Automating Quality Control of Irradiance Data with a Comprehensive Analysis for Southern Africa

Abstract

A review of quality control for large irradiance datasets is applied as a case study for the Southern African Universities Radiometric Network (SAURAN) database. The quality control procedure is automated and applied to 24 stations from the database with a total of 848,189 hourly datapoints. From this, the individual station’s data quality is also analysed. The assessment validates the automated methodology without the need for a user-based review of the data. The SAURAN database can play a significant role in advancing solar and wind energy; however, the number of offline stations hinders this process. Data scarcity remains an obstacle to these goals, and therefore, recommendations are provided to address this. Recommendations regarding each site’s usability in time-series and discrete applications are made, which provides an overall indication of the SAURAN database’s irradiance measurement quality. Of the 24 measuring stations assessed, eight are recommended, 11 are recommended with cautious use, and five are recommended with extremely cautious use. These recommendations are based on multiple factors, such as whether a dataset has more than one full year of data or is missing minimal datapoints. Further, a study of the irradiance correlation between the stations was conducted. The results indicated groupings of different stations that showed highly correlated irradiance measurements and similar weather patterns. This is useful if a proposed renewable energy power plant, such as PV, falls within a cluster where the data from the SAURAN database can be used as a substitute if no data is available. SAURAN presents an opportunity for Southern Africa to increase its research outputs in solar and wind energy and lessen its dependency on fossil fuel-based energy production.

New Decomposition Models for Hourly Direct Normal Irradiance Estimations for Southern Africa

“…For each SAURAN station, a localised decomposition model is developed. A clustered decomposition model describes an area with similar irradiance patterns using the clustered areas discussed in [40]. Farmer and Rix first presented a two-cluster correlation map using the SAURAN database [48] and, by using this approach, this study formulated four clusters instead of two in Southern Africa, as shown in Figure 3a.…”

New Decomposition Models for Hourly Direct Normal Irradiance Estimations for Southern Africa

“…The methodology to develop a novel decomposition model is based on selected data from the automated quality control (QC) procedure proposed in [40] and addresses three geographical models:…”

“…Table 3 also shows each station's mean GHI, DNI, and DHI, determined after applying the QC procedure. 1 Daylight average, 2 Dataset size after quality control as in [40] and 0.175 ≤ K t ≤ 0.875.…”

“…For each SAURAN station, a localised decomposition model is developed. A clustered decomposition model describes an area with similar irradiance patterns using the clustered areas discussed in [40]. Ref.…”