Solar photovoltaic power plant parameters


Performance Ratio


Energy Measured (KWH)
P.R= --------------------------------------------
Energy (KWH)


   Energy Modeled=Irradiance @ Location (Kwh/m2 * Cell Area(m2)*ᶯ
   ᶯ is the module efficiency
   Energy measured is the data reported from the plant after one year of operation
   All data is measured over one Year

Capacity Utilization Factor


(Energy Measured) (KWh)
C.U.F= --------------------------------------------
Installed Capacity(kW)*8760(hr)

The reletionship between the two is


C.U.F*installed Capacity(kW)*8760(hr)
P.R= ………………………………………………………………..
Irradiance @location (kWh/(m2))*ᶯ

The P.R is a measure of the performance of a PV plant at a given irradiation level
Important aspects of the P.R is that it only evaluates the plant performance against the energy available from the sun . That is, it automatically discounts night times, when the sun does not shine We shall understand why this is important when We look into the C.U.F formula.
The C.U.F is a measure of how well a plant is utilized. This is important because a PV plant is an asset with a limited life and the investor would like to exteact as much value from the plant as possible.
To sum up, the P.R is a very useful tool to compare PV plants across the world and it directly reflects on the quality of construction and maintenance The C.U.F on the other hand is very useful in comparing different technologies and is particularly important to an investor who would like to know which technology offers maximum value.

SCADA (supervisory control and data acquisition) is a type of industries control and data acquisition system. Industries control system are computer controlled system that monitor and control industrial processes that exist in the physical world. But the SCADA system in the solar PV power plant is basically a measurement and monitoring system.

Tilt Angle: The angle at which a photovoltaic array is set to face the sun relative to a horizontal position.The tilt angle can be set or adjusted to maximize seasonal or annualenergy collection.
Fixed Tilt Array: A photovoltaic array set in at a fixed with respect to horizontal.

Tracking Array: A photovoltaic (PV) array that follows the path of the sun to maximize the solar radiation incident on the PV surface. The two most common orientations are:(1) one axis where the array tracks the sun east to west; and axis tracking where the array points directly at the sun times. Tracking arrays use both the direct and duffuse sunlight. Two axis tracking arrays capture the maximum possible daily energy.

Solar radiation


Angle of Radiation: The angle that a ray of sun makes with a line perpendicular to the surface . For example, a surface that directly faces the sun has a solar angle of incidence of zero, but if the surface is parallel to the sun (for example, sunrise striking a horizontal rooftop), the angle of incidence is 900.

Solar Radiation-the electromagnetic radiation emitted by the sun.

Diffuse Radiation: Radiation received from the sun after reflection and scattering by the atmosphere and ground.

Direct Normal Radiation (DNI):Radiation received by direct solar rays. Measured by apyrheliameter with a solar aperture of 5.70 to transcribe the solar disc.

Direct Insolation : sun light falling directly upon a collector. Opposite insolation.

Global Horizontal Insolation: Also Called Global Horizontal irradiance or total solar radiation is the sum of Direct Normal Irradiance (DNI), Diffuse Horizontal irradiance (DHI), and ground-reflected radiation; however, because ground reflected radiation is usually insignificantcompared to direct and diffuse, for all practical purposes global radiation is said to be the sum of diffuse radiation only:

Full sun: The amount of power density in sunlight received at the earth`s surface at noon on a clear day (about 1,000 Watts/square ,meter).

Peak Sun Hours: The equivalent number of hours per day when solar irradiance averages 1,000 w/m2. For example, six peak sun hours means that the energy received during total Day light hours equals the energy that would have the received had the irradiance for six hours been 1,000w/m2.

Pyranometer: An instrument used for measuring global solar irradiance.

Pyranometer: An instrument used for measuring direct beam solar irradiance. Uses an Aperture of 5.70 to transcribe the solar disc.

PV Module

Crystalline Silicon: A type of photovoltaic Cell made a Slice of single-crystal Silicon orpolycrystalline silion. Modules made out of single crystal cells are known as mono crystalline modules and the ones made out of poly crystalline silion cells are known as poly crystalline modules.

Thin Film Photovoltaic Module: A Photovoltaic modules constructed with sequential layers of thin film semiconductor materials.

Amorphous Silicon: A thin-film, Silicon photovoltaic cell having no crystalline structure. Manufacyured by depositing layers of doped silicon on a substrate.

Cadmium Telluride(CdTe): A thin-film photovoltaic modules with a mix of Cadmium and Telluride material..

Copper Indium DIselenide (CulnSe2 or Cis): A polycrystalline thin-film photovoltaic material (Some Times incorporating gallium (CIGS) and/or sulphur).

BIPV (Building-integrated Photovoltaic): A term for the design and integration of photovoltaic (PV) technology into the building envelope, typically replacing conventional building materials. This integration may be in vertical facdes, replacing view glass spandrel glass, or other façade material; into semitransparent skylight system; into roofing system, replacing traditioal roofing material; into shading "eyebrows" over window; or other building envelope systems.

Peak Watt: A Unit used to rate the performance of solar cells, modules, or arrays; the maximum nominal output of a photovoltaic devices, in watts (Wp) under standardized testconditions, usually 1,000 watts per square meter of sun light with other conditions, such as temoerature specified.

Photovoltaic (PV) Conversion Efficiency: The ratio of the electric power produced by aphotovoltiac device to the power of the sun light incident in the device.

Maximum Power Point (MPP): The Point on the current-voltage (I-V) curve of a moduleunder illumination, where the product of current and voltage is maximum. For a typicalsilion cell, this is at about 0.5 volts.

Power Conditioning Unit

Power Conditioning Equipment: Electrical equipment or power electronics, used to convert power from a photovoltaic array into a form suitable for subsequent use a collective term for inverter, converter, battery charge regulator and blocking diode.

Charge Controller: An electronic device that controls the charge input to the storing device (usually a battery) from the solar PV array.

DC to DC Converter: Electronic circuit to convert direct current voltages (e.g. photovoltaic module voltage) into other levels (e.g. load voltage). Can be part of a maximum power point tracker.

Maximum Power Point Tracker (MPPT): Means of a power conditioning unit that automatically operates the photovoltaic generator at its maximum power point under all conditions.

Maximum Power Tracking: Operating a photovoltaic array at the peak power point of the array's IV curve where maximum power is obtained also called peak power tracking.

Inverter: An electrical/electronic device that converts direct current electricity to alternating current either for stand-alone systems or to supply power to an electricity grid.

Grid Tied Inverter: Inverter that is tied to the utility grid and works in synchronization with the grid frequency and AC power.

Off Grid Inverter : A stand alone inverter that works on DC input from solar PV and or storage battery and gives out AC power.

Grid Interactive Inverter: Works as grid tied inverter when utility grid in available and as standalone inverter when grid power is not available.