Showing papers in "Journal of energy storage in 2017"

Engineering aspects of the design, construction and performance of modular redox flow batteries for energy storage

Abstract: Despite many studies and several extensive reviews of redox flow batteries (RFBs) over the last three decades, information on engineering aspects is scarce, which hinders progress with scale-up and implementation of this energy storage technology. This review summarises cell design requirements then critically considers design, construction and cell features together with their benefits and problems, leading to good practice through improved cell performance, knowledge and experience. Techniques for the characterisation of the reaction environment are illustrated by measurements of mass transport to (and from) electrode surfaces as a function of flow conditions, as well as pressure drop and electrolyte flow dispersion. The influence of design features on performance is illustrated by the effect of process conditions on the components of cell potential. Adequate attention to engineering aspects is seen to be critical to the effective performance of RFBs, particularly during scale-up and long-term operation. Techniques for the characterisation of reaction environment are summarised and a list of essential design and construction factors is provided. Finally, critical areas needing research and development are highlighted.

Electrical energy storage in highly renewable European energy systems: Capacity requirements, spatial distribution, and storage dispatch

Abstract: One of the major challenges of renewable energy systems is the inherently limited dispatchability of power generators that rely on variable renewable energy (VRE) sources. To overcome this insufficient system flexibility, electrical energy storage (EES) is a promising option. The first contribution of our work is to address the role of EES in highly renewable energy systems in Europe. For this purpose, we apply the energy system model REMix which endogenously determines both capacity expansion and dispatch of all electricity generation as well as storage technologies. We derive an EES capacity of 206 GW and 30 TWh for a system with a renewable share of 89%, relative to the annual gross power generation. An extensive sensitivity analysis shows that EES requirements range from 126 GW and 16 TWh (endogenous grid expansion) to 272 GW and 54 TWh (low EES investment costs). As our second contribution, we show how the spatial distribution of EES capacity depends on the residual load, which—in turn—is influenced by regionally predominant VRE technologies and their temporal characteristics in terms of power generation. In this sense, frequent periods of high VRE excess require short-term EES, which naturally feature low power-related investment costs. In contrast, long-term EES with low energy-related costs are characteristic for regions where high amounts of surplus energy occur. This relationship furthermore underlines how EES capacity distribution is implicitly influenced by technical potentials for VRE expansion.

Experimental investigation of parametric cell-to-cell variation and correlation based on 1100 commercial lithium-ion cells

Abstract: In order to prevent battery modules from inhomogeneity during operation, the integrated battery cells should be matched. Therefore, the cell-to-cell variations of relevant cell parameters due to manufacturing tolerances need to be quantified. Regarding cell matching, three points are lacking in current literature: first, reported parameter analyses have either based their statistic analysis on a too small number of cells. Or, second, few different cell parameters have been considered – hence, it was not possible to discuss which parameter would be beneficial to be used for classification. Third, potentially sensible correlations between different cell parameters have not been determined and discussed adequately. This paper provides a unique combination of analysing multiple different cell parameters and discussing their correlation – both based on a large number of examined cells: we investigate the parametric cell-to-cell variation and correlation of 1100 commercial production fresh LiFePO4-graphite cells which originate from two batches. The cell parameters are experimentally determined by conducting DC check-up (CU)- and AC EIS-measurements under monitored temperature and relaxation conditions for all 1100 cells. The data is statistically analysed for 15 different parameters: different discharge capacities, different DC and AC impedances, the mass and mean temperature of the cells. The determined relative variation of capacity and impedance is small: 0.28% and 0.72% respectively, which corresponds to a variation ratio of 1:2.2. The variation of the cell impedance allows no conclusion about the variation of the cell capacity. From the results, we derive four major implications concerning recommended characterisation parameters for the development and modelling of battery modules as well as for the quality control during cell production. Our experimentally determined parametric variation values and drawn conclusions are valuable for model fittings and battery pack analyses which have up to now been based on assumptions about cell-to-cell variations. The data set for all 1100 cells and 15 parameters is provided as supplementary material [1] .

