Energy Production Rate Research Articles

Driven and undriven states of multicomponent granular gases of inelastic and rough hard disks or spheres

Starting from a recent derivation of the energy production rates in terms of the number of translational and rotational degrees of freedom, a comparative study on different granular temperatures in gas mixtures of inelastic and rough disks or spheres is carried out. Both the homogeneous freely cooling state and the state driven by a stochastic thermostat are considered. It is found that the relaxation number of collisions per particle is generally smaller for disks than for spheres, the mean angular velocity relaxing more rapidly than the temperature ratios. In the asymptotic regime of the undriven system, the rotational-translational nonequipartition is stronger in disks than in spheres, while it is hardly dependent on the class of particles in the driven system. On the other hand, the degree of component-component nonequipartition is higher for spheres than for disks, both for driven and undriven systems. A study of the mimicry effect (whereby a multicomponent gas mimics the rotational-translational temperature ratio of a monocomponent gas) is also undertaken.

Parametrical study and turbulence analysis of high-speed flows around an open cavity using large eddy simulation

Large eddy simulation is used in this work to simulate the three-dimensional turbulent flow in an open cavity, with special attention paid to the parametrical effect and turbulence analysis. The effect of mesh resolution, the sub-grid model and the advection scheme on the resolved flow structure is discussed in detail. Then, the mechanism of flow-induced pressure fluctuation associated with the primary and secondary vortex in the shear layer is clarified quantitatively and qualitatively. Finally, the turbulent kinetic energy and turbulence production rate, the contribution of three components to total turbulence production rate and the main single contributor are analyzed systematically. The present simulations are performed for two Reynolds numbers and the results show that the flow is more turbulent with the increase in Reynolds number, but the general flow morphology is almost the same. It is expected that the basic founding is useful for understanding such similar flows and will provide some guidelines for controlling the vortex-induced flow instability in engineering applications.

A Comparative Analysis of Sunshine Duration Effects in terms of Renewable Energy Production Rates on The LEED BD + C Projects in Turkey

Global warming has been on the agenda over the past few years. Solutions to global warming and energy efficiency problems have brought with them the need for green building market. Leadership in Energy and Environmental Design (LEED) is a certification system regulating the compliance of green buildings to certain standards and is essential for construction projects focusing on sustainability and innovation. This study investigates the effects of sunshine duration on construction projects reducing annual electricity consumption and increasing renewable energy production. In this study, the effects of sunshine duration times on construction projects are located in different cities in Turkey which has gained point from LEED BD+C (NC) (LEED, Building Design + Construction: New Construction) certificate were analyzed with the help of getting the impact of annual electricity consumption and renewable energy production rates. It was our aim that the results will be used for construction projects in compliance with the “Energy and Atmosphere” category of the LEED BD+C certification system.

A novel radial jet drilling stimulation technique for enhancing heat recovery from fractured geothermal reservoirs

In this study, the application of the Radial Jet Drilling (RJD), a novel stimulating technique for enhancing productivity in the existing wells in deformable naturally fractured reservoirs was investigated using a robust three-dimensional finite element DFM (discrete fracture-matrix) model. Results showed that the RJD laterals were more effective in enhancing injectivity/productivity in cases with lower fracture density, i.e. lower equivalent permeability, while they had no significant effect on the heat production in these cases. In higher fracture density cases, the RJD laterals improved the heat production while had no significant effect on the injectivity/productivity. Results also showed that in reservoirs with very low permeability matrix, the RJD laterals can be used to connect the wells to the fracture network and hence enhance the well performance. The sensitivity analysis on the average net energy production rate with respect to the length of the RJD laterals showed that in the situations where the wells were not connected directly to the fractures, the length of RJD laterals played a crucial role in enhancing the average net energy rate. However, the 100 m laterals almost removed the dependency of the average net energy production rate on the well placement for low, medium and high fracture density cases.

Energy and entropy preserving numerical approximations of thermodynamically consistent crystal growth models

We present a numerical scheme that preserves the total energy and the entropy production rate, termed the energy and entropy production rate preserving scheme, for a general class of thermodynamically consistent phase field models for dendritic crystal growth derived from the first and second law of thermodynamics. The scheme is second order in time, linear and energy and entropy production rate preserving for any time steps. The scheme is first discretized in time aided by the energy quadratization (EQ) method and then in space using compact finite difference methods. The linear system resulting from the scheme is shown to be uniquely solvable at both the semi-discrete and the fully discrete level. Mesh refinement tests are performed to show the second-order time convergence rate in the scheme. Several numerical examples of dendritic crystal growth are provided to demonstrate the accuracy and efficiency of the scheme. The effects of various model parameters on growth patterns of the crystal are further investigated in details with the numerical solver. The approach to developing the energy and entropy production rate-preserving numerical scheme proposed in this study is so general that it can be applied to a wide range of thermodynamically consistent models not limited to phase field models.

