To establish a new quantitative analysis method for amorphous silica content and understand its effect on reservoir properties, the amorphous silica (SiO2) in the shale strata of the Lucaogou Formation in the Jimsar Depression was studied by scanning electron microscopy (SEM) observation, X-ray diffraction (XRD), and X-ray fluorescence spectrometry (XRF). Amorphous silica shows no specific morphology, sometimes exhibits the spherical or ellipsoid shapes, and usually disorderly mounds among other mineral grains. A new quantitative analysis method for observing amorphous SiO2 was established by combining XRD and XRF. On this basis, while the higher content of amorphous SiO2 lowers the porosity of the reservoir, the permeability shows no obvious changes. The higher the content of amorphous SiO2, the lower the compressive strength and Young’s modulus and the lower the oil saturation. Thus, amorphous SiO2 can reduce the physical properties of reservoir rocks and increase the reservoir plast... [more]

We present a novel mathematical model to investigate the extraction of wave power by flexible floaters. The model is based on the method of dry modes, coupled with a matched eigenfunction expansion. Our model results compare satisfactorily with preliminary data obtained from a demonstrator device, developed at the University of Groningen. We show that the role of elasticity is to increase the number of resonant frequencies with respect to a rigid body, which has a positive effect on wave power output. The mathematical model is then extended to irregular incident waves, described by a JONSWAP spectrum. Our results show that the peak capture factors decrease in irregular waves, as compared to the monochromatic case. However, the system becomes more efficient at non-resonant frequencies. This work highlights the need to scale-up experimental investigations on flexible wave energy converters, which are still a small minority, compared to those on rigid converters.

Drilling fluids are designed to be shear-thinning for limiting pressure losses when subjected to high bulk velocities and yet be sufficiently viscous to transport solid material under low bulk velocity conditions. They also form a gel when left at rest, to keep weighting materials and drill-cuttings in suspension. Because of this design, they also have a thixotropic behavior. As the shear history influences the shear properties of thixotropic fluids, the pressure losses experienced in a tube, after a change in diameter, are influenced over a much longer distance than just what would be expected from solely entrance effects. In this paper, we consider several rheological behaviors that are relevant for characterizing drilling fluids: Collins−Graves, Herschel−Bulkley, Robertson−Stiff, Heinz−Casson, Carreau and Quemada. We develop a generic solution for modelling the viscous pressure gradient in a circular pipe under the influence of thixotropic effects and we apply this model to configur... [more]

Energy-saving in regard to heating, ventilation, and air-conditioning (HVAC) in data centers is strongly required. Therefore, to improve the operating efficiency of the cooling equipment and extend the usage time of the economizer used for cooling information-technology equipment (ITE) in a data center, it is often the case that a high air-supply temperature within the range in which the ITE can be sufficiently cooled is selected. In the meantime, it is known that when the ambient temperature of the ITE rises, the speed of the built-in cooling fan increases. Acceleration of the built-in fan is thought to affect the cooling performance and energy consumption of the data center. Therefore, a method for predicting the temperature of a data center—which simply correlates supply-air temperature with ITE inlet temperature by utilizing existing indicators, such as air-segregation efficiency (ASE)—is proposed in this study. Moreover, a method for optimizing the total energy consumption of a da... [more]

Recently, the need for energy-saving and eco-friendly energy systems is increasing as problems such as rapid climate change and air pollution are getting more serious. While research on a power generation system using hydrogen energy-based fuel cells, which rarely generates harmful substances unlike fossil fuels, is being done, a power generation system that combines fuel cells and Organic Rankine Cycle (ORC) is being recognized. In the case of High Temperature Proton Exchange Membrane Fuel Cell (HT-PEMFC) with an operating temperature of approximately 150 to 200 °C, the importance of a thermal management system increases. It also produces the waste heat energy at a relatively high temperature, so it can be used as a heat source for ORC system. In order to achieve this outcome, waste heat must be used on a limited scale within a certain range of the temperature of the stack coolant. Therefore, it is necessary to utilize the waste heat of ORC system reflecting the stack thermal manageme... [more]