An overview of energy storage and its importance in Indian renewable energy sector: Part I – Technologies and Comparison

Abstract: Energy storage now a days is becoming an imperative part of renewable energy. With the massive growth of renewable energy sources, energy storage can play a substantial role in renewable energy integration in India. It is beneficial for entire supply chain mainly due to enhanced electric power quality, dependability and better grid stability. Thus, lowering renewable energy intermittency, with increased user-friendliness and accessibility of electrical energy in remote places and reduction in harmful emissions. This paper Part-I of two papers primarily presents an overview of the selected energy storage technologies like Pumped hydro energy storage, Compressed air energy storage, Battery energy storage, Flywheel, Supercapacitors, Hydrogen energy storage, Superconducting magnetic energy storage, and Thermal energy storage. It highlights driving factors for growing energy storage in India. A comprehensive comparison of various technical characteristics and features of these technologies is also discussed.

Investigations on latent heat storage materials for solar water and space heating applications

Abstract: The present study provides a thorough review on available latent heat storage materials (LHSMs) and their thermophysical properties for low temperature (25–80 °C) solar heating applications The applications are solar water and space heating The best LHSMs have been short-listed for the above applications based on the primary and secondary selection criteria Based on the above two criteria, it is found that lauric acid, palmitic acid, stearic acid, myristic acid, paraffin wax, sodium acetate trihydrate and an eutectic mixture of stearic acid and myristic acid (80:20 wt%) have a great potential to act as the best LHSM for solar water heating system, whereas, calcium chloride hexahydrate, n-eicosane, P116 wax, sodium sulfate decahydrate, disodium hydrogen phosphate dodecahydrate and lithium nitrate trihydrate are the best LHSMs for solar space heating The parameters affecting the life span of a LHSM, namely, thermal stability, corrosion, phase segregation and subcooling have been discussed in detail The present study also includes a list of commercially available LHSMs which can be employed for the solar water and space heating applications

Impact of battery degradation on energy arbitrage revenue of grid-level energy storage

Abstract: This study investigates the representation of battery degradation in grid level energy storage applications. In particular, we focus on energy arbitrage, as this is a potential future large-scale application of energy storage and there is limited existing research combining the modelling of battery degradation and energy storage arbitrage. We implement two different representations of battery degradation within an energy arbitrage model, and show that degradation has a strong impact on battery energy storage system (BESS) profitability. In a case study using historical electricity market prices from the MISO electricity market in the United States, we find that the achievable net present value (at an interest rate of 10%) for a battery system with a C-rate of 1C dropped from 358 $/kWh in the case considering no degradation to 194–314 $/kWh depending on the battery degradation model and assumptions for end of life (EOL) criteria. This corresponds to a reduction in revenue due to degradation in the 12–46% range. Moreover, we find that reducing the cycling of the battery via introducing a penalty cost in the objective function of the energy arbitrage optimization model can improve the profitability over the life of the BESS.

Demonstration of reusing electric vehicle battery for solar energy storage and demand side management

Abstract: This paper demonstrated reusing electric vehicle traction lithium ion batteries for solar energy time shifting and demand side management in a single family house. Batteries retired from electric vehicle usage retain 70% to 80% of their capacity and can be re-purposed as stationary storage system at reduced cost. However, they have mismatched aging conditions and unbalanced state-of-charge levels. Under typical series-parallel connection, the cells in a pack are prone to over charging or discharging due to deviated cycling conditions and misestimated states. The demonstrated battery management system included an extended Kalman filter based states estimator, enhanced current shunting, and protective circuitry to ensure system safety. One novel contribution was the introduction of a worst-difference state-of-charge estimation scheme for the battery pack, which places more computational resources on the battery cell of the worst health. The scheme provided satisfactory overall estimation accuracy and offered a method to optimize computational cost when large number of battery cells was integrated. In addition, a function was proposed to indicate the overall states of the entire energy storage system by aggregating the states of the battery cells within. Therefore, the energy management unit was able to dispatch the battery assembly as a unified pack. Three decision-table-based control strategies were demonstrated with objectives to maximize economic benefits, minimize grid energy consumption, or a balance of both. The data obtained from the demonstrating system located in Davis, CA showed that the battery energy storage system was able to successfully mitigate solar intermittency and energy demand fluctuation by charging from excess solar energy and discharging during the period of peak demand. It reduced daily grid energy consumption by 64%–100% and significantly improved solar penetration.

