Combined Energy Storage Research Articles

Review of the Topology and Energy Management Hybrid Energy Storage on Electric Vehicle

There are several ways to improve the mileage of the electric vehicle (EV). High-efficiency drivetrain and high energy density are the main factors. Energy storage source for EV obtained from the battery, ultra-capacitor (UC) and fuel cells (FC). Each of that has own characteristics and capacity. The battery has a good energy density, UC and FC are superiors on power density. Combining some of the energy storage will improve performance and mileage. On this paper, the topology of combining energy storage are reviewed. In addition, also review the power management strategy of hybrid energy storage. By using a convenient strategy, hybrid energy storage becomes very worth.

Carbon nitride nanotube for ion transport based photo-rechargeable electric energy storage

To resolve the fluctuation and storage issues renewable energy is facing, photo-rechargeable electric energy storage systems may contribute by immediately storing the generated electricity locally. Complementing the various conventional chemical-reaction-based photo-rechargeable electric energy storage systems, we propose here a physical ion transport-based photo-rechargeable electric energy storage system to harvest solar energy and then store it in place as ionic power, which can be reconverted into electric energy later but momentarily. The new solar energy conversion and storage approach is based on a carbon nitride nanotube membrane, which can be fabricated by chemical vapor deposition method. The charging and discharging current peaks can reach to 1.8 μA/cm2, which can be scaled up through parallel (current) and series (voltage) connections. Our findings provide possibilities in advancing the design principles for a combined, easy and efficient solar energy conversion and storage system.

Combined energy storage and methane bioelectrosynthesis from carbon dioxide in a microbial electrosynthesis system

This study demonstrates a novel approach for combined energy carrier production and energy storage in a Microbial Electrosynthesis System (MES). Continuous production of high purity methane (CH4) from carbon dioxide (CO2) was achieved in a 0.65 L carbon felt - filled cathode compartment of a membraneless MES. CH4 production reached 0.72 L d−1 at an energy consumption of 26 Wh LCH4−1. Owing to the membraneless design of the MES, pH control of the electrode compartments was not required, with the cathode compartment pH remaining below 8.5. Electrochemical characterization showed a progressive increase of the MES internal capacitance from 2.1 F to 3.2 F. Bioelectrochemical conversion of CO2 to CH4 can be used for long-term energy storage (power-to-gas conversion) combined with CO2 sequestration, while the internal capacitance of electroactive biofilms can be exploited to develop bioelectrochemical supercapacitors for fast energy return to the electrical grid.

Ultra-thick battery electrodes for high gravimetric and volumetric energy density Li-ion batteries

Lithium-ion batteries, already capable of addressing the requirements of electric vehicles and renewable electricity storage, will be in the focus for the next decade. However, the transition from the small batteries for portable electronic to ultra-high capacity batteries requires safety improvements and cost-cutting efforts. Intensive research has been performed in the last three decades to optimize specific and volumetric capacity of electrodes. Recently the attention is focusing on increasing the electrodes areal capacity to enable the substantial reduction of the current collectors, porous separator, and electrolyte resulting in large gravimetric and volumetric energy density improvements as well as cost savings. Here we propose a lithium-ion battery based on thick, additive-free ceramic negative and positive electrodes, i.e. LTO (Li4Ti5O12) and LFP (LiFePO4), obtained by a solvent-free technology called powder extrusion moulding. Against all odds, the LTO/LFP cell based on these thick ceramic electrodes (areal capacity of 13.3 mA h cm−2) achieved the very high energy of about 23.9 mW h cm−2. Such an excellent performance, achieved simulating a typical day-night charge/discharge cycle, opens the way for the deployment of low cost, effective household (and small industry) energy storage in combination with photovoltaic energy harvesting.

Polyaniline nanoparticle coated graphene oxide composite nanoflakes for bifunctional multicolor electrochromic and supercapacitor applications

Graphene oxide (GO)/polyaniline (PANI) composite nanoflakes were fabricated by chemical oxidative polymerization of aniline onto GO nanoflakes. The electrochromic properties and the electrochemical capacitive behaviors of the GO/PANI composite nanoflake film were investigated. The GO/PANI nanocomposite film exhibits excellent electrochromic and supercapacitive performances. In comparison with neat PANI film, the GO/PANI composite nanoflake film shows larger optical modulation, faster response speed, larger coloration efficiency and better cycling stability. Moreover, an areal capacitance of (137 mF/cm2) is obtained for GO/PANI nanoflake film at a scanning rate of 5 mV/s, higher than that of neat PANI film (36 mF/cm2). The GO/PANI composite nanoflake film also shows enhanced electrochromic and supercapacitive durability. And the electrochromism also could be utilized as an indicator for the capacitance. The high-performance GO/PANI nanocomposite film shows promising features for multifunctional devices combining energy storage and electrochromism.

