Solar photovoltaic technology is one of the most well established new and renewable energy technologies. Many researchers have undertaken wide research and development in this sector, including material and system design. To protect the exhaustion of global terrestrial land and to avoid the occupation of extensive farmlands, solar photovoltaic (PV) developers, as well as policymakers, have pursued various solutions, including the development of floating solar PV (FPV). This study consists of a technological and economic perspective to analyze the floating solar PV system. The authors utilize remote sensing results to predict FPV efficiency and measure energy yield from the system while also developing an economics analysis on an FPV project by comparison with ground-based solar PV (GPV). The results from the remote sensing method found that the lake has a cooler temperature than the ground, with an annual difference of around 8 °C. FPV efficiency was also shown to be around 0.61% highe... [more]

This study examines the relationship between renewable and nuclear energy consumption, carbon dioxide emissions and economic growth by using the Granger causality and non-linear impulse response function in a business cycle in Spain. We estimate the threshold vector autoregression (TVAR) model on the basis of annual data from the period 1970−2018, which are disaggregated into quarterly data to obtain robust empirical results through avoiding a sample size problem. Our analysis reveals that economic growth and CO2 emissions are positively correlated during expansions but not during recessions. Moreover, we find that rising nuclear energy consumption leads to decreased CO2 emissions during expansions, while the impact of increasing renewable energy consumption on emissions is negative but insignificant. In addition, there is a positive feedback between nuclear energy consumption and economic growth, but unidirectional positive causality running from renewable energy consumption to econom... [more]

Simultaneous saccharification and fermentation (SSF) at high solid loading is a potential approach to improve the economic feasibility of cellulosic ethanol. In this study, SSF using high loading of rice straw was assessed using a vertical ball mill reactor. First, the conditions of temperature and number of glass spheres were optimized at 8% (w/v) initial solids (41.5 °C, 18 spheres). Then, assays were carried out at higher solid loadings (16% and 24% w/v). At 8% or 16% solids, the fermentation efficiency was similar (ηF~75%), but the ethanol volumetric productivity (QP) reduced from 1.50 to 1.14 g/L.h. By increasing the solids to 24%, the process was strongly affected (ηF = 40% and QP = 0.7 g/L.h). To overcome this drawback, three different feeding profiles of 24% pre-treated rice straw were investigated. Gradual feeding of the substrate (initial load of 16% with additions of 4% at 10 and 24 h) and an inoculum level of 3 g/L resulted in a high ethanol titer (52.3 g/L) with QP of 1.1... [more]

This Special Issue on “Selected papers from IEEE ICKII 2019” selected 13 excellent papers from 260 papers presented in IEEE ICKII 2019 on topics in energies. The fields include: energy fundamentals, energy sources and energy carriers, energy exploration, intermediate and final energy use, energy conversion systems, and energy research and development. The main goal of this Special Isue is to discover new scientific knowledge relevant to the topic of energies.

This research focuses on restoring signals caused by power failures in transmission lines using the basis pursuit, matching pursuit, and orthogonal matching pursuit sensing techniques. The original signal corresponds to the instantaneous current and voltage values of the electrical power system. The heuristic known as brute force is used to find the quasi-optimal number of atoms k in the original signal. Next, we search for the minimum number of samples known as m; this value is necessary to reconstruct the original signal from sparse and random samples. Once the values of k and m have been identified, the signal restoration is performed by sampling sparse and random data at other bus bars of the power electrical system. Basis pursuit allows recovering the original signal from 70% of the random samples of the same signal. The higher the number of samples, the longer the restoration times, approximately 12 s for recovering the entire signal. Matching pursuit allows recovering the same p... [more]

The transient temperature response is of great importance for evaluating the thermal capacity of ground heat exchangers (GHE). Based on the composition line source theory and superposition principle, we have developed a novel analytical model in Laplace space for calculating the temperature transient response. In comparison to the existing models, this proposed model can account for the fluid thermal storage effect and heat rate difference between the two legs of the single U-tube. With the aid of this proposed model, we conduct a thorough sensitivity analysis to investigate the effects of different influencing factors on the thermal transient response. The calculated results show that fluid thermal storage and the rate difference can significantly influence the thermal response during the early studied period. Therefore, the effect of fluid thermal storage should not be neglected when the early-time thermal response is investigated. The thermal interference between the two legs will r... [more]

