Experimental Measurements and Thermodynamic Modeling of Melting Temperature of the Binary Systems n-C11H24–n-C14H30, n-C12H26–n-C13H28, n-C12H26–n-C14H30, and n-C13H28–n-C15H32 for Cryogenic Thermal Energy Storage

Thermal storage plays a major role in a wide variety of industrial, commercial, and residential applications when there is a mismatch between the offer and the claim of energy. In this paper, we study numerically the contribution of phase change materials (PCMs) for solar thermal energy storage (TES) in buildings. The studied configuration is a plane solar collector incorporating a PCM layer and coupled to a concrete slab (a roof of a building). The study is conducted for Casablanca (Morocco) meteorological conditions. Several simulations were performed to optimize the melting temperature and the PCM layer thickness. The results show that PCM imposes, on the roof, a temperature close to its melting temperature. The choice of a melting temperature Tmelt = 22 °C (the local indoor temperature Tc is fixed as Tc = 22 °C) limits the losses through the concrete slab, considerably. This last seems to be, nearly, adiabatic, in this case. Also, the energy released by PCM solidification, overnight, increases the outlet temperature of the coolant fluid to 35 °C and the useful flux to 80 W/m2, increasing the efficiency of the solar collector by night. The PCM functioned both as an energy storage material for the stabilization of the coolant fluid temperature and as an insulating material for the building.

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Molten Nitrate Salt Development for Thermal Energy Storage in Parabolic Trough Solar Power Systems

ASME 2009 3rd International Conference on Energy Sustainability, Volume 2 ◽

10.1115/es2009-90140 ◽

2009 ◽

Cited By ~ 21

Author(s):

Robert W. Bradshaw ◽

Joseph G. Cordaro ◽

Nathan P. Siegel

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Energy Storage ◽

Thermal Energy ◽

Thermal Energy Storage ◽

Molten Salts ◽

Experimental Measurements ◽

Nitrate Salt ◽

Parabolic Trough ◽

Salt Mixtures

Multi-component molten salts have been formulated recently that may enhance thermal energy storage for parabolic trough solar power plants. This paper presents further developments regarding molten salt mixtures consisting of common alkali nitrates and either alkaline earth nitrates or alkali nitrite salts that have advantageous properties for applications as heat transfer fluids in parabolic trough systems. We report results for formulations of inorganic molten salt mixtures that display freeze-onset temperatures below 100°C. In addition to phasechange behavior, several properties of these molten salts that significantly affect their suitability as thermal energy storage fluids were evaluated, including chemical stability and viscosity. The nitrate-based molten salts have demonstrated chemical stability in the presence of air up to 500°C. The capability to operate at temperatures up to 500°C may allow an increase in maximum temperature operating capability vs. organic fluids in existing trough systems and will enable increased power cycle efficiency. Experimental measurements of viscosity were performed from near the freeze-onset temperature to about 200°C. Viscosities can exceed 100 cP near the freezing temperature but are 4 to 5 cP in the anticipated operating temperature range. Experimental measurements of density, thermal conductivity and heat capacity are in progress and will be reported at the meeting. Corrosion tests were conducted for several thousand hours at 500°C with stainless steels and at 350°C for carbon and chromium-molybdenum steels. Examination of the specimens demonstrated good compatibility of these materials with the molten nitrate salt mixtures. Laboratory studies were conducted to identify mixtures of nitrate and nitrite (NO2−) salts as additional candidates for a low-melting heat transfer fluid. Mixtures in which the cations were potassium, sodium and lithium, in various proportions, demonstrated freezing points as low as 70°C for a particular nitrate/nitrite anion composition. Development has emphasized mixtures that minimize lithium content in order to reduce the cost as the lithium salt is the most expensive constituent. Work is in progress to explore the phase diagram of the 1:1 mol ratio of nitrate/nitrite and to evaluate physical properties such as viscosity, density and thermal conductivity. Results to date indicate that the viscosity of these mixtures is considerably less than nitrate-only melts, which necessarily contain calcium cations to suppress freezing to similarly low temperatures.

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Effectiveness of Thermal Properties in Thermal Energy Storage Modeling

Frontiers in Mechanical Engineering ◽

10.3389/fmech.2021.690793 ◽

2021 ◽

Vol 7 ◽

Author(s):

Law Torres Sevilla ◽

Jovana Radulovic

Keyword(s):

Thermal Conductivity ◽

Heat Capacity ◽

Thermal Properties ◽

Energy Storage ◽

Specific Heat ◽

Melting Temperature ◽

Latent Heat ◽

Specific Heat Capacity ◽

Thermal Energy ◽

Thermal Energy Storage

This paper studies the influence of material thermal properties on the charging dynamics in a low temperature Thermal Energy Storage, which combines sensible and latent heat. The analysis is based on a small scale packed bed with encapsulated PCMs, numerically solved using COMSOL Multiphysics. The PCMs studied are materials constructed based on typical thermal properties (melting temperature, density, specific heat capacity (solid and liquid), thermal conductivity (solid and liquid) and the latent heat) of storage mediums in literature. The range of values are: 25–65°C for the melting temperature, 10–500 kJ/kg for the latent heat, 600–1,000 kg/m3 for the density, 0.1–0.4 W/mK (solid and liquid) for the thermal conductivity and 1,000–2,200 J/kgK (solid and liquid) for the specific heat capacity. The temperature change is monitored at three different positions along the tank. The system consists of a 2D tank with L/D ratio of 1 at a starting temperature of 20°C. Water, as the heat transfer fluid, enters the tank at 90°C. Results indicate that latent heat is a leading parameter in the performance of the system, and that the thermal properties of the PCM in liquid phase influence the overall heat absorption more than its solid counterpart.

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Numerical Investigation of a Phase Change Material Building Integrating Solar Thermal Collector PCM-BST

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4053057 ◽

2021 ◽

pp. 1-34

Author(s):

Benkadour Ayman ◽

Mustapha Faraji

Keyword(s):

Energy Storage ◽

Phase Change ◽

Numerical Investigation ◽

Melting Temperature ◽

Phase Change Material ◽

Thermal Energy ◽

Thermal Energy Storage ◽

Solar Collector ◽

Concrete Wall ◽

Change Material

Abstract Sensible thermal energy storage systems can reduce energy environmental fluctuation dependency with the nocturnal energy needs usage in maintaining the building's comfort levels. In the present paper, Phase Change Material (PCM) is introduced to improve the thermal energy storage capacity of a solar collector integrating a novel composite Phase Change Material (PCM)/concrete wall. A mathematical model based upon the conservation and heat transfer equations has been developed using the enthalpy method. The Numerical investigation has been implemented into a personal FORTRAN code. Many series of simulation runs were executed. The position of the PCM layer within the wall and the PCM melting temperature are varied in the range 0 cm ≤ xm ≤ 7.5 cm and 15 °C ≤ Tm ≤ 35 °C, respectively. The objective is to let inner temperature Tin swing close to a comfort threshold. The position of PCM close to the absorber improves the efficiency of the room heating with good nocturnal use of latent heat stored during the day. PCM melting temperature affects deeply the composite PCM/concrete wall/solar collector behavior. Lastly, PCM gained the system an important benefit which is the solar collector high-Temperature isolation as to not reach the room and disturb the inside comfort zone by melting and solidifying. Those parameters can be considered as the primary pointers for PCM/wall integrated solar collector design. Also, a Daily Heating Potential, Qh, and Thermal Load Leveling, TLL, are introduced to evaluate the system performance.

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