Decreasing the levelized cost of renewable energy and improving the stability of power systems are the key requirements for realizing the sustainable growth of power production capacity. Concentrating solar power (CSP) technology with thermal energy storage can overcome the intermittent and unstable nature of solar energy, and its development is of great significance for the sustainable development of human society. In this paper, topic discovery and clustering were studied using bibliometric, social network analysis and information visualization technology based on the Web of Science database (SCI-Expanded) and the incoPat global patent database. The technology searched for papers and patents related to CSP technology to reveal the development trends of CSP technology and provide the references for related technical layout and hot spot tracking. The results show that the global output of CSP technology papers has continued to grow steadily, whereas the number of patent applications sh... [more]

The present paper deals with the theoretical evaluation of the efficiency of an array of cylindrical Wave Energy Converters (WECs) having a vertical symmetry axis and placed in front of a reflecting vertical breakwater. Linear potential theory is assumed, and the associated diffraction and motion radiation problems are solved in the frequency domain. Axisymmetric eigenfunction expansions of the velocity potential are introduced into properly defined ring-shaped fluid regions surrounding each body of the array. The potential solutions are matched at the boundaries of adjacent fluid regions by enforcing continuity of the hydrodynamic pressures and redial velocities. A theoretical model for the evaluation of the WECs’ performance is developed. The model properly accounts for the effect of the breakwater on each body’s hydrodynamic characteristics and the coupling between the bodies’ motions and the power take-off mechanism. Numerical results are presented and discussed in terms of the exp... [more]

Tidal stream turbines are subject to complex flow conditions, particularly when installed in staggered array configurations where the downstream turbines are affected by the wake and/or bypass flow of upstream turbines. This work presents, for the first time, methods for and results from the physical testing of three 1/15 scale instrumented turbines configured in a closely-spaced staggered array, and demonstrates experimentally that increased power extraction can be achieved through reduced array separation. A comprehensive set of flow measurements was taken during several weeks testing in the FloWave Ocean Energy Research Facility, with different configurations of turbines installed in the tank in a current of 0.8 m/s, to understand the effect that the front turbines have on flow through the array and on the inflow to the centrally placed rearmost turbine. Loads on the turbine structure, rotor, and blade roots were measured along with the rotational speed of the rotor to asses... [more]

The complexity of floating offshore wind turbine (FOWT) systems, with their coupled motions, aero-hydro-servo-elastic dynamics, as well as non-linear system behavior and components, makes modeling and simulation indispensable. To ensure the correct implementation of the multi-physics, the engineering models and codes have to be verified and, subsequently, validated for proving the realistic representation of the real system behavior. Within the IEA (International Energy Agency) Wind Task 23 Subtask 2 offshore code-to-code comparisons have been performed. Based on these studies, using the OC3 phase IV spar-buoy FOWT system, the Modelica for Wind Turbines (MoWiT) library, developed at Fraunhofer IWES, is verified. MoWiT is capable of fully-coupled aero-hydro-servo-elastic simulations of wind turbine systems, onshore, offshore bottom-fixed, or even offshore floating. The hierarchical programing and multibody approach in the object-oriented and equation-based modeling language Modelica hav... [more]

The current work was aimed at developing a new conditioning method of spent electrolyte-radioactive waste (RW) generated during the pyrochemical reprocessing of mixed nitride uranium-plutonium spent nuclear fuel. Magnesium potassium phosphate (MPP) compound samples were synthesized under solidification of the electrolyte surrogate solution in a LiCl-KCl-CsCl system. The phase composition and structure of obtained compounds were studied by XRD and SEM-EDS methods. It was found that the compounds possessed a high compressive strength of 17−26 MPa. Hydrolytic stability of the compounds was evaluated in accordance with the long semi-dynamic test GOST R 52126-2003 and with the static PCT test. The 137Cs content in the leached solutions was determined by gamma-ray spectrometry, and other compound components were determined by ICP−AES and ICP−MS methods. The differential leaching rate of Cs at 25 °C from monolithic samples on the 91st day of samples contact with water was 5−11 × 10−5 g/(cm2·d... [more]

It is imperative to have an in-depth understanding of the effect of extraneous moisture on the spontaneous combustion of coal not only for the control and prevention of coal spontaneous combustion in the coal mining industry, but also for the optimization design and application of the technological process. In this study, the type of moisture in a coal body has been redefined for the first time from the perspective of disaster prevention and control, i.e., original occurrence of moisture in the coal matrix and the extraneous moisture from the technological process. A suit of coal bodies with different extraneous moisture was prepared by soaking long-flame coal with a low water content. Using a temperature-programmed oxidation test, the effects of extraneous moisture on the temperature increase rate of coal bodies and the emission characteristics of gaseous products during coal spontaneous combustion were studied. Moreover, combined with the characterization of thermal analysis and of p... [more]