Optimizing PV and grid charging in combined applications to improve the profitability of residential batteries

Abstract: The energy storage market is growing exponentially and residential batteries are being deployed including in grid-connected housing, in order to increase on-site use of PV electricity, i.e. PV self-consumption. However, residential batteries have not reached economic profitability yet in most grid-connected situations, and alternative applications for residential batteries should be explored. This paper presents results from an economic optimization of the operation of a residential battery for two different applications, namely PV self-consumption and demand-load shifting under different dynamic tariff structures. A genetic algorithm was used to identify the optimal operation of the battery for both applications separately as well as combined, in order to investigate whether and under what circumstances the delivery of these two services can help to create an economic case. We find that the greatest monetary value per kWh of storage capacity installed is obtained when a battery is used for PV self-consumption under a single, flat tariff. Furthermore, adding demand-load shifting to the value proposition is economically attractive since it helps to minimize the levelized cost associated with battery storage. We also identify improvements needed for residential batteries to reach economic viability in Switzerland for both PV self-consumption and demand-load shifting, as for example, halving of capital expenditure of the battery system.

New proposed methodology for specific heat capacity determination of materials for thermal energy storage (TES) by DSC

Abstract: This study presents a methodology to determine the specific heat capacity (Cp) of materials for thermal energy storage (TES) by DSC. These materials have great energy storage capacities, and due to that, important heat flow fluctuations can be observed for each temperature differential, taking more time to reach a desired temperature gradient. Three different DSC methods are considered to be applied in the methodology, and are explained and compared in this study in order to select the most proper one for Cp determination. To perform this study, the Cp of three materials commonly used in sensible TES systems, slate, water, and potassium nitrate (KNO3), is determined. Excellent results with errors lower than 3% are obtained when using the proposed methodology with the areas method. Worse results are obtained with both dynamic and isostep methods, with errors up to 6% and 16% respectively, as a consequence of sensitivity problems during the measurements.

The role of storage technologies in energy transition pathways towards achieving a fully sustainable energy system for India

Abstract: In this work, a 100% renewable energy (RE) transition pathway based on an hourly resolved model till 2050 is simulated for India, covering demand by the power, desalination and non-energetic industrial gas sectors. Energy storage technologies: batteries, pumped hydro storage (PHS), adiabatic compressed air energy storage, thermal energy storage and power-to-gas technology are used in the modelling to provide flexibility to the system and balance demand. The optimisation for each time period (transition is modeled in 5 year steps) is carried out on an assumed costs and technological status of all energy technologies involved. Results indicate that a 100% renewable based energy system is achievable in 2050 with the levelised cost of electricity falling from a current level of 58 €/MWhe to 52 €/MWhe in 2050 in the power scenario. With large scale intermittent renewable energy sources in the system, the demand for storage technologies increases from the current level to 2050. Batteries provide 2596 TWh, PHS provides 12 TWh and gas storage provides 197 TWh of electricity to the total electricity demand. Most of the storage demand will be based on batteries, which provide as much as 42% of the total electricity demand. The synchronised discharging of batteries in the night time and charging of power-to-gas in the early summer and summer months reduces curtailment on the following day, and thus is a part of a least cost solution. The combination of solar photovoltaics (PV) and battery storage evolves as the low-cost backbone of Indian energy supply, resulting in 3.2–4.3 TWp of installed PV capacities, depending on the applied scenario in 2050. During the monsoon period, complementarity of storage technologies and the transmission grid help to achieve uninterrupted power supply. The above results clearly prove that renewable energy options are the most competitive and a least-cost solution for achieving a net zero emission energy system. This is the first study of its kind in full hourly resolution for India.

