Generic Energy Research Articles

Energy flow modeling and optimal operation analysis of the micro energy grid based on energy hub

The energy security and environmental problems impel people to explore a more efficient, environment friendly and economical energy utilization pattern. In this paper, the coordinated operation and optimal dispatch strategies for multiple energy system are studied at the whole Micro Energy Grid level. To augment the operation flexibility of energy hub, the innovation sub-energy hub structure including power hub, heating hub and cooling hub is put forward. Basing on it, a generic energy hub architecture integrating renewable energy, combined cooling heating and power, and energy storage devices is developed. Moreover, a generic modeling method for the energy flow of micro energy grid is proposed. To minimize the daily operation cost, a day-ahead dynamic optimal operation model is formulated as a mixed integer linear programming optimization problem with considering the demand response. Case studies are undertaken on a community Micro Energy Grid in four different scenarios on a typical summer day and the roles of renewable energy, energy storage devices and demand response are discussed separately. Numerical simulation results indicate that the proposed energy flow modeling and optimal operation method are universal and effective over the entire energy dispatching horizon.

A generic energy systems model for efficient ship design and operation

There is an environmentally and economically motivated need to reduce the fuel consumption and air emissions of ships. To achieve a reduction in energy consumption, the energy flow in the entire energy system of a ship must be analysed in both the component, or subsystem, level as well as in a holistic way to capture the interactions between the components. Of the currently available energy consumption monitoring and prediction methods or models, no single model or method can be used to assess the energy efficiency of an arbitrary vessel in both the early design phase and during operation. This study presents a new generic ship energy systems model that can be used for this purpose. This new model has two parts: one for the assessment of a ship’s energy consumption based on an ordinary static power prediction and one for advanced operational analysis, considering hydrodynamic and machinery systems effects. A Panamax tanker vessel was used as the case study vessel to prove the versatility of the model for five example simulations for the design and operation of ships. The examples include variations of the main dimensions, propeller design, engine layout and the operational profile on a North Atlantic route. From the results, different areas with a potential for energy savings were identified.

Optimal Dispatch of Responsive Loads and Generic Energy Storage Units in a Co-Optimized Energy and Reserve Market for Smart Power Systems

Responsive loads and energy storage units can play an important role to provide an economic and reliable operation of future energy systems. In this article, a stochastic energy and reserve market clearing scheme is presented considering demand response programs and energy storage devices. The approach is proposed to deal with stochastic and non-dispatchable renewable sources with high levels of penetration in the energy system. A two-stage stochastic programming scheme is formulated where in the first stage the energy market is cleared according to the forecasted amount of wind generation and demands and in the second stage the real time market is solved according to the assumed scenarios. Both stages are formulated as mixed integer linear programming problems. The introduced stochastic day-ahead scheduling scheme also regards load forecasting errors and unit/line outages. In order to generate sufficient scenarios for wind generation and demand uncertainties, the scenario generation procedure is defined as an optimization problem which is solved by particle swarm optimization algorithm.

Gravitational collapse of dark energy field configurations and supermassive black hole formation

Dark energy is the dominant component of the total energy density of our Universe. The primary interaction of dark energy with the rest of the Universe is gravitational. It is therefore important to understand the gravitational dynamics of dark energy. Since dark energy is a low-energy phenomenon from the perspective of particle physics and field theory, a fundamental approach based on fields in curved space should be sufficient to understand the current dynamics of dark energy. Here, we take a field theory approach to dark energy. We discuss the evolution equations for a generic dark energy field in curved space-time and then discuss the gravitational collapse for dark energy field configurations. We describe the 3 + 1 BSSN formalism to study the gravitational collapse of fields for any general potential for the fields and apply this formalism to models of dark energy motivated by particle physics considerations. We solve the resulting equations for the time evolution of field configurations and the dynamics of space-time. Our results show that gravitational collapse of dark energy field configurations occurs and must be considered in any complete picture of our Universe. We also demonstrate the black hole formation as a result of the gravitational collapse of the dark energy field configurations. The black holes produced by the collapse of dark energy fields are in the supermassive black hole category with the masses of these black holes being comparable to the masses of black holes at the centers of galaxies.

