High-temperature Energy Storage Research Articles

High-temperature liquid Sn-air energy storage cell

Α new type of a high temperature liquid metal-air energy storage cell based on solid oxide electrolyte has been successfully demonstrated at 750 °C by feeding metal Sn. In order to understanding the initial size effect of metal as a liquid fuel, we report here the impact of the thermal and electrochemical oxidation behavior of nano Sn (∼100 nm), comparing with micro-sized (∼5 µm) and macro-sized (∼350 µm) Sn. The thermogravimetric analysis and the monitoring OCV test indicate that the distinct property of nano-sized Sn results in a favorable thermal oxidation behavior near the melting point and a promising power performance due to enhanced fuel transport to the anode. However, the accumulated Sn oxide at the reaction interface during a discharge test towards the limitation of further electrochemical oxidation.

Flexible high-temperature dielectric materials from polymer nanocomposites.

Dielectric materials, which store energy electrostatically, are ubiquitous in advanced electronics and electric power systems. Compared to their ceramic counterparts, polymer dielectrics have higher breakdown strengths and greater reliability, are scalable, lightweight and can be shaped into intricate configurations, and are therefore an ideal choice for many power electronics, power conditioning, and pulsed power applications. However, polymer dielectrics are limited to relatively low working temperatures, and thus fail to meet the rising demand for electricity under the extreme conditions present in applications such as hybrid and electric vehicles, aerospace power electronics, and underground oil and gas exploration. Here we describe crosslinked polymer nanocomposites that contain boron nitride nanosheets, the dielectric properties of which are stable over a broad temperature and frequency range. The nanocomposites have outstanding high-voltage capacitive energy storage capabilities at record temperatures (a Weibull breakdown strength of 403 megavolts per metre and a discharged energy density of 1.8 joules per cubic centimetre at 250 degrees Celsius). Their electrical conduction is several orders of magnitude lower than that of existing polymers and their high operating temperatures are attributed to greatly improved thermal conductivity, owing to the presence of the boron nitride nanosheets, which improve heat dissipation compared to pristine polymers (which are inherently susceptible to thermal runaway). Moreover, the polymer nanocomposites are lightweight, photopatternable and mechanically flexible, and have been demonstrated to preserve excellent dielectric and capacitive performance after intensive bending cycles. These findings enable broader applications of organic materials in high-temperature electronics and energy storage devices.

Design and thermal properties of a novel ternary chloride eutectics for high-temperature solar energy storage

A new ternary chloride salt mixture, named SYSU-4, was developed composed of NaCl, CaCl2 and MgCl2 to meet the needs of solar energy storage over 550°C. The eutectic point and composition of SYSU-4 was predicted from the calculated phase diagram and also validated by differential scanning calorimetry (DSC). SYSU-4 was prepared experimentally by static melting method and its thermo-physical properties including heat capacity, density and viscosity at high temperature were measured, which were determined by DSC, Archimedes and vibration–rotation methods, respectively. According to the calculated ternary phase diagram, the lowest eutectic temperature was 424.05°C, in good agreement with experimental results of 424°C measured by DSC. Heat capacity of SYSU-C4 was averaged as 0.83 and 1.19J/gK for solid and liquid phase, respectively referred to sapphire standard material. Density of SYSU-C4 decreased linearly from 2.5g/cm3 to 1.9g/cm3 with the increase of temperature from 500 to 750°C. Viscosity of SYSU-C4 also decreased from 4.0cp to 3.0cp as the temperature increased. Negligible changes on the melting and freezing points of SYSU-C4 in 50 thermal cycles at 370–550°C indicates excellent thermal cycling stability. Moreover, the thermal stability of SYSU-C4 was excellent under 700°C. The developed ternary chloride salt mixture SYSU-4 can be a promising eutectic mixture for high-temperature solar thermal energy storage.

