•Transient thermal behavior of sensible heat storage tank SHS using molten salts and natural materials are obtained.•Optimization of SHS tanks are carried out.•Optimal design of SHS tank using ...natural materials can effectively replace using molten salt.•Using natural materials can eliminate extra cost associated with freeze protection, no pressurizing problem, no corrosion.
This paper presents numerical investigation of transient behavior and thermal storage capability of a sensible heat storage (SHS) unit designed for storing heat in the temperature range of 523–673 K. The objective of this study is to assess the potential of using two candidate materials as energy storage media found in Jordan. The thermal performance of using these materials in SHS tank is compared against concrete bed. A heat storage unit of cylindrical configuration with embedded charging tubes has been designed. To investigate their heat storage characteristics, a finite element based 3-D mathematical model has been developed using COMSOL Multiphysics 5.1. Numerically predicted results match closely with the data reported in the literature. Performances of the thermal storage bed of capacity of 136.7 MW in 3 h (including charging time, energy storage rate, charging energy efficiency) have been evaluated for the selected three storage materials. In order to optimize the design of energy storage tank, parametric studies are carried out by varying the number of the charging tubes, diameter of charging tubes, fins effectiveness, and storage bed diameter to its height. Simulations results showed that overall thermal performance of these materials using optimal design are satisfactory considering the problems associated with molten salt and concrete bed. More specifically, Dead Sea salt, concrete bed and Basalt rocks are more economically attractive relative to molten salt plant because they eliminate the extra cost associated with freeze protection, no pressurizing problem, no corrosion. Finally, natural stones can operate at higher temperature and do not suffer from cracking due to cyclic charging and discharging.
As an organic phase change material (PCM), paraffin wax (PW) has the problem of low thermal conductivity. It has been applied in the heat storage engineering. To improve the thermal performance of ...paraffin wax adopted in heat storage, it was mixed with expanded graphite (EG) via melt-blending method. The EG/PW was compressed into a shape-stabilized phase change material (SSPCM). The DSC curve was measured and the relationship between pressure and density of the SSPCM was tested. The SSPCM was vacuum encapsulated in aluminum bags and placed in a packed bed heat storage system to measure the thermal storage properties. The results showed that the thermal conductivity of the SSPCM was 7.06 W/(m °C), and the maximum density of the SSPCM was 1.07 g/cm 3. The average thermal efficiency of the heat storage system was 95.3%. The number of heat storage units was positively correlated with the heat release power. This study explored the feasibility of a simplified heat storage system.
•The energy performance and applicability of tube composite panel (TCP) investigated.•Based on the CFD results, a real-scale experimental plant of TCP was constructed.•The insulation performance ...differed depending on the TCP installation location.•An external wall reinforcement system with insulation performance was realized.
In South Korea, more than 300,000 buildings are evaluated as remodeling targets. These old buildings consume higher energy per unit area. Moreover, most of them are masonry structures, are vulnerable to earthquakes and can suffer significant damage. Therefore, textile and capillary tube composite panels (TCPs) are used to improve energy and seismic performance of old masonry buildings. In this study, the applicability of TCP to an actual building was confirmed using computational fluid dynamic (CFD). Based on the CFD analysis results, a real-scale experimental plant was constructed. To establish a sustainable method of using TCP, a photovoltaic-thermal (PVT) module that uses solar energy was combined. The applicability of TCPs using the PVT module was reviewed by performing a real-scale experiment. The PVT system could supply hot water at up to 27.6 °C to the TCP in winter. The thermal insulation performance improved with increasing supply water temperature. Especially, in the case of TCP installed indoors, heat could be transferred indoor more effectively than in the case with the TCP installed outdoors.
The paper illustrates the status quo of a research project for the development of a control system enabling CHP units for a demand-oriented electricity production by an intelligent management of the ...heat storage tank. Thereby the focus of the project is twofold. One is the compensation of the fluctuating power production by the renewable energies solar and wind. Secondly, a reduction of the load on the power grid is intended by a better match of local electricity demand and production.
In detail, the general control strategy is outlined, the method utilized for forecasting heat and electricity demand is illustrated as well as a correlation method for the temperature distribution in the heat storage tank based on a Sigmoid function is proposed. Moreover, the simulation model for verification and optimization of the control system and the two field test sites for implementing and testing the system are introduced.