Design and Analysis of Generic Energy Management Strategy for Controlling Second-Life Battery Systems in Stationary Applications

Recently, second-life battery systems have received a growing interest as one of the most promising alternatives for decreasing the overall cost of the battery storage systems in stationary applications. The high-cost of batteries represents a prominent barrier for their use in traction and stationary applications. To make second-life batteries economically viable for stationary applications, an effective power-electronics converter should be selected as well. This converter should be supported by an energy management strategy (EMS), which is needed for controlling the power flow among the second-life battery modules based on their available capacity and performance. This article presents the design, analysis and implementation of a generic energy management strategy (GEMS). The proposed GEMS aims to control and distribute the load demand between battery storage systems under different load conditions and disturbances. This manuscript provides the experimental verification of the proposed management strategy. The results have demonstrated that the GEMS can robustly handle any level of performance inequality among the used-battery modules with the aim to integrate different levels (i.e., size, capacity, and chemistry type) of the second-life battery modules at the same time and in the same application.

Mechanisms Responsible for the Large Piezoelectricity at the Tetragonal-Orthorhombic Phase Boundary of (1-x)BaZr0.2Ti0.8O3-xBa0.7Ca0.3TiO3 System.

Recently it was found that in the lead-free (1-x)BaZr0.2Ti0.8O3-xBa0.7Ca0.3TiO3 (BZT-xBCT) system, the highest piezoelectric d33 coefficient appears at the tetragonal (T) – orthorhombic (O) phase boundary rather than the O – rhombohedral (R) phase boundary, but the physical origin of it is still unclear. In this work we construct the phase diagram of the BZT-xBCT system using a generic sixth-order Landau free energy polynomial and calculate the energy barrier (EB) for direct domain switching between two variants of the stable low-symmetry ferroelectric phase. We find that the EB at the T-O phase boundary is lower than that at the O-R phase boundary and EB may serve as a rigorous quantitative measure of the degree of polarization anisotropy through Landau potential. The calculations may shed some light on the physical origin of the highest piezoelectric coefficients as well as the softest elastic compliance at the T-O phase boundary observed in experiments.

Electron-neutral scattering cross sections for CO2: a complete and consistent set and an assessment of dissociation

This work proposes a complete and consistent set of cross sections for electron collisions with carbon dioxide (CO2) molecules to be published in the IST-Lisbon database with LXCat. The set is validated from the comparison between swarm parameters calculated using a two-term Boltzmann solver and the available experimental data. The importance of superelastic collisions with CO2(0 1 0) molecules at low values of the reduced electric field is discussed. Due to significant uncertainties, there are ongoing debates regarding the deconvolution of cross sections that describe generic energy losses at specific energy thresholds into cross sections that describe individual processes. An important example of these uncertainties is with the dissociation of CO2, for which the total electron impact dissociation cross section has not yet been unambiguously identified. The available dissociation cross sections are evaluated and discussed, and a strategy to obtain electron-impact dissociation rate coefficients is suggested.

Machine Tool Energy Efficiency – A Component Mapping-Based Approach

The European Commission outlined the energy-related products (ErPs) meant to be labelled and regulated in order to achieve the goals to reduce the European amount of CO2-emissions by 20% by 2020 compared to projections. Machine tools (MTs) fulfill all mandatory criteria to be categorized as ErP, namely: significant sales volume, significant environmental impact and significant improvement potential. However, the energy consumption and energy efficiency of MTs strongly depend on their utilization. A generic evaluation approach for quantifying a MT’s energy efficiency is still under development by the working group ISO/TC 39/WG 12, which drives forward the ISO 14955 series for environmental evaluation of MTs.This work presents an approach for a generic energy efficiency evaluation of MTs. Component-specific behavior is investigated and aggregated in order to entirely describe the power consumption of a MT for any utilization by power mapping. Power maps contain all possible operational scenarios under the condition of the component boundaries. The approach allows a generic MT evaluation independent on the utilization and forms the base for future MT energy efficiency labelling. The presented approach is applied and validated in a practical case study.

Sequence Dependence of Viral RNA Encapsidation.

