Recent advances in energy storage and energy saving technologies:SDEWES special issue in 2022

Over the past few decades,there has been significant attention devoted to the development of advanced technologies for achieving sustainable and environmentally friendly energy production.One prominent event in this field was the 17th SDEWES Conference(Sustainable Development of Energy,Water,and Environment Systems),which took place from November 6-10,2022,in Paphos,Cyprus.This conference served as a gathering for 496 professionals,comprising scientists,researchers,and experts specializing in sustainable development.Participants came from 52 countries spanning six continents,with 349 attending in person and 147 joining virtually.Prof.Neven Duic,the full professor in the University of Zagreb,originated the SDEWES series since 2002,and serves as the associate editor of Energy Storage and Saving(ENSS)from the journal organization in 2021.This special issue(SI)is the second-time collaboration between SDEWES and ENSS.This editorial focuses on collating the key papers presented during the conference,with a particular emphasis on the pivotal topics including review on electrification and decarbonization,geothermal power utilization,thermal energy storage in heat pump,thermo-economic analysis on thermal system of buildings,industrial policymaking for low-emission technologies and mining investment in Latin America.ENSS also has established the SI for 18th SDEWES in 2023.Manuscripts are welcomed to 18th SDEWES held in Dubrovnik,Croatia on September 24-29,2023.

Thermodynamic performance of a cryogenic energy storage system based on natural gas liquefaction

Cryogenic energy storage(CES)is a viable method for grid-scale electrical energy storage.Considering the high energy density and mature application of liquefied natural gas(LNG),we proposed an LNG cryogenic energy storage(LNGES)system.A steady-state process model of the LNGES system was established using Aspen HYSYS.The effects of the natural gas composition and key operating parameters such as the charging pressure,discharging pressure,throttling temperature,and liquid storage pressure on the system performance were investigated.A multi-parameter genetic algorithm model built using the MATLAB software was used to optimize the LNGES system to optimize the round-trip efficiency(RTE).Then,an exergy analysis of the optimal configuration was conducted.The results suggested that the LNGES system could achieve optimal RTE and exergy efficiency values of 60.14%and 71.64%,respectively.Exergy destruction mainly occurred during the compression,throttling,expansion,and heat exchange.The proposed LNGES system could be a promising candidate for the large-scale application of CES technology in power grids and gas networks.

Experimental test of a building thermal system for preventive maintenance based on thermoeconomic analysis

An analysis of the sectorial structure of energy consumption shows that residential and tertiary sector buildings are the third-highest consumers,responsible for 29.5%of a city’s final energy consumption.The Building Quality Control Laboratory of the Basque Government aims to promote quality,innovation,and sustainability in buildings.To accomplish this goal,it has constructed an experimental facility with different energy generation technologies and a very versatile control system for testing different energy systems and operation modes.In this study,we tested a facility for supplying domestic hot water and heating for a multi-family house by means of a condensing boiler and an aerothermal heat pump(together with the corresponding control).This installation could reproduce the thermal demands required to be satisfied by the generation equipment through a programmed operation of the installation based on real demands.Additionally,this installation was analyzed using thermoeconomics(TE)to solve problems unable to be solved using traditional energy analyses based on the First Law of Thermodynamics.These problems include:(1)Determining the costs of the products of the installation based on physical criteria,(2)detecting the places where losses actually occur,evaluating their costs,and proposing cost-effective improvements,and(3)diagnosing issues in the installation.As a result,this paper suggests a solution to the preventive maintenance problems confronting the technical maintenance personnel for thermal installations in buildings by applying TE knowledge and using real data collected from sensors.

