Robust Optimal Operation of a Gas Turbine Cogeneration Plant Under Uncertain Energy Demands

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Ryohei Yokoyama ◽  
Masashi Ohkura ◽  
Tetsuya Wakui
Keyword(s):  
Gas Turbine ◽  
Energy Supply ◽  
Numerical Study ◽  
Optimization Method ◽  
Optimal Operation ◽  
Mixed Integer ◽  
Cogeneration Plant ◽  
Co2 Emission Reduction ◽  
Operational Strategy ◽  
Energy Demands

Some optimal operation methods based on the mixed-integer linear programming (MILP) have been proposed to operate energy supply plants properly from the viewpoints of economics, energy saving, and CO2 emission reduction. However, most of the methods are effective only under certain energy demands. In operating an energy supply plant actually, it is necessary to determine the operational strategy properly based on predicted energy demands. In this case, realized energy demands may differ from the predicted ones. Therefore, it is necessary to determine the operational strategy so that it is robust against the uncertainty in energy demands. In this paper, an optimization method based on the MILP is proposed to conduct the robust optimal operation of energy supply plants under uncertain energy demands. The uncertainty in energy demands is expressed by their intervals. The operational strategy is determined to minimize the maximum regret in the operational cost under the uncertainty. In addition, a hierarchical relationship among operation modes and on/off states of equipment, energy demands, and energy flow rates of equipment is taken into account. First, a general formulation of a robust optimal operation problem is presented, which is followed by a general solution procedure. Then, in a numerical study, the proposed method is applied to a gas turbine cogeneration plant for district energy supply. Through the study, some features of the robust optimal operation are clarified, and the validity and effectiveness of the proposed method are ascertained.

Optimal Operation of a Gas Turbine Cogeneration Plant in Consideration of Equipment Minimum Up and Down Times

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
Ryohei Yokoyama
Keyword(s):  
Gas Turbine ◽  
Energy Supply ◽  
Numerical Study ◽  
Optimal Operation ◽  
Operational Planning ◽  
Mixed Integer ◽  
Cogeneration Plant ◽  
Operational Strategies ◽  
Operational Strategy ◽  
District Energy

It has become important for operators to determine operational strategies of energy supply plants appropriately corresponding to energy demands varying with season and time from the viewpoints of economics, energy saving, and reduction in CO2 emission. Especially, cogeneration plants produce heat and power simultaneously, which increases alternatives for operational strategies. This makes it more important for operators to determine operational strategies of cogeneration plants appropriately. In this paper, for the purpose of assisting operators or operating plants automatically, an optimal operational planning method based on the mixed-integer linear programming is developed to determine the operational strategy of equipment so as to minimize the operational cost, in consideration of equipment minimum up and down times for each piece of equipment to be operated with appropriate numbers of startups and shutdowns. In the numerical study, the proposed method is applied to the daily operational planning of a gas turbine cogeneration plant for district energy supply. It is clarified how the constraints for minimum up and down times affect the operational strategy and cost. Through the study, the validity and effectiveness of the proposed method is ascertained.

Optimal Operation of a Gas Turbine Cogeneration Plant in Consideration of Equipment Minimum Up and Down Times

2011 ◽  
Author(s):  
Ryohei Yokoyama
Keyword(s):  
Gas Turbine ◽  
Energy Supply ◽  
Numerical Study ◽  
Optimal Operation ◽  
Operational Planning ◽  
Mixed Integer ◽  
Cogeneration Plant ◽  
Operational Strategies ◽  
Operational Strategy ◽  
District Energy

It has become important for operators to determine operational strategies of energy supply plants appropriately corresponding to energy demands varying with season and time from the viewpoints of economics, energy saving, and recently reduction in CO2 emission. Especially, cogeneration plants produce heat and power simultaneously, which increases alternatives for operational strategies. This makes it more important for operators to determine operational strategies of cogeneration plants appropriately. In this paper, for the purpose of assisting operators or operating plants automatically, an optimal operational planning method based on the mixed-integer linear programming is developed to determine the operational strategy of equipment so as to minimize the operational cost, in consideration of equipment minimum up and down times for each piece of equipment to be operated with appropriate numbers of startups and shutdowns. In the numerical study, the proposed method is applied to the daily operational planning of a gas turbine cogeneration plant for district energy supply. It is clarified how the constraints for minimum up and down times affect the operational strategy and cost. Through the study, the validity and effectiveness of the proposed method is ascertained.

