A short- and long-term demand based analysis of a CO2 concentrated solar power system with backup heating

Abstract

Daily minute-based (i.e., short-term) and typical meteorological year (TMY) hourly-based (long-term) analyses are presented for a recompression cycle with direct CO2 heating in a parabolic collector field. The cycle is assisted by a backup heating unit, which is composed of a two-tank molten salt thermal storage and an auxiliary heating process representing, for example, a fossil fuel burner. The analyses also considered that the cycle is subjected to two distinct demand profiles, one that is constant throughout the day and another that varies hourly. The multitude of conditions modeled allowed the results to explore the effect of different solar irradiation profiles, seasonality and solar multiple factor. The analysis revealed that for short and long-term analysis the proper size of the solar collector field, here presented by the solar multiple, is strongly related to the demand profile as well as to the time frame considered within the analysis, i.e. short-term or TMY. The results also indicated that when the recompression cycle operates under same solar multiple factor with either a variable or a constant demand, the latter configuration is less dependent of auxiliary heating while the former presents higher performance values. Ultimately, the analysis reinforces the need for considering realistic inputs (e.g., irradiation, demand, etc.) when dealing with renewable-based power plants.