Experimental investigation of the impact of fluid distribution on thermocline storage performance

Abstract

The influence of fluid distribution on packed bed thermocline storage is studied experimentally on a 107 kWh prototype-scale setup. Three distributors are placed at the top of the tank, comparing uniform, central and peripheral geometries. A reference case is first considered and consists in a charge between 100 °C and 140 °C with an interstitial fluid velocity of 1.25 mm·s−1. Local analysis reveals a short-term influence of the distributor at the top of the packed bed. Radial temperature is most homogeneous when using uniform distribution, then central, then peripheral. However, the packed bed quickly homogenises radial temperature: the differences observed between distributors are erased in less than 6% of the total tank height. As a consequence, the longitudinal temperature profiles are unaffected by the distributor and the same utilisation rate of 81% is obtained for the three geometries. The coupling between fluid distribution and velocity is then studied: five charges are performed at velocities varying between 0.5 mm·s−1 and 1.5 mm·s−1 for each distributor. The influence of velocity is visible over the range studied: the utilisation rate decreases by about 2% due to advection, in agreement with numerical simulations. Fluid distribution, on the other hand, has no influence on global storage performance, showing the robustness of packed bed thermocline systems.