We develop a Flory mean-field theory for viral RNA (vRNA) molecules that extends the current RNA folding algorithms to include interactions between different sections of the secondary structure. The theory is applied to sequence-selective vRNA encapsidation. The dependence on sequence enters through a single parameter: the largest eigenvalue of the Kramers matrix of the branched polymer obtained by coarse graining the secondary structure. Differences between the work of encapsidation of vRNA molecules and of randomized isomers are found to be in the range of 20 kBT, more than sufficient to provide a strong bias in favor of vRNA encapsidation. The method is applied to a packaging competition experiment where large vRNA molecules compete for encapsidation with two smaller RNA species that together have the same nucleotide sequence as the large molecule. We encounter a substantial, generic free energy bias, that also is of the order of 20 kBT, in favor of encapsidating the single large RNA molecule. The bias is mainly the consequence of the fact that dividing up a large vRNA molecule involves the release of stored elastic energy. This provides an important, nonspecific mechanism for preferential encapsidation of single larger vRNA molecules over multiple smaller mRNA molecules with the same total number of nucleotides. The result is also consistent with recent RNA packaging competition experiments by Comas-Garcia et al.1 Finally, the Flory method leads to the result that when two RNA molecules are copackaged, they are expected to remain segregated inside the capsid.

A concise, approximate representation of a collection of loads described by polytopes

Aggregations of flexible loads can provide several power system services through demand response programs, for example load shifting and curtailment. The capabilities of demand response should therefore be represented in system operators’ planning and operational routines. However, incorporating models of every load in an aggregation into these routines could compromise their tractability by adding exorbitant numbers of new variables and constraints.In this paper, we propose a novel approximation for concisely representing the capabilities of a heterogeneous aggregation of flexible loads. We assume that each load is mathematically described by a convex polytope, i.e., a set of linear constraints, a class which includes deferrable loads, thermostatically controlled loads, and generic energy storage. The set-wise sum of the loads is the Minkowski sum, which is in general computationally intractable. Our representation is an outer approximation of the Minkowski sum. The new approximation is easily computable and only uses one variable per time period corresponding to the aggregation’s net power usage. Theoretical and numerical results indicate that the approximation is accurate for broad classes of loads.

A Flexoelectric Double-Curvature Nonlinear Shell Energy Harvester

Flexoelectricity possesses two gradient-dependent electromechanical coupling effects: the direct flexoelectric effect and the converse flexoelectric effect. The former can be used for sensing and energy generation; the latter can be used for ultraprecision actuation and control applications. Due to the direct flexoelectricity and large deformations, theoretical fundamentals of a generic nonlinear distributed flexoelectric double-curvature shell energy harvester are proposed and evaluated in this study. The generic flexoelectric shell energy harvester is made of an elastic double-curvature shell laminated with flexoelectric patches and the shell experiences large oscillations, such that the von Karman geometric nonlinearity occurs. Flexoelectric output voltages and energies across a resistive load are evaluated using the current model in the closed-circuit condition when the shell is subjected to harmonic excitations and its steady-state voltage and power outputs are also calculated. The generic flexoelectric shell energy harvesting theory can be simplified to shell (e.g., cylindrical, conical, spherical, paraboloidal, etc.) and nonshell (beam, plate, ring, arch, etc.) distributed harvesters and the simplification procedures are demonstrated in three cases, i.e., a cylindrical shell, a circular ring and a beam harvester. Other shell and nonshell flexoelectric energy harvesters with standard geometries can also be defined using their distinct two Lamé parameters and two curvature radii.

Haptic Assembly Using Skeletal Densities and Fourier Transforms1

Haptic-assisted virtual assembly and prototyping has seen significant attention over the past two decades. However, in spite of the appealing prospects, its adoption has been slower than expected. We identify the main roadblocks as the inherent geometric complexities faced when assembling objects of arbitrary shape, and the computation time limitation imposed by the notorious 1 kHz haptic refresh rate. We addressed the first problem in a recent work by introducing a generic energy model for geometric guidance and constraints between features of arbitrary shape. In the present work, we address the second challenge by leveraging Fourier transforms to compute the constraint forces and torques. Our new concept of “geometric energy” field is computed automatically from a cross-correlation of “skeletal densities” in the frequency domain, and serves as a generalization of the manually specified virtual fixtures or heuristically identified mating constraints proposed in the literature. The formulation of the energy field as a convolution enables efficient computation using fast Fourier transforms (FFTs) on the graphics processing unit (GPU). We show that our method is effective for low-clearance assembly of objects of arbitrary geometric and syntactic complexity.

