Solid Heat Storage Research Articles

Thermal analysis and design of solid energy storage systems using a modified lumped capacitance method

Solid sensible heat storage is an attractive option for high-temperature storage applications in terms of the investment and maintenance costs. Typical solid thermal energy storage systems use a heat transfer fluid to deposit and extract heat as the fluid flows through a tubular heat exchanger embedded in the solid storage material. A one-dimensional unsteady model of the heat transfer and energy storage in a solid heat storage module was developed using a modified lumped capacitance method which is valid for large Biot numbers with the introduction of an effective heat transfer coefficient. Experiments using water as the heat transfer fluid and concrete as the storage material were used to validate the model. The model was used to analyze a cylindrical energy storage unit to study the energy storage in the storage module and optimize the design.

Optimal Design of High-Temperature Thermal Energy Store Filled with Ceramic Balls

The momentary amount of the available solar energy and the demand usually are not equal during the usage of solar energy for heating and electric power supply. So it is necessary to store the heat energy. This article shows optimal design of a new construction, sensible heat store filled with solid heat storage material. The planned heat store has cascade system formed a spiral flow-path layout. This is a conceptual model, worked out in case of packed bed with ceramic balls. The aim of the special layout is to realize better overall efficiency than regular sensible heat stores have. The new construction would like to get higher overall efficiency by long flow-way, powerful thermal stratification and spiral flow-path layout which can ensure lower heat loss. The article shows the calculation method of the simulation of the charge and discharge and the calculation method of the overall efficiency using the results of the simulations. The geometric sizes and operating parameters of the thermal energy store with the best overall efficiency were calculated using genetic algorithm (GA). The results of the calculation tasks show that a thermal energy store with long flow-way, with cascade system formed spiral flow-path layout has higher overall efficiency than an one-duct, short flow-way thermal energy store which has equal mass of solid heat storage material as the long flow-way one, mentioned before.

440 太陽熱利用暖房システムにおける集熱器と蓄熱槽に関する研究

The characteristics of thermal behavior of solid heat storage tank (Rock Bed) combined with air heating type of solar collector were investigated theoretically by applying the heat transfer model considering for rock-air convection heat transfer, thermal conduction as a void parameter, and heat loss to the environment, and experimentally by cylindrical rock-beds connecting with the ref-lamp simulation system of the solar collector. The solar collector characteristics is the most significant parameter for this system, so the heat absorbed efficiency η_c is based on the simultaneous solutions for the energy balancing equation between the wall and glass elements coupled with the energy equation of heated air in the collector channel. The storage energy equations were discretized by the control volume method and solved numerically by Guess-Seidel iteration full implicit technique by using the above derived collector performance η_c depending on the temperature difference in the rock and surroundings. The behaviors of storage performance have been discussed for various parameter under the condition of (1) the air flow rate per unit of face area, (2) solar incident intensity q_inc, and (3) storage and discharge air flow mode.

416 空気加熱式太陽光集熱器を熱源とする固体蓄熱槽に関する研究

416 空気加熱式太陽光集熱器を熱源とする固体蓄熱槽に関する研究

807 空気加熱式太陽光集熱器を熱源とする岩床式固体蓄熱槽に関する研究

807 空気加熱式太陽光集熱器を熱源とする岩床式固体蓄熱槽に関する研究

Heat transferential study on a heat storage container with phase change material

This paper presents heat transfer characteristics of a heat storage container utilizing latent heat storage material, calcium chloride hexahydrate (melting point 28°C). The heat storage container is consisted of a vertical cylindrical pipe with a vertical heat transfer tube at the center and the latent heat storage material containing into the cylindrical pipe. The heat release and heat transfer characteristics during the solidification of the latent heat storage material are experimentally studied. The following results are obtained. The relation between the time and total heat flow rate, that is, the heat release characteristics have the following three stages: (1) the stage of sensible heat release from liquid heat storage material, (2) the latent heat release stage, (3) the stage of sensible heat release from solid heat storage material. The actually measured values of thermal resistance show a tendency similar to that of the theoretical values, but their absolute values are smaller than those of theoretical values by about 40%. This is because the solidified crystals of heat storage material do not grow in circular shape concentric with the heat transfer pipe but grow in dendritical shape, and dendritical crystallized portions function as fins.