Design Study for the European Underground Research Infrastructure related to Advanced Adiabatic Compressed Air Energy Storage

Thermal Energy Storage


  • Optimized design of a TES unit for the AA-CAES operating conditions to give high efficiency and low material cost.
  • Development of simplified storage models for AA-CAES unit design.
  • Evaluation of diverse materials for high-temperature sensible TES.

Preliminary Storage configuration

TES dimensions

  • Length 10m, diameter 6m, solids content 460 tons

Cavern dimensions

  • Length 260m, diameter 10m

Air flow

  • 1 kg/s

TES storage efficiency

  • Greater than 90%


Applicability of rocks, concrete, and ceramics as sensible thermal energy storage material

Temperature-dependent thermophysical properties were used to compare the different materials in a test scenario.

First results:

  • Ceramics show the best thermodynamic performance.
  • Concrete shows the worst thermodynamic performance.
  • Rocks show thermodynamic performance similar to ceramics with much lower costs.

Design & optimization of storage unit for proposed thermodynamic cycle and cavern

Design variables:

  • TES length
  • Cover insulation thickness
  • Particle diameter

Objective functions:

  • Material costs
  • Exergy efficiency


  • dimensions
  • and min. air outflow temperature

TES Design

  • Existing conventional methods are not applicable to provide required air-tightness of the TES because of the high temperature conditions.
  • Lining for the TES has to ensure sufficient thermal insulation to reduce the heat losses.
  • This can be achieved by use of multilayer lining: