bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Changes in Alloy Anodes for Li-Ion Batteries
Authors: Adams Jacob N. , Ausderau Logan J. , Nelson George J.
Published: October 2018

Tin (Sn) alloy electrodes show great potential for advancing battery performance due to the high capacity of tin. To realize this potential, the volumetric expansion during the lithiation process must be mitigated. One means of mitigating volumetric expansion of tin is to alloy it with copper to create Cu6Sn5. Such alloy electrodes retain some of the high capacity of tin, while attempting to accommodate volumetric changes with the addition of the malleable copper. Lithiation and delithiation tests were conducted with the Cu6Sn5 pellet electrodes to produce microstructural changes at the electrode surface. To observe and quantify these microstructural changes, x-ray microtomography was performed on electrode samples after electrochemical testing. The microtomography data was reconstructed into a 3D image, segmented, and the continuous phase size distribution (PSD) of each electrode sample was analyzed. The electrodes lithiated to 0 V vs Li/Li+ and then delithiated to 0.2 V vs. Li/Li+ showed the most substantial reduction in overall PSD compared to the other samples. This suggests that full lithiation of the Sn present in the alloy electrodes followed by partial delithiation of the Li4.4Sn to Li2CuSn can cause substantial microstructural changes related to volume expansion on lithiation and structural collapse upon delithiation. The electrodes fully lithiated to 0 V vs Li/Li+ and not delithiated show a higher overall phase size distribution, including all solid phases, than the pristine sample and the electrode samples that were partially lithiated to 0.2 V vs. Li/Li+ and delithiated to 1.5 V vs. Li/Li+. The higher overall phase size distribution that is shown by the sample that was fully lithiated and not delithiated is evidence of the significant volumetric expansion of the Cu6Sn5 compound due to lithiation. During this process of volumetric expansion, the phase size distribution of the Cu6Sn5/Sn phase is shown to decrease. When the volumetric expansion of the lithiated electrode samples and the volumetric contraction of the delithiated electrode sample are considered together, it can be inferred that the microstructural changes that are observed, such as the decrease in phase size distribution of the Cu6Sn5/Sn phase, can be attributed to the volumetric expansion and contraction of the compound during the lithiation and delithiation process.
Biogas Potentials Evaluation of Household Wastes in Johannesburg Metropolitan Area Using the Automatic Methane Potential Test System (AMPTS) II
Authors: Nwaigwe Kevin N. , Agarwal Abhishek , Anyanwu Emmanuel E.
Published: October 2018

A work on biogas potentials evaluation of household wastes in Johannesburg metropolitan area using the Automatic Methane Potential Test System (AMPTS) II is presented. The AMPTS II consists of three units — the sample incubation unit, CO2 absorption unit and the gas volume measuring device. Organic fraction of wastes collected from households within Johannesburg metropolis were sorted, ground and prepared into slurry by mixing with water. Microcrystalline cellulose powder with 3.5% loss on drying and 0.28g/cc density was used as control substrate while anaerobic sludge collected from a functional biogas reactor was used as inoculum. Anaerobic sludge was classified as sample A, household waste containing mainly non-food waste was labelled sample B, sample C was microcrystalline cellulose used as positive control while household waste composing of mainly food waste was classified as sample D. Each sample was fed into a 50 mL bottle reactor in triplicates and stirred in a clockwise direction continuously for 5 minutes with a pulse interval of 1 minute at a set temperature of 37°C for 30 days retention time. NaOH solution was prepared into solution following standard procedure and mixed with a prepared 0.4 % Thymolpthalein solution. The resultant solution was poured into the 100 mL bottles of the CO2 unit. Produced biogas was measured through water displacement in the volumetric bath and values read off through a data-logger connected to a laptop. Results indicated biochemical methane potential (BMP) of 69–800 NmL/gvs and biogas composition with more than 50% methane before CO2 fixing and over 80% after CO2 fixing. Given that the average amount of waste generated per person per day in South Africa is over 0.7 kg, there is huge potentials for biogas production from household wastes in Johannesburg.
The Features of Closed Brayton Cycle and Sub-Critical Combined Cycles Coupled With (Very) High Temperature Gas-Cooled Reactor
Authors: Qu Xinhe , Yang Xiaoyong , Zhao Gang , Wang Jie
Published: October 2018