The energy consumption of buildings is very important for both economic and environmental reasons. Newly built buildings are characterized by higher insulation and airtightness of the building envelope, and are additionally equipped with technologies that minimize energy consumption in order to meet legal requirements. In existing buildings, the modernization process should be properly planned, taking into account available technologies and implementation possibilities. Hotel buildings are characterized by a large variability of energy demand, both on a daily and a yearly basis. Monitoring systems, therefore, provide the necessary information needed for proper energy management in the building. This article presents an energy analysis of the Turówka hotel located in Wieliczka (southern Poland). The historical hotel facility is being modernized as part of the project to adapt the building to the requirements of a sustainable building. The modernization proposal includes a trigeneration... [more]

Selection of the optimal properties of coal as a natural sorbent, both as a sample collected from a seam or of the coal seam itself, requires various parameters to be determined and may not be based on the knowledge of metamorphism degree only. In order to improve the predictions of sorption capacity and the kinetics, analyses of correlation and multiple regression based on the results of laboratory studies were performed for 15 coal samples with various coal rank. The maximum vitrinite reflectance (R0) for low-rank coals was 0.78%−0.85%, and 0.98%−1.15% and 1.85%−2.03% for medium- and high-rank coals, respectively. Coal samples were subjected to technical and petrographic analysis. The gravimetric method was used to perform sorption tests using methane, in order to determine the sorption capacity and the effective diffusion coefficient for each of the coals. Pycnometric methods were used to determine the textural parameters of coals, such as the percentage porosity and specific pore v... [more]

This paper presents the results of energy analysis of absorption heat pumps. The thermo-chemical instability term was introduced for absorption heat pumps used for heating or cooling or heating and cooling. A higher thermo-chemical instability results in the equipment being more sensitive with regard to the variation of the heat source flux. This sensitivity can be taken into account when heat sources are chosen for a certain absorption machine. Absorption heat pumps having thermo-chemical compressors were compared from energy demand and energy efficiency points of view with heat pumps having mechanical compressors. As it is shown, for certain evaporation and condensation temperature values, an absorption heat pump with similar efficiency to that of the heat pump with a mechanical compressor can always be found.

With the rapid development of electric vehicles (EVs), one of the urgent issues is how to deploy limited charging facilities to provide services for as many EVs as possible. This paper proposes a bilevel model to depict the interaction between traffic flow distribution and the location of charging stations (CSs) in the EVs and gasoline vehicles (GVs) hybrid network. The upper level model is a maximum flow-covering model where the CSs are deployed on links with higher demands. The lower level model is a stochastic user equilibrium model under elastic demands (SUE-ED) that considers both demands uncertainty and perceived path constraints, which have a significant influence on the distribution of link flow. Besides the path travel cost, the utility of charging facilities, charging speed, and waiting time at CSs due to space capacity restraint are also considered for the EVs when making a path assignment in the lower level model. A mixed-integer nonlinear program is constructed, and the eq... [more]

In the present paper, the heat transfer of gravity-driven dense particle flow around five different shapes of tubes is numerically studied using discrete element method (DEM). The velocity vector, particle contact number, particle contact time and heat transfer coefficient of particle flow at different particle zones around the tube are carefully analyzed. The results show that the effect of tube shape on the particle flow at both upstream and downstream regions of different tubes are remarkable. A particle stagnation zone and particle cavity zone are formed at the upstream and downstream regions of all the tubes. Both the stagnation and cavity zones for the circular tube are the largest, and they are the smallest for the elliptical tube. As the particle outlet velocity (vout) changes from 0.5 mm/s to 8 mm/s at dp = 1.72 mm/s, when compared with the circular tube, the heat transfer coefficient of particle flow for the elliptical tube and flat elliptical tube can increase by 20.3% and 1... [more]

Electrical energy is the highest energetic cost in recirculation aquaponic systems (RASs), especially for fish-tank water. Therefore, reducing energy consumption is one of the challenges in developing RAS models. In this study, eleven experimental setups, based on numerical models from an earlier investigator, were built to investigate. Among them, three additional cases (cases 9−11) investigated the transient discharging energy efficiency of thermal energy storage (TES). Cases 9−11 considered three temperature levels, namely, 65−75 °C, 71−81 °C, and 81−87 °C, with a mass flow rate of 0.166 kg/s. The results show that when heating 3.4 m3 of fish tank water from 24.5 °C to 28 °C, the average temperature error of the tank water was between 1.2% and 3.4%. The difference in the heat transfer rate was within ±4.2%. The error in the thermal efficiency was below 8.0%. The error range of the total required thermal energy was from 6.4% to 11.5%. Cases 9−11 used 5.6%, 6.4%, and 7.2% of the therm... [more]

This paper took a two-stage turbocharged heavy-duty six-cylinder diesel engine as the research object and established a two-stage turbocharging system matching model. The influence rules between the two-stage turbocharging key parameters were analyzed, while summarizing an optimization method of key parameters of a two-stage turbocharger. The constraint equations for the optimal distribution principle of the two-stage turbocharger’s pressure ratio and expansion ratio were proposed. The results show that when the pressure ratio constraint equation and expansion ratio constraint equation are satisfied, the diesel engine can achieve the target pressure ratio, while the total energy consumption of the turbocharger is the lowest.

