Climate-regime cospectrum analysis: Shortwave solar irradiance for regionally spaced locales

Solar irradiance has both short-term (less than 12 hour) and long-term (seasonal) variations. Understanding these fluctuations is crucial for improving solar resource forecasting and evaluating co-production strategies for solar-fossil power technologies. Six USA sites are selected from the Integrated Surface Irradiance Study (ISIS) and Surface Radiation (SURFRAD) budget network. To assess the long-term variations, the data is analyzed in seasonal periods: winter, spring, summer, and fall. Power spectral density is used to analyze the short term and long term variations in DWS. The inter-site coherence and phase analysis allows geographic dispersion of the solar resource to be evaluated. Results indicate that understanding long-term periodic oscillations are useful to optimize the co-production of solar/fossil power. Seasonal analysis of short-term variations suggests that the ability of a regionally dispersed network of PV to dampen the intermittency of solar power production is dependent upon the climatic regime.