High Temperature Gas-cooled Reactor (HTR) and Very High Temperature Gas-cooled Reactor (VHTR), are the most promising and achievable fourth-generation nuclear reactor for its inherent safety. In this paper, the performance of Closed Brayton Cycle (CBC) and two sub-critical combined cycles were investigated and compared. The CBC is a recuperated and inter-cooling closed Brayton cycle. Two combined cycles include the sub-critical Rankine cycle without steam reheating (Simple Combined Cycle, SCC) and a sub-critical reheated Rankine cycle (Reheated Combined Cycle, RCC). The topping cycles of SCC and RCC are both a simple Brayton cycle, and connect with the bottoming cycles by a sub-critical heat recovery steam generator (HRSG). Physical and mathematical models of three different thermodynamic cycles were established. Within the temperature range of the HTR and VHTR, the effects and mechanism of key parameters, such as reactor outlet temperature, steam temperature and pressure, on features of three different cycles were investigated. The results showed the elevated reactor outlet temperature could obviously enhance efficiency of three cycles. The results showed that RCC had the highest efficiency while SCC had the lowest efficiency, and the efficiency of CBC is slightly lower than that of RCC. The results could be helpful to understand and develop the power conversion system coupled with (V)HTR in the future.
Research and Practice of Nuclear Equipment Procurement and Supply Management Based on “Internet+” Mode
Authors: Zhou Hui , Ding Liang , Shi Xu , Li Zhongkui
Published: October 2018

The procurement and supply management of nuclear power equipment are carried out offline in tradition, the mode is mono and inflexible, the organizational process assets is poorly accumulated, the implementation process is not transparent, the tracking control effect is poor, the efficiency is relatively low. Adopting the information technology has acquired certain effect in improving organizational process assets accumulation although, the information is fragmented, efficiency improvement is not obvious. Study on “Internet + Procurement” was carried out since the year of 2015, compared with the traditional model, all the business and supplier information of procurement management of nuclear power equipment were interconnected, the whole process of procurement and supply management are through the internet, it is a innovation of the procurement and supply management mode using information technology. a wealth of data was accumulated for further analysis, an interconnected network was built between buyer and supply, significant change was brought out to the field of nuclear power equipment procurement, the role of this synergistic effect, contributes to the shortening of the construction period of nuclear power projects.
Cavitation Modelling in Different Designs of Micro Kaplan Hydro-Turbine
Authors: ElGammal Tarek , Sakamoto Tomoki , Amano Ryoichi S.
Published: October 2018

The paper investigates the cavitation in micro-turbomachinery, using a small-sized water system. Unsteady numerical model is architected to predict cavitating flows through a 7.5 cm axial hydro-turbine working at 2.8 m water head. Based on the validated simulations, specific turbine designs (regular design and rim-drive turbines) are simulated with cavitating flow conditions including different rotation speeds (1000–5000 rpm) and outlet pressures (0, -24, -48, -96, kPa gage). Phase change interactions (liquid water and vapor) were considered by adding the physics models of Volume of Fluid (VOF) multiphase, cavitation, and Large Eddy Simulation (LES) turbulence. Records featured spatial variation in the cavitation pattern between the two designs. Rim-drive turbine stands against cavitation along the rim integration lines, but it starts the hub cavitation earlier than the regular turbine. The proposed rim-drive bests the regular geometry before cavitation, and the relative efficiency gap increased to be 16% at extreme cavitation condition.
An Investigation of the Influence of Fluidics Insertion Technique on Acetylene/Argon Gas Additives to LPG on the Turbulent Lean Premixed Flame Characteristics for an EV Burner
Authors: Hassan Sameh H. , Emara Ahmed A. , Elkady Mahmoud A.
Published: October 2018

A series of experiments were performed on a vertical EV burner with a constant coflow air of 873 L /min to generate turbulent lean premixed flow in order to study the impact of the addition of Acetylene/Argon mixture to the liquefied petroleum gas (LPG) on the temperature field and flame structure. The fluidics mechanism was inserted at a fixed position inside the entry section of the EV burner assembly. The flow rates of fuel (LPG/C2H2/ Ar) and air were measured using calibrated rotameters. The different volume ratios of the fuel constituents (at a specified fuel flow rate) were admitted via three solenoid valves at the entry section of each stream prior to mixing and monitored using a labview program. The axial temperature profiles at different operating conditions were measured using a bare wire Pt-Pt -10% Rh (type S) thermocouple of wire diameter 250 μm. Flame images were obtained — before and after fluidics insertion — using a high resolution Canon 6D 20MP digital camera. The selection of the different considerated cases was based on flame stability. The experimental program aims at identifying and analyzing the changes in flame characteristics (flame length, axial profiles of mean gas temperature, NOx concentration and overall combustion efficiency) resulting from the insertion of fluidics while considering different proportions of the fuel constituents) (including pure LPG, as a reference case). In all experiments flame stabilization was ensured. The results obtained indicate the following: it was noticed that in most cases of pure LPG only, and other mixtures the images shows increase in both the length and luminosity of the flame as a result of higher degrees of swirl due to the fluidics insertion while the temperature profiles of the different flames were changed. It was indicated that NOx trend was decreased by 52% while the combustion efficiency was improved by 2.5%.
Gas Turbine Engine Price Estimation Using Artificial Neural Network
Authors: Rowlands David Olusina , Savill Mark
Published: October 2018

Gas turbine engine prices vary widely. Any organisation planning to invest in a project involving the use of gas turbine engines, as prime mover, must perform a robust economic analysis to guide the organisations investment decisions. One major element that could greatly influence the outcome of an economic analysis, and eventual organisational decisions and planning, is gas turbine engine acquisition price.

