Single Tank System Research Articles

A hardware/software architecture dedicated to model predictive control law and implemented into an FPGA platform

Model predictive control (MPC) is an optimisation-based strategy for high-performance control engineering practice and real-time applications. This method needs to solve online a quadratic programming (QP) problem at each sample time to find optimal control sequence. In this paper, a new optimised MPC architecture is presented, for a gradient-based QP solver to implement linear MPC on a field-programmable gate array platform, which allows obtaining high-quality performances for the real-time control applications. It requires a manual programming of the high-level C/C ++ code in opposition to the other presented approaches, which automatically generates the code. The efficiency of this approach is completed with real time control of the water level of a single tank system running on a Nanoboard 3000XN chip using a conception environment (Altium Designer), while comparing between the MPC and PID controllers.

Studies on Closed-loop Interaction in a Multi-loop Single Tank Control System

This paper investigates the interaction between level and flow loop in a single tank system. The data generated is used to generate all transfer functions via step test method. The model generated is then simulated on MATLAB-Simulink and the obtained results are then compared with experimental results for verification. A Relative Gain Array analysis is performed to check the interaction and comment on the pairing.

Determining the optimal cultivation strategy for microalgae for biodiesel production using flow cytometric monitoring and mathematical modeling

Trade-off between growth and lipid accumulation is one of the main issues in cultivation of microalgae for biodiesel production. Advantages of two-phase cultivation systems, with growth and lipid accumulation occurring in separate tanks, have been proposed. However, because the two-phase cultivation system requires more cultivation space and complex operation procedures compared to a single tank system, its advantage for lipid production is still uncertain. Furthermore, previous studies have not explicitly determined an optimal cultivation schedule, defining timing of the transfer of cells to the second tank and harvesting in the second tank. We therefore developed a model for lipid accumulation in the microalgae Chlorella sorokiniana to compare theoretical maxima of lipid productivity in single- and two-tank cultivation systems. We first established a monitoring method of growth and lipid accumulation using a flow cytometer, and then modeled the data by a logistic equation to derive a model for lipid accumulation. This model was used to theoretically optimize cultivation methods and harvest times to maximize lipid productivity in four different cultivation systems: single- or two-tank setups, with batch or fed-batch cultures, respectively. Results theoretically demonstrated that a two-phase cultivation system is slightly more productive than a single-tank one. The mathematical model analysis indicates strategies for further improving the productivity of each cultivation system without any additional investments in cultivation systems (i.e., nutrient, light, CO2). Our model analysis approach provides a theoretical basis for determining an optimal cultivation strategy of microalgae and identifies experimental data helpful for further improvement of cultivation systems.

A novel algorithm for real-time framework in multiprocessor environment

The objective of the paper is to represent the real-time framework in multiprocessor environment task scheduling process by examining the novel algorithm advanced PSO. The advanced PSO algorithm has the metaphor as the basis to facilitate social interaction, which makes a search on space by making adjustments to the trajectories of individual vectors, referred to "particles" as they are considered as the points that move within the multidimensional search space. This algorithm will reduce the turn-around time, burst time and waiting time for multiprocessor task scheduling, when compared to existing algorithm like first come first served algorithm, shortest job first algorithm and round robin scheduling algorithm. This proposed algorithm is developed and making hardware for tank level water control for single input single output tank system and two input two output tank system. LABVIEW software is used to implement the real-time algorithm in hardware and software. The time taken for searching best position for particles will be executed and compare with all algorithms using bar chart will be given in result.

Fuel Flow Topology and Control for Extending Aircraft Thermal Endurance

The effect of fuel flow topology and control on the thermal endurance of aircraft that use fuel as a heat sink was explored. Differential equations were derived that describe the behavior of recirculated fuel flows within a proposed dual-tank topology that features a designated recirculation tank. Equations for single-tank flow topology are also presented. It is shown that a simple switching controller acting on a dual-tank system results in aircraft thermal endurance that is greater than or equal to that of a single-tank configuration when the aircraft engine and fuel system are driven at a constant mass flow rate. More sophisticated examples are considered for a fighter aircraft mission where the endurance achieved by both open- and closed-loop single-tank systems are compared to the endurance of a dual-tank system operating under closed-loop control. Simulation results are used to quantify benefits that can be obtained by a judicious selection of closed-loop control strategy and fuel flow topology. The results show that a controlled dual-tank fuel topology can increase aircraft thermal endurance over that which can be attained by a single-tank fuel flow topology.

