Wind speed increases could cause PV yield losses

A Spanish research group says air flux variations over different parts of solar plants could also lead to mismatch losses. Past. studies have only looked at the benefits of high wind speed on PV arrays, which enhances module cooling.

Image: University of Alcala, communications engineering, CC BY 4.0

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New research from Spain’s University of Alcala reveals that higher wind speeds can result in mismatch and power yield losses in solar power plants. In “Energy losses in photovoltaic generators due to wind patterns,” recently published in Communications Engineering, the researchers challenge the conventional belief that increased wind speed benefits ground-mounted PV plants by enhancing solar module cooling.

“In these previous cases, the interface module/air flux is small to appreciate a full airflow development in natural conditions,” the scientists said. “In big PV generators exposed to wind patterns, the module temperature depends on its position inside them, as the air flux affects how the module exchanges heat with it. This is the reason why the wind speed increase did not necessarily bring the best PV performance.”

The researchers conducted real-world measurements on a PV system situated at the Technical University of Madrid, consisting of 21 south-oriented modules, each with a 245 W output. They used a thermographic camera to measure transient temperatures resulting from slight wind fluctuations in a single cell. Additionally, temperature and voltage were recorded at various points on the PV system using resistance temperature detectors.

Their findings indicate that when the system faces headwinds, it experiences higher mismatch losses compared to winds coming from the rear. Specifically, daily energy loss with headwinds was 0.28%, while tailwinds reduced energy production by 0.21%. Under the same conditions but with lower wind speeds, headwinds resulted in a 0.25% mismatch loss, while tailwinds caused a 0.17% loss. On days with very low or no wind, the observed loss was 0.13%.

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“In other words, a decrease of the energy losses with the wind speed decrease,” the group said. “This apparent counter-intuitive argument follows the fluid mechanics theory, as the wind interaction with the PV generator induces air flux variations that modify the heat transfer from the modules to the air. The thermal behavior that leads to these losses is intrinsically linked with the airflow properties.”

The researchers also found that monthly mismatch losses follow the same patterns as daily losses.

“As the typical lifespan of a PV power plant may last some decades, this must represent an important uncertainty source to ensure the reliability of the PV plants,” they explained. “This suggests that the hitherto depreciated local wind patterns for energy estimations must be taken into account for a proper energy estimation during their lifespan.”

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