Abstract:

The typical meteorological year (TMY) is crucial for assessing solar energy resources, significantly impacting the scientific evaluation of regional solar resource assessments and the optimal design of photovoltaic power generation systems. These systems directly influence the technical and economic performance of solar energy utilization. With ongoing climate warming, key indicators of the climate system have shown rapid changes. Over the past 60 years, global surface solar radiation initially decreased and then increased. However, since the 1980s, approximately 25% of observation stations have recorded a continuous decline, highlighting significant temporal and spatial variations in surface solar radiation. Xinjiang, China, a region sensitive to global climate changes, has experienced significant shifts in temperature, precipitation, and other meteorological elements. This study analyzes global horizontal irradiations (GHI) data collected from eight stations in Xinjiang from 1961 to 2022, examining temporal and spatial variations. Additionally, using wind speed, temperature, humidity, and dew point temperature data, we employed the Sandia method to select the TMY for solar energy resource assessment. We compared the differences in GHI TMY selected with the Sandia method every 30 years (four standard climatological normals of 1961—1990, 1971—2000, 1981—2010 and 1991—2020). The findings indicate that while GHI in northern Xinjiang initially decreased and then increased, it continued to decline in southern and eastern Xinjiang from 1961 to 2022. Post-1990s, the rate of decline slowed. Seasonally, GHI reduction rates in autumn and winter were notably higher than that in spring and summer. The GHI values of TMY calculated with the Sandia method were close to the annual average, with a relative error within ±3%. As meteorological elements changed, the absolute error between TMY with Sandia and the annual average increased. Furthermore, monthly GHI exhibited considerable volatility, with fluctuations notably larger between 1981—2000 and 1991—2020 compared to earlier periods. In these four periods, the variability in typical months was less in northern Xinjiang than that in the south and east due to smaller interannual GHI variations. The highest monthly GHI values in TMY typically occurred from June to July, while the values from January to March were generally higher than those from October to December.

Key words: climate change, solar energy resources, typical year, Xinjiang