Tuning of optimal P and PI controllers for level control of single tank system

Tuning of optimal P and PI controllers for level control of single tank system

Comparison of Tuning Methods of PID Controllers for Level Process for Single Tank System

Comparison of Tuning Methods of PID Controllers for Level Process for Single Tank System

Coagulation/flocculation of lignin aqueous solution in single stage mixing tank system: Modeling and optimization by response surface methodology

Lignin particles contribute to color pollution in river water and treating this type of pollution biologically is difficult. In this study, the treatment of a model solution containing lignin using a single mixing tank system approach with poly-diallyldimethyl ammonium chloride (polyDADMAC) as destabilizer was carried out. The effect of various flocculants i.e., calcium lactate, magnesium hydroxide and anionic polyacrylamide (APAM) were investigated. Calcium lactate performed better than magnesium hydroxide and anionic polyacrylamide as flocculants. The coagulation/flocculation with polyDADMAC–calcium lactate removed lignin through a complex mechanism: the adsorptive-charge neutralization–precipitation–bridging mechanism. Response surface methodology (RSM) study indicated that strong interaction in the coagulation/flocculation of lignin occurred between the initial pH–polyDADMAC dosage, initial pH–calcium lactate dosage and polyDADMAC–calcium lactate dosage. The highest lignin removal achieved was between 50 and 68%. The removal behavior depended on the initial lignin concentration in the solution. The results showed that lignin removal from aqueous solution is possible in a single stage mixing tank by utilizing polyDADMAC–calcium lactate as a dual coagulant. The method mentioned here will potentially be useful for the treatment of lignin containing wastewater from several industrial processes such as palm oil mill, pulp and paper, olive mill etc.

Experimental Investigation of a Cascaded Latent Heat Storage System for Diesel Engine Waste Heat Recovery

Thermal storage plays a vital role in improving the overall efficiency of a waste heat recovery system. A phase change storage system exhibits high energy storage density and isothermal behavior during the charging and discharging processes. In the present work, the cascading arrangement of the phase change storage system is studied to analyze the improvement in the efficiency of the storage system during the charging process, and to compared it with a single storage tank system. The performance parameters, such as the amount of heat recovered, the heat lost, charging rate, charging efficiency, and the percentage of energy saved, are investigated in detail.

A cost and performance comparison of packed bed and structured thermocline thermal energy storage systems

A structured concrete thermocline thermal energy storage (TES) system is proposed as an alternative to currently-used TES systems. The issues of material settlement and thermal ratcheting found in packed bed thermocline TES systems is avoided by replacing the packed aggregate bed with structured high-temperature concrete. A summary of all utility scale TES systems with integrated TES in existence today is provided and discussed. Cost reduction options such as replacing two-tank systems with single-tank systems and replacing liquid storage media with solid storage media are discussed along with limitations of both options. Numeric models are developed to simulate the performance of utility scale packed bed and structured thermocline TES systems; efficiencies of 92.37% and 84% are modeled for packed-bed and structured systems. A complete cost analysis of utility-scale, 2165MWh packed bed and structured systems is conducted; capacity costs of $30/kWh and $34/kWh are determined for packed bed and structured systems respectively. A structured concrete thermocline is deemed to be a viable TES option due to its low cost and the fact that there are no concerns of thermal ratcheting of the tank.

Kinetic behavior in criticality accident of two fuel solution tanks

This work aimed at criticality safety in fuel-fabrication or reprocessing facilities. To estimate the expected released energy in criticality accidents of several fuel-solution tanks based on the energy released in a single-fuel-solution-tank accident, the total energy released in a two-tank system was evaluated with different compositions of fuel solutions. The code used for the analysis took into account the neutronic coupling between the tanks. The results made clear that as the fuel enrichment increases, neutronic coupling becomes stronger. The calculated increase of the total energy released in a criticality accident of a system with two fuel-solution tanks compared to that of a system with just one was roughly the same regardless of different feedback model used for the analysis. The results show that the difference in energy release between multiple-tank and single-tank systems of similar composition may be evaluated using the developed transient analysis code.

Level control of single water tank systems using Fuzzy-PID technique

In this study, for the control of a single water tank system, a fuzzy-PID controller design technique based on a fuzzy model is investigated. For this purpose, a water tank system is linearized as a number of submodels depending on the operating point, and a fuzzy model is obtained by fuzzy combining. Each submodel is approximated as a first order time delay model, and a PID controller is designed using several existing tuning techniques. Then, through the fuzzy combination of this controller using the same method as that of the fuzzy model, a fuzzy-PID controller is designed. For the proposed technique, a simulation is performed using the fuzzy model of a water tank system, and the validity is examined by comparing its performance with that of a PID controller.

