Investigating the impacts of spatial-temporal variation features of air density on assessing wind power generation and its fluctuation in China

Air density plays an important role in assessing wind resource. Air density significantly fluctuates both spatially and temporally. But literature typically used standard air density or local annual average air density to assess wind resource. The present study investigates the estimation errors of the potential and fluctuation of wind resource caused by neglecting the spatial-temporal variation features of air density in China. The air density at 100 m height is accurately calculated by using air temperature, pressure, and humidity. The spatial-temporal variation features of air density are firstly analyzed. Then the wind power generation is modeled based on a 1.5 MW wind turbine model by using the actual air density, standard air density rho(st), and local annual average air density rho(site), respectively. Using rho(st) overestimates the annual wind energy production (AEP) in 93.6% of the study area. Humidity significantly affects AEP in central and southern China areas. In more than 75% of the study area, the winter to summer differences in AEP are underestimated, but the intra-day peak-valley differences and fluctuation rate of wind power are overestimated. Using rho(site) significantly reduces the estimation error in AEP. But AEP is still overestimated (0-8.6%) in summer and underestimated (0-11.2%) in winter. Except for southwest China, it is hard to reduce the estimation errors of winter to summer differences in AEP by using rho(site). Using rho(site) distinctly reduces the estimation errors of intra-day peak-valley differences and fluctuation rate of wind power, but these estimation errors cannot be ignored as well. The impacts of air density on assessing wind resource are almost independent of the wind turbine types.