Investigation of High Temperature Nanofluids for Solar Thermal Power Conversion and Storage Applications

The aim of this study is to investigate the enhancement of thermal properties of various high temperature nanofluids for solar thermal energy storage application. In concentrating solar power (CSP) systems, the thermo-physical properties of the heat transfer fluids (HTF) and the thermal energy storage (TES) materials are key to enhancing the overall system efficiency. Molten salts, such as alkali nitrates, alkali carbonates, or eutectics are considered as alternatives to conventional HTF to extend the capabilities of CSP. However, there is limited usage of molten salt eutectics as the HTF material, since the heat capacity of the molten salts are lower than that of conventional HTF. Nanofluid is a mixture of a solvent and nanoparticles. Well dispersed nanoparticles can be used to enhance thermo-physical properties of HTF. In this study, silica (SiO2) and alumina (Al2O3) nanoparticles as well as carbon nanotubes (CNT) were dispersed into a molten salt and a commercially available HTF. The specific heat capacity of the nanofluids were measured and applicability of such nanofluid materials for solar thermal storage applications were explored. Measurements performed using the carbonate eutectics and commercial HTF that are doped with inorganic and organic nano-particles show specific heat capacity enhancements exceeding 5–20% at concentrations of 0.05% to 2.0% by weight. Dimensional analyses and computer simulations were performed to predict the enhancement of thermal properties of the nanofluids. The computational studies were performed using Molecular Dynamics (MD) simulations.

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A New Ternary Chloride Eutectic Mixture and its Thermo-physical Properties for Solar Thermal Energy Storage

Energy Procedia ◽

10.1016/j.egypro.2014.11.1089 ◽

2014 ◽

Vol 61 ◽

pp. 1314-1317 ◽

Cited By ~ 8

Author(s):

Xiaolan Wei ◽

Ming Song ◽

Qiang Peng ◽

Jing Ding ◽

Jianping Yang

Keyword(s):

Energy Storage ◽

Physical Properties ◽

Thermal Energy ◽

Thermal Energy Storage ◽

Eutectic Mixture ◽

Solar Thermal ◽

Solar Thermal Energy ◽

Thermo Physical Properties

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Experimental Study of Nanoengineered Molten Salts as Thermal Energy Storage in Solar Power Plants

Volume 6: Energy, Parts A and B ◽

10.1115/imece2012-87692 ◽

2012 ◽

Cited By ~ 1

Author(s):

Hani Tiznobaik ◽

Donghyun Shin

Keyword(s):

Energy Storage ◽

Physical Properties ◽

High Temperatures ◽

Thermal Energy ◽

Thermal Energy Storage ◽

Molten Salts ◽

Solar Power ◽

Operating Temperature ◽

Concentrated Solar Power ◽

Thermo Physical Properties

In a concentrated solar power (CSP), high operating temperature (over 500 °C) is the key for enhancing the efficiency of the system. The operating temperature of the system mainly relies on thermal energy storage (TES) material. Existing TES materials such as mineral oil or paraffin wax cannot be applicable at high temperatures, since these materials are not thermally stable over 400 °C. However, very few materials are suitable and reliable for the high temperatures. Using molten salts (e.g., alkali nitrate, alkali carbonate, alkali chloride, etc.) as thermal energy storage material is an alternative way due to several benefits. They are cheap and environmentally safe compared with the conventional TES materials. They are thermally stable at higher temperatures (over 500 °C). However, their usage is limited due to low thermo-physical properties (e.g. Cp is less than 1.6 J/g°C). The low thermo-physical properties can be improved by dispersing nanoparticles into the salts. In this study, nanomaterials were synthesized by dispersing inorganic nanoparticles into ionic salts. Modulated differential scanning calorimeter (MDSC) was used to measure the heat capacity of the nanomaterials. Scanning electron microscopy (SEM) was used for material characteristic analysis. Hence, the application of the nanomaterials as thermal energy storage in a concentrated solar power was explored.

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Demonstration of Phase Change Thermal Energy Storage in Zinc Oxide Microencapsulated Sodium Nitrate

Applied Sciences ◽

10.3390/app11136234 ◽

2021 ◽

Vol 11 (13) ◽

pp. 6234

Author(s):

Ciprian Neagoe ◽

Ioan Albert Tudor ◽

Cristina Florentina Ciobota ◽

Cristian Bogdanescu ◽

Paul Stanciu ◽

...

