This study assesses the performance of a solid-state semiconductor-based hybrid photovoltaic-thermoelectric device that aims to harness both solar irradiance and heat dissipated from photovoltaic cells operating in Foz do Iguaçu city. Initially, the technologies involved, and the arrangement of the proposed device are presented; the modeling process of the generator operation under local operating conditions and taking into account solar energy availability is described later. The thermal energy harvesting brings out an average annual efficiency gain of 4.42% and a maximum efficiency increase of 6.05% (in the fall equinox) compared to standalone PV cell operation. The power output increase due to the utilization of the heat dissipated by the PV cells was substantial, reaching values ranging from 14.82% to 40.54%, depending on the time of year. The novelty of this research stems from the field power generation forecast, in southern hemisphere, for a new STEG device that combines photovo... [more]

Conventional sensor nodes are often battery-powered, and battery power limits the overall lifetime of the wireless sensor networks (WSNs). Wireless charging technology can be implemented in WSNs to supply power to sensor nodes and resolve the problem of restricted battery power. This type of mixed network is called wireless rechargeable sensor networks (WRSNs). Therefore, wireless charger deployment is a crucial task in WRSNs. In this study, the method of placing wireless chargers to efficiently extend the lifetime of the WRSNs is addressed. Owing to the data forwarding effect in WSNs, sensor nodes that are closer to the data collection or sink node drain more power than nodes that are further away from the data collection or sink node. Therefore, this study proposes a novel hybrid search and removal strategy for the power balance charger deployment method. The wireless chargers are placed in the chosen nodes of the WRSNs. The node-chosen problem we address is called the dominating set... [more]

The use of photovoltaic solar technology is increasingly widespread and consolidated worldwide, gaining significant interest in Brazil. Thanks to records of gradual photovoltaic system price decreases and the construction of legal frameworks favorable to their diffusion, urban and rural residential consumers, service companies, industries, and the government are progressively adhering to the use of this technology. In this context, it is important that institutions and companies with multiheadquarters discern whether it is more advantageous, from both a technical and economic point of view, to disperse photovoltaic systems throughout all of their headquarters or to centralize them in the offices presenting the best energy efficiency. The present study aims at answering this question. To this end, indicators recorded in the Institute of Education Science and Technology (IFRN)-Solar Project implemented by the Rio Grande do Norte Federal Institute of Education, Science and Technology, in... [more]

Heat exchanger network (HEN) retrofit is a vital task in the process design to improve energy savings. Various types of heat exchangers such as shell and tube, double-pipe, compact plate, and spiral tube have their working temperature ranges and costs. Selecting suitable types of heat exchangers according to their temperature ranges and costs is a crucial aspect of industrial implementation. However, considering the type of heat exchangers in the HEN retrofit process is rarely seen in previous publications. This issue can be solved by the proposed Shifted Retrofit Thermodynamic Grid Diagram with the Shifted Temperature Range of Heat Exchangers (SRTGD-STR). The temperature ranges of six widely used heat exchanger types are coupled in the grid diagram. This diagram enables the visualisation of identifying the potential retrofit plan of HEN with heat-exchanger type selection. The retrofit design aims to minimise utility cost and capital cost. An illustrative example and a case study are p... [more]

Measurements such as current and terminal voltage that are typically used to determine the battery’s state of charge (SOC) are augmented with measured force associated with electrode expansion as the lithium intercalates in its structure. The combination of the sensed behavior is shown to improve SOC estimation even for the lithium ion iron phosphate (LFP) chemistry, where the voltage−SOC relation is flat (low slope) making SOC estimation using measured voltage difficult. For the LFP cells, the measured force has a non-monotonic F−SOC relationship. This presents a challenge for estimation as multiple force values can correspond to the same SOC. The traditional linear quadratic estimator can be driven to an incorrect SOC value. To address these difficulties, a novel switching estimation gain is used based on determining the operating region that corresponds to the actual SOC. Moreover, a drift in the measured force associated with a shift of the cell SOC−expansion behavior over time is... [more]