This study applies artificial neural networks to estimate gas turbine engine price. A supervised network learning strategy has been adopted to train the network from a dataset of historical records of gas turbine engine performance parameters and engine price. Numerical gradient checking has been performed to validate the computed cost function with quantified similarity obtained in the order of 10−9. The challenge of neural network overfitting has been minimized by applying a regularization technique. As such, the developed network closes reflects real world observations. To validate the network predictions, the developed neural network has been used to estimate the price of known gas turbine engine units with 95% to 99.9% accuracy.
Condensing Turbine Exhaust Steam in a Steam Surface Condenser Using Multiple Sources of Cooling Water
Authors: Nadig Ranga
Published: October 2018

Scarcity and restrictions in the use of cooling water has prompted power plant developers to explore multiple sources of cooling mediums to condense turbine exhaust steam in a steam surface condenser. The cooling mediums can have different chemistries dictating selection of different tube and tubesheet materials. The flowrate, inlet temperature and temperature rise for the cooling mediums can be different. Some cooling mediums may not be available during certain times of the year. The resulting steam surface condenser will include multiple smaller tube bundles of various sizes operating with different flowrates and temperatures.

The challenges in designing a condenser that employs multiple sources of cooling medium with different chemistries, flowrates and inlet temperatures are enormous. To ensure reliable operation a number of thermal, hydraulic and mechanical design issues must be carefully evaluated. Determining performance of the entire condenser at off-design conditions with variations in flowrates and inlet temperatures of one or more cooling water streams (or absence thereof) can be complicated.

This paper highlights the major concepts that need to be addressed while designing a steam surface condenser that employs multiple sources of cooling medium to condense the turbine exhaust steam. Critical thermal, hydraulic and mechanical design issues that can impact the performance and reliability of the overall condenser are addressed.
Testing Spark Ignition Engines Converted to Operate on JP-8
Authors: Seibert Michael , DuBois Terry , Scenna Richard , Thampan Tony
Published: October 2018

Testing was performed on commercially available 1 kW spark ignition generators that were modified to operate on JP-8 and other heavy fuels. This approach is motivated by the US Military mandate that only one fuel, JP-8, be taken to the battlefield, and the increased electrical demands at the squad and platoon level. Small units require a portable power source that can meet their energy demands, particularly battery charging. While diesel engines can operate on JP-8, their weight limits their mobility at the platoon level. Spark ignition engines have better power density at the 1 kW level, but must be modified to burn logistically available fuel.

Multiple approaches have been pursued to enable these engines to operate on JP-8. In the present study, the longer term effects of three approaches are examined and compared to an unmodified spark ignition generator operating on gasoline. These approaches include A) chemically altering the fuel as it flows to the engine to create a higher octane mixture, B) modifying the carburetor and using ether starter fluid to preheat the cylinder, and C) electrically heating the cylinder while modifying the fuel system for direct injection. The different generators were characterized by oil sampling at 15 hour intervals. Oil testing included flash point, viscosity, wear elements, and additives. Oil quality and emissions vary with load. Different approaches to conversion perform better at different loads.

It was determined that multiple start-stop cycles with no load resulted in fuel dilution of the lubricating oil in several of the modified engines. Response varied with some of the modified engines maintaining low fuel dilution similar to the gasoline fueled engine while others indicated 15–20% fuel in the oil. During operation at full load, the modified JP-8 burning generators showed 3–5% fuel dilution in the oil while the unmodified gasoline generator was less than 1%.

These experiments illustrate the challenges in developing portable, reliable JP-8 burning power sources. While further research and development is needed in each approach, it was shown that converted spark ignition engines are a promising path to portable logistic power. Oil analysis was shown to identify future research and development efforts to improve this technology.
Reliability Analysis of Offshore Wind Turbines Using Copula
Authors: Hu Weifei , Jiang Zhiyu , Wang Yeqing
Published: October 2018

Offshore structures are subject to severe environmental conditions and require high operating and maintenance costs. At the design stage of an offshore structure, it is necessary to perform load analysis and to consider representative environmental conditions characterized by statistical models. However, many available joint distribution models of the environmental parameters can only describe the correlation of these parameters in a very restricted form. The use of simple probabilistic models without correctly addressing their correlation may lead to significant bias in the reliability analysis. Here, the correlation between three offshore environmental parameters including the significant wave height, wave peak period, and mean wind speed is described by copula. The copula density functions and theoretical derivations of copula correlation parameters using actual sea state data are provided for general applications of reliability analysis of offshore structures. Hindcast data of two representative sites are used to fit the best copula. The developed copula-based joint distribution can be used for accurate reliability analysis of offshore structures considering long-term fatigue loads and extreme responses.
Powering the Pearl: A Study of Cuba’s Energy Autonomy
Authors: Worsham Elizabeth K. , Vargas Esposito Genesis d.
Published: October 2018

