A First Order Thermodynamic and Economic Analysis for Integrating Thermal and Compressed Air Energy Storage for a Dispatchable Wind and Solar Powered System

Wind and solar technologies have experienced rapid market growth recently as a result of the growing interest for implementation of renewable energy. However, the intermittency of wind and solar power is a major obstacle to their broader use. The additional risks of unexpected interruptions and mismatch with demand have hindered the expansion of these two primary renewable resources. The goal of this research is to analyze an integrated energy system that includes a novel configuration of wind and solar coupled with two storage methods to make both wind and solar sources dispatchable during peak demand, thereby enabling their broader use. The proposed system utilizes compressed air energy storage (CAES) that is driven from wind energy and thermal storage supplied by concentrated solar thermal power in order to achieve this desired dispatchability. While current CAES facilities use off peak electricity to power their compressors, this system uses power from wind turbines to compress air to high pressure for storage. Also, rather than using natural gas for heating of the compressed air before its expansion through a turbine, which it typical for conventional systems, the system described in this paper replaces the use of natural gas with solar thermal energy and thermal storage. Through a thermodynamic and a levelised lifetime cost analysis we have been able to develop estimates of the power system performance and the cost of energy for this integrated wind-solar-storage system. What we found is that the combination of these components resulted in an efficiency of over 50% for the main power components. We also estimated that the overall system is more expensive per unit of electricity generated than two of the current technologies employed today, namely coal and nuclear, but cheaper than natural gas peaking units. However, this economic analysis, though accurate with regard to the technologies chosen, will not be complete until cost values can be placed on some of the externalities associated with power generation such as fuel cost volatility, national security, and emissions.