Investigation of LaxSr1−xCoyM1−yO3−δ (M = Mn, Fe) perovskite materials as thermochemical energy storage media

Materials in the LaxSr1−xCoyMn1−yO3−δ (LSCM) and LaxSr1−xCoyFe1−yO3−δ (LSCF) families are candidates for high-temperature thermochemical energy storage due to their facility for cyclic endothermic reduction and exothermic oxidation. A set of 16 LSCM and 21 LSCF compositions were synthesized by a modified Pechini method and characterized by powder X-ray diffraction and thermogravimetric analysis. All materials were found to be various symmetries of the perovskite phase. LSCM was indexed as tetragonal, cubic, rhombohedral, or orthorhombic as a function of increased lanthanum content. For LSCF, compositions containing low lanthanum content were indexed as cubic while materials with high lanthanum content were indexed as rhombohedral. An initial screening of redox activity was completed by thermogravimetric analysis for each composition. The top three compositions with the greatest recoverable redox capacity for each family were further characterized in equilibrium thermogravimetric experiments over a range of temperatures and oxygen partial pressures. These equilibrium experiments allowed the extraction of thermodynamic parameters for LSCM and LSCF compositions operated in thermochemical energy storage conditions.

Efficiency Improvement and Potential LCOE Reduction with an LFR-XX SMS Plant with Storage

Abstract Several forms of renewable energy have in the last decade achieved a remarkable technological improvement and cost effectiveness, including Solar Energy. Photovoltaic systems (PV) are reaching grid parity in the sunniest regions of Europe. Apart from PV, a promising technology is Concentrated Solar Power (CSP) with thermal storage, because it enables higher power plant availability throughout the year as well as dispatchability, a highly important and valuable feature for a power plant. However significant cost reductions are still to be achieved, for CSP to be competitive with conventional electricity production and with PV. In this paper a few technological improvements are described and a proposal is made to combine them in a system that is more efficient and has, simultaneously, the potential of being cheaper. The goal is to show the potential for advanced LFR concepts in combination with high temperature molten salt mixtures and energy storage as being also important contenders to the objective of bringing STE- Solar Thermal Electricity to the market in a competitive way. The concept presented and developed includes a higher ΔT of the heat transfer fluid (HTF), a particular storage strategy and a new optical concept based on a new Linear Fresnel Concentrator (LFR XX SMS-Simultaneous Multiple Surface, Fig.1,2, [1] enabling an important increase in the overall yearly solar to electricity conversion efficiency and generating an important potential for electricity cost reduction. It is shown that values approaching 10eurocents/kWh, for a 50MW plant with 7 hours storage capacity are possible in Southern Europe.

Development of a Concentrating Solar Power System Using Fluidized-bed Technology for Thermal Energy Conversion and Solid Particles for Thermal Energy Storage

Abstract Concentrating solar power (CSP) is an effective way to convert solar energy into electricity with an economic energy-storage capability for grid-scale, dispatchable renewable power generation. However, CSP plants need to reduce costs to be competitive with other power generation methods. Two ways to reduce CSP cost are to increase solar-to-electric efficiency by supporting a high-efficiency power conversion system, and to use low-cost materials in the system. The current nitrate-based molten-salt systems have limited potential for cost reduction and improved power-conversion efficiencywith high operating temperatures. Even with significant improvements in operating performance, these systems face challenges in satisfying the cost and performance targets. This paper introduces a novel CSP system with high-temperature capability that can be integrated into a high-efficiency CSP plant and that meets the low-cost, high-performance CSP targets. Unlike a conventional salt-based CSP plant, this design uses gas/solid, two-phase flow as the heat-transfer fluid (HTF); separated solid particles as storage media; and stable, inexpensive materials for the high-temperature receiver and energy storage containment. We highlightthe economic and performance benefits of this innovative CSP system design, whichhas thermal energy storage capability for base-load power generation.

High temperature energy storage performances of methane reforming with carbon dioxide in a tubular packed reactor

High temperature heat transfer and energy storage performances of methane reforming with carbon dioxide in tubular packed reactor are investigated under different operating conditions. Experimental results show that the methane reforming in tubular packed reactor can efficiently store high temperature thermal energy, and the sensible heat and heat loss besides thermochemical energy storage play important role in the total energy storage process. When the operating temperature is increased, the thermochemical storage efficiency first increases for methane conversion rising and then decreases for heat loss rising. As the operating temperate is 800°C, the methane conversion is 79.6%, and the thermochemical storage efficiency and total energy efficiency can be higher than 47% and 70%. According to the experimental system, the flow and reaction model of methane reforming is established using the laminar finite-rate model and Arrhenius expression, and the simulated methane conversion and energy storage efficiency fit with experimental data. Along the flow direction, the fluid temperature in the catalyst bed first decreases because of the endothermic reaction and then increases for the heat transfer from reactor wall. As a conclusion, the maximum thermochemical storage efficiency will be obtained under optimal operating temperature and optimal flow rate, and the total energy efficiency can be increased by the increase of bed conductivity and decrease of heat loss coefficient.