Thermal and economic evaluation of thermocline combined sensible-latent heat thermal energy storage system for medium temperature applications

In the current work a new thermocline combined sensible-latent heat thermal energy storage configuration is proposed as an alternative to the currently used thermal storage systems; containing solid rod structures of cheap naturally occurring material with phase change material capsules impregnated between the rods. An energy balance method coupled with an enthalpy based technique are used to develop a comprehensive transient numerical model. The numerical simulations are performed to compare the performance and the cost of the three types of thermal energy storage systems. The three thermal energy storage systems are; sensible rod structure, encapsulated phase change material and combined sensible-latent heat. The influence of different evaluation indexes on economic feasibility and the performance of thermal energy storage such as capital cost, capacity cost per kWh, axial temperature distribution, pumping work, thermocline degradation, effective discharging time and effective discharging efficiency; are analyzed. The results show that effective discharging efficiency and capacity costs for encapsulated phase change material, combined sensible-latent heat, sensible rod structure are 95%, 87%, 76% and $42/kWh, $37/kWh, $35/kWh, respectively. Moreover, the hybrid configuration exhibits a storage capacity of 78.5 kWh/m3, which is 26% higher than sensible rod structure and 22% lower than encapsulated phase change material configuration. The results of the comparative study indicate that the combined sensible-latent heat TES system seems to be a more viable option among the considered configurations due to its optimized performance and comparatively low cost. Also due to the reasons that thermal ratcheting of the storage tank is avoided and it provides stable fluid outlet temperature.

The nature of combining energy storage applications for residential battery technology

Batteries are expected to play an important role in the transition to decarbonised energy systems by enabling the further penetration of renewable energy technologies while assuring grid stability. However, their hitherto high capital costs is a key barrier for their further deployment. In order to improve their economic viability, batteries could provide several applications offering revenues. The techno-economic evaluation of batteries simultaneously serving several applications has proven to be challenging due to the trade-offs between energy and power applications. Focusing on residential batteries, we develop an optimisation method for designing optimal value propositions and we test it for four different applications both individually and jointly: PV self-consumption, demand load-shifting, avoidance of PV curtailment and demand peak shaving. Our results show that the combination of all applications currently helps batteries to get closer to profitability, from a net present value (NPV) per unit of capital expenditure (CAPEX) of −0.63 ± 0.04 for PV self-consumption only to −0.36 ± 0.10, with the combination of demand peak-shaving and PV self-consumption adding most value (0.21 ± 0.04). We also find that the annual household’s electricity consumption determines the value of energy storage applications. The proposed method allow us to classify storage applications as complementary and substitutive depending on whether their combined application increases their economic attractiveness or not. These results thus offer valuable insight for stakeholders interested in the deployment of energy storage in combination with energy efficiency, heat pumps and electric vehicles such as consumers, utility companies and policy makers.

Using electrical energy storage in residential buildings – Sizing of battery and photovoltaic panels based on electricity cost optimization

The popularity of small-scale residential energy production using photovoltaic power generation is predicted to increase. Self-production of electricity for self-consumption has become profitable mainly because of high-distribution costs and taxes imposed by the service providers on commercially produced electricity or because of the subsidies which reduce installation costs. Electrical energy storage can be used to increase the self-consumption potential of photovoltaic power. Additionally, electrical energy storage can lead to other benefits such as demand response or avoiding high load peaks. In this study, the profitability and sizing of a photovoltaic system with an associated electrical energy storage are analyzed from an economic perspective. The novel theory of sizing for profitability is presented and demonstrated using case studies of an apartment building and detached houses in Finland. To maximize the benefits, several alternative models for electricity metering and pricing are used and compared. The results demonstrated that the optimal size of the photovoltaic system could be increased by using electrical energy storage and suitable electricity pricing. This could lead to an increasing amount of photovoltaic production in the residential sector. Additionally, it is possible that when all the incentives are taken into account, electrical energy storage in combination with photovoltaic power generation would be more profitable than photovoltaic power generation alone. Photovoltaic power generation also increased the profitability of electrical energy storage, which could mean that the implementation of electrical energy storage in the residential sector could likewise increase.

