Development and Application of a Dynamic Decomposition Strategy for the Optimal Synthesis/Design and Operational/Control of a SOFC Based APU Under Transient Conditions

2005 ◽  
Author(s):  
Diego Rancruel ◽  
Michael von Spakovsky
Keyword(s):  
Life Cycle ◽  
System Level ◽  
System Response ◽  
Optimization Approach ◽  
Total System ◽  
Operational Control ◽  
Dynamic Synthesis ◽  
Control Optimization ◽  
Synthesis Design ◽  
Total Life

A typical approach to the synthesis/design optimization of energy systems is to only use steady state operation and high efficiency (or low total life cycle cost) at full load as the basis for the synthesis/design. Transient operation is left as a secondary task to be solved by system and control engineers once the synthesis/design is fixed. However, transient regimes may happen quite often and the system response to them is a critical factor in determining the system feasibility. Therefore, it is important to consider the system dynamics in the creative process of developing the system. A dynamic optimization approach developed by the authors and called Dynamic Iterative Local-Global Optimization (DILGO) is applied to the dynamic synthesis/design and operational/control optimization of a solid oxide fuel cell based auxiliary power unit. The approach is based on a decomposed optimization of individual units (components and sub-systems), which simultaneously takes into account the interactions between all the units which make up the overall system. The approach was developed to support and enhance current engineering synthesis/design practices, producing improvements in the initial synthesis/design state of the system and its components at all stages of the process and allowing for any degree of detail (from the simple to the complex) at the unit (component or sub-system) level. The total system is decomposed into three sub-systems: stack sub-system (SS), fuel processing sub-system (FPS), and the work and air recovery sub-system (WRAS). Mixed discrete, continuous, and dynamic operational decision variables are considered. Detailed thermodynamic, kinetic, geometric, physical, and cost models are developed for the dynamic system using advanced state-of-the-art tools. DILGO is then applied to the dynamic synthesis/design and operational/control optimization of the system using total life cycle costs as the objective function. Results for this system and component optimization are presented and discussed.

Modeling the System and Component Performance Interactions of a SOFC Based APU for Changes in Application Load: Transient Response and Control Strategy

2004 ◽  
Author(s):  
D. F. Rancruel ◽  
M. R. von Spakovsky
Keyword(s):  
Transient Response ◽  
Control Strategy ◽  
Control Strategies ◽  
Control Variable ◽  
System Level ◽  
System Component ◽  
System Response ◽  
Optimal Control Strategy ◽  
Synthesis Design ◽  
And Control

Solid-Oxide-Fuel-Cell (SOFC) stacks respond in seconds to changes in load while the balance of plant subsystem (BOPS) responds in times several orders of magnitude higher. This dichotomy diminishes the reliability and performance of SOFC electrodes with changes in load. In the same manner current and voltage ripples which result from particular power electronic subsystem (PES) topologies and operation produce a negative effect on the SOFC stack subsystem (SS) performance. The difference in transient response among the sub-systems must be approached in a way which makes operation of the entire system not only feasible but ensures that efficiency and power density, fuel utilization, fuel conversion, and system response are optimal at all load conditions. Thus, a need exists for the development of transient component- and system-level models of SOFC based auxiliary power units (APUs), i.e. coupled BOPS, SS, and PES, and the development of methodologies for optimizing subsystem responses and for investigating system-interaction issues. In fact the transient process occurring in a SOFC based APU should be systematically treated during the entire creative process of synthesis, design, and operational control, leading in its most general sense to a dynamic optimization problem. This entails finding an optimal system/component synthesis/design, taking into account on- and off-design operation, which in turn entails finding an optimal control strategy and control profile for each sub-system/component and control variable. Such an optimization minimizes an appropriate objective function while satisfying all system constraints. A preliminary set of chemical, thermal, electrochemical, electrical, and mechanical models based on first principles and validated with experimental data have been developed and implemented using a number of different platforms. These models have been integrated in order to be able to perform component, subsystem, and system analyses as well as develop optimal syntheses/designs and control strategies for transportation and stationary SOFC based APUs. Some pertinent results of these efforts are presented here.