Analysis and Modeling of Selected Energy Consumption Factors for Embedded ECG Devices

Heart attack is a life threaten cardiac disease. Although advances in information and communication technologies have brought us tiny embedded electrocardiogram (ECG) devices and efficient algorithms to continuously monitor and analyze ECG signals, energy consumption of the system is a critical concern for practical usage. However, there have been not many studies focusing on energy consumption of mobile ECG monitoring, especially lacking guidelines in selecting proper data communication strategies and computational algorithms. In this paper, we examine three possible modes of data transmissions for energy consumption. A generic energy consumption model and a simulated environment were developed to examine the influence of different communication strategies and ventricular fibrillation detection methods in terms of computational efficiency and power consumption. This paper shows that the total ratio of energy saving between mode transmitting all data and our proposed event transmission is up to 84.67% per 508 s of data segment.

Energy Consumption Analysis of Wireless Ad hoc Networks Routing Protocols under Different Energy Models

The energy consumption of the wireless nodes is one of the major issues in wireless ad hoc networks. Energy saving is an important objective of various routing protocol algorithms. In this paper energy consumption by the wireless nodes using two routing protocols AODV and DYMO for communication has been compared with respect to generic, micamotes and micaZ energy models for a particular simulation scenario. This comparison is based on performance in terms of following metrices: average jitter, end to end delay, throughput, energy consumption in transmit mode, energy consumption in receive mode, and energy in idle modes. Results show that the mica-motes energy model is best as compared to micaZ and generic energy models and also observed that the ADOV outperform DYMO routing protocol in generic, mica-motes and micaZ energy radio models.

Wood energy interventions and development in Kano, Nigeria: A longitudinal, ‘situated’ perspective

This paper provides a longitudinal, critical overview of woodfuel interventions in Kano and northern dryland Nigeria. Woodfuel still accounts for up to two-thirds of energy consumption, yet fuelwood-related issues are often ‘by-products’ of ‘higher priority’ energy–environment–development preoccupations. We suggest that energy policy has historically reflected preoccupations dominated by fossil fuel and new and renewable energy concerns, thereby raising questions about whether and to what extent such interventions reflect a desire to address woodfuel in its own right. The paper adopts a selective critique of some foundational assumptions about the energy–poverty–development nexus, notably in relation to energy transition theory and practice, to explain such outcomes and their practical and policy implications. In doing so, the analysis places particular emphasis on context, to demonstrate why the role of ‘situatedness’ must be better appreciated in energy circles and, equally importantly, acted upon during woodfuel interventions. More meaningful interventions, the paper concludes, should be based less on insights deriving from generic (wood) energy systems, hierarchies and relations, and considerably more on the lessons to be learned from the dynamic and complex realities of actual (wood) energy practices, networks and economies. In this, as in much else, context remains key.

Biogas Power Plants in Poland—Structure, Capacity, and Spatial Distribution

This paper presents the analysis and evaluation of biogas power plant capacity in Poland based on the generic structure and energy production. These issues are also presented from the point of view of the obtained energy and biogas energy production in Poland against selected European Union countries. The paper also indicates a significant diversity in the spatial distribution of biogas plants in Poland. It also discusses the importance of biogas plants as one of the elements of bottom-up development of the second tier administrative units. There are 231 biogas power plants in Poland (as of 2013), which are based on biogas from landfill sites, biogas from wastewater treatment plants, and agricultural biogas. The generic structure of biogas power plants in Poland is dominated by power plants based on biogas from landfill. Despite the fact that Poland has large resources of agricultural substrate, there are very few biogas power plants based on agricultural biogas. There are no biogas power plants in almost 60% of poviats in Poland, despite the fact that every poviat in Poland has enough of this substrate at its disposal. This article contributes innovative elements to existing knowledge on biogas power plants in Poland, thanks to its comprehensive treatment of the problem of biogas power plants in Poland and because it urges local authorities and local communities to behave more ecologically, as well as promoting endogenous factors of the economic development of a given region.