The present article deals with two key drivers of social acceptance of wind energy: procedural justice and distributional justice. It is based on a comparative expert assessment carried out in the frame of the Horizon 2020 project WinWind covering six European countries. The focus of the paper is on procedural and financial participation of citizens and local stakeholders in wind energy projects. The first part covers institutional arrangements for public engagement in two areas of the decision-making process—wind turbine zoning/siting in spatial plans and authorization procedures. Here, three levels of public involvement—information, consultation and participation—were analyzed. The second part examines active and financial participation of citizens and local stakeholders. Here, we distinguish between two different modes of governance: institutionalized forms of public governance and voluntary forms of corporate governance. The outcomes suggest that concrete paths to the social accept... [more]

The energy-optimal routing of Electric Vehicles (EVs) in the context of parcel delivery is more complicated than for conventional Internal Combustion Engine (ICE) vehicles, in which the total travel distance is the most critical metric. The total energy consumption of EV delivery strongly depends on the order of delivery because of transported parcel weight changing over time, which directly affects the battery efficiency. Therefore, it is not suitable to find an optimal routing solution with traditional routing algorithms such as the Traveling Salesman Problem (TSP), which use a static quantity (e.g., distance) as a metric. In this paper, we explore appropriate metrics considering the varying transported parcel total weight and achieve a solution for the least-energy delivery problem using EVs. We implement an electric truck simulator based on EV powertrain model and nonlinear battery model. We evaluate different metrics to assess their quality on small size instances for which the op... [more]

Today, application of cavity receivers in solar concentrator systems is suggested as an interesting and novelty research subject for increasing thermal performance. In this research, a parabolic trough concentrator (PTC) with a rectangular cavity receiver was energetically investigated. The cavity receiver was studied with smooth and corrugated tubes. Different solar heat transfer fluids were considered, including water, air, and thermal oil. The effect of different operational parameters, as well as structural parameters, was investigated. The results showed that the linear rectangular cavity receiver with corrugated tube showed higher amounts of the absorbed heat and energy performance compared to the smooth tube as the cavity tube. Thermal performance of the rectangular cavity was improved using the application of water as the solar heat transfer fluid, which was followed by thermal oil and, finally, air, as the solar heat transfer fluid. Finally, it could be recommended that the re... [more]

We carried out a wind tunnel experiment to examine the power generation efficiency of a stand-alone miniature wind turbine and its wake characteristics at different tip speed ratios (TSRs) under the same mean inflow velocity. Resistors in the electrical circuit were adjusted to control the TSRs to 0.9, 1.5, 3.0, 4.1, 5.2, and 5.9. The currents were measured to estimate the turbine power outputs versus the TSRs and then establish the actual power generation coefficient Cp distribution. To calculate the mechanical power coefficient, a new estimation method of the mechanical torque constant is proposed. A reverse calibration on the blade rotation speed was performed with given electrical voltages and currents that are used to estimate the mechanical power coefficient Cp, mech. In the experiment, the maximum Cp,mech was approximately 0.358 (corresponding to the maximum Cp of 0.212) at the TSR of 4.1. Significant findings indicate that the turbine at the TSR of 5.2 produces a smaller torque... [more]

The simultaneous use of two passive methods (twisted tape and a nanofluid) in a heat transfer system will increase the average Nusselt number (Nu) of the system. However, the presence of inserts and nanoparticles inside the tube will create higher pressure drop (ΔP) in the system, which can eventually affect the overall enhancement ratio (η), especially at higher Reynolds numbers (Re). Several modifications of twisted tapes have been made to reduce ΔP, but most showed a decreasing trend of η as Re increased. The objective of this study is to design a new geometry of twisted tape that yields a larger value of Nu and a smaller value of ΔP, which can result in a larger value of η especially at higher Re. A simulation and experimental analysis are conducted in which Re ranges from 4000−16,000 with two types of nanofluids (SiC/Water and Al2O3/Water) at various values of the volume fraction, (φ) (1−3%). ANSYS FLUENT software with the RNG k-ɛ turbulent model is adopted for the simulation anal... [more]

