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Phase Change Materials (PCMs) are gaining importance in energy storage applications. However, many PCMs are poor thermal conductors and thus can benefit from the optimal use of appropriate fins. This work introduces a PCM-fin structure optimization framework. Typically, the non-linear solidification process increases the complexity associated with solving the mathematical equations for the PCM-fin structure optimization problem, making it computationally expensive. In this paper a modeling approach called Layered Thermal Resistance (LTR) model is extended and developed in 2D cylindrical geometry in order to enable efficient PCM-fin structure optimization. The finned LTR model represents the nonlinear transient solidification process by analytic equations. This significantly reduces the computational cost associated with optimization. A finned heat pipe structure modeled by the finned LTR approach is optimized based on minimizing cost while meeting operational requirements. The optimal results imply that thinner fins result in lower system cost and that there is a thickness limit for the fins to be economically welded on a heat pipe. The finned LTR model also gives the optimal cost of material usage for a large scale latent thermal energy storage system in terms of dollars per kilowatt and it was found that the system cost is slightly lower by using carbon-steel as the construction material for the heat pipes and fins than by using Al 6061. [ABSTRACT FROM AUTHOR]

Future electricity systems which plan to use large proportions of intermittent ( e.g. wind, solar or tidal generation) or inflexible ( e.g. nuclear, coal, etc. ) electricity generation sources require an increasing scale-up of energy storage to match the supply with hourly, daily and seasonal electricity demand profiles. Evaluation of how to meet this scale of energy storage has predominantly been based on the deployment of a handful of technologies including batteries, Pumped Hydroelectricity Storage, Compressed Air Energy Storage and Power-to-Gas. However, for technical, confidentiality and data availability reasons the majority of such analyses have been unable to properly consider and have therefore neglected the potential of Pumped Heat Energy Storage, which has thus not been benchmarked or considered in a much detail relative to competitive solutions. This paper presents an economic analysis of a Pumped Heat Energy Storage system using data obtained during the development of the world’s first grid-scale demonstrator project. A Pumped Heat Energy Storage system stores electricity in the form of thermal energy using a proprietary reversible heat pump (engine) by compressing and expanding gas. Two thermal storage tanks are used to store heat at the temperature of the hot and cold gas. Using the Levelised Cost of Storage method, the cost of stored electricity of a demonstration plant proved to be between 2.7 and 5.0 €ct/kW h, depending on the assumptions considered. The Levelised Cost of Storage of Pumped Heat Energy Storage was then compared to other energy storage technologies at 100 MW and 400 MW h scales. The results show that Pumped Heat Energy Storage is cost-competitive with Compressed Air Energy Storage systems and may be even cost-competitive with Pumped Hydroelectricity Storage with the additional advantage of full flexibility for location. As with all other technologies, the Levelised Cost of Storage proved strongly dependent on the number of storage cycles per year. The low specific cost per storage capacity of Pumped Heat Energy Storage indicated that the technology could also be a valid option for long-term storage, even though it was designed for short-term operation. Based on the resulting Levelised Cost of Storage, Pumped Heat Energy Storage should be considered a cost-effective solution for electricity storage. However, the analysis did highlight that the Levelised Cost of Storage of a Pumped Heat Energy Storage system is sensitive to assumptions on capital expenditure and round trip efficiencies, emphasising a need for further empirical evidence at grid-scale and detailed cost analysis. [ABSTRACT FROM AUTHOR]

For the energy management of the boost converter based battery/supercapacitor (SC) hybrid energy storage system (HESS) in electric vehicles, a robust current control should be achieved for the battery such that the battery safety can be guaranteed. In this paper, an estimator-based adaptive sliding-mode control (estimator-based ASMC) strategy is proposed for the current tracking control of the boost converter based battery/SC HESS. By considering the unmodeled dynamics of the SC and the unknown disturbances, the equivalent circuit and the state-space average model are established for the boost converter based battery/SC HESS. To achieve the current tracking control, a sliding surface is defined based on the estimated tracking current error. The average control factor is designed according to the sliding-mode control (SMC) strategy. Furthermore, the adaptation laws are designed based on the state observers and the Lyapunov function, which can be used to estimate the load variations and unknown external input voltage. Finally, the adaptive control factor is recalculated based on the estimator-based ASMC strategy. In practical application, a hysteresis control strategy and an average filter method are developed to guarantee the smooth SMC for the boost converter based battery/SC HESS. Simulations and experiments are established to verify the estimator-based ASMC strategy. Compared to the conventional total SMC (TSMC) and PI strategies, the estimator-based ASMC strategy has over 37% and 50% settling-time improvement of current adjustment to deal with the load variation, respectively. The estimator-based ASMC strategy can improve the operating stability of the boost converter based battery/SC HESS under different operating modes. The battery can provide a constant or optimal current to the load. Therefore, the boost converter based battery/SC HESS with the proposed estimator-based ASMC strategy can effectively ensure the system stability and extend the battery life, simultaneously. [ABSTRACT FROM AUTHOR]

The reduction of automotive fuel consumption and emissions remains one of the main challenges. This paper presents the potential fuel saving in a CNG-powertrain derived from the recovery of the main energy losses. The analysis includes the kinetic energy recovery by a belt starter generator (BSG), the exhaust gas waste heat recuperation by using in a cascade approach, a thermoelectric generator (TEG) and a turbo-generator (TBG)- and the electrification of the main auxiliaries. An additional 48 V board net as well as the addition of a storage system are also included in the study. To support on the design phase of the project and in the operation strategy, a dynamic model in Matlab/Simulink® has been used. The model includes all the new components/major changes required in the vehicle- experimentally validated-. It has been used on backward simulations for the ACEA long haul mission in order to maximize the vehicle’s efficiency. Estimations at rating point (600 Nm and 1200 rpm) result in an electric production up to 4 kW h and a fuel saving of 7.5%. The most convenient technologies in the ACEA cycle turns out to be the KERs followed by the TBG. [ABSTRACT FROM AUTHOR]

Electrical vehicles have the capability to lessen the severe threats of energy crisis and environment pollution. The Lithium ion battery as a promising solution for the energy storage in vehicular applications is briefly introduced in this paper. The adverse effects of improper temperature, including performance degradation, potential thermal runaway, temperature non-uniformity and low temperature performance are described afterwards. The thermal model, electrochemical model, equivalent circuit model and electrochemical/electrical-thermal coupling methods are also elaborated for the accurate battery modeling. More importantly, this review detailedly summarizes the progress on battery thermal management systems (BTMSs) including the air, liquid, boiling, heat pipe and solid-liquid phase change based strategies during recent years. Influence factors and development focus of different BTMSs are stated elaborately. Passive cooling systems utilizing the latent heat during the phase change process are more attractive options compared to the conventional single phase forced air and liquid cooling methods. However, there still exist some challenges to be addressed before commercializing. In addition, different methods could be combined to meet the requirements of various applications. The improvement of these existing BTMSs is supposed to be paid more attention to enhance Li-the performance and safety of Li-ion batteries. [ABSTRACT FROM AUTHOR]

The need to develop renewable heat sources for domestic space heating is a well known problem, for solar thermal systems mismatch between generation and load is a major issue, and thermochemical interseasonal heat storage offers a solution to this problem. Recent research has shown that using an absorbent material as a host for salt hydrates can be advantageous in achieving a high energy density material while alleviating the problematic practical characteristics, such as agglomeration, which salt hydrates typically possess. In this paper results are presented for a 13X molecular sieve which was tested to determine its potential for interseasonal domestic thermochemical energy storage alone and as a host material for Magnesium Sulfate (MgSO 4 ). Two different impregnation preparation methods have been utilised in our experiments, (i) a wetness impregnation method and (ii) a new method in which 13X molecular sieve powders and MgSO 4 are formed into pellets with use of a binder. The materials produced by each method were tested against each other and compared to a zeolite-Y material to assess which is the best candidate material for thermal energy storage. The impact of ion exchange on the energy storage potential of the 13X materials was also investigated. Analysis of the materials characteristics and thermal performance was conducted using a Differential Scanning Calorimeter (DSC), Thermogravimetric Analyser (TGA) coupled with a Residual Gas Analyser (RGA), Scanning Electron Microscope (SEM) with Energy Dispersive X-ray (EDX) spectroscopy and a custom built fixed bed 200 g in-situ hydration and dehydration chamber to assess the materials performance on a larger scale. The results demonstrate that the thermochemical storage potential of the 13X molecular sieve was enhanced following a Mg 2+ ion exchange process, resulting in a maximum increased energy storage of approximately 14% (65 J/g) compared to standard non treated 13X pellets. [ABSTRACT FROM AUTHOR]