Measurement of Respiration Rate in Live Caenorhabditis elegans

Mitochondrial function and dysfunction are at the core of aging and involved in many age-dependent diseases. Rate of oxygen consumption is a measure of mitochondrial function and energy production rate. The nematode Caenorhabditis elegans (C. elegans) offers an opportunity to study "living" mitochondria without the need for mitochondrial extraction, purification and associated artifacts. Oxygen consumption rate (OCR) is traditionally measured using single-chamber Clark electrodes with or without the addition of metabolic modulators. More recently, multi-well oxygen electrodes with automated injection system have been developed to enable rapid measurement of OCR under different conditions. Here, we describe a detailed protocol that we have adapted from existing protocols to measure coupled and uncoupled mitochondrial respiration (with and without metabolic modulators) in live respiring nematodes using a Seahorse XFe96 extracellular flux analyzer. We present details on our protocol, including preparation of nematode culture, use of metabolic modulators, execution of Seahorse XF assay as well as post-experimental data analysis. As a reference, we provide results of a series of experiments in which the metabolic activity of N2 wild-type nematodes was compared to N2 nematode treated with paraquat, a compound that generates reactive oxygen species (ROS), thus causing oxidative damage and mitochondrial dysfunction. These data illustrate the kind of insights that can be obtained even using a low number of nematodes (10 animals only per well).

Multi-objective optimization for energy efficient machining with high productivity and quality for a turning process

The global competition and rising concerns over the environmental issues have forced the manufacturing industry to balance the energy consumption, production rate and product quality. This requires the power consumption to be reduced and the production rate to be maximized in accordance with the required quality of the product. The required quality, dictated by the surface finish, is based on the customer preferences, the functional requirements of the product and the product itself. In machining context, these quantities mainly depend upon the choice of process parameters. This study is an attempt to obtain a suitable combination of the turning parameters to optimize material removal rate (MRR) and power for different targeted values of surface roughness. The predictive model has been developed using response surface methodology (RSM). Model fitness and adequacy have been confirmed with analysis of variance (ANOVA).

Effect of Flap on the Wind Turbine-Concentrator Combination

Wind energy is a renewable energy resource that can be used to ensure energy sustainability without causing environmental pollution. In this content, many studies are going on to acquire more energy from the wind. One of the methods to increase the energy production rate of the wind turbine is increase the mass flow rate which moves through the turbine working section. This can be achieved by equipping the turbine with a concentrator. The purpose of this study is to optimize the concentrator with flap geometry leading maximum flow speed increase at the turbine zone and compare it single airfoil shape concentrator. The actuator porous disc model is used to represent wind turbine in the concentrator. Response Surface Method is used as optimization methods with 2D CFD analyses. Concentrator with flap increases the flow speed by a factor 1.2 while single airfoil section increases by a factor 1.1.

A novel pricing scheme for managing virtual energy communities and promoting behavioral change towards energy efficiency

The harmonization between the variable rate of energy production in the era of massive renewable energy penetration is a major challenge in an open, competitive and resilient electricity market. As a result, there is an increasing need for modern pricing schemes, which will effectively incentivize willing users to modify their energy consumption pattern to meet this objective. Current energy pricing schemes (e.g. real time pricing) treat all users the same, and do not adequately compensate for behavioral changes, thus mitigating the behavioral change dynamics. In this paper, we propose a Community Real Time Pricing (CRTP) scheme together with an Energy Community Formation Algorithm (ECFA), where users are clustered in Virtual Energy Communities (VECs) according to: (i) their level of flexibility in modifying their Energy Consumption Curve (ECC), and (ii) their relationships in Online Social Networks (OSNs), modelling peer-pressure capabilities. We show that CRTP with ECFA can simultaneously achieve considerable reduction in the system’s energy cost and greater aggregated users’ welfare than with the state-of-the-art real time pricing. CRTP–ECFA adopts a truly fair pricing policy, as each user is rewarded exactly according to his/her individual contribution in reducing system costs, thus promoting the desired behavioral change.