Cuba’s national pride comes from their projected autonomy as a communist country, although they have been dependent on other countries to supply them with resources since the revolution. However, Cuba has a high capacity for various forms of renewable energy. This study analyzes the impacts of Cuba’s decline in petroleum use and the rise of renewable energy. There is a lack of primary research on Cuba’s energy infrastructure because of government censorship and availability of reliable data, so this study utilizes accounts from Cuban citizens as well as first-hand observations of the country. Research was conducted through interviews, observations, and written accounts of life in Cuba. The decline of Cuba’s use of petroleum has led to an emphasis on sustainability, affecting people’s lifestyles and the economy. The inability to produce enough electricity has created an inequality between those who are involved in tourist industries and those who are not. However, the dawn of renewable energy is helping to close that gap while protecting Cuba’s energy independence and preventing another Special Period.
Modelling and Simulation of Homogeneous Charge Compression Ignition Engine Fueled by Biodiesel
Authors: Hawi Meshack , Ahmed Mahmoud , Ookawara Shinichi
Published: October 2018

Homogeneous charge compression ignition (HCCI) is a combustion technology which has received increased attention of researchers in the combustion field for its potential in achieving low oxides of nitrogen (NOx) and soot emission in internal combustion (IC) engines. HCCI engines have advantages of higher thermal efficiency and reduced emissions in comparison to conventional internal combustion engines. In HCCI engines, ignition is controlled by the chemical kinetics, which leads to significant variation in ignition time with changes in the operating conditions. This variation limits the practical range of operation of the engine. Additionally, since HCCI engine operation combines the operating principles of both spark ignition (SI) and compression ignition (CI) engines, HCCI engine parameters such as compression ratio and injection timing may vary significantly depending on operating conditions, including the type of fuel used. As such, considerable research efforts have been focused on establishing optimal conditions for HCCI operation with both conventional and alternative fuels. In this study, numerical simulation is used to investigate the effect of compression ratio on combustion and emission characteristics of an HCCI engine fueled by pure biodiesel. Using a zero-dimensional (0-D) reactor model and a detailed reaction mechanism for biodiesel, the influence of compression ratio on the combustion and emission characteristics are studied in Chemkin-Pro. Simulation results are validated with available experimental data in terms of incylinder pressure and heat release rate to demonstrate the accuracy of the simulation model in predicting the performance of the actual engine. Analysis shows that an increase in compression ratio leads to advanced and higher peak incylinder pressure. The results also reveal that an increase in compression ratio produces advanced ignition and increased heat release rates for biodiesel combustion. Emission of NOx is observed to increase with increase in compression ratio while the effect of compression ratio on emissions of CO, CO2 and unburned hydrocarbon (UHC) is only marginal.
Multi-Objective Design Optimization for Distributed Energy Systems With Energy Storage: A Case Study
Authors: Zhang Jian , Cho Heejin , Zhang Hongguang , Yang Fubin
Published: October 2018

As a promising approach for sustainable development, the distributed energy system receives increasing attention worldwide and has become a key topic explored by researchers in the areas of building energy systems and smart grid. In line with this research trend, this paper presents a case study of designing an integrated distributed energy system including photovoltaics (PV), combined cooling heating and power (CCHP) and electric and thermal energy storage for commercial buildings (i.e., a hospital and a large hotel). The subsystems are modeled individually and integrated based on a proposed control strategy to meet the electric and thermal energy demand of a building. A multi-objective particle swarm optimization (PSO) is performed to determine the optimal size of each subsystem with objectives to minimize carbon dioxide emissions and payback period. The results demonstrate that the proposed method can be effectively utilized to obtain an optimized design of distributed energy systems that can minimize environmental and economic impacts for different buildings.
Comprehensive Energy Modeling of Tri-Sol: A Three-in-One Solar Concentrating BIPV/Thermal/Daylighting System
Authors: Lawless Sean , Gorthala Ravi
Published: October 2018

A numerical model was developed in the TRNSYS environment (a transient simulation software) for Tri-Sol, a novel three-in-one solar energy system that produces electricity, hot water, and daylight for commercial buildings, to simulate its annual performance in terms of the three useful energy streams. Even though this model was developed for Tri-Sol, it can also be used for calculating the annual performance of similar concentrating PV/thermal (PV/T) and daylighting systems for various geographical locations. The model simultaneously calculates the codependent electrical and thermal performances, and calculates the useful daylight harvested by the building. The model is versatile and flexible in that any configuration of the modeled system can be properly designed using by changing parameters and inputs inside of TRNSYS.