Thermal and mechanical characterization of under-2-μm-thick AlCrNbSiTi high-entropy thin film

High-entropy alloys(HEAs)exhibit extraordinary physical properties such as superior strength-to-weight ratios and enhanced corrosion and oxidation resistance,making them potentially useful in energy storage and gener-ation industries.However,thermal and mechanical properties of HEAs with various compositions vary signifi-cantly.Furthermore,these properties have rarely been investigated simultaneously owing to material or instru-mentation limitations.Herein,we synthesize an HEA(AlCrNbSiTi)coating with a thickness of less than 2μm.We customize a frequency-domain photothermal testing system to characterize the thermal and mechanical proper-ties of the proposed coating with high accuracy.Owing to the large mixing enthalpy of the Al-Ti,Nb-Si,and Ti-Si pairs in the coating,its hardness and elastic modulus are 15.2 and 254.7 GPa,respectively,which are higher than those of previously reported HEAs.The thermal conductivity of the AlCrNbSiTi coating is characterized to be 2.90 W·m^(−1)·K^(−1),within the expected range and well explained by the free-electron consistency diversity and phonon scattering from the amorphous structure.Additionally,the coating exhibits adequate wear performance,with a wear rate of 5.4×10^(−8) mm^(3)·N^(−1)·m^(−1).This relatively low thermal conductivity,combined with extraordi-nary mechanical properties,makes the proposed material an excellent candidate as a protective coating material for nuclear reactor components which require high strength,irradiation resistance,and thermal protection.

Optimum insulation thickness and exergy savings of building walls in Bamenda: a comparative analysis

The goal of this study is to examine the energetic,entransy,and exergetic methodologies employed to estimate the ideal insulation thickness for construction walls in terms of cost and ecological impact.To achieve these goals,the life cycle cost analysis-based insulating thicknesses of the various methods are evaluated along with the overall costs,yearly cost reductions,and total expenses.The fuel consumption,CO_(2) emissions,and ecological effects are then compared using an environmental analysis based on the three methodologies.The savings of hollow concrete brick(HCB),compressed stabilized earth brick(CSEB),and sundried earth brick(SEB)walls are evaluated along with the insulation thicknesses in terms of cost and ecological impact.As a result,it is determined that the exergetic technique is better suited for optimizing insulating thickness.For CSEB,SEB,and HCB walls,the economic ideal insulation thicknesses are 0.01 m,0.016 m,and 0.02 m,with yearly financial savings of 5$⋅m^(-2),7.5$⋅m^(-2),and 9$⋅m^(-2).For CSEB,SEB,and HCB walls,accordingly,the ecological optimal insulation thicknesses are 0.023 m,0.032 m,and 0.040 m,with net savings of exergetic ecological impact equal to 59 mPts⋅m^(-2),55 mPts⋅m^(-2),and 51 mPts⋅m^(-2).

Experimental evaluation of factors affecting performance of concentrating photovoltaic/thermal system integrated with phase‐change materials(PV/T‐CPCM)

The photovoltaic/thermal(PV/T)system is a promising option for countering energy shortages.To improve the performance of PV/T systems,compound parabolic concentrators(CPCs)and phase-change materials(PCMs)were jointly applied to construct a concentrating photovoltaic/thermal system integrated with phase-change materials(PV/T-CPCM).An open-air environment is used to analyze the effects of different parameters and the intermittent operation strategy on the system performance.The results indicate that the short-circuit current and open-circuit voltage are positively correlated with the solar irradiance,but the open-circuit voltage is negatively correlated with the temperature of the PV modules.When the solar irradiance is 500 W⋅m^(−2) and the temperature of the PV modules is 27.5℃,the short-circuit current and open-circuit voltage are 1.0 A and 44.5 V,respectively.Higher solar irradiance results in higher thermal power,whereas the thermal efficiency is under lower solar irradiance(136.2-167.1 W⋅m^(−2) is twice under higher solar irradiance(272.3-455.7 W⋅m^(−2))).In addition,a higher mass flow rate corresponds to a better cooling effect and greater pump energy consumption.When the mass flow rate increases from 0.01 to 0.02 kg⋅s^(-1),the temperature difference between the inlet and outlet decreases by 1.8℃,and the primary energy-saving efficiency decreases by 0.53%.The intermittent operation of a water pump can reduce the energy consumption of the system,and the combination of liquid cooling with PCMs provides better thermal regulation and energy-saving effects under various conditions.

