Auxiliary Energy Source Research Articles

HYBRID SYSTEM SIMULATION TO SUPPLY HEATED AIR TO A SOLAR FOOD DRYER

The intermittence of solar radiation, due to continuous rainy or cloudy days, is a limitation of simple and small solar dryers. These conditions often make them impossible to use. By including storage systems (thermal accumulation) and/or auxiliary energy sources, drying processes or dehydration can be conducted continuously, even during periods of low insolation. Therefore, the present work simulates and evaluates the thermal and energetic behavior of a hybrid system for heating the air that is directed to the dehydration chamber of a solar food dryer. The software selected for the simulation was TRNSYS. The simulated hybrid system consists of a flat plate solar collector and an arrangement of electrical resistors that guarantee the entry of air, at a constant temperature, into the dehydration chamber. The target temperature selected is 70 oC, and the absence of food products in the chamber is assumed. An arrangement with four electric resistors totaling 1900 W, with three different powers of 1000 W, 500 W, and 200 W proved adequate to guarantee the entrance of air at a constant temperature when considering the climatic conditions of a city in the South of Brazil.

Thermoelectric Energy Storage Using Auxiliary Solar Thermal and Geothermal Energy

Abstract Multi-megawatt thermoelectric energy storage (TEES) based on thermodynamic cycles is a promising alternative to pumped-storage hydroelectricity (PSH) and compressed air energy storage (CAES) systems. The size and cost of energy storage are the main advantages of this technology as it generally uses inexpensive energy storage materials and does not require high-pressure tanks or rare geographic terrain, but the round trip electric efficiency of this technology remains low compared to its competitors. In this context, the objective of this article is to study and simulate a TEES system. A TEES system converts electrical energy to thermal energy by means of an electric heater uses joule heating effect, the system storage this thermal energy in solar salt. Stored thermal energy is converted into electrical energy by a thermal engine uses the organic Rankine cycle (ORC). An auxiliary energy source is integrated with the organic Rankine cycle to improve the round trip electric efficiency of the system. Auxiliary energy source can be solar thermal and geothermal at an average temperature between 100 and 140 °C, which is used to evaporate the working fluid to saturation. The steam is then superheated by stored thermal energy. The superheated steam expands in a turbine producing a good amount of energy compared to the saturated steam expansion. Methanol (CH3OH) has been used as a working fluid because its boiling point is less than 100 °C at the atmospheric pressure.

ANFIS-Based Control of Multi-objective Grid Connected Inverter and Energy Management

As a consequence of fast socio-economic progress, the requirement of auxiliary energy sources is creating new opportunities in the field of renewable energy sources (RES). This paper presents a hybrid photovoltaic (PV)–fuel cell (FC) energy structure for grid-connected applications. The key challenges associated with the integration of RES are managing harmonic distortions, voltage fluctuations and power sharing. To mitigate these problems and to enhance the overall performance of the system, multi-objective inverter based on hybrid intelligent controller, adaptive neuro-fuzzy inference system has been designed. In the proposed system, PV acts as a primary energy source, while FC serves as a secondary energy source. An overall power management strategy has been designed to manage power flows among the RES, load and grid. The effectiveness of the proposed multi-objective inverter control and energy management of the system is validated under MATLAB/Simulink platform.

A numerical study on the thermal performance of prismatic li-ion batteries for hibrid electric aircraft

The increase of greenhouse gas emissions and environmental pollution leading to global warming have made it necessary for measures to be taken to increase the production and usage of electric vehicles. Instead of fossil fuels, these vehicles, which are powered by electricity from sustainable sources, promise hope for global warming through zero emissions. Batteries for electric aircraft are in important position. In these vehicles, the primary energy source or primary auxiliary energy source is high-density batteries. Temperature is one of the most important factors impressive battery performance as it shortens battery life. Lithium ion batteries are the preferred battery in this study because they have a high specific energy and energy density. This study examined the performance of the heat generated by 10 prismatic batteries. These batteries were connected to each other in series. The cathode of the batteries is LiMn2O4. A three-dimensional thermal analysis was performed under natural and forced transport conditions. The temperature of the batteries rises in the middle of the battery module and an uneven temperature distribution was observed under natural convection. Because of the heat transfer from each battery’s surface, both a decrease in temperature was observed and a balanced temperature distribution happened under forced convections. As the C ratio decreased, the temperature of the batteries decreased, but this process requires a longer time. For this reason, C values should be selected according to the battery capacity and working environment.