• An improved operation strategy for decentralized A-CAES is proposed. • TES behavior and its effects on A-CAES performance are analyzed. • Characteristics and capacity limitations of HES's components are considered. • A parametric study showed an optimum value for the system's design parameters. • Improved operation strategy reduced the ramp-up /down rate by around 4% /11%. Adiabatic compressed air energy storage (A-CAES) has shown great application potentials in integrated hybrid energy systems (HES) in recent years. The integration requires A-CAES to store intermittent renewables power to meet the fluctuating load demand. Therefore, the operation of compressors and turbines must be adjusted by renewable power output and load demand, respectively. This paper presents an improved energy management operation strategy (I-EMOS) to enhance the A-CAES system's utilization for decentralized applications. In doing so, besides integrating thermal energy storage (TES) unit into CAES, several limitations of an A-CAES unit, such as its conversion process mode, dynamic characteristics, power input/output constraints of compressor/turbine train, air pressure constraint, and thermal storage capacity limitations are considered. An HES consisting of PV, A-CAES, and grid to answer the building's electric demand is simulated. The results are validated against data from an existing A-CAES pilot. It is concluded that adopting features and capacity limitations of the A-CAES system's power conversion unit in operational strategies contributes to improved management of energy flow in HES. It is observed that for certain air tank volume and maximum/minimum pressures under I-EMOS, an enhanced performance can be achieved. This analysis presents a feasibility assessment approach for decentralized A-CAES integrated with renewables implemented and tested in a real-world case study. [ABSTRACT FROM AUTHOR]

[Display omitted] • Direct solar-driven thermochemical energy storage in operando fluidized thermogravimetric analyzer is demonstrated. • Excellent long-term stability with energy storage density of more than 85% of the initial value after 100 cycles. • In-situ X-ray diffraction analysis shows the underlying mechanism is attributed to the presence of (AlMgFeMn)O x crystals. • The solar-thermal efficiency of (AlMgFeMn)O x CaCO 3 pellets is significantly improved from 9% to 19%. Calcium looping (CaL) is one of the most promising thermochemical energy storage technologies for high-temperature applications such as next-generation concentrated solar power (CSP) systems. However, most previous investigations have mainly focused on optimizing Calcium-based materials to maintain their reactivity during cycling, while their behavior in reactors under direct solar irradiation has rarely been reported. In this paper, highly efficient and stable direct solar-driven thermochemical energy storage in fluidized reactors is demonstrated. (AlMgFeMn)O x CaCO 3 pellets demonstrated excellent long-term stability with an energy storage density of more than 85% of the initial value after 100 cycles. The underlying mechanism can be attributed to the presence of poly-oxide (AlMgFeMn)O x crystals , which prevent crystallite growth and sintering, as confirmed by in-situ X-ray diffraction analysis. Moreover, the solar-thermal conversion efficiency of (AlMgFeMn)O x CaCO 3 pellets in fluidized bed reactors is significantly improved from 9% to 19% thanks to the considerably increased average solar absorptance and fast reaction kinetics over white (AlMg)O x CaCO 3 pellets. The experimental analysis using an operando fluidized thermogravimetric analyzer (F-TGA) further revealed that the interparticle diffusion control limitation in traditional TGA or fixed bed and localized overheating due to Gaussian distribution of solar irradiation are successfully relieved in a fluidized bed. We further suggest that steam has a positive effect on enhancing reaction kinetics and stability by performing 10 energy storage/release cycles of (AlMgFeMn)O x CaCO 3 pellets under direct irradiation of concentrated light due to the increase of surface area after rehydration and the higher OH reactivity toward CaO. This work paves the way for the application of solar-driven fluidized bed reactors for scalable thermochemical energy storage. [ABSTRACT FROM AUTHOR]

• Thermo-economic evaluation is performed for sub-ambient thermally integrated PTES. • Efficiency up to 99% is achievable by sacrificing the storage capacity and cost. • Cold-storage medium flowrate affects the storage capacity, cost, and power output. • Continuous high flowrate external heat source can reduce the LCOS up to 0.17 $/kWh. • Proposed technology performs comparably to others without geographical limitations. Thermally integrated pumped-thermal electricity storage (TI-PTES) offers the opportunity to store electricity as thermal exergy at a large scale, and existing studies are primarily focused on TI-PTES systems based on high-temperature thermal energy storage. This paper presents a thermo-economic analysis of a "cold TI-PTES" system which converts electricity into cold energy using a vapor compression refrigeration (VCR) unit and stores it at sub-ambient temperatures during the charging process, and generates electricity by using an organic Rankine cycle (ORC) working between the sub-ambient temperature and an external low-grade heat source during the discharging process. The effects of key parameters, i.e., mass flowrate and temperature of the storage medium, ORC evaporation temperature, component efficiencies, and pinch-point temperature differences, on the system performance are evaluated based on a whole-system thermo-economic model. The results reveal that the roundtrip efficiency and levelized cost of storage (LCOS) of the system increases while the electrical energy storage capacity decreases as the temperatures of the two cold storage tanks approach each other. When the temperature of the cold storage tank 1 rises from 1 °C to 8 °C while the cold storage tank 2 remains as 13 °C, there is an increase of 25% and 20% in the roundtrip efficiency and LCOS respectively while the energy storage capacity decreases by 69%. A roundtrip efficiency of 0.74 and LCOS of 0.32 $/kWh are achieved with a heat source temperature of 85 °C, using a mass flowrate and temperature of the cold storage medium of 50 kg/s and 1 °C. Furthermore, any change in cold storage medium mass flowrate changes both electrical energy storage capacity and power output by the same proportions. With a continuous high-flowrate external heat source, the LCOS can be as low as 0.17 $/kWh. By providing sufficient heat from an external heat source, the proposed system possesses a high potential for medium-to-large scale energy storage with a unique hybrid nature for electricity storage and thermal integration. [ABSTRACT FROM AUTHOR]

• A micro-CHP system integrating PVT collectors, a SE and energy storage is considered. • A transient model is developed to evaluate technoeconomic and environmental performance. • The primary energy savings and carbon emission reduction amount to 35% and 37%. • The discounted payback period of the system is 28 years. • The system has greater environmental benefits and a longer payback period than alternatives. This paper presents a comprehensive analysis of the energetic, economic and environmental performance of a micro-combined heat and power (CHP) system that comprises 29.5 m2 of hybrid photovoltaic-thermal (PVT) collectors, a 1-kW e Stirling engine (SE) and energy storage. First, a model for the solar micro-CHP system, which includes a validated transient model for the SE micro-CHP unit, is developed. Parametric analyses are performed throughout a year to evaluate the effects of key component sizes and operating parameters, including collector flow rate, storage tank size, SE micro-CHP flow rate, and battery capacity, on the energetic, economic and environmental performance of the proposed system using real hourly weather data, and thermal and electrical energy demand profiles of a detached house located in London (UK). The optimum component sizes and operating parameters are determined accordingly. The daily and monthly operating characteristics of the system are evaluated, and its annual performance is compared to those of a reference system (gas boiler plus grid electricity), as well as of other alternative solar-CHP systems including a PVT-assisted heat pump system and a standalone PVT system. The results indicate that the installation of such a system can achieve an annual electricity self-sufficiency of 87% and an annual thermal energy demand coverage of 99%, along with annual primary energy savings and carbon emission reduction rate of 35% and 37% relative to the reference system. Over 30 years of operation, the net present value (NPV) of the proposed system is £1990 and the discounted payback period is 28 years. The economics of the proposed system is very sensitive to utility prices, especially the electricity purchase price. Relative to the alternative solar systems, the proposed system offers greater environmental benefits but has a longer payback period. This implies that although the energy saving and emission reduction potential of the proposed system is significant, the initial/capital investment, especially of the SE CHP unit and the PVT collector array, are currently high, so efforts should focus on the cost reduction of these technologies. [ABSTRACT FROM AUTHOR]

• Three configurations of Rankine-based Carnot battery systems were presented. • Thermodynamic and economic models of proposed systems were developed. • The basic Rankine-based system has the highest power-to-power efficiency of 31.9%. • The reversible system has the lowest levelized cost of storage of 0.451 $/kWh. The rapid growth of renewable energy, accompanied by intermittent and instability, has brought great challenges to energy storage technology. Rankine-based Carnot batteries are considered a promising solution to electricity storage in view of their high energy density at a low temperature. Determining the suitable Rankine-based Carnot battery configuration for its development and application requires accurate prediction and comprehensive comparison of the system performance under different conditions. In this paper, three Rankine-based Carnot Battery systems were constructed using a heat pump-organic Rankine cycle. Mathematical models of the aforementioned systems were built to assess and compare their performance from a thermodynamic standpoint. The results showed that the basic heat pump-organic Rankine cycle and reversible heat pump-organic Rankine cycle are better in energy and exergy aspects, where power-to-power-efficiency and exergy efficiency are higher by about 21.4% and 18.7% than that of reversible heat pump-organic Rankine cycle using a dual-function machine, respectively. Compared with basic heat pump-organic Rankine cycle and reversible heat pump-organic Rankine cycle, the levelized cost of storage of reversible heat pump-organic Rankine cycle using a dual-function machine is lower by about 12.3% and 5.4%, respectively. Taking the three criteria together, it seems that the reversible heat pump-organic Rankine cycle is better thermo-economically. The sensitivity analysis revealed that the heat source temperature has a greater impact on the reversible heat pump-organic Rankine cycle using a dual-function machine, and its absolute value of the sensitivity coefficient is 3. [ABSTRACT FROM AUTHOR]