Impacts of thermal and electric contact resistance on the material design in segmented thermoelectric generators

Segmented thermoelectric generators(STEGs)can exhibit present superior performance than those of the conventional thermoelectric generators.Thermal and electrical contact resistances exist between the thermoelectric material interfaces in each thermoelectric leg.This may significantly hinder performance improvement.In this study,a five-layer STEG with three pairs of thermoelectric(TE)materials was investigated considering the thermal and electrical contact resistances on the material contact surface.The STEG performance under different contact resistances with various combinations of TE materials were analyzed.The relationship between the material sequence and performance indicators under different contact resistances is established by machine learning.Based on the genetic algorithm,for each contact resistance combination,the optimal material sequences were identified by maximizing the electric power and energy conversion efficiency.To reveal the underlying mechanism that determines the heat-to-electrical performance,the total electrical resistance,output voltage,ZT value,and temperature distribution under each optimized scenario were analyzed.The STEG can augment the heat-to-electricity performance only at small contact resistances.A large contact resistance significantly reduces the performance.At an electrical contact resistance of RE=10^(-3) K⋅m^(2)⋅W^(-1) and thermal contact resistance of RT=10-8Ω⋅m^(2),the maximum electric power was reduced to 5.71 mW(90.86 mW without considering the contact resistance).And the maximum energy conversion efficiency is lowered to 2.54%(12.59%without considering the contact resistance).

Erratum regarding previously published articles

Owing to a Publisher error,the declaration of competing interest statements was not included in the published version of the following articles that appeared in previous issues of Energy Storage and Saving.The authors were contacted after publication to request a declaration of competing interest,however.

Experimental investigation of inflow-outflow asymmetry in induced-charge electro-osmosis

Induced-charge electro-osmosis(ICEO)is a research hotspot in bioengineering and analytical chemistry.Inflow-outflow asymmetry of ICEO was reported in the existing literatures,but systematic study on this phenomenon is insufficient.In this experimental study,we found that in strong electric fields,not only the velocity magnitude but also the vortex positions of ICEO are asymmetrical along the inflow and outflow directions because of the pronounced non-uniform surface electrokinetic transport.On the inflow and outflow directions,the amplitudes of velocities are unequal,ICEO maximum velocity positions change depending on the electric field intensity and sodium chloride(NaCl)concentration.Additionally,the distances between vortex centers are different.At NaCl solution concentration of 0.001 mol⋅L^(-1),the outflow velocity almost vanishes.The asymmetry rises with the increasing electric field intensity.The new discoveries can direct the application of microscale devices.

Influence of active and passive equipment for advanced pressurized water reactor on thermal hydraulic and source term behavior in severe accidents

Extensive studies have been carried out on the behavior of core degradation and fission products of common pressurized water reactors(PWRs).However,few of them have investigated the relationship between thermal hydraulic and fission product behavior in advanced passive PWRs.Due to the impact of thermal hydraulic be-haviors in different accident sequences on the release and transportation of fission products,an integrated severe accident analysis(ISAA)code with highly coupled thermal hydraulic and source term calculations is required to simultaneously analyze thermal hydraulic and source term behavior.For advanced passive PWRs,important safety systems that may affect the behavior of the core and fission products should be considered.It is therefore necessary to simulate the thermal hydraulic and fission product behavior of advanced passive PWRs.In this study,the ISAA code is adopted to simulate the occurrence of a hypothetical double ended cold leg LBLOCA of HPR1000 in three scenarios of equipment failure.The results show that the high-temperature fuel rods and cladding ma-terials exhibit delayed failure at the lower position of the active core,whereas earlier failure at higher position during the reflooding.Active and passive equipment affects fuel temperature,the oxidation conditions of the fuel,the interaction of fission products and structural materials,and the state of the fuel,thereby affecting the release of fission products in the fuel.HPR1000 only relies on passive equipment to relieve the core degradation in severe accidents,realize the in-vessel retention of melt,and eliminate the ex-vessel release possibility of fission product.It is hoped that the results can provide references for HPR1000 to formulate the severe accident management guidelines(SAMG).