This model was used to predict the annual performance a single Tri-Sol PV/T module and a single Tri-Sol unit with five such modules as a function of its tilt and geographical location. Then, this model was used to compute the monthly performance of a Tri-Sol array for a 10,000 ft.2 building for varying geographical locations at a fixed tilt angle. These results show the utility and the power of the model for designing combined PV/T-daylighting solar technologies such as Tri-Sol.
Investigation of the Evaporation Processes for Aqueous Ammonia and Aqueous Urea and Guidelines for Using Simplifying Assumptions
Authors: Eldredge Thomas , Thomas Morgan
Published: October 2018

For SCR (selective catalytic reduction) applications both aqueous ammonia and urea reagents are used for NOx reducing agents in exhaust systems. For both diesel engines and small boilers, the reagent injection systems often consist of a few, and in some cases, a single injector, located on the wall of the exhaust pipe or duct. Often numerical modeling is performed to determine the location and orientation of the injectors and to predict the NRMS (normalized root mean square) of the gas phase reducing specie distribution prior to the catalyst. Aqueous ammonia and aqueous urea have significantly different processes from the point of injection to the formation of the gas phase reducing species. Evaporation characteristics are important, but for urea, the molecule must also decompose into ammonia and isocyanic acid. For modeling purposes, a simplifying assumption is frequently made to treat the liquid reagent as liquid water and assume that the evaporation of liquid water satisfactorily emulates the processes of forming the gas phase reducing species for both aqueous ammonia and aqueous urea reagents. In reality, the reagent droplets are binary component mixtures and treating the droplets as a single component, namely water, may significantly depart from reality. Additionally, the evaporation processes for aqueous ammonia and aqueous urea have significantly different behaviors. This paper addresses the potential errors associated with using a single component water drop for emulating the evaporation of aqueous ammonia and aqueous urea. This is accomplished by analyzing binary component evaporation for both aqueous ammonia and aqueous urea. Additionally, the time for the gas phase chemical decomposition of urea into ammonia and isocyanic acid is evaluated for various conditions. Typical decomposition times are compared to droplet evaporation times. Finally, the paper attempts to provide guidelines for determining when treating the drops as a single component may be sufficiently accurate, and when the complexity of modeling binary component evaporation is necessary.
Fast Local Pressure Estimation for Two Dimensional Systems From Molecular Dynamics Simulations
Authors: Yesudasan Sumith , Chacko Sibi
Published: October 2018

Coupling of statistical properties from atomistic simulations to continuum is essential to model many multi-scale phenomena. Often, the system under consideration will be homogeneous in two-dimensions (2-D). But due to the existing coupling methods, the property estimation takes place in three-dimensions (3-D) and then averaged to 2-D, which is computationally expensive due to the 3-D convolutions. A direct 2-D pressure or stress estimation model is lacking in literature. In this work, we develop a direct 2-D pressure field estimation method which is much faster than 3-D methods without losing accuracy. The method is validated with MD simulations on two systems: a liquid film and a cylindrical drop of argon suspended in surrounding vapor. This formulation will enable the study of 2-D fundamental phenomena like passive liquid flows in microlayer, as well as facilitate the coupling of atomistic and continuum simulations with reduced computational cost.
Gas Turbine Fouling Offshore: An Analysis of Engine Air Flow
Authors: Madsen Stian , Yildirim Mehmet Serkan , Bakken Lars E.
Published: October 2018

Optimized operation of gas turbines is discussed for a fleet of eleven LM2500PE engines at a Statoil North Sea offshore field i n Norway. Three engines are generator drivers whilst eight engines are compressor drivers. Several of the compressor drive engines are running at peak load (T5.4 control), hence the production rate is limited by the available power from these engines. The majority of the engines discussed run continuously without redundancy, hence gas turbine uptime is critical for the field’s production and economy.

Two of the compressor drive engines are instrumented with a new static P2 probe in order to have an inlet depression measurement and thus be able to monitor compressor air flow. Compressor air flow has been used as an additional parameter to efficiency, in order to have better analysis methods and better documentation of deterioration rates. The performance gain with online water wash at high water-to-air ratio and upgraded inlet air filter systems, as well as successful operation at longer intervals between offline wash/maintenance stops are thus documented.

An approach for developing a compressor map for mass flow based on field measurements, predictions and deterioration has been performed, as well as correction methods for engine load and ambient conditions in order to be able to compare performance points in various conditions and engine control modes. When monitoring compressor air flow, the Reynolds number effects on axial compressor performance can be analyzed.

