Auxiliary Energy Source Research Articles

Dynamic modeling and control of a wind turbine generator with fuel cell, Ultra capacitor stack as an auxiliary storage

The world has turned its focus towards renewable energy sources due to the depletion of fossil fuels. Nuclear energy seems to hold the long term solution to this energy problem. However we know that nuclear energy has its own downfall in the production and the disposal of the radioactive waste produced. Wind energy and solar energy have gained considerable importance. The main problem associated with wind energy is that, due to unpredictable and varying wind speed, the system cannot be used to supply a constant load demand. This also leads to problems in attaching the wind generation system to a common bus. The same problem exists with solar power generation as well. To overcome this problem in this paper we have proposed a solution by adding a fuel cell, ultra capacitor stack as an auxiliary energy source. This energy source is used to supply the power demand during lack of wind. Furthermore the system is designed in such a way that these fluctuations are tolerated and the system is relatively free of harmonics in by using a new topology.

Global parameter of ultrasound exploitation (GPUE) in the reactors for wastewater treatment by sono-Fenton oxidation

Modeling of the sonochemical reactors presents a great challenge due to issues related to the experimental investigation and description of the primary effects of the ultrasound. The main idea proposed in this work was to establish an algorithm consisting of the viable laboratory analyses and basic elements of chemical reaction engineering. In this paper, a novel modeling approach is presented. Proposed approach is characterized by the following; ultrasound was investigated as an auxiliary source of energy and the kinetic constants determined for the basic oxidation reactions, i.e. Fenton type oxidation were treated as independent of the ultrasound. Sonochemical effectiveness factor is expressed as a global parameter of the ultrasound exploitation (GPUE) that was introduced in the kinetic model as the e US factor. Factor e US is modeled as a function of employed frequency, actual power of the transducer, portion of the cavitationally active zone, i.e. dimensionless active volume and the average temperature in the reactor. Lumped system has been assumed. In order to obtain all the necessary data, the experimental study included different sets of experiments. The kinetics of the sonochemical processes, e.g. US/Fe 2+/H 2O 2, US/Fe 2+/ S 2 O 8 2 - , US/Fe 2+/ HSO 5 - was investigated in the term of mineralization of model wastewaters containing different types of organic pollutants. The Weissler dosimetry and peroxodisulfate decomposition upon sonication, were used to facilitate the determination of e US . They follow zero order kinetics, thus can be used as a model reaction to reflect all the primary effects of ultrasound and to establish the empirical correlation for e US calculation. Finally, GPUE has been introduced in the adequate kinetic models and the overall model was validated.

Modeling and simulation of a single phase grid connected photovoltaic system

This paper gives a complete computer simulation program of a single phase grid connected PV system using Matlab/Simulink and SimPowerSystem tool in order to monitor the performance of each unit of the system during a selected day in the year representing a sunny day and another cloudy day using the hourly data of load demand, solar radiation and temperature at The Kharga Oasis site, as a case study. The system consists of a PV array subsystem as the primary source of energy, the electric grid as an auxiliary source of energy, the battery bank as a stand by source that feeds the electrical load in case of grid failure. This paper also focuses on the operation control of the system. This control is on/off switch control according to modes of operation of the system and there is a control of inverter using PI controller to achieve the maximum power point of the PV array. Finally this paper gives the simulation results of the required system output parameters; PV output power, grid power, load power, battery power, and battery voltage and state of charge.

Exergy, ecosystem functioning and efficiency in a coastal lagoon: The role of auxiliary energy