Spatial and temporal modeling of sub- and supercritical thermal energy storage

This paper describes a thermodynamic model that simulates the discharge cycle of a single-tank thermal energy storage (TES) system that can operate from the two-phase (liquid–vapor) to supercritical regimes for storage fluid temperatures typical of concentrating solar power plants. State-of-the-art TES design utilizes a two-tank system with molten nitrate salts; one major problem is the high capital cost of the salts (International Renewable Energy Agency, 2012). The alternate approach explored here opens up the use of low-cost fluids by considering operation at higher pressures associated with the two-phase and supercritical regimes.The main challenge to such a system is its high pressures and temperatures which necessitate a relatively high-cost containment vessel that represents a large fraction of the system capital cost. To mitigate this cost, the proposed design utilizes a single-tank TES system, effectively halving the required wall material. A single-tank approach also significantly reduces the complexity of the system in comparison to the two-tank systems, which require expensive pumps and external heat exchangers.A thermodynamic model is used to evaluate system performance; in particular it predicts the volume of tank wall material needed to encapsulate the storage fluid. The transient temperature of the tank is observed to remain hottest at the storage tank exit, which is beneficial to system operation. It is also shown that there is an optimum storage fluid loading that generates a given turbine energy output while minimizing the required tank wall material.Overall, this study explores opportunities to further improve current solar thermal technologies. The proposed single-tank system shows promise for decreasing the cost of thermal energy storage.

An Innovative Concept of a Thermal Energy Storage System Based on a Single Tank Configuration Using Stratifying Molten Salts as both Heat Storage Medium and Heat Transfer Fluid, and with an Integrated Steam Generator

The proposed innovative thermal energy storage system is based on a single tank containing a mixture of nitrate salts (60% NaNO3 and 40% KNO3 in weight; this mixture gradually changes from solid to liquid in the temperature range between about 220°C and 240°C, becoming completely melted above this temperature), with an integrated steam generator directly contained inside it. The system is operated exploiting the thermal stratification of the salts mixture in the temperature range between 550°C (hot temperature) and 290°C (cold temperature). The experimental work conducted at ENEA has revealed that the thermal stratification of the molten salts mixture can be maintained quite constant for several hours and the presence of the integrated steam generator actively guarantees and maintains the stratification during the operation time, avoiding mixing of the stratified layers. The single-tank system with stratification of the molten salts and an integrated steam generator is an important improvement in terms of efficiency, reliability and cost reduction, with respect to the two-tank thermal energy storage system. This report has the aim of giving an overview of this new technology but, given the fact that the experimental activities are still ongoing, the description of the system remains at a qualitative level. The complete set of experimental results will be presented in the future when the Projects that are framework of this research will have been completed.

Thermal behaviour of a modular storage system when subjected to variable charge and discharge sequences

This paper presents the results of an experimental study conducted on a multi-tank thermal storage. The purpose of the study was to investigate the thermal behaviour of the stratified tank system when subjected to standard draw profiles. The experimental setup consisted of a charge loop to simulate a solar collector input, three commercially available 270L domestic hot water tanks and three side-arm, natural convection heat exchangers. The system was charged using two 3kW electric heaters which produced a variable input power to simulate the variation in output of a typical fixed orientation solar collector. Realistic hot water draws were conducted according to the specifications of the Canadian Standard Association, CSA-F379.1, for Solar Domestic Hot Water Systems. Experimental tests were conducted over 2days for three different plumbing configurations, and compared with simulation results produced in the TRNSYS simulation environment. The plumbing configurations which were considered include: series charge and series discharge, parallel charge and parallel discharge, and series charge and parallel discharge. Comparisons between system configurations were based on stratification levels, hot water delivery temperatures, and solar fractions. Results of the study showed that charging and discharging the system in parallel produced the highest solar fraction when compared to the other multi-tank configurations, with solar fractions of 0.62 and 0.67 from experimental testing and TRNSYS simulation, respectively. When compared to a single tank configuration, the parallel charge and parallel discharge configuration achieved 97.7% of the delivered solar energy of a stratified single tank system with the same storage volume and heat exchanger performance.

A study on the thermodynamic analysis of a cascaded latent heat storage system over the single storage tank system for diesel engine waste heat recovery

This article presents the comparison of performance of a cascaded Latent Heat Storage (LHS) system over the Single Storage Tank (SST) system for heat recovery from a diesel engine. The energy and exergy saved and efficiencies during the charging process are evaluated and reported using actual system data. The discharge process is analysed with a case study and it is concluded that it is possible to improve both the energy and exergy efficiencies appreciably using the cascaded LHS system. The exergy analysis, combined with the environmental perspective, is the useful solution methodology for many of the energy and environmental problems.