Understanding the gas turbine performance deterioration is of vital importance. Trending of its deviation from the engine baseline facilitates load-independent monitoring of the gas turbine’s condition. Instrument resolution and repeatability are key factors in order to have reasonable results on the performance analysis. Based on previous tests and analysis, the compressor air flow rate is the most sensitive parameter for detecting performance deterioration. Unfortunately, gas turbines for offshore operation, are normally not equipped with any air flow measurement devices.
A Novel Design for Reduction of Ammonium Bisulfate Deposition in the Rotary Air Preheater
Authors: Bu Yufan , Wang Limin , Wei Xiaoyang , Deng Lei , Che Defu
Published: October 2018

Nitrogen oxide (NOx) emitted from boilers in coal-fired power plant may be reduced by 90 percent through the application of the selective catalytic reduction (SCR). However, the escaped ammonia from the SCR systems could react with sulfur oxides (SOx) in the flue gas to form ammonium bisulfate (ABS) in exhaust systems. The blockage and corrosion caused by ABS seriously impact the rotary air preheater (RAPH), which would not only increase operating cost on ash-blowing and cleaning but also lead to unplanned outage. To solve the problem, in this paper a novel preheater system is proposed. A single preheater is split into two sub-preheaters, between which the main flue gas flow is mixed with the recirculated flue gas from outlet of the lower-temperature preheater. After the mixing point, a reaction chamber and a precipitator are installed. A numerical finite difference method (FDM) is employed to model the RAPH and obtain the accurate temperature distribution of fluid and heat transfer elements. The initial formation temperatures of (NH4)2SO4 and ABS are 200 °C and 170 °C, respectively, according to the flue gas composition in this work. By calculation, this split design of the RAPH is believed to be effective in reducing deposition of ABS.
Potential Impacts of Net-Zero Energy Buildings With Distributed Photovoltaic (PV) Power Generation on the Electrical Grid
Authors: Kim Dongsu , Cho Heejin , Luck Rogelio
Published: October 2018

This study evaluates potential aggregate effects of net-zero energy building (NZEB) implementations on the electrical grid in simulation-based analysis. Many studies have been conducted on how effective NZEB designs can be achieved, however the potential impact of NZEBs have not been explored sufficiently. As significant penetration of NZEBs occurs, the aggregated electricity demand profile of the buildings on the electrical grid would experience dramatic changes. To estimate the impact of NZEBs on the electrical grid, a simulation-based study of an office building with a grid-tied PV power generation system is conducted. This study assumes that net-metering is available for NZEBs such that the excess on-site PV generation can be fed to the electrical grid. The impact of electrical energy storage (EES) within NZEBs on the electrical grid is also considered in this study. Finally, construction weighting factors of the office building type in U.S. climate zones are used to estimate the number of national office buildings. In order to consider the adoption of NZEBs in the future, this study examines scenarios with 20%, 50%, and 100% of the U.S. office building stock are composed of NZEBs. Results show that annual electricity consumption of simulated office buildings in U.S. climate locations includes the range of around 85 kWh/m2-year to 118 kWh/m2-year. Each simulated office building employs around 242 kWp to 387 kWp of maximum power outputs in the installation of on-site PV power systems to enable NZEB balances. On a national scale, the daily on-site PV power generation within NZEBs can cover around 50% to 110% of total daily electricity used in office buildings depending on weather conditions. The peak difference of U.S. electricity demand typically occurs when solar radiation is at its highest. The peak differences from the actual U.S. electricity demand on the representative summer day show 9.8%, 4.9%, and 2.0% at 12 p.m. for 100%, 50%, and 20% of the U.S. NZEB stocks, respectively. Using EES within NZEBs, the peak differences are reduced and shifted from noon to the beginning of the day, including 7.7%, 3.9%, and 1.5% for each percentage U.S. NZEB stock. NZEBs tend to create the significant curtailment of the U.S. electricity demand profile, typically during the middle of the winter day. The percentage differences at a peak point (12 p.m.) are 8.3%, 4.2%, and 1.7% for 100%, 50%, and 20% of the U.S. NZEB stocks, respectively. However, using EES on the representative winter day can flatten curtailed electricity demand curves by shifting the peak difference point to the beginning and the late afternoon of the day. The shifted peak differences show 7.4%, 3.7%, and 1.5% at 9 a.m. for three U.S. NZEB stock scenarios, respectively.
Metamodeling-Based Performance Analysis for Digital Power Plant
Authors: Zhou Dengji , Wei Tingting , Ma Shixi , Zhang Huisheng , Huang Di , Lu Zhenhua
Published: October 2018

Digital power plant is the theory and method to improve the operating quality of power plant by quantifying, analyzing, controlling and deciding the physical and working objects of power plants in the whole life cycle. Signals and management information of power plants will be digitized, so as to realize information exchange reliably and accurately and large-scale distributed resource sharing based on the network technology. Then optimization decisions and scientific guidance for plant operation will be proposed by intelligent expert system based on the digital resources. Therefore, the foundation of digital power plant is system modeling and performance analysis. However, there are some problems in the process of the modeling performance analysis of digital power plant. For instance, each unit of the system model has different dimensions and different type of mathematical description, and the data or information used for modeling are defined differently and belong to different enterprises, who do not want to share their information. Metamodeling is potential to solve these problems. It defines the specification to describe a unit and the relationship between different elements. Compared with traditional modeling methodologies for thermal systems, metamodeling makes the model more standardized, and the relationship of the model elements is more explicit and better understood by the co-simulation partners. In this paper, the collaborative modeling and simulation platform for digital power plant has been established based on the metamodeling method and the performance of the target plant has been analyzed from different aspects via field data. The metamodeling method consists of three parts: syntax definition, model development and algorithm definition. The result shows that the collaborate modeling and simulation platform can be used to reduce costs, decrease equipment failure rate, and improve plant output, so as to guarantee the safety and increase economics.
A Parametric Study of Wave Interaction With a Rotor Having Hydrofoil Blades
Authors: Yang Yingchen , Jenet Fredrick , Xu Ben , Garza Juan Carlos , Tamayo Benjamin , Chavez Yessica , Reyes Oscar , Fuentes Samuel
Published: October 2018

