Old Coal Mines Could Store Grid Power, Study Shows
Researchers developed a working blueprint for converting abandoned coal mines into giant batteries that store compressed air and feed power back to the grid. The approach could unlock vast untapped capacity for renewable energy storage without building new infrastructure—a critical gap as utilities race to balance wind and solar.
Originaltitel: Compressed air energy storage in abandoned coal mine roadways: Potential assessment and grid coordination optimization
<p>Utilizing underground spaces of abandoned coal mines for compressed air energy storage (CAES) systems represents a feasible and promising option, yet its feasibility is highly dependent on the system's thermodynamic performance, sealing integrity, and coordination with the power grid. Taking the Datong No.1 Coal Mine in Chongqing as a case study, this study develops a thermodynamic model of CAES suitable for coal mine roadways and performs a comprehensive parameter sensitivity analysis. A quantitative evaluation framework for mine-based CAES is innovatively proposed, and the air tightness performance of storage roadways is investigated under various combinations of air storage pressure and lining permeability. Furthermore, a multi-objective coordinated dispatch model integrating mine-based CAES with the power grid is established, and an improved particle swarm optimization (PSO) algorithm is employed to solve the model. The thermodynamic analysis results show that system efficiency is improved by approximately 10.2% when the compressor isentropic efficiency is increased from 0.80 to 0.94. A more significant improvement of 14.3% is achieved by raising the heat-exchanger efficiency from 0.80 to 0.94. However, a fivefold increase in energy storage density(ESD) achieved by elevating the upper storage pressure limit from 6 to 15 MPa is accompanied by an 8% efficiency loss, revealing an inverse relationship between efficiency and ESD. After CAES retrofitting, the available roadway volume of the Datong No.1 Coal Mine reaches 458,000 m3, corresponding to a total storage capacity of 1374 MWh. Numerical simulations indicate that for the long-term operation of mine-based roadway CAES, the permeability of the sealing layer must be maintained below 1 × 10−20 m2. Grid-coordination results indicate that integrating roadway CAES reduces total electricity cost by 2.25% relative to the non-CAES case, yields peak-shaving/valley-filling revenue of $41,547, and increases renewable penetration from 51.4% to 54.1%, accompanied by absorbable capacity of installed renewable energy increases of 11.7%. Overall, the proposed assessment and dispatch framework jointly quantifies engineering feasibility, including capacity and leakage constraints, and system level value, thereby providing a transferable basis for deploying mine roadway CAES to support higher renewable energy integration.</p>