Decarbonization of power systems has put Renewable Energy Sources (RES) at the forefront when it comes to electric power generation. The increasing shares of converter-connected renewable generation cause a decrease of the rotational inertia of the Electric Power System (EPS), and consequently deteriorate the system capability to withstand large load-generation imbalances. Low-inertia systems are subjected to fast and large frequency changes in case of in-feed loss, where the traditional primary frequency control is not sufficient to preserve the frequency stability and to maintain the frequency above the critical value. One possible solution to this rising problem is seen in Fast Frequency Response (FFR) provided by the High-Voltage Direct-Current (HVDC)-based systems. This paper presents the adaptive FFR control of HVDC-based systems for frequency stability enhancement in the low-inertia system. The EPS is considered as a “black box” and the HVDC response is determined only using the... [more]

Power transformers are the main element of an electric power system. The service life of these devices depends to a large extent on the technical condition of their insulation system. Replacing mineral oils with natural or synthetic ester (retrofilling process) may increase the efficiency and operational safety of transformers, and also limit their adverse environmental impact. It is technically unfeasible to completely remove mineral oil from a transformer. Its small residues form a mixture with fluid ester, with different physicochemical and electric properties. Streaming electrification is one of the phenomena which, under unfavorable conditions, may damage the insulation system of a forced oil cooled transformer. It is necessary to run prophylactic tests for the ECT (electrostatic charging tendency) of insulating liquid mixtures from the point of view of transformer retrofilling, which is being used more often than before. The article presents the results of studies on selected phy... [more]

A fast and reliable vertical transportation system is an important component of modern office buildings. Optimization of elevator control strategies can be easily done using the state-of-the-art artificial intelligence (AI) algorithms. This study presents a novel method for optimal dispatching of conventional passenger elevators using the information obtained by surveillance cameras. It is assumed that a real-time video is processed by an image processing system that determines the number of passengers and items waiting for an elevator car in hallways and riding the lifts. It is supposed that these numbers are also associated with a given uncertainly probability. The efficiency of our novel elevator control algorithm is achieved not only by the probabilistic utilization of the number of people and/or items waiting but also from the demand to exhaustively serve a crowded floor, directing to it as many elevators as there are available and filling them up to the maximum allowed weight. Th... [more]

We present an alternative approach to estimating the spatial footprint of energy consumption, as this represents a major fraction of the ecological footprint (EF). Rather than depicting the current lack of sustainability that comes from estimating a footprint based on uptake of carbon emissions (the method used in EF accounting), our proposed “Renewable Energy Equivalent Footprint” (REEF) instead depicts a hypothetical world in which the electricity and fuel demands are met entirely from renewable energy. The analysis shows that current human energy demands could theoretically be met by renewable energy and remain within the biocapacity of one planet. However, with current technology there is no margin to leave any biocapacity for nature, leading to the investigation of two additional scenarios: (1) radical electrification of the energy supply, assuming 75% of final energy demand can be met with electricity, and (2) adopting technology in which electricity is used to convert atmospheri... [more]

Wake models play a fundamental role in finding optimized solutions in wind farm control. In fact, they allow assessing how wakes develop and interact with each other with the agility required for real-time applications. In this paper, a Gaussian Wake Model (GWM) is implemented in the OpenFAST framework in a way such that its fidelity is increased with respect to previously implemented models, while enhancing its compatibility with control purposes. The OpenFAST tool is coupled with Floris, NREL’s software based on the GWM, in order to simulate the wake effect on downstream machines (in the case where the downstream rotor is fully covered by the wake, only partially covered by the wake, of the wake is generated by the interaction of more than one turbine), while the rotor aerodynamics is calculated using the BEMT on the actual rotor flow field. We intend this work as a starting point for developing and testing open/closed-loop control logics that will work in real wind farms. To show th... [more]

