This study summarizes the 2018 Eastern Mediterranean solar irradiance figures on ground level and makes a preliminary estimate for 2019. Regional solar irradiance data is analyzed in order to estimate the normalized output of solar power facilities in the region, considering the strong link between the two variables. The average solar energy cumulative flux, measured at the IMS station in Bet Dagan in Israel's Central Coastal Plane during 2018, was 5,339 Wh/m2 per day, which is 4.0% higher than the 1965-2014 multi-year annual solar flux average. The anomaly is within the standard annual deviation of ±4.0% during the 1965-2014 period. 2019 is expected to show above average solar irradiance figures in the Eastern Mediterranean region, continuing the high-level solar irradiance trend - similar to the period of late 1960s and early 1970s or even exceeding it.
Bet Dagan is the longest operating Israel Meteorological Service (IMS) station which has been measuring solar energy flux on ground level since 1965. The station is thus very suitable for long-term analysis of ground level solar energy flux in the Eastern Mediterranean. Regional solar irradiance data is analyzed in order to estimate the normalized output of individual solar power facilities in the region, considering the strong link between the two variables. It should be emphasized that variance in solar flux on the ground level is mostly a result of regional weather and climate influenced by long-term trends in solar activity, planetary climatic shifts and more recently by anthropogenic causes; only to small degree variance in measured solar flux is a direct result of sun's solar output, which is relatively stable.
Figure 1. Solar irradiance measured at Bet Dagan in central Israel in monthly resolution during 2018 (orange) vs. the average for respective months obtained during 1965-2014 (blue).
The average solar energy cumulative flux, measured at the IMS station in Bet Dagan in Israel's Central Coastal Plane during 2018, was 5,339 Wh/m2 per day, which is 6.3% higher than the 1965-2014 multi-year annual solar flux average. The anomaly is within the standard annual deviation of ±4.0% during the 1965-2014 period. The preceding 2017 solar energy flux figure was 5,453 Wh/m2 per day, 6.3% higher than the multi-year flux average. In 2016, solar energy flux figure was 5,520 Wh/m2 per day, 7.6% higher than the multi-year flux average and the record highest measurement at Bet Dagan IMS station since it began operating since 1965. In 2015, the solar energy cumulative flux was at 5,269 Wh/m2 per day, which was 2.8% higher than the 1965-2014 multi-year average. The 2014 solar energy cumulative flux was at 5,399 Wh/m2 per day, as well higher than multi-year average.
Figure 2. Solar irradiance measured at Bet Dagan in central Israel in yearly resolution during 1965-2018 (blue) and estimate for 2019.
An estimate for 2019, based on the first nine months of the year, is 5,366±57 Wh/m2 per day, which is higher than multi-year average. Hence, 2019 is expected to show above average solar irradiance figures in the Eastern Mediterranean region, continuing the high-level solar irradiance trend - similar to the period of late 1960s and early 1970s or even exceeding it. Increased solar irradiance on ground level is driving increased performance figures for PV facilities in the region - a phenomenon which may continue for some time. Among possible factors to alter this projection is an unexpected change in solar activity or a powerful volcanic eruption in Equatorial regions at an intensity of VEI 5.0 or above.