Use of encapsulated zinc particles in a eutectic chloride salt to enhance thermal energy storage capacity for concentrated solar power

Concentrated Solar Power (CSP) is considered as a viable large-scale renewable energy source to produce electricity. However, current costs to produce electricity from CSP are not cost competitive as compared to the traditional energy generation technologies based on fossil fuels and nuclear. It is envisioned that development of high efficiency and high heat capacity thermal storage fluids will increase system efficiency, reduce structural storage volume, and hence, contribute to reducing costs. Particularly, with respect to CSP, current high temperature energy storage fluids, such as molten salts, are relatively limited in terms of their thermal energy storage capacity and thermal conductivity. The current work explores possibility of boosting the thermal storage capacity of molten salts through latent heat of added phase change materials. We studied the advantage of adding coated Zn micron-sized particles to alkali chloride salt eutectic for enhanced thermal energy storage. Zinc particles (0.6 μm and 5 μm) obtained from commercial source were coated with an organo-phosphorus shell to improve chemical stability and to prevent individual particles from coalescing with one another during melt/freeze cycles. Thermal cycling tests (200 melt/freeze cycles) showed that coated Zn particles have good thermal stability and are chemically inert to alkali chloride salt eutectic in both N2 and in air atmospheres. Elemental mapping of the cross-sectional view of coated Zn particles from the composite after thermal cycles showed no signs of oxidation, agglomeration or other type of particle degradation. The measured enhancement in volumetric thermal storage capacity of the composite with just ∼10 vol% of coated Zn particles over the base chloride salt eutectic varies from 15% to 34% depending on cycling temperature range (ΔT = 50°C–100 °C).

Oxidation and reduction kinetics of iron and iron based alloys used as storage materials in high temperature battery

The background of the present studies relates to the development of a novel high temperature energy storage system based on a solid oxide cell. The energy is stored in a metal/metal oxide system which is part of the fuel side of the cell. The aim of the present study was to evaluate the suitability of pure iron and iron based model alloys as possible energy storage material for this type of high temperature battery system at a service temperature of 800°C. For this purpose the oxidation and reduction behaviour of iron in Ar–H2–(H2O) environments has been examined. The reduction process in Ar–2%H2 of the wüstite scale formed on pure iron in Ar–H2–H2O was hampered by the formation of a continuous, gas tight metallic iron layer on its surface. Possible approaches to increase oxidation and reduction kinetics by optimised alloy compositions for the Fe storage are discussed.

Solid State Electrolytes for Ambient and Middle Temperature Next Generation Electrochemical Storage Systems

Solid state electrolytes are typically known for their utilization in high-temperature or stationary electrochemical energy storage systems. For practical applications as well as for next generation systems like sulfur or air cells, the solid state electrolyte (SSE) has to be stable, dense and flexible. The thickness therefore needs to be reduced to obtain an acceptable passive weight. The aim of this study is the demonstration of an innovative, flexible solid state electrolyte for future systems, and to calculate the impact of its thickness on the energy densities of various storage systems.

TiO2-decorated graphite nanoplatelet nanocomposites for high-temperature sensor applications.

Temperature and/or composition mapping inside high temperature energy conversion and storage devices are challenging, yet of critical importance to improve the material design for optimum performance. Here, the great potential of TiO2 nanoparticle (NP)-decorated graphite nanoplatelet (GNP) nanocomposites as high temperature thermal senors or gas sensors is reported. Effects of the GNP substrate on phonon confinement in Raman spectrum, grain growth, and phase stability of anatase TiO2 NPs at high temperatures are systematically studied. Thermally sensitive Raman signatures, indicating the ultrafast grain growth of TiO2 NPs in response to short thermal shock treatments (0.1-25 s) at high temperatures, are exploited for high temperature thermal sensing applications. A very high accuracy of nearly 98% in temperature measurements is demonstrated for a given short-time thermal exposure. Thermal stability of anatase TiO2 NPs against transformation into the rutile phase in TiO2 -GNP nancomposites is substantially increased by controlling the surface area of the substrate, which would significantly improve the performance of TiO2 -based high temperature gas sensors.