Thermophotovoltaic (TPV) systems generate electricity without the limitations of radiation intermittency, which is the case in solar photovoltaic systems. As energy demands steadily increase, there is a need to improve the conversion dynamics of TPV systems. Consequently, this study proposes a novel radiation-thermodynamic model to gain insights into the thermodynamics of TPV systems. After validating the model, parametric studies were performed to study the dependence of power generation attributes on the radiator and PV cell temperatures. Our results indicated that a silicon-based photovoltaic (PV) module could produce a power density output, thermal losses, and maximum voltage of 115.68 W cm−2, 18.14 W cm−2, and 36 V, respectively, at a radiator and PV cell temperature of 1800 K and 300 K. Power density output increased when the radiator temperature increased; however, the open circuit voltage degraded when the temperature of the TPV cells increased. Overall, for an 80 W PV module,... [more]

Seismically isolated nuclear power plants (NPPs) can provide substantial benefits towards reducing the failure probability of NPPs, especially for beyond design basis earthquake shaking. One risk posed by seismic isolation is the potential for pounding to a stop or moat wall, with currently little guidance provided by design standards on how to address this concern. In this paper, a structural model of an isolated NPP based on the Advanced Power Reactor 1400 MW is enveloped with moat walls and advanced bearing models. The bearing models account for large strain behavior through failure based on full-scale experiments with lead rubber bearings (LRBs). Using these analytical models and a measured ultimate property diagram from LRB failure tests, the range of clearance to the stop considering the performance criteria for the NPP is investigated. Although the analysis results are dependent on the particular models, ground motions, and criteria employed, this research provides an overview o... [more]

Removing heat from high-density information technology (IT) equipment is essential for data centers. Maintaining the proper operating environment for IT equipment can be expensive. Rising energy cost and energy consumption has prompted data centers to consider hot aisle and cold aisle containment strategies, which can improve the energy efficiency and maintain the recommended level of inlet air temperature to IT equipment. It can also resolve hot spots in traditional uncontained data centers to some degree. This study analyzes the IT environment of the hot aisle containment (HAC) system, which has been considered an essential solution for high-density data centers. The thermal performance was analyzed for an IT server room with HAC in a reference data center. Computational fluid dynamics analysis was conducted to compare the operating performances of the cooling air distribution systems applied to the raised and hard floors and to examine the difference in the IT environment between th... [more]

In the parking lots of public commercial areas, such as shopping malls, hospitals, and scenic spots, the parking spaces with electric vehicle (EV) charging facilities are often occupied by ordinary cars. How to regulate the parking order in the parking lot is a key issue in the operation and management of the parking facilities. In this paper, a method of assessing parking fees for vehicles parked at the charging facilities is proposed based on an economic penalty strategy, including fixed-penalty and dynamic-penalty strategies. First, a traffic flow model of the parking lot in public area is established. Then, a price and consumption model of parking fees and parking lot utilization is established, along with different penalty strategies. Finally, taking the parking lot of a shopping mall as an example, the penalty strategies are optimized through particle swarm optimization (PSO) algorithm. The simulation results show that the method proposed can help to improve the utilization of EV... [more]

Bio-based supply chains are by nature complex to optimize. The new logistic concept of integrated biomass logistical center (IBLC) provides us the opportunity to make full use of the idle capacity for a food/feed plant to produce biobased products so that the entire chain efficiency can be improved. Although research has been conducted to analyze the IBLC concept, is yet to be an optimization model that can optimally arrange the activities in the supply chain where an IBLC stands in the middle. To fill the knowledge gap in the literature, this paper makes the first step to develop a MILP model that enables biobased supply chain optimization with the IBLC concept, which supports logistic and processing decisions in the chain. The model is applied in a case study for a feed and fodder plant in Spain where managerial insights have been derived for transferring the plant to a profitable IBLC.

