Glossary O - Z

O

Open circuit voltage
Voltage measured on the connection terminals of a solar module or solar cell, with current switched off.

Output
The amount of energy produced within a certain period of time. The applicable unit is watt (W).

P

Peak output
See Kilowatt peak.

Photovoltaics
Photovoltaics is the name of the solar technology that converts sunlight into electrical current. The term is derived from “photon” (Greek for light) and the name of the physicist Alessandro Volta (1745-1827).

Polycrystalline cell structure
Silicon with a partially ordered crystal structure. The basic material for polycrystalline solar cells. The blue solar cells have a textured crystalline appearance typical of PV modules. Polycrystalline cells are slightly less effective than monocrystalline cells, but play a substantial part in the PV industry due to the special fabrication technology and high manufacturing capacities. Polycrystalline PV modules represent good value for money.

PV
Abbreviation for photovoltaic.

PV module
Solar cells that are interconnected and encapsulated to achieve certain process parameters and for their mechanical protection.

R

Rated output
Output of a solar module (solar cell) at the MPP

Rated current
Current generated by a solar module (solar cell) at the MPP.

Renewable energy sources
The energy sources which, in human terms, are inexhaustible. These are: Solar power, geothermal, tidal and biomass energy.

S

Silicon
After oxygen, the second most common chemical element on Earth. It is the basic material for the semiconductor industry, and a raw material used for manufacturing solar cells. Silicon is mainly available as quartz sand (SiO2) in combination with oxygen, not as an element.

Shading
Shading of solar systems from protruding roofs or trees leads to reduced solar energy output.

Solar
(lat.) relating to the sun

Solar system
System for transforming solar radiation into usable energy in the form of heat (solar thermal system) or electricity (photovoltaic system).

Solar thermal system
System for converting solar radiation into usable energy in the form of heat.

Solar coverage
See Coverage level.

Solar generator
See Generator.

Solar electricity
DC current generated directly in solar cells.

Solar cell
When solar cells come into contact with light or heat, positively and negatively charged particles are released (photo effect), generating direct current.

Standard Test Conditions (STC)
In order to enable objective comparison of different PV modules and solar cells, the following standard test conditions have been defined for determining their characteristics:
1. An irradiation E of 1000 W/m²
2. A cell temperature T of 25°C with a tolerance of ± 2°C
3. A defined light spectrum AM = 1.5

System utilisation, Level of
Ratio of solar output to total amount of irradiation. This is a measure of the overall efficiency of the solar energy system.

T

Thin film technology
Technology used to manufacture solar cells, that allows for savings in materials. In this process, photoactive semiconductors are applied to a substrate (e.g. glass) as thin films.

V

V
Abbreviation for volt. Unit of electrical charge.

W

W
Abbreviation for watt. Unit of electrical output.