Our recent progress on studying wave interaction with a lift-type rotor is discussed in this paper. The particular focus is on characterization of the rotor’s unidirectional responsiveness in waves. The rotor consists of six hydrofoil blades in two sets. One blade set has three blades laid out as a vertical-axis wind turbine of the Darrieus type. The other blade set has three blades configured like a Wells turbine. In combination, the formed rotor can be driven by flows in any direction to perform unidirectional rotation about its vertically mounted shaft. This unidirectional responsiveness of the rotor also holds in waves, making the rotor a valuable device for wave energy conversion. For parametric study of the rotor, hydrofoil blades using different cross sectional profiles and chord lengths have been employed to configure the rotor. The rotor was then tested in a wave flume under various wave conditions in a freewheeling mode. Experimental results were analyzed and discussed. The yielded research findings will greatly enhance the fundamental understanding on the rotor performance in waves, and effectively guide the prototype rotor development for practical applications.
A Novel Parameter for the Evaluation of Static Mixers
Authors: Thomas Morgan , Eldredge Thomas , Medina Hector , Fazzina David
Published: October 2018

Static, or motionless, mixers are widely used in applications that involve chemical reactions, heat transfer, blending of fluids, or a combination of these. Within those applications, mixing can affect various parameters such as heat or mass transfer rates, process operating time, cost, safety, and product quality. Therefore, it is crucial to assess the performance of static mixers. In general, their performance is evaluated based on their ability to carry out mixing while minimizing energy loss. To accomplish this, a novel mixing parameter, the M number, is proposed and evaluated. The M number is a unitless parameter that describes the effects of the mixer using entropy change and pressure drop. The parameter is compared to another method of mixing evaluation that relies on Covariance (CoV) change across the mixer. Computational Fluid Dynamics (CFD) is executed using both methods to evaluate two static mixers and compare the results of each method. Potential applications for the M number are discussed and its limitations are noted.
Harvesting Waste Thermal Energy From Military Systems
Authors: Moreno Rondolf J. , Pollman Anthony , Grbovic Dragoslav
Published: October 2018

Military systems greatly depend on the availability of energy. This energy comes mostly in the form of burning fuel in order to produce mechanical work or producing electricity. The ability to extract the most out of these systems aligns with the current focus of energy efficiency, not only in the military, but in society at large. In this research, an infrared camera was used to create an infrared map to infer temperature differences on a gasoline-powered generator at steady state operations. These temperature differences were inputted into an experimental phase during which a digitally-controlled hot plate, water block, variable resistor, and digital acquisitions system were used to measure current output from a single TEG for loads of 1, 10, and 100 Ω, respectively. Data were analyzed and the correlation coefficients determined. These coefficients were modeled a single module and then various array configurations for TEGs in COMSOL. Using the findings, a single commercial 56 mm by 56 mm Be2Te3 TEG can yield 0.72 W of power. Simple calculations yield 72 W of power when 100 modules are joined in 10 sets coupled in parallel with each set containing 10 modules in coupled in series. This would require 560 mm by 560 mm or approximately 2 ft. by 2 ft. of system space to be covered.
Analysis and Operation Optimization of Recompression Supercritical Carbon Dioxide Power Generation System Based on the Power Flow Method
Authors: Li Xia , Chen Qun , Chen Xi
Published: October 2018