This paper reports the performance of a spark ignition engine using gasoline blended with an upgraded bio-oil rich in aromatics and ethanol. This upgraded bio-oil was obtained using a two-step catalytic process. The first step comprised an in-situ catalytic pyrolysis process with CaO in order to obtain a more stable deoxygenated organic fraction, while the second consisted of a catalytic cracking of the vapours released using ZSM-5 zeolites to obtain an aromatics-rich fraction. To facilitate the mixture between bio-oil and gasoline, ethanol was added. The behaviour of a stationary spark ignition engine G12TFH (9600 W) was described in terms of fuel consumption and electrical efficiency. In addition, gaseous emissions and polycyclic aromatic hydrocarbon (PAH) concentrations were determined. Trial tests suggested that it is possible to work with a blend of gasoline, ethanol and bio-oil (90/8/2 vol%, herein named G90E8B2) showing similar fuel consumption than pure gasoline (G100) at the s... [more]

Models of technical systems are an essential means in design and product-development processes. A large share of technical systems, or at least subsystems, are directly or indirectly connected with the generation or transformation of energies. In design science, elaborated modelling approaches were developed for different levels of product concretization, for instance, requirement models and function models, which support innovation and new product-development processes, as well as for energy-generating or -transforming systems. However, on one product-concretization level, the abstract level that describes the physical behavior, research is less mature, and an overview of the approaches, their respective advantages, and the connection possibilities between them and other modelling forms is difficult to achieve. This paper proposes a novel discussion structure based on modelling perspectives and digital-engineering frameworks. In this structure, current approaches are described and ill... [more]

Ageing of technical systems and machines is a matter of fact. It therefore does not come as a surprise that an energy conversion system such as a wind turbine, which in particular operates under non-stationary conditions, is subjected to performance decline with age. The present study presents an analysis of the performance deterioration with age of a Vestas V52 wind turbine, installed in 2005 at the Dundalk Institute of Technology campus in Ireland. The wind turbine has operated from October 2005 to October 2018 with its original gearbox, that has subsequently been replaced in 2019. Therefore, a key point of the present study is that operation data spanning over thirteen years have been analysed for estimating how the performance degrades in time. To this end, one of the most innovative approaches for wind turbine performance control and monitoring has been employed: a multivariate Support Vector Regression with Gaussian Kernel, whose target is the power output of the wind turbine. On... [more]

Solid recovered fuel (SRF) residue, which is leftovers from the SRF manufacturing process, usually is discarded in landfill because of its low heating value and high ash and moisture content. However, it could be used as a fuel after mechanical and biological treatment. Gasification experiments were conducted on treated SRF residue (TSRFR) to assess the viability of syngas production. Efforts were also made to improve the gasification performance by adding low-cost natural minerals such as dolomite and lime as bed material, and by blending with biomass waste. In the case of additive mineral tests, dolomite showed better performance compared to lime, and in the case of biomass blends, a 25 wt% pine sawdust blend with TSRFR showed the best performance. Finally, as an appropriate condition, a combined experiment was conducted at an equivalence ratio (ER) of 0.2 using a 25 wt% pine sawdust blend with TSRFR as a feedstock and dolomite as the bed material. The highest dry gas yield (1.81 Nm3... [more]

