scholarly journals Synthesis and Characterization of Molten Salt Nanofluids for Thermal Energy Storage Application in Concentrated Solar Power Plants—Mechanistic Understanding of Specific Heat Capacity Enhancement

Nanomaterials ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 2266
Author(s):  
Binjian Ma ◽  
Donghyun Shin ◽  
Debjyoti Banerjee
Keyword(s):  
Heat Capacity ◽  
Energy Storage ◽  
Specific Heat ◽  
Molten Salt ◽  
Specific Heat Capacity ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Solar Power ◽  
Alumina Nanoparticles ◽  
Concentrated Solar Power

Molten salts mixed with nanoparticles have been shown as a promising candidate as the thermal energy storage (TES) material in concentrated solar power (CSP) plants. However, the conventional method used to prepare molten salt nanofluid suffers from a high material cost, intensive energy use, and laborious process. In this study, solar salt-Al2O3 nanofluids at three different concentrations are prepared by a one-step method in which the oxide nanoparticles are generated in the salt melt directly from precursors. The morphologies of the obtained nanomaterials are examined under scanning electron microscopy and the specific heat capacities are measured using the temperature history (T-history) method. A non-linear enhancement in the specific heat capacity of molten salt nanofluid is observed from the thermal characterization at a nanoparticle mass concentration of 0.5%, 1.0%, and 1.5%. In particular, a maximum enhancement of 38.7% in specific heat is found for the nanofluid sample prepared with a target nanoparticle mass fraction of 1.0%. Such an enhancement trend is attributed to the formation of secondary nanostructure between the alumina nanoparticles in the molten salt matrix following a locally-dispersed-parcel pattern. These findings provide new insights to understanding the enhanced energy storage capacity of molten salt nanofluids.

Mechanism Exploration of the Enhancement of Thermal Energy Storage in Molten Salt Nanofluid

2021 ◽  
Author(s):  
Zhao Li ◽  
Liu Cui ◽  
B. R. Li ◽  
xiaoze du
Keyword(s):  
Molecular Dynamics ◽  
Heat Capacity ◽  
Energy Storage ◽  
Specific Heat ◽  
Molten Salt ◽  
Specific Heat Capacity ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Md Simulations

The enhancement of the specific heat capacity of molten salt-based nanofluid is investigated via molecular dynamics (MD) simulations. The results show the addition of the nanoparticle indeed enhances the specific...

Investigation of Molten Salt Nanomaterial as Thermal Energy Storage in Concentrated Solar Power

2012 ◽  
Author(s):  
Bharath Dudda ◽  
Donghyun Shin
Keyword(s):  
Heat Capacity ◽  
Energy Storage ◽  
Specific Heat ◽  
Molten Salt ◽  
Specific Heat Capacity ◽  
Thermal Energy ◽  
Molten Salts ◽  
Oxide Nanoparticles ◽  
Concentrated Solar Power ◽  
Mineral Oils

It is a known fact that the solar energy is the most abundant form of renewable source of energy available abundantly in most of the areas. It is relatively the most promising form of renewable energy through which many developed countries like US, Spain are generating electricity using CSP, PV, and other forms of solar cells. This paper mainly focuses on the Concentrated Solar Power (CSP) and about the method of enhancing the Thermal Energy Storage (TES) capacity. Here, we use molten salt as the Heat Transfer Fluid (HTF) as an alternative to mineral oils and other commonly used HTF. The reasons behind using molten salts have also been listed in the paper. The major disadvantage in molten salts as a HTF is their low specific heat capacity compared to mineral oils. The low specific heat capacity of molten salt can be enhanced by dispersing oxide nanoparticles. In this paper, we synthesized molten salt nanomaterials by dispersing oxide nanoparticles in to selcte4d molten salts. Specific heat capacity measurement was performed using a modulated differential scanning calorimeter (MDSC). Hence, we evaluated the use of molten salt nanomaterials as HTF in CSP.

Enhanced Heat Capacity of Molten Salt Nano-Materials for Concentrated Solar Power Application

2012 ◽  
Author(s):  
Ramaprasath Devaradjane ◽  
Donghyun Shin
Keyword(s):  
Heat Capacity ◽  
Energy Storage ◽  
Molten Salt ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Molten Salts ◽  
Solar Power ◽  
Storage Temperature ◽  
Nano Materials ◽  
Concentrated Solar Power

Storage of thermal energy using molten salt materials has been widely explored for concentrating solar power. Since these power plants use thermodynamic cycle, the overall system cycle efficiency significantly relies on the thermal energy storage temperature. Therefore, increasing the thermal energy storage temperature and decreasing the amount of material needed can result in reducing the cost of solar energy. Molten salts are stable up to 700°C, relatively cheap, and safe to the environment. However, the heat capacity of the molten salts is typically low (∼1.5 J/gK) compared to other thermal storage materials. The low heat capacity of molten salts can be improved by dispersing nanoparticles. In this study, we synthesized molten salt nanomaterial by dispersing oxide nanoparticles into selected molten salts. Heat capacity measurements were performed using a modulated differential scanning calorimeter. Materials characterization studies were performed using a scanning electron microscopy. Hence, we evaluated the use of the molten salt nanomaterials as thermal energy storage media in concentrated solar power applications. Increase in the specific heat capacity of the molten salt is also demonstrated on addition with Nano materials of specific size and quantity.