Investigation of Control Strategy Development Using an Integrated Model of a SOFC Based APU Under Transient Conditions

2004 ◽  
Author(s):  
Diego Rancruel ◽  
Michael von Spakovsky
Keyword(s):  
Fuel Cell ◽  
Fuel Consumption ◽  
Thermal Stresses ◽  
High Efficiency ◽  
Research Work ◽  
System Level ◽  
System Response ◽  
Sufficient Information ◽  
Synthesis Design ◽  
Start Up

A typical approach to the synthesis/design optimization of energy systems is to only use steady state operation and high efficiency (or low total life cycle cost) at full load as the basis for the synthesis/design. Transient operation as reflected by changes in power demand, shut-down, and start-up are left as secondary tasks to be solved by system and control engineers once the synthesis/design is fixed. However, start-up and shut-down may be events that happen quite often and, thus, may be quite important in the creative process of developing the system. This is especially true for small power units used in transportation applications or for domestic energy supplies, where the load demand changes frequently and peaks in load of short duration are common. The duration of start-up is, of course, a major factor which must be considered since rapid system response is an important factor in determining the feasibility of solid oxide fuel cell (SOFC) based auxiliary power units (APUs). Start-up and shut-down may also significantly affect the life span of the system due to thermal stresses on all system components. Therefore, a proper balance must be struck between a fast response and the costs of owning and operating the system so that start-up or any other transient process can be accomplished in as short a time as possible yet with a minimum in fuel consumption. In this research work we have been studying the effects of control laws and strategies and transients on system performance. The results presented in this paper are based on a set of transient models developed and implemented for the components of a 5 kW net power SOFC based APU and for the high-fidelity system which results from their integration. The simulation results given below are for two different start-up approaches: one with steam recirculation and component preheating and the second without either. These start-up simulations were performed for fixed values of a number of system-level parameters (e.g., fuel utilization, steam to methane ratio, etc.) and were used to generate sufficient information to permit the development of appropriate control strategies for this critical operating point. These strategies are based on a balance between fuel consumption and response time. In addition, energy buffering hardware was added to the system configuration in order to minimize the effect of transients on fuel cell stack performance and lifetime.

A Decomposition Strategy Applied to the Optimal Synthesis/Design and Operation of an Advanced Fighter Aircraft System: A Comparison With and Without Airframe Degrees of Freedom

2003 ◽  
Author(s):  
Diego F. Rancruel ◽  
Michael R. von Spakovsky
Keyword(s):  
Optimization Problems ◽  
Environmental Control ◽  
System Level ◽  
Significant Advance ◽  
Total System ◽  
Energy Integration ◽  
Fighter Aircraft ◽  
System A ◽  
Synthesis Design ◽  
Operational Optimization

A decomposition methodology based on the concept of “thermoeconomic isolation” applied to the synthesis/design and operational optimization of an advanced tactical fighter aircraft is the focus of this research. Conceptual, time, and physical decomposition were used to solve the system-level as well as unit-level optimization problems. The total system was decomposed into five sub-systems as follows: propulsion sub-system (PS), environmental control sub-system (ECS), fuel loop sub-system (FLS), vapor compression and PAO loops sub-system (VC/PAOS), and airframe sub-system (AFS) of which the AFS is a non-energy based sub-system. A number of different configurations for each sub-system were considered. The most promising set of candidate configurations, based on both an energy integration analysis and aerodynamic performance, were developed and detailed thermodynamic, geometric, physical, and aerodynamic models at both design and off-design were formulated and implemented. A decomposition strategy called Iterative Local-Global Optimization (ILGO) developed by Mun˜oz and von Spakovsky (2000b,c) was then applied to the synthesis/design and operational optimization of the advanced tactical fighter aircraft. This decomposition strategy is the first to successfully closely approach the theoretical condition of “thermoeconomic isolation” when applied to highly complex, highly dynamic non-liner systems. This contrasts with past attempts to approach this condition, all of which were applied to very simple systems under very special and restricted conditions such as those requiring linearity in the models and strictly local decision variables. This is a significant advance in decomposition and has now been successfully applied to a number of highly complex and dynamic transportation and stationary systems. This paper presents the detailed results from one such application, which additionally considers a non-energy based sub-system (AFS).