On Destruction of a Thermally Stable Layer by Compositional Convection in the Earth's Outer Core

We discuss destruction of a thermally stable layer in the upper part of the Earth's outer core by compositional convection excited at the inner core boundary. We propose to use the radial distribution of power induced by thermal and compositional buoyancy (rate of kinetic energy production) as a measure of occurrence of thermal and compositional convection. The power consists of the terms proportional to convective entropy flux and convective compositional flux. In the region with positive power, convection is active because kinetic energy can be produced by buoyancy force, and a stably stratified layer could not be formed there. On the other hand, in the region with negative power, convection is suppressed and a stably stratified layer may be produced. Considering penetration effect of convection, we discuss possible maximum and minimum thicknesses of the stable layer based on the radial distribution of power and its radial integral, respectively. We construct a 1-dimensional thermal and compositional balance model of the Earth's core with a larger value of thermal conductivity recently suggested by high-pressure experiments and first principle calculations, and estimate radial distributions of power for various values of core mantle boundary (CMB) heat flux Q_CMB. When Q_CMB > Q_sCMB no thermally stable layer can exist, where Q_sCMB is conductive heat flux along the adiabat at CMB. On the other hand, when Q_CMB < Q_sCMB, formation of an upper thermally stable layer becomes possible, depending on the extent of penetration of compositional convection excited below. When Q_CMB is sufficiently lower than Q_sCMB, a thermally stable layer survives the maximum penetration of compositional convection. The results show that a thermally stable layer becomes effectively thinner when the effect of compositional convection is considered compared with the results of previous studies where the existence of a stable layer is evaluated based on the convective flux only.

Mineralocorticoid antagonism enhances brown adipose tissue function in humans: A randomized placebo-controlled cross-over study.

To investigate whether mineralocorticoid (MC) antagonism enhances brown adipose tissue (BAT) function in humans. In a randomized double-blind, cross-over designed trial, 10 healthy adults (two men, eight women) underwent 2 weeks of spironolactone (100 mg/d) treatment and placebo, with an intervening 2-week wash-out period. BAT function was assessed in response to cooling and to a mixed meal. Metabolic activity was measured by fluoro-deoxyglucose (FDG) uptake (maximal standardized uptake value, SUVmax ) using PET-CT. Thermogenic activity was measured by skin temperatures overlying supraclavicular (SCL) BAT depots using infrared thermography. Postprandial metabolism was measured by energy production rate (EPR) and lipid synthesis using indirect calorimetry. During cooling, BAT metabolic activity (SUV 6.30 ± 2.16 vs 3.98 ± 1.34; P < 0.05) and volume (54.9 ± 22.8 vs 21.6 ± 11.8 cm3 ; P < 0.05) were significantly higher, and mean SCL temperature decreased by a smaller degree (-0.3°C°± 0.2°C vs -0.9°C ± 0.2°C; P = 0.05) with spironolactone treatment. A mixed meal increased SCL temperature and EPR. The postprandial rise in SCL temperature (+0.4°C ± 0.1°C vs +0.1°C ± 0.1°C; P < 0.05) but not in EPR was greater during spironolactone treatment. Postprandial lipid synthesis occurred in three participants with placebo but in none with spironolactone treatment (P = 0.06). MC antagonism enhanced human BAT function in response to cooling and to a meal during which lipid synthesis was suppressed. As postprandial EPR comprises energy dissipated as heat and energy required to store nutrients, the reduction in lipid synthesis during MC antagonism is a probable consequence of concurrent stimulation of BAT thermogenesis. The shift in energy usage from storage to heat dissipation indicates that MC antagonists may have therapeutic benefit for obesity.

Characteristics of energy production and dissipation around a bubble rising in water

A numerical simulation on the rise behaviour of a bubble rising in stagnant water at Re ≈ 800–1300 has been conducted. It is found that vorticity generated at the side of the bubble is transferred to the wake region, forming chains of hairpin vortices that are regularly shed and transported downstream. The resulting fluctuations in shape, trajectory, and rise velocity were found to conform well to experimental observations. The fluctuations in velocity resulting from the unsteady wakes were analysed through a fixed-frame approach about the centre of mass of the bubble. The average turbulent kinetic energy in the near wake region was found to be ≈1.4–4.8% with respect to the average kinetic energy of the bubble. The production of the turbulent kinetic energy was found to occur predominantly at the near wake region of the bubble, mostly as a result of normal and tangential gradients of the mean streamwise velocity. Interestingly, several regions of negative rate of energy production were identified, namely at the top and side interfaces of the bubble. Overall, the ratio of positive-to-negative production rate was found to be ≈2.4–3.1, resulting in a net conversion towards smaller-scale fluctuations from the mean flow. Small–scale dissipation was found to occur throughout the wake of the bubble.

