SMA Sunny Island 2012 Technical Description page 210

SMA Solar Technology AG
Glossary
SOC
State of Charge: the charge level of the battery, see Charge Level. If, for example, 25 Ah is taken
from a 100-Ah battery, the charge level (SOC) is then 75 %.
SOH
State of health: describes the relationship between the present capacity and the battery's nominal
value, given as a percentage.
Solar cell
An electronic component which generates electrical energy when irradiated with sunlight. Since the
voltage produced by a single solar cell is very small (approx. 0.5 V), several solar cells are
combined to form a solar module. The most common semiconductor material presently used for
solar cells is silicon, which is manufactured in different forms (monocrystalline, polycrystalline,
amorphous). In addition to vastly different mechanical variations, which are usually designed to
increase the level of efficiency, completely new materials are currently being tested (cadmium
telluride, cadmium indium sulphide, titanium dioxide and many others).
Solar energy
"Sun energy", this means energy from sunlight or other solar irradiation (heat and/or UV radiation).
Solar module
Electrical connection of several solar cells encapsulated in a housing to protect the sensitive cells
from mechanical stress and environmental influences.
Stand-alone grid system
An energy generation system which is completely independent of any external power sources.
String
Describes a group of solar modules electrically connected in series. A PV system usually consists of
a number of strings, which avoids excessive yield losses caused by variations in shadowing on
different modules.
String inverter
An inverter concept which avoids the disadvantages of the central inverter concept. The PV
generator is split into individual strings, each of which is connected to the external grid by means of
its own string inverter. This greatly simplifies installation and reduces the yield losses which can be
caused by manufacturing deviations or variations in shadowing on the solar modules.
Sub-Cluster (Extension Cluster)
Cluster in a multicluster system which is subordinate to the main cluster and is therefore not
responsible for the management of the entire system.
VRLA
Valve regulated lead acid battery: lead acid battery with semi-solid electrolyte or closed lead acid
battery. Examples of this type of battery are gel batteries and AGM batteries (Absorbent Glass
Mat).
210 SI2012_2224-TEN082311 Technical Description