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Accurate estimation of energy storage capacity of a cavern with regard to a defined storage volume and type is the very first step in planning and engineering a Compressed Air Energy Storage (CAES) plant. The challenges in obtaining the reliable estimation present in the complexity associated with the thermodynamics of the internal air compression and expansion processes and the coupled heat transfer with surroundings. This tool simulates the time-dependent variations of air pressure, temperature, volume and mass flow rate during the CAES system operation, and estimates the maximum exergy (electricity) storage capacity with a known cavern volume with different operation and heat transfer conditions.

The figures illustrate two of the large-scale CAES systems: conventional diabetic CAES (D-CAES) and adiabatic CAES (A-CAES). Through the stages of charging, storing and discharging, the two CAES systems are operated. Rather than using fossil fuels in the conventional D-CAES cycle, A-CAES uses thermal energy storage to store the heat of compression and heat up the compressed air during the discharging period.

Two air storage modes, uncompensated isochoric storage and compensated isobaric storage, are shown in (a) and (b). In the mode of uncompensated isochoric air storage, air pressure varies between the minimum pressure and the maximum pressure and air volume is unchanged. Conversely, air volume varies in the compensated isobaric air storage and air pressure is maintained unchanged.

A validation of the calculation is plotted. The mass flow rate in a 24-h window is used as input variables for the simulation. The experimental inlet air temperature at the three periods of non-zero inflow ratesare 50.96 , 45.95 , and 49.08 , respectively. The simulated pressure and temperature variations are plotted in (a) and (b) respectively. According to the results, simulated pressure and temperature variations follow closely to the test data of the trial operation of Huntorf CAES plant.


Proposed range:1-500

Input of mass flow

Proposed range:273-353

Temprature of input mass

Proposed range:0-300

Output of mass flow

Proposed range:273-353

Initial air temprature in cavern

Proposed range:1000000-10000000

Throttling pressure

Proposed range:10-200000

Area of cavern surface area

Proposed range:1000000-20000000

Cavern maximum pressure

Proposed range:1-200

Cavern heat transfer coefficient

Proposed range:1000000-10000000

Initial cavern air pressure

Proposed range:20-1000000

Cavern volume

Proposed range:10-100000000

Initial air mass in cavern
Energy in adiabatic cavern
Energy in isothermal cavern