Keyword(s):

Zinc Oxide ◽

Thermal Properties ◽

High Temperature ◽

Energy Storage ◽

Phase Change ◽

Thermal Energy ◽

Sodium Nitrate ◽

Thermal Energy Storage ◽

Metal Corrosion ◽

Scanning Calorimetry

Microencapsulation of sodium nitrate (NaNO3) as phase change material for high temperature thermal energy storage aims to reduce costs related to metal corrosion in storage tanks. The goal of this work was to test in a prototype thermal energy storage tank (16.7 L internal volume) the thermal properties of NaNO3 microencapsulated in zinc oxide shells, and estimate the potential of NaNO3–ZnO microcapsules for thermal storage applications. A fast and scalable microencapsulation procedure was developed, a flow calorimetry method was adapted, and a template document created to perform tank thermal transfer simulation by the finite element method (FEM) was set in Microsoft Excel. Differential scanning calorimetry (DSC) and transient plane source (TPS) methods were used to measure, in small samples, the temperature dependency of melting/solidification heat, specific heat, and thermal conductivity of the NaNO3–ZnO microcapsules. Scanning electron microscopy (SEM) and chemical analysis demonstrated the stability of microcapsules over multiple tank charge–discharge cycles. The energy stored as latent heat is available for a temperature interval from 303 to 285 °C, corresponding to onset–offset for NaNO3 solidification. Charge–self-discharge experiments on the pilot tank showed that the amount of thermal energy stored in this interval largely corresponds to the NaNO3 content of the microcapsules; the high temperature energy density of microcapsules is estimated in the range from 145 to 179 MJ/m3. Comparison between real tank experiments and FEM simulations demonstrated that DSC and TPS laboratory measurements on microcapsule thermal properties may reliably be used to design applications for thermal energy storage.

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Multidisciplinary Approaches for Assessing a High Temperature Borehole Thermal Energy Storage Facility at Linköping, Sweden

Energies ◽

10.3390/en14144379 ◽

2021 ◽

Vol 14 (14) ◽

pp. 4379

Author(s):

Max Hesselbrandt ◽

Mikael Erlström ◽

Daniel Sopher ◽

Jose Acuna

Keyword(s):

Thermal Properties ◽

High Temperature ◽

Energy Storage ◽

Thermal Energy ◽

Thermal Energy Storage ◽

Thermal Response ◽

Site Investigation ◽

Thermal Response Test ◽

Response Test ◽

Crystalline Bedrock

Assessing the optimal placement and design of a large-scale high temperature energy storage system in crystalline bedrock is a challenging task. This study applies and evaluates various methods and strategies for pre-site investigation for a potential high temperature borehole thermal energy storage (HT-BTES) system at Linköping in Sweden. The storage is required to shift approximately 70 GWh of excess heat generated from a waste incineration plant during the summer to the winter season. Ideally, the site for the HT-BTES system should be able to accommodate up to 1400 wells to 300 m depth. The presence of major fracture zones, high groundwater flow, anisotropic thermal properties, and thick Quaternary overburden are all factors that play an important role in the performance of an HT-BTES system. Inadequate input data to the modeling and design increases the risk of unsatisfactory performance, unwanted thermal impact on the surroundings, and suboptimal placement of the HT-BTES system, especially in a complex crystalline bedrock setting. Hence, it is crucial that the subsurface geological conditions and associated thermal properties are suitably characterized as part of pre-investigation work. In this study, we utilize a range of methods for pre-site investigation in the greater Distorp area, in the vicinity of Linköping. Ground geophysical methods, including magnetic and Very Low-Frequency (VLF) measurements, are collected across the study area together with outcrop observations and lab analysis on rock samples. Borehole investigations are conducted, including Thermal Response Test (TRT) and Distributed Thermal Response Test (DTRT) measurements, as well as geophysical wireline logging. Drone-based photogrammetry is also applied to characterize the fracture distribution and orientation in outcrops. In the case of the Distorp site, these methods have proven to give useful information to optimize the placement of the HT-BTES system and to inform design and modeling work. Furthermore, many of the methods applied in the study have proven to require only a fraction of the resources required to drill a single well, and hence, can be considered relatively efficient.

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