Due to the peculiar physical properties, supercritical carbon dioxide (sCO2) is considered as a promising working fluid in power generation cycles with high reliability, simple structure and great efficiency. Compared with the general thermal systems, the variable properties of sCO2 make the system models obtained by the traditional modelling method more complex. Besides, the pressure distribution in the system will affect the distribution of the fluid properties, the fluid properties influencing the heat transfer process will produce an impact on the temperature distribution which will in turn affect the pressure distribution through the mass flow characteristics of all components. This contribution introduces the entransy-based power flow method to analyze and optimize a recompression sCO2 power generation system under specific boundary conditions. About the heat exchanger, by subdividing the heat transfer area into several segment, the fluid properties in each segment are considered constant. Combining the entransy dissipation thermal resistance of each segment and the energy conservation of each fluid in each segment offers the governing equations for the whole heat transfer process without any intermediate segment temperatures, based on which the power flow diagram of the overall heat transfer process is constructed. Meanwhile, the pressure drops are constrained by the mass flow characteristics of each component, and the inlet and outlet temperatures of compressors and turbines are constrained by the isentropic process constraints and the isentropic efficiencies. Combining the governing equations for the heat exchangers and the constraints for turbine and the compressors, the whole system is modeled by sequential modular method. Based on this newly developed model, applying the genetic algorithm offers the maximum thermal efficiency of the system and the corresponding optimal operating variables, such as the mass flow rate of the working fluid in the cycle, the heat capacity rate of the cold source and the recompression mass fraction under the given heat source. Furthermore, the optimization of the system under different boundary conditions is conducted to study its influence on the optimal mass flow rate of the working fluid, the heat capacity of the cold source and the maximum system thermal efficiency. The results proposes some useful design suggestions to get better performance of the recompression supercritical carbon dioxide power generation system.
CFD Analysis of Stall in a Wells Turbine
Authors: Kincaid Kellis , MacPhee David W.
Published: October 2018

The Wells turbine is a self-rectifying device that employs a symmetrical blade profile, and is often used in conjunction with an oscillating water column to extract energy from ocean waves. The effects of solidity, angle of attack, blade shape and many other parameters have been widely studied both numerically and experimentally. To date, several 3-D numerical simulations have been performed using commercial software, mostly with steady flow conditions and employing various two-equation turbulence models. In this paper, the open source code Open-FOAM is used to numerically study the performance characteristics of a Wells turbine using a two-equation turbulence model, namely the Menter SST model, in conjunction with a transient fluid solver.
Evaluation of Flexibility Optimization for Thermal Power Plants
Authors: Hübel Moritz , Prause Jens Hinrich , Gierow Conrad , Hassel Egon , Wittenburg Raphael , Holtz Dorian
Published: October 2018

The increasing share of fluctuating renewable energy sources leads to changing requirements for conventional power plants. The changing characteristics of the residual load requires the conventional fleet to operate with higher load gradients, lower minimum load at improved efficiency levels as well as faster start-ups and provision of ancillary services. Despite the requirements from the electricity market, the value of improving those flexibility parameters is hard to evaluate for power plant operators. In order to quantify the additional benefit that can be achieved by improving flexibility parameters on a certain power plant in a changing market environment, an adjustable load dispatch model has developed for that purpose. Using past electricity market data, the model is validated for typical coal and a typical gas fired power plants by reproducing their operational schedule. In the next step, the model is used to apply parameter changes to the power plants specifications and economic effects are demonstrated. General statements are derived on which flexibility parameter needs to be improved on each power plant type. Furthermore, specific economic evaluations are shown for the reference power plants in order to present the ability of the developed tool to support investment decisions for modernization projects of existing power plants.
Morphometric analysis in different geographical populations of Varroa destructor (Acari: Varroidae) associated with Apis mellifera colonies in Iran
Authors: Farjamfar Mahsa , Saboori Alireza , Nozari Jamasb , Hosseininaveh Vahid
Published: October 2018

Varroa destructor is a major ectoparasitic mite which feeds on the western honey bee, Apis mellifera hemolymph. Morphometric analysis of V. destructor in Iran was performed in order to detect differences within some populations of the species. Totally, 145 female mites were collected from A. mellifera colonies in different geographical regions in Iran and Europe (Spain and France). Eight morphological variables were measured: 1) length of dorsal shield (LDS), 2) width of dorsal shield (WDS), 3) length of genital shield (LGS), 4) width of genital shield (WGS), 5) length of metapodal shield (LMS), 6) width of metapodal shield (WMS), 7) length of anal shield (LAS) and 8) width of the anal shield (WAS). The ratios of LDS/WDS, WDS/LDS, LGS/WGS and LAS/WAS were also calculated. Multivariate analyses demonstrated significant differences in means of body length (LDS) and body width (WDS) between populations. Using principal component analysis (PCA) and cluster analysis with pair group method, five morphological groups were established. PCA analyses were also shown one morphotype, A3, between samples. Collectively, our findings suggest a wide phenotypic plasticity within the populations of Varroa mite in Iran.
The role of education interventions in improving economic rationality
Authors: Kim Hyuncheol Bryant , Choi Syngjoo , Kim Booyuel , Pop-Eleches Cristian
Published: October 2018

Educating for economic rationality

The hypothesis that education enhances economic decision-making has been surprisingly underexplored. Kim
et al.
studied this question using a randomized control trial in a sample of 2812 girls in secondary schools in Malawi. Four years after providing financial support for a year's schooling, they presented the subjects with a set of decision problems (for example, allocating funds to immediate versus future expenses) that test economic rationality. The education intervention enhanced both educational outcomes and economic rationality as measured by consistency with utility maximization in the long run.

Science
, this issue p.
83