Energy balance of reduced order models for unsteady flows using sparse coding

Galerkin projection is a commonly used reduced order modeling approach; however, stability and accuracy of the resulting models are open issues for unsteady flow fields. Balance between production and dissipation of energy is crucial for stability. Moreover, the rates of energy production and dissipation are functions of large- and small-scale information captured in the chosen modes. Due to the highly nonlinear nature of the Navier–Stokes equations, the process of choosing an ‘appropriate’ set of modes from the simulation or experimental data is non-trivial. Recent work indicates that modal decompositions computed using a sparse coding approach yield multi-scale modes that provide improved low-order models compared to the commonly used proper orthogonal decomposition. This study seeks to use energy components analysis to develop a deeper understanding of the improved model performance with sparse modes. In addition, a greedy search-based sparse coding algorithm is developed for basis extraction. The analysis is performed on two canonical problems of incompressible flows inside a lid-driven cavity and past a stationary cylinder. Results indicate that there is a direct link between the presence of multi-scale features in the reduced set of modes, balance between production and dissipation of energy, and reduced order model performance.

Powering up: Financing and Policy for the Worldwide Transition to Renewable Energy

The worldwide transition to renewable energy innovation and production, while promising, has been slow and uneven. An important reason is the lack of adequate financing for renewables. This paper examines how different nations’ financial markets and renewable energy policies contribute to the rates of renewable energy production and innovation. We theorize and demonstrate, using a sample of 73 countries from 1991 to 2013, the positive influence of credit market development on the transition to renewable energy production and innovation, and the complementary function of regulatory policies and credit market development on such transition. As such, we contribute to the sustainability literatures on financing renewable energies, regulatory versus market policy effects, and cross-national green development.

Interplay between polydispersity, inelasticity, and roughness in the freely cooling regime of hard-disk granular gases.

A polydisperse granular gas made of inelastic and rough hard disks is considered. Focus is laid on the kinetic-theory derivation of the partial energy production rates and the total cooling rate as functions of the partial densities and temperatures (both translational and rotational) and of the parameters of the mixture (masses, diameters, moments of inertia, and mutual coefficients of normal and tangential restitution). The results are applied to the homogeneous cooling state of the system and the associated nonequipartition of energy among the different components and degrees of freedom. It is found that disks typically present a stronger rotational-translational nonequipartition but a weaker component-component nonequipartition than spheres. A noteworthy "mimicry" effect is unveiled, according to which a polydisperse gas of disks having common values of the coefficient of restitution and of the reduced moment of inertia can be made indistinguishable from a monodisperse gas in what concerns the degree of rotational-translational energy nonequipartition. This effect requires the mass of a disk of component i to be approximately proportional to 2σ_{i}+〈σ〉, where σ_{i} is the diameter of the disk and 〈σ〉 is the mean diameter.

Fermentative biohydrogen production from tequila vinasse via the lactate-acetate pathway: Operational performance, kinetic analysis and microbial ecology

In this study, a comprehensive approach considering the operational performance, kinetic analysis and microbial ecology was employed to investigate the fermentative biohydrogen (bioH2) production from tequila vinasse. Batch fermentations were conducted in a 3-L stirred tank reactor at 35 °C and pH 6.5–5.8. The bioH2 yield of 124 ± 9 NmL/g VSadded and a peak bioH2 production rate of 159 ± 33 NmL/L-h were obtained. Thus, the energy yield and energy production rate were estimated as 1.5 kJ/g VSadded and 48.7 ± 10.2 kJ/L-d, respectively. The metabolic profile and correlation analysis reflected that bioH2 was associated with the consumption of lactate and acetate. The lactate-acetate pathway was consistent with the modeling of substrate consumption, product formation and biomass growth accurately described by the modified Gompertz model. Illumina MiSeq high-throughput sequencing revealed that Clostridium beijerinckii, Streptococcus sp. and Acetobacter lovaniensis were the main species at the highest bioH2 production activity. The results obtained suggested that the lactate-acetate pathway can potentially be used to produce bioH2 from tequila vinasse.

Cold adaptation does not alter ATP homeostasis during cold exposure in Drosophila melanogaster.

