Supercritical CO2 Recirculation in Reservoirs for Continuous Storage and Production of Renewable Energy

Abstract

Over the past decades, many countries have started to place emphasis towards electricity production from renewable sources, such as solar and wind, to limit the amount of CO2 emissions in the atmosphere and reduce global warming. However, solar and wind energy are exclusively reliant on climate conditions; thus, secure and continuous power supply cannot be guaranteed. Therefore, maintaining reliable and continuous power supply calls for concepts and implementation of energy storage techniques. CO2 subsurface energy storage is one of the most innovative techniques that could be applied to solve drawbacks of traditional storage techniques such as scale limitation in both capacity and time, low efficiencies, environmental concerns, or high costs. In this paper, we reviewed and assessed the use of CO2 subsurface energy storage systems by looking at the thermodynamic cycles, machinery, and reservoir conditions. Moreover, a comprehensive study on multiphase flow in porous media has been conducted by looking at capillarity, relative permeability, mass balance, heat balance, thermal properties, and phase behavior. Different well configurations have been compared by performing injection and production simulations to conclude that the use of horizontal injection and production wells is preferred over other proposed well configurations for many reasons such as decreasing the amount of initial CO2 needed to develop and operate the reservoir, covering a large area of the reservoir, and increasing the system's capacity and efficiency. The findings show that CO2 subsurface energy storage system can operate if certain requirements exist: 1) availability of initial CO2 supply, 2) availability of the necessary equipment and solar, or wind, power plants, 3) safety of the targeted location, 4) two deep, clean reservoirs with high porosity and high permeability and 5) presence of a caprock. Ensuring the existence of requirements determined from this study will allow a safe, large (in terms of capacity and time), efficient, and cheap method to store and produce renewable energy continuously. In the foreseeable future, the world will inevitably depend on electricity production from renewable sources; therefore, more energy storage techniques have to be developed. CO2 subsurface energy storage systems have to be considered as they can contribute to reducing emissions and global warming, ensuring a secure and continuous power supply, and solving the drawbacks of traditional storage techniques. The outcomes of this paper will contribute to the growth and development of CO2 subsurface energy storage systems