Compressed Air Energy Storage (CAES) Cavern Simulator

Cavern Mode

Compression Process

Compressor / turbine power 20 MW

Time acceleration ×60

Charging cavern…

Cavern State

Pressure

1.0 bar

Air temperature

20 °C

Energy stored

0.0 MWh

Round-trip eff.

–

Simulated time

0.0 h

Cavern fill

0 %

How it works

Compressed Air Energy Storage (CAES) stores grid electricity by using a compressor to pump air into a sealed underground cavern (a solution-mined salt dome, at Huntorf and McIntosh). To recover the energy, the pressurised air is released through a turbine that spins a generator. The cavern is treated as a fixed volume of ideal gas:

P·V = m·R·T           (ideal gas law, R = 287 J/(kg·K) for air)

Isothermal work/kg:   w = R·T₀·ln(P₂/P₁)
Adiabatic work/kg:    w = γ/(γ−1)·R·T₀·[(P₂/P₁)^((γ−1)/γ) − 1]
Adiabatic temperature: T₂ = T₀·(P₂/P₁)^((γ−1)/γ),   γ = 1.4

Adiabatic — a simple single-stage compressor with no cooling. All the compression work briefly turns into heat, so temperature spikes far above ambient; that heat then leaks into the surrounding rock while the cavern sits idle, and the pressure drops with it (isochoric cooling, P falls at constant volume) — energy is lost exactly the way real "diabatic" CAES plants lose it, which is why they burn natural gas in the turbine to reheat the air before expansion.
Isothermal — models a multi-stage compressor with intercooling that removes heat as fast as it's generated, so the air stays near ambient temperature. This needs less total work to reach the same pressure and loses far less energy while idle — the strategy pursued by modern "advanced adiabatic" (AA-CAES) designs that capture and reuse the heat instead of discarding it.
Round-trip efficiency is the ratio of electrical energy recovered on discharge to electrical energy spent charging. Real CAES plants sit around 40–70%; this model reproduces the same qualitative gap between the two compression strategies.

Compressed air (cavern) Hot (adiabatic heating)

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