The Mg-Li binary system is characterized by the presence of α-Mg(Li) and β-Li(Mg) phases, where magnesium exists in ordered and disordered forms that may affect the hydrogenation properties of magnesium. Therefore, the hydrogenation properties of an AZ31 alloy modified by the addition of 4.0 wt.%, 7.5 wt.% and 15.0 wt.% lithium were studied. The morphology (scanning electron microscopy (SEM)), structure, phase composition (X-ray diffraction (XRD)) and hydrogenation properties (differential scanning calorimetry (DSC)) of AZ31 with various lithium contents were investigated. It was found that the susceptibility of magnesium in the form of α-Mg(Li) to hydrogenation was higher than that for the magnesium occupying a disordered position in β-Li(Mg) solid solutions. Magnesium hydride was obtained as a result of hydrogenation of the AZ31 alloy that was modified with 4.0 wt.%, 7.5 wt.% and 15.0 wt.% additions of lithium, and was characterized by high hydrogen desorption activation energies of... [more]

This article describes a study that aimed to estimate the fuel-saving potential possessed by the hybridization of conventional powertrains intended for heavy-duty vehicles based on diesel and natural gas fueled engines. The tools used for this analysis constitute mathematical models of vehicle dynamics and the powertrain, including its components, i.e., the engine, electric drive, transmission, and energy storage system (ESS). The model of the latter, accompanied by experimental data, allowed for an analysis of employing a supercapacitor regarding the selection of its energy content and the interface between the traction electric drive and the ESS (in light of the wide voltage operating range of supercapacitors). The results revealed the influence of these factors on both the supercapacitor efficiency (during its operation within a powertrain) and the vehicle fuel economy. After implementation of the optimized ESS design within the experimentally validated vehicle model, simulations we... [more]

In the search for improvements in perovskite solar cells (PSCs), several different aspects are currently being addressed, including an increase in the stability and a reduction in the hysteresis. Both are mainly achieved by improving the cell structure, employing new materials or novel cell arrangements. We introduce a hysteresis-free low-temperature planar PSC, composed of a poly(3-hexylthiophene) (P3HT)/CuSCN bilayer as a hole transport layer (HTL) and a mixed cation perovskite absorber. Proper adjustment of the precursor concentration and thickness of the HTL led to a homogeneous and dense HTL on the perovskite layer. This strategy not only eliminated the hysteresis of the photocurrent, but also permitted power conversion efficiencies exceeding 15.3%. The P3HT/CuSCN bilayer strategy markedly improved the life span and stability of the non-encapsulated PSCs under atmospheric conditions and accelerated thermal stress. The device retained more than 80% of its initial efficiency after 1... [more]

When identifying and comparing forecasting models, there may be a risk that poorly selected criteria could lead to wrong conclusions. Thus, it is important to know how sensitive the results are to the selection of criteria. This contribution aims to study the sensitivity of the identification and comparison results to the choice of criteria. It compares typically applied criteria for tuning and performance assessment of load forecasting methods with estimated costs caused by the forecasting errors. The focus is on short-term forecasting of the loads of energy systems. The estimated costs comprise electricity market costs and network costs. We estimate the electricity market costs by assuming that the forecasting errors cause balancing errors and consequently balancing costs to the market actors. The forecasting errors cause network costs by overloading network components thus increasing losses and reducing the component lifetime or alternatively increase operational margins to avoid th... [more]

This paper presents the results of research related to the transformation of electrical energy into potential and kinetic energy of waves generated on the water surface. The waves are generated to model the environmental conditions for the needs of the model tests. The model tests are performed on model-scale objects to predict the features of full-scale maritime objects. It is done to improve human safety and the survivability of constructions. Electrical energy is transformed into the energy of the water waves using a wave maker. The wave maker considered is a facility with an electrohydraulic drive and an actuator submerged into the water. The actuator movement results in the waves being mechanically-generated in accordance with the wave maker theory. The study aimed to investigate the advantage of the newly implemented fuzzy-logic controller over the hitherto cascading proportional-integral controllers of the wave maker actuator. The research was focused on experimental investigati... [more]