Power-To-Storage - The Use of an Anode-Supported Solid Oxide Fuel Cell as a High-Temperature Battery

A novel high-temperature energy storage system based on an SOFC is presented (Power-to-Storage). The energy is stored as a metal/metal oxide which is part of the fuel side. However, in contrast to a classical SOFC, the fuel side is kept under stagnant hydrogen/water vapor. By using the cell as an electrolyzer (SOEC), the surplus electricity (from renewable energy sources) is used to charge the system by reducing a metal oxide. Vice versa, if energy is needed the system works as an SOFC thereby oxidizing the metal (discharging the battery). First results from storage material development and stack testing are presented.

Titanium Carbide and Carbide‐Derived Carbon Composite Nanofibers by Electrospinning of Ti‐Resin Precursor

AbstractTiO2/C and TiC/C composite nanofibers were produced by electrospinning of resin/TiCl4 precursor solution. The resulting ceramic fiber webs were porous and showed surface areas as high as 523 m2g–1. They were further converted to carbide‐derived carbon (CDC) fibers under full retention of the fiber‐like shape and flexibility. These CDC membranes showed a hierarchical pore structure and specific surface as high as 1378 m2g–1. Applications in the area of high temperature filtration, catalyst support and energy storage are conceivable.

Supercapacitor Operating At 200 Degrees Celsius

The operating temperatures of current electrochemical energy storage devices are limited due to electrolyte degradation and separator instability at higher temperatures. Here we demonstrate that a tailored mixture of materials can facilitate operation of supercapacitors at record temperatures, as high as 200°C. Composite electrolyte/separator structures made from naturally occurring clay and room temperature ionic liquids, with graphitic carbon electrodes, show stable supercapacitor performance at 200°C with good cyclic stability. Free standing films of such high temperature composite electrolyte systems can become versatile functional membranes in several high temperature energy conversion and storage applications.

Flexible Glass for High Temperature Energy Storage Capacitors

Through the rolled-up glass: We demonstrate an alkali-free glass (• in figure) with high permittivity, low dielectric loss, high energy density, and potential self-healing capabilities that significantly performs better for high temperature–high power capacitor applications prepared through a standard roll-to-roll process than currently used polymer films (shown for comparison). As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Heat transfer analysis of encapsulated phase change material for thermal energy storage

Transient two dimensional heat transfer analysis is conducted to investigate a high temperature energy storage using encapsulated phase change materials (EPCMs) for concentrated solar power applications. The phase change material (PCM) considered is the NaNO3 encapsulated by a stainless steel in a cylindrical shaped capsule (or tube). Energy storage/retrieval into/from various sizes of EPCM capsules is simulated for both laminar and turbulent flow conditions of the heat transfer fluid (HTF) by an accurate modeling of the propagating liquid/solid interface in a PCM. Numerical simulations are conducted by employing a front-tracking method and an enthalpy–porosity approach. The results predicted by the two methods agree well. A two-dimensional cylindrical shaped EPCM capsule or tube is considered in simulations using gas (air) and liquid (Therminol/VP-1) as heat transfer fluids in a cross flow and an axial flow arrangement. The energy storage/retrieval times into/out of the EPCM capsule is dictated by the surface heat transfer of the EPCM for the capsule sizes considered in this study. A single horizontally placed rod in a channel with different blockage ratios for laminar and turbulence flows of HTF is studied in the present paper. It is illustrated by the present work that enthalpy-porosity method can be applied to simulate heat transfer at the capsule level and the system level. System level storage module is a thermocline that includes an arrangement of several EPCMs for several megawatts of thermal energy storage (TES) for several hours used in concentrated solar power applications and other industrial thermal systems.