In insects and other ectotherms, cold temperatures cause a coma resulting from loss of neuromuscular function, during which ionic and metabolic homeostasis are progressively lost. Cold adaptation improves homeostasis during cold exposure, but the ultimate targets of selection are still an open question. Cold acclimation and adaptation remodels mitochondrial metabolism in insects, suggesting that aerobic energy production during cold exposure could be a target of selection. Here, we test the hypothesis that cold adaptation improves the ability to maintain rates of aerobic energy production during cold exposure by using 31 P NMR on live flies. Using lines of Drosophila melanogaster artificially selected for fast and slow recovery from a cold coma, we show that cold exposure does not lower ATP levels and that cold adaptation does not alter aerobic ATP production during cold exposure. Cold-hardy and cold-susceptible lines both experienced a brief transition to anaerobic metabolism during cooling, but this was rapidly reversed during cold exposure, suggesting that oxidative phosphorylation was sufficient to meet energy demands below the critical thermal minimum, even in cold-susceptible flies. We thus reject the hypothesis that performance under mild low temperatures is set by aerobic ATP supply limitations in D. melanogaster, excluding oxygen and capacity limitation as a weak link in energy supply. This work suggests that the modulations to mitochondrial metabolism resulting from cold acclimation or adaptation may arise from selection on a biosynthetic product(s) of those pathways rather than selection on ATP supply during cold exposure.

Three-Stage Anaerobic Sequencing Batch Reactor (ASBR) for Maximum Methane Production: Effects of COD Loading Rate and Reactor Volumetric Ratio

A three-stage anaerobic sequencing batch reactor system was developed as a new anaerobic process with an emphasis on methane production from ethanol wastewater. The three-stage anaerobic sequencing batch reactor system consisted of three bioreactors connected in series. It was operated at 37 °C with a fixed recycle ratio of 1:1 (final effluent flow rate to feed flow rate) and the washout sludge from the third bioreactor present in the final effluent was allowed to be recycled to the first bioreactor. The pH of the first bioreactor was controlled at 5.5, while the pH values of the other two bioreactors were not controlled. Under the optimum chemical oxygen demand loading rate of 18 kg/m3d (based on the feed chemical oxygen demand load and total volume of the three bioreactors) with a bioreactor volumetric ratio of 5:5:20, the system provided the highest gas production performance in terms of yields of both hydrogen and methane and the highest overall chemical oxygen demand removal. Interestingly, the three-stage anaerobic sequencing batch reactor system gave a much higher energy production rate and a higher optimum chemical oxygen demand loading rate than previously reported anaerobic systems since it was able to maintain very high microbial concentrations in all bioreactors with very high values of both alkalinity and solution pH, especially in the third bioreactor, resulting in sufficient levels of micronutrients for anaerobic digestion.

Water footprint of the Sobradinho hydropower plant, Northeastern Brazil

Hydroelectricity is responsible for the greatest fraction of the electric energy generated in Brazil. The water footprint of hydropower plants (WFP) is an important indicator of the sustainable and efficient use of water resources. In this context, WFP of the Sobradinho Hydropower Plant was determined for the period from 2003 to 2012, taking into account the reservoir’s historical variation for the flooded area. To accomplish this, monthly series of electric energy production, flooded area, evaporation and evapotranspiration rates were used. Average gross and net evaporation were 2,031 and 1,577 mm year-1, respectively. The average power generation of this facility in the analyzed period was 462 MW, and the flooded area of its reservoir presented an average value of 3,054 km². Based on the monthly data, the gross and net water footprints were, respectively, 417 and 325 m³ GJ-1. Based on these results, it can be concluded that the changes in the reservoir’s area exert direct and important influence on the WFP estimates of the Sobradinho hydropower plant. The WFP estimates in this study were different from other studies that adopted a constant value of 4,214 km² for this reservoir’s area, which is taken based on the normal water level of the plant operation.

Nonlinear model predictive control of a vortex-induced vibrations bladeless wind turbine

In this paper, a nonlinear model predictive controller (NMPC) is proposed for a vortex-induced vibrations bladeless wind turbine (BWT). The BWT consists of a long rigid cylinder mounted on a flexible beam. The nonlinear dynamic model of the transverse vibrations of the BWT is obtained under the fluctuating lift force due to periodically shedding vortices. The NMPC method is used to design a controller that achieves maximum energy production rate. It is observed that the power generation of the NMPC drops in high wind speeds due to a mismatch between the vortex shedding frequency and the structural natural frequency. Therefore, a secondary gain-scheduling (GS) controller is proposed to virtually increase the natural frequency of the structure to match the vortex shedding frequency for high winds. Although previous studies predicted the output power of the studied BWT to be less than 100 W, with the proposed GS-NMPC scheme the output power reaches the value of 1 kW. Therefore, the capability of the BWT as a renewable energy generation device was highly underestimated in the literature. The computed values of the aero-mechanical efficiency suggest the BWT as a major competitor to the conventional wind turbines.