Starting-up strategies for solar thermal fields attending to time and economic criteria: Application of hierarchical control

Solar thermal fields are usually coupled to storage tanks to improve the energy dispatchability. In direct configuration and without an auxiliary energy source, the state of the storage tank at the beginning of the operation is very relevant. If the storage device is stratified or discharged in terms of energy, the start-up phase until reaching the desired operating point can take a long time and reduce the benefits. Consequently, this paper presents a two-layer hierarchical controller aimed at reducing the costs and time spent in this operating phase. The upper layer is based on a Nonlinear Model Predictive Control (NMPC) strategy, and the lower one is composed of Proportional Integral Derivative (PID) controllers. The proposed technique was applied to a real facility located at Plataforma Solar de Almería (southest of Spain). Moreover, a comparative simulation study with manual and previous approaches proposed in literature was performed to evidence the important economic and time savings achieved by the application of the developed technique.

Research on multi-energy management system of fuel cell vehicle based on fuzzy control

This paper studies a hybrid power system composed of fuel cells, super capacitors and batteries. Super capacitors are used as auxiliary energy sources to provide the required high power when the car starts and accelerate, while absorbing braking energy when the car is braking. Fuzzy control is used to optimize its energy management strategy. The fuzzy controller of the three-energy source system takes the battery, super capacitor, and bus demand power as the input of the fuzzy controller, and the battery demand power and the fuel cell demand power as the fuzzy controller output. The system realizes the energy distribution of super capacitors, fuel cells and storage batteries according to power requirements, thereby improving the performance of the system and extending the life of components. And with hydrogen consumption as the optimization goal, the particle swarm algorithm is used to optimize the parameters of the fuzzy membership function. Compared with the fuzzy control strategy without particle swarm optimization, the optimized fuzzy energy management strategy reduces the hydrogen consumption of fuel cell vehicles. 10 L/(100 km)-1, which improves the economy of the vehicle.

Optimal design and sensitivity analysis of a PV-WT-hydraulic storage system generation in a remote area in Tunisia

ABSTRACT One of the major problems of renewable systems e.g. photovoltaic systems (PV) and Wind Turbine systems (WT) is the intermittence of their productions. Problems caused by the intermittency of these systems can be reduced by the insertion of an auxiliary energy source e.g. fuel cells, electrochemical storage, hydraulic energy storage system. Electrochemical storage is the most used solution but it suffers from several problems e.g. deep discharges, cost, cycles, oxidation, etc. To avoid these problems caused by this type of storage system, this paper proposes and analyzes the efficiency of the replacement of electrochemical storage by a hydraulic energy storage system by performing two Integrated Optimal Design (IOD) followed by a sensitivity analysis versus environmental data changes. This hydraulic system is associated to a renewable energy system WT/PV installed in the Thermal Processes Laboratory in Research and Technology Center of Energy (CRTEn) in Borj Cedria (a typical remote area very close to the sea). The global PV-WT-Hydraulic storage system optimal sizing is needed in order to ensure continuity and reliability of electricity supply of this specific remote area.

Simple and Efficient Green Extraction of Steviol Glycosides from Stevia rebaudiana Leaves.

The food industry has currently shown great interest in alternative sweeteners to sugars with the aim of producing healthier products. In light of this, steviol glycosides are natural low-caloric sweeteners present in Stevia rebaudiana, which have additionally been described as bioactive components with potential therapeutic properties. In this work, a green method for the extraction of steviol glycosides from stevia leaves was optimized by applying a factorial screening design of five variables (time, temperature, agitation, grinding, and sample–solvent ratio) and the subsequent response surface design of Box-Behnken. The optimized extraction method allows for the recovery of stevia sweeteners in a simple and efficient manner by using tap water as the extractant, without the application of an auxiliary energy source to reduce costs, thus representing an interesting strategy for their industrial-scale production.

HYDROELECTRIC ROAD RAMP

Purpose. The purpose of the study was to elaborate on a renewable source of energy using daily vehicles' traffic. The research question was how to produce electricity by using vehicle's kinetic energy and water-contained energy. In this paper «hydroelectric road ramp» is described as an auxiliary energy source which can be used in smart cities. Methodology. By conducting the literature review of adjacent methods and existing inventions, combining principles of work of these inventions, the system for producing electricity without destroying nature has been designed. Findings. Based on the supposition that 200 vehicles per hour pass over a ramp, the findings show that power generated by the system equals to 405,34 W. Considering the fact, that city roads function around the clock we can multiply the obtained result by 24 hours. Thus, we can accumulate a lot of electricity for efficient using in necessary goals. Even considering the fact that road capacity is different hour by hour, there is an opportunity to generate enough electricity for its conservation and further usage. Originality. From one side ‘hydroelectric road ramp’ is the system of generating electricity by using principles of work of conventional hydroelectric power station and pneumatic water sprayer, from the other side it is a speed breaker which may improve the safety conditions on the road. Practical value. The calculations we obtained led us to the theoretical conclusion that electricity getting from new source can be effectively used in the 'smart city' such as: powering street lights, traffic lights or serve as a complementary source of energy for e-mobiles charging points.

