Intra-hour classification of direct normal irradiance for two sites in Spain and India

Kurzfassung

The magnitude of the direct normal irradiance (DNI) depends on seasonal differences due to the sun-earth geometry, and atmospheric extinction processes caused by aerosols and clouds. The most relevant source for intra-hour variability in the DNI are clouds. Suitable sites for concentrating solar power (CSP) plants have an annual average DNI above approx. 2000 kWh/m². Not only the average DNI but also the temporal and spatial DNI variability on the field has a considerable impact on the dispatched electricity [1]. A classification method based on eight distinct variability classes for 1 minute resolved DNI on an hourly basis is introduced by [2]. In this work, the approach presented by [2] is adapted for an intra-hour application, which is more suitable for CSP applications. Here, we discuss the impact of the considered time window on the classification. Furthermore, the impact of the spatial solar field DNI on the variability classification was studied, using spatially resolved DNI maps of a camera based nowcasting system [3].Moreover, we present the results of a variability classification study, including data of a complete year (2017) for a NETRA facility near New Delhi and the Plataforma Solar de Almería (PSA)