• A tri-generation system coupled with liquid air energy storage is proposed to use biomass efficiently. • Thermodynamic indicators for liquid air energy storage under the off-design conditions is proposed. • The effects of mixed burning ratio, charge–discharge cycles and charge–discharge pressure for system are discussed. • The electric efficiency of the system is 5.6% higher than that of traditional system. • The mixed burning ratio can reach 0.9 by choosing the suitable pressures of liquid air storage pressure. Biomass gasification, as a green energy, can be integrated with natural gas combined cooling, heating and power system to realize energy cascade utilization and reduce carbon emissions. This paper proposes a biomass gasification and liquefied natural gas complementary system, including biomass gasifier, gas turbine combined cycle, liquid air energy storage, and absorption chiller, to use more biomass efficiently. The system uses a liquid air energy storage system to absorb excess exhaust from the compressor and solves the compressor's surge when using low calorific value gas. This integration can raise mixed burning ratio of gas to 0.9 without modifying GT. The thermodynamic model of the system is established, and the evaluation indicators are proposed. Based on the rated power of a 270 MW gas turbine, the thermodynamic performances of the system under design conditions are simulated by Aspen Plus. The exergy flow diagrams of the three seasons are obtained. When the ambient temperature changes, the exergy destruction of gas turbine changes the most, and its exergy destruction in winter is 8.3% of the rated power lower than in summer. Besides, the heating exergy destruction of syngas reaches 76.8% for preheating feed water. The performances of the system under off-design conditions are discussed. When the mixed burning ratio of syngas and natural gas increases to 0.9, the input power of liquid air energy storage is 92 MW, and the output power is 53 MW. The electric efficiency of the system with liquid air energy storage increases by 5.6% compared to the system without liquid air energy storage. By selecting the design pressure of liquid air energy storage, the exergy efficiency can be increased by 6.5% when the mixed burning ratio is 0.9. [ABSTRACT FROM AUTHOR]

• A novel hybrid power/thermal-to-hydrogen energy storage scheme is applied to DES. • Multi-objective optimization is conducted for optimal configurations of the DES. • A case study of DES is performed in different climate regions of China. • The configuration flexibility and performances of the DES are improved. • Climate and market conditions have significant influences on DES deployment. This paper presents a novel distributed energy system (DES) with hybrid-hydrogen energy storage, in which the proton exchange membrane electrolyzer (PEMEC) and steam reforming of methanol (SRM) are used to convert surplus power and waste heat into hydrogen. To identify the feasibility of the proposed DES in different climate regions, a case study is performed to choose a rehabilitation hospital in Harbin, Jinan, Wuhan and Guangzhou of China to explore the DES optimal configurations. The mixed integer linear programming model is established and the multi-objective optimization considering annual total cost (ATC) and annual carbon emissions (ACE) is conducted by improved version of augmented ε -constraint (AUGMECON2) method for system optimal configurations. After selecting four cases among Pareto frontiers for each city, the two methods of Analytic Hierarchy Process/Shannon entropy combined with Gray Relation Analysis are performed to determine the most suitable locations. The results show that adding the SRM to DES as a hybrid-hydrogen energy storage system can improve the configuration flexibility, environmental performance and primary energy ratio compared with only-electrochemical hydrogen storage DES. The Pareto frontiers for four cities demonstrate a trade-off between ATC and ACE, and the ACE is decreased by 6.3% with ATC increased by 1.4% in Jinan. Generally, Guangzhou is the best suitable city, and Jinan and Wuhan rank second by two evaluation methods with 0.727 and 0.643 average scores, respectively. The current electricity and natural-gas prices are verified to be beneficial to Jinan to deploy the proposed DES, and Guangzhou and Wuhan present a better economic performance with the minimum ATC decreased by 11.4% and 6.58% under ideal energy prices. The results can provide useful information for hybrid-hydrogen energy storage application to DES in different climate regions. [ABSTRACT FROM AUTHOR]

• Use the P-graph approach to provide optimal and near-optimal solutions. • Integrate battery storage and hydrogen into renewable energy systems. • Hydrogen storage reduces energy system costs by 21.5% and battery storage by 5.3%. • Provide environmental cost of CO 2eq emission from the island energy system. • Sensitivity analysis can be used to support practical applications. Renewable energy systems play an important role in alleviating environmental pollution, and their characteristics, including low emissions and recyclability, are highly favourable. At present renewable energy can be costly and renewable energy systems have room for optimization, particularly systems which cater to remote and island areas. This paper develops a P-graph-based multi-period energy model, using hydrogen for energy storage to satisfy the fluctuating electrical and thermal energy demand of an island. Hydrogen can be generated from renewable energy sources during off-peak periods and can be used to serve as an energy carrier. An economic and carbon footprint analysis of the system is performed, which compares a pure renewable energy system, with hydrogen storage, and with battery storage. Within the same scenario, the results show that the renewable energy systems with hydrogen storage and battery storage are 21.5 % and 5.3 % cheaper than the renewable energy system without energy storage, with CO 2eq emissions of 1,717 t/y and 1,680 t/y. These findings show that the inclusion of energy storage systems has great potential to reduce costs within renewable energy systems. Changes in the supply of biomass were investigated (which had the greatest impact in the study area), as well as changes in the cost of hydrogen storage. In addition to the optimal solution, near-optimal solutions were also suggested to provide well-rounded guidance for implementation. [ABSTRACT FROM AUTHOR]

• A new distributed energy system that combines multi-energy storage is proposed. • An operation strategy that prioritizes the use of renewable energy is introduced. • A two-phase collaborative optimization method is proposed. • The new system is applied to a nearly zero energy community. The combination of a distributed energy system and multi-energy storage system has the potential to use renewable energy on a large scale and to further improve the system's energy efficiency. Therefore, a new type of distributed energy system that combines multi-energy storage is proposed in this paper. Its novelty is that the three types of energy storage, i.e., cold, heat and electricity, are considered simultaneously, and the electric vehicle load is also included in the distributed energy system in combination with the multi-energy storage system, which allows full consideration of the effect of multi-energy storage on the distributed energy system. Three operation modes are proposed to give full play to the advantages of the new system according to the charging mode for electric vehicles. Subsequently, a two-phase collaborative optimization method for system configuration and operation optimization is proposed, and it is applied to a nearly zero energy community. The results show that the primary energy savings rate of the distributed energy system that combines multi-energy storage is 53.5% when the electric vehicle charging load is provided by the new system, which is 17.5% higher than that of the traditional distributed energy system, while the annual cost savings rate increased by only 8.3%. In addition, the hourly operating cost of the distributed energy system that combines multi-energy storage is also significantly reduced compared with the separated production system. Therefore, the method of two-phase collaborative optimization in the new system proposed in this paper can be used to realize the optimal system configuration and operation design for energy savings and consumption reduction. Finally, the new system can provide a feasible scheme for the energy supply of a nearly zero energy community in the future. [ABSTRACT FROM AUTHOR]

• A hybrid power-to-gas process in a power plant utilizing captured carbon dioxide. • Developing the synthetic natural gas production process model by Aspen Plus. • Process optimizing through reaction operation conditions and thermal integration. • Annual energy storage of 2.9 × 107 GJ and 66% emission reduction for the power plant. • Methane production cost was 1738 $/ton when oxygen selling price was considered. The global destructive effects of carbon dioxide emissions and the importance of energy storage for grid stability and peak shaving applications are in deep concern. In this regard, this paper investigates the recycling of carbon dioxide from gas-fired power plant emissions into synthetic natural gas based on a novel power-to-gas process with the aim of chemical energy storage and emission reduction. The hybrid power-to-gas process proposed in this paper integrates the power generated from the gas plant and renewable energies. To make a precise evaluation of system performance, the referenced system is analyzed from technical, economic, and environmental points of view. The process is optimized through the reaction operation conditions and the energy utilization of the process. The results demonstrate that the power-to-gas process achieves a reaction synthetic natural gas production yield of over 97% at the optimal operation conditions. Regarding energy and environmental outlook, the power plant provides 15.4% of the power-to-gas total energy consumption, with the remaining 84.6% supplied from renewable energy resources. From the synthetic natural gas produced, the power-to-gas process provides total annual energy storage of 2.9 × 107 GJ and recycles 1.6 Mton of carbon dioxide for the power plant flues, resulting in a reduction of the plant emissions by around 66%. According to the economic data, with the consideration of the selling price of oxygen, the cost of the synthetic natural gas produced results in 1738 $/ton. The obtained results indicate that the system designed can reduce production costs due to hybrid electricity and offers two unique attributes: energy storage capability and drastic reduction of carbon dioxide emissions. [ABSTRACT FROM AUTHOR]

