Performance indicators for technical analysis

1. Performance Ratio

Performance Ratio (PR) stated as a percentage (%), is the ratio of the actual amount of energy produced by a solar PV power plant to the energy produced by the same plant when operating continuously at standard test conditions (STC). In other words, PR describes the relationship between the actual and theoretical energy output of the solar PV plant.  It can be understood that the closer the PR value approaches towards 100%, the respective solar PV power plant is operating more efficiently.

PR = Actual PV plant output (kWh)) ÷ Estimated nominal PV plant output (kWh)# 

Where (#) is the Solar Irradiance (kWh/m2) on the PV Module  X  Active area of the installed PV module (m2) X efficiency of the PV module

PR is independent of PV power plant capacity and is typically evaluated on a monthly or yearly basis. It informs the user how energy-efficient and reliable the PV plant is, and the result is also described as a quality factor.

Depending on the geographical location and season, the PR value falls normally within the range 40% to 90%. For a well-designed system, the PR ratio range is from 75% to 90%[1].


How to calculate the solar power plant performance ratio?

Video copyright and property of Minutes 2 Energy (Youtube)

2. Capacity Utilization Factor (CUF)

CUF also known as the capacity factor is the ratio of the actual annual energy output from the PV power plant to the energy generated by the PV plant when it operates at its full rated power, i.e., 24 hours and 365 days a year. In other words, it is a measure of how much energy is produced by a plant compared with its maximum output.

CUF = Actual PV plant output per year (kWh) ÷  ( PV plant capacity in KW X 8760 hours per year )

The definition of this performance indicator shows that the expected value of CUF cannot be high because the actual PV plant capacity is limited by the number of sunshine hours.

How to calculate a Capacity utilisation factor?

Video copyright and property of  Gray Cells Energy – Business e-Learning & Training (Youtube)


3. System Efficiency

Efficiency is a measurement of how much of a given resource’s energy potential gets turned into electricity. In the case of PV power plants, the system efficiency is basically the ratio of the output energy of the PV plant to the energy of the incoming irradiation incident on the PV modules

System Efficiency=  Generated energy from the PV plant (kWh) ÷  Solar irradiation incident on the PV modules area in the same PV plant (kWh) 

The PV power plant efficiency depends majorly on the efficiency of PV modules which is in the range of 16% – 19% and inverter efficiency which is in the range of 96% – 98%, depending on the manufacturer and technology used. System efficiency can be useful when it is required to compare the different designs and makes of PV power plants.


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