Numerical characterization of thermocline behaviour of combined sensible-latent heat storage tank using brick manganese rod structure impregnated with PCM capsules

Efficient medium temperature thermal energy storage (TES) can help to eliminate the imbalance between energy demand and supply. In this study the issue of thermal ratcheting in TES system is avoided by using structured sensible heat storage material. Another technical issue of temperature drops at the end of discharging cycles occurring in only sensible material filled TES is overcome to some extent by using phase change material (PCM) between sensible rod structure (SRS) providing stable fluid outlet temperature. A comprehensive transient numerical model is formulated by solving separate equations for heat transfer fluid and storage materials using energy balance method coupled with enthalpy technique to study the influence of phase change temperature in the PCM. The numerical model predicts thermal stratification behaviour and thermocline formation along the symmetry-axis. A detailed parametric analysis of the combined sensible-latent heat thermal energy storage is performed to investigate the effect of porosity variation, inlet velocity and feature size of sensible heat storage material on total energy utilization, effective discharging efficiency and effective discharging time using thermocline characterization. The results indicate that discharging efficiency of hybrid TES tank can be increased by using lower velocity of fluid at inlet, by decreasing porosity or by using reduced SRS feature size. The study offers suggestions for optimized design and governing parameters of a new type of combined sensible-latent heat TES configuration, while avoiding thermal ratcheting with stable fluid outlet temperature for an application specific process.

Dynamic modeling and simulation of a heat pump system for enhancing cycle flexibility

This paper presents a dynamic simulation of a heat pump using butane refrigerant for the purpose of integration with a combined cycle power system and thermal energy storage to enhance flexibility. A dynamic model of a heat pump system is developed using the Amesim software and the simulation result in the case of changing the heat source and heat sink conditions is shown to validate the simulation performance.

Techno-economic analysis of micro fuel cell cogeneration and storage in Germany

In this paper, the effectiveness of support schemes for micro fuel cells in Germany is analyzed with regard to the latest market conditions, technical characteristics, and legislative changes. To this end, a dynamic model is used and applied to high-resolution household demand data. Specifically, we scrutinize whether polymer electrolyte membrane fuel cells are now a feasible investment option for residential usage in Germany or are likely to become so soon. Furthermore, we investigate whether electric energy storage could be a useful extension to the domestic fuel cell system by supplying short-term peak demand, and thus increasing self-consumption and potentially the overall economic merit. We find that the fuel cell technology analyzed is unlikely to become cost-competitive by 2020, and it may take quite some time to achieve a substantial market diffusion. We conclude that for the time being, electric energy storage in combination with a fuel cell system is not a worthwhile investment in a scenario where grid connection is assumed.

Optimal operation value of combined wind power and energy storage in multi-stage electricity markets

This paper provides a methodology to compute the optimal bidding by a wind power producer in a multi-stage market. The methodology is not restricted to the two-stage markets often reported in the literature—a day-ahead bid submission followed by an adjustment in the imbalance market. Instead, it allows studying any number of markets operating on the same dispatch hour. Particularly, this paper analyzes part of the Spanish market, covering the day-ahead, the six intraday, and the imbalance market. They are markets with different schedules, but this paper shows that by simply rearranging the market prices into a single equivalent market and employing the increments of power as bids, the calculations are visibly simplified; despite the different scope and gate closures. The methodology also includes a dynamic programming approach that relies on the equivalent market data to provide an optimal bidding sequence and its economic value when (i) uncertain prices and wind power production are considered, and (ii) energy storage is employed. As an application, the proposed methodology is employed to analyze the revenues derived by a wind power producer using ESS in the Spanish market.

Molten salt chemistry in nitrate salt storage systems: Linking experiments and modeling

Sensible heat storage in molten nitrate salts is a key technology when it comes to thermal energy storage in combination with concentrating solar power (CSP) plants. Currently, a mixture of sodium and potassium nitrate called Solar Salt is used at temperatures between 280 and 560 °C. Our research approaches comprise an improvement of Solar Salt stability at temperatures above 560 °C, which comes along with a broadening of the operating temperature range. In this way, a higher storage capacity and efficiency, as well as economic advances can be achieved. Numerous publications about the chemistry of molten nitrate salt mixtures reveal the formation of chemical species such as nitrite ions, nitrous gases and oxide ions and carbonate ions. Among these, the reversible reaction of nitrate to nitrite with release of oxygen is the predominant reaction at temperatures below 560 °C. So far, there is a lack of literature that pays particular attention on the contributions of reaction kinetics and mass transport effects on the reaction velocity of the nitrate/nitrite-reaction. However, understanding of these physico-chemical phenomena is essential, because further decomposition reactions build on the nitrate/nitrite-reaction. In this study, experiments at different scales (50 mg to 100 g) are compared with regard to the reduction reaction velocity at 500 °C. A data treatment procedure for thermogravimetric analysis experiments successfully eliminates effects of salt evaporation on the measured mass changes. The chemical equilibrium of the salt samples turned out to be reasonable, when compared to literature values. It was found, that the surface-to-volume ratio of the salt melt samples significantly affects the evaporation rates and the reaction velocity. The time period that is needed until chemical equilibrium is reached at 500 °C clearly increases when the surface-to-volume ratio decreases. The thermogravimetric analysis apparatus enables experiments, which measure reaction kinetics without mass transport limitations. It is demonstrated that a simulation model adapted from literature displays a reaction velocity that incorporates both reaction kinetics and mass transport without differentiation of the two phenomena.