Evaluation of grid-level adaptability for stationary battery energy storage system applications in Europe

Abstract: This work discusses the grid-level suitability for stationary battery energy storage systems based on lithium ion technology in general, focusing on the integration of such systems in the low-voltage grid-level in Europe. The vast majority of recent research regarding stationary battery storage systems focuses on single-electricity-grid voltage levels, whereas the interaction of different electricity grid-levels has been widely neglected. Challenges in distribution grids mostly originate from the quantity of challenges in low-voltage grids, stationary battery energy storage systems that are operated in low-voltage grids may reduce these challenges. Therefore, this work investigates stationary battery energy storage systems installed in low-voltage grids and their effects on superimposed grid-levels. Simulation results show that grid challenges, addressed by battery storage systems in low-voltage grids, have positive multiplicative impacts on upper grid levels, reducing local grid demand and lowering power peak stress. A proposal is presented for a low-voltage grid battery storage system that can be operated to fulfill the aforementioned functionality and yield the benefits via a multi-purpose or multi-tasking battery storage system.

Real-world operating strategy and sensitivity analysis of frequency containment reserve provision with battery energy storage systems in the german market

Abstract: Large-scale battery energy storage systems (BESS) have become increasingly interesting to provide ancillary services for the electricity grid. Especially the German frequency containment reserve (FCR) market which is organized by the German transmission system operators (TSO) is attractive for BESS. Because of its importance for the system stability, FCR has to be provided continuously with 100% availability. Due to the limited energy capacity of BESS, an operating strategy is required to enable continuous FCR provision. The German TSOs have defined several requirements that BESS have to comply with as well as degrees of freedom (DoF) to enable corrective measures such as selective recharging for an operating strategy. This paper presents a sensitivity analysis of different operational parameters based on an operating strategy developed within the M5BAT (Modular Multi_Megawatt Multi-Technology Medium-Voltage Battery Energy Storage System) project. Within this project the construction and operation of a 5 MW hybrid BESS with five different battery technologies is realized. As this BESS will mainly be operated in the German FCR market, it is used as reference for this paper. The developed operating strategy considers the TSO’s FCR requirements and DoF and is fully applicable to the German FCR market. Within this paper it is explained how corrective measures have to be triggered in order to comply with the requirements. A model of the M5BAT BESS, which comprises various battery technologies and an energy management system (EMS) for load allocation among multiple battery strings, is introduced. Simulations of FCR operation with measured frequency data of the year 2014 are presented. The influence of the lead time and duration of corrective measures, the EMS and the FCR requirements on compliance with the FCR requirements, amount of corrective measures, resulting energy throughput, state-of-energy (SOE) distributions and cycle numbers are investigated. The results show a significant impact of all parameters. It is found that velocity and flexibility of corrective measures (e.g. recharging) and an efficient EMS are prerequisites for FCR operation with BESS under the applicable regulation. Additionally, the results indicate that the overall benefits of FCR provision with BESS could be improved with an adjustment of the requirements (30-min-criterion).

An overview of energy storage and its importance in Indian renewable energy sector: Part II – energy storage applications, benefits and market potential

Abstract: Energy storage is gaining importance in both conventional and renewable energy sector in India. Due to several applications and benefits, energy storage systems show huge potential in Indian renewable energy sector. This paper (Part II) mainly focuses on the energy storage market potential in India, its applications and benefits as well. Part I of the two papers, presented an overview of selected energy storage technologies with a comprehensive comparison of important characteristics and features. Whereas in this paper, applications and benefits of energy storage at various stages of energy systems is presented, along with prospects of energy storage market potential, key opportunities and recent developments in upcoming years in India. This work also highlights the current status of various energy storage projects across India and few of the challenges forbidding their large-scale deployment.

Eyring acceleration model for predicting calendar ageing of lithium-ion batteries

Abstract: Modelling of lithium-ion batteries calendar ageing is often based on a semi-empirical approach by using, for example the Arrhenius acceleration model. Our approach is based on Eyring acceleration model, which is not widely used for electrochemical energy storage components. Parameter identification is typically performed without taking into account the state-of-charge (SoC) drifting. However, even in rest condition, battery cells’ SoC drifts because of capacity losses (self-discharge and capacity fade). In this work we have taken into account the SoC drift during calendar ageing tests. For this, we considered available capacity (Ah) instead of SoC (%) as ageing factor. Then, the analytical solution of the problem leads to the use of the Lambert W function in the model formulation. Simulation results show that Lambert-Eyring model is more accurate and allows a reduction in the number of parameters to be identified.

