Glossary
AC (alternating current)
AC is the abbreviation for alternating current whose polarity constantly changes periodically. Solar electricity is produced as direct current (DC) as a rule and must be converted to alternating current with an inverter before it is fed into the public grid.
DC (direct current)
The direct current is an electrical current whose polarity remains constant, i.e. doesn’t change.
Diffuse irradiation
The solar irradiation that reaches the earth´s surface indirectly from the sun (e.g. is first scattered by clouds, water and dust particles)
Direct normal irradiation
The solar irradiation that is incident on the earth coming directly from the sun (e.g. no scattering).
Efficiency
The efficiency gives the effectiveness of the energy conversion and of the energy transmission. It describes the ratio between the energy supplied and the energy input. A solar cell efficiency of 35% conveys that 35% of the incoming solar energy can be converted into electrical energy.
Electricity production costs
These are the costs that the energy producer must spend in order to produce the electricity. These costs are usually given in cost per kilowatt-hour.
Energy output
The energy output is the electricity yield of a system within a certain time period (mostly one year). The energy output of a photovoltaic system is dependent on different factors like location, system construction, seasons, influences from the surroundings, and the solar irradiation in a given year. The energy output is given in kWh.
Global irradiation
Global irradiation is the radiation incident on a horizontal area on the earth. It is comprised of direct, diffuse and reflected radiation. It indicates how much solar energy is available on the surface of the earth.
Grid Parity
Grid parity means that the electricity produced from a photovoltaic system costs exactly the same as the electricity that the consumer receives from the public electricity grid, therefore, making solar electricity economically competitive. Grid parity therefore is not related to the pure electricity production costs.
Inverter
An inverter is an electrical device that converts dc current into ac current, i.e. dc voltage into ac voltage.
Nominal Power
The nominal power is the potential power output of a system under standard test conditions. The nominal power of concentrator systems is given in watt (Wnom) and correlates to a direct radiation of 850 W/m².