Optimization of an Integrated Energy Storage Scheme for a Dispatchable Wind Powered Energy System

Abstract

The intermittency of wind and solar power and the mismatch between when they are available and when demand is high have hindered the expansion of these two primary renewable resources. The goal of this research is to analyze an integrated energy system (named DSWiSS for dispatchable solar wind storage system) that includes a novel configuration of wind and solar together with compressed air energy storage (CAES) that is driven from excess nighttime wind energy and thermal storage energized by concentrated solar power in order to make these sources dispatchable during peak demand. This paper builds off prior published work for the DSWiSS configuration with an analysis of actual historical meteorological data for West Texas solar insolation, generation output data for a wind farm in West Texas, recorded electricity demand data of the Electric Reliability Council of Texas (ERCOT) grid, and historical temperature data for West Texas to assess system performance. In this analysis, a comparison approach was taken by optimizing both the operation of a conventional CAES facility that does not incorporate wind and solar directly and the operation of a CAES facility directly coupled to a wind farm, which will be referred to as CAES-plus-Wind. Dynamic parameters for wind generation, electricity price, and ambient temperature were utilized in the optimization models. Through the use of optimization models and the incorporation of a thermodynamic model of the CAES equipment, we found that in each season the electricity price is a key factor in determining whether the facility stores or generates energy. For the CAES equipment, the summer season yields the highest profits primarily because of the larger spread between highest and lowest daily price for electricity. Even though profits for the CAES equipment in the other seasons are small or negative, it appears that the value of the facility in the summer is greater than the costs in the other three seasons combined. Additionally, we found that the value of directly coupling the CAES facility to a wind farm versus operating the two entities separately yielded no significant increase in profits. Lastly, this analysis did not attempt to quantify the possible increase in wind farm generation output that could result from reduced curtailment with the use of an energy storage system such as is proposed in this paper. This additional source of revenue could be a major contributor to the economic justification for large scale energy storage.