Exergy, as the sum of energy and information contained in a given system due to living organisms, can act as a quality indicator of ecosystems. Here, we investigated the exergy of Marsala Lagoon (Mediterranean Sea), along with microbial (prokaryotic and heterotrophic nanobenthos) biomass, prokaryotic heterotrophic production and extracellular enzymatic activities, and the biochemical composition of sediment organic matter. The aim of the study was to assess the role of auxiliary energy (e.g. hydrodynamic stress) in the ecosystem functioning and efficiency of a ‘detritus sink’ lagoon. Samples were collected at sites characterized by contrasting hydrodynamic and trophic conditions. Exergy transfer through the benthic microbial loop was influenced by two main factors: (1) organic matter bioavailability; and (2) hydrodynamic forcing. At both sites, the values of total exergy were higher in summer than in winter, and the specific exergy decreased from winter to autumn, along with increasing auxiliary energy. Our data indicate that in coastal ‘detritus sink’ systems, auxiliary energy sources can have a crucial role in exergy transfer and ecosystem functioning through modifying the efficiency of transfer to higher trophic levels of the refractory organic detritus, which is otherwise lost by burial in the sediment. As coastal lagoons are often intensively modified by human activities, we conclude that maintenance of the natural hydrodynamic regimes is a key factor in the preservation of the functioning of lagoon ecosystems and of their provision of goods and services to humans.

A Hybrid Fuel Cell Power System

This paper proposes a hybrid fuel cell power system, which consists of a fuel cell, an isolated unidirectional converter, a bidirectional converter, an inverter, and a battery. The fuel cell and the battery are connected to the same voltage bus through an appropriate hybrid full-bridge LLC resonant unidirectional converter and a three-level buck/boost bidirectional converter, respectively. The battery is an auxiliary energy source, powers the load during the system's start state to make it easy for the system to cold start, and provides or absorbs the dynamic power when the load varies and the fuel cell cannot respond immediately, so the system dynamic characteristics are improved. Furthermore, the battery can also provide peak power at overload, so the power rating of the fuel cell can be decreased, which reduces the total system cost. In order to ensure that the system operates with high efficiency, this paper also proposes a power management control scheme, which controls the bidirectional converter operating under buck, boost, or shutdown mode according to the operation condition of the fuel cell and battery, so that the battery can be charged or discharged. The operation of the system during cold start and overload are analyzed in detail. A 1-kW fuel cell power system was built in the laboratory. Experimental results are shown to verify the theoretical analysis.

Simulation based size optimization of a PV/wind hybrid energy conversion system with battery storage under various load and auxiliary energy conditions

In this paper, size of a PV/wind integrated hybrid energy system with battery storage is optimized under various loads and unit cost of auxiliary energy sources. The optimization is completed by a simulation based optimization procedure, OptQuest, which integrates various heuristic methods. In the study, the main performance measure is the hybrid energy system cost. And the design parameters are PV size, wind turbine rotor swept area and the battery capacity. The case study is realized for Izmir Institute of Technology Campus Area, Urla, Turkey. The simulation model of the system is realized in ARENA 12.0, a commercial simulation software, and is optimized using the OptQuest tool in this software. Consequently, the optimum sizes of PV, wind turbine and battery capacity are obtained under various auxiliary energy unit costs and two different loads. The optimum results are confirmed using Loss of Load Probability (LLP) and autonomy analysis. And the investment costs are investigated how they are shared among those four energy sources at the optimum points.

A computational study on evaluation of solar absorption cooling system in India

The present paper presents the simulation of a solar powered absorption cooling system with an absorption working pair of lithium bromide and water. The system consists of a flat plate solar collector, a lithium bromide water absorption chiller, an auxiliary energy source and a hot water storage tank. Initially, the thermodynamic behaviour of the cooling system cycle is simulated under various ambient conditions to determine the working conditions of the absorption cooling system compatible with the capacity of the flat plate collector. Computer modelling of a solar absorption cooling system using a flat plate collector was undertaken for all possible climatic conditions of Bahal, India. The results have shown that for each ton of refrigeration a minimum collector area of 26·02 m2 with an optimal water storage tank capacity ranging from 1000 to 1500 L is required, so that the system can operate solely on solar energy for ∼7 h a day.

Thermal analysis of solar biomass hybrid co-generation plants

This article describes a co-generation plant based on the biogas being produced from the waste of distillery plant and highlights the possible configuration in which the plant can be hybridized with auxiliary solar energy source having the advantage of using financial incentives in several countries. In hybridization, the solar heat is used for heating the boiler feed water. The solar heat-generating unit consists of line focus parabolic trough collector, heat transportation system and heat delivery unit such as heat exchanger. The simulation model of heat and mass transfer processes in the solar field as well as the balance of the system is developed to investigate the technological feasibility of the concept in terms of plant yield and matching of subsystems.