Molecular simulation on carbon dioxide capture performance for carbons doped with various elements

Among the different types of CO_(2)capture technologies for post-combustion,sorption CO_(2)capture technology with carbon-based sorbents have been extensively explored with the purpose of enhancing their sorption perfor-mance by doping hetero elements due to the rapid reaction kinetics and low costs.Herein,sorption capacity and selectivity for CO_(2)and N 2 on carbon-based sorbents doped with elements such as nitrogen,sulfur,phosphorus,and boron,are evaluated and compared using the grand canonical Monte Carlo(GCMC)method,the universal force field(UFF),and transferable potentials for phase equilibria(TraPPE).The sorption capacities of N-doped porous carbons(PCs)at 50℃were 76.1%,70.7%,50.6%,and 35.7%higher than those of pure PCs,S-doped PCs,P-doped PCs,and B-doped PCs,respectively.Its sorption selectivity at 50℃was approximately 14.0,nearly twice that of pure PCs or other hetero-element-doped PCs.The N-doped PCs showed the largest sorption heat at 50℃among all the PCs,approximately 20.6 kJ·mol^(−1),which was 9.7%−25.5%higher than that of the pure PCs under post-combustion conditions.Additionally,with the product purity of 41.7 vol.%−75.9 vol.%for vacuum pressure swing sorption,and 53.4 vol.%−83.6 vol.%for temperature swing sorption,the latter is more suitable for post-combustion conditions than pressure-swing sorption.

Thermal performance of a metal hydride reactor for hydrogen storage with cooling/heating by natural convection

Metal hydride(MH)systems can be used for storage in stationary facilities of hydrogen with a high volume density at temperatures and pressures close to ambient ones.Recently,the possibility of using passive heating/cooling systems or regenerative heat exchangers has been studied to improve the energy efficiency of MH systems for hydrogen storage without the need for forced circulation of a heating/cooling fluid.Natural convection of air may be used to passively remove/add heat as required for proper operation of a MH reactor.Under these conditions,the MH reactor can operate at a constant ambient air temperature and be driven by a difference in pressure between the source and the consumer of hydrogen.Since operation of MH systems with natural convective heating/cooling has not been systematically investigated as yet,a tubular MH reactor based on this principle is examined in this paper.Two-thirds of the internal volume ofø25.4×1 mm tube is occupied by a composition of LaNi5 and aluminium foam(one linear metre contains 1.1 kg of LaNi5 with a hydrogen capacity of 153 NL H2).Annular fins are used to increase heat transfer to air.Detailed and simplified mathematical models of the systems of this class are proposed and validated.It is shown that acceptable hydrogen charging/discharging rates in such systems are achieved with proper selection of fining characteristics.Charging from a hydrogen source at a pressure of 10 atm and an ambient air temperature of 10 to 30℃ takes 15 min.A reactor with a length of 1 m can desorb almost all stored hydrogen at a minimum outlet pressure of 0.45 bar to feed 30-300 W fuel cells.

Experimental study and numerical analysis of vacuum thermal characteristics of brush DC motor

Brush direct current(DC)motors have several qualities that make them very attractive for space flight applica-tions.Considering the high reliability requirements of aerospace missions,the thermal characteristics and ther-mal failure of the brush DC motor in the space environment were studied.Using a motor thermal resistance network model,a special thermal test method was determined and combined with a thermal conductivity anal-ysis model,the thermal parameters were obtained via item-by-item stripping,and the motor temperature field was constructed.By introducing the arc discharge factor to evaluate the electric-corrosion heat consumption,the numerical analysis results were in good agreement with the test results under the conditions of stalled rotor,nor-mal rotation,single brush,and multiple brushes.The analysis and test results show that continuous operation for 110 s will lead to melting of the brush solder joints,and electrical corrosion heat consumption is one of the main factors that cannot be ignored.The reliability model of vacuum applications should be established in the normal working mode of at least two brushes in both the positive and negative electrodes.To improve the reliability,a sealed air-filled structure of the motor was proposed,a heat-flow co-simulation model of a continuous medium flow with a large curvature and constant without a gravity field was established,and the temperature and ve-locity fields under different sealed pressures were obtained.The results show that the temperature of the single brush reduced to below 140°C from 204.5°C in vacuum,which can meet the long-term continuous working requirement of high reliability of brush motors in space missions.In addition,it was found that with the decrease in pressure,the effect of convective heat transfer gradually weakens,the temperature gradually increases and converges to the unique heat conduction process of the gas,while the effect of convection is negligible.As the pressure continues to decrease,the sealed gas evolves from continuous medium flow to transitional and free molecular flow,and the heat conduction effect of the gas weakens again until it approaches the singleness solid conduction process.

