connection point where the PV array connects to the distribution grid, supplying power to the grid. |
Inverter | Inverter | - | A device that converts DC electricity into AC electricity for stand-alone or utility-interactive systems. |
kW | Kilowatt | - | A unit of power; 1 kW = 1000 watts. |
kWh | Kilowatt-hour | - | A unit of energy; 1 kWh = 1000 watts acting over a period of 1 hour. |
Load | Load | - | Anything in an electrical circuit that draws power when the circuit is turned on. |
Module | Photovoltaic Module | - | The smallest environmentally protected assembly of solar cells and ancillary parts, intended to generate DC power under unconcentrated sunlight. |
Ohm | Ohm | Ω (Ohms) | The unit of resistance to the flow of an electric current. |
One-axis tracking | One-axis Tracking | - | A system capable of rotating about one axis, usually following the sun from East to West. |
Parallel connection | Parallel Connection | - | A way of joining electricity-producing devices by connecting positive leads together and negative leads together; increases the current. |
Peak load | Peak Load | - | The maximum load or usage of electrical power occurring in a given period of time, typically a day. |
Performance variability | Performance Variability | - | Refers to the extent of fluctuation or deviation from a consistent level of performance, often measured by the dispersion of outcomes over time. |
Photovoltaic (PV) array | PV Array | - | An interconnected system of PV modules that function as a single electricity-producing unit. |
Photovoltaic (PV) cell | PV Cell | - | The smallest semiconductor element within a PV module that converts light into electrical energy (DC voltage and current). |
Photovoltaic (PV) efficiency | PV Efficiency | % | The ratio of electric power produced by a cell at any instant to the power of the sunlight striking the cell. |
Photovoltaic (PV) module | PV Module | - | The smallest environmentally protected assembly of solar cells and ancillary parts, intended to generate DC power under unconcentrated sunlight. |
Photovoltaic (PV) panel | PV Panel | - | Often used interchangeably with PV module, but more accurately refers to a physically connected collection of modules. |
Photovoltaic (PV) system | PV System | - | A complete set of components for converting sunlight into electricity by the photovoltaic process, including the array and balance of system components. |
Power factor | Power Factor | - | The ratio of the average power and the apparent volt-amperes. Affected by the inductance and capacitance of the load. |
Safe zone (inverters) | Safe Zone | - | Refers to the specific area or distance around the inverter that ensures proper ventilation, accessibility for maintenance, and protection from environmental hazards. |
Series connection | Series Connection | - | A way of joining photovoltaic cells or batteries by connecting positive leads to negative leads; increases the voltage. |
Soiling losses | Soiling Losses | - | Refer to the reduction in energy output caused by the accumulation of dirt, dust, pollution, or other contaminants on the surface of solar panels. |
Solar energy | Solar Energy | - | Energy from the sun. |
Stand-alone PV system | Stand-alone PV System | - | An autonomous or hybrid photovoltaic system not connected to a grid. May or may not have storage, but most stand-alone systems require batteries or some other form of storage. |
String size | String Size | - | Refers to the number of photovoltaic (PV) modules connected in series within a solar array, determining the overall voltage of the string. |
tilt | tilt | degrees | The angle at which solar panels are installed relative to the horizontal plane. This angle is typically set to match the geographical latitude of the installation site to maximize sunlight exposure and energy production. |
Transformer | Transformer | - | Steps AC voltage up or down, depending on the application. |
Transformer class | Transformer Class | - | Refers to the classification of a transformer based on its voltage rating, application, insulation type, cooling method, and other specifications. |
Two-axis tracking | Two-axis Tracking | - | A system capable of rotating independently about two axes (e.g., vertical and horizontal) and following the sun for maximum efficiency of the solar array. |
Vac | Voltage of Alternating Current | V (Volts) | Refers to the voltage of alternating current (AC) in a PV system or electrical circuit, typically representing the output voltage from an inverter or the grid voltage to which the system is connected. |
Voc | Open-circuit Voltage | V (Volts) | The maximum possible voltage across a photovoltaic cell or module when no current is flowing. |
Watt | Watt | W (Watts) | The unit of electric power; 1 watt = 1 joule per second. |
Wh | Watt-hour | Wh (Watt-hours) | A unit of energy; see kilowatt-hour for a larger unit. |