Development of advanced solar assisted drying systems

The Solar Energy Research Group in the Universiti Kebangsaan Malaysia has been set-up more than two decades ago. One of the activities is in the field of solar thermal process, particularly in development of solar assisted drying systems. Solar drying systems technical development can proceed in two directions. Firstly simple, low power, short life, and comparatively low efficiency-drying system. Secondly, the development of high efficiency, high power, long life expensive solar drying system. The group has developed four solar assisted drying systems namely (a) the V-groove solar collector, (b) the double-pass solar collector with integrated storage system, (c) the solar assisted dehumidification system for medicinal herbs and (d) the photovoltaic thermal (PVT) collector system. The common problems associated with the intermittent nature of solar radiation and the low intensities of solar radiation in solar thermal systems can be remedied using these types of solar drying systems. These drying systems have the advantages of heat storage, auxiliary energy source, integrated structure control system and can be use for a wide range of agricultural produce.

Profiles of PAH emission from steel and iron industries.

In order to characterize the polycyclic aromatic hydrocarbons (PAHs) emission from steel and iron industries, this study measured the stack emission of twelve steel and iron plants in southern Taiwan to construct a set of source fingerprints. The study sampled the emissions by the USEPA's sampling method 5 with the modification of Graseby for the gas and particulate phase PAH and, then, used Hewlett-Packard 5890 gas chromatograph equipped with mass spectrometer detector to analyze the samples. The steel and iron industries are classified into three categories on the basis of auxiliary energy source: Category I uses coal as fuel, Category II uses heavy oil as fuel and Category III uses electric arc furnace. The pollution source profiles are obtained by averaging the ratios of individual PAH concentrations to the total concentration of 21 PAHs and total particulate matter measured in this study. Results of the study show that low molecular weight PAHs are predominant in gas plus particulate phase for all three categories. For particulate phase PAHs, however, the contribution of large molecular weight compounds increases. Two-ring PAHs account for the majority of the mass, varying from 84% to 92% with an average of 89%. The mass fractions of 3-, 4-, 5-, 6-ring PAHs in Category I are found to be more than those of the other two categories. The mass of Category III is dominated by 7-ring PAHs. Large (or heavy) molecular weight PAHs (HMW PAHs) are carcinogenic. Over all categories, these compounds are less than 1% of the total-PAH mass on the average. The indicatory PAHs are benz[a]anthracene, benzo[k]fluoranthene, benzo[ghi]perylene for Category I, benzo[a]pyrene, acenaphthene, acenaphthylene for Category II and coronene, pyrene, benzo[b]chrycene for Category III. The indicatory PAHs among categories are very different. Thus, dividing steel and iron industry into categories by auxiliary fuel is to increase the precision of estimation by a receptor model. Average total-PAH emission factors for coal, heavy oil and electric arc furnace were 4050 microg/kg-coal, 5750 microg/l-oil, 2620 microg/kW h, respectively. Carcinogenic benzo[a]pyrene for gas plus particulate phase was 2.0 g/kg-coal, 2.4 microg/l-oil and 1.4 microg/kW h for Category I, II and III, respectively.

The performance of a box-type solar cooker with auxiliary heating

In Bangladesh it is very difficult to use solar cookers during the months when the days are generally cloudy and at times solar cooking becomes impossible. To overcome such problems for a box-type solar cooker, we have used an auxiliary source of energy inside it. This is done with the help of a built-in heating coil inside the cooker or a retrofit electric bulb in a black painted cylinder. It is found that the use of auxiliary sources allows cooking on most cloudy days.

Simulation studies of the position of the auxiliary heater in thermosyphon solar water heating systems

This paper investigates the effect of the physical location of the auxiliary source of energy in thermosyphon solar water heaters and shows that the performance of the system can be optimised with respect to the geometry of the system components. The investigation has been based on a domestic thermosyphon solar water heating system, which was simulated using the TRNSYS programme. The annual solar fraction of the system, at the weather and socioeconomic conditions of Cyprus, is, at best, approximately 77% with an in-tank auxiliary heater configuration and 86% with an external auxiliary heater. It is demonstrated that the arrangement with the external auxiliary unit has a higher collector efficiency and results in a higher annual solar fraction. In the case of in-tank auxiliary, the system performance increases with the height of the auxiliary position from the bottom of the storage tank; with the auxiliary at the bottom of the storage tank the annual solar fraction is approximately 59%, compared to 77% when the auxiliary is located at the top of the tank. The system performance also depends on the height of the collector return from the bottom of the tank.