Economic evaluation of a PV combined energy storage charging station based on cost estimation of second-use batteries

Recycling of a large number of retired electric vehicle batteries has caused a certain impact on the environmental problems in China. In term of the necessity of the re-use of retired electric vehicle battery and the capacity allocation of photovoltaic (PV) combined energy storage stations, this paper presents a method of economic estimation for a PV charging station based on the utilization of retired electric vehicle batteries. According to the second-use battery technology, a capacity allocation model of a PV combined energy storage charging station based on the cost estimation is established, taking the maximum net income of the PV combined energy storage charging station as the objective function, the real-time power balance of the PV combined energy storage charging station and the state of charge (SOC) of the energy storage system as constraint conditions. As the economy of the second-use battery energy storage system is related to the purchase, operation and maintenance costs of the energy storage system, the capacity cost of the retired electric vehicle batteries is estimated by the double declining balance method. In order to facilitate comparative analysis, the optimal capacity configuration of the PV combined energy storage charging station is given by the teaching-learning-based optimization (TLBO) and particle swarm optimization (PSO) algorithms respectively. The net present value (NPV) is adopted to evaluate the cost and benefit of the PV charging station with the second-use battery energy storage during the lifecycle. Combined with the actual operation data of the PV combined energy storage charging station in Beijing, the economy of the PV combined energy storage charging station is evaluated according to the conventional batteries and the second-use batteries. The simulation results show that the optimal capacity configuration obtained by the TLBO algorithm is better than that of the conventional batteries obtained by the PSO algorithm, which provides a theory basic for the re-use of the retired electric vehicle batteries and has a certain practical value of the project.

Optimal Sizing and Control Strategies for Hybrid Storage System as Limited by Grid Frequency Deviations

Frequency deviations of power systems caused by grid-connected wind power fluctuations is one of the key factors which restrains the increase of wind penetration level. This paper examines a combined wind and hybrid energy storage system (HESS, supercapacitor, and battery) to smooth wind power fluctuations. A fuzzy-based wind-HESS system (FWHS) controller is proposed to suppress the wind power fluctuations. The proposed controller takes full advantage of the complimentary characteristics of the supercapacitor and battery with the supercapacitor and battery in charge of high and middle frequency components of wind fluctuations, respectively. A differential evolution (DE)-based optimal sizing method for HESS systems is introduced to evaluate the minimum capacity of HESS as being limited by grid frequency deviation. The efficiency of the proposed scheme in the paper for wind-HESS system is evaluated by a real Chinese power system.

Equilibrium and kinetic aspects for catalytic methanation focusing on CO2 derived Substitute Natural Gas (SNG)

The production of Substitute Natural Gas (SNG) can be a key component of indigenous energy supply towards a low carbon future. In the present work, state of the art catalytic processes for SNG production based on CO and CO2 methanation are presented. Equilibrium based simulations are performed for both CO and CO2 methanation in order to define the optimum process parameters. A special focus is given on SNG derived from CO2 and hydrogen via power to gas process, which combines energy storage, Carbon Capture and Utilisation (CCU) with SNG production. Three kinetic models for CO2 methanation at 10 atm, 17 atm and 20 atm from the literature are compared. The quality of SNG produced is evaluated depending on the different operating pressure and temperature of CO2 derived SNG process. Low pressure bulk methanation (< 20 atm) cannot meet today's grid specifications without any additional measures taken such as blending with fossil natural gas or additional process equipment. Although heating value and Wobbe Index can be fulfilled, the maximum allowed hydrogen content remains a critical issue. Optimum process scheme and conditions for a dry hydrogen mole fraction lower than 2%vol in the final SNG are presented.