This work describes the experimental characterization of a commercial sodium−nickel chloride battery and the investigation on a state-of-the-art model that represents the battery behavior. This battery technology is considered very promising but it has not fully been exploited yet. Besides improvements on the technological side, accurate models of the battery should be found to allow the realization of Battery Management Systems with advanced functions. This achievement may extend the battery exploitation to its best. The paper describes the experimental set-up and the model parameter identification process, and discusses the identified parameters and the model validation tests. The comparison between model simulations and experiments shows that the model is rather accurate for low-current rates, but it loses accuracy and it is not able to reproduce with fidelity the battery behavior at low states of charge or at high current rates. Further research efforts and refinements of the model... [more]

Piezoelectric energy harvesters can scavenge energy from their ambient environment in order to power low-consumption electronic devices. The last two decades have seen a growing interest towards vortex-induced vibration harvesters; most harvesters consist in rigid splitter plates oscillating at higher frequencies. The concept presented here is a low-frequency undulating flexible plate placed in the wake of a square cylinder. Piezoelectric patches can be placed at the plate surface to harvest the strain energy arising when the plate bends. The flapping pattern mimics an anguilliform swimming motion. There is a great need to establish correlation between wake generating bluff body size, plate dimensions and power output. Geometric parameters were investigated using water tunnel experiments, particle image velocimetry and fluid−structure interaction modeling. Results showed that for a given plate length and within a given freestream velocity range, there is a square cylinder diameter and... [more]

The selection of cost-effective components of the building envelope plays a significant role in a sustainable building design solution. Therefore, in terms of effective decision-making, it is important to have a complete insight into construction and running costs throughout the lifespan of the building. A systematic building information modelling (BIM) approach as a new trend in the innovative approaches in the construction (AECO) industry provides appropriate support for improvement of environmental assessments. Our study presents a new approach to automated/semi-automated comprehensive energy and the whole life-cycle cost analysis of building envelope components using BIM, and, as such, it represents a novelty for Advanced Construction Project Management. It focuses on the sequence of steps required for evaluation of energy and economic assessment, from the basic 3D BIM model, through the energy and cost analysis, to the final evaluation and decision-making. The energy balance was c... [more]

The efficiency and reliability of blades are key indicators for a tidal current turbine (TCT). A traditional blade design is often an empirical design on hydrodynamics and structure, sequentially. A hydrofoil with a low lift−drag ratio is considered when the structural strength cannot satisfy requirements. However, efficiency is then sacrificed. A redundant design is generally adopted to protect from load uncertainty, but this increases blade weight and cost. In this paper, we present an improved blade design method to enhance the blade reliability of TCTs with relatively high efficiency for energy generation. An equivalent S−N curve model describing the relationship between axial load and cycle times and a simplified load spectrum including load caused by shear flow and turbulence are proposed for the first time for convenient lifetime estimation. A multi-objective genetic algorithm is used to optimize the chord length, twist angle, and thickness of the blade for the best match betwee... [more]

In the fight against climate change, the utilization of renewable energy resources is being encouraged in every country all over the world to lessen the emissions of greenhouse gases. However, not all countries are able to efficiently utilize these resources, and instead of providing solutions, the inefficient use of renewable energy may lead to even more damage to the environment. Data from eight countries belonging to the highly industrialized countries (HIC) group and nine from newly industrialized countries (NIC) group were used to evaluate the energy utilization of these groups. Factors such as total renewable energy capacity, the labor force, and total energy consumption were considered to be the input factors, while, CO2 emission and gross domestic product are the output factors. These factors were used to calculate efficiency scores of every country from 2013 to 2018 using the undesirable output model of Data envelopment analysis (DEA). The grey prediction model was also used t... [more]