Fast-charging to a partial state of charge in lithium-ion batteries: A comparative ageing study

Abstract: At electric vehicle fast-charging stations, it is generally recommended to avoid charging beyond similar to 80% State-of-Charge (SOC) since topping-off to full capacity disproportionately increases ...

Dynamic modeling and simulation of an Isobaric Adiabatic Compressed Air Energy Storage (IA-CAES) system

Abstract: This paper discusses the dynamic modeling of an innovative Isobaric Adiabatic Compressed Air Energy Storage (IA-CAES) system using “Dymola”. The system is a solution to reduce the effect of the intermittence of the renewable energy sources and thus improve the penetration of these sources into the energy mix. It also enables restoring the balance between supply and demand for electricity and supporting the electrical grid. The proposed system is characterized by the recovery of the compression heat and the storage of air under fixed pressure in order to improve its efficiency and its energy density. The dynamic model takes into account the mechanical inertia of the turbo-machinery as well as the thermal inertia of the heat exchangers and the storage tanks. This allows the model to evaluate the response time of the storage system and its ability to meet the power demand. Then, it allows studying the flexibility of the storage system by evaluating the durations of the transient states and the proposals to reduce these durations. The system efficiency is 53.6%. The results show that the time required to reach the steady state is about 120 s during storage periods and 382 s during production periods. In addition, the power consumed or produced by the storage system matches with the set point with maximum delay of 6 s and maximum relative error of 9%. The system is then able to reach the nominal power in few minutes (secondary reserve). Finally, a standby mode with minimal energy consumption is studied in order to reduce the durations of the transient states and then to be able to meet the primary reserve (by reaching 33% of the nominal power in 10 s). It consists in operating the compressor at 54% and the turbine at 72% of their nominal speeds.

Evaluation and performances comparison of calcium, strontium and barium carbonates during calcination/carbonation reactions for solar thermochemical energy storage

Abstract: The efficiency and economic competitiveness of thermal storage for concentrating solar power plant can be improved by increasing the operating temperature (above 600 °C). Thermochemical energy storage is an attractive way of efficiently storing high-temperature solar heat, in the form of chemical bonds as a stable and safe solid material, when compared with existing sensible and latent heat storage materials. Among the most interesting materials, BaCO3, CaCO3 and SrCO3 show high storage temperatures (typically above 800 °C), energy storage densities, and charging and discharging rates. Heat charge corresponds to the calcination (decarbonation) reaction of the carbonates (endothermal step) and heat discharge corresponds to the reverse carbonation of the oxides (exothermal step). A comparative thermodynamic and kinetic study of calcination and carbonation reactions involving commercial and synthesized CaCO3, SrCO3 and BaCO3 powders was performed for application in thermochemical energy storage. An experimental study based on thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) was conducted to study the decomposition and carbonation reactions and to determine the enthalpy of reaction for each metal carbonate. While complete calcination was achieved regardless of the metal carbonate involved, partial carbonation was observed with loss in CO2 capture capacity during cycling. The effect of the addition of a promoting agent such as magnesium oxide on thermal stability for improving chemical and structural cyclability of these three candidate carbonates was also investigated. Beneficial effect of MgO addition was demonstrated and noticeable performance stability was obtained in the case of SrCO3/SrO during successive energy storage cycles.