The paper assesses the impact of combustion of biofuels produced based on municipal sewage sludge in stoker-fired boilers on the amount of pollutant emissions and examines the tendency of ash deposition of biofuels formed during the combustion process. The combustion tests were performed in a laboratory system enabling simulation of a combustion process present in stoker-fired boilers. The study was conducted for three types of biofuels; i.e., fuel from sewage sludge and coal slime (PBS fuel), sewage sludge and meat and bone meal (PBM fuel) and fuel based on sewage sludge and sawdust (PBT) with particle size of 35 mm and 15 mm. This paper describes and compares the combustion process of biofuels with different granulation and composition and presents the results of changes in emission values of NOx, SO2, CO, and CO2. The emission results were compared with the corresponding results obtained during combustion of hard coal. The results showed that biofuels with lower particle sizes were... [more]

The approval and evaluation process for sustainable aviation fuels (SAF) via ASTM D4054 is both cost- and volume-intensive, namely due to engine operability testing under severe conditions. Engine operability tests of combustor under figures of merit (FOM) limit phenomena are the fuel effects on lean blowout, high-altitude relight, and cold-start ignition. One method to increase confidence and reduce volume in tiered testing is to use surrogate fuels for manipulation of properties. Key fuel performance properties (surface tension, viscosity, density) for cold-start ignition was determined prior to this study. Prior work regarding this FOM has not considered the combination of these properties. A surface tension blending rule was validated and incorporated into the jet fuel blend optimizer (JudO). A generalized surrogate calculator for N-dimensional surrogate components and features was developed. Jet fuel surrogates developed in this study were a mixture of conventional and sustainable... [more]

Ti-V-based body-centered cubic (BCC) alloys have potential for large-scale hydrogen storage if expensive vanadium is substituted with much cheaper Fe-containing ferrovanadium. Use of ferrovanadium reduces the alloys’ hydrogen storage capacity. This is puzzling since the amount of Fe is low and hydrogen atoms are accommodated in interstitial sites which are partly coordinated by Fe in many intermetallic compounds. The present work is aimed at finding a structural explanation for Fe-induced capacity loss in Ti-V alloys. Since such alloys and their hydrides are highly disordered without long-range occupational order of the different metal species, it was necessary to employ a technique which is sensitive to local structure. Neutron total scattering coupled with reverse Monte Carlo modelling was thus employed to elucidate short-range atomic correlations in Ti0.63V0.27Fe0.10D1.73 from the pair distribution function. It was found that Fe atoms form clusters and that the majority of the vacan... [more]

Energy transformation by power electronic converters is not feasible without the efficient use of renewable energy. The article tries to extend the use of renewable energy to PHEV battery charging. In PHEV, the battery is one of the major sources of stored energy. The converter used for charging these batteries is of crucial concern. The paper addresses various challenges in designing a DC to DC converter for battery charging in DC bus. An optimized converter is designed to work with renewable energy sources to accomplish a high boost ratio, low input current ripple, low output voltage ripple, high power efficiency, and high power density. A combination of two interleaved boost converters is effectively used with the overlap time switching to achieve a high voltage boost ratio in forming the DC bus. Transformer isolation is used to increase reliability and boost ratio further. The secondary side employs a series-connected voltage doubler. The converter boosts an input voltage of 24 V t... [more]

Driven by the transformation of the energy structure, China’s photovoltaic (PV) power generation industry has made remarkable achievements in recent years. However, there are more than 30 regions (cities/provinces) in China, and the economic, policy, technological, and the environmental conditions of each region are significantly different, which leads to a huge discrepancy in PV power generation efficiency. To address the imbalance in the development of PV industry, first, this paper employed the integrated fuzzy analytic hierarchy process−data envelopment analysis (FAHP−DEA) model to evaluate the PV power generation efficiency of 30 regions in China. Second, Tobit regression model was used to examine the effects of 9 potential influencing factors. Third, a concrete analysis was conducted, and discussion based on the efficiency rankings and regression results was made. Additionally, the FAHP−DEA model proposed in this study can also be applied to the efficiency evaluation issues of ot... [more]