A real‐time experimental investigation of building integrated thermal energy storage with air‐conditioning system for indoor temperature regulation

AbstractIn this article, a novel concept of the latent heat thermal energy storage system combined with the conventional cooling system is proposed for the application of indoor thermal comfort. Lauryl alcohol with a melting point of 22‐25°C is selected as phase change materials (PCM) for the study. From the results of experiment conducted with different mass of PCM, there is no change in temperature drop achieved while increasing PCM mass but there is increase in discharge time. The average air temperature in bottom chamber is maintained at 26°C which is in thermal comfort range throughout the experiment. For the experiments with different inlet air temperatures, higher drop in top chamber outlet air temperature is achieved for higher inlet temperatures. The temperature of the room can bring down to human thermal comfort range with a minimum duration of time with the proposed system irrespective of initial room temperature. The proposed system helps to maintain the buildings in human thermal comfort range with less‐energy consumption when the conventional air‐conditioning system is not in operation which in turn decreases the major energy consumption by the building sector through other auxiliary energy source.

Systems design and analysis of liquid air energy storage from liquefied natural gas cold energy

The cold recovery of liquefied natural gas (LNG) is an important issue and power generation is widely recognized as a potential option. However, the amount of generated power from LNG regasification is relatively small for use as a primary energy source to the energy grid. Therefore, using recovered LNG cold energy as an auxiliary energy source for the energy grid can be more appropriate than directly supplying power to the energy grid. By applying an energy storage system to the LNG regasification process, the recovered energy can be flexibly released to the energy grid when required. Among various energy storage technologies, liquid air energy storage (LAES) is one of the most promising large-scale energy storage systems. This study proposes a combined LAES and LNG regasification process. In this system, the air is cooled via heat exchange with LNG and compressed by using the generated power from LNG. This power is produced by both direct and indirect methods: LNG direct expansion and organic Rankine cycle with a mixed working fluid, respectively. This is a novel work in which both direct and indirect power generation methods to the LNG regasification process are combined with the energy storage system. According to the performance comparisons amongst various energy storage systems combined with the LNG regasification process, this proposed system is the most efficient proposed in the literature. Moreover, economic evaluation is performed using a net present value to investigate the feasibility of the proposed system.

A New Formula for Hydrogen Consumption in Hybrid Systems Based on Fuel Cell Current Gradient and Peak Value

DOI : 10.26650/electrica.2019.18013 In the study, we proposed a new formula for the hydrogen consumption of fuel cell under non-constant current behavior. We used supercapacitors as auxiliary energy source to form a hybrid system and change the current behavior of the fuel cell. We performed hybrid system tests for different supercapacitor values. We extracted the fuel cell current, voltage, hydrogen consumption for each configuration. We compared the measured values and expected values from known equations. We see that, results from hydrogen consumption equations does not match the hybrid system hydrogen consumption. Finally, we proposed a new formula for hydrogen consumption including the current gradient and current peak value for hybrid systems. Cite this article as: Ozcelep Y, Sari G, Kuntman A. A New Formula for Hydrogen Consumption in Hybrid Systems Based on Fuel Cell Current Gradient and Peak Value. Electrica, 2019; 19(1): 59-64.

Effective mitigation of the load pulses by controlling the battery/SMES hybrid energy storage system

In this paper it is analyzed the behavior of a battery/Superconducting Magnetic Energy Storage (SMES) hybrid Energy Storage Systems that can be used in a Fuel Cell/Renewable Energy Sources (RESs)/Hybrid Power System under an unknown load profile and variable RES power, which uses the Fuel Cell System as Auxiliary Energy Source. In general, the load demand profile includes large and sharp pulses, especially requested for space and military equipment, communication, and high-tech applications. The sizing and control of the battery/SMES Hybrid Power System under pulsed load are validated by simulations. The variability of the load demand and RES power is mitigated by using the Load-Following control for Auxiliary Energy Source of the RES Hybrid Power System. Thus, if the load power is higher than the RES power, then the battery will operate in charge-sustaining mode due to using the Load-Following control for Auxiliary Energy Source. Otherwise, the battery will operate in charge-increasing mode if the Hybrid Power System does not use an electrolyzer to be supplied with this excess of power. So, a reduced capacity is needed for battery operating in charge-sustaining mode due to use of the Load-Following control. However, the load pulses with large and sharp profile must be mitigated by the appropriate control of the SMES in order to protect the Fuel Cell system. So, the capacity of the SMES to generate (or to absorb) such pulses is analyzed in this paper. The simulation results illustrate the capacity of the SMES to generate different shapes of pulses. Thus, an effective mitigation of the load pulses is proposed here by controlling the SMES converter. Also, the design of the battery/SMES Hybrid Power System under dynamic load is presented.

