Type Thermal Storage Research Articles

Thermocline Storage Filled with Structured Ceramics. Numerical Consistency of the Developed Numerical Model and First Observations

AbstractThe attraction of solar energy is greatly enhanced by the possibility of it being used during times of reduced or non-existent solar flux, such as weather induced intermittences or the darkness of the night. Therefore optimizing thermal storage for use in solar energy plants is crucial for the success of this sustainable energy source. Here we present a study of a structured bed filler dedicated to Thermocline type thermal storage, believed to outweigh the financial and thermal benefits of other systems currently in use such as packed bed Thermocline tanks. Several criterions such as Thermocline thickness and Thermocline centering are defined with the purpose of facilitating the assessment of the efficiency of the tank to complement the standard concepts of power output. A numerical model is developed that reduces to two dimensions the modeling of such a tank. The structure within the tank is designed to be built using simple bricks harboring rectangular channels through which the solar heat transfer and storage fluid will flow. The model is scrutinized and tested for physical robustness, and the results are presented in this paper. The consistency of the model is achieved within particular ranges for each physical variable.

Performance Estimation of Vertical Inflow Diffuser for Temperature-stratified Type Thermal Storage Tank by CFD Analysis - Effect of Tank Water Level and Step Change of Flow Rate on Temprature Distribution -

Performance Estimation of Vertical Inflow Diffuser for Temperature-stratified Type Thermal Storage Tank by CFD Analysis - Effect of Tank Water Level and Step Change of Flow Rate on Temprature Distribution -

Sliding flow method for exergetically efficient packed bed thermal storage

The feasibility of a thermal energy storage method is highly dependent on its exergetic efficiency. The two major components which cause exergy destruction in packed bed thermal energy storage methods are pressure drop and temperature dispersion. It is difficult to prevent exergy destruction with existing packed bed type thermal storage systems because the effect of most physical parameters on the pressure drop is opposite to that on the mixing or axial dispersion. We propose a new sliding flow strategy in which fluid inlet and outlet ports change as the temperature front in the bed moves. In this design the typical distance between two simultaneously active inlet and outlet ports will be approximately equal to twice the axial dispersion length. The computations presented in this paper show that the sliding flow method (SFM) is expected to perform significantly better than existing methods and will result in substantial reduction in exergy destruction. The major advantage of the SFM is its ability to decouple thermal behavior and pressure drop effects, thus reducing the design constraints.

Heat transfer analysis of encapsulated phase change materials

Solar energy is receiving a lot of attention recently since it is a clean, renewable, and sustainable energy. Solar energy is used for space heating, power generation and other applications. A major limitation however is that it is available for only about 2000 h a year in many places. Therefore it is critical to find ways to store solar thermal energy for the off hours. Sensible heat of material has been used for storing thermal energy but due to material properties this type of thermal storage has limitations. Using encapsulated phase change materials is potentially a better way to store thermal energy with the associated reversible heat transfer. The present work deals with certain aspects of storing solar thermal energy in high temperature phase change materials with melting points above 400 °C. The objective is the storage of large amounts of solar energy (∼600 MWh). Two kinds of encapsulated capsules are considered; zinc encapsulated in nickel and eutectic salt mixtures (57 mol% NaCl and 43 mol% MgCl2) in stainless steel encapsulation. Diffusion and phase change computations are reported here in the form of temperature profiles of the phase changing and encapsulated materials for spherical capsules. The time for heating and melting during charging (storage of thermal energy into capsulated phase change material) and the time for cooling and solidification during discharging (retrieval of thermal energy) are presented for both zinc–nickel and salt–stainless steel systems. As per expectations, the time for heat transfer is much shorter for liquid heat transfer media compared to those for gases. Moreover, the heat transfer times are shorter with smaller sizes of capsules.

H-36 連結完全混合槽型蓄熱槽への多槽連結温度成層化技術適用に関する研究 : その3.ディフューザ改良による蓄熱バランス向上

H-36 連結完全混合槽型蓄熱槽への多槽連結温度成層化技術適用に関する研究 : その3.ディフューザ改良による蓄熱バランス向上

Assessment of Energy-conserving, Environmental Load-reducing, and Cost-reducing Performance of the Combustion Type Thermal Storage CO2 Fertilization System in a Greenhouse

This study evaluated three types of combustion type CO2 fertilization systems: The thermal storage type (excess heat energy is stored and used for heating), the heat waste type (excess heat is discharged outdoors), and the diffusion type (excess heat is discharged indoors). We analyzed the validity, energy-conserving, environmental load-reducing, and cost-reducing characteristics of these types, and reached the following conclusions.1)The excess heat generated by combustion type CO2 fertilization accounted for several percentages of the daily cumulative solar irradiation during the intermediate period under the standard condition in this study (amount of CO2 fertilization,48 g (CO2) m-2d-1). The thermal storage type is expected to prevent the aggravation of the thermal/humidity environment in the greenhouse and decrease the efficiency of supplied CO2.2)Using the thermal storage type,a maximal energy conservation of 8% and a reduction in CO2 discharge can be expected in large greenhouses (annual energy consumption in the entire greenhouse, about 3 GWh) under the standard conditions of this study (summer/intermediate period ratio, 0.33; thermal storage/discharge efficiency, 0.8).3)The unit cost of CO2 fertilization using this thermal storage type was about 25 yen kg-1 (during depreciation) and about 12 yen kg-1 (after depreciation) under the standard conditions of this study (summer/intermediate period ratio, 0.33; price of unit quantity of heat, 5.5 yen kWh-1; thermal storage/discharge efficiency, 0.8). To reduce the unit cost of CO2fertilization, improvement in thermal storage/discharge efficiency, a decrease in fuel cost, and an increase in the number of days in operation during the intermediate period are necessary.

514 成層型蓄熱槽における多孔板の整流挙動(熱工学2,学術講演)

514 成層型蓄熱槽における多孔板の整流挙動(熱工学2,学術講演)

403 氷蓄熱式パッケージエアコンの省エネルギー性評価

403 氷蓄熱式パッケージエアコンの省エネルギー性評価

Effects of Ice Bridging Phenomena on Ice-making Characteristics of an Ice-on-coil Type Thermal Storage Apparatus

Effects of Ice Bridging Phenomena on Ice-making Characteristics of an Ice-on-coil Type Thermal Storage Apparatus

Simulation analysis of passive solar heated buildings—Preliminary results

Solar gains through windows, walls, modified walls, skylights, clerestory windows, and roof sections provide an opportunity to dramatically reduce the total heating energy requirements of a building. Many such passive solar heating elements are currently available to a designer presenting a large number of possible system designs. A computer simulation analysis has been employed to aid in the selection of components. The results indicate that a performance comparable to that of a conventional active solar heating system should be achievable in an optimized design passive solar heating system. The placement and type of thermal storage is crucial to good performance. Movable insulation of the window increases the performance. When used in conjunction with a conventional heating system, temperature variations in the building can be reduced to those normally experienced.

Thermal Stress and Heat Storage Capacity in Sphere Heated by Fluid Having Varying Temperature

This work is concerned with the thermal stress and the heat storage capacity in pebbles exposed to a fluid of which the temperature changes periodically. The industrial application of such a heated sphere can be seen in a heat exchanger of thermal-storage type used as one of the system components in power plant such as high temperature gas cooled reactor and MHD power generation. In this study theoretical analysis is performed for three different types of temperature variation in pebbles heated by fluid. The results of numerical analysis clarify the thermoelastic behaviour and heat storage capacity and it is concluded that the trapezoidal heating is the most suitable one of the three, in view of the magnitude of induced thermal stress and the efficiency of heat transfer.