scholarly journals Life Cycle GHG Emissions of Residential Buildings in Humid Subtropical and Tropical Climates: Systematic Review and Analysis

Buildings ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 6
Author(s):  
Daniel Satola ◽  
Martin Röck ◽  
Aoife Houlihan-Wiberg ◽  
Arild Gustavsen
Keyword(s):  
Systematic Review ◽  
Life Cycle ◽  
Residential Buildings ◽  
Construction Materials ◽  
Ghg Emissions ◽  
Energy Performance ◽  
Cycle Performance ◽  
Tropical Climates ◽  
Building Life Cycle ◽  
Total Life

Improving the environmental life cycle performance of buildings by focusing on the reduction of greenhouse gas (GHG) emissions along the building life cycle is considered a crucial step in achieving global climate targets. This paper provides a systematic review and analysis of 75 residential case studies in humid subtropical and tropical climates. The study investigates GHG emissions across the building life cycle, i.e., it analyses both embodied and operational GHG emissions. Furthermore, the influence of various parameters, such as building location, typology, construction materials and energy performance, as well as methodological aspects are investigated. Through comparative analysis, the study identifies promising design strategies for reducing life cycle-related GHG emissions of buildings operating in subtropical and tropical climate zones. The results show that life cycle GHG emissions in the analysed studies are mostly dominated by operational emissions and are the highest for energy-intensive multi-family buildings. Buildings following low or net-zero energy performance targets show potential reductions of 50–80% for total life cycle GHG emissions, compared to buildings with conventional energy performance. Implementation of on-site photovoltaic (PV) systems provides the highest reduction potential for both operational and total life cycle GHG emissions, with potential reductions of 92% to 100% and 48% to 66%, respectively. Strategies related to increased use of timber and other bio-based materials present the highest potential for reduction of embodied GHG emissions, with reductions of 9% to 73%.

scholarly journals Understanding Power System Behavior through Mining Archived Operational Data

2009 ◽  
Vol 10 (1) ◽  
Author(s):  
Sarasij Das ◽  
Nagendra Rao P S
Keyword(s):  
Data Mining ◽  
Power System ◽  
System Level ◽  
Data Sets ◽  
Total System ◽  
System Behavior ◽  
Average System ◽  
Recorded Data ◽  
Operational Data ◽  
Southern Regional

This paper is the outcome of an attempt in mining recorded power system operational data in order to get new insight to practical power system behavior. Data mining, in general, is essentially finding new relations between data sets by analyzing well known or recorded data. In this effort we make use of the recorded data of the Southern regional grid of India. Some interesting relations at the total system level between frequency, total MW/MVAr generation, and average system voltage have been obtained. The aim of this work is to highlight the potential of data mining for power system applications and also some of the concerns that need to be addressed to make such efforts more useful.

Harmonic Synthesis Design Methodology for Dynamic Spring Balancing

1996 ◽  
Vol 118 (4) ◽  
pp. 733-740 ◽  
Author(s):  
Eungsoo Shin ◽  
D. A. Streit
Keyword(s):  
Dynamic System ◽  
Initial Conditions ◽  
Phase 1 ◽  
System Optimization ◽  
Optimization Method ◽  
Optimization Techniques ◽  
System Response ◽  
Two Phase ◽  
Walking Machine ◽  
Synthesis Design

A new spring balancing technique, called a two-phase optimization method, is presented. Phase 1 uses harmonic synthesis to provide a system configuration which achieves an approximation to a desired dynamic system response. Phase 2 uses results of harmonic synthesis as initial conditions for dynamic system optimization. Optimization techniques compensate for nonlinearities in machine dynamics. Example applications to robot manipulators and to walking machine legs are presented and discussed.

