Session: 09-18-01: Innovations in Storage, Recovery and Upgrade of Thermal Energy

Paper Number: 166755

CFD Simulations Featuring Unsteady RANS/LES for Assessing Liquid Piston Compression Performance for Energy Storage 

In this study, numerical studies were performed to investigate thermal hydraulics behaviors of near-isothermal liquid piston compression, which is applied for the compressed air energy storage (CAES) technology. CAES is one of many Long Duration Energy Storage (LDES) playing an important role for a sustainable energy and a resilient power system.

As a cost-effective integration of variable renewable energy sources into the current power grid, LDES is defined as a technology storing energy in various forms, including chemical, thermal, mechanical, or electrochemical and these resources can dispatch energy in terms of electricity or heat for extended periods of time, ranging from several hours, to days, weeks, or seasons.

Compressed air energy storage (CAES) is one of the many LDES options that can store electrical energy in the form of potential energy (compressed air) and can be co-located with central power plants or distribution centers. In a CAES technology, the energy charging process occurs when a compressor is electrically powered to compress air (charging) to convert electrical to potential energy in a compression chamber. The discharging occurs when the stored energy is discharged by expanding pressurized air with a turboexpander generator to regenerate electricity.

Among the CAES technologies, a near-isothermal liquid piston compressor utilizing air and water as operating fluids offers a major advantage over traditional solid piston compressor which avoids gas leakage and reduces energy wastage due to friction, yielding an overall higher efficiency.

This study presents numerical studies of liquid piston compressor featuring the approach of filling the chamber from the bottom inlet with water to compress air. Numerical simulations were performed using the Unsteady Reynolds-Averaged Navier-Stokes (URANS) and Large-Eddy Simulation (LES) coupled with the multiphase Volume-of-Fluid (VOF) model to simulate the transient interface between water and air, as well as capture the heat and mass transfer within the volume of compression chamber. In the present work, the RANS k-ω turbulent model and LES WALE (Wall-Adapting Local-Eddy Viscosity) subgrid scale model featuring a novel form of the velocity gradient tensor in its formulation was applied because of its advantages over the Smagorinsky model. On the other hand, the VOF model is suitable for model flows involving immiscible fluids, fluid mixtures, free surfaces, and phase contact on numerical grids capable of resolving the interface between the phases.

In this effort, effects of boundary conditions applied to the CFD-VOF calculations such as no wall, a adiabatic wall, and a thick wall with a heat flux subscribed to the overall pressure and temperature as well as the transient evolutions of flow and heat transfer evolution within the compression chamber are investigated and discussed. In addition, the reverse process, i.e., expansion, will be studied. Different designs of compressor and operating conditions will be evaluated to determine optimum set of geometric and operating parameters that provides peak performance.

Results from this work will provide a better understanding to the entire cycle of compression and expansion in the liquid piston design and will be used to improve the overall system efficiency of CAES technology.

Presenting Author: Nithin Panicker Oak Ridge National Laboratory

Presenting Author Biography: Dr. Nithin Panicker is a staff member in the Energy Systems Integration and Modeling group at Oak Ridge National Laboratory. Nithin received his PhD (2017) in mechanical engineering at Iowa State University, and his MS (2011) in mechanical engineering at the University of Cincinnati. He is an expert in applying CFD technology to solve challenging industrial/academic problems encountered in energy and manufacturing applications. At ORNL, he leads several High-Performance Computing simulation projects funded through Department of Energy’s High-Performance Computing for Energy Innovation program and through Office of Nuclear Energy program, in collaboration with many industry partners: Alcoa USA, EPRI, Spar systems Inc., CCAM, Solid power inc etc.

Authors:

Nithin Panicker Oak Ridge National Laboratory
Thien Nguyen Oak Ridge National Laboratory
Steve Kowalski Oak Ridge National Laboratory