Characterization of Near Isothermal Compression and Expansion for Energy Storage

As the global share of electricity generation from intermittent renewable energy sources increases, developing efficient and scalable electricity storage technologies becomes critical to modernizing the grid, matching the supply and demand, and raising the capacity factor of renewable generation. The Ground-Level Integrated Diverse Energy Storage (GLIDES) is an efficient energy storage technology invented at Oak Ridge National Laboratory (ORNL). GLIDES stores energy by compressing gas using a liquid piston in pressure vessels benefiting from employing hydraulic turbomachinery which are more efficient than gas turbomachinery. Therefore, GLIDES has higher round-trip efficiency (RTE) than Compressed Air Energy Storage (CAES). Since GLIDES employs pressure vessels, it is not geographically limited as CAES and pump storage hydro (PSH) are. Two proof-of-concept prototypes were design and built at ORNL with nominal capacity of 1 and 3 . GLIDES 2^nd generation prototype achieved 98.5% isothermal compression efficiency experimentally. A physics-based performance model was developed simulating the GLIDES behavior during operation and was validated using the experimental data. For cost reduction purposes, the first cost of GLIDES when employing steel vessels, carbon fiber vessels, pipe segments, and underground pressure reservoirs was modeled. The results of the cost model showed first cost as low as and could be achieved for a grid-scale GLIDES using depleted oil/gas reservoirs and high-pressure pipe segments, respectively. Employing the studies done on liquid piston compression and direct heat exchange with micron-sized sprayed droplets in GLIDES, a one of a kind near isothermal liquid compressor (IsoLiqComp), capable of compressing any refrigerant, is designed and developed at ORNL. A secondary physics-based performance model was developed to study the condensable gas behavior. Based on simulation results, 95% isothermal efficiency can be achieved. A 1^st generation IsoLiqComp prototype was built using a 0.005 compression chamber. The results of this research show GLIDES is a low-cost efficient energy storage technology competitive to conventional Lithium-ion and Lead acid batteries. Significant increase in compression efficiency in comparison to conventional compressors is achievable using IsoLiqComp. HVAC systems, natural gas transportation, and extraction systems (etc.) can highly benefit from employing IsoLiqComp and the studies performed in this research.