An assessment of the wave power at the southern coast of the middle part of Java Island (Indonesia) was conducted based on a 15-year hindcast spectral wave model using the MIKE 21 Spectral Wave software. The model was forced with wind data with a 0.125° spatial interval and hourly time resolution. The obtained model was validated with field data collected from a buoy station that provided a set of significant wave height data with an hourly data interval for the whole month of June 2014. The validation showed that the obtained model matched the observed data with a minor average error. A spatial analysis was conducted in order to find the most suitable location for installing wave energy converters while taking into consideration the potential area demand, the wave power intensity, and the distance from the shore. Moreover, spatial analysis is conducted in order to find a suitable location to install wave energy converters, with consideration to potential area demand, wave power intens... [more]

One of the ways used to reduce the emission of carbon dioxide and other harmful substances is the implementation of biomass co-firing processes with coals. Such processes have been implemented for many years throughout many countries of the world, and have included using existing high-power coal boilers. Despite numerous experiments, there are still no analyses in the literature allowing for their generalization. The purpose of this paper is to determine the generalized energy and ecological characteristics of dust steam boilers co-firing hard coal with biomass. The energy characteristics determined in the paper are the dependence of the gross energy efficiency of boilers on such decision parameters as their efficiency and the share of biomass chemical energy in fuel. However, the ecological characteristics are the dependence of emission streams: CO, NO, SO2, and dust on the same decision parameters. From a mathematical point of view, the characteristics are approximation functions bet... [more]

In this study, the thermal stability and corrosivity of various CO2-loaded tertiary amine blends in both aqueous and non-aqueous form in stainless steel cylinders were studied for combined acid gas and water removal. The thermal stability was measured from the remaining amine concentration and the corrosivity was measured from the amount of various metals in blends using titration and inductively coupled plasma mass spectrometry (ICP-MS), respectively. The experimental data were used to calculate the rate constants of amine group loss. The developed model represented the experimental data very well. Solvent change from H2O to triethylene glycol (TEG) in blends decreased the thermal stability and vice versa for corrosivity. The amine stability was increased when contact with stainless steel was reduced. An increase in the amine concentration or CO2 loading at constant temperature decreased the thermal stability and vice versa for corrosivity.

The direct integration of Photovoltaic (PV) to the three-phase Modular Multilevel Converter (MMC) without dc−dc converters results in high-efficiency PV power plant with increased energy yield. The arm power control method for the MMC further improves the extraction of available power under uneven irradiance across different phases of the MMC. However, the uneven irradiance between the sub-modules results in residual voltage that results in harmonics and unbalance components. In this paper, the effect of uneven irradiance across the sub-module of the MMC is investigated with arm power control method. A modified balancing algorithm for the arm power control of the MMC is proposed which enables balanced power to be injected into ac grid despite uneven irradiance across the sub-modules in the MMC. The modified balancing algorithm enables to keep the unbalance in the phase currents below 10% and the Total Harmonic Distortion (THD) is confined as per IEEE 519 standard.

In recent years, the Oil & Gas industry has been subjected to a progressive electrification process aiming to comply with global environmental requirements on CO2 emissions reduction. High-power electric motors fed by Variable Frequency Drives (VFDs) have replaced gas turbines as drivers for gas compression applications. In Liquefied Natural Gas (LNG) plants, unexpected downturns could be experienced in case of high torsional vibrations of power generations units. These torsional vibrations derive from the interaction among turbine-generator (TG) units and VFDs and are known as Sub-Synchronous Torsional Interactions (SSTIs). SSTIs can lead to instability when the overall electromechanical system lacks sufficient damping. In this scenario, electrical damping assessment is fundamental in order to ensure stability and reliable operation of an LNG plant. Negative electrical damping is strictly related to the negative incremental resistance behavior of the power converters and it is influen... [more]