Comparative study on the globally optimal performance of cryogenic energy storage systems with different working media

Cryogenic energy storage(CES)has garnered attention as a large-scale electric energy storage technology for the storage and regulation of intermittent renewable electric energy in power networks.Nitrogen and argon can be found in the air,whereas methane is the primary component of natural gas,an important clean energy resource.Most research on CES focuses on liquid air energy storage(LAES),with its typical round-trip efficiency(RTE)being approximately 50%(theoretical).This study aims to explore the feasibility of using different gases as working media in CES systems,and consequently,to achieve a high system efficiency by constructing four steady-state process models for the CES systems with air,nitrogen,argon,and methane as working media using Aspen HYSYS.A combined single-parameter analysis and multi-parameter global optimization method was used for system optimization.Further,a group of key independent variables were analysed carefully to determine their reasonable ranges to achieve the ideal system performance,that is,RTE and liquefaction ratio through a single-parameter analysis.Consequently,a multi-parameter genetic algorithm was adopted to globally optimize the CES systems with different working media,and the energy and exergy analyses were conducted for the CES systems under their optimal conditions.The results indicated the high cycle efficiency of methane and a low irreversible loss in the liquefaction cycle.Moreover,the Joule-Thomson valve inlet temperature and charging and discharging pressures considerably affected the system performance.However,exergy loss in the CES system occurred primarily in the compressor,turbine,and liquefaction processes.The maximum optimal RTE of 55.84%was achieved in the liquid methane energy storage(LMES)system.Therefore,the LMES system is expected to exhibit potential for application in the CES technology to realize the integration of natural gas pipelines with renewable power grids on a large scale.Moreover,the results of study have important theoretical significance for the innovation of the CES technology.

Electrification and decarbonization: a critical review of interconnected sectors, policies, and sustainable development goals

Climate actions(SDG-13)aim at limiting global warming by targeting carbon emissions reduction.With the energy industry recognized as a significant CO_(2) emitter,SDG-13 policies mostly translate energy transition to renewables(SDG-7)and the electrification of end-users,both energy-demanding sectors and society(cities,households,and mobility).The double-layered actions parallel the classical“cascade control”employed in industrial sectors.For achieving deep decarbonization,the ambitious net-zero emissions(NZE),large-scale deployment of renewables demand storage,with hydrogen as a prominent chemical storage alternative,and carbon capture&storage(CCS)for hard-to-electrify sectors.Infrastructure developments need policy and capital investments,and geopolitics and resource availability challenge and offer opportunities.Since decarbonization and electrification have multiple realization paths and impact the industrial metabolism,SDGs are interconnected with synergies and trade-offs.Prioritization of SDGs by policymakers is necessary for resilience and robustness in achieving climate goals within a systems dynamics approach.This critical review identifies niches in decarbonization and electrification,enlightening the industrial metabolism under the lens of SDGs.

Optimal allocation method of energy storage for integrated renewable generation plants based on power market simulation

This study designs and proposes a method for evaluating the configuration of energy storage for integrated re-newable generation plants in the power spot market,which adopts a two-level optimization model of“system simulation+plant optimization”.The first step is“system simulation”which is using the power market simu-lation model to obtain the initial nodal marginal price and curtailment of the integrated renewable generation plant.The second step is“plant optimization”which is using the operation optimization model of the integrated renewable generation plant to optimize the charge-discharge operation of energy storage.In the third step,“sys-tem simulation”is conducted again,and the combined power of renewable and energy storage inside the plant is brought into the system model and simulated again for 8,760 h of power market year-round to quantify and compare the power generation and revenue of the integrated renewable generation plant after applying energy storage.In the case analysis of the provincial power spot market,an empirical analysis of a 1 GW wind-solar-storage integrated generation plant was conducted.The results show that the economic benefit of energy storage is approximately proportional to its capacity and that there is a slowdown in the growth of economic benefits when the capacity is too large.In the case that the investment benefit of energy storage only considers the in-come of electric energy-related incomes and does not consider the income of capacity mechanism and auxiliary services,the income of energy storage cannot fulfill the economic requirements of energy storage investment.