Robust Optimal Operation of a Gas Turbine Cogeneration Plant Under Uncertain Energy Demands

2014 ◽  
Author(s):  
Ryohei Yokoyama ◽  
Masashi Ohkura ◽  
Tetsuya Wakui
Keyword(s):  
Linear Programming ◽  
Gas Turbine ◽  
Integer Linear Programming ◽  
Mixed Integer Linear Programming ◽  
Energy Supply ◽  
Optimal Operation ◽  
Mixed Integer ◽  
Cogeneration Plant ◽  
Operational Strategy ◽  
Energy Demands

Some optimal operation methods based on the mixed-integer linear programming have been proposed to operate energy supply plants properly from the viewpoints of economics, energy saving, and CO2 emission reduction. However, most of the methods are effective only under certain energy demands. In operating an energy supply plant actually, it is necessary to determine the operational strategy properly based on predicted energy demands. In this case, realized energy demands may differ from the predicted ones. Therefore, it is necessary to determine the operational strategy so that it is robust against the uncertainty in energy demands. In this paper, an optimization method based on the mixed-integer linear programming is proposed to conduct the robust optimal operation of energy supply plants under uncertain energy demands. The uncertainty in energy demands is expressed by their intervals. The operational strategy is determined to minimize the maximum regret in the operational cost under the uncertainty. In addition, a hierarchical relationships among operation modes and on/off states of equipment, energy demands, and energy flow rates of equipment are taken into account. First, a general formulation of a robust optimal operation problem is presented, which is followed by a general solution procedure. Then, in a numerical study, the proposed method is applied to a gas turbine cogeneration plant for district energy supply. Through the study, some features of the robust optimal operation are clarified, and the validity and effectiveness of the proposed method are ascertained.

scholarly journals Optimal Operation of a Gas Turbine Cogeneration Plant in Consideration of Equipment Startup/Shutdown Cost

1997 ◽  
Author(s):  
Ryohei Yokoyama ◽  
Koichi Ito
Keyword(s):  
Gas Turbine ◽  
Energy Supply ◽  
Large Scale ◽  
Numerical Study ◽  
Optimal Operation ◽  
Operational Planning ◽  
Mixed Integer ◽  
Planning Problem ◽  
Cogeneration Plant ◽  
Operational Strategy

A rational method of determining the operational strategy of energy supply plants in consideration of equipment startup/shutdown cost is proposed. The operational planning problem is formulated as a large-scale mixed-integer linear programming one, in which on/off status and energy flow rates of equipment are determined so as to minimize the sum of energy supply and startup/shutdown costs over the period considered. By utilizing a special structure of the problem, an algorithm of solving the problem efficiently is proposed. Through a numerical study on the daily operational planning of a gas turbine cogeneration plant for district heating and cooling, the effectiveness of the proposed algorithm is ascertained in terms of computation time, and the influence of equipment startup/shutdown cost on the operational strategy and cost is clarified.