Floating offshore wind turbines (FOWTs) experience fluctuations in their platforms, owing to the various wave and wind conditions. These fluctuations not only decrease the output of the wind power generation system, but also increase the fatigue load of the structure and various equipment mounted on it. Therefore, when designing FOWTs, efficient performance with respect to waves and other external conditions must be ensured. In this study, a model test was performed with a 10 MW floating offshore wind turbine. The model test was performed by scaling down a 10 MW FOWT model that was designed with reference to a 5 MW wind turbine and a semisubmersible platform by the National Renewable Energy Laboratory and the DeepCwind project. A scale ratio of 1:90 was used for the model test. The depth of the East Sea was considered as 144 m and, to match the water depth with the geometric similarity of mooring lines, mooring tables were installed. The load cases used in the model test are combined e... [more]

China’s huge investment in the “belt and road initiative” (BRI) may have helped improve the economic level of participating countries, but it may also be accompanied by a substantial increase in greenhouse gas (GHG) emissions. The BRI corridors aim to bring regional stability and prosperity. In such efforts, energy efficiency due to increased transport has been overlooked in the recent literature. This paper employed a data envelopment analysis of the slack-based measurement (SBM) for bad output to assess the transport energy efficiency of 19 countries under the BRI economic corridors. By using the most cited transport-related input variables, such as vehicles, labor, motor oil, jet fuel, and natural gas, this study first analyzes the transport energy efficiency by first assuming the output variables individually and then takes two years as a pre- and post-BRI case by considering the aggregated output model. The results show an increase in economic activity but a decline in transport e... [more]

Price fluctuations in crude oil and natural gas, as important sources of energy, have a remarkable influence on our economies and daily lives. Therefore, it is extremely important to react appropriately and to formulate appropriate policies or strategies to reduce the expected negative effects of fluctuations. However, as Kilian suggested, not all oil price shocks are similar; price increases can have diverse impacts on the real price of oil, depending on the underlying determinants of the price fluctuation. Therefore, economists, policymakers, and investors need to decompose real price shocks and evaluate the responses of macroeconomic aggregates to different types of shocks. In this study, we investigate and compare the different effects crude oil and natural gas price shocks have on US real GDP and CPI levels, utilizing a two-stage method based on a structural vector autoregression (SVAR) model proposed by Kilian. We found that a crude oil specific demand shock made larger contribut... [more]

A fundamental thermodynamic analysis of an air-cooled fuel cell, where the reactant air stream is also the coolant stream, is presented. The adiabatic cell temperature of such a fuel cell is calculated in a similar way as the adiabatic flame temperature in a combustion process. Diagrams that show the dependency of the cathode outlet temperature, the stoichiometric flow ratio and the operating cell voltage are developed. These diagrams can help fuel cell manufacturers to identify a suitable blower and a suitable operating regime for their fuel cell stacks. It is found that for standard conditions, reasonable cell temperatures are obtained for cathode stoichiometric flow ratios of ξ = 50 and higher, which is in very good agreement with manufacturer’s recommendations. Under very cold ambient conditions, the suggested stoichiometric flow ratio is only in the range of ξ = 20 in order to obtain a useful fuel cell operating temperature. The outside relative humidity only plays a role at ambie... [more]

The Italian building stock consists of buildings mainly constructed until the mid-20th century using pre-industrial construction techniques. These buildings require energy refurbishment that takes into account the preservation of their architectural heritage. In this view, this work studies an innovative integrated modelling and simulation framework consisting of the implementation of Historical Building Information Modeling (HBIM) for the energy retrofit of historical buildings with renewable geothermal HVAC system. To this aim, the field case study is part of a medieval complex in Central Italy (Perugia), as representative ancient rural offshore architecture in the European countryside. The system involves of a ground source heat pump, a water tank for thermal-energy storage connected to a low-temperature radiant system, and an air-handling unit. The building heating energy performance, typically influenced by thermal inertia in historical buildings, when coupled to the novel HVAC sy... [more]