Switching sliding-mode control strategy based on multi-type restrictive condition for voltage control of buck converter in auxiliary energy source

In this paper, a switching sliding-mode control strategy is proposed for the voltage control of a buck converter in auxiliary energy source. The aim of this study is to solve the singularity problem of the terminal sliding-mode control strategy and simplify the implementation of the exponential operation of the non-singular terminal sliding-mode control strategy in practical applications. To achieve this goal, the state-space model of the buck converter in the auxiliary energy source is established. Furthermore, a novel switching sliding surface is defined based on the non-singular terminal sliding-mode control strategy. To ensure the stability of the switching sliding-mode control system, a multi-type restrictive condition, including non-singular type and reachable type, is designed based on equivalent control law and Lyapunov stability criterion, respectively. Simulations and experiments are presented to verify the effectiveness of the proposed switching sliding-mode control strategy. The results show that both the non-singular terminal sliding-mode control and the switching sliding-mode control can effectively solve the singularity problem. Compared with the terminal sliding-mode control strategy, the non-singular terminal sliding-mode control and the switching sliding-mode control strategies have over 18% and 34.4% settling-time improvement of voltage adjustment to deal with the large load variation, respectively. The proposed switching sliding-mode control strategy can not only ensure the robust voltage control of the buck converter in the auxiliary energy source, but also simplify the implementation of exponential circuit in practical applications.

Switching control strategy based on non-singular terminal sliding mode for buck converter in auxiliary energy source

This paper proposes a switching control strategy for voltage control of buck converter in auxiliary energy source. The state-space average model of the buck converter is established. Then, the non-singular terminal sliding mode control (NTSMC)strategy is described. Furthermore, the switching sliding surface based on NTSMC is developed to achieve single-phase output, which can simplify the exponential operation of the NTSMC. The system stability is proved by the Lyapunov stability criterion. Simulation model with the proposed control strategy and conventional sliding mode control (CSMC) strategies are established. Compared with CSMC, the proposed strategy has a better stability and dynamic response.

Investigation of Effect of Biomass Torrefaction Temperature on Volatile Energy Recovery Through Combustion

Biomass torrefaction is a mild pyrolysis thermal treatment process carried out at temperatures between 200 and 300 °C under inert conditions to improve fuel properties of parent biomass. Torrefaction yields a higher energy per unit mass product but releases noncondensable and condensable gases, signifying energy and mass losses. The condensable gases (volatiles) can result in tar formation on condensing, hence, system blockage. Fortunately, the hydrocarbon composition of volatiles represents a possible auxiliary energy source for feedstock drying and/or torrefaction process. The present study designed a low-pressure volatile burner for torrefaction of pine wood chips and investigated energy recovery from volatiles through clean co-combustion with natural gas (NG). The research studied the effects of torrefaction pretreatment temperatures on the amount of energy recovered for various combustion air flow rates. For all test conditions, blue flames and low emissions at the combustor exit consistently signified clean and complete premixed combustion. Torrefaction temperature at 283–292 °C had relatively low volatile energy recovery, mainly attributed to higher moisture content evolution and low molecular weight of volatiles evolved. At the lowest torrefaction pretreatment temperature, small amount of volatiles was generated with more energy recovered. Energy conservation evaluation on the torrefaction reactor indicated that about 27% of total energy carried by the exiting volatiles and gases has been recovered by the co-fire of NG and volatiles at the lowest temperature, while around 19% of the total energy was recovered at the intermediate and highest torrefaction temperatures, respectively. The energy recovered represents about 23–45% of the energy associated with NG combustion in the internal burner of the torrefaction reactor, signifying that the volatiles energy can supplement significant amount of the energy required for torrefaction.

The Impact of Reservoir Heterogeneities on High-Temperature Aquifer Thermal Energy Storage Systems. A Case Study from Northern Oman.

