The Lattice Boltzmann Method (LBM) was used for simulation of a gas flow and conjugate heat transfer in fixed packed beds with solid particles inside. D2Q9 version of the Factorized Central Moment (FCMLBM) is used for a gas flow computation. Heat transfer in the bed is described by second distribution function set and multiple relaxation time lattice Boltzmann method (DDF MRT LBM) is used. Numerical solver is implemented using NVIDIA CUDA framework and comparison of performance on different GPUs is presented as well. Validation of the code is done using experimentally measured values of temperatures in fixed rock bed in a high-temperature thermal storage experiment. Next, the rate of heat transfer in a large scale fixed bed is numerically investigated, together with description of the bed’s thermal characteristics for two different mass flow rates of hot air.