Estimating the performance ratio of solar PV plants is important because PR serves as a key metric in agreements between Engineering, Procurement, and Construction (EPC) companies and investors, playing a pivotal role in determining system performance. The performance ratio of a solar PV plant is defined as the ratio of energy produced to the expected energy yield. The formula for calculating PR is outlined by IEC 61724. Agreements often include penalties if the agreed-upon PR is not met, underscoring the significance of accurate PR estimation.
Is there any ambiguity in calculating PR, or are there no suitable tools?
There are different formulas and methodologies to calculate the PR of a solar PV plant; however, there is no ambiguity, as the formula and methodology to be adopted are agreed upon between the EPC/Solar Installer and the client well before the project starts. There are tools that are used to design and simulate the solar PV plant, based on which energy yield and PR are predicted.
Why does the challenge persist, and could it be overcome?
During the process of converting sunlight to electricity, the conversion chain includes many steps that introduce uncertainties:
- The specifications mentioned in the spec sheet file of the panel (PAN file), which are considered during the design phase, are based on laboratory tests conducted by the manufacturer. During these tests, error margins may be introduced.
- Soiling losses can be considered, but it remains uncertain how practical it is to assess soiling loss for an entire solar park based on a single soiling sensor.
- The accuracy of data transmission is crucial; inaccurate data can make it challenging to calculate the most precise PR.
- Conducting a sensitivity analysis is challenging, as such an analysis requires only one variable to change at a time. In a solar PV park, however, numerous variables change simultaneously, introducing uncertainties.
Estimating PR can certainly be improved by better weather models, though achieving 100% accuracy may still be challenging.
Author: Eshan Sharma I MSc. Sustainable Energy System Management I Renewable Energy Enthusiast