Performance Ratio as a Metric in Swedish PV Park Procurements

Sammanfattning: When procuring a solar PV park in Sweden there are many stakeholders involved. As of today, the metric called performance ratio (PR) is often used to guarantee the park’s performance. Nonetheless, comprehending and evaluating PR can be challenging due to its inherent complexity. This study highlights favorable and unfavorable aspects of using PR as a performance metric in solar park procurements in Sweden. The study analyzes the correlation between PR, yield, and revenue, indicating a weak correlation between PR and yield. Findings show that lower values of PR often correspond to a higher yield, this suggests that PR is not a reliable metric for assessing the performance of a solar park. In addition, it may lead to negative implications for stakeholders involved in both procurement and operation of a solar park Relying solely on PR can potentially result in financial losses.  Furthermore, a sensitivity analysis was conducted with a focus on inverter loss and DC/AC ratio. Results illustrate that PR and inverter loss are strongly correlated for a park with a high DC/AC ratio, and they have a weaker correlation for a park with low a DC/AC ratio. This is due to increased inverter loss resulting from clipping losses in the system. The study suggests that a desirable DC/AC ratio of 1,15 maximizes yield and profit. In conclusion, while PR exhibits lower variation and can entail lower risk for Engineering, Procurement and Construction (EPC) companies, it is not always a reliable metric for assessing park performance. The weak correlation between PR and yield, as well as revenue, has implications for developers and investors. The study suggests that a lower DC/AC ratio may reduce the risk for EPCs guaranteeing PR, but decisions based solely on PR may not guarantee the highest revenue for investors and developers.