Solar Glossary
Short, plain-language explanations of the terms you meet in solar power, batteries and EV conversion.
Solar power plant (GES)
A system that converts sunlight into electricity with photovoltaic panels. In Turkish it is called GES; one built on a roof is a rooftop plant, one built on the ground is a ground-mounted plant.
Photovoltaics (PV)
The direct conversion of light into electric current in semiconductor cells. Solar panels are made of these cells and produce direct current (DC).
STC (Standard Test Conditions)
1000 W/m² irradiance, 25 °C cell temperature and an AM 1.5 light spectrum. The power and electrical values on a panel label are measured under these conditions; real output in the field varies with temperature and irradiance.
Wp / kWp (peak power)
Watt-peak: the peak power of a panel under standard test conditions (STC). 1 kWp = 1000 Wp; for example, ten 540 Wp panels make 5.4 kWp of installed capacity. System size is expressed in kWp.
kWh and kW
kWh (kilowatt-hour) is an amount of energy: a 1 kW appliance running for one hour uses 1 kWh. Electricity bills and battery capacity are given in kWh, while the power drawn at a given moment is given in kW.
Monocrystalline panel
A panel made with cells cut from single-crystal silicon. It is more efficient than polycrystalline, so the same area delivers more power. Most panels sold today are monocrystalline.
TOPCon cell
Tunnel Oxide Passivated Contact: a cell technology for N-type silicon that reduces losses with a thin oxide and polysilicon layer on the rear surface. It aims for higher efficiency and lower heat losses than PERC cells.
PERC cell
Passivated Emitter and Rear Cell: a widely used P-type cell technology that raises efficiency with a passivation layer on the rear of the cell.
Half-cut cells
A panel design in which cells are cut in half before being connected. Less current flows through each half, so resistive losses fall and partial shading affects output less.
Inverter
A device that converts the direct current (DC) produced by the panels into the 230 V alternating current (AC) used at home and on the grid. There are grid-tied, off-grid and hybrid types.
On-grid (grid-tied) system
A system that works connected to the grid: electricity is used in the building first and the surplus goes to the grid. For safety it shuts down automatically during a power cut.
Off-grid system
A system that is not connected to the grid: it generates and stores its own electricity with panels, a battery and an inverter. It is used in cabins, caravans, fields and places the grid does not reach.
Hybrid system
A system that is grid-connected but also uses a battery. It stores daytime output for the evening and, during an outage, keeps the loads chosen in the design running from the battery.
MPPT (maximum power point tracking)
A control method that continuously finds the voltage–current point at which the panel delivers the most power in the current light and temperature. It is built into charge controllers and inverters.
BOOST MPPT charge controller
An MPPT charge controller that boosts the panel voltage above the battery-pack voltage to charge it. It lets lower-voltage panels charge 24–72 V battery packs, such as electric-vehicle batteries.
LiFePO₄ (lithium iron phosphate) battery
A lithium battery with lithium iron phosphate chemistry. Its long cycle life, high usable capacity and thermal stability make it common in solar storage and electric vehicles.
Gel and AGM batteries
Maintenance-free types of lead-acid battery: the electrolyte is held in a gel (gel) or absorbed in glass fibre (AGM). They cost less up front, but deep discharges shorten their life and their usable capacity is more limited than lithium.
DoD (depth of discharge)
How much of a battery's capacity is used. For example, 80% DoD means 80% of the capacity has been drawn. The higher the DoD a battery allows, the larger its usable capacity.
BMS (battery management system)
An electronic circuit that monitors the voltage, current and temperature of lithium battery cells, protects against overcharge, over-discharge and short circuits, and balances the cells.
Cycle life
How many full charge–discharge cycles a battery can go through, usually counted until its capacity falls to a set percentage. The figure depends on depth of discharge and temperature and is stated in the product data sheet.
Net metering (mahsuplaşma)
Billing in which the electricity fed into the grid and the electricity drawn from it are offset against each other within the period set by regulation. Which period applies (for example monthly or hourly) depends on the connection type and the current rules in Türkiye.
Licence-exempt generation
A generation plant built without a generation licence, mainly to cover the owner's own consumption. Capacity limits, the application and the grid connection process are set by the relevant regulation and the distribution company.
Self-consumption
The share of solar electricity used in the building at the moment it is produced, instead of being fed into the grid. The higher the self-consumption rate, the greater the savings; appliances that run during the day and a battery raise it.
Degradation
The slow decline of a panel's efficiency over the years. Manufacturers state the annual loss rate and the power the panel must still deliver at the end of the warranty in the data sheet.
Specific yield (kWh/kWp)
The energy that 1 kWp of installed capacity produces in a year. It depends on the local sunshine and the direction and tilt of the panels; it is high in sunny regions such as Antalya and is the basis of the savings calculation.
Performance ratio (PR)
The ratio of a system's actual output to the energy it could theoretically produce under the same irradiance. It sums up temperature, cable, inverter and soiling losses in a single figure and shows the health of the system in monitoring.
MC4 connector
The standard locking male–female connector used for DC connections between panels and between a panel and a device. It must be crimped with the proper tool for a safe connection.
String
A group of panels connected in series. Voltages add up in series, so the number of panels in a string is chosen to fit the input voltage range of the inverter or charge controller.
Voc and Isc
Open-circuit voltage (Voc) and short-circuit current (Isc): the limit values of a panel under standard test conditions. When designing a string, Voc, which rises in cold weather, must not exceed the device's maximum input voltage.
Shading and row spacing
A shadow on one panel can affect the whole string it is connected to, not just that panel. In ground-mounted plants the row spacing is calculated from the sun angle at the winter solstice so that rows do not shade each other.
Payback period
The time it takes for the savings from the system to pay back the investment. It depends on consumption, the electricity price, the region and the system cost; the calculator estimates it with a long-term projection.
EPC (turnkey)
Engineering, Procurement, Construction: a turnkey project model in which one company takes on engineering, equipment supply and installation.
O&M (operation and maintenance)
Operation & Maintenance: monitoring, periodic inspection, cleaning and fault repair of the system after installation.
Hub motor
An electric motor built into the wheel hub, common on e-bikes, scooters and three-wheelers. The vehicle's battery voltage (for example 48, 60 or 72 V) must match the motor controller.
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