Repurposing Inactive Oil and Gas Wells for Energy Storage: Maximizing the Potential via Optimal Drivetrain Control

In recent years, there is a growing emphasis on utilizing energy storage for improving the grid resilience to withstand and recover from disruptive events. At the same time, as renewable energy supply continues to grow, the application of gravity -based solutions such as pumped hydro dominate the commercial space, however, is challenged by the availability, scalability, and cost of co-locating solar and wind energy. Repurposing numerous idle and orphaned oil wells that are conveniently located closer to existing grid infrastructure offers a promising low-cost alternative. The successful implementation of such a gravity energy storage system however requires optimized operation and control of an electromechanical drivetrain system that helps minimize the levelized costs of storage and maximize efficiency and revenue. This paper specifically addresses this task through the optimization and control of a regenerative drive system that is coupled to an interior permanent magnet synchronous machine driving a 100N weight in a 300m well. A dynamic MATLAB/Simulink model is used to simulate the operation of the electric drivetrain system during storage and discharge operations. The results showed initial round-trip efficiency of 85.9% from the electrical system alone and outline the factors that are crucial for maximizing the efficiency.