Compared with conventional vehicles, hybrid electric vehicles (HEVs) have the advantage of high-energy conversion efficiency, which can have better fuel economy and lower emissions. The main issue of HEVs is how to develop an energy management strategy to achieve significantly better fuel efficiency. In this research, the Equivalent Consumption Minimization Strategy (ECMS) was applied to optimize the performance of fuel consumption in the Advanced Hybrid System-II (AHS-II). Based on FTP-75 Test Procedure defined by the U.S. Environmental Protection Agency (EPA), a backward simulation module was established. The baseline simulation module with the rule-based control strategy was validated with the original fuel consumption data. Then, the module with ECMS followed the same control rules of engine on/off and mode selection, and the fuel consumption of ECMS was compared with the simulation results of the baseline model. The fuel economy improvements of ECMS in urban, highway driving patte... [more]

Wind Diesel Power Systems (WDPS) are isolated microgrids which combine Wind Turbine Generators (WTGs) with Diesel Generators (DGs). The WDPS modelled in this article is composed of a DG, a WTG, consumer load, Dump Load (DL) and a Flywheel Energy Storage System (FESS). In the Wind-Diesel (WD) mode both the DG and WTG supply power to the consumers. The WDPS is simulated in the WD mode in the case that the WTG produced power exceeds the load consumption. This WTG excess power case is simulated in the subcases of DL and FESS turned off, only-DL and only-FESS. Simulations for the DL and FESS-off case show that the WTG excess power leads to a continuous system frequency increase, so that the tripping of the WTG Circuit Breaker (CB) is required to guarantee the WDPS power supply continuity. Simulations for the only-DL/only-FESS cases show that commanding the DL/FESS to consume controlled power, so that the required DG power to balance the system active power is positive, enables the DE speed... [more]

Today’s market leading electric vehicles, driven on typical UK motorways, have real-world range estimation inaccuracy of up to 27%, at around 10 °C outside temperature. The inaccuracy worsens for city driving or lower outside temperature. The reliability of range estimation largely depends on the accuracy of the battery’s underlying state estimators, e.g., state-of-charge and state-of-energy. This is affected by accuracy of the models embedded in the battery management system. The performance of these models fundamentally depends on experimentally obtained parameterisation and validation data. These experiments are mostly performed within thermal chambers, which maintain pre-set temperatures using forced air convection. Although these setups claim to maintain isothermal test conditions, they rarely do so. In this paper, we show that this is potentially the root-cause for deterioration of range estimation at low temperatures. This is because, while such setups produce results comparable... [more]

Two bimetallic Fe-Cu and Fe-Ca oxygen carriers were studied for chemical looping gasification (CLG) of biomass. The SEM results indicated that there was no obvious agglomeration on the bimetallic Fe-Cu oxygen carrier supported on Al2O3 and Fe-Ca oxygen carrier after five redox cycles while agglomeration occurred on CuO supported on Al2O3 due to the low melting point of CuO. The XRD results indicated the presence of copper-ferrite and calcium-ferrite phases in the bimetallic materials. The two bimetallic oxygen carriers can be re-oxidized with air to form a crystalline that is similar to the fresh materials. The Fe-Ca oxide became active at 360 °C which was lower than 380 °C for the Fe-Cu oxygen carrier. The high thermal stability and redox reactivity of bimetallic Fe-Cu and Fe-Ca oxygen carriers make the bimetallic oxygen carriers more suitable for recycling during CLG. The method for preparing Fe-Cu oxygen carriers had no significant impact on biomass conversion efficiency but had sig... [more]

Anaerobic digestion (AD) is a suitable management option for the energy valorization of many wastes, including the organic fraction of municipal solid waste (OFMSW). However, in some cases, long storage after the separate collection of this waste is required for management reasons, especially when the amount of waste to be treated temporarily exceeds the capacity of available AD plants. This study evaluates the biochemical methane potential (BMP) of the OFMSW after preliminary storage of 2, 6, and 10 days, in order to assess whether they are still suitable for AD or not. Moreover, the accuracy of three kinetic models (first order, Gompertz, and logistic models) in estimating the methane yield of stored OFMSW is tested. The resulting methane yield was between about 500 and 650 NmL·gVS−1 and slightly increased with the increase of the storage time after collection. Overall, this study has demonstrated that storage of OFMSW, when the collected amount of solid waste exceeds the treatment c... [more]