Influence of high intensive dry mixing and calendering on relative electrode resistivity determined via an advanced two point approach

Abstract: In order to achieve a profound understanding of the production process of electrodes for lithium-ion batteries, methods to determine the (intermediate) product quality are a necessity. Therefore, a new, fast and easy to use two point method to determine the relative resistivity of dry electrodes has been established. The method is used to determine process-induced changes in the electrode’s structure. A materials testing machine is used to ensure a homogeneous and constant mechanical stress during the analysis. By applying a direct current and measuring the voltage drop the electron transport characteristic along the whole electrode cross-section, taking all battery relevant resistances into account, can be determined. The result is an easy to compare relative resistivity value including coating resistance, contact resistance between coating and adhering current collector as well as the contact resistances between sample and probe. Process-induced changes are clearly visible in the results. The influence of the main testing parameters – contact stress and applied current – is determined. To cross-check the results, an established ‘powder probe’ method is used to confirm the relative resistivity changes caused by calendering. Slight calendering of LiNiMnCoO2 cathodes leads to an increase in electrode resistivity as conductive pathways are broken by the applied shear forces. However, increasing the cathode density to 2.95 g/cm3 decreases resistivity by one third compared to uncalendered electrodes by re-establishing and shortening electrical pathways. Furthermore, a relative resistivity of anodes produced with a high energy powder mixing step is measured and shows that applying too much stress to the carbon black leads to a loss in long range conductivity, resulting in electrodes with an increased resistivity of up to 50%.

Performance evaluation and optimization of encapsulated cascade PCM thermal storage

Abstract: One of the main components of any solar power plant is its thermal heat storage system. Heat storage reduces the cost of power generation by increasing the capacity factor of the system. This paper aims to model and optimize the operation of a consecutive multi-layer Phase Change Material (PCM) thermal heat storage system, named Cascade Latent Heat Storage (CLHS), using the method of characteristics and genetic algorithm. The model is validated through comparison with experimental data available in the literature. The model can predict fluid and PCM temperature, PCM phase and the energy absorbed by PCM. A sensitivity analysis is employed for both the PCM and the fluid parameters. The PCM types, placement, and quantity are optimized in two different cases. Optimization results in comparison with the best case of a Single-PCM storage show an improvement of the system performance. In the first case, the stored energy of a CLHS during a 4-h charge period is maximized by increasing 5.12%, while in the second case, the discharged energy maximized during an 8-h charge-discharge cycle by 5% increase. This achievement can outperform current storage systems capabilities in different applications such as building and solar power plants.

Preparation and thermal performance of methyl palmitate and lauric acid eutectic mixture as phase change material (PCM)

Abstract: A series of binary mixtures of Methyl Palmitate (MP) and Lauric Acid (LA) were prepared and investigated, aiming for potential phase change material (PCM) for thermal energy storage systems. The thermal analysis of the PCM binary mixtures was investigated by means of Differential Scanning Calorimetry (DSC). A theoretical and experimental determination of the eutectic mixture was established. The results indicated that the eutectic binary mixture of 60%MP and 40%LA has desirable properties of phase transition temperatures within the comfort temperature range (Tm = 25.6 °C, Tf = 20.2 °C) and high latent heat capacity (ΔHm = 205.4 J/g, ΔHf = 205.8 J/g). The paper experimentally studied the other important thermo-physical properties required for modelling and stimulating the PCM in any storage systems such as thermal conductivity, enthalpy curve, phase diagram, specific heat, thermal diffusivity, and density. The thermal stability test indicated that the eutectic mixture had reliable thermal performance upon thermal cycling. Based on all these results, the MP-LA eutectic mixture is a promising material for thermal energy storage.

Influence of zinc additive and pH on the electrochemical activities of β-nickel hydroxide materials and its applications in secondary batteries

Abstract: The importance of Ni-based batteries in the present context is extremely valuable, as their electrochemical properties are expected to offer significant insights into their application as battery materials. In this direction, Ni(OH) 2 has been prepared using the co-precipitation method by varying the concentrations of zinc additive (2, 4, 6 & 8 wt%) and pH (8, 9, 10 & 11). The results show that the prepared samples exist in β-phase with flake like structure. The electrochemical properties of b-Ni(OH) 2 have been investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements using a paste-type electrode on a nickel mesh as a current collector. The cyclic voltammetry measurements indicate that the reversibility of the electrode reaction increases at pH 10 and 6% Zn additive. Whereas, the EIS measurements reveal that a reduction in the charge transfer resistance increases the double layer capacitance of the nickel electrode.

