A Review on the Performance Indicators and Influencing Factors for the Thermocline Thermal Energy Storage Systems

Abstract

Thermal energy storage (TES) system plays an essential role in the utilization and exploitation of renewable energy sources. Over the last two decades, single-tank thermocline technology has received much attention due to its high cost-effectiveness compared to the conventional two-tank storage systems. The present paper focuses on clarifying the performance indicators and the effects of different influencing factors for the thermocline TES systems. We collect the various performance indicators used in the existing literature, and classify them into three categories: (1) ones directly reflecting the quantity or quality of the stored thermal energy; (2) ones describing the thermal stratification level of the hot and cold regions; (3) ones characterizing the thermo-hydrodynamic features within the thermocline tanks. The detailed analyses on these three categories of indicators are conducted. Moreover, the relevant influencing factors, including injecting flow rate of heat transfer fluid, working temperature, flow distributor, and inlet/outlet location, are discussed systematically. The comprehensive summary, detailed analyses and comparison provided by this work will be an important reference for the future study of thermocline TES systems.

Numerical analysis of demolition waste‐based thermal energy storage system for concentrated solar power plants

“…Discharging efficiency (Equation 18) is the ratio of discharged energy to the amount of energy stored in packed-bed. 37,50 η…”

Assessment of Inlet Mixing During Charge and Discharge of a Large-Scale Water Pit Heat Storage

“…Water is used as the storage material, which means it will naturally stratify due to the density difference between hot and cold water [42]. It is important to note that inlet mixing caused by high inlet flow rates or large temperature differences between the incoming water and the water in the PTES may significantly contribute to the destruction of thermal stratification [43,44]. In this case, appropriate operating strategies should be selected to minimize mixing during the charge and discharge of the heat storage.…”

Impact of buoyant jet entrainment on the thermocline behavior in a single-medium thermal energy storage tank

“…In this regard, different shapes of flow distributor have been proposed and tested, including tubular distributors (e.g., [26,27]), baffle plates (e.g., [28,29]), radial plates (e.g., [30,31]), hemispherical diffuser [32], porous pipes (e.g., [20,33]), etc. A detailed state-of-the art survey on these flow distributors can be found in [34]. The main purpose is to counterbalance the strong inertia force of the inflowing jet by producing multi-branch streams, inversed flow or radial flow, thereby limiting the impact of thermal jet within a certain depth.…”