Performance Analysis and Optimization of Fresnel Lens Concentrated Solar Water Heater

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Vinod Kumar Soni ◽  
R. L. Shrivastava ◽  
S. P. Untawale ◽  
Kshitij Shrivastava
Keyword(s):  
Life Cycle ◽  
Performance Analysis ◽  
Flat Plate ◽  
Mass Flow ◽  
Critical Parameters ◽  
Total System ◽  
Outlet Temperature ◽  
Solar Water Heater ◽  
Water Heater ◽  
Solar Water

Concentrated solar power (CSP) is a mature and efficient technology to cater the large-scale demand of hot water. Conventional reflectors/mirrors in CSP share 50% of total system cost. High installation as well as O&M cost is the major concern in reflector-based CSP. Apart from the above, manufacturing defects and adverse service environment cause premature degradation of reflectors and substantial drop in efficiency and service life. Performance analysis of an innovative optically concentrated solar water heater (OCSWH) using plurality of Fresnel lenses of poly methyl methacrylate (PMMA) is presented in the work. Size and yield of any solar water heater (SWH) are mainly dependent on its aperture area, output temperature, and mass flow rate, which are termed herein as critical parameters. Series of experimentations is carried out by varying critical design and operating parameters viz. aperture area, outlet temperature, and rate of mass flow, and similar experimentation is also carried out on commercially available flat plate SWH to compare its performance. Loss of heat from riser and header pipes is restricted by application of effective insulation. Substantial improvement in collector efficiency, increase in rate of mass flow, and rise in discharge temperature with reference to flat plate collector are noted. Economics is also studied covering life cycle cost (LCC), life cycle saving (LCS), and energy payback period.

scholarly journals Biology of Diadiplosis multifila (Diptera: Cecidomyiidae) in Planococcus citri under constant temperatures

2019 ◽  
Vol 10 (3) ◽  
pp. 346-352
Author(s):  
Alexandre Martins Dos Santos ◽  
José Eudes De Morais Oliveira ◽  
Andréa Nunes Moreira de Carvalho ◽  
Martin Duarte De Oliveira ◽  
Carla Patrícia Oliveira de Assis ◽  
...  
Keyword(s):  
Life Cycle ◽  
Sex Ratio ◽  
Larval Stage ◽  
Pupal Stage ◽  
Planococcus Citri ◽  
Egg Viability ◽  
Northeast Region ◽  
Embryonic Period ◽  
Semi Arid ◽  
Total Life

Diadiplosis multifila was recently discovered feeding on Planococcus citri eggs in vineyards in the semi-arid northeast region of Brazil. The objective of the present paper was to study the biology of D. multifila in P. citri under constant temperatures of 22, 25, 28, and 31 °C. We evaluated its embryonic stage, egg viability, development period, survival of larva and pupa, longevity, average number of eggs, and sex ratio. D. multifila completed its life cycle in all temperatures except for 31 °C. The length of the embryonic period ranged from 4 to 7 days. The larval stage was longer at a temperature of 22 °C (8.6 days) and shorter at 28 °C (6.4). The pupal stage exhibited durations of 12.9, 10.4, and 8.2 days for temperatures of 22, 25, and 28 °C, respectively. The average viability in the larval stage was 97% and 83% in the pupal stage. The total life cycle took 16.7 (28 °C), 20 (25 °C), and 27 (22 °C) days to complete. The adults lived for approximately 2 days and the females produced on average 34, 25, and 19 eggs at temperatures of 22, 25, and 28 °C, respectively. The sex ratio varied from 0.46 to 0.54.

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