In the Indian solar context, CUF is perhaps the most overused word when it comes to measuring a solar power plant performance. The interesting thing is, not many people outside India understand the CUF because most of them use a much better metric – Performance Ratio(PR). When we posted the CUF of solar plants in India available in the MNRE website, many readers outside India emailed us asking how CUF is calculated and how different it is from the globally accepted standard of Performance Ratio(PR) (Some discussions on the topic in Linkedin are available here and here).
CHROSIS, a Germany based consulting firm, has published this excellent whitepaper on the subject that gives some good insights on the subject.
Update: A concise version of the whitepaper in the form of a power point presentation can be viewed below.
Some of the highlights of the whitepaper are given below.
Performance Ratio (PR) of a plant for a period of time =Energy measured(kWh)/(Irradiance(kWh/m2) on the panel x Active area of PV module(m2) x PV module efficiency)
Capacity Utilisation Factor(CUF) =Energy measured (kWh) / (365*24*installed capacity of the plant).
So on one side, PR is a measure for the performance of a PV system taking into account environmental factors (temperature, irradiation, etc.) and on the other side is CUF that completely ignores all these factors and also the de-rating or degradation of the panels.
Some more factors that can also be important when comparing PR vs. CUF:
– PR will take into account the availability of the grid, CUF will not.
– PR will take into account the minimum level of irradiation needed to generate electrical energy, CUF will not.
– PR will take into account irradiation levels at a given period of time, CUF will not
PR can be used as a tool to compare different solar PV systems with each other – even if they are located at different locations since all environmental factors will be taken into account. Therefore only the design and the ability of the system to convert solar energy into electrical energy will be compared with each other.
Therefore we are not convinced that the CUF is a good tool to provide insights into a solar PV system.
The whitepaper gives a comprehensive overview of the factors that affect PR and how to monitor and control it. The whitepaper can be downloaded here.
(This blog is supported by Aspiration Cleantech Ventures)
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