The paper presents a new approach to predicting the 24-h electricity power demand in the Polish Power System (PPS, or Krajowy System Elektroenergetyczny—KSE) using the deep learning approach. The prediction system uses a deep multilayer autoencoder to generate diagnostic features and an ensemble of two neural networks: multilayer perceptron and radial basis function network and support vector machine in regression model, for final 24-h forecast one-week advance. The period of the data that is the subject of the experiments is 2014−2019, which has been divided into two parts: Learning data (2014−2018), and test data (2019). The numerical experiments have shown the advantage of deep learning over classical approaches of neural networks for the problem of power demand prediction.

In this study, several purge and ventilation methods are proposed to reduce and remove condensation in a heat recovery ventilator for commercial and household buildings. The effects of the airflow rate, duration of ventilation, purge interval, and return air temperature on the quantities of condensation and condensation removal in the heat recovery ventilator are analyzed. The increase in the air flow rate and return air temperature increases the condensation removal rate owing to the enhanced evaporation of the condensate. Furthermore, the reductions in the duration of ventilation and purge interval decreased the accumulation of condensate on the heat exchanger element. Based on the experimental results, optimum ventilation and purge strategies are proposed according to the outdoor temperature. The operation of the heat recovery ventilator with the proposed ventilation and purge strategies shows at least a 33% and up to an 80% reduction in the quantity of condensate compared with a gi... [more]

Korea Atomic Energy Research Institute (KAERI) established a multi-dimensional hydrogen analysis system to evaluate hydrogen release, distribution, and combustion in the containment of a Nuclear Power Plant (NPP), using MAAP, GASFLOW, and COM3D. In particular, KAERI developed an analysis methodology for a hydrogen flame acceleration, on the basis of the COM3D validation results against measured data of the hydrogen combustion tests in the ENACCEF and THAI facilities. The proposed analysis methodology accurately predicted the peak overpressure with an error range of approximately ±10%, using the Kawanabe model used for a turbulent flame speed in the COM3D. KAERI performed a hydrogen flame acceleration analysis using the multi-dimensional hydrogen analysis system for a severe accident initiated by a station blackout (SBO), under the assumption of 100% metal−water reaction in the Reactor Pressure Vessel (RPV), to evaluate an overpressure buildup in the containment of the Advanced Power Re... [more]

The space scientific payload rack is a multifunctional experimental platform, and the requirements of the environmental temperature index are different for diversified experimental modules inside. The air cooling system is an important part of the rack thermal control system. A new type of air cooling system with small size and flexible arrangement is proposed in this paper, that is, micro air ducts with pinhole-sized air vents. The rack physical models of new and traditional air cooling modes are established, respectively. The numerical simulation of the inner air flow is carried out by Ansys Fluent CFD software (Ansys Inc., Canonsburg, PA, USA), which verifies that compared with the traditional method, the temperature field and flow field of the new air cooling method are more uniform, and the heat sources located at the edge of the rack can also be cooled better.

Helium is the second most abundant element in the Universe after hydrogen. Considerable resources of helium-3 isotope (He3) are located mostly outside the Earth. He3 is very important for science and industry, especially for airport neutron detectors, lung tomography and helium dilution refrigerators. Besides, global warming is forcing the industry and governments to search for alternative energy sources, and He3 has the potential to be used as fuel in future nuclear fusion power plants. Unfortunately, the price of gaseous He3 has recently increased from $200 per liter to over $2750. The expected further increase in price and demands led us to present an analysis of the economic profitability for He3 separation process, which utilizes the properties of superfluid helium. This paper shows the arguments supporting the idea that extraction from natural sources is the only economically viable way of obtaining He3 isotope nowadays. The method could be relatively easily implemented into the... [more]