Circulating fluidized bed heat recovery/storage and its potential to use coated phase-change-material (PCM) particles

Within the thermal energy capture and/or storage systems currently available or investigated, PCMs are the sole latent heat stores. Despite their low thermal conductivity, that limits charging and discharging times, the higher energy storage capacity per unit weight in comparison with sensible heat stores, makes them increasingly attractive for high temperature applications, resulting in reduced storage volumes and required circulation rates within the heat collector. The present paper introduces these PCMs, and their potential application in high temperature energy capture and storage, using a circulating fluidized bed (CFB) as transfer/storage mode. Thermal considerations determine the optimum size range for the applied particles (<400μm). The heat transfer from the wall of the CFB to the flowing gas–solid suspension is a major design parameter of the collector, and studied for different operating conditions as determined by the gas velocity and solids circulation flux. Measured values of the heat transfer coefficients are discussed, and compared with empirical predictions of Molodtsof–Muzyka, and Gorliz–Grace. Fair agreement is obtained only when the empirical parameters are carefully predicted. The application of a packet renewal mechanism at the wall is also investigated, with a fair prediction of the heat transfer coefficient in terms of the expected solid contact time at the wall.

Concentrating Solar Thermal Heat Storage Using Metal Hydrides

Increased reliance on solar energy conversion technologies will necessarily constitute a major plank of any forward global energy supply strategy. It is possible that solar photovoltaic (PV) technology and concentrating solar thermal (CST) power technology will play roughly equal, but complementary roles by 2050. The ability to increase reliance on CST power technology during this period, however, will be constrained by a number of factors: the large plant sizes dictated by economies of scale, the high associated transmission infrastructure investment cost, and the limitations of current thermal energy storage technologies. Thus, solar technology's main midterm role is seen to be as hybrid solar thermal power plant. The development of low-cost, high-temperature, high-energy density thermal energy storage systems is needed to enable CST plants to be dispatchable and accelerate the deployment of this technology. Thermochemical storage has the best potential to achieve these energy storage requirements and a brief overview of thermochemical energy storage options for CST plants points to high-temperature metal-hydride thermochemical heat energy storage systems. Hydrogen storage systems offer the highest energy storage capacity per volume and are therefore the most likely candidates for achieving the goal of fully dispatchable CST plants. A number of high-temperature metal-hydride thermochemical solar energy storage systems have been proposed and a small number of these systems are currently being investigated and developed. A key component of this work is matching the thermochemical metal-hydride system with a suitable “low-temperature” hydrogen storage material to produce systems that are self-regulating. A summary of the development status of these systems suggests that, despite the technical challenges associated with high-temperature thermochemical energy storage systems, their potential advantages are now seeing development occurring. Although in the early stages, their commercialisation could be fast tracked.

Fundamental Study on Saving Energy for Electrified Railway System Applying High Temperature Superconductor Motor and Energy Storage System

Induction motor instead of dc one has been applied widely for dc electric rolling stock because of the advantage of its utility and efficiency. However, further improvement of motor characteristics will be required to realize environment-friendly dc railway system in the future. It is important to study more efficient machine applying dc electric rolling stock for next generation high performance system. On the other hand, the methods to reuse regenerative energy produced by motors effectively are also important. Therefore, we carried out fundamental study on saving energy for electrified railway system. For the first step, we introduced the energy storage system applying electric double-layer capacitors (EDLC), and its control system. And then, we tried to obtain the specification of high temperature superconductor induction/synchronous motor (HTS-ISM), which performance is similar with that of the conventional induction motors. Furthermore, we tried to evaluate an electrified railway system applying energy storage system and HTS-ISM based on simulation. We succeeded in showing the effectiveness of the introductions of energy storage system and HTS-ISM in DC electrified railway system.

High-Temperature Poly(phthalazinone ether ketone) Thin Films for Dielectric Energy Storage

The synthesis and characterization of poly(phthalazinone ether ketone) (PPEK) for high-temperature electric energy storage applications is described. It was found that PPEK displayed excellent stability of the dielectric properties over a broad frequency and temperature range. Little change in the breakdown field and discharge time has been observed in PPEK with the increase of temperature up to 190 degrees C. A linear correlation between the AC conductance and the angular frequency implied that the hopping as a dominant conduction process contributed to the dielectric loss. Superior energy densities, remarkable breakdown strengths, and fast discharge speeds have been demonstrated in PPEK at various temperatures.