• A novel liquid air energy storage system is firstly established. • Test result with liquid phase cold storage subsystem is originally obtained. • The highest cold storage efficiency for the liquid air energy storage system is achieved. • The method for the cold storage subsystem design is analyzed and carried out. Liquid air energy storage is a promising large-scale energy storage technology for power grid peak-load shifting and reducing the volatility of renewable energy power generation. A high-efficiency cold storage subsystem of the liquid air energy storage system is important to guarantee good overall system performance. Liquid phase cold storage technology can avoid the heat conduction in the axial direction of that in the solid-phase media, which theoretically can achieve a higher cold storage efficiency. In this paper, the design method for liquid phase cold storage was proposed. A novel liquid air energy storage system with the compression power of 100 kW was built. The variation rules of the working medium temperatures, pressures and other key experimental results during the process of cold storage and release were tested. Results showed that the system achieved a 91.35% cold storage efficiency, providing an important basis for the liquid–air energy storage system to making it possible to gain a net round trip electricity to electricity efficiency to 50%. Methods to further improve the cold storage efficiency were also proposed in this paper. [ABSTRACT FROM AUTHOR]

• SNG and O 2 are produced by a methanator coupled to an electrolyzer and a geothermal plant. • Products are cost-effectively liquefied increasing their value and easing transport and storage. • Selling LSNG and LOx on relevant markets makes the system cost-effective. • Excess electricity available in low price hours is exploited. • The system eases the integration of an increasing share of renewable generation. In the framework of a scenario with an always increasing share of generation from variable renewable sources, the need for systems able to store energy or to convert the excess generation into useful goods is becoming of paramount importance. While several projects and pilot plants deal with direct energy storage or with the conversion of the excess generation into other energetic goods (hydrogen or methane) often overlooking economic considerations, this paper proposes a cost-effective approach in which liquified methane and oxygen are produced and sold on their specific markets, which represents one of the first profitable Power-to-X applications at current market values. The paper presents the completely new and never investigated before idea of coupling the plant with a freely available source of pure carbon dioxide from a geothermal unit, thus making it possible to produce synthetic methane to be liquefied, stored and then used in other sectors of the society. The carbon dioxide coming with the geothermal fluid is no longer released in the environment as it currently naturally happens even when not going through the geothermal facility. Detailed models of the main system components were created, and an optimization procedure was carried out. Interestingly, the revenues from the sale of liquefied oxygen are well above those coming from synthetic methane and turn the system profitable. With a proper operation planning, bidding on the electricity day-ahead-market, a large hydrogen storage system proved to be unnecessary. The results of the system optimization clearly show that this kind of systems, although conceived in a very favourable condition, can become profitable only if the energy storage function is coupled with the production of other goods services. Assuming an average electricity price of 52 €/MWh, the plant profitability is achieved for an LNG selling price of 0.45 €/kg and an LOx price around 0.30 €/kg. These figures will rapidly decrease in the near future as lower electricity prices are forecasted. [ABSTRACT FROM AUTHOR]

A promising way to electrify regions lacked to reliable access to electricity is the employment of stand-alone photovoltaic power systems (SPPSs). Recently, the cost of electricity from such systems has fallen, and it is expected that this tendency will continue in the future. Within this paper, a new design methodology of highly reliable and sustainable SPPSs is presented. The approach consists of the following processes: prediction of the load demand, characterization of the PV performance on site, sizing the SPPS considering different storage technologies, and forming the most effective design. On the other hand, a new dimensionless number will be introduced to characterize the PV performance at a particular location. In order to demonstrate the methodology, an intention to electrify 93 households in a rural community is given as an example. The results show that a SPPS configuration including compressed air energy storage and supercapacitor may be the most effective SPPS design. [ABSTRACT FROM AUTHOR]

Energy storage plays a vital role in shifting cooling energy load from period of peak demand to that of low demand. This paper reports performance data of an ice-storage unit in solar absorption cooling system for cooling an office space. The cooling system consists of ammonia-water absorption chiller, evacuated tube solar collectors and ice-storage. Experiments were carried out on two consecutive days in each of the month of March and October in Dhahran, Saudi Arabia. The ice-storage unit was charged on the first day and the cool energy discharged on the other day. The results showed average coefficient of performance (COP) of the chiller during charging as 0.43 and 0.47 for the months of March and October, respectively. The results also indicate that the ice-storage can provide a backup time of about 5–6 h, which is sufficient to cool the given space during the early hours of chiller warm-up. [ABSTRACT FROM AUTHOR]

In this study a 4.4 kW stationary compression ignition engine is coupled with a double pipe heat exchanger, vapour absorption refrigeration system and thermal energy storage system to achieve Trigeneration i.e. power, heating and cooling. A shell and tube type heat exchanger filled with erythritol is used to store thermal energy of engine exhaust. Various combinations of thermal energy storage system integrated micro-trigeneration were investigated and results related to performance and emissions are reported in this paper. The test results show that micro capacity (4.4 kW) stationary single cylinder diesel engine can be successfully modified to simultaneously produce power, heating and cooling and also store thermal energy. [ABSTRACT FROM AUTHOR]

In this paper, cost-efficient operation problem of photovoltaic/battery/fuel cell hybrid energy system has been evaluated in the presence of demand response program. Each load curve has off-peak, mid and peak time periods in which the energy prices are different. Demand response program transfers some amount of load from peak periods to other periods to flatten the load curve and minimize total cost. So, the main goal is to meet the energy demand and propose a cost-efficient approach to minimize system’s total cost including system’s electrical cost and thermal cost and the revenue from exporting power to the upstream grid. A battery has been utilized as an electrical energy storage system and a heat storage tank is used as a thermal energy storage system to save energy in off-peak and mid-peak hours and then supply load in peak hours which leads to reduction of cost. The proposed cost-efficient operation problem of photovoltaic/battery/fuel cell hybrid energy system is modeled by a mixed-integer linear program and solved by General algebraic modeling system optimization software under CPLEX solver. Two case studies are investigated to show the effects of demand response program on reduction of total cost. [ABSTRACT FROM AUTHOR]

Different storage technologies enable an increasing share of variable renewable generation in the electricity system by reducing the temporal mismatch between generation and demand. Two storage ratings are essential to time-shift delivery of electricity to loads: electric power, or instantaneous electricity flow [W], and electric energy, or power integrated over time [Wh]. An optimal storage portfolio is likely composed of multiple technologies, each having specific power and energy ratings. This paper derives and explains the link between the shape of the time-varying demand and generation profiles and the amount of desirably installed storage capacity, both energy and power. An analysis is performed for individual storage technologies first, showing a link between the necessary power and energy capacity and the demand and generation profile. Then combinations of storage technologies are analyzed to reveal their mutual interaction in a storage portfolio. Results show an increase in desirability for storage technologies with low cost power ratings when the mismatch between generation and demand occurs in daily to weekly cycles. Storage technologies with low cost energy ratings are preferred when this mismatch occurs in monthly to seasonal cycles. The findings of this work can help energy system planners and policy makers to explain results from generation expansion planning studies and to isolate the storage benefits accountable to temporal arbitrage in broader electricity storage studies. [ABSTRACT FROM AUTHOR]

Liquid Air Energy Storage systems represent a sustainable solution to store energy. Although a lot of interest is dedicated to large scale systems (up to 300 tons per day), a small-scale Liquid Air Energy Storage can be used as energy storage as part of a microgrid and/or an energy distribution network. However, when scaling down the size of the system, the round trip efficiency decreases due to the low performance of the liquefaction process. In this paper a preliminary study on the optimal configuration for a microgrid scale liquefaction cycle (10 tons per 12 h) for a Liquid Air Energy Storage application is proposed in order to minimize the specific consumption. The Linde, Claude and Kapitza cycles are modelled and compared by means of a parametric analysis carried out with the software Aspen HYSYS. The results show that the two stages compression Kapitza cycle operating at 40 bar represents an optimal solution in terms of performance and cycle configuration resulting in a specific consumption of about 700 kW h/t. The analysis also shows that the implementation of a pressurized phase separator leads to a reduction of the specific consumption as high as 21% (≈550 kW h/t). [ABSTRACT FROM AUTHOR]