The effects of industrial policymaking on the economics of low-emission technologies: the TRANSid model

Basic materials such as steel,cement,aluminium,and(petro)chemicals are the building blocks of industrialised societies.However,their production is extremely energy and emission intensive,and these industries need to decarbonise their emissions over the next decades to keep global warming at least below 2°C.Low-emission industrial-scale production processes are not commercially available for any of these basic materials and require policy support to ensure their large-scale diffusion over the upcoming decades.The novel transition to industry decarbonisation(TRANSid)model analyses the framework conditions that enable large-scale investment decisions in climate-friendly basic material options.We present a simplified case study of the cement sector to demonstrate the process by which the model optimises investment and operational costs in carbon capture technology by 2050.Furthermore,we demonstrate that extending the model to other sectors allows for the analysis of industry-and sector-specific policy options.

Comparative study on heat transfer enhancement of metal foam and fins in a shell-and-tube latent heat thermal energy storage unit

Metal foam and fins are two popular structures that are employed to enhance the heat transfer of phase change materials in shell-and-tube heat storage units.However,it remains unclear which structure is better in terms of energy storage performance.In this study,the heat transfer enhancement performances of metal foam and fins are compared to provide guidance on the optimal structure to be chosen for practical applications.Three fin structures(four fins,two vertical fins,and two horizontal fins)are considered.Under the full configuration(volume fraction of metal=3%),the unit with four fins was found to have a faster melting rate than those with vertical or horizontal fins.In other words,increasing the number of fins helps to accelerate the melting process.Nevertheless,the unit with metal foam enhancement has the highest melting rate.Under the half configuration(volume fraction of metal=1.5%),the melting rate of the unit enhanced by metal foam is significantly decreased,whereas there is no remarkable changes in the units enhanced by fins.However,metal foam is still shown to be the best thermal enhancer.The energy storage rate of the unit enhanced by metal foam can be up to 10 times higher than that of the unit enhanced by fins.

Strength analysis of molten salt tanks for concentrating solar power plants

Promoting the development of concentrating solar power(CSP)is critical to achieve carbon peaking and carbon neutrality.Molten salt tanks are important thermal energy storage components in CSP systems.In this study,the cold and hot tanks of a 100 MW CSP plant in China were used as modeling prototypes.The materials and geometric models were determined based on related specifications and engineering experience.Mechanical characteristics of the tanks under steady condition,including the deformation,stress distribution,and stress concentration,were simulated and calculated.Furthermore,the strength of the tank walls was evaluated.The findings can be used as a reference for designing the molten salt storage tank and reducing the risk during the operation.

Numerical investigation of a latent cold storage system using shell-and-tube unit

The use of cold thermal storage systems in low-temperature industrial applications is considered one of the most promising ways of improving energy efficiency and reducing the use of power during peak periods.In this study,the thermal performance of a shell-and-tube cold storage system under realistic operating conditions is investigated numerically.The proposed model is developed based on energy balances and then validated using existing experimental data from the literature.Glycol/water is used as the heat transfer fluid(HTF)and the phase transition phenomena in the phase change material(PCM)is simulated using the enthalpy-porosity approach.The influence of several design and operating parameters,including the HTF mass flow rate,HTF temperature,PCM type,and volume,on the cold storage performance during the crystallization process is presented and analyzed.The numerical results show that increasing the HTF mass flow rate accelerates the PCM crystallization process.However,the delivery periods of constant thermal power and constant HTF outlet temperature are reduced.The HTF inlet temperature has a significant effect on the cold storage performance,and the complete charging period is reduced by approximately 37%when the HTF inlet temperature is reduced from−4°C to−7°C.Increasing the number of tubes in the cold storage unit is concluded to significantly improve the thermal performance of the system,and using water/ice as a cold storage medium is more suitable than using the commercial PCMs RT2-HC and RT4-HC.Finally,the proposed numerical model for cold storage systems can be successfully used to design and simulate their realistic operation under different conditions.