The present paper deals with the Life-Cycle Cost (LCC) of an offshore renewable energy farm that is currently a topic of interest for operators and investors. The LCC analysis refers to the Cost Breakdown Structure (CBS) considering all the phases of life span, and it has been carried out for floating offshore wind farms (FOWFs) and hybrid wind-wave farms (HWWFs). For HWWFs, this paper proposes a hybrid wind-wave energy system (HWWES), which provides the coupling of wave energy converter (WEC) with Tension Leg Platform (TLP) or Spar Buoy platform (SB). The LCC analysis has been carried out considering: (i) FOWF consisting of TLP floating platforms; (ii) FOWF consisting of a SB floating platforms; (iii) HWWF realized with the conceived hybrid system coupling the WEC with the TLP platform; (iv) HWWF realized with the conceived hybrid system coupling the WEC with SB platform. In addition to the LCC evaluation, the Levelized Cost of Energy (LCOE) analysis has also been carried out. The sit... [more]

In developing countries, electrification in remote areas, where access to energy is limited or null, has been one of the biggest challenges in recent years. Isolated microgrids with renewable generation are an efficient alternative for the energy supply in these areas. The objective of this work was to analyse the techno-economic viability of 6 isolated microgrids in different locations in the non-interconnected zone of Colombia, considering different climatic conditions, the availability of renewable resources, the current consumption profile, and a modified profile applying demand-side management. Modelling and simulation were performed considering storage systems based on lithium and lead-acid batteries. The resulting simulations provide the optimal system cost, emissions levels, electricity cost and battery lifetime. This study demonstrates that isolated hybrid microgrids with renewable energy are a feasible alternative to solve access to energy problems, reducing the need for dies... [more]

Through applying an exemplary design study, the dependencies between current density, temperatures, and weight in an electrical drive system for a small range aircraft with conventional electrical fan or propeller drives are evaluated. This study applies a combined numerical (Finite Element Method FEM) and analytical approach to the machine design, calculation of temperatures, and cooling system design (cooler, pumps, piping). A design scenario was defined using start and climb flight in a warm tropical surrounding as the worst load case. The design has to move between two fixed temperature limits: The maximum allowable temperature in the machine insulation and the ambient temperature. The implemented method facilitates a comparatively fast-medium depth design of the drive system. The derived results show, in fact, a minimum of weight at a certain current density, which is one of the key interests for the designers of the electrical machine. The main influences on this minimum are the... [more]

Pore structure has been widely observed to affect the seismic wave velocity of rocks. Although taking lab measurements on 1.0-inch core plugs is popular, it is not representative of the fractured-vuggy carbonates because many fractures and vugs are on a scale up to several hundred microns (and greater) and are spatially heterogeneous. To overcome this shortage, we carried out the lab measurements on full-diameter cores (about 6.5−7.5 cm in diameter). The micro-CT (micro computed tomography) scanning technique is used to characterize the pore space of the carbonates and image processing methods are applied to filter the noise and enhance the responses of the fractures so that the constructed pore spaces are reliable. The wave velocities of P- and S-waves are determined then and the effects of the pore structure on the velocity are analyzed. The results show that the proposed image processing method is effective in constructing and quantitatively characterizing the pore space of the full... [more]

An important aspect of the off-grid utilization of hybrid generation systems is the integration of energy storage facilities into their structures, which allows for improved power supply reliability. However, this results in a significant increase in the cost of such systems. Therefore, it is justified to use optimization resulting in the minimization of the selected economic indicator taking into account the most important technical constraints. For this reason, this work proposes an algorithm to optimize the structure of a hybrid off-grid power distribution system (with electrochemical energy storage), designed to supply a load with known daily energy demand. The authors recommend genetic algorithm utilization as well as a modified criterion for evaluating the quality of solutions based on the Levelized Cost of Energy (LCOE) index. Several technical and economic analyses were presented, including unit costs, power distribution of the wind and solar sections, nominal battery capacity,... [more]