Power-to-gas through CO2 methanation: Assessment of the carbon balance regarding EU directives

Abstract: The transformation of carbon dioxide (CO2) into fuels is receiving a growing attention from engineers, scientists and policy makers. For instance, CO2 and hydrogen produced with renewable electricity can be combined to provide methane (power-to-gas). This strategy could store temporary surpluses of renewable electricity, but the lack of accurate carbon balance makes it difficult to establish the regulatory status of the final product, particularly when CO2 is derived from fossil resources. This article describes an adapted methodology assessing the carbon balance of power-to-gas. The emissions of greenhouse gases per unit of energy have been calculated for different scenarios, varying the source of electricity and the origin of carbon dioxide. The methodology allows accounting for the energy contained in the initial fuel that provides the carbon dioxide. When the CO2 is derived from an industrial process (e.g. cement industry), the energy content of the final product has been estimated and accounted for. The results demonstrate that power-to-gas should use electricity surpluses as much as possible. Biogenic and atmospheric CO2 are the most interesting sources, but the utilization of fossil CO2 makes sense in given situations. Results also suggest that current EU directives on renewable energy are not perfectly suited to power-to-gas.

Evaluation of Electrical Energy Storage (EES) Technologies for Renewable Energy: A Case from the US Pacific Northwest

Abstract: Increase in use of renewable energy such as solar and wind has created challenges in balancing load. Renewable energy intermittency can be addressed with different solutions and technologies. Using Electric Energy Storage (EES) has been an approach which has been studied extensively in the recent years. This paper reviews the storage technologies leveraging both technical papers on technologies as well as other reviews of such technologies done by other researchers. The contribution of this paper is in two areas. First the use of a case study demonstrates how different approaches can address different challenges. Second contribution is the review of evaluation factors and methods of such technologies resulting in a proposed framework.

The suppression of lithium dendrite growth in lithium sulfur batteries: A review

Abstract: Lithium sulfur batteries (LSBs) are attractive owing to the high theoretical capacities of sulfur cathode active material (1672 mAh g−1) and lithium anode active material (3862 mAh g−1), which leads to a specific energy of approximately 2600 Wh kg−1. However, for any rechargeable batteries employing lithium metal as the anode, a major failure mechanism is uncontrolled dendrite formation, which presents serious safety issues, low Coulombic efficiency and poor cycle performance. Recently, researchers make great effort to overcome these problems. Here we summarize some methods for suppressing lithium dendrite growth based on the failure mechanism of LSBs, mainly including novel separator, anode modification and electrolyte modification. We also discuss the advantages and disadvantages of different methods and point out the challenges that still needed to be addressed for building better LSBs.

State-Of-Charge Evaluation Of Supercapacitors

Abstract: In the last years, energy storage systems are increasingly involved in applications in which they are required to deliver or adsorb significant charging or discharging currents in short intervals of time, typically a few seconds. Thanks to their high specific power, supercapacitors may represent one of the most promising technologies for this kind of applications. However, one of the main concerns regarding their operation is the accurate estimation of their state of charge; the most common technique, based on ampere-hour counting, typically requires some correction mechanisms, since it implies a significant loss of accuracy over time, due to the accumulation of measuring errors. In the present paper, a novel algorithm to assess the state of charge of supercapacitors is described and implemented. The algorithm is based on the evaluation of the parameters of an equivalent electric circuit of the supercapacitor, and on the consequent use of a Luenberger-style technique for the runtime evaluation of its state of charge, based on the measure of current and voltage at supercapacitor's terminals. The algorithm estimates the cell open circuit voltage while the current is highly variable, as typical in power-oriented applications, hence the corresponding state of charge.