Exploiting renewable energy is a critical greenhouse gases reduction strategy for China, especially in areas where new power plants are needed. Challenges in energy storage, however, always complicate the design of renewable energy-dominated power generation systems. This study attempt to provide a solution to the energy storage problem through the synergy of both the power supply and demand sides. Based on local natural energy resources endowments, this paper applies the hybrid optimization model for multiple energy resources and load types to analyse the feasibility of satisfying energy demand. To verify the model’s technological and economic feasibility, this research applies its synergy model to a 2.8 km 2 isolated island in the South China Sea. The simulation results demonstrate that the cost of energy and net present cost of the power supply system are $0.212/kW h and $127 M when hydrogen energy storage equipment is used, and $0.178/kW h and $101 M when traditional-battery energy storage equipment is utilized. This study also reveals that using flywheels to supplement the hydrogen and traditional-battery energy storage equipment could reduce the cost of energy by 5.6% and 3.4%, respectively. In addition, power system demand-side management can further reduce the cost of energy by approximately 20% for all technology scenarios considered in this study. A carbon emissions analysis demonstrates that the carbon reduction rates of the proposed power systems are between 87.7% and 95.1% compared with a fossil-energy based power system. In brief, this study indicates that solar and wind energy combined with appropriate energy storage equipment can meet the energy demand of the island. [ABSTRACT FROM AUTHOR]

The plug-in electric vehicles and hydrogen storage systems containing electrolyzer, stored hydrogen tanks and fuel cell as energy storage systems can bring various flexibilities to the energy management problem. In this paper, selling price determination and energy management problem of an electricity retailer in the smart grid under uncertainties have been proposed. Multiple energy procurement sources containing pool market, bilateral contracts, distributed generation units, renewable energy sources (photovoltaic system and wind turbine), plug-in electric vehicles and hydrogen storage systems are considered. The scenario-based stochastic method is used for uncertainty modeling of pool market prices, consumer demand, temperature, irradiation and wind speed. In the proposed model, the selling price is determined and compared by the retailer in the smart grid in three cases containing fixed pricing, time-of-use pricing and real-time pricing. It is shown that the selling price determination based on real-time pricing and flexibilities of plug-in electric vehicles and hydrogen storage systems leads to higher expected profit. The proposed model is formulated as mixed-integer linear programming that can be solved under General Algebraic Modeling System. To validate the proposed model, three types of selling price determination under four case studies are utilized and the results are compared. [ABSTRACT FROM AUTHOR]

This paper describes a hybrid tram powered by a Proton Exchange Membrane (PEM) fuel cell (FC) stack supported by an energy storage system (ESS) composed of a Li-ion battery (LB) pack and an ultra-capacitor (UC) pack. This configuration allows the tram to operate without grid connection. The hybrid tram with its full load is tested in the CRRC Qingdao Sifang Co.; Ltd. It firstly works on the operation mode switching method (OPMS) without energy regenerative and proper power management. Therefore, an equivalent consumption minimization strategy (ECMS) aimed at minimizing the hydrogen consumption is proposed to improve the characteristics of the tram. The results show that the proposed control system enhances drivability and economy, and is effective for application to this hybrid system. [ABSTRACT FROM AUTHOR]

This paper evaluates the potential carbon dioxide emissions reduction from the implementation of electric energy storage to a combined power generation unit and an organic Rankine cycle relative to a conventional system that uses utility gas for heating and utility electricity for electricity needs. Results indicate that carbon dioxide emission reductions from the operation of the proposed system are directly correlated to the ratio of the carbon dioxide emission conversion factor for electricity to that of the fuel. The location where the system is installed also has a strong influence on the potential of the proposed system to save carbon dioxide emissions. Finally, it is shown that by using carbon emissions cap and trade programs, it is possible to establish a frame of reference to compare/exchange operational cost gains with carbon dioxide emission reductions/gains. [ABSTRACT FROM AUTHOR]

In this paper, the comparative study of energy and exergy performance of two weir type cascade solar stills with and without PCM storage in sunny and semi-cloudy days is carried out. The governing equations of energy analysis include a set of nonlinear equations which is obtained by writing energy balance for the various components of a solar still (i.e. glass cover, brackish water, absorber plate, phase change materials). A detailed exergy analysis is carried out and various irreversibility rates in the solar still system and its exergy efficiency are introduced. In order to solve the governing equations a computer simulation program is developed. The results of a numerical simulation of the present study are in good agreement with the experimental data of previous literatures. The numerical results of the present study show that the energy and exergy performance of solar still without PCM storage is better than the solar still with PCM storage in sunny days. On the other hand, the solar still with PCM storage is preferred for semi-cloudy days due to its better energy and exergy performance. The maximum value of the energy and exergy efficiencies of the solar still without PCM for a typical sunny day are 76.69% and 6.53%, respectively. While, the maximum energy and exergy efficiencies of the solar still with PCM for a sample semi-cloudy day are 74.35% and 8.59%, respectively. Furthermore, it is observed that the highest irreversibility rate belongs to the absorber plate and its value for the solar still without PCM on typical sunny day and the solar still with PCM on semi-cloudy days is 83.1% and 78.8% of the whole of system irreversibility rates, respectively. Whereas, the irreversibility rate of glass cover and brackish water can be neglected. [ABSTRACT FROM AUTHOR]

This paper describes the performance of thermal storage integrated micro-cogeneration system based on single cylinder diesel engine. In addition to electricity generated from genset, waste heat from hot exhaust of diesel engine was used to heat water in a double pipe heat exchanger of 67.70 cm length with inside tube diameter of 3.81 cm and outside tube diameter of 5.08 cm. Additionally, a latent heat thermal energy storage system was also integrated with this cogeneration system. A shell and tube type heat exchanger of 346 mm diameter and 420 mm height with 45 tubes of 18 mm diameter each was designed and fabricated, to store thermal energy, in which Erythritol (C 4 H 10 O 4 ) was used as phase changing material. The test results show that micro capacity (4.4 kW), stationary, single cylinder, diesel engine can be successfully utilized to simultaneously produce power as well as heating, and to also store thermal energy. Slight decrease in engine performance was observed when double pipe heat exchanger and latent heat thermal energy storage system was integrated with engine but the amount of energy which could be recovered was significant. Maximum percentage of energy saved was obtained at a load of 3.6 kW and was 15.2%. [ABSTRACT FROM AUTHOR]

Utilizing renewable energies is the promising solution to the environmental problems which are brought about due to fossil fuel consumption. The fact that these kinds of energies are intermittent can be overcome with using energy storage systems. Wind energy coupled with compressed air energy storage systems is one of the best candidates in this respect. The main objective of this paper is to study the integration of this system with a Combined Cooling, Heating and Power cycle comprised of a gas turbine, an organic Rankine cycle and an absorption refrigeration system. Energy and exergy analyses are applied to the system and the effect of key parameters on the system performance are analyzed. The results show that under design condition, the system can generate 33.67 kW electricity, 2.56 kW cooling and 1.82 ton per day hot water with a round trip energy efficiency of 53.94%. Also exergy analysis reveals that wind turbine, combustion chamber and compress air storage system have the highest amount of exergy destruction respectively. Finally, sensitivity analysis shows that parameters related to gas turbine are the most prominent parameters of the system which can change performance of the system considerably. [ABSTRACT FROM AUTHOR]

[Display omitted] • High-potential Australian hydrogen hubs with existing infrastructure. • Hybrid wind-solar generation and flexible Haber-Bosch reduce storage needs. • Green ammonia cost-competitive if gas price $14/MBtu or higher in 2030. • Levelized costs of ammonia: $756/tonne by 2025 and $659/tonne by 2030. • Synergy between southern hemisphere supply and northern hemisphere demand. Green ammonia has received increasing interest for its potential as an energy carrier in the international trade of renewable power. This paper considers the factors that contribute to producing cost-competitive green ammonia from an exporter's perspective. These factors include renewable resource quality across potential sites, operating modes for off-grid plants, and seasonal complementarity with trade buyers. The study applies a mixed-integer programming model and uses Australia as a case study because of its excellent solar and wind resources, and the potential for synergy between Southern Hemisphere supply and Northern Hemisphere demand. Although renewable resources are unevenly distributed across Australia and present distinct diurnal and seasonal variability, modelling shows that most of the pre-identified hydrogen hubs in each state and territory of Australia can produce cost-competitive green ammonia providing the electrolysis and Haber-Bosch processes are partially flexible to cope with the variability of renewables. Flexible operation reduces energy curtailment and leads to lower storage capacity requirements using batteries or hydrogen storage, which would otherwise increase system costs. In addition, an optimised combination of wind and solar can reduce the magnitude of storage required. Providing that a partially flexible Haber Bosch plant is commercially available, the modelling shows a levelised cost of ammonia (LCOA) of AU$756/tonne and AU$659/tonne in 2025 and 2030, respectively. Based on these results, green ammonia would be cost-competitive with grey ammonia in 2030, given a feedstock natural gas price higher than AU$14/MBtu. For green ammonia to be cost-competitive with grey ammonia, assuming a lower gas price of AU$6/MBtu, a carbon price would need to be in place of at least AU$123/tonne. Given that there is a greater demand for energy in winter concurrent with lower solar power production, there may be opportunities for solar-based Southern Hemisphere suppliers to supply the major industrial regions, most of which are located in the Northern Hemisphere. [ABSTRACT FROM AUTHOR]