Polyacrylonitrile (PAN) nanofibers have specific characteristics such as thermal insulation, weatherproofing, and sunlight resistance and therefore are appropriate to be applied as insulation ...materials for various industries, especially in greenhouse construction. The heat source in greenhouse buildings that operate independently in the heating network comes from heat storage tanks. In the present study, employing thermal field numerical simulations, we investigate the heat flux of a cylindrical heat storage tank with silica aerogel-modified PAN nanofibers as thermal insulation materials. The geometric scale of the tank body, thermal insulation material thickness, and outdoor temperature are optimized to improve thermal insulation. The significant discrepancy in heat flux at different parts of the heat storage tank leads to the extreme heat flux arising at the water–gas interface on the inner and outer walls. It is indicated that the heat flux distribution can be effectively ameliorated by modifying the scale of the tank body to retain the overall water temperature. In particular, effective insulation can merely be acquired when the thermal conductivity of the insulation material is below 3.3 W·m−1·K−1. Eventually, the heat storage tank is optimized to store 1400 L water at 100 °C with a radius of 0.6 m and a thermal insulation thickness of 50 mm at an outdoor temperature of −10 °C, which can maintain excellent thermal insulation for 8 and 24 h at 87.7 and 69.9 °C, respectively.
A ground source heat pump (GSHP) system utilizes a relatively stable underground temperature to achieve energy-saving for heating and cooling in buildings. Among various types of GSHP systems, ...Vertical Closed Loop Ground Source Heat Pump (VGSHP) has received increasing attention due to a variety of advantages such as the potential to be installed in a relatively small space and improved energy efficiency. In this research, in order to improve the system performance of a VGSHP, a VGSHP system coupled with heat storage tank was evaluated. For this purpose, the detailed analysis on the operational behavior of heat storage tank and the variations of heat pump energy performance due to the connection with heat storage tank was performed, and characteristics of heat pump part load ratios (PLRs) and the corresponding energy requirements, compared to chiller and boiler based conventional system, were analyzed in detail, using dynamic energy simulation after comprehensive validation process of heat pump performance curves. The results of this study showed that the VGSHP system coupled with heat storage tank showed an energy saving effect of about 20% for cooling and about 77% for heating compared to the conventional air conditioning system, and an energy saving effect of about 2% for cooling and about 15% for heating compared to the VGSHP system without heat storage tank, mainly due to the fact that the operational pattern of heat pump such as PLR and COP characteristics was changed by the operation of heat storage tank.
The introduction of a heat storage tank (HST) into a cogeneration power plant was considered in this paper. The power plant investigated consisted of multiple power production units and operated in a ...two-tariff electricity pricing market. The HST tank capacity was optimized for maximum profits with and without consideration of the investment costs. When the investment costs were included in the optimization, the optimal HST capacity was nearly halved. Optimal sizing of the HST using heat consumption data from prior years requires over one thousand variables in the mathematical model. A novel method was proposed to drastically reduce the number of variables and find the optimal HST capacity using existing optimization algorithms on a typical computer. The results show that introduction of an HST to electrical and thermal energy generation can increase profits and thermal production capacity of the combined cycle power plant.
•Novel method of finding optimal daily HST capacity was proposed.•Method can be used for finding an optimal 24-h operation of CHP power plant.•Possible to use efficiently different solver routines.•Conclusion is that it is possible to gain financial benefit using HST.•Method is appropriate also for next day optimal driving of complex CHP.
Thermocline sensible heat storage (SHS) systems are usually utilized in parabolic trough solar power systems. Liquid lead–bismuth eutectic (LBE) is a potential heat transfer medium for SHS systems, ...but its influences on the performances of SHS systems are rarely studied. In this study, a simulation model of thermocline SHS tank using liquid LBE as the heat transfer fluid is established, and the influences of initial cold and hot LBE temperatures on the operation and mechanical performances of the tank are estimated. The results reveal that when the liquid LBE is used as the heat transfer fluid, the SHS tank can operate stably. The initial cold LEB temperature has almost no influence on both the total heat storage and heat release durations of the tank, while the initial hot LBE temperature has proportional relationships with the total heat storage and heat release durations. The heat storage performance as well as the heat release behavior of the tank can be improved by increasing the initial cold LBE temperature, or by decreasing the initial hot LBE temperature. The peak maximum mechanical stress of the tank can be decreased by increasing the initial cold LBE temperature, or by decreasing the initial hot LBE temperature.
Improving the flexibility of combined heat and power (CHP) units is an important way to solve the problem of wind power accommodation in northern China. Firstly, this paper analyzes the principle of ...an extraction-type CHP unit, calculates its safe operation range, and analyzes its contradiction between heating and peaking. Secondly, the safe operation ranges of the CHP unit with several flexibility modifications are further calculated, which involve two-stage bypass, low-pressure cylinder (LPC) removal, heat storage tank, and electric boiler. Finally, based on the safe operation ranges, their effects on improving the capabilities of deep peak shaving and wind power accommodation are compared, and their adaptabilities to different wind scenarios are analyzed. The results show that: ① all flexibility modifications can improve the deep peak shaving capability of the CHP unit, especially for the two-stage bypass and the electric boiler; ② LPC removal modification can accommodate wind power to some extent, but most of wind power is still abandoned; ③ heat storage tank modification is unstable in different wind scenarios, which is determined by the surplus heating capability during the daytime.
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