The effect of external compressive loads on the cycle lifetime of lithium-ion pouch cells

Abstract: In application, lithium-ion pouch-format cells undergo expansion during cycling. To prevent contact loss between battery pack components and delamination and deformation during battery operation, compressive pressure is applied to cells in automotive battery modules/packs by way of rigid cell housing within the modules. In this paper, the impact of such compressive pressure on battery degradation is studied. Samples of commercial, 15 Ah LiNiMnCoO2/Graphite electrode pouch-type cells were cycled 1200 times under atmospheric, 5 psi and 15 psi compressive loads. After 1200 cycles, the capacity fade for 0, 5 and 15 psi loads was11.0%, 8.8% and 8.4%, respectively; the corresponding power fade was found to be 7.5%, 39% and 18%, respectively, indicating power fade peaks between 0 and 15psi. This contrasting behaviour is related to the wettability increase and separator creep within the cell after compressive load is applied. The opposing capacity fade and power fade results require consideration from automotive battery engineers at the design stage of modules and packs. In addition to capacity fade and power fade results, the study identified the evolution of compressive pressures over multiple cycles, showing that pressure increases with cycling.

Recent advances in layered double hydroxides as electrode materials for high-performance electrochemical energy storage devices

Abstract: As we are facing increasing challenges of diminishing fossil fuel and global warming, there is increasing interest in developing advanced and cost effective electrochemical energy storage devices for diverse applications including mobile power supply to portable electronics, electric vehicles (EVs) or hybrid EVs (HEVs). To this end, layered double hydroxides (LDHs) have gained considerable attention in the past decade as a unique class of electrode materials due to their multiple cations, flexible ion exchangeability and tunable compositions. With abundant slabs and electrochemically active sites, the LDHs can used to produce energy storage devices with both the double-layer capacitance and Faradaic pseudo-capacitance. In this review, we summarize and discuss recent progress in the synthesis of LDHs based materials for electrochemical energy storage devices including lithium ion batteries and electrochemical supercapacitors.

Compressed air energy storage integrated with floating photovoltaic plant

Abstract: Floating photovoltaic (FPV) systems are an emerging technology suitable for large plants, especially, on fresh water basins. We suggest integrating a CAES system to FPV using the pipes, necessary for the buoyancy of the modular raft structure, as a compressed air reservoir. The huge basin thermal inertia allows for an isothermal compression– expansion cycle, which promises high storage efficiency.

Pentaerythritol with alumina nano additives for thermal energy storage applications

Abstract: Pentaerythritol is a poly alcohol with high solid–solid phase change enthalpy that makes it suited for thermal energy storage applications. At solid–solid phase transition temperature, pentaerythritol change from body centered tetrahedral molecular structure into a homogeneous face-centered cubic crystalline structure accompanied with the absorption of the hydrogen bond energy. The present work investigates the effect of adding alumina (Al2O3) nanoparticles to pentaerythritol on thermal and chemical stability by performing thermal cycling test. Dispersion stability and aggregation of nanoparticles during thermal cycling were studied with FESEM and EDX analysis. The thermal and chemical stability of pentaerythritol samples added with alumina nanoparticles in the weight proportions 0.1%, 0.5% and 1% were tested using the characterization methods such as TGA, DSC and FTIR. The change in the specific heat and thermal conductivity of pentaerythritol was studied by the T-history method. The experimental results showed good thermal and chemical stability for alumina enhanced pentaerythritol subjected to 100 thermal cycles along with a negligible change in specific heat and thermal conductivity values. Non-isothermal crystallization kinetics of the PE added with alumina nanoparticles were also studied in this experimental work.

Electrochemical-electrical-thermal modeling of a pouch-type lithium ion battery: An application to optimize temperature distribution

Abstract: This paper presents an electrochemical-electrical-thermal coupled modeling approach for pouch-type lithium ion batteries. In the presented approach, simple and efficient analytical methods are applied to calculate the current density over the current collector and the localized heat generation rate of current collectors. The feasibility of this approach is validated with experimentation. A comprehensive simulation study on the impact of tab arrangements on the temperature distribution of pouch-type lithium ion batteries is conducted. The results demonstrate that symmetrical tab arrangements improve the uniformity of temperature distribution significantly, although they will lead to a very slight increment of the maximum temperature on the surface of pouch cell. Besides, placing the collecting tabs on the opposite sides or long side(s) of battery cell is helpful in lowering its maximum temperature and improving the uniformity of temperature distribution.