The inherent fluctuation and intermittence of wind power and solar photovoltaics pose great difficulty for stable power grid operation. Aiming at enhancing their exploitation efficiency, this paper presents a modeling study of a large-scale renewable energy system that is backed by gas turbine power plant and energy storage. From a full-life-cycle perspective, the system configuration and power dispatch strategy were optimized by coordinating system economy and carbon emission. The results indicate that the integration of gas turbine and hydrogen energy storage reduces carbon emissions and renewable curtailment but with high costs. To improve the system economy, extra electrochemical energy storage is incorporated to share the compensation when the grid shortfall is below the minimum gas turbine load. The collaborative hydrogen and electrochemical energy storage scheme improves the operating conditions of the gas turbine and significantly saves natural gas consumption, resulting in better system economy and carbon reduction. The minimum carbon emission of the proposed hybrid renewable energy system is 37.2% lower than the scenario with no renewable power. • Scalable hybrid renewable energy system modeling combined with gas turbine/storage • Integrated analysis for balancing system economy and carbon reduction • Multi-objective optimization for system configuration and operating strategy • Collaborative hydrogen and electrochemical storage scheme for economy/carbon gains [ABSTRACT FROM AUTHOR]

• Layered thermal store was both experimentally and numerically studied. • Layered control resulted in >60 % reduction on pressure drop. • Layered control resulted in uniform exit temperature for a longer period. • Layered store outperforms simple store as it reaches steady-state in 3rd cycle. • 1st and 2nd Law storage cycle efficiencies were analysed. This paper presents a study carried out as part of commissioning and testing of world's first grid-scale 150 kW e Pumped Heat Energy Storage (PHES) demonstration system. The system employs two novel layered packed-bed thermal stores. The present study experimentally investigates one of the stores designated as "hot thermal store", which has an energy storage density of 1072 MJ/m3 and stores heat at 500 °C and 12 bar. The layered store is an enhancement of a normal packed-bed store and offers a higher degree of thermal stratification. Experiments show that layering results in about 64 % reduction in pressure loss along with yielding considerably narrower thermocline. Round-trip efficiency, storage capacity and utilisation were calculated based on 1st Law analysis considering both simple and layered mode operation at nominal design conditions. Two cycle control scenarios were considered: time-based and temperature-based. In the time-based scenario, the store shows nearly similar performance in both modes. However, in temperature-based scenario, layered mode outperforms. During cyclic operation, layered mode outperforms as it reaches steady-state in merely 3rd cycle, without any loss in efficiency, capacity and utilisation; simple mode yields competitive efficiency but capacity and utilisation deteriorate after each successive cycle and steady-state is achieved in 20th cycle. 2nd Law analysis was additionally performed to gain insight into various losses and their impact on the performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Framework development for geological energy storage evaluation in renewable energy systems. • Integrated assessment of compressed air energy storage in porous formations (PM-CAES) for future energy systems. • PM-CAES may provide up to 50 GWh electrical energy for periods of up to 18 d. • Geotechnical optimisation of achievable power may be achieved through innovative well design. Compressed air energy storage in geological porous formations, also known as porous medium compressed air energy storage (PM-CAES), presents one option for balancing the fluctuations in energy supply systems dominated by renewable energy sources. The strong coupling between the subsurface storage facility and the surface power plant via the pressure of the compressed air, which directly determines the amount of energy stored and the power rates achievable, requires the consideration of the fluctuating supply and demand of electric power, the specific technical design of the compressed air energy storage plant and the subsurface storage processes to determine achievable power rates, storage capacities and overall performance. In this paper, we present subsurface storage designs using a set of future energy system scenarios with different fractions of renewable energy supply and technical options for the power plant. Our findings indicate that the PM-CAES systems can supply 115 MW of electric power and between 12.1 GWh and 49.9 GWh of electric energy for up to 429 h, thus offering grid-scale power storage capacity. The storage design is robust against variations in future energy system scenarios and different power plant configurations, with efficiencies between 0.54 and 0.67 and energy densities between 0.12 and 0.28 kWh per kilogram of stored air. The storage design can be improved further by using horizontal instead of vertical wells, which also reduces induced pressure increases in the storage formation. This study for the first time provides a complete framework for assessing achievable storage rates and capacities for PM-CAES based on detailed forecasts of future energy systems, the geological and geotechnical setting as well as engineering aspects of the compressed air energy power plant. [ABSTRACT FROM AUTHOR]

• Hydrogen storage systems enable flexible energy conversion and scheduling. • Hydrogen storage cost accounts for the largest proportion of system cost. • The hydrogen energy storage system has less demand for energy storage space. With global energy consumption increasing year by year, the industrial sectors of the world's countries have never been more urgent in achieving carbon reduction. Renewable energy plays a crucial role in the industrial decarbonization process. As the most mature renewable energy technology, wind and photovoltaic power generation have made significant progress in recent years. However, the intermittent characteristics hinder the efficient use of renewable energy. Existing research provides sufficient support for the flexible scheduling of large-scale renewable energy. Hence, this paper proposes a combined energy system composed of wind power-photovoltaic-energy storage salt cavern with hydrogen as the energy scheduling carrier. The system mainly realizes energy conversion through electrolytic water equipment and fuel cells. Then, Qianjiang City, Hubei Province, is taken as the analysis object, and the working conditions of each component in the system are optimized with the help of an improved particle swarm optimization algorithm. According to the results, the system's contribution to the energy system is discussed, and the system's economy and carbon reduction effect is studied. The analysis proves that the improved particle swarm optimization algorithm has a stronger solving ability. The combined energy system can effectively improve the economy and renewable energy utilization rate, meet the regional electricity demand, and significantly reduce carbon emissions. The economic analysis of the system shows that the operation and maintenance cost of hydrogen storage salt caverns accounts for the largest proportion of the total cost, about 60 %. Compared with several existing large-scale energy storage technologies, it is found that the energy efficiency of the whole system is only about 40 % due to the limitation of technology maturity. Nevertheless, the flexibility of the hydrogen storage system layout is relatively high. The required underground space volume is only equivalent to 1/6 and 1/2 of pumped storage and compressed air storage with the same scheduling capacity. The system will provide a theoretical support for the optimization of energy pattern and layout. [ABSTRACT FROM AUTHOR]

For multi-energy storage vehicles, the performance of online predictive energy management strategies largely relies on the length and effective utilization of predictive information. In this context, this paper proposes a novel velocity prediction method for the full driving cycle of electric vehicles based on the spatial–temporal commuting data, then the predicted velocity is applied to predictive energy management in electric vehicles with battery/supercapacitor hybrid energy storage system. Firstly, an one-year real-world commuting data set is collected on a Chinese arterial road with 10 intersections, 225 records are classified into 79 categories. Then, a real-time two-stage full driving cycle prediction method is proposed, where a medium-term prediction based on a long–short term memory (LSTM) network and a long-term prediction generated by a spatial–temporal interpolation method (STIM) are spliced for each category. The most probable category, i.e., the executed LSTM and STIM can be updated in real-time. Finally, a multi-horizon model predictive control method (MH-MPC) is established to leverage the predicted velocity for optimal power distribution. Compared with the conventional short-sighted MPC, the MH-MPC can reduce 4.2% battery degradation cost in a statistics form with real-time computation requirements satisfied. • A novel spatial–temporal data-driven velocity prediction method is proposed. • Second-level velocity prediction of the full driving cycle can be achieved. • Multi-horizon model predictive control for long-term optimal energy management. • More economy gained from leveraging the long-term prediction information. • The study is based on a one-year real-world commuting data set in China. [ABSTRACT FROM AUTHOR]