Growth rate-dependent expression of phenol-assimilation pathways in Alcaligenes eutrophus JMP 134-the influence of formate as an auxiliary energy source on phenol conversion characteristics

Alcaligenes eutrophus JMP 134 was continuously (carbon-source-limited) grown on phenol to determine the maximum growth rates (μmax) as a function of the phenol assimilation pathways expressed. During growth on phenol as the sole source of carbon and energy, an almost exclusive expression of the ortho cleavage pathway (catechol 1,2-dioxygenase) was observed at initially low growth rates. This allowed a μmax of 0.28 h-1. The induction of the meta cleavage pathway (catechol 2,3-dioxygenase), which appeared at around 0.25 h-1, resulted in a further increase in the growth rate to 0.40 h-1 after the enzyme activities of this pathway had been correspondingly expressed. Hence, two maximum growth rates, one for the ortho and one for the meta cleavage pathway, exist for the growth of A. eutrophus JMP 134 on phenol. Growth on phenol was stimulated by formate, which served as an auxiliary energy source in this strain. The simultaneous utilization of phenol and formate at a molar ratio of 1:5.2 resulted in an increase of the yield coefficient from about 0.75 g dry mass/g phenol to 1.25 g/g. Furthermore, formate exerted a pronounced effect on the growth rate. At a molar ratio of phenol to formate of 1:4.2, the growth rate was increased to 0.42 h-1, despite the exclusive induction of the ortho cleavage pathway. The meta cleavage pathway was expressed during growth on this substrate mixture at about 0.4 h-1. However, this did not enable a significant increase of the growth rate beyond 0.4 h-1. This is attributed to an exhaustion of the capacity for formate oxidation at this rate. The results are discussed with respect to energy production capabilities when phenol is assimilated as an energy-deficient heterotrophic substrate.

Low energy gain from formate oxidation during bacterial growth on 2,4‐dichlorophenoxyacetic acid

AbstractAlcaligenes eutrophus JMP 134 was chemostatically grown on 2,4‐dichlorophenoxyacetic acid (2,4‐D) at a dilution rate of 0.06 h−1; formate was fed as an auxiliary energy source. The simultaneous utilization of both components resulted in an increase in growth yield. As an example, this figure increased from 0.18 g dry mass/g 2,4‐D to 0.25 g dry mass/g 2,4‐D during growth on 1 g/l 2,4‐D plus 3 g/l sodium formate. The increase was correlated to energy generated from formate oxidation. Accordingly, a P/O‐quotient of 1 was derived for the energy transduction of NADH obtained from formate oxidation as it was for the overall efficiency during growth on 2,4‐D itself. This low energy yield was attributed to uncoupling exerted by 2,4‐D. The theoretical maximum yield coefficient of 0.69 g/g could not be reached due to the limiting activity of formate dehydrogenase in the conversion of the required quantities of formate.

Experimental and theoretical discrepancies in growth yields of Acinetobacter calcoaceticus: a correction of published data

Acinetobacter calcoaceticus can incompletely oxidize aldose sugars to the corresponding aldonic acids. This reaction can serve as an auxiliary energy source for the organism. An increase in biomass yields is observed in acetate-limited chemostat cultures grown in the presence of, for example, xylose. However, experimental and theoretical discrepancies exist with respect to the magnitude of the yield enhancement as a result of xylose addition. We previously observed increases in cell yields that were unexpectedly high. In contrast, other data were in agreement with the theoretical predictions. In this paper, evidence is presented indicating that this discrepancy is likely to be due to errors in the methodology used for our previous investigation, in particular with respect to the determination of biomass concentrations.