Optimal Operation of a Gogeneration Plant in Consideration of Equipment Startup/Shutdown Cost

1999 ◽  
Vol 121 (4) ◽  
pp. 254-261 ◽  
Author(s):  
R. Yokoyama ◽  
K. Ito
Keyword(s):  
Energy Supply ◽  
Large Scale ◽  
Numerical Study ◽  
District Heating ◽  
Computation Time ◽  
Optimal Operation ◽  
Operational Planning ◽  
Mixed Integer ◽  
Planning Problem ◽  
Operational Strategy

A rational method of determining the operational strategy of energy supply plants in consideration of equipment startup/shutdown cost is proposed. The operational planning problem is formulated as a large-scale mixed-integer linear programming one, in which on/off status and energy flow rates of equipment are determined so as to minimize the sum of energy supply and startup/shutdown costs over the period considered. By utilizing a special structure of the problem, an algorithm of solving the problem efficiently is proposed. Through a numerical study on the daily operational planning of a gas turbine cogeneration plant for district heating and cooling, the effectiveness of the proposed algorithm, is ascertained in terms of computation time, and the influence of equipment startup/shutdown cost on the operational strategy and cost is clarified.

Optimal Design of a Gas Turbine Cogeneration Plant by a Hierarchical Optimization Method With Parallel Computing

2018 ◽  
Author(s):  
Ryohei Yokoyama ◽  
Yuji Shinano ◽  
Yuki Wakayama ◽  
Tetsuya Wakui
Keyword(s):  
Optimal Design ◽  
Energy Supply ◽  
Optimization Method ◽  
Optimal Operation ◽  
Hierarchical Optimization ◽  
Cogeneration Plant ◽  
Design Problems ◽  
Computation Efficiency ◽  
Supply Systems ◽  
Energy Supply Systems

To attain the highest performance of energy supply systems, it is necessary to rationally determine types, capacities, and numbers of equipment in consideration of their operational strategies corresponding to seasonal and hourly variations in energy demands. Mixed-integer linear programming (MILP) approaches have been applied widely to such optimal design problems. The authors have proposed a MILP method utilizing the hierarchical relationship between design and operation variables to solve the optimal design problems of energy supply systems efficiently. In addition, some strategies to enhance the computation efficiency have been adopted: bounding procedures at both the levels and ordering of the optimal operation problems at the lower level. In this paper, as an additional strategy to enhance the computation efficiency, parallel computing is adopted to solve multiple optimal operation problems in parallel at the lower level. In addition, the effectiveness of each and combinations of the strategies adopted previously and newly is investigated. This hierarchical optimization method is applied to an optimal design of a gas turbine cogeneration plant, and its validity and effectiveness are clarified through some case studies.

Effect of Steam Injected Gas Turbines on the Unit Sizing of a Cogeneration Plant

1994 ◽  
Author(s):  
Koichi Ito ◽  
Ryohei Yokoyama ◽  
Yoshikazu Matsumoto
Keyword(s):  
Energy Saving ◽  
Thermal Energy ◽  
Gas Turbines ◽  
Numerical Study ◽  
Optimization Method ◽  
Operational Planning ◽  
Simple Cycle ◽  
Cogeneration Plant ◽  
Operational Strategies ◽  
Energy Demands

The effect of installing steam injected gas turbines in a cogeneration plant is analyzed in the aspects of unit sizing and operational planning. An optimization method is used to determine the capacities of gas turbines and other auxiliary machinery in consideration of their operational strategies for variations of electricity and thermal energy demands. Through a numerical study on a plant for district hearing and cooling, it is clarified how the installation of steam injected gas turbines in place of simple cycle ones can improve the economic and energy saving properties. The influence of capital cost of steam injected gas turbines on the unit sizing and the above properties is also clarified.

Sizing of a Gas Turbine for Repowering of Cogeneration Power Plant Ljubljana by Mathematical Optimisation

1996 ◽  
Author(s):  
Mihael Gabriel Tomšič ◽  
Olgica Perović
Keyword(s):  
Power Plant ◽  
Gas Turbine ◽  
Optimal Operation ◽  
Hot Water ◽  
Mixed Integer ◽  
Heat Recovery Boiler ◽  
Continuous Variables ◽  
District Heating System ◽  
Operational Strategy ◽  
Steam Extraction