The outburst of population as well as increasing industrialisation have triggered a very prominent imbalance between electricity demand and supply in emerging economies such as Indonesia. Based on this premise, electricity generation and distribution firms such as Perusahaan Listrik Negara (PLN) are faced with an urgent need to enhance availability and reliability through capacity expansion as well as the institutionalisation of cost-effective maintenance and asset management (MAM) principles. Some of the principles recommended here involve embedding customised overall health index (OHI) and total life cycle cost (LCC) estimation principles into engineering decisions that relate to asset renewal and/or replacement. While discussions about the fundamental theories and estimation approaches for OHI and LCC for power transformers (PTs) already exist in the current body of literature, however, they are mostly in a generic form which has somewhat limited proper implementation of these valua... [more]

Three load matching indicators (self-consumption rate, self-sufficiency rate, loss of load probability) and the CO2 emissions were evaluated for 55 Cypriot households with 3 kWp rooftop photovoltaic (PV) generators. The calculations were performed using 30-minute generation and consumption data from a large scale smart meter project in Cyprus. To investigate the effects of recent advances in local legislation, an analysis for higher PV capacities (5 kWp and 10 kWp) was also performed. The PV generation profiles for 5 kWp and 10 kWp PVs were obtained by scaling the 3 kWp PV generation profiles. The results showed that the self-consumption of the analyzed households varied seasonally, as it was related to their heating and cooling demand. More interestingly, the ratio between the households’ annual electricity generation and demand, formally defined here as generation-to-demand ratio (GTDR), was found to be related to the value ranges of the studied load matching indicators. Hence, on av... [more]

With the rapid development of new energy vehicles (NEVs) industry in China, the reusing of retired power batteries is becoming increasingly urgent. In this paper, the critical issues for power batteries reusing in China are systematically studied. First, the strategic value of power batteries reusing, and the main modes of battery reusing are analyzed. Second, the economic benefit models of power batteries echelon utilization and recycling are constructed. Finally, the economic benefits of lithium iron phosphate (LIP) battery and ternary lithium (TL) battery under different reusing modes are analyzed based on the economic benefit models. The results show that when the industrial chain is fully coordinated, LIP battery echelon utilization is profitable based on a reasonable scenario scheme. However, the multi-level echelon utilization is only practical under an ideal scenario, and more attention should be paid to the first level echelon utilization. Besides, the performance matching of... [more]

This paper holds a critical review of current research activities dealing with smart architectural glazing worldwide. Hereafter, the main trends are analyzed and critically reported, with open issues, challenges, and opportunities, providing an accurate description of technological evolution of devices in time. This manuscript deals with some well-known, highly performing technologies, such as semitransparent photovoltaics and novel photoelectrochromic devices, the readiest, probably, to reach the final stage of development, to disclose the manifold advantages of multifunctional, smart glazing. The complex, overall effects of their building integration are also reported, especially regarding energy balance and indoor visual comfort in buildings.

This study focuses on the analysis of the parameters of an oscillating water column (OWC) wave energy conversion system and wave conditions. Interactions between the dimensions of the OWC chambers and wave conditions are all taken into account to design an alternative OWC converter, called caisson-based OWC type wave energy converting system. A numerical method using an unsteady Navier-Stokes equations theorem in conservation form is used to analyze the proposed analytical model. The objective of this study is to try to apply an OWC wave energy converter to a caisson breakwater, which has been constructed in a harbor. The structure proposed in this study is a series of sets of independent systems, in which each set of converters is composed of three chambers to capture the wave energy, while better ensuring the safety of the caisson breakwater. Responses to be analyzed related to the conversion efficiency of the caisson-based OWC wave energy converting system include the airflow veloci... [more]

Coal burst occurrences are affected by a range of mining and geological factors. Excessive slipping between the strata layers may release a considerable amount of strain energy, which can be destructive. A competent strata is also more vulnerable to riveting a large amount of strain energy. If the stored energy in the rigid roof reaches a certain level, it will be released suddenly which can create a serious dynamic reaction leading to coal burst incidents. In this paper, a new damage model based on the modified thermomechanical continuum constitutive model in coal mass and the contact layers between the rock and coal mass is proposed. The original continuum constitutive model was initially developed for the cemented granular materials. The application of the modified continuum constitutive model is the key aspect to understand the momentum energy between the coal−rock interactions. The transformed energy between the coal mass and different strata layers will be analytically demonstrat... [more]

This paper presents an overview of the DC link development and evolution dedicated to HVDC structure for connecting offshore wind power plants to onshore power systems. The growing demand for the green energy has forced investors in power industry to look for resources further out at sea. Hence, the development of power electronics and industrial engineering has enabled offshore wind farms to be situated further from the shore and in deeper waters. However, their development will require, among other technologies, DC-DC conversion systems. The advantages of HVDC over HVAC technology in relation to transmission distance are given. The different HVDC configurations and topologies of HVDC converters are elucidated. In this context, the HVDC grids are a promising alternative for the expansion of the existing AC grid.