Performance comparison between a two-reactor cascade and a single tank in an activated sludge wastewater treatment process

We Investigate a model for the treatment of wastewater in the activated sludge process. The process is based on the aeration of wastewater with flocculating biological growth, followed by the separation of treated wastewater from biological growth. Part of this growth is wasted, and the remainder returned to the system. The biochemical model consists of two types of bacteria, sludge bacteria and sewage bacteria, and two types of ciliated protozoa, free-swimming ciliates and ciliates attached to sludge floes. A combination of steady-state analysis, path following techniques and numerical integration of the governing equations are used to study the dynamics of this system in a network of two coupled reactors arranged in a series. We compare the treatment efficiency for a single tank system with that of a two-reactor cascade. In the latter scenario the total residence time is fixed and the residence time in the first reactor is taken to be a design parameter. Process parameters that ensure optimal performance are discussed.

Effects of white shrimp, Litopenaeus vannamei (Boone), and Nile tilapia, Oreochromis niloticus L., stocking density on growth, nutrient conversion rate and economic return in integrated closed recirculation system

Integrated closed recirculation systems in intensive shrimp culture is one strategy that minimizes waste from culture systems and the risk of disease and provides an additional income source as well. This study investigated the effect of tilapia–shrimp stocking density ratio on the growth, nutrient conversion rate and economic return in the integrated closed recirculation culture system of white shrimp ( Litopenaeus vannamei) and Nile tilapia ( Oreochromis niloticus). The experiment was conducted using outdoor tank system with 6 treatment conditions: T1, single shrimp tank system; T2, closed recirculation system without tilapia; T3 to T6, integrated closed recirculation system with the tilapia–shrimp stocking density ratio of 0.01, 0.025, 0.05 and 0.075, respectively. The shrimp were stocked at a density of 40 individual m − 2 for all treatments. Shrimp were fed with commercial pellets, while tilapia was not fed with the feed pellet. The culture period was 8 weeks for shrimp and 7 weeks for tilapia. The shrimp growth rate and net income of the system of T2 was significantly higher than T5 and T6 ( P < 0.05) but was no different from T1, T3 and T4. The tilapia growth rate in T3 was significantly higher than the others ( P < 0.05). The nitrogen conversion rate into total (shrimp + tilapia) biomass of T2 to T5 was significantly higher than T1 ( P < 0.05). T6 showed a lower N conversion rate than the lower tilapia–shrimp ratio. The phosphorus conversion rate into total biomass was significantly higher in T3 to T6 than T1 and T2 ( P < 0.05). These results indicate that tilapia stocking significantly improved P conversion rate but the N conversion and shrimp growth rates decreased with high tilapia stocking. Considering all parameters, the integrated system with a low tilapia–shrimp ratio (the ratio of 0.01 and 0.025) were effective to improve the nutrient conversion rate to culture animals without lowering shrimp growth.

Single- and multi-tank energy storage for solar heating systems: fundamentals

A multi-tank liquid-water system for storing low-temperature solar-derived heat is investigated experimentally and analytically. The motivation is a perceived economic advantage of the proposed system over single-tank systems in solar heating systems where the required total volume of water is rather large — say 2000 l or more. In the proposed system, the individual tanks in the multi-tank system (each with a volume of about 200 l) are interconnected by means of two strings of immersed-coil heat exchangers: the first string serially connects exchangers that have been immersed at the bottoms of the tanks, the second connects exchangers that have been immersed at the tops of the tanks. The first string will be connected to the solar collector loop and the second in the load loop. The present work experimentally demonstrates the degree of effective stratification that the multi-tank system can achieve, as well as a thermodynamically advantageous ‘thermal diode’ effect. It also describes a model for a multi-tank system as well as experiments that validate the model. Part of the multi-tank model is a model for a single tank with immersed coil heat exchanger, and this model drew upon a ‘reversion-elimination’ algorithm from the recent literature. The validity of the reversion-elimination algorithm is supported by the present experiments.

PID TUNING FOR A MULTIVARIABLE PLANT USING TAGUCHI-BASED METHODS

This paper presents the use of Taguchi methods for tuning PID parameters in a multivariable plant. The process used is a single-tank system with two inflows. The level in the main tank and one of the input flows are the controlled variables. The variation of eight parameters was analysed and tests were performed with a L18 orthogonal array. After five stages of experimentation, a 65% improvement in signal-to-noise ratio was achieved.