scholarly journals Fuzzy reliability-based optimization of a hydropower reservoir

2019 ◽  
Vol 21 (2) ◽  
pp. 308-317 ◽  
Author(s):  
Sukanya J. Nair ◽  
K. Sasikumar
Keyword(s):  
Performance Optimization ◽  
Optimal Operation ◽  
Operating Policy ◽  
Multi Stage ◽  
Decision Making Problem ◽  
Fuzzy Event ◽  
Hydropower Production ◽  
Reliability Based Optimization ◽  
Optimal Operating Policies ◽  
Hydropower Reservoir

Abstract Reservoir operation modeling and optimization are inevitable components of water resources planning and management. Determination of reservoir operating policy is a multi-stage decision-making problem characterized by uncertainty. Uncertainty in inflows and power demands lead to varying degrees of the working of a reservoir from one period to another. This transition, being ambiguous in nature, can be addressed in a fuzzy framework. The different working states of the reservoir are described as fuzzy states. Based on the degree of success in meeting the power demand and randomness associated with inflows, hydropower production is considered as a random fuzzy event. This paper examines the scope of profust reliability theory, a theory used in the reliability analysis of manufactured systems, in the performance optimization of a hydropower reservoir system. The operating policy derived from a profust reliability-based optimization model is compared with a simulation model. The model is then used to derive the optimal operation policy for a hypothetical reservoir fed by normally distributed inflow, for a period of five years. The results show that the model is useful in deriving optimal operating policies with improved reliabilities in hydropower production.

Investigation Into Optimal Operation of BCHP Systems in the Air-Conditioning Season

2006 ◽  
Author(s):  
Jiacong Cao ◽  
Hong Fang
Keyword(s):  
Power Generation ◽  
Energy Conservation ◽  
Performance Optimization ◽  
Optimization Problems ◽  
Economic Effect ◽  
Numerical Data ◽  
Computer Time ◽  
Optimal Operation ◽  
Exergetic Efficiency ◽  
Lower Efficiency

Building cooling, heating and power generation (BCHP) is important for the sustainable energy strategy in China because of its contribution to energy conservation and the reduction of CO2 emissions. The number of BCHP or small-scaled combined cooling, heating and power generation systems that have been put to use or are in the course of construction is steadily increasing in China. However, in many cases the performance of BCHP systems is not good enough, i.e., the average real exergetic efficiency of whole system is much lower than expected and the economic effect is not satisfactory. This is a problem that perplexes designers and plant owners and need be investigated so as to increase the knowledge of optimizing the operation of BCHP systems. In this paper the performance of a typical BCHP system is investigated using thermodynamic and thermoeconomic analyses based on the simulating results of off-design operation and the solution of performance optimization of the system. With the help of a great number of real running data of the system and the master data supplied by manufacturers, a model of the system operation is developed to simulate the whole domain of operation on off-design conditions. In order to shorten computer time the operation domain is described by a set of functions obtained by curve fitting using the numerical data from the simulation. Two models of optimization, of which the objective functions are the exergetic efficiency and gross benefit of the whole BCHP system separately, are established in virtue of these fitted functions. The simulation of off-design operation and the solution of the optimization problems supply a great number of useful data that form various graphs, which are to be the references to energy conservation and economic operation of the systems. The investigation indicates that there are some differences between the optimum working conditions obtained by the two optimization models, whereas it is inevitable that the system runs with some lower efficiency and less gross benefit when working at high cooling or heating load factors. By analyzing the data some significant conclusions are obtained, which will be helpful for the BCHP industry in China.

Performance optimization of solar multi-stage flash desalination process using Pinch technology

Desalination ◽  
2008 ◽  
Vol 220 (1-3) ◽  
pp. 524-530 ◽  
Author(s):  
Hou Shaobo ◽  
Zhongjin Zhang ◽  
Zhongzhou Huang ◽  
Aixia Xie
Keyword(s):  
Performance Optimization ◽  
Multi Stage ◽  
Pinch Technology

An approach to hesitant fuzzy multi-stage multi-criterion decision making

Kybernetes ◽  
2014 ◽  
Vol 43 (9/10) ◽  
pp. 1447-1468 ◽  
Author(s):  
Huchang Liao ◽  
Zeshui Xu ◽  
Jiuping Xu
Keyword(s):  
Decision Making ◽  
Fuzzy Variable ◽  
Entropy Method ◽  
Aggregation Operators ◽  
Average Deviation ◽  
Content Type ◽  
Preference Information ◽  
Multi Stage ◽  
Fuzzy Aggregation ◽  
Decision Making Problem

Purpose – The purpose of this paper is to develop some weight determining methods for hesitant fuzzy multi-criterion decision making (MCDM) in which the preference information on attributes is collected over different periods. Design/methodology/approach – Based on the proposed weight determining methods and dynamic hesitant fuzzy aggregation operators, an approach is developed to solve the hesitant fuzzy multi-stage multi-attribute decision-making problem where all the preference information of attributes over different periods is represented in hesitant fuzzy values. Findings – In order to determine the weights associated with dynamic hesitant fuzzy operators, the authors propose the improved maximum entropy method and the minimum average deviation method. Research limitations/implications – This paper does not consider the multi-stage multi-criteria group decision-making problem. Practical implications – An example concerning the evaluation of rangelands is given to illustrate the validation and efficiency of the proposed approach. It should be stated that the proposed approach can also be implemented into other multi-stage MCDM problems. Originality/value – The concept of hesitant fuzzy variable (HFV) is defined. Some operational laws and properties of the HFVs are given. Moreover, to fuse the multi-stage hesitant fuzzy information, the aggregation operators of hesitant fuzzy sets are extended to that of the HFVs.