Pulsed laser deposition of amorphous diamond-like carbon films with ArF (193 nm) excimer laser

We have deposited hydrogen-free diamond-like amorphous carbon films by ArF (193 nm) pulsed laser ablation of graphite. The deposition process is performed with a laser power density of only 5 × 108 W/cm2 at room temperature without any auxiliary energy source incorporation. The resulting films possess remarkable physical, optical, and mechanical properties that are close to those of diamond and distinct from the graphite target used. The films have a mechanical hardness up to 38 GPa, an optical energy band gap of 2.6 eV, and excellent thermal stability. Analysis of electron energy loss spectroscopy reveals the domination of diamond-type tetrahedral bonding structure in the films with the sp3 bond fraction over 95%. Compared with other reported results of pulsed-laser-deposited diamond-like carbon films, our experimental results confirm that the laser wavelength or photon energy plays a crucial role in controlling the properties of the pulsed-laser-deposited diamond-like carbon films.

Techno-economic optimization of a hybrid collector-cum-storage system

A mathematical model is presented for studying the techno-economic performance of a hybrid solar air heating system. The configuration of the system consists of a collector-cum-storage system for solar heating of air, an adjuster unit for bringing down the higher air temperature to the desired limit by mixing fresh air in it, and an auxiliary energy source to provide the deficient amount of heat to the air to attain the desired temperature whenever required. In order to evaluate the performance of the system, numerical calculations have been made corresponding to the climatic data of Delhi and the cost parameters prevalent in the Indian market. Numerical results show that the cost of the useful energy obtained for optimized values of collector area and water-depth is much less than the cost of electrical heating.

Biochemical limits to microbial growth yields: An analysis of mixed substrate utilization

A theoretical analysis has been made of carbon conversion efficiency during heterotrophic microbial growth. The expectation was that the maximal growth yield occurs when all the substrate is assimilated and the net flow of carbon through dissimilation is zero. This, however, is not identical to a 100% carbon conversion, since assimilatory pathways lead to a net production of CO(2). It can be shown that the amount of CO(2) produced by way of assimilatory processes is dependent upon the nature of the carbon source, but independent of its degree of reduction and varies between 12 and 29% of the substrate carbon. An analysis of published yield data reveals that nearly complete assimilation can occur during growth on substrates with a high energy content. This holds for substrates with a heat of combustion of ca. 550 kJ/mol C, or a degree of reduction higher than 5 (e.g. ethane, ethanol, and methanol). Complete assimilation can also be achieved on substrates with a lower energy content, provided that an auxiliary energy source is present that cannot be used as a carbon source. This is evident from the cell yields reported for Candida utilis grown on glucose plus formate and for Thiobacillus versutus grown on acetate plus thiosulfate. This evaluation of the carbon conversion efficiency during assimilation also made it possible to compare the energy content of the auxiliary energy substrate added with the quantity of the carbon source it had replaced. It will be shown that utilization of the auxiliary energy source may lead to extreme changes in the efficiency of dissimilatory processes.

Exergy analysis of solar-assisted heat pump systems

The purpose of this study is to perform a second law analysis via a computer simulation of a solar-assisted heat pump system. Results are obtained for typical days during each month of December. January, February and March for Istanbul (41° N). During the analysis, five different solar collector areas are used for both the solar-assisted heat pump system and the solar collector system. Eleven different systems are examined and the results are compared. The conventional boiler is used as an auxiliary energy source for all of the systems. The exergetic efficiency or second law efficiency is defined, formulated and deduced for each of the systems. The exergetic efficiencies are calculated and comparisons are performed among the different systems.

Choice of thermal energy system for solar absorption cooling

It is essential to operate a solar vapour absorption cooling system only at design conditionsin order to maximize the saving of conventional electrical energy. The paper deals with the analysis of a solar thermal energy system by coupling the collector field, an auxiliary thermal energy source, the thermal energy reservoir and the generator of the absorption chiller in a single closed loop, thus ensuring optimum performance of the chiller at design conditions. This analysis is preceded by a quasi steady-state analysis for the system without the auxiliary source to obtain the temperature history of the reservoir, the hourly thermal energy availability and the resulting cooling effect. The comparative results of the two systems highlight the importance of auxiliary thermal energy source in mximizing the electrical energy saving. The utility of auxiliary energy input is highly attractive because of its high effective COP and higher equivalent electrical conversion efficiency.