Electricity generation process

An electricity generation process is disclosed. The process comprises injecting an aqueous feed stream into a salt formation to dissolve the salt contained therein, and then extracting a saline stream containing said dissolved salt from the salt formation. The process also comprises converting latent osmotic energy present in said saline stream into electricity by passage through an osmotic power unit comprising a semi-permeable membrane which permits the passage of water but not the passage of salts in which said saline stream is passed over one side of the semi-permeable membrane, a low salinity stream being passed over the other side of said membrane. The process also comprises using an output stream derived from the low salinity stream as the aqueous feed stream.