System-Level Transient Thermal Analysis for Performance Optimization of High Power Microelectronics

2003 ◽  
Author(s):  
Victor Adrian Chiriac ◽  
Tien-Yu Tom Lee ◽  
H. S. Chen
Keyword(s):  
Thermal Performance ◽  
Performance Optimization ◽  
Numerical Study ◽  
Optimal Operation ◽  
System Level ◽  
Main Concern ◽  
Efficient Operation ◽  
Normal Test ◽  
Transient Thermal ◽  
Short Time

The increasing trend in power levels and densities leads to the need of design thermal optimization, at either module or system level. A numerical study using finite-volume software was conducted to model the transient thermal behavior of a system including a package dissipating large amounts of power over short time durations. The system is evaluated by choosing the appropriate heat sink for the efficient operation of the device under 100W of constant powering, also to enhance the thermal performance of the enclosure/box containing the test stack-up. The intent of the study is to provide a meaningful understanding and prediction of the high transient powering scenarios. The study focuses on several powering and system design scenarios, identifying the main issues encountered during a normal device operation. The power source dissipates 100W for 2 seconds then is cooled for another 2 seconds. This thermal cycle is likely to occur several times during a normal test-up, and it is the main concern of the manufacturers not to exceed a limit temperature during the device testing operation. The transient trend is further extrapolated analytically to extract the steady state peak temperature values, in order to maintain the device peak temperatures below 120°C. The benefit of the study is related to the possibility to extract the maximum/minimum temperatures for a real test involving a large number of heating-cooling cycles, yet maintaining the initial and peak temperatures within a certain range, for the optimal operation of the device. The flow and heat transfer fields are thoroughly investigated. By using a combination of numerical and analytical study, the thermal performance of the device undergoing infinity of periodic thermal cycles is further predicted.

scholarly journals Optimal Operation of a Microgrid with Hydrogen Storage Based on Deep Reinforcement Learning

Electronics ◽  
2022 ◽  
Vol 11 (2) ◽  
pp. 196
Author(s):  
Zhenshan Zhu ◽  
Zhimin Weng ◽  
Hailin Zheng
Keyword(s):  
Hydrogen Storage ◽  
Interpolation Method ◽  
Linear Interpolation ◽  
Optimal Operation ◽  
Gradient Algorithm ◽  
Sequential Decision ◽  
Generalization Capability ◽  
Characteristic Model ◽  
Decision Making Problem ◽  
Policy Gradient

Microgrid with hydrogen storage is an effective way to integrate renewable energy and reduce carbon emissions. This paper proposes an optimal operation method for a microgrid with hydrogen storage. The electrolyzer efficiency characteristic model is established based on the linear interpolation method. The optimal operation model of microgrid is incorporated with the electrolyzer efficiency characteristic model. The sequential decision-making problem of the optimal operation of microgrid is solved by a deep deterministic policy gradient algorithm. Simulation results show that the proposed method can reduce about 5% of the operation cost of the microgrid compared with traditional algorithms and has a certain generalization capability.

scholarly journals Evaluating Ecosystems Services Values due to Land use Transformation in the Gojeb Sub-basin, Southwest Ethiopia

2021 ◽  
Author(s):  
Hailu Shiferaw ◽  
Tena Alamirew ◽  
Tibebu Kassawmar ◽  
Gete Zeleke
Keyword(s):  
Land Use ◽  
Sustainable Use ◽  
Land Use Land Cover ◽  
Cultivated Land ◽  
Policy Makers ◽  
Use Of Resources ◽  
Small Holder Farmers ◽  
Hydropower Production ◽  
Land Use Transformation ◽  
Hydropower Reservoir

Abstract BackgroundLand use land cover (LULC) transformation and ecosystems service valuation (ESVs) play important roles for vegetation restoration and payment for ecosystems service (PES) programs. The objective of this work was to quantify LULC transformations and associated ESVs in the Gojeb sub-basin by analyzing LULC between 1986 and 2016 using satellite images, field observations and ancillary datasets. ResultsThe summarized LULC classes are: bareland, cropland, grassland, forest, plantation, settlement, shrub, water-body and woodland. The ESVs were evaluated for each LULC based on these LULC classes. Forests had the highest cover (> 423000ha ~60%) in 1986 but it reduced to 317000ha (~45%) in 2016. About >56000ha of forests were changed to cultivated land, and >105000ha to different classes. Cultivated land increased from >258000ha (~37%) in 2016 compared to 150000ha (~21.5%) in 1986. The sub-basin had ESVs of US$2.52 billion in 1986 but decreased to US$1.97 billion in 2016; losing about US$0.551 billion within the last 30 years (annual loss rate of US$18.4 million). Potential drivers would be agricultural expansion, land degradation/erosion, landslide and deforestation, indicating that requires concerted effort to restore and manage landscapes for sustainable socio-ecological and economic uses.ConclusionThis study is meaningful for management of natural resources in the catchment, improvement of hydropower production and lifespan of the hydropower reservoir on one hand and productivity of small holder farmers and inhabitants in the basin on the other besides to the lesson learned to other similar basins. Hence, payment for ecosystems service scheme is recommended as a win-win approach to be implemented between upper and downstream users for sustainable use of resources. This study assist policy makers in designing evidence-based solutions for PES programs in the study area and elsewhere.

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