• A CaL system is proposed for energy storage, domestic heat supply and CO 2 capture. • The system configuration is optimized by the HEATSEP framework. • The heat storage efficiency and energy penalty sources are analyzed. • CO 2 avoidance cost: 111.1 RMB/ton CO2 with the average CaO conversion of 0.3. • Potential approaches to improve techno-economic performances were analyzed. Affordable long-term energy storage and CO 2 capture technique are imperative to developing the future carbon–neutral energy system. This paper proposed a calcium looping system powered by excess renewable electricity to achieve long-term thermochemical energy storage, residential heat supply and carbon capture. The system can be constructed with industrial equipment and exploit natural, abundant and cheap limestone as the circulating material. The electrical calciner is designed to charge the energy and produce the high-pressured CO 2 during the valley of the electricity grid, while the carbonator side is primarily driven by the discharged thermochemical energy and on-demand coordinates the heat network along with the carbon capture. The HEATSEP framework is adopted to optimize heat transfer processes and operating conditions for deriving the most favorable system configuration in the energy and economic aspects. Compared to the reference plant with electric boilers and short-term heat storage tanks, an energy penalty of around 32.3% total energy percentage points should be paid to drive long-term energy storage and carbon capture. The energy penalty is attributed to thermal losses in the calciner and heat exchanger networks, chemical energy lost by the make-up flow of fresh limestone, CO 2 compression for storage and auxiliary power for solid/fluid circulations. Due to a comparable total plant investment cost to the reference plant, the proposed system achieves the CO 2 avoidance cost of 111.1 RMB/ton CO2 , showing some competitiveness over current post-combustion carbon capture techniques. The techno-economic competitiveness of the proposed system can be further strengthened by replacing natural or synthetic Ca-based materials with high cycling performance instead of limestone, as well as extending applicable occasions to achieve almost year-round operation. [ABSTRACT FROM AUTHOR]

The global demands for air conditioning have increased rapidly over the last few decades leading to significant power consumption and CO 2 emissions. Current air conditioning systems use mechanical vapour compression systems which consume significant amount of energy particularly during peak times and use refrigerants that have global warming potential higher than that of carbon dioxide. This paper presents a new approach for providing air conditioning and power using liquid nitrogen produced from surplus electricity at off peak times or renewable energy sources. Thermodynamic analyses of different cryogenic cycles was carried out to achieve the most effective configuration that provides the required cooling and power for a 170 m 2 dwelling in Libya with minimum LN 2 consumption. Results showed that at today LN 2 prices, it is feasible to use LN 2 to provide for cooling and power demands of residential buildings with saving of up to 28% compared to conventional AC systems. However, as the LN 2 price decreases to around 1.3 pence per litre, the proposed technology will have significant advantages compared to AC systems with savings of up to 79% with almost 85% of the energy stored in LN 2 is recovered. [ABSTRACT FROM AUTHOR]

This work presents a smart microgrid consisting of diesel, photovoltaic (PV), and battery storage plants. One of the key features of smart grid is to provide a redundant high quality power for the consumers. In islanded microgrid, the under frequency and/or voltage collapse, caused by power deficiency, can lead to power outage. The current practice is to shed the load demand until the frequency and voltage are restored. However, the redundancy in supplying power has no meaning as long as the loads are shed. The main objective of this paper is to propose a power management system (PMS) that protects the microgrid against the load shedding. PMS is able to control the microgrid in both centralized and decentralized fashions. To prevent under frequency load shedding (UFLS), this work proposes using battery energy storage system (BESS) to compensate for the power mismatch in the islanded microgrid. A method is presented to estimate the rate of change of frequency and to calculate the power deficiency. The approximated value is exploited as the set-point to dispatch BESS. PV and battery plants are supposed to share the reactive power demand proportionally and thus regulate the voltage at the load bus. This work also suggests two outer control loops, namely, frequency restoration loop (FRL) and difference angle compensator (DAC). These loops ensure microgrid smooth transition from islanded mode to grid-connected mode. The microgrid is configured to investigate the effective utilization of exiting solar PV plant connected to distribution network in Sabah Malaysia. The microgrid is implemented in PSCAD software and tested under different scenarios. The microgrid with PMS shows operational stability and improvements in comparison with the original system. The results indicate that PMS can effectively control the microgrid in all operating modes. [ABSTRACT FROM AUTHOR]

In this paper, a method for designing hybrid electricity generation systems is presented. It is based on the Modified Electric System Cascade Analysis method. The Power Pinch analysis is used as a guideline for development of an isolated power supply system, which consists of photovoltaic panels, wind turbines and energy storage units. The design procedure uses a simulation model, developed using MATLAB/SIMULINK and applies the developed algorithms for obtaining an optimal design. A validation of the Modified Electric System Cascade Analysis method is performed by comparing the obtained results with those from the Homer Pro software. The procedure takes as inputs hourly wind speed, solar radiation, demands, as well as cost data, for the generation and storage facilities. It is also applied to minimize the loss of power supply probability and to minimize the number of storage units. The algorithm has been demonstrated with a case study on a site in Oujda city, with daily electrical energy demand of 18.7 kWh, resulting in a combination of photovoltaic panels, wind turbine and batteries at minimal cost. The results from the Modified Electric System Cascade Analysis and HOMER Pro show that both tools successfully identified the optimal solution with difference of 0.04% in produced energy, 5.4% in potential excess of electricity and 0.07% in the cost of the energy. [ABSTRACT FROM AUTHOR]

Thermal management is indispensable to lithium-ion battery pack especially within high power energy storage device and system. To investigate the thermal performance of lithium-ion battery pack, a type of liquid cooling method based on mini-channel cold-plate is used and the three-dimensional numerical model was established in this paper. The effects of number of channels, inlet mass flow rate, flow direction and width of channels on the thermal behaviors of the battery pack were analyzed. The results showed that the mini-channel cold-plate thermal management system provided good cooling efficiency in controlling the battery temperature at 5C discharge. A 5-channel cold-plate was enough and the temperature could be evidently reduced by increasing the inlet mass flow rate. Additionally, for the bad temperature uniformity in the design 1, design 2 was proposed and compared with the design 1. The maximum temperature and temperature difference decreased 13.3% and 43.3%, respectively. Temperature uniformity was significantly improved. [ABSTRACT FROM AUTHOR]

• Force interactions between foot and ground within a gait cycle are changing in a dynamic manner. • Capturing the vertical component of force and motion generated by foot can maximize the energy harvested from human walking. • Energy induced by footstep motion can be converted into hydraulic energy directly and stored simultaneously. • Hydraulic energy recovery system is superior in power density and storage to those aimed at generating electricity. Human walking induces a lot of mechanical energy available for harvesting. It is promising to use such energy to reduce the energy supply of wearable electronics and robotic equipment such as exoskeleton. This paper mainly deals with the design and performance analysis of the energy recovery system based on fluid power transmission principle. Firstly, modeling and simulation of single foot walking motion were carried out to investigate the human walking dynamics to explore the variation of energy produced by human walking within a gait cycle. Together with gait characteristics measurement, the foot-ground interaction force in the horizontal and vertical directions is obtained. Then, the energy recovery system based on the working principle of volumetric pump was designed to convert the human walking induced mechanical energy into hydraulic energy directly and achieve energy storage with accumulator in the meantime. The energy recovery results obtained under different conditions of walking speed and load carrying are considered by numerical simulation and experimental verification. It is shown that the output power in average of the recovery mechanism by single foot walking at 5.56 km/h is around 3.2 W, and the captured power can be increased with higher precharge pressure of accumulator. Comparisons indicate that power and its density of the system proposed in this paper are far greater than that achieved by electric generation, providing a potential solution for hydraulically actuated walking mechatronic systems. [ABSTRACT FROM AUTHOR]

• A coastal hydro-electrical energy system considering desalination is proposed. • The multi-objective operation optimization of the system is formulated. • The virtual energy storage characteristics of the desalination is analyzed. • The constrained NSGA-III algorithm can find the Pareto-optimal front of the problem. • The cost of desalination plants is reduced by using virtual energy storage analytics. To make best use of available coastal renewable energy and to meet local freshwater demand, optimal operation of a coastal hydro-electrical energy system with consideration of seawater desalination is proposed in this paper. The paper outlines a system configuration which is used to develop the virtual energy storage characteristics of a desalination plant and in which cost-savings are demonstrated while preserving the local desalinated water supply. To achieve the control criteria, minimization of the total period cost and tie-line power fluctuations are considered as two objectives in an objective function. Constraints are established based on the system configuration and the multi-objective optimization problem is solved with the third generation of the constrained non-dominated sorting genetic algorithm (NSGA-III) algorithm. Virtual energy storage characteristics of the desalination units is studied and utilized in the model. The paper examines several case studies to verify the feasibility and merits of the proposed method. The operational characteristics of the virtual energy storage components in the system is discussed, and sensitivity analysis of the operating parameters of the pumped storage hydropower unit and the seawater desalination unit are also conducted. Simulation results show that the proposed optimal operation approach is suitable for calculating the total cost as well as assessing the power stability on the tie-line, and NSGA-III is capable of determining the Pareto-optimal operational plans of the system. [ABSTRACT FROM AUTHOR]

