  Compressed air energy storage is suitable for large-scale electrical energy
storage, which is important for integrating renewable energy sources into
electric power systems. A typical compressed air energy storage plant consists
of compressors, expanders, caverns, and a motor/generator set. Current cavern
models used for compressed air energy storage are either accurate but highly
nonlinear or linear but inaccurate. The application of highly nonlinear cavern
models in power system optimization problems renders them computationally
challenging to solve. In this regard, an accurate bilinear cavern model for
compressed air energy storage is proposed in this paper. The charging and
discharging processes in a cavern are divided into several real/virtual states.
The first law of thermodynamics and ideal gas law are then utilized to derive a
cavern model, i.e., a model for the variation of temperature and pressure in
these processes. Thereafter, the heat transfer between the air in the cavern
and the cavern wall is considered and integrated into the cavern model. By
subsequently eliminating several negligible terms, the cavern model reduces to
a bilinear model. The accuracy of the bilinear cavern model is verified via
comparison with both an accurate nonlinear model and two sets of field-measured
data. The bilinear cavern model can be easily linearized and is then suitable
for integration into optimization problems considering compressed air energy
storage. This is verified via comparatively solving a self-scheduling problem
of compressed air energy storage using different cavern models.