This paper presents the experimental development at demonstration scale of an integrated gasification system fed with wood chips. The unit is based on a fixed-bed, updraft and air-blown gasifier—with a nominal capacity of 5 MWth—equipped with a wet scrubber for syngas clean-up and an integrated chemical and physical wastewater management system. Gasification performance, syngas composition and temperature profile are presented for the optimal operating conditions and with reference to two kinds of biomass used as primary fuels, i.e., stone pine and eucalyptus from local forests (combined heat and power generation from this kind of fuel represents a good opportunity to exploit distributed generation systems that can be part of a new energy paradigm in the framework of the circular economy). The gasification unit is characterised by a high efficiency (about 79−80%) and an operation stability during each test. Particular attention has been paid to the optimisation of an integrated double... [more]

A nonlinear sliding-mode controller for a three-phase converter, utilized in plug-in electric vehicles (PEVs), is proposed in this paper. The proposed controller enables the utilized converter to perform multiple functions during different operating modes of the vehicle, i.e., grid-to-vehicle (G2V) and vehicle-to-grid (V2G) modes. The bidirectional three-phase converter and the proposed controller operate as a power factor correction circuit, bridgeless boost converter, and rectifier during G2V mode (i.e., plug-in charging), and it operates as a conventional single-stage inverter during V2G mode. The stability analysis of the proposed controller is performed by defining a proper Lyapunov function. The functionality of the proposed nonlinear controller is first evaluated through simulation studies. The feasibility and effectiveness of the proposed control strategy is then validated using an industrial control card through a hardware-in-the-loop (HIL) experimental testbed.

This study focuses on carbon capture and distribution technology, which is a new approach to the solution of this problem. In order to use this technology more effectively, six significant criteria are defined by considering the essentials of the international Loss Control Institute and the supported literature. Moreover, the analytic network process (ANP) is applied for measuring the relative importance of each factor. The findings demonstrate that organizational factor has the greatest importance, whereas market factor is the weakest element. In addition, the education of the personnel is the most important criterion for low-cost industrial carbon dioxide capture and separation technologies. In this context, it is seen that companies need competent personnel in order to reduce the costs of these products. There are two types of strategies that companies can develop to achieve this goal. Firstly, it would be appropriate for companies to provide their staff with the necessary training... [more]

The fixed-bed gasification of lignin-rich and -deficient mixtures was carried out to probe the synergistic effects between two model compounds, Lignin Pink (LP) rich in Na and Cellulose Microcrystalline (CM). Reaction conditions utilized the most commonly used air ratios in current wood gasifiers at 750 and 850 °C. It was found that by increasing the lignin content in the mixture, there was a selectivity change from solid to gas products, contrary to a similar study previously carried out for pyrolysis. This change in product mix was promoted by the catalytic effect of Na edge recession deposits on the surface of the char. As a result, the water gas shift reaction was enhanced at 850 °C for the LP48CM52 mixture across all air ratios. This was evidenced by a strong correlation between the produced H2 and COx. Meanwhile, by lowering the lignin content in the mixtures, the reactivity of cellulose microcrystalline was found to generate more char at higher temperatures, similar to lignin mi... [more]

In this study, low-quality rapeseed was used as a raw material for biodiesel fuel production. The application of such seeds with an enzyme catalyst is a green approach to producing renewable biodiesel fuel. During the in situ transesterification process, mineral diesel was selected as an extraction solvent for the simultaneous extraction and transesterification of rapeseed oil (RO). This allowed, at the end of the process, for the production of a mixture of mineral diesel and biodiesel fuel. Energy is saved using this process, as the need to extract the oil separately is eliminated and extraction and transesterification take place together in the in situ process. In this study, 11 different lipases were analyzed from which to select the most effective biocatalyst according to the chosen experimental conditions. The most suitable lipase for in situ transesterification was Lipozyme TL IM (Thermomyces lanuginosus). The impact of the temperature and duration of the reaction was investigate... [more]