Theoretical investigation on energy storage characteristics of a solar liquid desiccant air conditioning system in Egypt

This work presents theoretical study of a standalone outdoor liquid desiccant air conditioning (LDAC) system assisted by solar energy. The liquid desiccant dehumidification cycle was integrated with a double indirect evaporative air cooler and a regenerative air heat recovery. The double indirect evaporative air cooler was used to recover heat from the return air, while air-air heat exchanger was used to recover heat from air leaving the regenerator. A water-in-glass evacuated tube solar collector was used to supply the system with solar heat. The remaining required heat is provided by natural gas fired boiler. The system was simulated by transient model under thermal energy storage, thermochemical energy storage and combined thermal and thermochemical energy storage modes.The theoretical results show that the mean daily thermal coefficient of performance (TCOP) is a strong function of the difference between absolute humidity ratio of outdoor air and saturated air. Results also show that, each tube of solar collector can deliver 30-Watt to operate the LDAC system under thermal energy storage mode for 16 h daily. While in the LDAC system under thermochemical energy storage mode, each tube would deliver 38.5-Watt for 16 h operation.It has been found that, to rise the solar fraction from 90% to 100% in the thermal energy storage mode, the required size of tubes array will be increased by 20%. Also, an analysis was carried out on the TCOP and required storage volume of the different energy storage modes. It shows that the combined energy storage method is the most energy efficient method.Finally, life cycle cost analysis (LCCA) was carried out for the LDAC system using various types of energy storage modes. The comparison indicated that 90% solar fraction LDAC system is the most economic system related to unit prices of solar collector and gas prices in Egypt. The total annual cost for the 90% solar assisted LDAC system is found to be lower than that of a vapor compression cycle (VCC) by about 50.5%. At the second order, the thermal energy storage mode by 49%. On the other side, the thermochemical energy storage mode is the least cost saving energy storage mode.

Polyaniline films with modified nanostructure for bifunctional flexible multicolor electrochromic and supercapacitor applications

The flexible polyaniline (PANI) thin films with modified nanostructure are prepared on flexible indium tin oxide (ITO)/polyethylene terephthalate (PET) substrates by combination of galvanostatic and cyclic voltammetric electrodeposition techniques. The electrochemical properties of as-prepared PANI nanomaterials are investigated by using the PANI film as an active material of the electrode for primary electrochromic device and electrochemical supercapacitor. This film presents a remarkable mechanical flexibility, high coloration efficiency of 80.9 cm2 C−1 at 630 nm and noticeable multicolor performances with reversible color change of transparent, pale yellow, green, blue and blue-purple. Further, a smart supercapacitor is presented, and the level of energy storage can be monitored by the change of optical performance. The film displays the highest specific capacitance of 473.3 F g−1 at the scan rate of 0.03 V s−1. The high-performance PNAI film exhibits promising features for various emerging flexible and multicolor electronics and optoelectronic devices combining energy storage and electrochromism.

Analysis and Efficiency Assessment of Direct Conversion of Wind Energy Into Heat Using Electromagnetic Induction and Thermal Energy Storage

This study deals with thermodynamic analyses of an integrated wind thermal energy storage (WTES) system. The thermodynamic analyses of the proposed system are performed through energy and exergy approaches, and the energy and exergy efficiencies of the components in the system and overall system are determined and assessed. The magnitudes of irreversibilities are determined, and the impacts of different parameters on the performance of the system are identified. The overall energy and exergy efficiencies of the proposed system and its subsystems are computed as well. The energy and exergy efficiencies of the overall system are defined and obtained as 7.0% and 8.6%, respectively. WTES plants with combined molten salt energy storage application can run continuously, and can provide electrical power for both on-grid and off-grid systems. By converting the wind power into a permanent energy source, the WTES offers a practical solution that can meet the electrical demand of the regions where the climate conditions are feasible for consistent, environmentally benign and cost-effective electric power, and it can be considered as a potential energy solution.

Rule Based Coordinated Control of Domestic Combined Micro-CHP and Energy Storage System for Optimal Daily Cost

This paper presents a novel control algorithm for optimising operational costs of a combined domestic micro-CHP (combined heat and power), battery and heat storage system. Using a minute by minute basic time-step, this work proposes a simple and computationally efficient rule based whole-system management, developed from empirical study of realistic simulated domestic electricity and heat loads. The CHP availability is considered in two binary states which, together with leveraging storage effectively, maximises CHP efficiency, and gives the algorithm increased real world feasibility. In addition, a novel application of a dual battery system is proposed to support the micro-CHP with each battery supplying just one of the distinctive morning and evening electrical load peaks, and thus inherently improving overall battery system lifetime. A case study is presented where the algorithm is shown to yield approximately 23% energy cost savings above the base case, almost 3% higher savings than that of the closest previous work, and 96.8% of the theoretical minimum cost. In general, the algorithm is shown to always yield better than 88% of the theoretical minimum cost, a ratio that will be considerably higher when real-world CHP limitations are factored into the theoretical minimum calculation.