• Construct an evaluation system of energy storing node optimization selection. • Contribute to adding four subnetworks using BOCR with this study's concern. • Extend the research on energy storage enterprises selection. • Extend the research on overall influential factor evaluation and ranking analysis. Energy storage has developed into a key solution to the problem of energy abandonment, which has been paid close attention. In the era of energy sharing, there is a general trend of cooperation between energy storage companies and power suppliers. This paper evaluates energy storage node enterprises to make their alliance more valuable with power generation node enterprises. First, this paper expounds the importance of sustainable energy storing node optimization selection and identifies 23 criteria from the perspective of benefits, opportunities, costs and risks to establish the evaluation index system. Then a hybrid ANP-BOCR -TOPSIS method is proposed to evaluate the index system including determining the integrated criteria weights and ranking four alternatives by TOPSIS method. Next, a case study is used to verify the accuracy and feasibility of the hybrid method. Through the validation with DEMATEL and comparative analysis of three integrated methods, it is concluded that the hybrid ANP-BOCR-TOPSIS method can be applied to the evaluation of clean energy further research. Finally, the suggestions and conclusions are given in the end. [ABSTRACT FROM AUTHOR]

• A novel energy storage-based supercritical CO 2 power system with ejector is proposed. • Thermodynamic analysis and parametric optimization are carried out. • Power regulation capacities in energy storage and release conditions are examined. • Correspondence between storage tank pressure and system performance is conducted. The application of supercritical CO 2 (S-CO 2) in power generation systems shows huge advantages of compactness and high efficiency for nuclear energy utilization. However, it is difficult to achieve a quick response for reactor power regulation system in isolated power gird, and amounts of nuclear heat is wasted by bypass regulation to track the power load. In this paper, a novel energy storage-based supercritical CO 2 power system with ejector is proposed to realize the rapid energy storage and energy release in system operation to guarantee high conversion efficiency of nuclear energy. Thermodynamic mathematical models are established to examine the performance of the proposed system. The parametric analysis and optimization are performed to acquire the optimum system performance. Furthermore, the performance evaluation in energy storage conditions and energy release conditions are presented to show the power regulation capacity of the proposed system. Results show that the appropriate split ratios of recompression supercritical CO 2 power system for different main compressor outlet pressures are both about 0.3. The optimum thermal efficiency of the proposed system is 44.58% and the corresponding exergy efficiency is 66.94% under the given system conditions. In addition, 10% of mass flow rate storage for the S-CO 2 results in a decrease in power load of 41.2%, and 10% of mass flow rate release for the S-CO 2 can achieve an increase in power load of 45.59%. Furthermore, the maximum regulation capacity for the power load increases with the pressure of the high-pressure energy storage tank. Meanwhile, the energy release conditions with a low pressure of high-pressure energy storage tank and a high entrainment ratio of the ejector result in the decrease in net power output. [ABSTRACT FROM AUTHOR]

• The off-design model of liquid air energy storage system is established. • The new strategy considers the synergistic regulation relationship between multiple variables. • The cold cycle strategy is helpful to recover cold energy and improve system performance fully. • The thermal cycle strategy achieves better heat coupling and prolongs the discharging time. • The off-design operation domains of the system under different molten salt temperatures are obtained. Liquid air energy storage (LAES) is a large-scale physical energy storage system with high energy storage density. At present, the coupling matching regulation mechanism of the cold and thermal cycles is unclear under off-design conditions, which makes the stable and efficient operation of the LAES system difficult. New multivariable control strategies for cold and thermal cycles are proposed based on the solar aided liquid air energy storage (SA-LAES) system. The study results show the "equal proportion cold recovery" strategy is superior to other strategies, improving the system performance and meeting the demand of the maximum capacity of the charging process. When the liquid air mass flow ratios are 0.7 and 0.4, the air liquefaction ratios increase by 20.20% and 86.43%, and the round-trip efficiency (RTE) values increase by 19.44% and 84.86%, respectively. The new thermal cycle control strategy achieves a good heat coupling matching and maximizes the discharging time and RTE in the zero-carbon environment. Under 70% load and 40% load, the discharging time increase by 16.26% and 53.83%. RTE values increase by 16.28% and 53.84%, respectively. Finally, the operation domains of SA-LAES at different molten salt temperatures are obtained with the optimal cold and thermal cycle strategies. The achievements in this paper will provide valuable reference for the stable operation of SA-LAES under off-design conditions. [ABSTRACT FROM AUTHOR]

• Thermal energy storage characteristics under solar fluctuation are studied. • Charging performance over the whole working days is analysed. • Effects of high-level, rising, oscillating and falling solar radiation are revealed. • Heat transfer enhancement of ceramic foam under solar fluctuation is demonstrated. Thermal energy storage (TES) is an effective method to buffer solar fluctuation and enable Organic Rankine Cycle (ORC) to operate under steady and design conditions. Heat transfer and energy storage characteristics of TES systems under solar fluctuation need to be studied to better understand the practical energy storage process and provide guidance on design/optimisation of integrated TES-ORC systems. In this paper, the charging process of a shell-and-tube system containing molten salt as phase change material with/without ceramic foam enhancement over a whole sunny and cloudy day was investigated. For the same full charging cases, the total stored energy is different according to solar fluctuation, with a maximum difference of 17.9%. Strong solar radiation not only accelerates the energy storage rate but also improves the total stored energy. Rising solar radiation can also cause large total stored energy while the energy storage rate is slow. Oscillating solar radiation generates the least total stored energy among full charging cases, however, the energy storage rate is higher than that under rising solar radiation. Falling solar radiation leads to small total stored energy. Ceramic foam-enhanced molten salt is more sensitive to solar fluctuation while the total stored energy over the whole working day is improved by 33.2% on a sunny day and 29.1% on a cloudy day respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel adsorption-type trans-critical compressed CO 2 energy storage system is proposed. • The low-pressure adsorption tank uses an adsorption strategy and significantly increases CO 2 storage density. • The dynamic charging and discharging process of the high-pressure storage tank is examined. • The influence of key parameters on the volume of the high-pressure storage tank is investigated. • The system does not need to rely on thermal storage heat exchangers and large underground caverns. Compressed CO 2 energy storage technology is a feasible resolution to stabilize the fluctuation of renewable energy output and has significant development prospects. The main challenge currently facing is how to achieve high-density storage of low-pressure CO 2. To get rid of the engineering application limitations caused by low-pressure CO 2 liquefaction storage and large-scale cave storage, a new type of adsorption trans-critical compressed CO 2 energy storage system is proposed in this paper. Using Fe-MOR(0.25) as an adsorbent, the storage density of CO 2 can reach 390.94 kg/m3 at 298 K and 0.1 MPa. The thermodynamic simulation is carried out based on the first and second laws of thermodynamics. The results demonstrate that the system round trip efficiency, exergy efficiency, and energy storage density under the design conditions are 66.68 %, 67.79 %, and 12.11 kWh/m3, respectively. The results of sensitivity analysis indicate that the storage pressure and storage temperature of the high-pressure tank have compound effects on the system, and they are the key parameters affecting the performance of the system. Releasing pressure at critical points can cause abrupt changes in system performance. Heat exchanger effectiveness, compressor, and turbine isentropic efficiency improvements positively affect the system performance. [ABSTRACT FROM AUTHOR]

During power grid contingencies, frequency regulation is a primary concern. Historically, frequency regulation during contingency events has been the sole responsibility of the power utility. We present a practical method of using distributed demand response scheduling to provide frequency regulation during contingency events. This paper discusses the implementation of a control system model for the use of distributed energy storage systems such as battery banks and electric water heaters as a source of ancillary services. We present an algorithm which handles the optimization of demand response scheduling for normal operation and during contingency events. We use dynamic programming as an optimization tool. A price signal is developed using optimal power flow calculations to determine the locational marginal price of electricity, while sensor data for water usage is also collected. Using these inputs to dynamic programming, the optimal control signals are given as output. We assume a market model in which distributed demand response resources are sold as a commodity on the open market and profits from demand response aggregators as brokers of distributed demand response resources can be calculated. In considering control decisions for regulation of transient changes in frequency, we focus on IEEE standard 1547 in order to prevent the safety shut-off of inverter-based generation and further exacerbation of frequency droop. This method is applied to IEEE case 118 as a demonstration of the method in practice. [ABSTRACT FROM AUTHOR]