Waste From Metallurgic Industry: A Sustainable High-Temperature Thermal Energy Storage Material for Concentrated Solar Power

2013 ◽  
Author(s):  
Nicolas Calvet ◽  
Guilhem Dejean ◽  
Lucía Unamunzaga ◽  
Xavier Py
Keyword(s):  
Heat Capacity ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Solar Power ◽  
Low Cost ◽  
Concentrated Solar Power ◽  
Storage Material ◽  
Energy Storage Material ◽  
Thermal Energy Storage Material

The ambitious DOE SunShot cost target ($0.06/kWh) for concentrated solar power (CSP) requires innovative concepts in the collector, receiver, and power cycle subsystems, as well as in thermal energy storage (TES). For the TES, one innovative approach is to recycle waste from metallurgic industry, called slags, as low-cost high-temperature thermal energy storage material. The slags are all the non-metallic parts of cast iron which naturally rises up by lower density at the surface of the fusion in the furnace. Once cooled down some ceramic can be obtained mainly composed of oxides of calcium, silicon, iron, and aluminum. These ceramics are widely available in USA, about 120 sites in 32 States and are sold at a very low average price of $5.37/ton. The US production of iron and steel slag was estimated at 19.7 million tons in 2003 which guarantees a huge availability of material. In this paper, electric arc furnace (EAF) slags from steelmaking industry, also called “black slags”, were characterized in the range of temperatures of concentrated solar power. The raw material is thermo-chemically stable up to 1100 °C and presents a low cost per unit thermal energy stored ($0.21/kWht for ΔT = 100 °C) and a suitable heat capacity per unit volume of material (63 kWht/m3for ΔT = 100°C). These properties should enable the development of new TES systems that could achieve the TES targets of the SunShot (temperature above 600 °C, installed cost below $15/kWht, and heat capacity ≥25 kWht/m3). The detailed experimental results are presented in the paper. After its characterization, the material has been shaped in form of plates and thermally cycled in a TES system using hot-air as heat transfer fluid. Several cycles of charge and discharged were performed successfully and the concept was validated at laboratory scale. Apart from availability, low-cost, and promising thermal properties, the use of slag promotes the conservation of natural resources and is a noble solution to decrease the cost and to develop sustainable TES systems.

Experimental Investigation of Molten Salt Nanofluid for Solar Thermal Energy Application

2011 ◽  
Author(s):  
Donghyun Shin ◽  
Debjyoti Banerjee
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Specific Heat ◽  
Molten Salt ◽  
Specific Heat Capacity ◽  
Thermal Energy ◽  
Molten Salts ◽  
Solar Power ◽  
Solar Thermal ◽  
Wide Range

The overall efficiency of a Concentrated Solar Power (CSP) system is critically dependent on the thermo-physical properties of the Thermal Energy Storage (TES) components and the Heat Transfer Fluid (HTF). Higher operating temperatures in CSP result in enhanced thermal efficiency of the thermodynamic cycles that are used in harnessing solar energy (e.g., using Rankine cycle or Stirling cycle). Particlularly, high specific heat capacity (Cp) and high thermal conductivity (k) of the HTF and TES materials enable reduction in the size and overall cost of solar power systems. However, only a limited number of materials are compatible for the high operating temperature requirements (exceeding 400°C) envisioned for the next generation of CSP systems. Molten salts have a wide range of melting point (200°C∼500°C) and are thermally stable up to 700°C. However, thermal property values of the molten salts are typically quite low (Cp is typically less than ∼2J/g-K and k is typically less than ∼1 W/m-K). To obviate these issues the molten salts can be doped with nanoparticles — resulting in the synthesis / formation of nanomaterials (nanocomposites and nanofluids). Nanofluids are colloidal suspensions formed by doping with minute concentration of nanoparticles. Nanofluids were reported for anomalous enhancement in their thermal conductivity values. In this study, molten salt-based nanofluids were synthesized by liquid solution method. A differential scanning calorimeter (DSC) was used to measure the specific heat capacity values of the proposed nanofluids. The observed enhancement in specific heat is then compared with predictions from conventional thermodynamic models (e.g. thermal equilibrium model or “simple mixing rule”). Transmission Electron Microscopy (TEM) is used to verify that minimal aggregation of nanoparticles occurred before and after the thermocycling experiments. Thermocycling experiments were conducted for repeated measurements of the specific heat capacity by using multiple freeze-thaw cycles of the nanofluids/ nano-composites, respectively. This study demonstrates the feasibility for using novel nanomaterials as high temperature nanofluids for applications in enhancing the operational efficiencies as well as reducing the cost of electricity produced in solar thermal systems utilizing CSP in combination with TES.

scholarly journals Effectiveness of Thermal Properties in Thermal Energy Storage Modeling

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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