The paper deals with optimal sizing of a gas turbine for repowering of cogeneration power plant Ljubljana considering possible plant operational strategy with respect to variations of electric and heat loads and energy costs. CHP plant is a main source for the Ljubljana town district heating system. Existing plant consists of two condensing steam turbines with steam extraction, back pressure turbine with steam extraction, auxiliary steam and hot water boilers for peak heat load production. This system delivers up to 111 MW into the power grid and up to 348 MW of heat. Repowering with gas turbine generator set with additionally fired heat recovery boiler is considered. For uncoupling heat and power generation a heat storage tank is assumed. For sizing of new equipment and plant operational strategy a model based on mixed-integer linear programming was developed. Zero - one integer variables are adopted to indicate the on/off status of operation, continuous variables to indicate the operational level of each constituent equipment and an optimal solution is derived by branch and bound method. Two prospective sizes of TG sets were tested for range of assumptions regarding power purchase tariff schedules. Different optimal operation policies resulted. The study provides background for contract negotiation and for investment decisions.

Evaluation of Performance Robustness of a Gas Turbine Cogeneration Plant Based on a Mixed-Integer Linear Model

2016 ◽  
Author(s):  
Ryohei Yokoyama ◽  
Ryo Nakamura ◽  
Tetsuya Wakui ◽  
Yuji Shinano
Keyword(s):  
Linear Model ◽  
Energy Supply ◽  
Mixed Integer ◽  
Design Stage ◽  
Cogeneration Plant ◽  
Energy Demands ◽  
Integer Linear Model ◽  
Supply Systems ◽  
Energy Supply Systems ◽  
Performance Robustness

In designing energy supply systems, designers are requested to rationally determine equipment types, capacities, and numbers in consideration of equipment operational strategies corresponding to seasonal and hourly variations in energy demands. However, energy demands have some uncertainty at the design stage, and the energy demands which become certain at the operation stage may differ from those estimated at the design stage. Therefore, designers should consider that energy demands have some uncertainty, evaluate the performance robustness against the uncertainty, and design the systems to heighten the robustness. Especially, this issue is important for cogeneration plants, because their performances depend significantly on both heat and power demands. Although robust optimal design methods of energy supply systems under uncertain energy demands were developed, all of them are based on linear models for energy supply systems. However, it is still a hard challenge to develop a robust optimal design method even based on a mixed-integer linear model. At the first step for this challenge, in this paper, a method of evaluating the performance robustness of energy supply systems under uncertain energy demands is proposed based on a mixed-integer linear model. This problem is formulated as a bilevel mixed-integer linear programming one, and a sequential solution method is applied to solve it approximately by discretizing uncertain energy demands within their intervals. In addition, a hierarchical optimization method in consideration of the hierarchical relationship between design and operation variables is applied to solve large scale problems efficiently. Through a case study on a gas turbine cogeneration plant for district energy supply, the validity and effectiveness of the proposed method and features of the performance robustness of the plant are clarified.

Multiobjective Robust Optimal Design of a Gas Turbine Cogeneration Plant Under Uncertain Energy Demands

2001 ◽  
Author(s):  
Ryohei Yokoyama ◽  
Koichi Ito
Keyword(s):  
Optimal Design ◽  
Energy Saving ◽  
Gas Turbine ◽  
Energy Supply ◽  
Design Method ◽  
Primary Energy ◽  
Weighted Sum ◽  
Cogeneration Plant ◽  
Energy Demands ◽  
Robust Optimal Design

A multiobjective robust optimal design method based on the minimax regret criterion is proposed for sizing equipment of energy supply plants so that they are robust in economic and energy saving characteristics under uncertain energy demands. Equipment capacities and utility contract demands as well as energy flow rates are determined to minimize a weighted sum of the maximum regrets in the annual total cost and primary energy consumption, and satisfy all the possible energy demands. This optimization problem is formulated as a kind of multilevel linear programming one, and its solution is derived by repeatedly evaluating lower and upper bounds for the optimal value of the weighted sum of the maximum regrets. Through a case study on a gas turbine cogeneration plant for district energy supply, the trade-off relationship between the robustness in economic and energy saving characteristics is clarified.

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