Reuse of construction shafts in compressed air energy storage systems

A method of reusing at least a first construction shaft utilized for construction of a hydrostatically compressed air energy storage system during operation of the hydrostatically compressed air energy storage system, the method comprising:

• step a) conveying at least a first construction apparatus into or out of an underground accumulator through the first construction shaft when constructing the accumulator;
• step b) removing the first construction apparatus from the accumulator and the first construction shaft;
• step c) converting the first construction shaft to become an operating component of the hydrostatically compressed air energy storage system by fluidly connecting the first construction shaft to form part of at least one of:
• i. an air flow path fluidly connecting a gas compressor/expander subsystem with a layer of compressed gas within the accumulator;
• ii. a compensation liquid flow path fluidly connecting a compensation liquid reservoir and a layer of compensation liquid within the accumulator;
• and
• iii. a thermal fluid flow path fluidly connecting a thermal source reservoir and a thermal storage reservoir;
• the method further comprising operating the hydrostatically compressed air energy storage system in at least one of:
• a charging mode in which the gas compressor/expander subsystem convey compressed air at a storage pressure into the layer of compressed air which displaces a corresponding amount of compensation liquid from the layer of compensation liquid out of the accumulator via the compensation liquid flow path thereby maintaining the layer of compressed air at substantially the storage pressure during the charging mode;
• a discharging mode in which air from the layer of compressed air exits the accumulator and drives the gas compressor/expander subsystem and a corresponding amount of compensation liquid is re-introduced into the layer of compensation liquid within the accumulator thereby maintaining the layer of compressed air at substantially the storage pressure during the discharging mode;
• and
• a storage mode in which there is no flow of the compressed air or compensation liquid and the layer of compressed air and the layer of compensation liquid are retained within the accumulator at substantially the storage pressure.