A Parametric Energy Model for Energy Management of Long Belt Conveyors

As electricity prices continue to rise, the increasing need for energy management requires better understanding of models for energy-consuming applications, such as conveyor belts. Conveyor belts are used in a wide range of industries, including power generation, mining and mineral processing. Conveyor technological advances are leading to increasingly long conveyor belts being commissioned. Thus, the energy consumption of each individual belt conveyor unit is becoming increasingly significant. This paper proposes a generic energy model for belt conveyors with long troughed belts. The model has a two-parameter power equation, and it uses a partial differential equation to capture the variable amount of material mass per unit length throughout the belt length. Verification results show that the power consumption calculations of the newly proposed simpler model are consistent with those of a known non-linear model with an error of less than 4%. The online parameter identification set-up of the model is proposed. Simulations indicate that the parameters can be identified successfully from data with up to 15% measurement noise. Results show that the proposed model gives better predictions of the power consumed and material delivered by a long conveyor belt than the steady-state models in the current literature.

Nearly Zero Energy Building (NZEB) using IoT and Smart Grid

Current energy policy and climate mitigation goals require distinct reductions of the primary energy demand in the building sector. The existing building stock poses challenge since clear-cut technical and economical retrofit strategies for different types of existing buildings are still not established. The goal of the study is to identify such retrofit strategies to achieve optimal cost levels and to assess costs and benefits of nearly zero energy buildings (nZEB). Firstly building types are defined by covering single-family houses, multi-family houses, office buildings and school buildings. Secondly, a large set of generic energy efficiency measures are described, covering seven strategic fields, namely building envelope measures, heating and hot water supply technologies and fuel choice, ventilation and lighting systems, electricity and district heat mixes. This covers the usage of smart home appliances, eco-friendly building ventilation system. Thirdly, energy performance is calculated based on technical and physical characteristics and using building energy balance software. Fourthly, investment costs and life cycle costs are established based on unitary costs of building elements and building technologies. Cost-effectiveness is determined based on he net present value method which is compared to the annuity method for a couple of cases. The integration of smart grid and IoT(Internet of Things) is a new concept for conserving more.

Energy-aware two-way relaying networks under imperfect hardware: optimal throughput design and analysis

In this paper, we propose a new formula for achieving optimal throughput in energy-aware cooperative networks with generic time and power energy harvesting protocol, namely time power switching based relaying (TPSR). Especially, this investigation analyzes the impact of imperfect hardware at the relay node and the destination node in the two-way relaying networks (TWRN). This analysis enables us to derive the closed-form expressions of outage probabilities of signal-to-noise and distortion ratio (SNDR) at the destination nodes under the effect of hardware impairments. Interestingly, the optimal policy of joint wireless information and energy transfer is designed to maximize the system throughput by finding the optimal time switching and power splitting fractions in the proposed TPSR protocol. An important achievement is that the proposed optimal design offers the maximum throughput of system when we consider the trade-off between throughput and time-power factors in energy harvesting protocol by both numerical method and simulation. Numerical results provide practical insights into the performance of energy-aware TWRN under hardware impairments. Monte-Carlo method is also deployed to corroborate the accuracy of analytical derived expressions.

A generic energy optimization framework for heterogeneous platforms using scaling models

Mobile platforms are becoming highly heterogeneous by combining a powerful multiprocessor system-on-a-chip (MpSoC) with numerous other resources, including display, memory, power management IC, battery and wireless modems into a compact package. Furthermore, the MpSoC itself is a heterogeneous resource that integrates many processing elements such as CPU cores, GPU, video, image, and audio processors. Platform energy consumption and responsiveness are two major considerations for mobile systems, since they determine the battery life and user satisfaction, respectively. As a result, energy minimization approaches targeting mobile computing need to consider the platform at various levels of granularity. In this paper, we first present power consumption, response time, and energy consumption models for mobile platforms. Using these models, we optimize the energy consumption of baseline platforms under power, response time, and thermal constraints with and without introducing new resources. Finally, we validate the proposed framework through experiments on Qualcomm’s Snapdragon 800 Mobile Development Platforms.