We conducted a geoscientific feasibility study for the development of a high-temperature thermal aquifer energy storage system (HT-ATES) outside the capital of Muscat, northern Oman. The aquifer storage is part of a solar-geothermal cooling project for the sustainable and continuous cooling of office buildings. The main concept is that excess solar energy will be stored in the subsurface through hot water injection and subsequently utilised as auxiliary energy source during peak demand times. The characterisation of aquifer heterogeneities is thus essential to predict subsurface thermal heat plume development and recovery efficiency of the storage system. We considered two aquifer systems as potential storage horizons, (i) a clastic-dominated alluvial fan system where individual channel systems in combination with diagenetic alterations constitute the main heterogeneities and (ii) a carbonate-dominated system represented by a homogenous layer-cake architecture. The feasibility study included a multidisciplinary approach from initial field work, geocellular reservoir modelling to finite element fluid flow and thermal modelling. Our results show that for the HT-ATES system, with a high frequency of injection and production cycles, heat loss mainly occurs due to heterogeneities in the permeability field of the aquifer in combination with buoyancy driven vertical fluid flow. An impermeable cap-rock is needed to keep the heat plume in place. Conductive heat loss is a minor issue. Highly complex heat plume geometries are apparent in the clastic channel system and ATES well planning is challenging due to the complex and interconnected high-permeable channels. The carbonate sequence shows uniform plume geometries due to the layer cake architecture of the system and is tentatively more suitable for ATES development. Based on our findings we propose the general concept of HT-ATES traps, incorporating and building on expertise and knowledge from petroleum and reservoir geology regarding reservoir rocks and suitable trap&seal geometries. The concept can be used as guideline for future high-temperature aquifer storage exploration and development.

Trimode Smart Charging and Real Vehicle Characteristics Investigation for Solar-electric Vehicles

Because of the increasingly serious problems of environmental pollution and non-renewable energy shortage, in recent years, the world has been vigorously developing new energy vehicles, especially electric vehicles. Electric vehicles with solar energy as an auxiliary energy source can reduce the demand for power generation and charging stations for excessive electric vehicles during peak hours. In the present study, a solar electric vehicle was built, in which batteries and solar panel jointly provided power for car operations. In order to ensure that the electricity of solar panel can be safely and continuously supplied to the motor, this paper designed an intelligent charging controller with three work mode to connect the solar panel and batteries. Through reasonable charging strategy, this technology can maximize the use of solar energy, and ensure the safety and service life of the battery. Real vehicle test results show that the solar intelligent charging technology has obvious effect on the expansion of vehicle endurance, and also show that the integration of solar panel into the body design is an effective means to deal with the energy crisis in the future.

Area optimization of solar collectors for adsorption desalination

Adsorption desalination is an emerging method to address the shortage of fresh water. To achieve its energy-saving potentials, a renewable low-temperature heat source is the key. This paper focuses on the area optimization of solar collectors in combined solar heating systems that supply heat for adsorption desalination, aiming at achieving the maximum economic benefits during the lifespan of a project. The optimum tilt angle was discussed and the corresponding daily radiation data were calculated with HDKR (Hay, Davies, Klucher, Reindl) model. The area optimization function was proposed with the unit costs of fresh water as the optimization objective. A reference area calculated according to annual solar radiation was employed to describe the optimization results. Then the influences of the price of auxiliary energy sources, the performance ratio of adsorption desalination, and the heat loss of solar heating on the optimization results were studied with an actual adsorption desalination project in Tianjin. It has been found that the optimal area is positively associated with the auxiliary energy price, however approximately inversely proportional to the performance ratio of desalination and the energy efficiency of solar heating. The unit costs of producing fresh water can be reduced up to 20% after collector area optimization when the auxiliary energy is expensive. Besides, the overall costs of utilizing solar heating to supply heat for adsorption desalination is around 0.03–0.04 CNY/MJ which is lower than conventional energy sources. We also tested the optimization results with an altered precision of radiation data and different meteorological conditions. Findings in this paper proved the advantages of incorporating solar heating in adsorption desalination and provided instructions for designing solar adsorption desalination projects.

Techno-economic analysis of an integrated collector storage solar water heater with CPC reflector for households

ABSTRACTFew countries bank on solar water heating systems (SWHS) to meet their domestic hot water needs, and instead prefer to use fuel or electric/gas geysers. The reason is the former having relatively high initial investment and performance marred by poor maintenance, and the latter having low initial cost. In this light, we need to compare the economic feasibility of an SWHS with the other alternatives. In almost all solar energy systems, the annual loads are met by a combination of solar and non-solar alternatives, i.e. auxiliary or conventional energy source. Several economic criteria have been proposed and used for evaluating and optimising solar energy systems. The authors have made use of EES software to obtain the economic figures of merit. The proposed model has low initial cost and better long-time thermal performance estimates. The annual solar fraction for the model is 0.55 and the payback period is two years.